Optical systems and laser processing equipment

Abstract

To provide an optical system and a laser processing device with which it is possible to downsize the optical system of the laser processing device and heighten the safety of laser processing.SOLUTION: Provided is an optical system (30, 30A and 30B) for relaying light to a processing lens (26) which is used for processing a workpiece, the system comprising a spatial light modulator (24) and a second lens (L2) located between the spatial light modulator and the processing lens. When it is assumed that f2 represents the focal distance of the second lens and M represents the magnification of projection from the spatial light modulator to the processing lens pupil of the processing lens, the distance D from the second lens to the processing lens pupil is D=f2-Mf2, and the distance D1 from the spatial light modulator to the second lens is D1=f2-f2 / M, the spatial light modulator being in a conjugate relation with the processing lens pupil of the processing lens.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an optical system and a laser processing apparatus, and particularly to an optical system and a laser processing apparatus that condense laser light onto a workpiece to perform laser processing.

Background Art

[0002] Conventionally, there has been known a technique of forming a cutting start point region serving as a starting point for cutting inside a workpiece along a cutting planned line of the workpiece by irradiating the workpiece with laser light while aligning the condensing point inside the workpiece (see, for example, Patent Document 1).

[0003] In the laser processing apparatus described in Patent Document 1, a pair of lenses of a 4F lens unit constitute a bilateral telecentric optical system in which the reflection surface of a reflective spatial light modulator and the entrance pupil surface of a condensing lens unit are in an imaging relationship.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above-described laser processing apparatus, in addition to a processing optical system such as a condensing lens unit, optical systems such as an observation optical system and an AF (Automatic Focus) optical system (hereinafter referred to as an accessory optical system) are provided. The above-described accessory optical system needs to be provided between the 4F optical system and the processing optical system.

[0006] Figure 10 shows an example of the optical system of a laser processing apparatus. In Figure 10, a pair of lenses L1 and L2 constitute an afocal optical system (4F optical system). Of the pair of lenses L1 and L2, the lens furthest from the pupil 26a of the processing lens is designated as the first lens L1, and the lens closest to it is designated as the second lens L2, with the focal lengths of the first lens L1 and the second lens L2 being f1 and f2, respectively.

[0007] As shown in Figure 10, in an optical system using a 4F optical system, in order to secure space for ancillary optical systems, it is necessary to increase the focal length f2 of the second lens L2, which is closer to the processed lens pupil 26a, among the pair of lenses that make up the 4F optical system.

[0008] The following describes the size of the optical system of the laser processing apparatus. The magnification M from the spatial light modulator 24 to the processing lens pupil 26a is largely determined by the size of the spatial light modulator 24 and the processing lens pupil 26a. The magnification M from the spatial light modulator 24 to the processing lens pupil 26a is expressed by the following equation (1).

[0009]

number

[0010] As shown in Figure 10, the pupil 26a of the processed lens is positioned at the rear focal point of the second lens L2, and the spatial light modulator 24 is positioned at the front focal point of the first lens L1. In other words, the spatial light modulator 24 and the pupil 26a of the processed lens are conjugate. Therefore, the distance L from the spatial light modulator 24 to the pupil 26a of the processed lens is expressed by the following equation (2).

[0011] L = 2 × (f1 + f2) …(2) As shown in equation (1), the focal length f1 of the first lens L1 is determined when the magnification M is determined. Then, in order to provide an auxiliary optical system between the second lens L2 and the pupil 26a of the processing lens, if the focal length f2 of the second lens L2 is increased, the focal length f1 of the first lens L1 will inevitably increase from equation (1). For this reason, as shown in equation (2), the distance L from the spatial light modulator 24 to the pupil 26a of the processing lens becomes longer, and the optical system of the laser processing device becomes larger.

[0012] When the distance L is expressed using the focal length f2 and magnification M of the second lens L2 as parameters, the following equation (3) is obtained.

[0013]

number

[0014] Note that D is the distance from the second lens L2 to the pupil 26a of the processed lens, and in the example shown in Figure 10, it is equal to the focal length f2 of the second lens L2.

