Laser device, mirror, and laser processing device

Abstract

A laser device (200) is provided with a mirror used as a partial reflection mirror (6) constituting one end of a resonator (10). The mirror has an inner surface (6a) to which a partial reflection coating for a specific wavelength is applied or to which no partial reflection coating is applied, and an outer surface (6b) which faces the opposite direction from the inner surface (6a) and to which a total transmission coating for a specific wavelength is applied. The inner surface (6a) is a curved surface having a curvature center (O1) positioned on an optical axis (10a) of the resonator (10). The outer surface (6b) is a curved surface having a curvature center (O2) offset from the optical axis (10a) of the resonator (10).

Description

Laser device, mirror and laser processing device

[0001] The present disclosure relates to a laser device that emits a laser beam, a mirror used in the laser device, and a laser processing device that includes the laser device.

[0002] A laser device has been known in the art that amplifies light by oscillating it between a partial reflector and a total reflector, and then emits a portion of the amplified light (laser beam). The partial reflector forms one end of a resonator, and the total reflector forms the other end of the resonator.

[0003] The partial reflector has an inner surface facing the total reflector and an outer surface facing away from the inner surface. The total reflector has a reflective surface that reflects light toward the partial reflector. The optical axis of the resonator is located on a line passing through the center of curvature of the inner surface of the partial reflector and the center of curvature of the reflective surface of the total reflector. The center of curvature of the inner surface of the partial reflector is located on the optical axis of the resonator.

[0004] Patent Document 1 discloses a partial reflector having a curved concave inner surface and a curved convex outer surface as a conventional example. In the partial reflector disclosed in Patent Document 1, the center of curvature of the outer surface is located on the optical axis of the resonator, which passes through the center of curvature of the inner surface.

[0005] Japanese Patent Application Publication No. 5-198880

[0006] In a laser device, a portion of the light that passes through the inner surface of the partial reflector may be reflected by the outer surface of the partial reflector and return to the resonator. In this case, if the center of curvature of the outer surface is located on the optical axis of the resonator as disclosed in Patent Document 1, the light reflected by the outer surface of the partial reflector travels back and forth between the partial reflector and the total reflector and is amplified, generating parasitic oscillation light, which is emitted in approximately the same direction as the optical axis of the laser beam.

[0007] Furthermore, as disclosed in Patent Document 1, if the center of curvature of the outer surface is located on the optical axis of the resonator, the outer and inner surfaces of the partial reflecting mirror will be oriented in roughly the same direction, and the laser beam emitted from the laser device will be reflected by the outer and inner surfaces of the partial reflecting mirror, resulting in the problem that stray light will be emitted in roughly the same direction as the optical axis of the laser beam.

[0008] This makes it difficult to separate the laser beam used to process the workpiece from parasitic oscillation light, stray light, etc. that are unnecessary for processing the workpiece, which may result in processing defects due to the parasitic oscillation light, stray light, etc. being irradiated onto the workpiece.

[0009] The present disclosure has been made in view of the above, and aims to provide a laser device that can suppress the occurrence of processing defects.

[0010] In order to solve the above-mentioned problems and achieve the object, the laser device according to the present disclosure includes a mirror used as a partial reflector constituting one end of a resonator. The mirror has an inner surface that is coated with a partial reflection coating for a specific wavelength or that is not coated with a partial reflection coating, and an outer surface facing away from the inner surface that is coated with a total transmission coating for the specific wavelength. The inner surface is a curved surface having a center of curvature located on the optical axis of the resonator. The outer surface is a curved surface having a center of curvature offset from the optical axis of the resonator.

[0011] The laser device according to the present disclosure has the effect of suppressing the occurrence of processing defects.

