Processing optical system, processing apparatus, and processing method

Abstract

[Problem] To provide a processing optical system, a processing device, and a processing method that can form an ideally shaped riblet structure. [Solution] A processing optical system (15) comprises: a first optical system (16) that split a processing light EL0 from a light source (2) into a first processing light EL1 and a second processing light EL2; a second optical system (17) that forms a interference fringe IS on a surface of an object (W) by dividing the second processing light EL2 into a plurality of second processing lights EL2 and irradiating the divided plurality of second processing lights EL2 onto the object (W) from different incident directions; and a third optical system (18) that irradiates the first processing light EL1 from the first optical system (16) toward an interference area IA on the surface of the object (W) where an interference fringe IS has been formed.

Description

Technical Field

[0001] The present disclosure relates to the technical fields of, for example, a processing optical system, a processing apparatus, and a processing method for processing an object.

Background Art

[0002] Patent Document 1 describes a processing apparatus capable of processing an object so that riblets are formed on the surface of the object such as an airframe of an aircraft. Such a processing apparatus is required to appropriately process the object.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] According to a first aspect, there is provided a processing optical system including: a first optical system that branches processing light from a light source into first processing light and second processing light; a second optical system that divides the second processing light into a plurality of second processing lights and irradiates the object with the plurality of divided second processing lights from different incident directions to form interference fringes on the surface of the object; and a third optical system that irradiates the first processing light from the first optical system toward an interference region on the surface of the object where the interference fringes are formed.

[0005] According to a second aspect, there is provided a processing optical system including: an interference fringe forming optical system that divides the second processing light among the first and second processing lights, which are pulsed lights whose at least a part of the emission periods overlap, into a plurality of second processing lights and irradiates the object with the plurality of divided second processing lights from different incident directions to form interference fringes on the surface of the object; and an irradiation optical system that irradiates the first processing light toward an interference region where the interference fringes are formed.

[0006] According to a third embodiment, a processing apparatus is provided for performing riblet processing on the surface of an object using light from a light source, comprising the processing optical system described above and a positional relationship changing device for changing the positional relationship between the interference fringes formed on the surface of the object by the processing optical system and the surface of the object.

[0007] According to a fourth aspect, a processing method is provided for performing riblet processing on the surface of an object using light from a light source, the method comprising: splitting processing light from the light source into a first processing light and a second processing light; dividing the second processing light into a plurality of second processing lights and irradiating the object with the divided plurality of second processing lights from different incident directions to form interference fringes on the surface of the object; and irradiating the first processing light toward an interference region on the surface of the object where the interference fringes are formed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing the overall structure of the processing system of this embodiment. [Figure 2] This is a system configuration diagram showing the system configuration of the processing system of this embodiment. [Figure 3A] This is a perspective view showing the riblet structure. [Figure 3B] This is a cross-sectional view showing the riblet structure (the cross-section obtained along the line III-III' in Figure 3A). [Figure 3C] This is a top view showing the riblet structure. [Figure 4] This is a plan view showing an example of interference fringes. [Figure 5] This is a diagram showing the configuration of the processing optical system of this embodiment. [Figure 6A] This shows the fluence distribution of the processing light (interference light) in a comparative example where interference fringes are formed by multiple second processing lights without irradiating with a first processing light, and the cross-sectional shape of the riblet structure formed by the processing light in the comparative example. [Figure 6B]This figure shows the fluence distribution of the processing light in this embodiment, in which interference fringes are formed by multiple second processing lights, and the cross-sectional shape of the riblet structure formed by the processing light in this embodiment. [Figure 7] This graph shows the relationship between light fluence and the amount of workpiece processing. [Figure 8] This shows the fluence distribution of the processing light (interference light) in a comparative example in which interference fringes are formed by at least the second processing light without irradiation with the first processing light, and the cross-sectional shape of the riblet structure formed by the processing light in that comparative example. [Figure 9] This figure shows the fluence distribution of the processing light in this embodiment, in which interference fringes are formed by multiple second processing lights, and the cross-sectional shape of the riblet structure formed by the processing light in this embodiment. [Figure 10A] This shows the ideal waveform. [Figure 10B] The image shows two waveforms (fundamental frequency waveform and double frequency waveform) obtained by performing a Fourier transform on an ideal waveform. [Figure 11] This diagram is an explanatory table summarizing the irradiation patterns in the irradiation region, interference region, and superposition region of five example processing optical systems. [Figure 12] This is an explanatory diagram showing the structure of the processing optical system in the first example. [Figure 13] This is an explanatory diagram showing the characteristics of the second processed light at the splitting surface, the characteristics of the second processed light at the reflective surface, and the characteristics of the second processed light at the passing surface in the special beam splitter of the processing optical system in the first example. [Figure 14] This is an explanatory diagram showing the structure of the processing optical system in the second example. [Figure 15] This is an explanatory diagram showing the characteristics of the second processed light at the splitting surface, the reflection surface, and the passage surface in a special beam splitter of the processing optical system in the second example. [Figure 16] This is an explanatory diagram showing the structure of the processing optical system in the third example. [Figure 17]In the special beam splitter of the processing optical system of the third example, it is an explanatory diagram showing the mode of the second processing light on the splitting surface, the mode of the second processing light on the reflection surface, and the mode of the second processing light on the passing surface. [Figure 18] It is an explanatory diagram showing the structure of the processing optical system of the fourth example. [Figure 19] In the special beam splitter of the processing optical system of the fourth example, it is an explanatory diagram showing the mode of the second processing light on the splitting surface, the mode of the second processing light on the reflection surface, and the mode of the second processing light on the passing surface. [Figure 20] It is an explanatory diagram showing the structure of the processing optical system of the fifth example. [Figure 21] In the special beam splitter of the processing optical system of the fifth example, it is an explanatory diagram showing the mode of the second processing light on the splitting surface, the mode of the second processing light on the reflection surface, and the mode of the second processing light on the passing surface. [Figure 22] It is an explanatory diagram showing the structure of the processing optical system of the modified example. [Figure 23] It is an explanatory diagram showing two interference regions and two irradiation regions formed by the second optical system of the processing optical system of the modified example on the surface of the workpiece. [Figure 24] It is an explanatory diagram showing the structure of the processing optical system as another modified example. [Figure 25] It is an explanatory diagram showing the structure of the processing optical system as yet another modified example.

Embodiments for Carrying Out the Invention

[0009] Embodiments of the machining optical system, machining apparatus, and machining method will be described below with reference to the drawings. In the following, embodiments of the machining optical system, machining apparatus, and machining method will be described using a machining system SYS capable of machining a workpiece W, which is an example of an object. However, the present invention is not limited to the embodiments described below. Furthermore, in the following description, the positional relationships of the various components constituting the machining system SYS will be described using an XYZ Cartesian coordinate system defined by mutually orthogonal X, Y, and Z axes. For the convenience of explanation, in the following description, the X-axis direction and the Y-axis direction will be assumed to be horizontal (i.e., a predetermined direction in the horizontal plane), and the Z-axis direction will be assumed to be vertical (i.e., a direction perpendicular to the horizontal plane, and essentially the up and down direction). Also, the rotational directions (in other words, inclination directions) around the X, Y, and Z axes will be referred to as the θX direction, θY direction, and θZ direction, respectively. Here, the Z-axis direction may be the direction of gravity. Also, the XY plane may be the horizontal direction. [Examples]

[0010] (1) Structure of the processing system SYS First, the structure of the machining system SYS of this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing the structure of the machining system SYS of this embodiment. Figure 2 is a system configuration diagram showing the system configuration of the machining system SYS of this embodiment.

[0011] As shown in Figures 1 and 2, the processing system SYS comprises a processing device 1, a processing light source 2, and a control device 3. The processing device 1 is mounted as an end effector on an articulated robot 102 attached to a self-propelled drive unit 101 and includes a processing head 11 that irradiates the surface of a workpiece W placed on a stage 13 with processing light EL from the processing light source 2 via a beam transmission optical system 103. The processing head 11 is controlled by the control device 3 together with the self-propelled drive unit 101, the articulated robot 102, and the processing light source 2.

[0012] Here, the beam transmission optical system 103 transmits processing light EL from the processing light source 2, which supplies processing light EL to the processing head 11. Based on a command from the control device 3 (see arrow R in Figure 1), the processing head 11 irradiates the surface of the workpiece W placed on the stage 13 with processing light EL from the beam transmission optical system 103. Based on a command from the control device 3, the articulated robot 102 changes the position and orientation of the processing head 11 relative to the surface of the workpiece W, thereby changing the position and direction in which the processing light EL irradiates the surface of the workpiece W. Based on a command from the control device 3, the self-propelled drive unit 101 changes the position and orientation of the articulated robot 102, and by extension the processing head 11 attached to the articulated robot 102, relative to the surface of the workpiece W, thereby changing the position and direction in which the processing light EL irradiates the surface of the workpiece W. Details of the structure of the processing head 11 will be described later with reference to Figures 2 to 6.

[0013] The processing apparatus 1 is capable of processing a workpiece W, which is a work object (may also be called a base material), under the control of the control device 3. The workpiece W may be, for example, a metal, an alloy (e.g., duralumin), a semiconductor (e.g., silicon), a resin, a composite material such as CFRP (Carbon Fiber Reinforced Plastic), a paint (for example, a paint layer applied to a substrate), glass, or an object made of any other material.

[0014] The surface of the workpiece W may be coated with a film made of a different material than the workpiece W. In this case, the surface of the film coated on the surface of the workpiece W may be the surface processed by the processing device 1. Even in this case, the processing device 1 may be considered to be processing the workpiece W (i.e., processing the workpiece W coated with the film).

[0015] The processing apparatus 1 irradiates the workpiece W with processing light EL in order to process the workpiece W. The processing light EL can be any type of light, as long as it is possible to process the workpiece W by irradiating it. In this embodiment, the explanation will proceed using the example that the processing light EL is laser light, but the processing light EL can be a different type of light from laser light. Furthermore, the wavelength of the processing light EL can be any wavelength, as long as it is possible to process the workpiece W by irradiating it. For example, the processing light EL may be visible light or invisible light (for example, at least one of infrared light, ultraviolet light, and extreme ultraviolet light). The processing light EL includes pulsed light (for example, pulsed light with a pulse width of picoseconds or less). This pulse width is the emission time of the pulsed light. However, the processing light EL does not have to include pulsed light. In other words, the processing light EL may be continuous light.

[0016] The processing light EL is supplied from the processing light source 2 that generates the processing light EL to the processing apparatus 1 via an unillustrated light propagation member (for example, at least one of an optical fiber and a mirror). The processing apparatus 1 irradiates the workpiece W with the processing light EL supplied from the processing light source 2. As described above, if the processing light EL is laser light, the processing light source 2 may include a laser light source (for example, a semiconductor laser such as a laser diode (LD)). The laser light source may include at least one of a fiber laser, CO2 laser, YAG laser, and excimer laser. However, if the processing light EL is not laser light, the processing light source 2 may include any light source (for example, at least one of an LED (Light Emitting Diode) and a discharge lamp).

[0017] The processing apparatus 1 may perform a removal process by irradiating the workpiece W with processing light EL to remove a portion of the workpiece W. For example, the processing apparatus 1 may perform a removal process by utilizing the principle of thermal processing to remove a portion of the workpiece W. Specifically, when processing light EL is irradiated onto the surface of the workpiece W, the energy of the processing light EL is transferred to the irradiated portion of the workpiece W and to the adjacent portion of the workpiece W adjacent to the irradiated portion. When heat caused by the energy of the processing light EL is transferred, the material constituting the irradiated portion and the adjacent portion of the workpiece W melts due to the heat caused by the energy of the processing light EL. The molten material scatters as droplets. Alternatively, the molten material evaporates due to the heat caused by the energy of the processing light EL. As a result, the irradiated portion and the adjacent portion of the workpiece W are removed. When thermal processing is performed, the processing light EL may include pulsed light or continuous light with a pulse width of milliseconds or more.

[0018] On the other hand, depending on the characteristics of the processing light EL, the processing apparatus 1 may perform a removal process to remove a portion of the workpiece W using the principle of non-thermal processing (e.g., ablation processing). In other words, the processing apparatus 1 may perform non-thermal processing (e.g., ablation processing) on ​​the workpiece W. For example, if light with a high photon density (in other words, fluence) is used as the processing light EL, the material constituting the irradiated portion and adjacent portion of the workpiece W will instantly evaporate and scatter. In other words, the material constituting the irradiated portion and adjacent portion of the workpiece W will evaporate and scatter in a time sufficiently shorter than the thermal diffusion time of the workpiece W. In this case, the material constituting the irradiated portion and adjacent portion of the workpiece W may be emitted from the workpiece W as at least one of ions, atoms, radicals, molecules, clusters, and solid fragments. When non-thermal processing is performed, the processing light EL may include pulsed light with a pulse width of picoseconds or less (or, in some cases, nanoseconds or femtoseconds or less). When pulsed light with a pulse width of picoseconds or less (or, in some cases, nanoseconds or femtoseconds or less) is used as the processing light EL, the material constituting the irradiated area and adjacent areas of the workpiece W may sublimate without going through a melting state. Therefore, it becomes possible to process the workpiece W while minimizing the impact of heat caused by the energy of the processing light EL on the workpiece W.

[0019] In this embodiment, the processing apparatus 1 may form a riblet structure RB (see Figure 3, etc.) on the surface of the workpiece W by performing a removal process. The process of forming the riblet structure RB may be called riblet processing. In other words, the processing apparatus 1 may perform riblet processing on the surface of the workpiece W.

[0020] The riblet structure RB may include a textured surface that can reduce the fluid resistance of the workpiece W surface (in particular, at least one of frictional resistance and turbulent frictional resistance). For this reason, the riblet structure RB may be formed on a workpiece W having a member that is placed (in other words, located) in a fluid. In other words, the riblet structure RB may be formed on a workpiece W having a member that moves relative to a fluid. Here, "fluid" means a medium (e.g., at least one of gas and liquid) flowing relative to the surface of the workpiece W. For example, if the surface of the workpiece W moves relative to a medium while the medium itself is stationary, this medium may be referred to as a fluid. The state in which the medium is stationary may mean a state in which the medium is not moving relative to a predetermined reference object (e.g., the ground surface).

[0021] When a riblet structure RB is formed on a workpiece W that includes a structure capable of reducing the fluid resistance on the workpiece W's surface (particularly frictional resistance and at least one of turbulent frictional resistance), the workpiece W becomes more mobile relative to the fluid. As a result, the resistance that hinders the movement of the workpiece W relative to the fluid is reduced, leading to energy savings. In other words, it becomes possible to manufacture environmentally friendly workpieces W, such as turbine blades. This contributes to meeting the United Nations' Sustainable Development Goal (SDG) 7, "Affordable and Clean Energy," and to Target 7.3, "Double the rate of improvement in global energy efficiency by 2030."

[0022] Furthermore, the riblet structure RB may be formed on a workpiece W different from the turbine blade. An example of a workpiece W on which the riblet structure RB is formed is at least one of a turbine vane, fan, impeller, propeller, and pump, which may also be called a stator vane. A fan is a component (typically a rotating body) used in blowers and the like to form a flow of gas. An impeller is, for example, a component used in a pump, and is a rotatable vane that generates a force that causes the pump to pump (or suck) fluid. A propeller is, for example, a component (typically a rotating body) that converts rotational force output from a prime mover, including at least one of an engine and a motor, into thrust force for a moving body, including at least one of an airplane and a ship. Another example of a workpiece W on which the riblet structure RB is formed is the housing (e.g., airframe or hull) of a moving body, including at least one of an airplane and a ship.

[0023] Here, the riblet structure RB will be described with reference to Figures 3A, 3B, and 3C. As shown in Figures 3A, 3B, and 3C, the riblet structure RB may include a structure in which multiple convex structures 81 extending along a first direction along the surface of the workpiece W are arranged along a second direction that is along the surface of the workpiece W and intersects the first direction. In other words, the riblet structure RB may include a structure in which multiple convex structures 81, each formed to extend along the first direction, are arranged along the second direction. In the example shown in Figures 3A, 3B, and 3C, the riblet structure RB includes a structure in which multiple convex structures 81 extending along the X-axis are arranged along the Y-axis.

[0024] The convex structure 81 is a structure that protrudes along a direction that intersects both the first direction (the direction in which the convex structure 81 extends) and the second direction (the direction in which the convex structures 81 are arranged). The convex structure 81 is a structure that protrudes from the surface of the workpiece W. In the examples shown in Figures 3A, 3B, and 3C, the convex structure 81 is a structure that protrudes along the Z-axis direction. The convex structure 81 may include a protruding shape that is a projection relative to the surface of the workpiece W. The convex structure 81 may include a convex shape that is convex relative to the surface of the workpiece W. The convex structure 81 may include a mountain-shaped structure that is a peak relative to the surface of the workpiece W. Between adjacent convex structures 81, groove structures 82 that are recessed compared to the surrounding area are formed. Therefore, the riblet structure RB may include a structure in which multiple groove structures 82 extending along a first direction along the surface of the workpiece W are arranged along a second direction that is also along the surface of the workpiece W and intersects the first direction. In other words, the riblet structure RB may include a structure in which multiple groove structures 82, each formed to extend along the first direction, are arranged along the second direction. In the examples shown in Figures 3A, 3B, and 3C, the riblet structure RB includes a structure in which multiple groove structures 82 extending along the X-axis are arranged along the Y-axis. The groove structure 82 may also be referred to as a groove-like structure.

[0025] Furthermore, the convex structure 81 may be considered as a structure protruding from the groove structure 82. The convex structure 81 may be considered as a structure that forms at least one of a projection-shaped structure, a convex-shaped structure, and a mountain-shaped structure between two adjacent groove structures 82. The groove structure 82 may be considered as a structure recessed from the convex structure 81. The groove structure 82 may be considered as a structure that forms a groove-shaped structure between two adjacent convex structures 81. Furthermore, the groove structure 82 may be referred to as a groove-like structure.

[0026] The height H_rb of at least one of the multiple convex structures 81 may be set to a height determined according to the pitch P_rb of the convex structure 81. For example, the height H_rb of at least one of the multiple convex structures 81 may be less than or equal to the pitch P_rb of the convex structure 81. For example, the height H_rb of at least one of the multiple convex structures 81 may be less than or equal to half the pitch P_rb of the convex structure 81. As an example, the pitch P_rb of the convex structure 81 may be greater than 5 micrometers and less than 200 micrometers. In this case, the height H_rb of at least one of the multiple convex structures 81 may be greater than 2.5 micrometers and less than 100 micrometers.

[0027] To process such a riblet structure RB onto a workpiece W, the processing apparatus 1, as shown in Figures 1 and 2, includes, in addition to the processing head 11 described above, a head drive system 12 (in the example of Figure 1, a self-propelled drive unit 101 and an articulated robot 102), a stage 13, and a stage drive system 14. The processing head 11 irradiates the workpiece W with processing light EL from the processing light source 2. To irradiate the workpiece W with processing light EL, the processing head 11 is equipped with a processing optical system 15. The processing head 11 irradiates the workpiece W with processing light EL via the processing optical system 15.

[0028] In this embodiment, the processing optical system 15 may form a riblet structure RB on the surface of the workpiece W by forming interference fringes IS (see Figure 4, etc.) on the surface of the workpiece W. Specifically, the processing optical system 15 irradiates the workpiece W with multiple processing light ELs (two processing light ELs in the example shown in Figure 1) generated by splitting the processing light EL from the processing light source 2, each from a different incident direction. As a result, interference light is generated by the interference of the multiple processing light ELs. In this case, the processing optical system 15 can be considered to be essentially irradiating the workpiece W with interference light generated by the interference of multiple processing light ELs. As a result, interference fringes IS caused by the interference light are formed on the surface of the workpiece W. The detailed structure of the processing optical system 15 will be described in detail later with reference to Figure 5, etc., so the explanation is omitted here.

[0029] An example of interference fringes IS is shown in Figure 4. Interference fringes IS may have bright areas IL and dark areas ID. Bright areas IL may include portions of interference fringes IS where the fluence is greater than a predetermined amount (i.e., high). Bright areas IL may include portions illuminated by light from the interference light forming the interference fringes IS where the fluence is greater than a predetermined amount. Dark areas ID may include portions of interference fringes IS where the fluence is smaller than a predetermined amount (i.e., low). Dark areas ID may include portions illuminated by light from the interference light forming the interference fringes IS where the fluence is smaller than a predetermined amount. Also, the fluence in bright areas IL may be greater than the fluence in dark areas ID.

[0030] Figure 4 further shows the relationship between the interference fringes IS and the riblet structure RB. The bright areas IL may be used primarily to form the groove structure 82 described above. In this case, the processing optical system 15 may form the groove structure 82 constituting the riblet structure RB on the surface of the workpiece W by forming the bright areas IL included in the interference fringes IS on the surface of the workpiece W and removing a part of the workpiece W. The processing optical system 15 may also form the groove structure 82 on the surface of the workpiece W by irradiating the surface of the workpiece W with the light portion of the interference light that forms the bright areas IL and removing a part of the workpiece W. The processing optical system 15 may also form the groove structure 82 on the surface of the workpiece W by removing a part of the workpiece W using processing light EL that reaches the bright areas IL (i.e., using the light portion of the processing light EL that reaches the bright areas IL). In this case, the interference fringes IS may include multiple fringes arranged along the direction in which the groove structure 82 extends (the X-axis direction in the example of Figure 4) and the direction in which the groove structure 82 is aligned (the Y-axis direction (fringe pitch direction) in the example of Figure 4). In other words, the interference fringes IS may include multiple bright areas IL extending along the direction in which the groove structure 82 extends (the X-axis direction in the example of Figure 4), and fringes that are aligned along the direction in which the groove structure 82 is aligned (the Y-axis direction (fringe pitch direction) in the example of Figure 4).