[0015] Here, if we set f2 = 200 mm and M = -2 / 3, then from equation (1) we get f1 = 300 mm, and from equation (3) we get L = 1000 mm.

[0016] Furthermore, if we set f2 = 300 mm and M = -2 / 3, then from equation (3) we get L = 1500 mm, which means the total length of the optical system of the laser processing device becomes extremely large.

[0017] As described above, increasing the overall length of the optical system of a laser processing device can make it more susceptible to the effects of angular errors in optical elements, potentially compromising the stability of laser processing. Furthermore, it can also become more susceptible to the effects of thermal expansion of the laser processing device, potentially compromising the stability of laser processing.

[0018] This invention has been made in view of these circumstances, and aims to provide an optical system and a laser processing apparatus that can miniaturize the optical system of a laser processing apparatus and improve the stability of laser processing. [Means for solving the problem]

[0019] In order to achieve the above object, a first aspect of the present invention is an optical system that relays light to a processing lens used for processing a workpiece, including a spatial light modulator and a second lens disposed between the spatial light modulator and the processing lens. When the focal length of the second lens is f2 and the projection magnification from the spatial light modulator to the processing lens pupil of the processing lens is M, the distance D from the second lens to the processing lens pupil is D = f2 - Mf2, the distance D1 from the spatial light modulator to the second lens is D1 = f2 - f2 / M, and the spatial light modulator is in a conjugate relationship with the processing lens pupil of the processing lens.

[0020] The optical system according to the second aspect of the present invention, in the first aspect, includes a first lens disposed upstream of the spatial light modulator, and the first lens and the second lens constitute an afocal optical system.

[0021] The optical system according to the third aspect of the present invention, in the first aspect, includes a first lens disposed so that light incident on the spatial light modulator passes through and reflected light reflected by the spatial light modulator after being incident on the spatial light modulator passes through, and the first lens and the second lens constitute an afocal optical system.

[0022] The optical system according to the fourth aspect of the present invention, in the first aspect, the spatial light modulator has a condensing action, and the focal length f1 of the spatial light modulator is f1 = -f2 / M.

[0023] A fifth aspect of the present invention is a laser processing apparatus including a processing lens and an optical system according to any one of the first to fourth aspects. The spatial light modulator irradiates with a condensing point inside the workpiece, modulates laser light for forming a laser processing region inside the workpiece, and the optical system relays the laser light modulated by the spatial light modulator to the processing lens.

Advantages of the Invention

[0024] According to the present invention, the distance from the spatial light modulator to the processing lens pupil can be shortened, and the stability of laser processing can be enhanced. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 shows a laser processing apparatus according to the first embodiment of the present invention. [Figure 2] Figure 2 is a block diagram of the control device. [Figure 3] Figure 3 is a conceptual diagram illustrating the laser processing region formed near the focal point inside the wafer. [Figure 4] Figure 4 is a conceptual diagram illustrating the laser processing region formed near the focal point inside the wafer. [Figure 5] Figure 5 is a conceptual diagram illustrating a state in which laser-processed areas are formed in a multilayer structure inside a wafer. [Figure 6] Figure 6 shows an example of a relay optical system according to the first embodiment of the present invention. [Figure 7] Figure 7 shows an example of a relay optical system according to a second embodiment of the present invention. [Figure 8] Figure 8 shows a laser processing apparatus according to a third embodiment of the present invention. [Figure 9] Figure 9 shows an example of a relay optical system according to a third embodiment of the present invention. [Figure 10] Figure 10 shows an example of the optical system of a laser processing device. [Modes for carrying out the invention]

[0026] Hereinafter, embodiments of the optical system and laser processing apparatus according to the present invention will be described with reference to the attached drawings.

[0027] [First Embodiment] (Laser processing equipment) Figure 1 shows a laser processing apparatus according to the first embodiment of the present invention.

[0028] As shown in Figure 1, the laser processing apparatus 10 according to this embodiment comprises a stage 12, a processing apparatus body (optical system unit) 20, a processing lens 26, and a control device 50. In this embodiment, the processing apparatus body 20 and the control device 50 are shown as separate components, but the configuration is not limited to this, and the processing apparatus body 20 may include part or all of the control device 50.