[0012] 3 is a partial enlarged view of the partial reflector of the laser device according to the first embodiment; FIG. 4 is a diagram for explaining the function of the resonator of the laser device according to the first embodiment; FIG. 5 is a diagram showing the relationship between the radius of curvature of the inner surface of the partial reflector, the radius of curvature of the outer surface of the partial reflector in the laser device according to the first embodiment, the distance between the optical axis of the laser oscillated light reflected by the outer surface of the partial reflector and the optical axis of the resonator, and the amount of eccentricity of the outer surface of the partial reflector from the optical axis; 12 is a partial enlarged view of FIG. 12, showing the resonator of the laser device according to the fourth embodiment; FIG. 13 is a diagram for explaining the operation of the laser device according to the fourth embodiment; and FIG. 14 is a diagram for explaining the operation of the laser device according to the fourth embodiment.

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser device, a mirror, and a laser processing device according to embodiments will be described in detail below with reference to the accompanying drawings.

[0014] First Embodiment. FIG. 1 is a configuration diagram showing a laser processing apparatus 100 including a laser device 200 according to a first embodiment. Hereinafter, directions will be described in accordance with the right-handed XYZ coordinate system shown in FIG. 1 . The X-axis, Y-axis, and Z-axis directions are perpendicular to one another. The laser processing apparatus 100 processes a workpiece 400 by irradiating the workpiece 400 with a laser beam r1. Processing includes, for example, cutting, welding, and drilling. The workpiece 400 is, for example, a metal plate or substrate. The laser processing apparatus 100 includes a laser device 200 that emits a laser beam r1 and a laser processing machine 300 that focuses the laser beam r1 emitted from the laser device 200 and irradiates the workpiece 400 with the focused laser beam r1. Details of the laser device 200 will be described later. The laser processing machine 300 includes optical components such as mirrors and lenses (not shown) for guiding the laser beam r1 to the workpiece 400, and a housing 300a that houses the optical components. Although not shown, the laser processing apparatus 100 includes a drive mechanism for moving the position of the workpiece 400 in the X-axis, Y-axis, and Z-axis directions. If the Y-axis direction in FIG. 1 is the up-down direction, the laser apparatus 200 in FIG. 1 is viewed along the up-down direction, while the laser processing machine 300 in FIG. 1 is viewed along a direction perpendicular to the up-down direction. In reality, the laser processing machine 300 is positioned so that the laser beam r1 and the workpiece 400, indicated by dotted hatching, are positioned in the negative direction of the Y-axis. For ease of explanation, the laser processing machine 300 in FIG. 1 is rotated 90 degrees from its actual position. The directions shown in FIG. 1 are set for the convenience of explaining the laser apparatus 200 and the laser processing machine 300 and do not specify the orientation in which the laser apparatus 200 and the laser processing machine 300 are used.

[0015] Next, the laser device 200 will be described in detail with reference to FIGS. 2 and 3. FIG. 2 is a perspective view showing the laser device 200 according to the first embodiment. FIG. 3 is a partially enlarged view of FIG. 1, showing the configuration of the resonator 10 of the laser device 200 according to the first embodiment. FIG. 3 is a view of the resonator 10 of the laser device 200 according to the first embodiment, viewed from the positive direction to the negative direction of the Y-axis. FIG. 3 also shows apertures 8 and 9, which are omitted in FIG. 2. As shown in FIGS. 2 and 3, the laser device 200 includes a housing 1, two electrodes 2 and 3, a blower 4, a heat exchanger 5, a partial reflecting mirror 6, a total reflecting mirror 7, and two apertures 8 and 9.

[0016] The housing 1 shown in Fig. 2 is a box-shaped member that encloses a laser gas, which is a laser medium. As shown in Fig. 3, one opening 1a is formed in the housing 1. In this embodiment, the opening 1a is formed in one side wall of the housing 1 in the Z-axis direction. The opening 1a connects the inside and outside of the housing 1. The opening 1a is a portion for emitting the laser beam r1 to the outside of the laser device 200.

[0017] As shown in Figure 2, two electrodes 2 and 3 are installed inside the housing 1. The two electrodes 2 and 3 are spaced apart in the Y-axis direction. The space between the two electrodes 2 and 3 forms a discharge region 12 where the laser gas is excited. When light is amplified by traveling back and forth between the partial reflector 6 and the total reflector 7 (when the light is oscillated as a laser), a high-frequency voltage is applied between the two electrodes 2 and 3 in the Y-axis direction to generate a silent discharge and excite the laser gas. The discharge direction coincides with the Y-axis direction.