[0031] The dark area ID may be used primarily to form the convex structure 81 described above. In this case, the processing optical system 15 may form the dark area ID included in the interference fringe IS on the surface of the workpiece W and remove a part of the workpiece W (or, in some cases, not remove a part of the workpiece W) to form the convex structure 81 constituting the riblet structure RB on the surface of the workpiece W. The processing optical system 15 may also form the convex structure 81 on the surface of the workpiece W by irradiating the surface of the workpiece W with the light portion of the interference light that forms the dark area ID and removing a part of the workpiece W. The processing optical system 15 may also form the convex structure 81 on the surface of the workpiece W by removing a part of the workpiece W using processing light EL that reaches the dark area ID (that is, using the light portion of the processing light EL that reaches the dark area ID). In this case, the interference fringe IS may include multiple fringes arranged along the direction in which the convex structure 81 is aligned (the Y-axis direction in the example of Figure 4), where the dark area ID extending along the direction in which the convex structure 81 extends (the X-axis direction in the example of Figure 4). In other words, the interference fringes IS may include multiple dark areas ID extending along the direction in which the convex structure 81 extends (the X-axis direction in the example of Figure 4), and fringes that are aligned along the direction in which the convex structures 81 are aligned (the Y-axis direction in the example of Figure 4).

[0032] As shown in Figures 1 and 2, the head drive system 12 (self-propelled drive unit 101, articulated robot 102) moves the machining head 11 along at least one of the X-axis, Y-axis, and Z-axis directions under the control of the control device 3. The head drive system 12 may also move the machining head 11 along at least one of the θX, θY, and θZ directions in addition to or instead of at least one of the X-axis, Y-axis, and Z-axis directions. When the machining head 11 moves, the positional relationship between the stage 13 (and furthermore, the workpiece W placed on the stage 13) and the machining head 11 changes. As a result, the positional relationship between the interference region IA (see Figure 4), where the machining head 11 forms interference fringes IS on the workpiece W, and the stage 13 and the workpiece W changes. In other words, the interference region IA can be moved on the workpiece W. A workpiece W is placed on the stage 13. The stage 13 does not have to hold the workpiece W placed on it. In other words, the stage 13 does not have to apply a holding force to the workpiece W placed on it. Alternatively, the stage 13 may hold the workpiece W placed on it. In other words, the stage 13 may apply a holding force to the workpiece W placed on it. For example, the stage 13 may hold the workpiece W by vacuum adsorption and / or electrostatic adsorption. Alternatively, a fixture for holding the workpiece W may hold the workpiece W, and the stage 13 may hold the fixture holding the workpiece W.

[0033] The stage drive system 14 moves the stage 13 under the control of the control device 3. Specifically, the stage drive system 14 moves the stage 13 relative to the machining head 11. For example, the stage drive system 14 may move the stage 13 along at least one of the following directions under the control of the control device 3: the X-axis direction, the Y-axis direction, the Z-axis direction, the θX direction, the θY direction, and the θZ direction. Moving the stage 13 along at least one of the θX, θY, and θZ directions may be considered equivalent to changing the orientation of the stage 13 (and furthermore, the workpiece W placed on the stage 13) around at least one of the X, Y, and Z axes. Alternatively, moving the stage 13 along at least one of the θX, θY, and θZ directions may be considered equivalent to rotating (or rotating) the stage 13 around at least one of the X, Y, and Z axes.

[0034] When stage 13 moves, the positional relationship between stage 13 (and consequently, the workpiece W placed on stage 13) and the machining head 11 changes. Furthermore, the positional relationship between stage 13 and workpiece W, and the interference region IA (see Figure 4) on workpiece W where the machining head 11 forms interference fringes IS as a result of machining, changes. In other words, the interference region IA moves on workpiece W.

[0035] Furthermore, the machining system SYS may change the positional relationship between the workpiece W placed on the stage 13 and the machining head 11 by moving both the stage 13 and the machining head 11 under the control of the control device 3. Alternatively, the machining system SYS may move the interference fringes IS relative to the workpiece W without moving the machining head 11 or the stage 13.

[0036] The control device 3 controls the operation of the machining system SYS. For example, the control device 3 may generate machining control information for machining the workpiece W, and may also control the machining device 1 based on the generated machining control information so that the workpiece W is machined according to that information. In other words, the control device 3 may control the machining of the workpiece W.

[0037] The control device 3 may include, for example, an arithmetic unit and a memory device. The arithmetic unit may include, for example, at least one of a CPU (Central Processing Unit) and a GPU (Graphics Processing Unit). The control device 3 functions as a device that controls the operation of the machining system SYS by having the arithmetic unit execute a computer program. This computer program is a computer program that causes the control device 3 (for example, the arithmetic unit) to perform (i.e., execute) the operations that the control device 3 should perform, as described later. In other words, this computer program is a computer program that causes the control device 3 to function so that the machining system SYS performs the operations described later. The computer program executed by the arithmetic unit may be recorded in a memory device (i.e., a recording medium) provided by the control device 3, or it may be recorded in any storage medium (for example, a hard disk or semiconductor memory) that is built into or can be attached to the control device 3. Alternatively, the arithmetic unit may download the computer program to be executed from an external device of the control device 3 via a network interface.

[0038] The control device 3 does not have to be located inside the machining system SYS. For example, the control device 3 may be located outside the machining system SYS as a server or the like. In this case, the control device 3 and the machining system SYS may be connected by a wired and / or wireless network (or a data bus and / or communication line). As a wired network, a network using a serial bus interface, such as at least one of IEEE1394, RS-232x, RS-422, RS-423, RS-485, and USB, may be used. As a wired network, a network using a parallel bus interface may be used. As a wired network, a network using an Ethernet® compliant interface, such as at least one of 10BASE-T, 100BASE-TX, and 1000BASE-T, may be used. As a wireless network, a network using radio waves may be used. An example of a network using radio waves is a network compliant with IEEE802.1x (for example, at least one of wireless LAN and Bluetooth®). As a wireless network, a network using infrared may be used. A network using optical communication may be used as the wireless network. In this case, the control device 3 and the machining system SYS may be configured to enable the transmission and reception of various types of information via the network. The control device 3 may also be able to transmit information such as commands and control parameters to the machining system SYS via the network. The machining system SYS may be equipped with a receiving device that receives information such as commands and control parameters from the control device 3 via the network. Alternatively, a first control device that performs some of the processing performed by the control device 3 may be provided inside the machining system SYS, while a second control device that performs other parts of the processing performed by the control device 3 may be provided outside the machining system SYS.

[0039] The control device 3 may implement a computational model that can be constructed by machine learning, which is achieved by the execution of a computer program by the arithmetic unit. An example of a computational model that can be constructed by machine learning is a computational model that includes a neural network (so-called artificial intelligence (AI)). In this case, the learning of the computational model may include learning the parameters of the neural network (for example, at least one of the weights and biases). The control device 3 may use the computational model to control the operation of the machining system SYS. In other words, the operation of controlling the operation of the machining system SYS may include the operation of controlling the operation of the machining system SYS using the computational model. The control device 3 may also implement a computational model that has been constructed by offline machine learning using training data. Furthermore, the computational model implemented in the control device 3 may be updated by online machine learning on the control device 3. Alternatively, the control device 3 may use, in addition to or instead of, the computational model implemented in the control device 3 to control the operation of the machining system SYS using a computational model implemented in an external device (i.e., a device located outside the machining system SYS).

[0040] Furthermore, as the recording medium for recording the computer program executed by the arithmetic unit, at least one of the following may be used: optical discs such as CD-ROM, CD-R, CD-RW, flexible disk, MO, DVD-ROM, DVD-RAM, DVD-R, DVD+R, DVD-RW, DVD+RW, and Blu-ray®; magnetic media such as magnetic tape; magneto-optical disks; semiconductor memory such as USB memory; and any other medium capable of storing a program. The recording medium may also include equipment capable of recording the computer program (for example, a general-purpose or dedicated device on which the computer program is implemented in a state in which it can be executed in at least one form, such as software and firmware). Moreover, each process and function included in the computer program may be realized by logical processing blocks realized within the control device 3 (i.e., the computer) when the control device 3 executes the computer program, or by hardware such as a predetermined gate array (FPGA, ASIC) provided in the control device 3, or in a form in which logical processing blocks and partial hardware modules that realize some elements of the hardware are mixed.

[0041] (2) Processing optical system 15 (2-1) Overview of the processing optical system 15 Next, the processing optical system 15 that forms interference fringes IS on the surface of the workpiece W will be described. As shown in Figure 5, the processing optical system 15 has a first optical system 16, a second optical system 17, and a third optical system 18. The processing optical system 15 splits the processing light EL generated by the processing light source 2 into two processing light ELs in the first optical system 16, and irradiates the workpiece W from the third optical system 18 with one of them. The processing optical system 15 also splits the other branched processing light EL in the second optical system 17 to generate multiple processing light ELs (two processing light ELs in the example shown in Figure 1), and irradiates the workpiece W from different directions. At this time, interference light is generated by the interference of the multiple processing light ELs generated by the second optical system 17. For this reason, the processing optical system 15 can be considered to be irradiating the workpiece W with interference light generated by the interference of multiple processing light ELs. In this manner, the processing optical system 15 forms interference fringes IS caused by interference light in the interference region IA on the surface of the workpiece W by the second optical system 17, and irradiates the interference region IA with processing light EL from the third optical system 18.

[0042] In the following explanation, each processing light EL will be distinguished by the following names. First, the processing light EL generated by the processing light source 2 will be called processing light EL0, and the portion of processing light EL0 that is branched by the first optical system 16 and directed to the third optical system 18 will be called the first processing light EL1. Furthermore, the portion of processing light EL0 that is branched by the first optical system 16 and directed to the second optical system 17 will be called the second processing light EL2, and the portion of the second processing light EL2 that is divided by the second optical system 17 and irradiated onto the workpiece W will be called the second processing light EL22. Finally, the portion of the first processing light EL1 from the first optical system 16 that is irradiated onto the workpiece W by the third optical system 18 will be called the first processing light EL11.

[0043] Therefore, the first optical system 16 generates a first processing light EL1 and a second processing light EL2 as pulsed light whose emission periods overlap at least partially by branching the processing light EL0 from the processing light source 2, and can also be called a branching optical system. Furthermore, the second optical system 17 can also be called an interference fringe forming optical system, which forms interference fringes IS on the surface of the workpiece W by irradiating the workpiece W with multiple second processing light EL22 generated by dividing the second processing light EL2 from different incident directions. And the third optical system 18 can also be called an irradiation optical system that irradiates the first processing light EL11 from the first processing light EL1 towards the interference region IA where the interference fringes IS are formed.

[0044] As described above, the processing optical system 15 forms interference fringes IS by irradiating the workpiece W with multiple second processing light beams EL22 from the second optical system 17 from different incident directions. Here, the number of multiple processing light beams EL22 may be an integer of 2 or more, as long as they form interference fringes IS.

[0045] In this embodiment, in addition to the interference region IA caused by multiple second processing lights EL22, the first processing light EL11 from the third optical system 18 is irradiated, and the fluence distribution of the processing light in the interference region IA where interference fringes IS are formed on the surface of the workpiece W changes compared to the comparative example where the first processing light EL11 is not irradiated. Specifically, Figure 6A shows the fluence distribution of the processing light in the comparative example, and Figure 6B shows the fluence distribution of the processing light in this embodiment. As shown in Figures 6A and 6B, in this embodiment, the minimum fluence of the processing light is higher compared to the comparative example. Note that the minimum fluence may be the minimum value of the fluence of the processing light at the dark area ID of the interference fringe IS. The minimum fluence may be the minimum value of the fluence of the processing light reaching the dark area ID of the interference fringe IS. The reason why the minimum fluence in this embodiment is larger than the minimum fluence in the comparative example is that by irradiating with multiple second processing lights EL22 and the first processing light EL11 in overlapping order, light components that affect the fluence distribution are introduced into the processing light without affecting the formation of the interference fringe IS. In other words, the processing optical system 15 imparts a light component to the interference light that affects the fluence distribution (the so-called DC component of the fluence distribution of the interference fringes IS) without affecting the formation of the interference fringes IS, by irradiating multiple second processing lights EL22 and first processing lights EL11 in combination. The processing optical system 15 imparts a light component to the interference light that affects the contrast component of the fluence distribution (i.e., the component that affects the intensity (brightness) of the interference fringes IS) without affecting the formation of the interference fringes IS, by irradiating multiple second processing lights EL22 and first processing lights EL11 in combination.

[0046] Conversely, the processing optical system 15 may superimpose the first processing light EL11 onto multiple second processing light EL22 such that it imparts a light component to the interference light that affects the fluence distribution but does not affect the formation of interference fringes IS. The processing optical system 15 may superimpose the first processing light EL11 onto multiple second processing light EL22 such that it imparts a light component to the interference light that increases the minimum fluence but does not affect the formation of interference fringes IS. Furthermore, the first processing light EL11 (its fluence) superimposed onto multiple second processing light EL22 may be set to allow the imparting of a light component to the interference light that affects the fluence distribution but does not affect the formation of interference fringes IS. The first processing light EL11 (its fluence) superimposed onto multiple second processing light EL22 may be determined based on at least one of the characteristics of the processing light EL0, the characteristics of the interference light, the characteristics of the workpiece W, and the characteristics of the riblet structure RB. The first processing light EL11 (its fluence) that is superimposed on multiple second processing light EL22 may be determined based on the results of experiments or simulations that form interference fringes IS to create a riblet structure RB on the workpiece W.

[0047] As shown in Figure 6A, in the comparative example, the riblet structure RB formed may have a flat tip shape. This is because, as mentioned above, the minimum fluence is relatively small in the comparative example. Therefore, as shown in Figure 6A, in the comparative example, there is a relatively high possibility that the fluence of at least a portion of the dark area ID of the interference fringe IS will be smaller than the lower limit TH_lowest fluence that allows the workpiece W to be machined (i.e., a portion of the workpiece W to be removed). As a result, at least a portion of the workpiece W where the dark area ID of the interference fringe IS is formed will not be machined, and consequently, there is a relatively high possibility that the tip shape of the convex structure 81 will be flat. Considering the characteristics of the riblet structure RB, if the tip shape of the convex structure 81 is flat, the effect of reducing the fluid resistance on the surface of the workpiece W may be reduced compared to the case where the tip shape of the convex structure 81 is pointed.

[0048] On the other hand, as shown in Figure 6B, in the riblet structure RB formed in this embodiment, the possibility of the tip shape of the convex structure 81 being flat is lower compared to the comparative example. This is because, as mentioned above, the minimum fluence is relatively large in this embodiment. Therefore, as shown in Figure 6B, in this embodiment, the possibility that the fluence of at least a portion of the dark area ID of the interference fringe IS becomes smaller than the lower limit value TH_lowest of the fluence that allows the workpiece W to be machined is relatively low. In other words, the possibility that the fluence of at least a portion of the dark area ID of the interference fringe IS is set to a fluence that allows the workpiece W to be machined is relatively high. As a result, the portion of the workpiece W in which the dark area ID of the interference fringe IS is formed is machined, and as a result, the possibility that the tip shape of the convex structure 81 approaches or matches an ideal shape (for example, a pointed shape) is relatively high. In other words, in this embodiment, the accuracy of the shape of the riblet structure RB is improved compared to the comparative example. As a result, in this embodiment, the possibility of forming a riblet structure RB that is relatively effective in reducing the fluid resistance of the surface of the workpiece W is relatively high.

[0049] Thus, the processing apparatus 1 of this embodiment can bring the shape of the riblet structure RB closer to or match the ideal shape compared to the comparative example. The processing apparatus 1 can form a riblet structure RB having a shape that is close to or matches the ideal shape compared to the comparative example. In this case, the processing apparatus 1 may be considered to be adjusting the shape of the riblet structure RB by superimposing the first processing light EL11 onto a plurality of second processing light EL22 so that the shape of the riblet structure RB formed on the workpiece W becomes a predetermined shape that is closer to the ideal shape than the shape of the riblet structure RB formed in the comparative example. As a result, the processing apparatus 1 can enjoy the effect of being able to appropriately process the workpiece W to form a riblet structure RB having a shape that is close to or matches the ideal shape.

[0050] Furthermore, considering that the above-mentioned effects can be appropriately enjoyed when the minimum fluence of the processing light is equal to or greater than the lower limit value TH_lowest of the fluence that can process the workpiece W, the processing optical system 15 may set the first processing light EL11 (its fluence) that is superimposed on multiple second processing light EL22s so that the minimum fluence of the processing light is set to be equal to or greater than the lower limit value TH_lowest. The processing optical system 15 may set the first processing light EL11 (its fluence) that is superimposed on multiple second processing light EL22s so that the minimum fluence of the processing light is set to a fluence that can process the workpiece W. The first processing light EL11 (its fluence) that is superimposed on multiple second processing light EL22s may be set so that the minimum fluence of the processing light is a fluence that can process the workpiece W. As a result, the above-mentioned effects can be appropriately enjoyed.

[0051] Depending on the characteristics of the workpiece W, the relationship between the fluence of the light irradiated onto the workpiece W and the amount of processing on the workpiece W (for example, the amount of removal per unit time, or, as one example, the amount of processing per pulse) may fluctuate depending on the fluence. For example, depending on the characteristics of the workpiece W, as shown in Figure 7, the first relationship between the fluence and the amount of processing on the workpiece W when the fluence of the processing light irradiated onto the workpiece W (or the fluence of multiple second processing lights EL22 that generate interference light and the fluence of the first processing light EL11 superimposed on them) is smaller than a predetermined threshold Fth may differ from the second relationship between the fluence and the amount of processing on the workpiece W when the fluence of the processing light (interference light) irradiated onto the workpiece W is larger than a predetermined threshold Fth. In this case, if the fluence of the processing light changes to span both a first range smaller than a predetermined threshold Fth and a second range larger than a predetermined threshold Fth, as shown in the upper part of Figure 7, the amount of processing in the first part of the workpiece W, which is irradiated with the portion of the processing light having a fluence smaller than the predetermined threshold Fth, will differ from the amount of processing in the second part of the workpiece W, which is irradiated with the portion of the processing light having a fluence larger than the predetermined threshold Fth. In the example shown in Figure 7, the ratio of the increase in processing amount to the increase in fluence in the second relationship is greater than the ratio of the increase in processing amount to the increase in fluence in the first relationship. In this case, the amount of processing in the first part of the workpiece W, which is irradiated with the portion of the processing light having a fluence smaller than the predetermined threshold Fth, will be less than the amount of processing in the second part of the workpiece W, which is irradiated with the portion of the processing light having a fluence larger than the predetermined threshold Fth. As a result, there is a possibility that the amount of processing in the first part of the workpiece W will be insufficient and / or the amount of processing in the second part of the workpiece W will be excessive. Therefore, the accuracy of the shape of the riblet structure RB formed on the workpiece W may deteriorate. For example, as shown in the lower part of Figure 8, the tip of the convex structure 81, which is mainly formed by the light portion of the processing light with a relatively low fluence (for example, the light portion that illuminates the dark area ID), may have a flat shape.

[0052] Therefore, as shown in the upper part of Figure 9, the processing optical system 15 may set the first processing light EL11 (its fluence) to be irradiated in conjunction with the multiple second processing light EL22 so that the minimum fluence of the interference light is equal to or greater than a predetermined threshold Fth. Alternatively, the processing optical system 15 may set the first processing light EL11 (its fluence) to be irradiated in conjunction with the multiple second processing light EL22 so that the minimum fluence of the interference light is equal to or greater than a threshold obtained by adding a predetermined margin to the predetermined threshold Fth. In other words, the processing optical system 15 may set the first processing light EL11 (its fluence) to be irradiated in conjunction with the multiple second processing light EL22 so that the minimum fluence of the interference light is equal to or greater than a threshold set based on the predetermined threshold Fth. In this case, as shown in the lower part of Figure 9, the possibility of the tip shape of the convex structure 81, which is mainly formed by the light portion of the processing light with a relatively small fluence (for example, the light portion irradiated onto the dark area ID), becoming an ideal shape becomes relatively higher. As a result, the above-mentioned effects can be appropriately enjoyed.

[0053] In other words, the object (workpiece W in the above embodiment) has the characteristic that the first relationship between fluence and processing amount when the fluence of each processing light is smaller than a predetermined threshold is different from the second relationship between fluence and processing amount when the fluence of each processing light is larger than a predetermined threshold. The ratio of the increase in processing amount to the increase in the fluence of the processing light in the second relationship is greater than the ratio of the increase in processing amount to the increase in the fluence of the processing light in the first relationship. The second optical system 17 sets the first processing light EL11 from the third optical system 18 such that the minimum fluence of the processing light reaching the dark part of the interference fringes is greater than or equal to a predetermined threshold.

[0054] Here, the riblet structure RB is unlikely to have a clean sinusoidal waveform in terms of the processing light pattern (waveform shape, hereafter also referred to as the ideal waveform Wi) required to obtain the ideal shape. However, since the riblet structure RB has a periodic shape, the ideal waveform Wi will also be periodic. For this reason, the ideal waveform Wi can be represented by multiple sinusoidal waveforms by performing a Fourier transform. An example of this is shown in Figures 10A and 10B. Figure 10A shows an example of the ideal waveform Wi, and Figure 10B shows two waveforms (fundamental frequency waveform Wb and double frequency waveform Wd) obtained by performing a Fourier transform on the ideal waveform Wi. Therefore, the ideal waveform Wi in Figure 10A is a superposition of the fundamental frequency waveform Wb and double frequency waveform Wd in Figure 10B.