[0029] Stage 12 is used to hold the workpiece by suction. Stage 12 is configured to be movable in the X and θ directions by a stage drive mechanism 28 (see Figure 2). The stage drive mechanism 28 can be configured with various mechanisms, such as a ball screw mechanism or a linear motor mechanism. The operation of the stage drive mechanism 28 is controlled by a control device 50 (movement control unit 54 in Figure 2).

[0030] In Figure 1, the three directions X, Y, and Z are mutually orthogonal. Of these, the X and Y directions are horizontal, and the Z direction is vertical. The θ direction is the direction of rotation with the vertical axis (Z-axis) as the axis of rotation.

[0031] In this embodiment, a semiconductor wafer (hereinafter referred to as "wafer") W, such as a silicon wafer, is used as the workpiece. The wafer W is divided into multiple regions by cutting lines arranged in a grid pattern, and various devices constituting a semiconductor chip are formed in each of these divided regions. In this embodiment, the case in which a wafer W is used as the workpiece is described, but the present invention is not limited to this, and for example, glass substrates, piezoelectric ceramic substrates, glass substrates, etc. can also be used.

[0032] The wafer W has a backgrind tape (BG tape) with adhesive material attached to the surface (device surface) on which the device is formed, and is placed on the stage 12 with the back surface facing upwards. There are no particular restrictions on the thickness of the wafer W, but one example is 700 μm or more, or 700 μm to 800 μm.

[0033] Alternatively, the wafer W may be placed on the stage 12 with a dicing tape having an adhesive material attached to one side, and the wafer W integrated with the frame via this dicing tape.

[0034] The processing apparatus body 20 comprises a housing 21, a laser light source 22, a spatial light modulator 24, a relay optical system 30, a beam expander 32, and a λ / 2 wave plate 34.

[0035] Inside the housing 21 are a laser light source 22, a spatial light modulator 24, a relay optical system 30, a beam expander 32, and a λ / 2 wave plate 34. The laser light source 22 may also be located outside the housing 21 (for example, on the top or side of the housing 21). A processing lens 26 is detachably attached to the bottom of the housing 21.

[0036] The processing apparatus body 20 is configured to be movable in the Y and Z directions by a body drive mechanism 29 (see Figure 2). The body drive mechanism 29 can be composed of various mechanisms, such as a ball screw mechanism or a linear motor mechanism. The operation of the body drive mechanism 29 is controlled by a control device 50 (movement control unit 54 in Figure 2). This allows the processing apparatus body 20 to be moved in the Y direction and also moved in the Z direction according to the processing position on the wafer W (the position where the laser processing area is formed). Therefore, the position of the focal point of the laser beam LB focused by the processing lens 26 can be changed to form the laser processing area at a desired position on the wafer W.

[0037] The laser light source (IR (InfraRed) laser light source) 22 emits (irradiates) laser light LB for processing to form a laser processing area inside the wafer W. The emission operation of laser light LB by the laser light source 22 is controlled by the control device 50 (laser control unit 56 in Figure 2). The conditions for the laser light LB are, for example, a semiconductor laser-pumped Nd:YAG (Yttrium Aluminum Garnet) laser, a wavelength of 1.1 μm, and a laser light LB spot cross-sectional area of ​​3.14 × 10⁻¹⁴. -8 cm2 The oscillation mode is a Q-switched pulse, the repetition frequency is 80kHz to 200kHz, the pulse width is 180ns to 370ns, and the output power is 8W.

[0038] The laser beam LB emitted from the laser light source 22 is reflected by the total reflection mirror 36 and reaches the beam expander 32. The beam expander 32 expands the laser beam LB emitted from the laser light source 22 to a beam diameter suitable for the spatial light modulator 24.

[0039] The laser beam LB, adjusted by the beam expander 32, is reflected by the total internal reflection mirror 38 and reaches the spatial light modulator 24 via the λ / 2 wave plate 34. The λ / 2 wave plate 34 adjusts the polarization plane of the laser beam LB incident on the spatial light modulator 24.