[0018] The blower 4 is installed inside the housing 1. The blower 4 is installed on the opposite side of the electrode 3 from the discharge region 12 in the Y-axis direction. The blower 4 serves to circulate the laser gas as shown by arrows A and B in FIG. 2 . In the illustrated example, the blower 4 circulates the laser gas in a rotational direction around the Z-axis. Specifically, the laser gas flows from the blower 4 toward the discharge region 12 in the direction shown by arrow A, and then flows through the discharge region 12 in the negative direction of the X-axis. After passing through the discharge region 12, the laser gas flows toward the heat exchanger 5 in the direction shown by arrow B, and then passes through the heat exchanger 5 to be cooled. The laser gas cooled by the heat exchanger 5 flows into the blower 4 and again flows from the blower 4 toward the discharge region 12 in the direction shown by arrow A. The gas flow direction in the discharge region 12 coincides with the X-axis direction. The gas flow direction may be opposite to the direction shown by arrows A and B. In this gas flow direction, the laser gas flows through the discharge region 12 in the positive direction of the X-axis. In this embodiment, the number of fans 4 is two, but it may be one or three or more. The two fans 4 are arranged at an interval from each other in the Z-axis direction.

[0019] The heat exchanger 5 is installed inside the housing 1. The heat exchanger 5 is installed on the opposite side of the electrode 3 from the discharge region 12 in the Y-axis direction. The heat exchanger 5 is disposed adjacent to the blower 4. The heat exchanger 5 cools the laser gas that has passed through the discharge region 12, and serves to suppress a rise in temperature inside the housing 1.

[0020] As shown in FIG. 3 , the resonator 10 is composed of a partial reflector 6 and a total reflector 7. The partial reflector 6, which is a mirror, constitutes one end of the resonator 10. The partial reflector 6 is positioned away from one end of the electrodes 2 and 3 in the Z-axis direction. The partial reflector 6 has an inner surface 6a and an outer surface 6b. The partial reflector 6 is positioned within the opening 1a. The inner surface 6a side of the partial reflector 6 is in a laser gas atmosphere, and the outer surface 6b side of the partial reflector 6 is in the air. In other words, at the opening 1a, the partial reflector 6 separates the inside and outside of the housing 1. Note that the dashed line protruding from the outer surface 6b in FIG. 3 indicates an extension of the outer surface 6b. Details of the partial reflector 6 will be described later.

[0021] The total reflecting mirror 7 forms the other end of the resonator 10. The partial reflecting mirror 6 and the total reflecting mirror 7 are arranged apart from each other in the Z-axis direction. The partial reflecting mirror 6 and the total reflecting mirror 7 are arranged with the electrodes 2 and 3 between them in the Z-axis direction. The total reflecting mirror 7 is arranged apart from the other ends of the electrodes 2 and 3 in the Z-axis direction. The total reflecting mirror 7 has a reflecting surface 7a that totally reflects light towards the partial reflecting mirror 6. In this embodiment, the reflecting surface 7a is a flat surface.

[0022] The optical axis 10a of the resonator 10 is located on a line passing through the center of curvature O1 of the inner surface 6a of the partial reflecting mirror 6 and the center of curvature of the reflecting surface 7a of the total reflecting mirror 7. However, if the reflecting surface 7a of the total reflecting mirror 7 is flat, the optical axis 10a of the resonator 10 is located on a line that passes through the center of curvature O1 of the inner surface 6a of the partial reflecting mirror 6 and is perpendicular to the total reflecting mirror 7, that is, on a perpendicular line to the total reflecting mirror 7. Note that "on a line" includes on the optical axis when light is optically bent via a folding mirror. The center of curvature O1 of the inner surface 6a of the partial reflecting mirror 6 is located on the optical axis 10a of the resonator 10. A laser beam r1 along the optical axis 10a of the resonator 10 is generated between the inner surface 6a of the partial reflecting mirror 6 and the reflecting surface 7a of the total reflecting mirror 7. Specifically, light is amplified by traveling back and forth between the inner surface 6a of the partial reflecting mirror 6 and the reflecting surface 7a of the total reflecting mirror 7 through the excited laser gas in the discharge region 12, and a portion of the amplified light (laser beam r1) passes through the partial reflecting mirror 6 and is emitted to the outside of the laser device 200. The light along the optical axis 10a of the resonator 10 propagates in the Z-axis direction through the discharge region 12. The laser device 200 of this embodiment is a three-axis orthogonal gas laser device in which the light propagation direction (Z-axis direction), the gas flow direction (X-axis direction) in the discharge region 12, and the discharge direction (Y-axis direction) are mutually orthogonal. Note that FIG. 3 also shows the optical axis 11 of the light amplified by traveling back and forth between the outer surface 6b of the partial reflecting mirror 6 and the reflecting surface 7a of the total reflecting mirror 7.