[0055] Therefore, the processing optical system 15 processes the workpiece W by forming interference fringes IS (hereinafter also referred to as interference fringe IS1) that show the fundamental frequency waveform Wb, and by forming interference fringes IS (hereinafter also referred to as interference fringe IS2) that show the second frequency waveform Wd, thereby forming a riblet structure RB with an ideal shape. In other words, the processing optical system 15 forms an interference fringe IS that shows an ideal waveform Wi by using interference fringes IS1 and IS2, thereby forming a riblet structure RB with an ideal shape. The processing optical system 15 can also form interference fringes IS1 and IS2 instead of forming interference fringes IS that show the ideal waveform Wi in order to form a riblet structure RB with an ideal shape.

[0056] The ideal waveform Wi changes depending on the shape required for the riblet structure RB, and the number and types of sinusoidal waveforms (frequency multiples, amplitude, etc.) obtained by the Fourier transform also change accordingly. Therefore, the processing optical system 15 should appropriately set the shape of the fundamental frequency waveform Wb, and the number and shape of the nth frequency waveforms Wn superimposed on the fundamental frequency waveform Wb, according to the ideal waveform Wi set to form the required riblet structure RB. Here, the processing optical system 15 may superimpose at least one nth frequency waveform Wn, also obtained by the Fourier transform, onto the fundamental frequency waveform Wb obtained by the Fourier transform of the ideal waveform Wi. Alternatively, the processing optical system 15 may superimpose two nth frequency waveforms Wn, also obtained by the Fourier transform, onto the fundamental frequency waveform Wb obtained by the Fourier transform of the ideal waveform Wi. Furthermore, the processing optical system 15 may superimpose three or more nth frequency waveforms Wn, also obtained by the Fourier transform, onto the fundamental frequency waveform Wb obtained by the Fourier transform of the ideal waveform Wi.

[0057] Based on these considerations, the processing optical system 15 splits the processing light EL0 from the processing light source 2 into a first processing light EL1 and a second processing light EL2 in the first optical system 16. Furthermore, the processing optical system 15 generates a fundamental frequency waveform Wb and multiple n-th frequency waveforms Wn as the second processing light EL22 from the second processing light EL2 in the second optical system 17, and irradiates the workpiece W from different incident directions with each of these to form interference fringes IS for each frequency. Then, the processing optical system 15 uses a third optical system 18 to irradiate the interference region IA where each interference fringe IS is formed with the first processing light EL1 as the first processing light EL11, superimposing it on each second processing light EL22. As a result, the processing optical system 15 can process the workpiece W appropriately with each interference fringe IS, and by superimposing the interference fringes IS, it can form a riblet structure RB with an ideal shape similar to that when an ideal waveform Wi is used.

[0058] Here, in the interference fringe IS, the period changes according to the angle of the interfering second processing light EL22; the smaller the angle, the longer the period, and the larger the angle, the narrower (shorter) the period. Also, in the interference fringe IS, the amplitude changes according to the fluence of the multiple second processing light EL22. For this reason, the second optical system 17 can change at least one of the amplitude and period in the interference fringe IS by changing the incident angle of the multiple emitted second processing light EL22, thereby forming interference fringe IS of the fundamental frequency waveform Wb and the nth frequency waveform Wn. Furthermore, by making the second optical system 17 capable of adjusting at least one of the amplitude and period in the interference fringe IS by changing the incident angle of the multiple emitted second processing light EL22, the fundamental frequency waveform Wb and the nth frequency waveform Wn can be made appropriate.

[0059] Next, five examples of processing methods using the processing optical system 15 will be explained using Figure 11. Figure 11 is a table summarizing the characteristics (formation) of the first processing light EL11 in the irradiation area RA, the interference fringes IS in the interference area IA, and the superimposed area OA in the processing area PA, which will be described later, in the five examples. Here, the processing area PA is the area in which the riblet structure RB can be processed by the processing optical system 15 (processing head 11), that is, the area in which the first processing light EL11 and the second processing light EL22 can be irradiated. This irradiable area includes the fact that the first processing light EL11 and the second processing light EL22 can be irradiated at once (simultaneously), and that it is the sum of the areas in which the first processing light EL11 and the processing light EL22 are irradiated by scanning or sweeping (displacing the irradiation position) the first processing light EL11 and the second processing light EL22 by the galvanometer mirror 21 (see Figure 12, etc.), which will be described later. In other words, the processing area PA is a region in which the workpiece W placed on the stage 13 can be irradiated with the first processing light EL11 and the second processing light EL22 without relatively moving the stage 13 and the processing optical system 15 (processing head 11). In this embodiment, the processing area PA is rectangular in shape, having sides extending in the X-axis direction and sides extending in the Y-axis direction. Furthermore, in the processing optical system 15 (processing head 11), the region in which the first processing light EL11 is irradiated by the third optical system 18 is defined as the irradiation area RA.

[0060] Furthermore, in the following, when the interference region IA or the irradiation region RA is smaller than the processing region PA, the galvanometer mirror 21, described later, is used to scan the entire processing region PA with the first processing light EL11 and the second processing light EL22 (the entire area is the scanning range). For this reason, the galvanometer mirror 21 functions as an interference fringe shifting member that moves the position of the interference region IA in a direction that intersects the optical axis of the second optical system 17, typically orthogonal. In addition, the galvanometer mirror 21, as an interference fringe shifting member, also has the function of moving the position of the irradiation region RA in a direction that intersects the optical axis of the second optical system 17, typically orthogonal. Note that this scanning range may be smaller than the processing region PA (only a part of the processing region PA is processed). Also, the processing region PA may be set smaller than the range in which the first processing light EL11 and the second processing light EL22 can actually be scanned. In this case, the scanning range may be larger than the processing area PA (the first processing light EL11 and the second processing light EL22 may be irradiated over a wider area than the processing area PA).

[0061] Figure 11 shows five examples of processing methods using processing optical systems 15A, 15B, 15C, 15D, and 15E, from left to right. Figure 11 also shows the configuration of the irradiation area RA due to the first processing light EL11 in the upper section, the configuration of the interference area IA (interference fringes IS) due to the second processing light EL22 in the middle section, and the configuration of the irradiation area RA and interference area IA (superimposed area OA, described later) in the processing area PA in the lower section.

[0062] In the processing method using the processing optical system 15A, as shown in the upper panel, the irradiation area RA (hereinafter referred to as irradiation area RA1) of the first processing light EL11 from the third optical system 18 is made smaller than the processing area PA (see lower panel). Specifically, in the processing method using the processing optical system 15A, the irradiation area RA1 is rectangular in shape, with the same size as the processing area PA in the Y-axis direction, but smaller than the processing area PA in the X-axis direction.

[0063] Furthermore, in the processing method using the processing optical system 15A, as shown in the middle section, the interference region IA, in which interference fringes IS are formed by multiple second processing light beams EL22 from the second optical system 17, is rectangular in shape and approximately the same size as the irradiation region RA1. In the processing method using the processing optical system 15A, interference fringes IS1 (hereinafter referred to as interference region IA1) showing the fundamental frequency waveform Wb and interference fringes IS2 (hereinafter referred to as interference region IA2) showing the double frequency waveform Wd are formed in the interference region IA at different timings (times).

[0064] In the processing method using the processing optical system 15A, as shown in the lower panel, the interference region IA1, which forms interference fringes IS1 showing the fundamental frequency waveform Wb, and the irradiation region RA1 formed by irradiation with the first processing light EL11 are superimposed. Hereafter, the region where the interference region IA1 and the irradiation region RA1 overlap will also be called the superimposed region OA1. In the processing method using the processing optical system 15A, this superimposed region OA1 is scanned over the entire processing region PA. That is, in the processing method using the processing optical system 15A, the interference region IA1 and the irradiation region RA1 are superimposed at one end of the processing region PA in the X-axis direction to form the superimposed region OA1, and the entire processing region PA is scanned by moving the superimposed region OA1 toward the other end in the X-axis direction. Subsequently, in the processing method using the processing optical system 15A, the interference region IA2, which forms interference fringes IS2 showing the 2x frequency waveform Wd, and the irradiation region RA1 formed by irradiation with the first processing light EL11 are superimposed to form the superimposed region OA2. In the machining method using the machining optical system 15A, the entire machining area PA is scanned with superimposed area OA2, which includes the double frequency waveform Wd, similar to superimposed area OA1, which includes the fundamental frequency waveform Wb.

[0065] As a result, in the processing method using the processing optical system 15A, the entire processing area PA on the surface of the workpiece W can be irradiated with interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd. In this case, in the processing method using the processing optical system 15A, the first processing light EL11 is superimposed on each of the interference fringes IS1 and IS2, so the workpiece W can be processed appropriately even in the areas where the dark areas ID of each interference fringe IS1 and IS2 are formed. Therefore, in the processing method using the processing optical system 15A, an ideally shaped riblet structure RB can be formed on the surface of the workpiece W in the processing area PA.

[0066] In the processing method using the processing optical system 15B, as shown in the upper panel, the irradiation area RA (hereinafter referred to as irradiation area RA2) of the first processing light EL11 from the third optical system 18 is made smaller than the processing area PA. Specifically, in the processing method using the processing optical system 15B, the irradiation area RA2 is rectangular in shape, being the same size as the processing area PA in the Y-axis direction, but smaller than the processing area PA in the X-axis direction.

[0067] Furthermore, in the processing method using the processing optical system 15B, as shown in the middle section, the interference region IA (hereinafter referred to as interference region IA3) where interference fringes IS are formed by multiple second processing light EL22 from the second optical system 17 is rectangular in shape and approximately the same size as the irradiation region RA2. In the processing method using the processing optical system 15B, interference fringes IS1 representing the fundamental frequency waveform Wb and interference fringes IS2 representing the double frequency waveform Wd are formed in parallel in the X-axis direction in the interference region IA3. That is, in the processing method using the processing optical system 15B, interference fringes IS2 of the double frequency waveform Wd are formed on one end of the interference region IA3 in the X-axis direction, and interference fringes IS1 of the fundamental frequency waveform Wb are formed side by side on the other end in the X-axis direction. In this example, in the interference region IA3, the region where interference fringes IS1 of the fundamental frequency waveform Wb are formed becomes the first region, and the region where interference fringes IS2 of the double frequency waveform Wd are formed becomes the second region. Note that the order of the first and second regions can be set as appropriate and is not limited to this example.

[0068] In the processing method using the processing optical system 15B, as shown in the lower panel, an interference region IA3 formed by arranging interference fringes IS1 and IS2 of two types of frequency waveforms Wb and Wd is superimposed with an irradiation region RA2 formed by irradiation with the first processing light EL11. Hereafter, the region where the interference region IA3 and the irradiation region RA2 overlap is also referred to as the superimposed region OA3. In the processing method using the processing optical system 15B, the entire processing region PA is scanned with this superimposed region OA3. That is, in the processing method using the processing optical system 15B, the interference region IA3 and the irradiation region RA2 are superimposed at one end of the processing region PA in the X-axis direction to form the superimposed region OA3, and the entire processing region PA is scanned by moving this superimposed region OA3 toward the other end in the X-axis direction.

[0069] As a result, in the machining method using the machining optical system 15B, the entire machining area PA on the surface of the workpiece W can be irradiated with interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd. In this case, in the machining method using the machining optical system 15B, the arranged interference fringes IS1 and IS2 are irradiated with the first machining light EL11 in superimposed light, so the workpiece W can be properly machined even in the areas where the dark areas ID of each interference fringe IS1 and IS2 are formed. Therefore, in the machining method using the machining optical system 15B, an ideally shaped riblet structure RB can be formed on the surface of the workpiece W in the machining area PA.

[0070] In this example, in the irradiation region RA2, interference fringes IS1 representing the fundamental frequency waveform Wb and IS2 representing the second-highest frequency waveform Wd are formed side by side, that is, the two interference fringes IS are formed in a tangent positional relationship in the Y-axis direction. However, interference fringes IS1 and IS2 may be formed in a separated positional relationship in the Y-axis direction, or they may be formed in a positional relationship where at least a part of them overlap, and are not limited to the example described above.

[0071] In the processing method using the processing optical system 15C, as shown in the upper panel, the irradiation area RA (hereinafter referred to as irradiation area RA3) of the first processing light EL11 from the third optical system 18 is made to be the same size as the processing area PA. Also, in the processing method using the processing optical system 15C, as shown in the middle panel, the interference area IA, which forms interference fringes IS by multiple second processing lights EL22 from the second optical system 17, is made to be smaller than the processing area PA. In detail, in the processing method using the processing optical system 15C, similar to the processing method using the processing optical system 15A, the interference area IA is rectangular in shape, with the same size as the processing area PA in the Y-axis direction, but smaller than the processing area PA in the X-axis direction. Furthermore, in the processing method using the processing optical system 15C, similar to the processing method using the processing optical system 15A, interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd are formed in the interference area IA at different timings (times). In other words, in the processing method using the processing optical system 15C, similar to the processing method using the processing optical system 15A, an interference region IA1 is formed in which interference fringes IS1 showing the fundamental frequency waveform Wb are formed, and an interference region IA2 is formed in which interference fringes IS2 showing the second frequency waveform Wd are formed.

[0072] In the processing method using the processing optical system 15C, as shown in the lower panel, the first processing light EL11 is irradiated onto the processing area PA, where interference region IA1 is formed by interference fringe IS1 of the fundamental frequency waveform Wb and interference region IA2 is formed by interference fringe IS2 of the double frequency waveform Wd, to form the irradiation area RA3. Here, the irradiation area RA3 is equal in size to the processing area PA, while interference regions IA1 and IA2 are smaller than the processing area PA. Therefore, in the irradiation area RA3 (processing area PA), the areas where interference regions IA1 and IA2 are formed become superimposed regions OA where the first processing light EL11 and multiple second processing light EL22 (interference fringes IS1, IS2) are superimposed. Then, in the processing method using the processing optical system 15C, the entire processing area PA is scanned with interference regions IA1 and IA2 while the irradiation area RA3 is formed. In other words, in the machining method using the machining optical system 15C, an irradiation region RA3 is formed in the machining region PA, and an interference region IA1 is formed at one end of the machining region PA in the X-axis direction. By moving the interference region IA1 toward the other end in the X-axis direction, the entire area of ​​the machining region PA is scanned, and a superimposed region OA4 is formed over the entire area of ​​the machining region PA. Subsequently, in the machining method using the machining optical system 15C, an irradiation region RA3 is formed in the machining region PA, and an interference region IA2 is formed at one end of the machining region PA in the X-axis direction. By moving the interference region IA2 toward the other end in the X-axis direction, the entire area of ​​the machining region PA is scanned, and a superimposed region OA5 is formed over the entire area of ​​the machining region PA.

[0073] As a result, in the machining method using the machining optical system 15C, the entire machining area PA on the surface of the workpiece W can be irradiated with interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd. In this case, since the entire machining area PA is irradiated with the first machining light EL11 in the machining method using the machining optical system 15C, the interference fringes IS1 and IS2 and the first machining light EL11 are reliably superimposed and irradiated, and the workpiece W can be appropriately machined even in the areas where the dark areas ID of the respective interference fringes IS1 and IS2 are formed. For this reason, in the machining method using the machining optical system 15C, an ideally shaped riblet structure RB can be formed on the surface of the workpiece W in the machining area PA.

[0074] In the processing method using the processing optical system 15D, as shown in the upper panel, the irradiation area RA3 of the first processing light EL11 from the third optical system 18 is made to be equal in size to the processing area PA, similar to the processing method using the processing optical system 15C. Also, in the processing method using the processing optical system 15D, as shown in the middle panel, the interference area IA3 in which interference fringes IS are formed by multiple second processing lights EL22 from the second optical system 17 is made to be smaller than the processing area PA, similar to the processing method using the processing optical system 15B. Specifically, in the processing method using the processing optical system 15C, the interference area IA3 is rectangular in shape, with the same size as the processing area PA in the Y-axis direction and smaller in size than the processing area PA in the X-axis direction. Then, in the processing method using the processing optical system 15D, similar to the processing method using the processing optical system 15B, interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd are formed in parallel in the X-axis direction within the interference area IA3. In other words, in the machining method using the machining optical system 15D, interference fringes IS2 of a double-frequency waveform Wd are formed on one end of the interference region IA3 in the X-axis direction, and interference fringes IS1 of a fundamental-frequency waveform Wb are formed side by side on the other end in the X-axis direction.

[0075] In the processing method using the processing optical system 15D, as shown in the lower panel, the first processing light EL11 is irradiated onto the processing area PA, where an interference region IA3 is formed, in which interference fringes IS1 and IS2 of two types of frequency waveforms Wb and Wd are arranged side by side, to form an irradiation region RA3. Here, the irradiation region RA3 is equal in size to the processing area PA, and the interference region IA3 is smaller than the processing area PA. Therefore, in the irradiation region RA3 (processing area PA), the area where the interference region IA3 is formed becomes a superimposed region OA6 in which the first processing light EL11 and multiple second processing lights EL22 (interference fringes IS1 and IS2) are superimposed. Then, in the processing method using the processing optical system 15D, the entire processing area PA is scanned with the interference region IA3 while the irradiation region RA3 is formed. In other words, in the machining method using the machining optical system 15D, an irradiation region RA3 is formed in the machining region PA, an interference region IA3 is formed at one end of the machining region PA in the X-axis direction, and by moving the interference region IA3 toward the other end in the X-axis direction, the entire area of ​​the machining region PA is scanned, and an overlay region OA6 is formed over the entire area of ​​the machining region PA.

[0076] As a result, in the machining method using the machining optical system 15D, the entire machining area PA on the surface of the workpiece W can be irradiated with interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd. In this case, since the entire machining area PA is irradiated with the first machining light EL11 in the machining method using the machining optical system 15D, the interference fringes IS1 and IS2 and the first machining light EL11 are irradiated in overlapping order, and the workpiece W can be properly machined even in the areas where the dark area ID of each interference fringe IS is formed. For this reason, in the machining method using the machining optical system 15D, an ideally shaped riblet structure RB can be formed on the surface of the workpiece W in the machining area PA.

[0077] In the processing method using the processing optical system 15E, as shown in the upper panel, the irradiation area RA3 of the first processing light EL11 from the third optical system 18 is made to be equal in size to the processing area PA, similar to the processing methods using the processing optical systems 15C and 15D. Furthermore, in the processing method using the processing optical system 15E, as shown in the middle panel, the interference area IA, which forms interference fringes IS by multiple second processing lights EL22 from the second optical system 17, is made to be approximately equal in size to the irradiation area RA3, i.e., the processing area PA. Therefore, in the processing method using the processing optical system 15E, interference fringes IS can be formed over the entire processing area PA without the second optical system 17 moving the interference area IA. In other words, in the processing method using the processing optical system 15E, the positional relationship between the irradiation area RA3 from the third optical system 18 and the interference area IA formed by the second optical system 17 remains constant.

[0078] Then, in the processing method using the processing optical system 15E, as shown in the lower panel, interference fringe IS1 (hereinafter referred to as interference region IA4) showing the fundamental frequency waveform Wb and interference fringe IS2 (hereinafter referred to as interference region IA5) showing the double frequency waveform Wd are formed in the interference region IA at different timings (times). At this time, in the processing method using the processing optical system 15E, interference region IA4, where interference fringe IS1 showing the fundamental frequency waveform Wb is formed, and irradiation region RA3, which is formed by irradiation with the first processing light EL11, are superimposed. Hereinafter, the region in which interference region IA4 and irradiation region RA3 are superimposed will also be called superimposed region OA7. Subsequently, in the processing method using the processing optical system 15E, interference region IA5, where interference fringe IS2 showing the double frequency waveform Wd is formed, is superimposed with irradiation region RA3, which is formed by irradiation with the first processing light EL11. Hereinafter, the region in which irradiation region RA3 is superimposed on interference region IA5 will also be called superimposed region OA8. Here, the irradiation region RA3, interference region IA4, and interference region IA5 are all equal in size to the processing region PA. Therefore, in the superposition regions OA6 and OA7, the first processing light EL11 and multiple second processing lights EL22 (interference fringes IS1, IS2) are superimposed over the entire processing region PA.

[0079] As a result, in the machining method using the machining optical system 15E, the entire machining area PA on the surface of the workpiece W can be irradiated with interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd. In this case, since the entire machining area PA is irradiated with the first machining light EL11 in the machining method using the machining optical system 15E, the interference fringes IS1 or IS2 and the first machining light EL11 are irradiated in superimposed, and the workpiece W can be properly machined even in the areas where the dark areas ID of each interference fringe IS1 and IS2 are formed. Therefore, in the machining method using the machining optical system 15E, an ideally shaped riblet structure RB can be formed on the surface of the workpiece W in the machining area PA.

[0080] Next, specific configuration examples of the five processing optical systems 15A, 15B, 15C, 15D, and 15E described above will be explained in order using Figures 12 to 21. Note that in Figures 12, 14, 16, 18, and 20, the processing light source 2 is omitted, and only the processing light EL0 from the processing light source 2 is shown.

[0081] (2-2) Processing optical system 15A Figure 12 shows the structure of the processing optical system 15A, and the processing light source 2 is not shown in Figure 12. As shown in Figure 12, the processing optical system 15A has a galvanometer mirror 21 and a collimating lens 22 to propagate the processing light EL0 from the processing light source 2 to the first optical system 16. As described above, the galvanometer mirror 21 is an interference fringe moving member that moves the position of the interference region IA relative to the second optical system 17 in a direction that intersects, typically orthogonal to, the optical axis of the second optical system 17, and reflects the processing light EL0 from the processing light source 2 toward the beam splitter 23. The galvanometer mirror 21 is designed so that its tilt can be changed in the rotational direction about a rotation axis extending in the Z-axis direction. By changing the tilt of the galvanometer mirror 21, the direction of reflection of the processing light EL0 toward the beam splitter 23 can be changed. The galvanometer mirror 21 is configured such that the range in which the direction of reflection of the processing light EL0 can be changed is within the range in which the branched second processing light EL2 can be incident on the splitting surface 25a of the special beam splitter 25, which will be described later. In other words, the galvanometer mirror 21 can change the direction in which the processing light EL0 travels within the range in which the second processing light EL2 can be incident on the splitting surface 25a. This galvanometer mirror 21 may be driven under the control of the control device 3, or under the control of another control device.