[0040] The spatial light modulator 24 is a phase-modulation type spatial light modulator that has a light modulation surface consisting of multiple pixels (micro-modulation elements) arranged in two dimensions, and modulates the phase of light incident on the light modulation surface pixel by pixel. For example, a reflective liquid crystal on silicon (LCOS) spatial light modulator (SLM) is used as the spatial light modulator 24. Based on a predetermined modulation pattern set by the spatial light modulator control unit 58 described later, the spatial light modulator 24 modulates the phase of light incident on the light modulation surface pixel by pixel and emits the modulated light in a predetermined direction.

[0041] The operation of the spatial light modulator 24 and the modulation pattern presented by the spatial light modulator 24 are controlled by the control device 50 (spatial light modulator control unit 58 in Figure 2). The modulation pattern may be a pattern (two-dimensional information) in which control values ​​(phase change amounts) corresponding to each of the multiple pixels constituting the optical modulation surface of the spatial light modulator 24 are distributed two-dimensionally, or it may be something like coefficient information when the modulation within the modulation region (optical modulation surface) is expressed as a function.

[0042] The spatial light modulator 24 is positioned in a position optically conjugate to the lens pupil (exit pupil) 26a of the processed lens 26.

[0043] The optical system (relay optical system) 30 is an optical system for relaying the laser beam LB modulated by the spatial light modulator 24 to the processing lens 26, and is provided in the optical path of the laser beam LB between the λ / 2 wave plate 34 and the processing lens 26, and includes the spatial light modulator 24. The relay optical system 30 includes at least one lens L2. The relay optical system 30 constitutes a bilateral telecentric optical system and projects the laser beam LB modulated by the spatial light modulator 24 onto the processing lens 26.

[0044] This relay optical system 30 is a bilateral telecentric reduction optical system, and the absolute value of its projection magnification M (hereinafter also simply referred to as magnification) is less than 1, for example M = -2 / 3.

[0045] The processing lens 26 is an objective lens (focusing optical system) that focuses the laser beam LB into the wafer W. The numerical aperture (NA) of this processing lens 26 is, for example, 0.65.

[0046] The total reflection mirrors 36 to 46 shown in Figure 1 are positioned to bend the optical path of the laser beam LB, and their number and arrangement are not limited to the example shown in Figure 1.

[0047] Although not shown in the diagram, the processing apparatus body 20 is also equipped with an alignment optical system for aligning with the wafer W, an observation optical system, and an AF optical system for maintaining a constant distance (working distance) between the wafer W and the processing lens 26.

[0048] (Control device) Figure 2 is a block diagram showing the control device 50. The control device 50 is implemented by a general-purpose computer, such as a personal computer or a microcomputer.

[0049] The control device 50 includes a processor (e.g., a CPU (Central Processing Unit)), ROM (Read Only Memory), RAM (Random Access Memory), a storage device 60, and an input / output interface, etc.

[0050] In the control device 50, various programs, such as the control program stored in the storage device 60, are loaded into RAM. The programs loaded into RAM are then executed by the processor, thereby realizing the functions of each part of the control device 50 shown in Figure 2, and various arithmetic and control processes are executed via the input / output interface.

[0051] As shown in Figure 2, the control device 50 functions as a control unit 52, a motion control unit 54, a laser control unit 56, and a spatial light modulator control unit 58.

[0052] The control unit 52 comprehensively controls each component of the control device 50 (including the movement control unit 54, the laser control unit 56, the spatial light modulator control unit 58, and the storage device 60).

[0053] The movement control unit 54 controls the relative movement between the stage 12 and the processing device body 20. The movement control unit 54 outputs control signals to the stage drive mechanism 28 to control the movement of the stage 12 in the X and θ directions, and outputs control signals to the main body drive mechanism 29 to control the movement of the processing device body 20 in the Y and Z directions.

[0054] The laser control unit 56 controls the emission of the laser beam LB. The laser control unit 56 outputs control signals to the laser light source 22 that control the wavelength, pulse width, intensity, emission timing, and repetition frequency of the laser beam LB.