[0082] The collimating lens 22 makes the processing light EL0 from the processing light source 2, reflected by the galvanometer mirror 21, into collimated light (parallel light). In other words, the collimating lens 22 is considered to be the light that is diffused (diverged) from the processing light source 2 in this example, and makes that processing light EL0 into collimated light (parallel light).

[0083] The processing optical system 15A has a beam splitter 23 as the first optical system 16 that splits the processing light EL0 from the processing light source 2 into a first processing light EL1 and a second processing light EL2. The processing light EL0, which has been collimated by the collimating lens 22, is incident on this beam splitter 23. The beam splitter 23 splits the processing light EL0 into a first processing light EL1 and a second processing light EL2. Specifically, the beam splitter 23 generates the first processing light EL1 which proceeds to the third optical system 18 by reflecting a portion of the processing light EL0, and generates the second processing light EL2 which proceeds to the second optical system 17 by passing another portion of the processing light EL0 through it. Alternatively, the beam splitter 23 may generate the first processing light EL1 by transmitting a portion of the processing light EL0 and generate the second processing light EL2 by reflecting the other portion of the processing light EL0. The beam splitter 23 may be an amplitude-splitting beam splitter or a polarization beam splitter. The beam splitter 23 propels the second processing light EL2, which it has passed through, to the second optical system 17 parallel to the Y-axis direction. For this reason, the galvanometer mirror 21, as an interference fringe moving member, is positioned in the optical path between the processing light source 2 and the beam splitter 23, which is the first optical system 16, positioned at a location where the processing light EL0 is split into the first processing light EL1 and the second processing light EL2. As described above, the galvanometer mirror 21 moves the position of the interference region IA relative to the second optical system 17 in a direction that intersects (orthogonal to) the optical axis of the second optical system 17.

[0084] In the example shown in Figure 12, the processing optical system 15A splits the processing light EL0 from the processing light source 2 into two before it enters the first optical system 16 (and its galvanometer mirror 21), using a diffractive optical element (DOE) or beam splitter (not shown). The processing optical system 15A then uses optical elements such as lenses to focus the two split processing light EL0 onto a single point or a narrow area close to it at different positions on the galvanometer mirror 21 (and its reflective surface). The first optical system 16 then reflects the two processing light EL0s at the galvanometer mirror 21 and passes them through the collimating lens 22. One of the split processing light EL0s is then reflected by the beam splitter 23 to become the first processing light EL1, while the other split processing light EL0 is passed through the beam splitter 23 to become the second processing light EL2. As a result, the processing optical system 15A can prevent the energy of the processing light EL0 from the processing light source 2 from concentrating in a narrow area on the beam splitter 23, thereby suppressing damage to the beam splitter 23 caused by the processing light EL0. Furthermore, since the processing optical system 15A focuses two processing light EL0 beams on one point or a narrow area close to it on the galvanometer mirror 21 (its reflective surface), it is easy to adjust the direction in which the processing light EL0 propagates by changing the tilt of the galvanometer mirror 21 to make the change easier and more appropriate.

[0085] Furthermore, the processing optical system 15A, as a second optical system 17 that branches the second processing light EL2 from the first optical system 16 to generate multiple second processing light EL22, includes a first cylindrical lens 24, a special beam splitter 25, a second cylindrical lens 26, a first mirror 27, an optical deflection member 28, a second mirror 29, a third mirror 31, a third cylindrical lens 32, and a lens 33. Here, the second optical system 17 of the processing optical system 15A does not necessarily have the first cylindrical lens 24, the second cylindrical lens 26, the second mirror 29, and the lens 33. The first cylindrical lens 24 is an optical member that has a shape extending in the X-axis direction and refractive power only in the Z-axis direction, and is a convex lens in a cross section perpendicular to the X-axis direction. This first cylindrical lens 24 focuses the second processing light EL2 from the first optical system 16 in the Z-axis direction without changing it in the X-axis direction. Furthermore, the first cylindrical lens 24 has its rear focal point in the direction of propagation of the second processing light EL2 set near the dividing surface 25a of the special beam splitter 25, which will be described later. For this reason, the first cylindrical lens 24 makes the second processing light EL2 a linear light extending in the X-axis direction on the dividing surface 25a (see Figure 13).

[0086] The special beam splitter 25 divides the second processing light EL2, which has been converted into a linear beam of light extending in the X-axis direction by the first cylindrical lens 24, into multiple second processing light beams EL22. Therefore, the special beam splitter 25 functions as an optical splitting member that divides the second processing light EL2 into multiple second processing light beams EL22. In the following description, for the sake of explanation, an example will be described in which the special beam splitter 25 divides the second processing light EL2 into two second processing light beams EL22 (when shown individually, one will be referred to as second processing light beam EL221 and the other as second processing light beam EL222). The special beam splitter 25 also has the function of merging the two divided second processing light beams EL22 and directing both second processing light beams EL22 toward the lens 33, i.e., the workpiece W beyond it. Furthermore, the focusing position of the second processed light EL2 formed by the first cylindrical lens 24 may be slightly offset in the optical axis direction from the special beam splitter 25.

[0087] This special beam splitter 25 is a rectangular plate-like member, positioned at a 45-degree inclination with respect to the Y-axis, with a central axis extending in the X-axis direction. The special beam splitter 25 has a splitting surface 25a, a reflective surface 25b, and a passing surface 25c, each extending in the X-axis direction (see Figure 13). In the special beam splitter 25, the area near the central axis in the 45-degree inclination direction is the splitting surface 25a, the upper side in that inclination direction, which is the right side as seen in Figures 12 and 13 (the third cylindrical lens 32 side), is the reflective surface 25b, and the lower side in that inclination direction, which is the left side as seen in Figures 12 and 13 (the first cylindrical lens 24 side), is the passing surface 25c. Note that the inclination angle of the special beam splitter 25 is not limited to 45 degrees.

[0088] The splitting surface 25a splits the second processing light EL2, which has been converted into a linear light extending in the X-axis direction by the first cylindrical lens 24, into multiple second processing light EL22. This splitting surface 25a is composed of an amplitude-splitting beam splitter and a polarizing beam splitter, and generates the second processing light EL221 by reflecting a portion of the second processing light EL2, and generates the second processing light EL222 by allowing another portion of the second processing light EL2 to pass through. Here, the special beam splitter 25 is positioned at a 45-degree inclination with respect to the Y-axis direction, so the second processing light EL221 generated by reflection from the splitting surface 25a is propelled parallel to the Z-axis direction to the second cylindrical lens 26, and the second processing light EL222 generated by passing through another splitting surface 25a is propelled parallel to the Y-axis direction to the third cylindrical lens 32.

[0089] The reflective surface 25b reflects the second processed light EL221, which has been reflected by the third mirror 31 and focused by the third cylindrical lens 32, so that it propagates downward in the Z-axis direction (towards the lens 33), as will be described later. For this reason, the reflective surface 25b is configured such that the back surface of the special beam splitter 25 facing the third cylindrical lens 32 has optical properties that reflect light. This reflective surface 25b can be formed by partially depositing a material onto the upper end of the back surface of the special beam splitter 25. Note that the configuration and position of the reflective surface 25b can be set as appropriate, as long as it reflects the second processed light EL221 from the third cylindrical lens 32 toward the lens 33, and is not limited to this example.

[0090] The passing surface 25c transmits the second processed light EL222, which has been reflected by the first mirror 27 and focused by the second cylindrical lens 26, so that it proceeds downward in the Z-axis direction (towards the lens 33), as will be described later. Here, it is desirable that the passing surface 25c has no optical effect on the second processed light EL222 from the second cylindrical lens 26. For this reason, in this example, the passing surface 25c is nothing, that is, the portion corresponding to the passing surface 25c in the special beam splitter 25 is cut out. Note that the configuration and position of the passing surface 25c can be set as appropriate, as long as it allows the second processed light EL222 from the second cylindrical lens 26 to pass towards the lens 33, and is not limited to this example.

[0091] The second cylindrical lens 26 is an optical element that has a shape extending in the X-axis direction and refractive power only in the Y-axis direction, and is a convex lens in a cross section perpendicular to the X-axis direction. The front focal point of this second cylindrical lens 26 in the direction of propagation of the second processed light EL221 is set near the dividing surface 25a of the special beam splitter 25, and the second processed light EL221 is made into collimated light (parallel light) of a predetermined size in the X-axis and Y-axis directions. The second cylindrical lens 26 propels the collimated second processed light EL221 toward the first mirror 27 parallel to the Z-axis direction. Furthermore, the second cylindrical lens 26 focuses the second processed light EL222 reflected by the first mirror 27 in the Y-axis direction without changing it in the X-axis direction, and makes it a linear light extending in the X-axis direction on the passage surface 25c, as will be described later (see Figure 13).

[0092] The first mirror 27 is a plate-shaped member and is positioned with a central axis extending in the X-axis direction, at an inclination of 45 degrees with respect to the Z-axis direction. The first mirror 27 reflects the second processing light EL221 from the second cylindrical lens 26 and propagates it parallel to the Y-axis direction to the optical deflection member 28. The first mirror 27 also reflects the second processing light EL222 from the second mirror 29 that has passed through the optical deflection member 28 and propagates it to the second cylindrical lens 26.

[0093] The optical deflection member 28 is a member that changes (deflects) the direction of propagation of light (second processing light EL221, second processing light EL222) traveling between the first mirror 27 and the second mirror 29. The optical deflection member 28 is an optical member that has a shape extending in the X-axis direction and refractive power only in the Z-axis direction, and refracts the direction of propagation of light between the first mirror 27 and the second mirror 29 to either the upper or lower side in the Z-axis direction. In this example, the optical deflection member 28 has a trapezoidal (wedge-shaped) cross section perpendicular to the X-axis direction, where the thickness (size in the Y-axis direction) is smallest on the upper side in the Z-axis direction and increases towards the lower side in the Z-axis direction. Therefore, compared to a state where the optical deflection member 28 is not provided, the optical deflection member 28 refracts light from one of the first mirror 27 and the second mirror 29 downward in the Z-axis direction and directs it toward the other side of the first mirror 27 and the second mirror 29. This optical deflection member 28 can be positioned in the optical path between the first mirror 27 and the second mirror 29, and can also be removed from that optical path. In Embodiment 1, it is driven under the control of the control device 3.

[0094] The second mirror 29 is a plate-shaped member and is positioned at a reference position with a central axis extending in the X-axis direction, at a 45-degree inclination with respect to the Z-axis direction, and tilted around the central axis relative to this reference position. The second mirror 29 is in a conjugate positional relationship with the special beam splitter 25 (its dividing surface 25a). In this example, the second mirror 29 in Figure 12 is tilted counterclockwise (opposite to clockwise) around the central axis with respect to the reference position. Note that the direction of tilting from this reference position may also be clockwise, and is not limited to this example. The second mirror 29 reflects the second processed light EL221 that has passed through the optical deflection member 28 and propagates it to the third mirror 31, and also reflects the second processed light EL222 reflected by the third mirror 31 and propagates it to the optical deflection member 28.

[0095] The third mirror 31 is a plate-shaped member and is positioned at a 45-degree inclination with respect to the Z-axis direction, with a central axis extending in the X-axis direction as its center. The third mirror 31 reflects the second processing light EL221 reflected by the second mirror 29 and propagates it to the third cylindrical lens 32, and also reflects the second processing light EL222 that has passed through the third cylindrical lens 32 and propagates it to the second mirror 29 parallel to the Z-axis direction.

[0096] The third cylindrical lens 32 is an optical element that has a shape extending in the X-axis direction and refractive power only in the Z-axis direction, and is a convex lens in a cross section perpendicular to the X-axis direction. The front focal point of this third cylindrical lens 32 in the direction of propagation of the second processed light EL222 is set near the dividing surface 25a of the special beam splitter 25, and the second processed light EL222 is made into collimated light (parallel light) of a predetermined size in the X-axis and Y-axis directions. The third cylindrical lens 32 propagates the collimated second processed light EL222 parallel to the Y-axis direction toward the third mirror 31. Furthermore, the third cylindrical lens 32 focuses the second processed light EL221 reflected by the third mirror 31 in the Y-axis direction without changing it in the X-axis direction, and makes it a linear light extending in the X-axis direction on the reflective surface 25b as described later (see Figure 13).

[0097] Here, the focal positions of the second cylindrical lens 26 and the third cylindrical lens 32 may coincide. Then, with respect to the second processed light EL221, the splitting surface 25a and the reflective surface 25b become optically conjugate in the YZ plane due to the second cylindrical lens 26, the third cylindrical lens 32 and the optical deflection member 28. Also, with respect to the second processed light EL222, the splitting surface 25a and the passing surface 25c become optically conjugate in the YZ plane due to the second cylindrical lens 26, the third cylindrical lens 32 and the optical deflection member 28. Here, with respect to the second processed light EL221 incident on the special beam splitter 25, its incident position is shifted from the position of the splitting surface 25a to the position of the reflective surface 25b, and the incident position of the second processed light EL222 incident on the special beam splitter 25 is shifted from the position of the splitting surface 25a to the position of the passing surface 25c. In other words, the optical deflection member 28 has the function of spatially separating the optical paths of light from the special beam splitter 25 and light incident on the special beam splitter 25.

[0098] Lens 33 focuses the second processing light EL221, reflected by the reflective surface 25b as described later, and the second processing light EL222, transmitted through the through surface 25c as described later, onto the surface of the workpiece W in such a way that interference fringes IS are formed on the surface of the workpiece W. In other words, Lens 33 aligns the central axis of the optical path through which the second processing light EL221, reflected by the reflective surface 25b, travels with the central axis of the optical path through which the second processing light EL222, transmitted through the through surface 25c, travels on the surface of the workpiece W. To put it another way, Lens 33 focuses the second processing light EL221 and EL222, which are incident from positions away from their optical axes, and causes them to be obliquely incident on the surface of the workpiece W so that they intersect with each other on the surface of the workpiece W. As a result, interference fringes IS are formed on the surface of the workpiece W in a linear region extending in the Y-axis direction, forming an interference region IA.

[0099] Furthermore, the processing optical system 15A includes a fourth mirror 34, a fourth cylindrical lens 35, and a fifth mirror 36 as a third optical system 18 that propagates the first processing light EL1 from the first optical system 16 into the interference region IA. The fourth mirror 34 is a plate-shaped member and is positioned at a 45-degree inclination with respect to the Z-axis direction, with a central axis extending in the X-axis direction as its center. The fourth mirror 34 reflects the first processing light EL1 from the first optical system 16 and propagates it toward the fourth cylindrical lens 35 parallel to the Y-axis direction.

[0100] The fourth cylindrical lens 35 focuses the first processing light EL1 in the X-axis direction without changing its orientation in the Z-axis direction. The fourth cylindrical lens 35 is set so that the rear focal point in the direction of propagation of the first processing light EL1 is at a position where interference region IA is formed on the surface of the workpiece W after passing through the fifth mirror 36. Therefore, the fourth cylindrical lens 35 causes the first processing light EL1 to travel toward the fifth mirror 36 parallel to the Y-axis direction, while being converted into a linear beam of light extending in the Z-axis direction.

[0101] The fifth mirror 36 is a plate-shaped member and is positioned at a 45-degree inclination with respect to the Z-axis direction, with a central axis extending in the X-axis direction as its center. The fifth mirror 36 reflects the first processing light EL1 from the fourth cylindrical lens 35 and directs it toward the surface of the workpiece W. Therefore, the third optical system 18 directs the first processing light EL1 toward the surface of the workpiece W by reflecting it through the fourth mirror 34 and the fourth cylindrical lens 35 and then through the fifth mirror 36, resulting in the first processing light EL11. This first processing light EL11 is a linear light extending in the Z-axis direction by the fourth cylindrical lens 35, and is reflected toward the surface of the workpiece W by the fifth mirror 36, resulting in a linear light extending in the Y-axis direction.

[0102] Next, the operation of this processing optical system 15A will be explained. First, the processing light EL0 emitted from the processing light source 2 is reflected by the galvanometer mirror 21, then passes through the collimating lens 22, and is split into the first processing light EL1 and the second processing light EL2 by the beam splitter 23, which is the first optical system 16. Here, the first processing light EL1 and the second processing light EL2 are considered to be collimated light after passing through the collimating lens 22. The first processing light EL1 proceeds to the third optical system 18, and the second processing light EL2 proceeds to the second optical system 17.

[0103] In the second optical system 17, the second processed light EL2 is passed through the first cylindrical lens 24 and propagated as a linear light extending in the X-axis direction to the splitting surface 25a of the special beam splitter 25 (see Figure 13). Then, a portion of the second processed light EL2 is reflected at the splitting surface 25a toward the second cylindrical lens 26 to become the second processed light EL221, and another portion passes through (is transmitted through) the splitting surface 25a to become the second processed light EL222 toward the third cylindrical lens 32. The second processed light EL221 passes through the second cylindrical lens 26, is reflected by the first mirror 27, and then reflected by the second mirror 29 and the third mirror 31, passes through the third cylindrical lens 32, and propagates toward the special beam splitter 25. Furthermore, the second processed light EL222 passes through the third cylindrical lens 32, is reflected by the third mirror 31 and the second mirror 29, is then reflected by the first mirror 27, passes through the second cylindrical lens 26, and proceeds toward the special beam splitter 25. At this time, if an optical deflection member 28 is placed in the optical path between the first mirror 27 and the second mirror 29, the second processed light EL221 and the second processed light EL222 also pass through that optical deflection member 28.

[0104] Here, the special beam splitter 25 (its splitting surface 25a), the first mirror 27, and the third mirror 31 are all plate-shaped members and are inclined at a 45-degree angle with respect to the Z-axis direction, and the second mirror 29 is also a plate-shaped member and is inclined at a 45-degree angle with respect to the Z-axis direction as its reference position. For this reason, in the second optical system 17, the second processing light EL221 and the second processing light EL222 are basically propelled from the special beam splitter 25 in different rotational directions (clockwise and counterclockwise) and then return to the special beam splitter 25. Furthermore, in the second optical system 17, the second mirror 29 is tilted counterclockwise around its central axis with respect to its reference position in Figure 12. Therefore, the second processing light EL221 reflected by the second mirror 29 travels to a position shifted to the right at the third mirror 31 compared to when it is at the reference position, and is reflected there, causing it to travel to a position shifted upward at the special beam splitter 25, i.e., toward the reflection surface 25b (see Figure 13). Similarly, the second processing light EL222 reflected by the second mirror 29 travels to a position shifted downward at the first mirror 27 compared to when it is at the reference position, and is reflected there, causing it to travel to a position shifted downward at the special beam splitter 25, i.e., toward the passage surface 25c (see Figure 13). As a result, the second optical system 17 can create a spatial difference between the second processing light EL221 and the second processing light EL222 while allowing them to pass through essentially the same optical path. For this reason, the second optical system 17 can be said to constitute a square Sagnac optical system.

[0105] The second optical system 17 then reflects the second processing light EL221 at the reflective surface 25b and directs it toward the lens 33, and also transmits the second processing light EL222 through the passing surface 25c and directs it toward the lens 33. In this way, the second optical system 17, in the special beam splitter 25, reflects the second processing light EL221 reflected at the splitting surface 25a toward the lens 33 using the reflective surface 25b, and also transmits the second processing light EL222, which has passed through the splitting surface 25a, toward the lens 33 through the passing surface 25c. Therefore, the second optical system 17 can utilize the second processing light EL2 from the first optical system 16 with extremely high efficiency to generate the second processing light EL221 and the second processing light EL222 that irradiate the workpiece W from different incident directions.

[0106] Furthermore, the second optical system 17 focuses the second processing light EL221 and the second processing light EL222 onto the surface of the workpiece W by passing them through the lens 33, thereby forming interference fringes IS. Here, the second optical system 17 sets the angle of the second mirror 29 in consideration of the arrangement and optical performance of each optical component so that the angle between the second processing light EL221 and the second processing light EL222 after passing through the lens 33 forms interference fringes IS1 of the fundamental frequency waveform Wb. In other words, the second optical system 17 sets the arrangement and optical performance of each optical component and the angle of the second mirror 29 in accordance with the period of the interference fringes IS1 of the fundamental frequency waveform Wb. As a result, the second optical system 17 can form an interference region IA1 (see Figure 11) of interference fringes IS1 showing the fundamental frequency waveform Wb on the surface of the workpiece W.

[0107] Furthermore, in the second optical system 17, it is possible to place an optical deflection member 28 in the optical path between the first mirror 27 and the second mirror 29. The optical deflection member 28 refracts light from one of the first mirror 27 and the second mirror 29 downwards in the Z-axis direction, compared to the state without the optical deflection member 28, and directs it toward the other mirror 29. As a result, the second processing light EL221, by passing through the optical deflection member 28, travels to a position shifted downwards on the second mirror 29 compared to the case where it does not pass through the optical deflection member 28. Reflection there increases the amount of shift to the right on the third mirror 31, and reflection there increases the amount of shift upwards (outwards) on the reflective surface 25b of the special beam splitter 25 (see the dashed line symbol EL221 in Figure 13). Furthermore, when the second processed light EL222 passes through the optical deflection member 28, the amount of downward displacement at the first mirror 27 increases compared to when it does not pass through the optical deflection member 28. As a result of reflection there, the amount of downward (outward) displacement at the passage surface 25c of the special beam splitter 25 increases (see the dashed line indicated by the symbol EL222 in Figure 13).