[0055] The spatial light modulator control unit 58 outputs a control signal to the spatial light modulator 24 to control its operation. That is, the spatial light modulator control unit 58 controls the spatial light modulator 24 to display a predetermined modulation pattern. By appropriately setting the modulation pattern to be displayed on the spatial light modulator 24, the spatial light modulator control unit 58 makes it possible to modulate the laser light LB (for example, modulating the intensity, amplitude, phase, polarization, etc., of the laser light L). Alternatively, the spatial light modulator control unit 58 may set a modulation pattern for modulating the laser light LB in the spatial light modulator 24 so that the aberration of the laser light LB generated at the position where the focal point of the laser light LB is aligned inside the wafer W is less than or equal to a predetermined aberration.

[0056] The storage device 60 is a device that stores various types of data, including the control program for the control device 50, and includes, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0057] (Laser processing) Figures 3 and 4 are conceptual diagrams illustrating the laser processing region formed near the focal point inside the wafer.

[0058] Figure 3 shows the state in which a laser beam LB incident inside the wafer W forms a laser processing region P at the focal point. Figure 4 shows the state in which the wafer W is moved horizontally under pulsed laser beam LB, forming discontinuous laser processing regions P, P, ... in a row. In this state, the wafer W either breaks naturally starting from the laser processing region P, or it can be broken starting from the laser processing region P by applying a slight external force. In this case, the wafer W is easily divided into chips without chipping occurring on the front or back surface.

[0059] Figure 5 is a conceptual diagram illustrating a state in which laser-processed areas are formed in a multilayer structure inside a wafer.

[0060] When the wafer W is thick and the laser processing region P cannot be cut in a single layer, as shown in Figure 5, the laser processing region P can be formed in multiple layers by changing the focal point of the laser beam LB in the thickness direction of the wafer W and scanning the laser beam LB multiple times across the wafer W. Using the laser processing region P thus formed in multiple layers as a starting point, the wafer W can be cut either spontaneously or by applying a small external force.

[0061] Although Figures 3 to 5 show discontinuous laser processing regions P, P, ... formed by pulsed laser light LB, a continuous laser processing region P may also be formed under a continuous wave of laser light LB.

[0062] (Relay optics) Figure 6 shows an example of a relay optical system according to the first embodiment of the present invention. Note that in Figure 6, the total reflection mirrors 40, 42, 44, and 46 of the relay optical system 30 shown in Figure 1 are omitted.

[0063] As shown in Figure 6, in the relay optical system 30, the spatial light modulator 24 and the lens (hereinafter referred to as the second lens) L2 are arranged in order from the upstream side, furthest from the processed lens pupil 26a.

[0064] Hereinafter, let M be the magnification from the spatial light modulator 24 to the processed lens pupil 26a, and let f2 be the focal length of the second lens L2.

[0065] As shown in Figure 6, the focal length f2 of the second lens L2 is determined such that the distance D from the second lens L2 to the pupil 26a of the processed lens is D = f2 - Mf2. In addition, the spatial light modulator 24 is positioned upstream of the second lens L2 at a distance D1 = f1 + f2 = f2 - f2 / M such that the spatial light modulator 24 and the pupil 26a of the processed lens are conjugate.

[0066] Furthermore, the spatial light modulator 24 according to this embodiment is given power such that its focal length f1 is f1 = -f2 / M. Pattern 1 is the pattern used to give power to the spatial light modulator 24 so that the focal length f1 = -f2 / M.

[0067] In this embodiment, wavefront manipulation by the spatial light modulator 24 is achieved by adding a predetermined modulation pattern to pattern 1. In other words, in this embodiment, the spatial light modulator 24 is used for both power generation and modulation.

[0068] The dimensions of the relay optical system 30 according to this embodiment will be described below. As shown in Figure 6, the distance D from the second lens L2 to the pupil 26a of the processed lens is D = f2 - Mf2. Rearranging this equation yields the following equation (4).

[0069]

number

[0070] Substituting equation (4) into the focal length f1 = -f2 / M of the spatial light modulator 24, we obtain the following equation (5).