[0108] Therefore, in the second optical system 17, by arranging the optical deflection member 28, the distance between the second processing light EL221 and the second processing light EL222 as they travel toward the lens 33 can be increased compared to when the optical deflection member 28 is not arranged. As a result, in the second optical system 17, by arranging the optical deflection member 28, the angle between the second processing light EL221 and the second processing light EL222 after they have passed through the lens 33 can be increased compared to when the optical deflection member 28 is not arranged. Therefore, in the second optical system 17, by arranging the optical deflection member 28, interference fringes IS with a smaller period can be formed on the surface of the workpiece W compared to when the optical deflection member 28 is not arranged. The second optical system 17 sets the shape (angle (degree of refraction (optical setting))) of the optical deflection member 28, taking into account the arrangement and optical performance of each optical component, so that the angle between the second processed light EL221 and the second processed light EL222 after passing through the lens 33 when the optical deflection member 28 is placed can form interference fringes IS2 of the double-frequency waveform Wd. In other words, the second optical system 17 sets the shape of the optical deflection member 28 along with the arrangement and optical performance of each optical component in accordance with the period of the interference fringes IS2 of the double-frequency waveform Wd. As a result, by placing the optical deflection member 28, the second optical system 17 can form an interference region IA2 (see Figure 11) of interference fringes IS2 showing the double-frequency waveform Wd on the surface of the workpiece W.

[0109] Furthermore, the period (pitch) P of the interference fringes IS1 and IS2 formed on the surface of the workpiece W is given by λ being the wavelength of the second processing light EL221 and EL222, n being the refractive index of the medium on the lens 33 side of the workpiece W with respect to wavelength λ, and 2θ being the intersection angle of the processing light EL221 and EL222 directed toward the workpiece W. P = λ / (2n × sinθ) It is given by.

[0110] Here, we consider the case where it is necessary to create a difference in amplitude between the fundamental frequency waveform Wb and the double frequency waveform Wd. In this case, it is necessary to set a similar difference in amplitude (energy amount) between the waveform showing the distribution of the amount of energy supplied to the workpiece W by the interference fringe IS1 representing the fundamental frequency waveform Wb, and the waveform showing the distribution of the amount of energy supplied to the workpiece W by the interference fringe IS2 representing the double frequency waveform Wd. This difference in amplitude (energy amount) can be set by changing the time it takes to overlap the interference region IA and the irradiation region RA to form the superposition region OA, that is, by changing the scanning speed by the galvanometer mirror 21. Furthermore, the above difference in amplitude (energy amount) can be set by changing the intensity of the processing light EL0 from the processing light source 2 when forming the interference region IA1 and the interference region IA2. The intensity of this processing light EL0 can be changed by changing the output of the processing light source 2 or by providing an optical element with a dimming effect in the optical path from the processing light source 2 to the first optical system 16.

[0111] Thus, in the second optical system 17, by changing the positions of the second processed light EL221 and the second processed light EL222 on the optical deflection member 28, the emission position and emission angle of the second processed light EL221 and the second processed light EL222 after passing through the lens 33 from the optical deflection member 28 can be changed. Furthermore, since the second optical system 17 forms interference fringes IS1 of the fundamental frequency waveform Wb by removing the optical deflection member 28 from the optical path, the intensity of the interference fringes IS1 can be ensured, and the interference fringes IS of the ideal waveform Wi can be appropriately formed in effect. This is because, generally, the interference fringes IS1 of the fundamental frequency waveform Wb often require a higher intensity than the interference fringes IS of the nth frequency waveform Wn. For this reason, if a higher intensity is required for the nth frequency waveform Wn, the second optical system 17 may form interference fringes IS1 of the nth frequency waveform Wn by removing the optical deflection member 28 from the optical path. Furthermore, when superimposing three or more n-frequency waveforms Wn, the second optical system 17 may be provided with a plurality of optical deflection members 28 having different shapes (angles of refraction) from each other, and it may be possible to individually place them in the optical path between the first mirror 27 and the second mirror 29 and to remove them from that optical path.

[0112] Furthermore, in the third optical system 18, the first processing light EL1 from the first optical system 16 is reflected by the fourth mirror 34, then passes through the fourth cylindrical lens 35, and proceeds to the fifth mirror 36 as a linear light extending in the Z-axis direction. Then, in the third optical system 18, it is reflected by the fifth mirror 36 to become the first processing light EL11, which irradiates the surface of the workpiece W as a linear light extending in the Y-axis direction at the position where interference regions IA (interference regions IA1 and IA2) are formed, thereby forming the irradiation region RA1 (see Figure 11). As a result, the processing optical system 15A, with the optical deflection member 28 removed in the second optical system 17, can superimpose the interference region IA1 and the irradiation region RA1 on the surface of the workpiece W to form an overlapping region OA1 (see Figure 11). Furthermore, by arranging the optical deflection member 28 in the second optical system 17 of the processing optical system 15A, the interference region IA2 and the irradiation region RA1 can be superimposed on the surface of the workpiece W to form an overlapping region OA2 (see Figure 11).

[0113] The processing optical system 15A sets the fluence of the first processing light EL11 in consideration of the arrangement and optical performance of each optical component in the first optical system 16, the second optical system 17, and the third optical system 18, so that the minimum fluence of the processing light in the superimposed region OA2 is a fluence that can process the workpiece W. In other words, the processing optical system 15A sets the branching ratio of the processing light EL0 from the processing light source 2 based on the arrangement and optical performance of each optical component in the first optical system 16, the second optical system 17, and the third optical system 18, so that the fluences of the interference fringes IS1 and IS2 are equal to or greater than the lower limit value TH_lowest of the fluence that can process the workpiece W.

[0114] The processing optical system 15A can move on the surface of the workpiece W while the superposition region OA1, i.e., the interference region IA1 and the irradiation region RA1 are superimposed, by driving the galvanometer mirror 21. Therefore, the processing optical system 15A determines the processing region PA as the region in which the superposition region OA1 can be moved by driving the galvanometer mirror 21. The processing optical system 15A scans the entire processing region PA with the superposition region OA1, which includes the fundamental frequency waveform Wb, by driving the galvanometer mirror 21 to move the superposition region OA2. Subsequently, with the optical deflection member 28 in place, the processing optical system 15A scans the entire processing region PA with the superposition region OA2, which includes the double frequency waveform Wd, by driving the galvanometer mirror 21 to move the superposition region OA2. As a result, the processing optical system 15A can irradiate the entire processing area PA on the surface of the workpiece W with interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd, with the first processing light EL11 superimposed. Therefore, the processing optical system 15A can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing area PA. Furthermore, by moving the stage 13, the processing optical system 15A can make any position on the surface of the workpiece W the processing area PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0115] (2-3) Processing optical system 15B Since the basic concept and configuration of this processing optical system 15B are the same as those of the processing optical system 15A described above, the same reference numerals are used for identical components, and detailed explanations are omitted. As shown in Figure 14, the processing optical system 15B has the same configuration for the first optical system 16 and the third optical system 18 as the processing optical system 15A. In the processing optical system 15B, the second optical system 17B, which branches the second processing light EL2 from the first optical system 16 to generate multiple second processing light EL22, is different from the second optical system 17 of the processing optical system 15A. In this second optical system 17B, compared to the second optical system 17 of the processing optical system 15A, there is no optical deflection member 28, and the second mirror 29B is different.

[0116] The second mirror 29B is formed by combining two plate-like members in the X-axis direction, with each member positioned at a 45-degree inclination with respect to the Z-axis direction, centered on a central axis extending in the X-axis direction. In this second mirror 29B, the far side of Figure 14 (negative side in the X-axis direction (-)) is designated as the first reflecting part 29Ba, and the near side of Figure 14 (positive side in the X-axis direction (+)) is designated as the second reflecting part 29Bb. For ease of understanding, in Figure 14, the first reflecting part 29Ba is shown with a dashed line, and the second reflecting part 29Bb is shown with a solid line. In this second mirror 29B, both the first reflecting part 29Ba and the second reflecting part 29Bb are tilted counterclockwise (opposite to clockwise) around the central axis with respect to the reference position in Figure 14. The direction of tilting from this reference position is not limited to this example; it may be clockwise as long as it is tilted in the same direction as the first reflector 29Ba and the second reflector 29Bb. The second mirror 29 reflects the second processed light EL221 from the first mirror 27 with both the first reflector 29Ba and the second reflector 29Bb, allowing it to proceed to the third mirror 31, and also reflects the second processed light EL222 from the third mirror 31 with both the first reflector 29Ba and the second reflector 29Bb, allowing it to proceed to the first mirror 27.

[0117] The first reflecting section 29Ba is angled such that the angle between the second processed light EL221 and the second processed light EL222 after passing through the lens 33 forms interference fringes IS1 of the fundamental frequency waveform Wb, taking into consideration the arrangement and optical performance of each optical component. In other words, the first reflecting section 29Ba is angled in accordance with the arrangement and optical performance of each optical component, in accordance with the period of interference fringes IS1 of the fundamental frequency waveform Wb. Similarly, the second reflecting section 29Bb is angled such that the angle between the second processed light EL221 and the second processed light EL222 after passing through the lens 33 forms interference fringes IS2 of the double frequency waveform Wd, taking into consideration the arrangement and optical performance of each optical component. In other words, the second reflecting section 29Bb is angled in accordance with the period of interference fringes IS2 of the double frequency waveform Wd, in accordance with the arrangement and optical performance of each optical component. Therefore, in the second mirror 29B, the second reflecting section 29Bb on the near side is tilted more with respect to the reference position than the first reflecting section 29Ba on the far side.

[0118] Here, the second processing light EL221 and the second processing light EL222 are formed after the second processing light EL2 (see Figure 15), which is a linear light extending in the X-axis direction on the dividing surface 25a, is divided and then collimated by the second cylindrical lens 26 and the third cylindrical lens 32 to a predetermined size in the X-axis direction and Y-axis direction (parallel light). Therefore, as the second processing light EL221 and the second processing light EL222 travel to the second mirror 29B with a predetermined size in the X-axis direction, a portion is reflected by the first reflector 29Ba and another portion is reflected by the second reflector 29Bb.

[0119] As a result, the second processing light EL221 is formed as a linear beam extending in the X-axis direction on the reflective surface 25b of the special beam splitter 25, on the upper side in the X-axis direction (corresponding to the far side in the X-axis direction in Figure 14), and as a linear beam extending in the X-axis direction at a position displaced to the right on the lower side in the X-axis direction (corresponding to the near side in the X-axis direction in Figure 14). Furthermore, the second processing light EL222 is formed as a linear beam extending in the X-axis direction on the passing surface 25c of the special beam splitter 25, on the upper side in the X-axis direction (corresponding to the far side in the X-axis direction in Figure 14), and as a linear beam extending in the X-axis direction at a position displaced to the left on the lower side in the X-axis direction (corresponding to the near side in the X-axis direction in Figure 14). Here, the difference in length between the upper and lower sides of the second processing light EL221 and the second processing light EL222 is the difference in time required to form the superposition region OA by overlapping the interference region IA and the irradiation region RA, and is set according to the difference in intensity (amplitude) between the fundamental frequency waveform Wb and the second frequency waveform Wd.

[0120] Therefore, the second processing light EL221 and the second processing light EL222 are configured such that a portion of them forms interference fringes IS1 of the fundamental frequency waveform Wb, and the other portion forms interference fringes IS2 of the double frequency waveform Wd. As a result, the second optical system 17B can irradiate the surface of the workpiece W with the second processing light EL221 and the second processing light EL222 by passing them through the lens 33, thereby forming an interference region IA3 on the surface of the workpiece W in which interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd are arranged in parallel (see Figure 11).

[0121] Next, the operation of the processing optical system 15B will be explained. First, the processing light EL0 emitted from the processing light source 2 is reflected by the galvanometer mirror 21, then passes through the collimating lens 22, and is split into the first processing light EL1 and the second processing light EL2 by the beam splitter 23, which is the first optical system 16. The first processing light EL1 proceeds to the third optical system 18, and the second processing light EL2 proceeds to the second optical system 17B. The second optical system 17B passes the second processing light EL2 through the first cylindrical lens 24 to make it a linear light extending in the X-axis direction, and the splitting surface 25a of the special beam splitter 25 splits it into the second processing light EL221 which proceeds to the second cylindrical lens 26, and the second processing light EL222 which proceeds to the third cylindrical lens 32. The second optical system 17B, similar to the second optical system 17B of the processing optical system 15A, advances the second processing light EL221 and the second processing light EL222 in different rotational directions (clockwise and counterclockwise) and then advances them from the special beam splitter 25 toward the lens 33.

[0122] The second optical system 17B then focuses the second processing light EL221 and the second processing light EL222 onto the surface of the workpiece W by passing them through the lens 33, thereby forming interference fringes IS. The second processing light EL221 and the second processing light EL222 are reflected by the first reflecting section 29Ba on the far side of Figure 14 and by the second reflecting section 29Bb on the near side of Figure 14. Therefore, the second optical system 17B irradiates the surface of the workpiece W with the second processing light EL221 and the second processing light EL222 after they have passed through the lens 33 at an angle that allows for the formation of interference fringes IS1 of the fundamental frequency waveform Wb on the far side of Figure 14 (negative side in the X-axis direction (-side)), and also irradiates the surface of the workpiece W at an angle that allows for the formation of interference fringes IS2 of the double frequency waveform Wd on the near side of Figure 14 (positive side in the X-axis direction (+side)). As a result, the second optical system 17B forms an interference region IA3 on the surface of the workpiece W, in which interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd are arranged side by side.

[0123] Furthermore, the third optical system 18 passes the first processing light EL1 from the first optical system 16 through the fourth cylindrical lens 35 to form a linear first processing light EL11 extending in the Z-axis direction. The third optical system 18 then irradiates the surface of the workpiece W with the first processing light EL11 as a linear light extending in the Y-axis direction at the position where the interference region IA3 is formed, thereby forming the irradiation region RA2. As a result, the processing optical system 15B, with the help of the second optical system 17B, can superimpose the interference region IA3 and the irradiation region RA2 on the surface of the workpiece W to form a superposition region OA3.

[0124] The processing optical system 15B can move on the surface of the workpiece W while the superposition region OA3, i.e., the interference region IA3 and the irradiation region RA3 are superimposed, by driving the galvanometer mirror 21. By driving the galvanometer mirror 21 to move the superposition region OA3, the processing optical system 15B scans the entire processing region PA with the superposition region OA3, which includes the fundamental frequency waveform Wb and the double frequency waveform Wd. As a result, the processing optical system 15B can irradiate the entire processing region PA on the surface of the workpiece W with interference fringes IS1 representing the fundamental frequency waveform Wb and interference fringes IS2 representing the double frequency waveform Wd, while the first processing light EL11 is superimposed. Therefore, the processing optical system 15B can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing region PA. Furthermore, by moving the stage 13, the processing optical system 15B can make any position on the surface of the workpiece W the processing region PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0125] (2-4) Processing optical system 15C Since the basic concept and configuration of this processing optical system 15C are the same as those of the processing optical system 15A described above, the same reference numerals are used for identical components, and detailed explanations are omitted. As shown in Figure 16, the processing optical system 15C has a second optical system 17 that is equivalent in configuration to that of the processing optical system 15A. Furthermore, the processing optical system 15C differs from the processing optical system 15A in that the first optical system 16C, which branches the processing light EL0 from the processing light source 2 into a first processing light EL1 and a second processing light EL2, and the third optical system 18C, which generates a first processing light EL11 from the first processing light EL1 and irradiates the workpiece W, are different. In addition, the configuration from the first optical system 16C to the second optical system 17 of the processing optical system 15C differs from that of the processing optical system 15A.

[0126] The processing optical system 15C differs from the processing optical system 15A in that the position (arrangement) of the first optical system 16C (beam splitter 23) relative to the galvanometer mirror 21 and collimating lens 22 has been changed, and a new lens 41 has been added. The beam splitter 23 as the first optical system 16C is positioned where the processing light EL0 from the processing light source 2 travels, and by reflecting a portion of the processing light EL0 it generates the first processing light EL1 that travels to the third optical system 18, and by allowing the other portion of the processing light EL0 to pass through it it generates the second processing light EL2 that travels to the lens 41.

[0127] The lens 41 focuses the second processing light EL2, which has passed through the beam splitter 23, onto the galvanometer mirror 21 (its reflective surface). In this example of the processing optical system 15C, the processing light EL0 from the processing light source 2 is assumed to be approximately collimated (parallel light), so the first processing light EL1 branched from it is assumed to be collimated (parallel light) of a predetermined size in the X-axis and Y-axis directions. The lens 41 sets the rear focal point in the direction of propagation of the second processing light EL2 near the galvanometer mirror 21 (its reflective surface), and focuses the second processing light EL2 onto the galvanometer mirror 21. The collimating lens 22 makes the second processing light EL2 reflected by the galvanometer mirror 21 into collimated light (parallel light). Furthermore, the second processed light EL2 focused by the lens 41 does not necessarily have to be completely focused onto the reflective surface of the galvanometer mirror 21, and the position of the focusing line of the second processed light EL2 by the lens 41 may be slightly off from the reflective surface of the galvanometer mirror 21 in the optical axis direction.

[0128] The second optical system 17 of the processing optical system 15C, similar to the processing optical system 15A, reflects the second processing light EL221 at the reflective surface 25b in the special beam splitter 25 and propagates it toward the lens 33, while also transmitting the second processing light EL222 through the passing surface 25c toward the lens 33. At this time, the second optical system 17 of the processing optical system 15C, similar to the processing optical system 15A, changes the distance between the second processing light EL221 and the second processing light EL222 in the special beam splitter 25 by switching between a state with the optical deflection member 28 removed and a state with the optical deflection member 28 in place (see Figure 17). Then, the second optical system 17 of the processing optical system 15C, similar to the processing optical system 15A, forms an interference region IA1 of interference fringe IS1 showing the fundamental frequency waveform Wb and an interference region IA2 of interference fringe IS2 showing the double frequency waveform Wd on the surface of the workpiece W.

[0129] Furthermore, the third optical system 18C differs from the third optical system 18 of the processing optical system 15A in that it lacks the fourth mirror 34 and the fourth cylindrical lens 35, and only has a fifth mirror 36. In the third optical system 18C, the first processing light EL1 from the first optical system 16C, i.e., the beam splitter 23, is reflected by the fifth mirror 36 and propagated to the surface of the workpiece W. Here, in the processing optical system 15C, the processing light EL0 from the processing light source 2 is assumed to be light that is approximately collimated (parallel light), so the first processing light EL1 branched from it is assumed to be light that is collimated (parallel light) of a predetermined size in the X-axis and Y-axis directions. Therefore, in the third optical system 18C, the first processing light EL11, which is directed toward the surface of the workpiece W after the first processing light EL1 is reflected by the fifth mirror 36, becomes light that is collimated of a predetermined size in the X-axis and Y-axis directions. The processing optical system 15C then irradiates the first processing light EL11 to form the irradiation region RA3, and makes the irradiation region RA3 equal in size to the processing region PA (see Figure 11). In other words, the processing optical system 15C sets the processing light EL0 from the processing light source 2 so that the irradiation region RA3 is equal in size to the processing region PA.

[0130] Next, the operation of the processing optical system 15C will be explained. First, when processing light EL0 is emitted from the processing light source 2, the first optical system 16C splits it into a first processing light EL1 and a second processing light EL2 using a beam splitter 23, and then the first processing light EL1 is sent to the third optical system 18C. The processing optical system 15C then collimates the second processing light EL2, which was branched in the first optical system 16C, using a collimating lens 22, and then sends it to the second optical system 17.

[0131] The second optical system 17 removes the optical deflection member 28 from the optical path between the first mirror 27 and the second mirror 29, thereby forming an interference region IA1 of interference fringes IS1 showing a fundamental frequency waveform Wb on the surface of the workpiece W. Furthermore, the second optical system 17 places the optical deflection member 28 in the optical path between the first mirror 27 and the second mirror 29, thereby forming an interference region IA2 of interference fringes IS2 showing a double frequency waveform Wd on the surface of the workpiece W.

[0132] Then, in the third optical system 18C, the first processing light EL1 from the first optical system 16C is reflected by the fifth mirror 36, and the first processing light EL11 of a predetermined size is irradiated onto the interference region IA (interference region IA1, interference region IA2) formed on the surface of the workpiece W in the X-axis and Y-axis directions to form an irradiation region RA3. The irradiation region RA3 is set to be the same size as the processing region PA. As a result, in the processing optical system 15C, with the optical deflection member 28 removed in the second optical system 17, the interference region IA1 and the irradiation region RA3 are superimposed on the surface of the workpiece W to form an overlapping region OA4 (see Figure 11). Also, in the processing optical system 15C, with the optical deflection member 28 placed in the second optical system 17, the interference region IA2 and the irradiation region RA3 are superimposed on the surface of the workpiece W to form an overlapping region OA5 (see Figure 11).

[0133] The processing optical system 15C then forms an irradiation region RA3 in the processing region PA and forms an interference region IA1 at one end of the processing region PA in the X-axis direction. The processing optical system 15C drives the galvanometer mirror 21 to move the interference region IA1 toward the other end in the X-axis direction, scanning the entire processing region PA and forming a superimposed region OA4 over the entire processing region PA (see Figure 11). Subsequently, the processing optical system 15C forms an irradiation region RA3 in the processing region PA and forms an interference region IA2 at one end of the processing region PA in the X-axis direction. Then, the processing optical system 15C drives the galvanometer mirror 21 to move the interference region IA2 toward the other end in the X-axis direction, scanning the entire processing region PA and forming a superimposed region OA5 over the entire processing region PA (see Figure 11). As a result, the processing optical system 15C can irradiate the entire processing area PA on the surface of the workpiece W with interference fringes IS1 of the fundamental frequency waveform Wb and interference fringes IS2 of the double frequency waveform Wd superimposed on the first processing light EL11. Therefore, the processing optical system 15C can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing area PA. Furthermore, by moving the stage 13, the processing optical system 15C can designate any position on the surface of the workpiece W as the processing area PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0134] (2-5) Processing optical system 15D As shown in Figure 18, this processing optical system 15D uses the first optical system 16C and the third optical system 18C of the processing optical system 15C, as well as the second optical system 17B of the processing optical system 15B. Therefore, the same reference numerals are used for parts with the same configuration, and detailed explanations are omitted.