[0071]

number

[0072] Therefore, the distance L from the spatial light modulator 24 to the pupil 26a of the processed lens is expressed by the following equation (6).

[0073]

number

[0074] In equation (6), if the distance D from the second lens L2 to the pupil 26a of the processed lens is 200 mm and the magnification M is -2 / 3, then L = 500 mm, and the distance L from the spatial light modulator 24 to the pupil 26a of the processed lens becomes half of that in the example shown in Figure 10.

[0075] According to this embodiment, by providing power to the spatial light modulator 24, the distance L from the spatial light modulator 24 to the pupil 26a of the processing lens can be shortened. This makes it possible to miniaturize the optical system of the laser processing apparatus and improve the stability of laser processing.

[0076] Furthermore, according to this embodiment, there is no 4F optical system between the spatial light modulator 24 and the processing lens, and only the second lens L2 is present, thus enabling the realization of a compact and simple optical system.

[0077] (Numerical example) From Figure 6, if we express the distance L from the spatial light modulator 24 to the processed lens pupil 26a using the focal length f2 of the second lens L2, we obtain the following equation (7).

[0078]

number

[0079] In equation (7), if we set M = -2 / 3 and f2 = 200 mm, then L = 833.33 mm. The distance D between the second lens L2 and the processed lens pupil 26a is D = f2·(1-M) = 333 mm.

[0080] On the other hand, in the optical system shown in Figure 10, the distance D = f2 between the second lens L2 and the pupil 26a of the processed lens is given by the following equation (8).

[0081]

number

[0082] In the first embodiment, the distance D from the second lens L2 to the processed lens pupil 26a is expressed by equation (9).

[0083] D = f²·(1-M) …(9) In the 4F optical system shown in Figure 10, the distance D from the second lens L2 to the processed lens pupil 26a was D = f2. However, in order to make it D = f2·(1-M) as in the first embodiment, we substitute equation (9) for f2 in equation (8). This gives us equation (10).

[0084]

number

[0085] Here, L' is the distance from the spatial light modulator 24 to the pupil 26a of the processed lens, which is necessary to achieve the distance D = f2·(1-M) from the second lens L2 to the pupil 26a of the processed lens in the 4F optical system shown in Figure 10.

[0086] In equation (10), if we set M = -2 / 3 and f2 = 200 mm, then L' = 1666.7 mm.

[0087] As described above, according to the first embodiment, the distance from the spatial light modulator 24 to the processed lens pupil 26a can be reduced to half.

[0088] [Second Embodiment] Next, a second embodiment of the present invention will be described. In the following description, components similar to those in the first embodiment will be denoted by the same reference numerals and their descriptions will be omitted.

[0089] Figure 7 shows an example of a relay optical system according to a second embodiment of the present invention. In Figure 7, as in Figure 6, the total internal reflection mirrors 40, 42, 44, and 46 for bending the optical path of the laser beam LB are omitted.

[0090] As shown in Figure 7, in the relay optical system 30A according to this embodiment, the first lens L1, the spatial light modulator 24, and the second lens L2 are arranged in order from the upstream side, furthest from the processed lens pupil 26a.

[0091] In this embodiment, the upstream first lens L1 is provided with the function of a focusing lens for the spatial light modulator 24.

[0092] As shown in Figure 7, the distance from the first lens L1 to the second lens L2 is f1 + f2, and the first lens L1 and the second lens L2 constitute a 4F optical system (afocal optical system). The processed lens pupil 26a is positioned downstream of the rear focal position F2 of the second lens L2 by -Mf2.

[0093] In this case, as shown in Figure 7, the position P0 conjugate to the processed lens pupil 26a is within the 4F optical system, that is, between the first lens L1 and the second lens L2. The spatial light modulator 24 is positioned at position P0 conjugate to the processed lens pupil 26a.

[0094] Specifically, the position P0 conjugate to the processed lens pupil 26a is at f2 / M, upstream from the rear focal position of the first lens L1 (front focal position of the second lens L2) F1.

[0095] In this embodiment, since the spatial light modulator 24 does not need to have power, the modulation pattern can be the same as that of a normal 4F optical system.