[0135] The operation of the processing optical system 15D will now be explained. First, when processing light EL0 is emitted from the processing light source 2, the beam splitter 23 in the first optical system 16C splits it into a first processing light EL1 and a second processing light EL2, and then the first processing light EL1 is advanced to the third optical system 18C. The processing optical system 15D then collimates the second processing light EL2, which was branched in the first optical system 16C, using the collimating lens 22, and then advances it to the second optical system 17B.

[0136] In the second optical system 17B, the second processing light EL221 is made into a linear beam on the reflective surface 25b that extends in the X-axis direction and shifts in the Y-axis direction midway, while the second processing light EL222 is made into a linear beam on the passing surface 25c that extends in the X-axis direction and shifts in the Y-axis direction midway (see Figure 19). The second optical system 17B then irradiates the surface of the workpiece W with the second processing light EL221 and the second processing light EL222 by passing them through the lens 33, thereby forming an interference region IA3 on the surface of the workpiece W in which interference fringes IS1 showing the fundamental frequency waveform Wb and interference fringes IS2 showing the double frequency waveform Wd are arranged in parallel (see Figure 11).

[0137] Then, in the third optical system 18C, the first processing light EL1 from the first optical system 16C is reflected by the fifth mirror 36, and the first processing light EL11 of a predetermined size is irradiated in the X-axis and Y-axis directions, superimposed on the interference region IA3 formed on the surface of the workpiece W, thereby forming an irradiation region RA3 of the same size as the processing region PA. As a result, the processing optical system 15D, by the second optical system 17B, can superimpose the interference region IA3 and the irradiation region RA3 on the surface of the workpiece W to form a superimposed region OA6 (see Figure 11).

[0138] The processing optical system 15D then forms an irradiation area RA3 in the processing area PA and an interference area IA3 at one end of the processing area PA in the X-axis direction. The processing optical system 15D drives the galvanometer mirror 21 to move the interference area IA3 toward the other end in the X-axis direction, scanning the entire processing area PA and forming a superimposed area OA6 over the entire processing area PA. As a result, the processing optical system 15D can irradiate the entire processing area PA on the surface of the workpiece W with interference fringes IS1 of the fundamental frequency waveform Wb and interference fringes IS2 of the double frequency waveform Wd superimposed on the first processing light EL11. Therefore, the processing optical system 15D can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing area PA. Furthermore, by moving the stage 13, the processing optical system 15D can make any position on the surface of the workpiece W the processing area PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0139] (2-6) Processing optical system 15E As shown in Figure 20, this processing optical system 15E includes a first optical system 16E having the same basic concept and configuration as the first optical system 16C of the processing optical system 15C described above. In the following description, the same reference numerals are used for parts with the same configuration, and detailed explanations are omitted. Furthermore, the processing optical system 15E includes a second optical system 17E having the same basic concept and configuration as the second optical system 17 of the processing optical system 15A described above. In the following description, the same reference numerals are used for parts with the same configuration, and detailed explanations are omitted. Moreover, since the processing optical system 15E uses the third optical system 18C of the processing optical system 15C, the same reference numerals are used for parts with the same configuration, and detailed explanations are omitted.

[0140] The processing optical system 15E differs from the processing optical system 15C in that it does not have a galvanometer mirror 21, a collimating lens 22, and a lens 41, and instead has a newly added mirror 42. The beam splitter 23, which is the first optical system 16E, is positioned where the processing light EL0 from the processing light source 2 travels, and by reflecting a portion of the processing light EL0, it generates the first processing light EL1 that travels to the third optical system 18, and by allowing the other portion of the processing light EL0 to pass through, it generates the second processing light EL2 that travels to the mirror 42. The mirror 42 is a plate-shaped member and reflects the second processing light EL2 that has passed through the beam splitter 23 toward the second optical system 17E (and its first cylindrical lens 24).

[0141] The second optical system 17E of the processing optical system 15E differs from the second optical system 17 of the processing optical system 15A in that a fourth cylindrical lens 43 is newly provided in place of lens 33. The fourth cylindrical lens 43 converts the second processing light EL221 and second processing light EL222 (see Figure 21), which are linear light extending in the X-axis direction from the special beam splitter 25, into rectangular light having sides extending in the X-axis direction and sides extending in the Y-axis direction (see Figure 11). The front focal point of this fourth cylindrical lens 43 in the direction of propagation of the second processing light EL221 and second processing light EL222 is set near the special beam splitter 25 (its reflective surface). Therefore, the fourth cylindrical lens 43 makes the second processing light EL221 and second processing light EL222 on the surface of the workpiece W collimated light (parallel light) of a predetermined size in the X-axis direction and Y-axis direction.

[0142] The operation of the processing optical system 15E will now be explained. First, when processing light EL0 is emitted from the processing light source 2, the first optical system 16E splits it into a first processing light EL1 and a second processing light EL2 using a beam splitter 23, and then the first processing light EL1 is directed to the third optical system 18C. The processing optical system 15E also reflects the second processing light EL2, which was branched in the first optical system 16E, using a mirror 42 and directs it to the second optical system 17E.

[0143] The second optical system 17E irradiates the surface of the workpiece W with light of a predetermined magnitude in the X-axis and Y-axis directions by passing the second processing light EL221 and the second processing light EL222 from the special beam splitter 25 through the fourth cylindrical lens 43. The second optical system 17E then removes the optical deflection member 28 from the optical path between the first mirror 27 and the second mirror 29, thereby forming an interference region IA4 of interference fringes IS1 showing a fundamental frequency waveform Wb on the surface of the workpiece W (see Figure 11). The second optical system 17 also places the optical deflection member 28 in the optical path between the first mirror 27 and the second mirror 29, thereby forming an interference region IA5 of interference fringes IS2 showing a double frequency waveform Wd on the surface of the workpiece W (see Figure 11).

[0144] Then, in the third optical system 18C, the first processing light EL1 from the first optical system 16E is reflected by the fifth mirror 36, so that the first processing light EL11 is irradiated onto the interference region IA4 formed on the surface of the workpiece W, thereby forming an irradiation region RA3 equal in size to the processing region PA. As a result, the processing optical system 15E, with the optical deflection member 28 removed in the second optical system 17, superimposes the interference region IA4 and the irradiation region RA3 on the surface of the workpiece W to form a superimposed region OA7 equal in size to the processing region PA (see Figure 11). Also, in the third optical system 18C, the first processing light EL1 from the first optical system 16E is reflected by the fifth mirror 36, so that the first processing light EL11 is irradiated onto the interference region IA5 formed on the surface of the workpiece W, thereby forming an irradiation region RA3 equal in size to the processing region PA. As a result, the processing optical system 15E, with the optical deflection member 28 positioned in the second optical system 17, overlaps the interference region IA5 and the irradiation region RA3 on the surface of the workpiece W to form a superposition region OA8 (see Figure 11).

[0145] As a result, the processing optical system 15E can irradiate the entire processing area PA on the surface of the workpiece W with interference fringes IS1 of the fundamental frequency waveform Wb and interference fringes IS2 of the double frequency waveform Wd superimposed on the first processing light EL11. Therefore, the processing optical system 15E can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing area PA. Furthermore, by moving the stage 13, the processing optical system 15E can designate any position on the surface of the workpiece W as the processing area PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0146] (2-7) Modified optical system 15F as an example Next, a modified processing optical system 15F will be described as a variation of the processing optical system 15 described above. As shown in Figure 22, the basic concept and configuration of this processing optical system 15F are the same as those of the processing optical system 15A described above, so the same reference numerals are used for identical components, and detailed explanations are omitted. In the processing optical system 15F, the processing light EL0 from the processing light source 2 is considered to be highly directional, having components with two different polarization directions.

[0147] The processing optical system 15F differs from the processing optical system 15A in that it does not have a galvanometer mirror 21 and a collimating lens 22. The first optical system 16F of the processing optical system 15F splits the processing light EL0 from the processing light source 2 into a first processing light EL1 and a second processing light EL2 using a beam splitter 23. Specifically, the beam splitter 23 generates the first processing light EL1 which proceeds to the third optical system 18F by reflecting a portion of the processing light EL0, and generates the second processing light EL2 which proceeds to the second optical system 17F by allowing the other portion of the processing light EL0 to pass through.

[0148] Furthermore, the processing optical system 15F differs from the second optical system 17 of the processing optical system 15A in that the second optical system 17F, into which the second processing light EL2 from the first optical system 16F is incident, does not have a first cylindrical lens 24, a second cylindrical lens 26, an optical deflection member 28, a third cylindrical lens 32, and a lens 33. Also, the second optical system 17F of the processing optical system 15F differs from the second optical system 17 of the processing optical system 15A in that a first polarizing beam splitter 44 is provided in place of the special beam splitter 25, and a second polarizing beam splitter 45, a first lens 46, and a second lens 47 are newly provided.

[0149] The first polarizing beam splitter 44 splits the second processing light EL2 from the first optical system 16F into multiple second processing light beams EL22. For the sake of explanation, the following description will explain an example in which the first polarizing beam splitter 44 splits the second processing light EL2 into two second processing light beams EL22 (when shown individually, one will be referred to as second processing light beam EL221 and the other as second processing light beam EL222). The first polarizing beam splitter 44 also has the function of merging the two split second processing light beams EL22 and directing both second processing light beams EL22 toward the second polarizing beam splitter 45.

[0150] The first polarizing beam splitter 44 is a rectangular plate-shaped polarizing beam splitter, and is positioned at a 45-degree inclination with respect to the Y-axis direction, with a central axis extending in the X-axis direction as its center. Therefore, the first polarizing beam splitter 44 has a first polarization splitting surface 44a that is inclined at a 45-degree inclination with respect to the Y-axis direction. The first polarizing beam splitter 44 generates a second processed light EL221 by reflecting a portion of the second processed light EL2 from the first optical system 16F, and generates a second processed light EL222 by allowing the remainder of the second processed light EL2 to pass through. At this time, the first polarizing beam splitter 44 reflects one of the p-polarized component and the s-polarized component at its first polarization splitting surface 44a, while allowing the other of the p-polarized component and the s-polarized component to pass through. Therefore, the second processing light EL2 from the first optical system 16F is configured to contain both p-polarized and s-polarized components in the first polarizing beam splitter 44 at the time it is incident on the first polarizing beam splitter 44. Thus, the processing light EL0 from the processing light source 2 is configured with two different polarization directions so that it contains both p-polarized and s-polarized components in the first polarizing beam splitter 44 at the time of incidence. Here, the first polarizing beam splitter 44 is positioned at a 45-degree inclination with respect to the Y-axis direction, so the second processing light EL221 generated by reflection is directed to the first mirror 27 parallel to the Z-axis direction, and the second processing light EL222 generated by passing through it is directed to the third mirror 31 parallel to the Y-axis direction.

[0151] In the second optical system 17F, the relationship between the first mirror 27, the second mirror 29, and the third mirror 31 with respect to the first polarizing beam splitter 44 is the same as that of the second optical system 17 of the processing optical system 15A, except that the first cylindrical lens 24, the second cylindrical lens 26, the optical deflection member 28, and the third cylindrical lens 32 are not provided. Therefore, in the second optical system 17F, the second processing light EL221 and the second processing light EL222 are basically propelled from the first polarizing beam splitter 44 in different rotational directions (clockwise and counterclockwise) and then returned to the first polarizing beam splitter 44. Here, in the second optical system 17F, the second mirror 29 is positioned at an angle from the reference position (plane), so that the second processing light EL221 and the second processing light EL222 pass through essentially the same optical path, while the emission angles of the second processing light EL221 and the second processing light EL222 are in different directions. The second optical system 17F reflects the second processing light EL221 at the first polarizing beam splitter 44 and directs it toward the second polarizing beam splitter 45, while transmitting the second processing light EL222 through the first polarizing beam splitter 44 and directing it toward the second polarizing beam splitter 45. The second processing light EL221 is linearly polarized in one of the p-polarization and s-polarization directions (first polarization direction) at the first polarizing beam splitter 44, and the second processing light EL222 is linearly polarized in the other of the p-polarization and s-polarization directions (second polarization direction) at the first polarizing beam splitter 44.

[0152] Therefore, the first polarizing beam splitter 44 emits the second processing light EL221 in the first polarization direction and the second processing light EL222 in the second polarization direction such that at least one of the emission angle and emission position is different. Thus, in the second optical system 17F, the first polarizing beam splitter 44, the first mirror 27, the second mirror 29, and the third mirror 31 form an upstream optical system that emits the second processing light EL221 in the first polarization direction and the second processing light EL222 in the second polarization direction such that at least one of the emission angle and emission position is different.

[0153] The second polarizing beam splitter 45 is constructed by combining a cubic polarizing beam splitter section 45a with an orthogonal triangular prism section 45b that is continuous with one of its faces. The polarizing beam splitter section 45a has a second polarization splitting surface 45c that is inclined at 45 degrees with respect to the Y-axis direction. This second polarization splitting surface 45c reflects one of the p-polarized component and the s-polarized component on the second polarization splitting surface 45c, while allowing the other of the p-polarized component and the s-polarized component to pass through. The second polarizing beam splitter 45 is positioned rotated around a central axis extending in the Y-axis direction relative to the first polarizing beam splitter 44, such that the second polarization splitting surface 45c is non-parallel to the first polarization splitting surface 44a of the first polarizing beam splitter 44 (they have different plane directions). Here, the plane direction may be the normal direction of the plane. In this modified version, the second polarization beam splitter 45 has a second polarization splitting surface 45c that is at a 45-degree angle with respect to the first polarization splitting surface 44a when viewed in the rotational direction about the central axis extending in the Y-axis direction. Therefore, while the plane perpendicular to the first polarization splitting surface 44a includes the X-axis direction (is considered parallel), the plane perpendicular to the second polarization splitting surface 45c is considered to make a predetermined angle (45 degrees in this modified version) with respect to the X-axis direction.

[0154] As described above, the second polarization splitting surface 45c is positioned rotated around a central axis extending in the Y-axis direction relative to the first polarization splitting surface 44a, so it can split the second processed light EL221, which is linearly polarized in the first polarization direction, and the second processed light EL222, which is linearly polarized in the second polarization direction, from the first polarization beam splitter 44. That is, the second polarization splitting surface 45c allows a portion of the second processed light EL221, which is linearly polarized in the first polarization direction, to pass through to become the second processed light EL221 in the third polarization direction, and reflects the remainder of the second processed light EL221 to become the second processed light EL221 in the fourth polarization direction. Furthermore, the second polarization splitting surface 45c allows a portion of the second processed light EL222, which is linearly polarized in the second polarization direction, to pass through to become the second processed light EL222 in the third polarization direction, and reflects the remainder of the second processed light EL222 to become the second processed light EL222 in the fourth polarization direction. As a result, the second polarization splitting surface 45c allows the second processed light EL221 and the second processed light EL222 in the third polarization direction that have passed through to interfere with each other, and also allows the reflected second processed light EL221 and the second processed light EL222 in the fourth polarization direction to interfere with each other. The second polarization beam splitter 45 then emits the second processed light EL221 and the second processed light EL222, which are in the third polarization direction, downwards in the Y-axis direction of the second polarization splitting surface 45c and propels them toward the first lens 46.

[0155] The orthogonal triangular prism portion 45b has a reflective surface 45d provided in the direction of propagation of the second processed light EL221 and the second processed light EL222 in the fourth polarization direction, which are reflected by the second polarization splitting surface 45c. In this modified example, the reflective surface 45d is parallel to the second polarization splitting surface 45c. Therefore, the reflective surface 45d, like the second polarization splitting surface 45c, has orthogonal planes that form a predetermined angle (45 degrees in this modified example) with respect to the X-axis direction. The reflective surface 45d reflects the second processed light EL221 and the second processed light EL222, which are in the fourth polarization direction, downwards in the Y-axis direction of the reflective surface 45d, and propagates them toward the first lens 46.

[0156] The first lens 46 is provided in conjunction with the second lens 47 in the Y-axis direction. The first lens 46 works in cooperation with the second lens 47 to irradiate the first position P1 on the surface of the workpiece W with the second processing light EL221 and the second processing light EL222 in the third polarization direction to form the first interference fringe (interference fringe IS of interference region IA6 (see Figure 23)). The first lens 46 also works in cooperation with the second lens 47 to irradiate the second processing light EL221 and the second processing light EL222 in the fourth polarization direction on the surface of the workpiece W to form the second interference fringe (interference fringe IS of interference region IA7 (see Figure 23)). The first lens 46 then works in cooperation with the second lens 47 to adjust the size of the interference region IA6 at the first position P1 and the size of the interference region IA7 at the second position P2 on the surface of the workpiece W. In other words, the first lens 46 works in cooperation with the second lens 47 to adjust the size of the first interference fringe (interference fringe IS in interference region IA6) formed by the second processed light EL221 and EL222 in the third polarization direction, and the second interference fringe (interference fringe IS in interference region IA7) formed by the second processed light EL221 and EL222 in the fourth polarization direction. This adjustment of size includes adjusting the size of the interference regions IA6 and IA7 on the surface of the workpiece W, as well as adjusting the period of the interference fringe IS on the surface of the workpiece W. For this reason, the first lens 46 and the second lens 47 can be said to constitute an afocal optical system.

[0157] For the sake of simplicity in the illustration, Figure 22 shows the first lens 46 and the second lens 47 as single lenses each, but the first lens 46 and the second lens 47 may each be composed of multiple lenses. Therefore, the first lens 46 and the second lens 47 may be referred to as the first lens group 46 and the second lens group 47, respectively. In addition, reflective members or diffractive optical elements may be used instead of or in addition to lenses. Therefore, the first lens 46 and the second lens 47 may be referred to as the first optical element group 46 and the second optical element group 47, respectively.

[0158] The second optical system 17F aligns the fringe pitch direction of the first interference fringe (interference fringe IS in interference region IA6) and the fringe pitch direction of the second interference fringe (interference fringe IS in interference region IA7) to the same direction or to be parallel to each other. Furthermore, the second optical system 17F equates the fringe pitch of the first interference fringe (interference fringe IS in interference region IA6) with the fringe pitch of the second interference fringe (interference fringe IS in interference region IA7). The second optical system 17F also aligns the phase of brightness and darkness of the interference fringe IS in interference region IA6 with that of the interference fringe IS in interference region IA7. Here, aligning the phases of brightness and darkness of both interference fringe IS means that the positions of brightness and darkness coincide when the interference fringe IS in interference region IA6 is virtually expanded and the interference fringe IS in interference region IA7 is virtually expanded; that is, they form similar patterns of brightness and darkness. In other words, the alignment of the light and dark phases of both interference fringes IS means that the phases of the interference fringes IS formed by virtually expanding interference region IA6 and the interference fringes IS formed by virtually expanding interference region IA7 are aligned.

[0159] Therefore, the second polarizing beam splitter 45 splits the second processed light EL221 in the first polarization direction into the second processed light EL221 in the third polarization direction and the second processed light EL221 in the fourth polarization direction, and also splits the second processed light EL222 in the second polarization direction into the second processed light EL222 in the third polarization direction and the second processed light EL222 in the fourth polarization direction. As a result, in the second optical system 17F, the second polarizing beam splitter 45, the first lens 46 and the second lens 47 form a first interference fringe (interference fringe IS in interference region IA6) at the first position P1 and a second interference fringe (interference fringe IS in interference region IA7) at the second position P2, becoming a downstream optical system.

[0160] Furthermore, the third optical system 18F differs from the third optical system 18 of the processing optical system 15A in that it has a beam splitter 48 in place of the fourth cylindrical lens 35. In the third optical system 18F, the fourth mirror 34 reflects the first processing light EL1 from the first optical system 16F and directs it to the beam splitter 48.

[0161] When the first processing light EL1 from the first optical system 16F is incident on the beam splitter 48, it splits the first processing light EL1 into the first processing light EL111 and the first processing light EL112. Specifically, the beam splitter 48 generates the first processing light EL111 that travels to the surface of the workpiece W by reflecting a portion of the first processing light EL1, and generates the first processing light EL112 that travels to the fifth mirror 36 by allowing the other portion of the first processing light EL111 to pass through. The region irradiated by this first processing light EL111 is called the irradiation region RA4. In this modified beam splitter 48 (third optical system 18F), the first processing light EL111 is set to irradiate a first position P1 on the surface of the workpiece W where an interference region IA6 is formed, and the irradiation region RA4 and the interference region IA6 overlap (see Figure 23). This beam splitter 48 may be an amplitude-splitting type beam splitter or a polarizing beam splitter.

[0162] The fifth mirror 36 reflects the first processing light EL112 from the beam splitter 48 and directs it toward the surface of the workpiece W. In this modified example, the fifth mirror 36 (third optical system 18F) is set to illuminate the second position P2 on the surface of the workpiece W with the first processing light EL112, where the interference region IA7 is formed (see Figure 23). The region irradiated by this first processing light EL112 is referred to as the irradiation region RA5.

[0163] Therefore, the third optical system 18F splits the first processing light EL1 by the beam splitter 48 into a first processing light EL111 (irradiation area RA4) that irradiates the area on the surface of the workpiece W where interference area IA6 is formed, and a first processing light EL112 (irradiation area RA5) that irradiates the area on the surface of the workpiece W where interference area IA7 is formed. The processing optical system 15F can then form a superimposed area OA8 on the surface of the workpiece W by overlapping interference area IA6 and irradiation area RA4, and can also form a superimposed area OA9 by overlapping interference area IA7 and irradiation area RA5 (see Figure 23). Therefore, the processing optical system 15F designates the combined superimposed area OA8 and superimposed area OA9 as the processing area PA.