[0096] From the positional relationship between the first lens L1, the spatial light modulator 24, and the second lens L2 in Figure 7, the following equation (11) can be obtained.

[0097]

number

[0098] In this embodiment, in order to secure the magnification M from the spatial light modulator 24 to the pupil 26a of the processed lens, the focal length f1 of the first lens L1 needs to be increased. Also, the laser beam LB is incident on the spatial light modulator 24 at an oblique angle to the light modulation surface. For this reason, in the second embodiment, the distance d between the spatial light modulator 24 and L1 needs to be increased to a certain extent so that the first lens L1 does not obstruct the reflected light from the spatial light modulator 24. Therefore, when determining the focal length f1 of the first lens L1, the magnification M from the spatial light modulator 24 to the pupil 26a of the processed lens and the required distance (d) between the first lens L1 and the spatial light modulator 24 need to be taken into consideration.

[0099] Once the focal length f1 of the first lens L1 and the focal length f2 of the second lens L2 are determined, the required incident beam diameter for the laser light LB incident on the first lens L1 is determined. Therefore, the required beam diameter can be created in the afocal optical system or beam expander 32 upstream of the relay optical system 30A.

[0100] The dimensions of the relay optical system 30 according to this embodiment will be described below. As shown in Figure 7, in this embodiment, the distance L from the first lens L1 to the pupil 26a of the processed lens is expressed by the following equation (12).

[0101] L = f1 + 2·f2 - M·f2 …(12) In equation (12), if D=200mm, f1=230mm, f2=120mm, and the distance d between the first lens L1 and the spatial light modulator 24 is 50mm, then L=550mm.

[0102] According to this embodiment, by giving the first lens L1 a focusing effect, the distance L from the first lens L1 to the pupil 26a of the processing lens can be shortened. This makes it possible to miniaturize the optical system of the laser processing apparatus and improve the stability of laser processing. In addition, by giving the first lens L1 a focusing effect, the load on the spatial light modulator 24 can be reduced.

[0103] Furthermore, according to this embodiment, there is no 4F optical system between the spatial light modulator 24 and the processing lens, and only the second lens L2 is present, thus enabling the realization of a compact and simple optical system.

[0104] [Third Embodiment] Next, a third embodiment of the present invention will be described. In the following description, components similar to those in the first and second embodiments will be denoted by the same reference numerals and their descriptions will be omitted.

[0105] Figure 8 shows a laser processing apparatus according to a third embodiment of the present invention.

[0106] As shown in Figure 8, in the relay optical system 30B according to this embodiment, the first lens L1 is positioned close to the optical modulation surface of the spatial light modulator 24. That is, the first lens L1 is positioned so that the laser beam LB passes through it twice.

[0107] Figure 9 shows an example of a relay optical system according to a third embodiment of the present invention. In Figure 9, as with Figures 6 and 7, the total reflection mirrors 40, 42, 44, and 46 for bending the optical path of the laser beam LB are omitted.

[0108] As shown in Figure 9, in the relay optical system 30B according to this embodiment, the laser beam LB passes through the first lens L1, is reflected by the spatial light modulator 24, and passes through the first lens L1 again. After that, the laser beam LB passes through the second lens L2 and reaches the pupil 26a of the processed lens. In Figure 9, the first lenses L1 through which the laser beam LB passes are indicated in order by the reference numerals L1-1 and L1-2.

[0109] As shown in Figure 9, the distance from the first lens L1-1 to the second lens L2 is f1 + f2, and the first lenses L1-1 and L1-2 and the second lens L2 constitute a 4F optical system (afocal optical system). The processed lens pupil 26a is positioned downstream of the rear focal position F2 of the second lens L2 by -Mf2.

[0110] Furthermore, the spatial light modulator 24 is positioned conjugate to the processed lens pupil 26a, that is, at a position f2 / M upstream from the rear focal position of the first lens L1 (front focal position of the second lens L2) F1.

[0111] In this embodiment, as in the second embodiment, it is not necessary to provide power to the spatial light modulator 24, so the modulation pattern can be the same as that of a normal 4F optical system.

[0112] As shown in Figure 9, in this embodiment, the distance L from the first lens L1 to the processed lens pupil 26a is expressed by equation (12) similar to that in the second embodiment.

[0113] According to this embodiment, by positioning the first lens L1 close to the spatial light modulator 24, the distance L from the first lens L1 to the pupil 26a of the processing lens can be shortened. This makes it possible to miniaturize the optical system of the laser processing apparatus and improve the stability of laser processing.

[0114] Furthermore, according to this embodiment, the first lens L1-2 and the second lens L2 between the spatial light modulator 24 and the processing lens do not constitute a 4F optical system (afocal optical system), thus enabling the realization of a compact and simple optical system.

[0115] Furthermore, in this embodiment, it is not necessary to increase the distance between the first lens L1 and the spatial light modulator 24 so that the reflected light from the spatial light modulator 24 is not blocked by the first lens L1. Therefore, this embodiment provides greater flexibility in the layout of the optical elements.

[0116] Furthermore, according to this embodiment, since the laser beam LB passes through the first lens L1 twice, the refractive power of the first lens L1 can be weakened, and the occurrence of aberrations can be suppressed.

[0117] In the above embodiment, the first lens L1 and the second lens L2 are shown as a single lens, but the present invention is not limited thereto. The first lens L1 and the second lens L2 may each be a lens group consisting of one or more lenses.

[0118] As described above, according to the first to third embodiments, the optical system (30, 30A, and 30B) of the laser processing apparatus 10 can be configured compactly. Furthermore, if necessary, the distance from the second lens L2 to the processing lens pupil 26a can be increased while keeping the overall size of the laser processing apparatus 10 relatively small.

[0119] In actual laser processing equipment, observation optics, AF optics, and other monitoring optics are required between the second lens L2 and the processing lens pupil 26a, and many optical elements are inserted. For this reason, the distance from the second lens L2 to the processing lens pupil 26a needs to be increased.

[0120] However, increasing the focal length f2 of the second lens L2 would consequently increase the focal length f1 of the first lens L1, resulting in a larger overall device. In other words, in the 4F optical system shown in Figure 10, it was necessary that f2 = D.

[0121] In contrast, in the optical systems (30, 30A, and 30B) according to the above embodiment, it is sufficient that f2(1-M)=D, so the focal length f2 of the second lens L2 can be shortened. This makes it possible to miniaturize the optical system of the laser processing apparatus 10. [Explanation of symbols]

[0122] 10…Laser processing device, 12…Stage, 20…Processing device body, 21…Housing, 22…Laser light source, 24…Spatial light modulator, 26…Processing lens, 30, 30A, 30B…(Relay) optical system, L1…First lens, L2…(Second) lens, 32…Beam expander, 34…λ / 2 wave plate, 50…Control device, 52…Control unit, 54…Movement control unit, 56…Laser control unit, 58…Spatial light modulator control unit, 60…Storage device

Claims

1. An optical system that relays light to a processing lens used for processing a workpiece, A spatial light modulator having a light-gathering effect, wherein the focal length f of the spatial light modulator １ ga f １ = -f ２ A spatial light modulator with power set to / M, A first lens is provided, which is arranged such that light incident on the spatial light modulator passes through it, and reflected light that has been reflected by the spatial light modulator after being incident on it also passes through it. The system comprises a second lens positioned between the spatial light modulator and the processed lens, The focal length of the second lens is f ２ When the projection magnification from the spatial light modulator onto the pupil of the processed lens is M, The distance D from the second lens to the pupil of the processed lens is D = f ２ -Mf ２ , The distance D1 from the spatial light modulator to the second lens is D1 = f ２ -f ２ / M, and the spatial light modulator is conjugate to the pupil of the processed lens. An optical system in which the first lens and the second lens constitute an afocal optical system.

2. A laser processing apparatus comprising the processing lens described above and the optical system described in claim 1, The spatial light modulator modulates laser light that is focused onto the inside of the workpiece and irradiated to form a laser processing area inside the workpiece. The optical system is a laser processing apparatus that relays the laser light modulated by the spatial light modulator to the processing lens.

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