[0164] In this modified version, the processing optical system 15F sets the fluence of the first processing light EL111 and the first processing light EL112, taking into consideration the arrangement and optical performance of each optical component in the first optical system 16F, the second optical system 17F, and the third optical system 18F, so that the minimum fluence of the processing light in the superposition regions OA8 and OA9 is a fluence that can process the workpiece W. In other words, the processing optical system 15F sets the branching ratio in the beam splitter 23 of the first optical system 16F and the beam splitter 48 of the third optical system 18F, based on the arrangement and optical performance of each optical component in the first optical system 16F, the second optical system 17F, and the third optical system 18F, so that the fluence of the interference fringes IS between interference region IA7 and interference region IA8 is greater than or equal to the lower limit value TH_lowest of a fluence that can process the workpiece W.

[0165] Next, the operation of this processing optical system 15F will be explained. First, when processing light EL0 is emitted from the processing light source 2, the beam splitter 23 in the first optical system 16F splits it into the first processing light EL1 and the second processing light EL2. The first processing light EL1 proceeds to the third optical system 18F, and the second processing light EL2 proceeds to the second optical system 17F.

[0166] In the second optical system 17F, a portion of the second processed light EL2 is reflected by the first polarizing beam splitter 44 (first polarization splitting surface 44a) toward the first mirror 27 to become the second processed light EL221, and the remaining portion passes through the first polarizing beam splitter 44 (first polarization splitting surface 44a) toward the third mirror 31 to become the second processed light EL222. The second processed light EL221 is reflected by the first mirror 27, the second mirror 29, and the third mirror 31 and travels toward the first polarizing beam splitter 44. The second processed light EL222 is reflected by the third mirror 31, the second mirror 29, and the first mirror 27 and travels toward the first polarizing beam splitter 44.

[0167] Here, the first polarizing beam splitter 44, the first mirror 27, and the third mirror 31 are all plate-shaped members and are tilted at a 45-degree angle with respect to the Z-axis direction, and the second mirror 29 is also a plate-shaped member and is tilted at a 45-degree angle with respect to the Z-axis direction as its reference position. For this reason, in the second optical system 17F, the second processing light EL221 and the second processing light EL222 are basically propelled from the first polarizing beam splitter 44 in different rotational directions (clockwise and counterclockwise) and then return to the first polarizing beam splitter 44. In the second optical system 17F, the second mirror 29 is tilted counterclockwise around its central axis with respect to its reference position in Figure 22. For this reason, the second processing light EL221 reflected by the second mirror 29 travels to a position shifted to the right of the third mirror 31 compared to when it is at the reference position, and is reflected there, causing it to travel towards a position shifted upward on the first polarizing beam splitter 44. Furthermore, the second processed light EL222 reflected by the second mirror 29 travels to a position shifted downwards at the first mirror 27 compared to when it is at the reference position, and is reflected there, causing it to travel towards a position shifted downwards at the first polarizing beam splitter 44. As a result, in the second optical system 17F, while the second processed light EL221 and the second processed light EL222 pass through essentially the same optical path, a spatial difference in position can be created between the second processed light EL221 and the second processed light EL222. For this reason, the second optical system 17F (and its upstream optical system) can be said to constitute a square Sagnac optical system.

[0168] Then, the second optical system 17F reflects the second processed light EL221 at the first polarizing beam splitter 44 (first polarization splitting surface 44a) and directs it toward the second polarizing beam splitter 45, while simultaneously transmitting the second processed light EL222 through the first polarizing beam splitter 44 (first polarization splitting surface 44a) toward the second polarizing beam splitter 45. As a result, the second processed light EL221 is linearly polarized in the first polarization direction, and the second processed light EL222 is linearly polarized in the second polarization direction.

[0169] The second polarizing beam splitter 45, at the first polarization splitting surface 44a, allows a portion of the second processed light EL221 in the first polarization direction to pass through to become the second processed light EL221 in the third polarization direction, and also allows a portion of the second processed light EL222 in the second polarization direction to pass through to become the second processed light EL222 in the third polarization direction. Furthermore, at the first polarization splitting surface 44a, the second polarizing beam splitter 45 reflects the remainder of the second processed light EL221 in the first polarization direction to become the second processed light EL221 in the fourth polarization direction, and also reflects the remainder of the second processed light EL222 in the second polarization direction to become the second processed light EL222 in the fourth polarization direction. The second polarizing beam splitter 45 then directs the second processed light EL221 and the second processed light EL222 in the third polarization direction toward the first lens 46. Furthermore, the second polarizing beam splitter 45 reflects the second processing light EL221 and EL222 in the fourth polarization direction with the reflective surface 45d and directs them toward the first lens 46. Then, the first lens 46 and the second lens 47 form an interference fringe IS (interference region IA6) at the first position P1 on the surface of the workpiece W by the second processing light EL221 and EL222 in the third polarization direction. Also, the first lens 46 and the second lens 47 form an interference fringe IS (interference region IA7) at the second position P2 on the surface of the workpiece W by the second processing light EL221 and EL222 in the fourth polarization direction.

[0170] Furthermore, in the third optical system 18F, the first processing light EL1 from the first optical system 16F is reflected by the fourth mirror 34 and then split into the first processing light EL111 and the first processing light EL112 by the beam splitter 48. Then, in the third optical system 18F, the first processing light EL111 is directed from the beam splitter 48 to the surface of the workpiece W to form an irradiation region RA4 at the first position P1, and the first processing light EL112 is reflected by the fifth mirror 36 and directed to the surface of the workpiece W to form an irradiation region RA5 at the second position P2. As a result, the processing optical system 15F forms an overlapping region OA8 at the first position P1 by overlapping the interference region IA6 and the irradiation region RA4 on the surface of the workpiece W, and forms an overlapping region OA9 at the second position P2 by overlapping the interference region IA7 and the irradiation region RA5. Furthermore, in the processing optical system 15F, the phase of the brightness and darkness of the interference fringes IS in interference region IA6 is aligned with the phase of the brightness and darkness of the interference fringes IS in interference region IA7.

[0171] As a result, the processing optical system 15F can irradiate the entire processing area PA on the surface of the workpiece W with interference fringes IS created by superimposing the first processing light EL111 or the first processing light EL112. The processing optical system 15F sets the fluence of the first processing light EL111 and the first processing light EL112 so that the minimum fluence of the processing light in the superimposed areas OA8 and OA9 is sufficient to process the workpiece W. Therefore, the processing optical system 15F can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing area PA. Furthermore, by moving the stage 13, the processing optical system 15F can make any position on the surface of the workpiece W the processing area PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W. At this time, since the processing optical system 15F aligns the phase of brightness and darkness of the interference fringes IS between the superimposed areas OA8 and OA9, it can form similar riblet structures RB in both the superimposed areas OA8 and OA9. Therefore, by moving the processing optical system 15F in a direction in which the bright and dark areas extend relative to the workpiece W, the riblet structure RB can be formed more efficiently at any position on the surface of the workpiece W.

[0172] Furthermore, in the processing optical system 15F, the upstream optical system of the second optical system 17F emits a second processing light EL221 with linear polarization in the first polarization direction and a second processing light EL222 with linear polarization in the second polarization direction from the first polarization beam splitter 44 such that at least one of the emission angle and emission position is different. At this time, in the processing optical system 15F, the first polarization beam splitter 44 splits the second processing light EL2 into a second processing light EL221 with linear polarization in the first polarization direction and a second processing light EL222 with linear polarization in the second polarization direction. Therefore, since the processing optical system 15F splits the second processing light EL2 using the first polarization beam splitter 44, the loss of light during splitting can be significantly suppressed.

[0173] In addition, the processing optical system 15F has a positional relationship in which the first polarization splitting surface 44a of the first polarization beam splitter 44 and the second polarization splitting surface 45c of the second polarization beam splitter 45 are rotated around a central axis extending in the Y-axis direction. As a result, the second polarization splitting surface 45c can split the second processing light EL221 and the second processing light EL222, which have been split into p-polarized and s-polarized components on the first polarization splitting surface 44a, into p-polarized and s-polarized components on the second polarization splitting surface 45c. In the processing optical system 15F, the second polarization splitting surface 45c of the second polarization beam splitter 45 splits the second processing light EL221 in the first polarization direction into the second processing light EL221 in the third polarization direction and the second processing light EL221 in the fourth polarization direction, and also splits the second processing light EL222 in the second polarization direction into the second processing light EL222 in the third polarization direction and the second processing light EL222 in the fourth polarization direction. The processing optical system 15F allows the second processing light EL221 and the second processing light EL222 in the third polarization direction, which have passed through the first polarization splitting surface 44a, to pass through the first lens 46 and the second lens 47 to proceed to the first position P1 on the surface of the workpiece W. In addition, in the processing optical system 15F, a reflective surface 45d is provided in the reflection direction of the second polarization splitting surface 45c of the second polarization beam splitter 45. Then, in the processing optical system 15F, the second processing light EL221 and the second processing light EL222 in the fourth polarization direction, which have been reflected by the reflective surface 45d, are passed through the first lens 46 and the second lens 47 and propagated to the second position P2 on the surface of the workpiece W. In this way, the processing optical system 15F can align the polarization directions of the second processing light EL221 and the second processing light EL222 by passing them through the second polarization splitting surface 45c and by reflecting them at the second polarization splitting surface 45c. As a result, the processing optical system 15F is able to interfere with the polarization directions of the second processing light EL221 and the second processing light EL222, which would not normally interfere with each other due to their different polarization directions, by using the second polarization beam splitter 45. Then, the processing optical system 15F forms interference fringes IS with the second processing light EL221 and EL222 that have passed through in the third polarization direction, and also forms interference fringes IS with the second processing light EL221 and EL222 that have been reflected in the fourth polarization direction.Therefore, the processing optical system 15F can efficiently utilize the second processing light EL2 emitted toward the second optical system 17F to form interference fringes IS.

[0174] In the processing optical system 15F described above, interference fringes IS of a single frequency are formed. However, similar to the processing optical systems 15A, 15C, and 15E, one or more n-th frequency waveforms Wn may be superimposed on the fundamental frequency waveform Wb. In this case, the processing optical system 15F may be provided such that, for example, in the second optical system 17F, the optical deflection member 28 can be positioned in the optical path between the first mirror 27 and the second mirror 29, and can be removed from that optical path, similar to the second optical system 17 of the processing optical system 15A.

[0175] (2-8) Modified Optical System 15G Next, a modified processing optical system 15G, which is a modified version of the processing optical system 15 described above, will be explained. Since the basic concept and configuration of this processing optical system 15G are the same as those of the processing optical system 15A described above, the same reference numerals are used for parts with the same configuration, and detailed explanations are omitted.

[0176] The processing optical system 15G differs from the processing optical system 15A in that it does not have a galvanometer mirror 21 and a collimating lens 22, as shown in Figure 24. Therefore, the first optical system 16G splits the processing light EL0 from the processing light source 2 into a first processing light EL1 and a second processing light EL2 using a beam splitter 23. Specifically, the beam splitter 23 generates the first processing light EL1, which proceeds to the third optical system 18G, by allowing a portion of the processing light EL0 to pass through, and generates the second processing light EL2, which proceeds to the second optical system 17G, by reflecting the other portion of the processing light EL0.

[0177] Furthermore, in the processing optical system 15G, the second optical system 17G, into which the second processing light EL2 from the first optical system 16G is incident, has a different configuration from the second optical system 17 of the processing optical system 15A. This second optical system 17G has a beam splitter 51, a mirror 52, and a mirror 53. The beam splitter 51 is an optical splitting member that receives the second processing light EL2 from the first optical system 16G and splits the second processing light EL2 into multiple second processing light EL22. This beam splitter 51 generates multiple second processing light EL2 by splitting the second processing light EL2. In the following explanation, for the sake of clarity, an example will be described in which the beam splitter 51 splits the second processing light EL22 into two second processing light EL22 (when shown individually, one will be referred to as second processing light EL221 and the other as second processing light EL222).

[0178] The beam splitter 51 may be an amplitude-splitting beam splitter. In this case, a portion of the second processing light EL2 passes through the beam splitter 51 as the second processing light EL221. On the other hand, another portion of the second processing light EL2 is reflected by the beam splitter 51 as the second processing light EL222. The beam splitter 51 is not limited to an amplitude-splitting beam splitter, but may also be a polarizing beam splitter. In this case, a polarization control member such as a waveplate may be placed in one or more of the optical paths of the multiple processing lights branched by the polarizing beam splitter.

[0179] The second processing light EL221 that has passed through the beam splitter 51 is incident on the mirror 52. The mirror 52 reflects the second processing light EL221 toward the workpiece W. The mirror 52 reflects the second processing light EL221 so that it is incident on the workpiece W at a predetermined incident angle θ.

[0180] The second processing light EL222 reflected by the beam splitter 51 is incident on the mirror 53. The mirror 53 reflects the second processing light EL222 toward the workpiece W. The mirror 53 reflects the second processing light EL221 such that the second processing light EL222 is incident on the workpiece W from a different direction and at an incident angle θ than the second processing light EL221.

[0181] The second processing light EL221 reflected by mirror 52 and the second processing light EL222 reflected by mirror 53 are irradiated onto an interference region IA8 set on the workpiece W. The second optical system 17G sets the interference region IA8 to a predetermined size in the X-axis and Y-axis directions. As a result, interference light generated by the interference of the second processing light EL221 and the second processing light EL222 within the interference region IA8 forms interference fringes IS.

[0182] The third optical system 18G of the processing optical system 15G differs from the third optical system 18 of the processing optical system 15A in that it lacks the fourth mirror 34 and the fourth cylindrical lens 35, and only has a fifth mirror 36. In the third optical system 18G, the first processing light EL1 from the first optical system 16G, i.e., the beam splitter 23, is reflected by the fifth mirror 36 and propagated to the surface of the workpiece W as the first processing light EL11. This third optical system 18G directs the first processing light EL11 toward the surface of the workpiece W into light of a predetermined magnitude in the X-axis and Y-axis directions. The area irradiated by this first processing light EL11 is defined as the irradiation area RA6.

[0183] Next, the operation of this processing optical system 15G will be explained. First, when processing light EL0 is emitted from the processing light source 2, the beam splitter 23 in the first optical system 16G splits it into the first processing light EL1 and the second processing light EL2. Then, the first processing light EL1 is advanced to the third optical system 18G and the second processing light EL2 is advanced to the second optical system 17G.

[0184] The second optical system 17G splits the second processing light EL2 from the first optical system 16G into the second processing light EL221 and the second processing light EL222 using a beam splitter 51, and reflects them onto the surface of the workpiece W using mirrors 52 and 53. As a result, the second optical system 17G forms an interference region IA8 of interference fringes IS on the surface of the workpiece W. Then, the third optical system 18G reflects the first processing light EL1 from the first optical system 16G using a fifth mirror 36, superimposing it onto the interference region IA8 formed on the surface of the workpiece W, and irradiating it with a first processing light EL11 of a predetermined size in the X-axis and Y-axis directions to form an irradiation region RA6.

[0185] As a result, the processing optical system 15G superimposes the interference region IA8 and the irradiation region RA6 on the surface of the workpiece W to form a superimposed region OA10. Therefore, the processing optical system 15G makes the superimposed region OA10 the processing region PA. This allows the processing optical system 15G to superimpose the interference fringes IS onto the first processing light EL11 over the entire processing region PA on the surface of the workpiece W. The processing optical system 15G sets the fluence of the first processing light EL111 such that the minimum fluence of the processing light in the superimposed region OA10 is sufficient to process the workpiece W. Therefore, the processing optical system 15G can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing region PA. Furthermore, by moving the stage 13, the processing optical system 15G can make any position on the surface of the workpiece W the processing region PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0186] In the processing optical system 15G described above, a single-frequency interference fringe IS is formed. However, similar to the processing optical systems 15A, 15C, and 15E, one or more n-th frequency waveforms Wn may be superimposed on the fundamental frequency waveform Wb. In this case, the processing optical system 15G may be configured such that, for example, the angle of at least one of the mirrors 52 and 53 can be changed, or optical elements that refract light may be placed in the optical path from the first mirror 27 or the second mirror 29 to the surface of the workpiece W, or removed from that optical path. Furthermore, in the processing optical system 15G, the optical paths of the second processing light EL221 and EL222 traveling toward the workpiece W and the optical path of the first processing light EL11 traveling toward the workpiece W are located on the same plane. However, the optical path of the first processing light EL11 traveling toward the workpiece W does not have to be located on the same plane as the optical paths of the second processing light EL221 and EL222.

[0187] (2-9) Modified Optical System 15H Next, a modified processing optical system 15H, which is a modified version of the processing optical system 15 described above, will be explained. Since the basic concept and configuration of this processing optical system 15H are the same as those of the processing optical system 15A described above, the same reference numerals are used for parts with the same configuration, and detailed explanations are omitted.

[0188] The processing optical system 15H differs from the processing optical system 15A in that it does not have a galvanometer mirror 21 and a collimating lens 22, as shown in Figure 25. Therefore, the first optical system 16H of the processing optical system 15H splits the processing light EL0 from the processing light source 2 into a first processing light EL1 and a second processing light EL2 using a beam splitter 23. Specifically, the beam splitter 23 generates the first processing light EL1 which proceeds to the third optical system 18H by passing a portion of the processing light EL0 through it, and generates the second processing light EL2 which proceeds to the second optical system 17H by reflecting the other portion of the processing light EL0. In this example, the beam splitter 23 is configured to propagate the second processing light EL2, which was generated by passing the beam through it, parallel to the Y-axis direction.

[0189] Furthermore, in the processing optical system 15H, the second optical system 17H, into which the second processing light EL2 from the first optical system 16H is incident, has a different configuration from the second optical system 17 of the processing optical system 15A. This second optical system 17H includes a beam splitter 55, an optical deflection member 56, a first mirror 57, and a second mirror 58. The beam splitter 55 is an optical splitting member that receives the second processing light EL2 from the first optical system 16H and splits the second processing light EL2 into multiple second processing light EL22. This beam splitter 55 splits the second processing light EL2, which has been made into a linear light extending in the X-axis direction by the first cylindrical lens 24, into multiple second processing light EL22. Therefore, the beam splitter 55 functions as an optical splitting member that splits the second processing light EL2 into multiple second processing light EL22. In the following explanation, for the sake of clarity, we will describe an example in which the beam splitter 55 splits the second processing light EL2 into two second processing lights EL22 (when shown individually, one will be referred to as the second processing light EL221 and the other as the second processing light EL222). The beam splitter 55 also has the function of merging the two split second processing lights EL22 and directing both second processing lights EL22 toward the workpiece W.

[0190] This beam splitter 55 is a rectangular plate-shaped member and is positioned at a 45-degree inclination with respect to the Y-axis direction, with a central axis extending in the X-axis direction as its center. This beam splitter 55 is composed of an amplitude-splitting beam splitter and a polarizing beam splitter, and generates a second processed light EL221 by reflecting a portion of the second processed light EL2, and generates a second processed light EL222 by allowing another portion of the second processed light EL2 to pass through. Here, since the beam splitter 55 is positioned at a 45-degree inclination with respect to the Y-axis direction, the second processed light EL221 generated by reflection from the beam splitter 55 is propagated parallel to the Z-axis direction to the optical deflection member 56, and the second processed light EL222 generated by passing through the other beam splitter 55 is propagated parallel to the Y-axis direction to the second mirror 58.

[0191] The optical deflection member 56 is a member that changes (deflects) the direction of propagation of light (second processing light EL221, second processing light EL222) traveling between the beam splitter 55 and the first mirror 57. The optical deflection member 56 is an optical member that has a shape extending in the X-axis direction and has refractive power only in the Y-axis direction, and between the beam splitter 55 and the first mirror 57, it refracts the direction of propagation of light to either the right or left side in the Y-axis direction as shown in Figure 25. In this example, the optical deflection member 56 has a trapezoidal (wedge-shaped) cross section perpendicular to the X-axis direction, where the thickness (size in the Z-axis direction) is smallest on the right side in the Y-axis direction and increases towards the left side in the Y-axis direction. Therefore, compared to the state without the optical deflection member 56, the optical deflection member 56 refracts the light from one of the beam splitter 55 and the first mirror 57 to the left in the Y-axis direction and directs it toward the other of the beam splitter 55 and the first mirror 57.

[0192] The first mirror 57 is a plate-shaped member and is positioned with a predetermined inclination in the Z-axis direction, with a central axis extending in the X-axis direction as its center. This predetermined inclination is set to reflect the second processing light EL221, which has been reflected by the beam splitter 55 and passed through the optical deflection member 56, toward the second mirror 58, and also to reflect the second processing light EL222, which has been reflected by the second mirror 58, toward the optical deflection member 56. The first mirror 57 reflects the second processing light EL221 from the optical deflection member 56 and directs it toward the second mirror 58. In addition, the first mirror 57 reflects the second processing light EL222 from the second mirror 29 and directs it toward the optical deflection member 56.

[0193] The second mirror 58 is a plate-shaped member and is positioned with a predetermined inclination in the Z-axis direction that is different from that of the first mirror 57, with respect to its central axis extending in the X-axis direction. This predetermined inclination, which is different from that of the first mirror 57, is set to reflect the second processing light EL222 that has passed through the beam splitter 55 toward the first mirror 57, and to reflect the second processing light EL221 that has been reflected by the first mirror 57 toward the beam splitter 55.

[0194] The beam splitter 55 reflects the second processing light EL221 reflected by the second mirror 58 and propagates it to the surface of the workpiece W, and also propagates the second processing light EL222, which has been reflected by the first mirror 57 and passed through the optical deflection member 56, to the interference region IA9 on the surface of the workpiece W. The second optical system 17H sets the interference region IA9 to a predetermined size in the X-axis and Y-axis directions. As a result, interference light generated by the interference of the second processing light EL221 and the second processing light EL222 within the interference region IA9 forms interference fringes IS.

[0195] The third optical system 18H of the processing optical system 15H differs from the third optical system 18 of the processing optical system 15A in that it does not have a fourth cylindrical lens 35, but does have a fourth mirror 34 and a fifth mirror 36. In the third optical system 18H, the first processing light EL1 from the first optical system 16H, i.e., the beam splitter 23, is reflected by the fourth mirror 34 and then by the fifth mirror 36 to proceed to the surface of the workpiece W as the first processing light EL11. This third optical system 18H directs the first processing light EL11 toward the surface of the workpiece W into light of a predetermined magnitude in the X-axis and Y-axis directions. The area irradiated by this first processing light EL11 is called the irradiation area RA7.

[0196] Next, the operation of this processing optical system 15H will be explained. First, when processing light EL0 is emitted from the processing light source 2, the beam splitter 23 in the first optical system 16H splits it into the first processing light EL1 and the second processing light EL2. Then, the first processing light EL1 is directed to the third optical system 18H and the second processing light EL2 is directed to the second optical system 17H.

[0197] In the second optical system 17H, the second processed light EL2 is directed towards the beam splitter 55. Thereafter, a portion of the second processed light EL2 is reflected by the beam splitter 55 toward the optical deflection member 56 to become the second processed light EL221, and another portion passes through the beam splitter 55 toward the second mirror 58 to become the second processed light EL222. The second processed light EL221 passes through the optical deflection member 56, is reflected by the first mirror 57, and then reflected by the second mirror 58 before proceeding toward the beam splitter 55. The second processed light EL222 is reflected by the second mirror 58 and the first mirror 57, and then passes through the optical deflection member 56 toward the beam splitter 55.

[0198] In the second optical system 17H, the second processed light EL221, reflected by the beam splitter 55, the first mirror 57, and the second mirror 58, proceeds to the beam splitter 55, and the second processed light EL222, which has passed through the beam splitter 55 and been reflected by the second mirror 58 and the first mirror 57, also proceeds to the beam splitter 55. For this reason, in the second optical system 17H, the second processed light EL221 and the second processed light EL222 are basically made to proceed from the beam splitter 55 in different rotational directions (clockwise and counterclockwise) and return to the beam splitter 55. Furthermore, in the second optical system 17H, an optical deflection member 56 is provided between the beam splitter 55 and the first mirror 57.

[0199] Therefore, the second processing light EL221 reflected by the beam splitter 55 travels to a position shifted to the left of the first mirror 57 compared to when the optical deflection member 56 is not present, and is reflected there, causing it to travel to positions in the second mirror 58 and beam splitter 55 that reflect the shift at the first mirror 57. Also, the second processing light EL222 that has passed through the beam splitter 55 travels to the optical deflection member 56 after being reflected by the second mirror 58 and the first mirror 57, and is refracted there, causing it to travel towards the position shifted to the left of the beam splitter 55 compared to when the optical deflection member 56 is not present. In this way, the second optical system 17H has an optical deflection member 56 between the beam splitter 55 and the first mirror 57, which causes a bias in the direction of the optical path of the second processing light EL221 and the second processing light EL222 after they are refracted by the optical deflection member 56. Therefore, in the second optical system 17H, a difference is created in the effect on the second processed light EL221 and the second processed light EL222 due to refraction by the optical deflection member 56, that is, in the shift caused by passing through the optical deflection member 56. As a result, in the second optical system 17H, the second processed light EL221 and the second processed light EL222 can pass through essentially the same optical path, while the emission angles of the second processed light EL221 and the second processed light EL222 can be made to be in different directions. For this reason, the second optical system 17H can be said to constitute a triangular Sagnac optical system.

[0200] The second optical system 17H reflects the second processing light EL221 with the beam splitter 55 and directs it toward the surface of the workpiece W, while also passing the second processing light EL222 through the beam splitter 55 toward the surface of the workpiece W. The second optical system 17H focuses the second processing light EL221 and the second processing light EL222 onto the surface of the workpiece W, thereby forming interference fringes IS and creating an interference region IA9. The third optical system 18H reflects the first processing light EL1 from the first optical system 16H with the fourth mirror 34 and the fifth mirror 36, superimposing the first processing light EL11 of a predetermined size onto the interference region IA9 formed on the surface of the workpiece W, and irradiating it in the X-axis and Y-axis directions to form an irradiation region RA7.

[0201] As a result, the processing optical system 15H overlaps the interference region IA9 and the irradiation region RA7 on the surface of the workpiece W to form a superimposed region OA11. Therefore, the processing optical system 15H makes the superimposed region OA11 the processing region PA. This allows the processing optical system 15H to irradiate the entire processing region PA on the surface of the workpiece W with interference fringes IS superimposed on the first processing light EL11. The processing optical system 15H sets the fluence of the first processing light EL111 such that the minimum fluence of the processing light in the superimposed region OA11 is sufficient to process the workpiece W. Therefore, the processing optical system 15H can form a riblet structure RB of an ideal shape on the surface of the workpiece W in the processing region PA. Furthermore, by moving the stage 13, the processing optical system 15H can make any position on the surface of the workpiece W the processing region PA, and can form a riblet structure RB of an ideal shape at any position on the surface of the workpiece W.

[0202] In the processing optical system 15H described above, interference fringes IS of a single frequency are formed. However, similar to the processing optical systems 15A, 15C, and 15E, one or more n-th frequency waveforms Wn may be superimposed on the fundamental frequency waveform Wb. In this case, the processing optical system 15H may be provided, for example, in the second optical system 17H, as a second optical deflection member that refracts the direction of light propagation in either direction along the Y axis, similar to the optical deflection member 56, but with a different angle of refraction from the optical deflection member 56, and can be interchanged with the optical deflection member 56.

[0203] Therefore, the processing optical system 15, processing apparatus 1, and processing method according to this disclosure can form a riblet structure with an ideal shape.

[0204] The processing optical system, processing apparatus, and processing method of this disclosure have been described above based on examples. However, the specific configuration is not limited to each of the examples 1 described above, and changes or additions to the design are permitted as long as they do not deviate from the gist of the invention as claimed in each of the patent claims.

[0205] In the above description, the processing device 1 is equipped with a head drive system 12. However, the processing device 1 does not have to be equipped with a head drive system 12. In other words, the processing head 11 does not have to be movable. Also, in the above description, the processing device 1 is equipped with a stage drive system 14. However, the processing device 1 does not have to be equipped with a stage drive system 14. In other words, the stage 13 does not have to be movable. Or, the processing device 1 does not have to be equipped with a stage 13 at all.

[0206] The above description describes an example in which the processing apparatus 1 forms a riblet structure RB on a metallic workpiece W (base material), and an example in which the processing apparatus 1 forms a riblet structure RB on a film coated on the surface of the workpiece W. However, the processing performed by the processing apparatus 1 is not limited to the above examples. For example, the processing apparatus 1 may form a riblet structure RB on the surface of the workpiece W, and the surface of the workpiece W on which the riblet structure RB is formed may be coated with a film. For example, when the processing apparatus 1 forms a riblet structure RB on a film coated on the surface of the workpiece W, the film on which the riblet structure RB is formed may be further coated with another film. In either example, the riblet structure RB may be coated with a film. In this case, the thickness of the film may be determined so that the function of the riblet structure RB is not reduced by the film coating on the riblet structure RB. For example, if the riblet structure RB is embedded in the film, the function of the riblet structure RB may be reduced by the film, so the thickness of the film may be determined so that the riblet structure RB is not embedded in the film. To prevent the function of the riblet structure RB from being reduced by the coating film on the riblet structure RB, the film may be formed along the shape of the riblet structure RB (for example, along the convex structure 81 or groove structure 82).

[0207] In addition to or instead of removal processing, the processing apparatus 1 may perform additive processing to add a new structure to the workpiece W by irradiating the workpiece W with processing light EL. In this case, the processing apparatus 1 may form the above-described riblet structure RB on the surface of the workpiece W by performing additive processing. Alternatively, the processing apparatus 1 may perform machining to process the workpiece W by bringing a tool into contact with the workpiece W, in addition to or instead of at least one of removal processing and additive processing. In this case, the processing apparatus 1 may form the above-described riblet structure RB on the surface of the workpiece W by performing machining.

[0208] In the above description, the machining system SYS forms a riblet structure RB on the surface of the workpiece W that has the function of reducing the fluid's resistance. However, the machining system SYS may form a structure on the workpiece W that has a different function than reducing the fluid's resistance on the workpiece W's surface. For example, the machining system SYS may form a riblet structure on the workpiece W to reduce the noise generated when the fluid and the surface of the workpiece W move relative to each other. For example, the machining system SYS may form a riblet structure on the workpiece W that generates vortices in relation to the fluid flow on the surface of the workpiece W. For example, the machining system SYS may form a structure on the workpiece W that gives the surface of the workpiece W hydrophobicity.

[0209] In the above description, the machining system SYS forms a riblet structure RB on the surface of the workpiece W. However, the machining system SYS may form any structure having any shape on the surface of the workpiece W. One example of any structure is a structure that generates vortices in relation to the fluid flow on the surface of the workpiece W. Another example of any structure is a structure that imparts hydrophobicity to the surface of the workpiece W. Another example of any structure is a micro- or nanometer-order fine texture structure (typically a bumpy structure including mountain and groove structures) formed regularly or irregularly. The fine texture structure may include at least one of a sharkskin structure and a dimple structure that has the function of reducing resistance by fluids (gas and / or liquids). The fine texture structure may include a lotus leaf surface structure that has at least one of a liquid-repellent function and a self-cleaning function (e.g., having a lotus effect). The fine texture structure may include at least one of the following: a micro-protrusion structure having a liquid transport function (see U.S. Patent Publication No. 2017 / 0044002), a bumpy structure having a hydrophilic function, a bumpy structure having an antifouling function, a moth-eye structure having at least one of a reflectivity reduction function and a liquid-repellent function, a bumpy structure that exhibits structural color by enhancing only light of a specific wavelength through interference, a pillar array structure having an adhesive function utilizing van der Waals forces, a bumpy structure having an aerodynamic noise reduction function, a honeycomb structure having a droplet collection function, and a bumpy structure that improves adhesion with a layer formed on the surface, and a bumpy structure for reducing frictional resistance. In this case as well, the convex structure constituting the bumpy structure may have the same structure as the convex structure 81 constituting the riblet structure RB described above. The groove structure constituting the bumpy structure may have the same structure as the groove structure 82 constituting the riblet structure RB described above. The fine texture structure does not have to have a specific function.

[0210] In the above description, the processing system SYS forms a riblet structure RB on the surface of the workpiece W. However, the processing system SYS may also form a mold for transferring the riblet structure RB onto the surface of the workpiece W. In this case, the workpiece W may be the surface of a moving body or a film that can be attached to a moving body.

[0211] In the above description, the processing system SYS processes the workpiece W by irradiating it with processing light EL. However, the processing system SYS may also process the workpiece W by irradiating it with any energy beam other than light. In this case, the processing system SYS may be equipped with a beam irradiation device capable of irradiating any energy beam in addition to or instead of the processing light source 2. Examples of any energy beam include at least one of a charged particle beam and an electromagnetic wave. Examples of a charged particle beam include at least one of an electron beam and an ion beam.

[0212] In the above description, the processing system SYS has a single galvanometer mirror 21 as an interference fringe moving member in the first four processing optical systems 15 (15A to 15D), with the mirrors located before and after the first optical system 16 (16A, 16C). However, the interference fringe moving member can be configured in any way that moves the position of the interference region IA (interference fringe IS) formed in the second optical system 17 (17A to 17D) in a direction perpendicular to the optical axis of the second optical system 17, and is not limited to the above example. Furthermore, although the galvanometer mirror 21 as an interference fringe moving member is provided individually before and after the first optical system 16 (16A, 16C), multiple mirrors may be provided in the optical path from the processing light source 2 through the second optical system 17 to the workpiece W, or multiple mirrors may be provided in the optical path from the processing light source 2 through the third optical system 18 to the workpiece W, and is not limited to the above example. As an example, in the processing optical system 15A, another galvanometer mirror may be provided in addition to the galvanometer mirror 21. In this example, in the second optical system 17 of the processing optical system 15A, a re-imaging optical system can be placed between the special beam splitter 25 and the lens 33, and a galvanometer mirror can be provided between the re-imaging optical system and the lens 33 at a position that is substantially conjugate to the special beam splitter 25. In this case, the galvanometer mirror between the re-imaging optical system and the lens 33, and the galvanometer mirror 21, will function as interference fringe moving members. Furthermore, in this case, if necessary, a galvanometer mirror can also be provided in the optical path from the processing light source 2 through the third optical system 18 to the workpiece W.

[0213] In the above description, the processing system SYS is shown as a processing optical system 15 (15A to 15H) with an example of multiple second optical systems 17 (17A to 17H). However, the second optical system 17 may have other configurations, as long as it divides the second processing light EL2 from the first optical system 16 to form multiple second processing light EL22 that irradiate the workpiece W from different incident directions to form interference fringes IS, and is not limited to the above example. Other second optical systems 17 may also form multiple second processing light EL22 that propagate in different directions from the first optical system 16 by using a diffractive optical element (DOE) or an optical mask (which partially obstructs the propagation of light).

Claims

1. A first optical system that splits the processing light from the light source into a first processing light and a second processing light, A second optical system that divides the second processing light into a plurality of second processing lights and irradiates the object with the divided plurality of second processing lights from different incident directions to form interference fringes on the surface of the object, A third optical system is provided to provide the DC component of the fluence distribution without affecting the contrast component of the fluence distribution that influences the formation of the interference fringes, by irradiating the first processing light from the first optical system toward the interference region on the surface of the object where the interference fringes are formed. Equipped with, A processing optical system that removes material from the surface of an object by using the plurality of second processing lights from the second optical system and the first processing light from the third optical system to form an uneven shape.

2. The third optical system simultaneously irradiates the object with the plurality of second processing lights and the first processing light. The machining optical system according to claim 1.

3. By simultaneously irradiating the object with the plurality of second processing lights and the first processing light, the minimum fluence in the dark areas of the interference fringes formed on the surface of the object is set to a fluence that can remove the surface of the object. The machining optical system according to claim 2.

4. The second optical system uses at least two of the divided plurality of second processed beams to form a first interference fringe on the surface of the object, and uses at least two second processed beams different from the first two to form a second interference fringe on the surface of the object, which is different from the first interference fringe. The processing optical system according to claim 1 or claim 2.

5. The interference region on the surface of the object where the interference fringes are formed includes a first region where the first interference fringes are formed and a second region where the second interference fringes are formed. The machining optical system according to claim 4.

6. The second optical system described above is A light splitting member that splits the second processing light into a plurality of second processing lights, A first optical member into which one of the multiple second processed beams divided by the light splitting member is incident, The optical member includes a second optical member to which a second processing light, different from the first second processing light, is incident, among the plurality of second processing lights divided by the light splitting member, The first second processing light from the first optical member is directed to the light splitting member via the second optical member, and the other second processing light from the second optical member is directed to the light splitting member via the first optical member. The processing optical system according to claim 1 or claim 2.

7. The first processing light is irradiated onto the surface of the object without passing through the second optical system. The processing optical system according to claim 1 or claim 2.

8. The second optical system includes an optical splitting member that splits the second processed light into a plurality of second processed lights, and adjusts at least one of the amplitude and period of the interference fringes by changing the incident angle of the plurality of second processed lights incident on the optical splitting member via the first and second optical members. The machining optical system according to claim 6.

9. The second optical system forms a first interference fringe and a second interference fringe on the surface of the object, the second interference fringe having at least one difference in amplitude and period from the first interference fringe. The processing optical system according to claim 1 or claim 2.

10. The first period during which the first interference fringe is formed by the second optical system and the second period during which the second interference fringe is formed by the second optical system are superimposed in at least part. The machining optical system according to claim 9.

11. The first period during which the first interference fringe is formed by the second optical system and the second period during which the second interference fringe is formed by the second optical system do not overlap. The machining optical system according to claim 9.

12. The first and second interference fringes are at least two of a plurality of types of interference fringes obtained by Fourier transforming the ideal waveform for obtaining the riblet structure to be formed. The processing optical system according to claim 11.

13. The second optical system allows adjustment of at least one of the amplitude and period of the interference fringes. The processing optical system according to claim 1 or claim 2.

14. The second optical system forms interference fringes in at least a portion of the interference region within the processed area on the surface of the object. The third optical system increases the integrated value of the light fluence irradiated to at least a portion of the processing area. The processing optical system according to claim 1 or claim 2.

15. At least a portion of the interference region formed by the second optical system and the irradiation region where the first processing light is irradiated onto the surface of the object by the third optical system overlap in the superposition region on the surface of the object. The surface of the object is processed while changing the positional relationship between the processing area and the superimposed area. The processing optical system according to claim 14.

16. The system further comprises an interference fringe moving member that moves the position of the interference region relative to the second optical system in a direction intersecting the optical axis of the second optical system. The processing optical system according to claim 15.

17. The interference fringe moving member moves the irradiation area to which the first processing light irradiates the surface of the object in the intersecting direction. The processing optical system according to claim 16.

18. The interference fringe moving member includes a scanning mirror that reflects light from the light source, By changing the reflection direction of the scanning mirror, the position of the interference region is moved in a direction that intersects the optical axis of the second optical system. The processing optical system according to claim 16.

19. The interference fringe moving member is positioned in the optical path between the light source and the first optical system. The processing optical system according to claim 16.

20. The interference fringe moving member is positioned in the optical path between the first optical system and the second optical system. The processing optical system according to claim 16.

21. The position of the interference region is changed within the irradiation area where the first processing light is irradiated onto the surface of the object by the third optical system. The processing optical system according to claim 1 or claim 2.

22. The interference region is formed by the third optical system at a fixed position relative to the irradiation region where the first processing light is irradiated onto the surface of the object. The processing optical system according to claim 1 or claim 2.

23. The second optical system modifies at least one of the amplitude and period of the interference fringes formed on the surface of the object. The processing optical system according to claim 1 or claim 2.

24. The second optical system modifies at least one of the amplitude and period of the interference fringes formed on the surface of the object. The processing optical system according to claim 1 or claim 2.

25. The second optical system includes a first polarization beam splitter that splits the second processed light into a second processed light with a first polarization and a second processed light with a second polarization, each having different polarization directions, and an upstream optical system that emits the second processed light with the first polarization and the second processed light with the second polarization such that at least one of the emission angle and emission position is different. The system includes a second polarization beam splitter that splits the first polarization second processed light into a third polarization second processed light and a fourth polarization second processed light having different polarization directions, and splits the second polarization second processed light into a third polarization second processed light and a fourth polarization second processed light, and a downstream optical system that irradiates the third polarization second processed light generated by the first polarization second processed light and the third polarization second processed light generated by the second polarization second processed light onto a first position on the surface of the object to form a first interference fringe, and irradiates the fourth polarization second processed light generated by the first polarization second processed light and the fourth polarization second processed light generated by the second polarization second processed light onto a second position on the surface of the object different from the first position to form a second interference fringe. The processing optical system according to claim 1 or claim 2.

26. The processing light from the aforementioned light source includes pulsed light with a pulse width of nanoseconds or less. The processing optical system according to claim 1 or claim 2.

27. The interference region on the surface of the object where the interference fringes are formed is subjected to ablation. The processing optical system according to claim 1 or claim 2.

28. The second optical system generates the plurality of second processing beams by diffracting the second processing beam. The processing optical system according to claim 1 or claim 2.

29. An interference fringe forming optical system that forms interference fringes on the surface of an object by dividing the second processing light into a plurality of second processing light beams from a first and second processing light beam, which are pulsed light beams whose emission periods overlap for at least a portion of each other, and irradiating the object with the divided plurality of second processing light beams from different incident directions, An illumination optical system that irradiates the first processing light toward the interference region where the interference fringes are formed in order to provide the DC component of the fluence distribution without affecting the contrast component of the fluence distribution that affects the formation of the interference fringes, Equipped with, A processing optical system that removes material from the surface of an object by using the plurality of second processing lights from the interference fringe forming optical system and the first processing light from the irradiation optical system to form an uneven shape.

30. The system further comprises a branching optical system that splits the processing light from the light source into the first processing light and the second processing light. The processing optical system according to claim 29.

31. A processing apparatus that performs riblet processing on the surface of an object using light from a light source, A processing optical system according to claim 1, claim 2, claim 29, or claim 30, A positional relationship changing device that changes the positional relationship between the interference fringes formed on the surface of the object by the processing optical system and the surface of the object. Equipped with, A processing apparatus that performs riblet processing including the uneven shape on the surface of an object using the processing optical system.

32. The positional relationship changing device changes the positional relationship in a direction intersecting the fringe pitch direction of the interference fringes. The processing apparatus according to claim 31.

33. A processing method for performing riblet processing on the surface of an object, which includes an uneven shape, using light from a light source, The processing light from the aforementioned light source is split into a first processing light and a second processing light. The second processing light is divided into a plurality of second processing lights, and the divided plurality of second processing lights are irradiated onto the object from different incident directions to form interference fringes on the surface of the object. The first processing light is irradiated onto the surface of the object toward the interference region where the interference fringes are formed, thereby providing the DC component of the fluence distribution without affecting the contrast component of the fluence distribution that influences the formation of the interference fringes. The removal process involves using the plurality of second processing lights and the first processing light to remove the uneven shape from the surface of the object, A processing method that includes this.

34. The processing method according to claim 33, wherein the irradiation includes simultaneously irradiating the object with the plurality of second processing lights and the first processing light so that the minimum fluence in the dark areas of the interference fringes formed on the surface of the object is such that the surface of the object can be removed.

35. Forming the interference fringes involves forming a first interference fringe on the surface of the object using at least two of the divided plurality of second processing lights, and forming a second interference fringe on the surface of the object that is different from the first interference fringe using at least two second processing lights that are different from the first two second processing lights. The processing method according to claim 33, including the following:

36. The processing method according to claim 35, wherein the interference region on the surface of the object on which the interference fringes are formed includes a first region on which the first interference fringes are formed and a second region on which the second interference fringes are formed.

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