[0023] The two apertures 8 and 9 are installed inside the housing 1. Openings 8a and 9a that penetrate the apertures 8 and 9 in the Z-axis direction are formed in the apertures 8 and 9. One of the apertures 8 is installed between the partial reflecting mirror 6 and the electrodes 2 and 3 in the Z-axis direction. The aperture 8 is installed so that the center of the opening 8a of the aperture 8 is located on the optical axis 10a of the resonator 10. The other aperture 9 is installed between the total reflecting mirror 7 and the electrodes 2 and 3 in the Z-axis direction. The aperture 9 is installed so that the center of the opening 9a of the aperture 9 is located on the optical axis 10a of the resonator 10.

[0024] Next, the partial reflecting mirror 6 will be described in detail with reference to Fig. 3 and Fig. 4. Fig. 4 is a partial enlarged view of Fig. 3, showing the configuration of the partial reflecting mirror 6 of the laser device 200 according to the first embodiment.

[0025] As shown in FIG. 3 , in this embodiment, the inner surface 6 a is a concave surface that becomes concave in the Z-axis direction away from the electrodes 2 and 3. The inner surface 6 a is either coated with a partial reflection coating for a specific wavelength or is not coated with a partial reflection coating. As shown in FIG. 4 , the inner surface 6 a is a curved surface having a center of curvature O1 located on the optical axis 10 a of the resonator 10. The inner surface 6 a is a curved surface with a radius of curvature R1 centered at the center of curvature O1. The shape of the inner surface 6 a is, for example, a spherical crown shape, but may be changed as appropriate. The shape of the inner surface 6 a may also be a shape in which arcs of the same shape and size are continuous over the entire length in the Y-axis direction.

[0026] As shown in FIG. 3 , the outer surface 6 b faces away from the inner surface 6 a and is coated with a total transmission coating for a specific wavelength. In this embodiment, the outer surface 6 b is a convex surface that is convex in the Z-axis direction away from the electrodes 2 and 3. As shown in FIG. 4 , the outer surface 6 b is a curved surface having a center of curvature O2 that is offset in the X-axis direction from the optical axis 10 a of the resonator 10. The outer surface 6 b is a curved surface with a radius of curvature R2 centered on the center of curvature O2. The center of curvature O2 of the outer surface 6 b is eccentric in the X-axis direction with respect to the optical axis 10 a of the resonator 10 and the center of curvature O1 of the inner surface 6 a. The shape of the outer surface 6 b is, for example, a spherical crown shape, but may be modified as appropriate. The shape of the outer surface 6 b may also be a shape with a one-dimensional curvature, such as a cylindrical surface. The shape of the outer surface 6 b may also be a shape in which arcs of the same shape and size are continuous along the entire length in the Y-axis direction.

[0027] In this embodiment, the center of curvature O2 of the outer surface 6b is located at a position offset in the X-axis direction from the optical axis 10a of the resonator 10, but it may be located at a position offset in a direction intersecting the optical axis 10a of the resonator 10. For example, the center of curvature O2 of the outer surface 6b may be located at a position offset in the Y-axis direction from the optical axis 10a of the resonator 10. The center of curvature O2 of the outer surface 6b is located at a position taking into account the refraction of light at the inner surface 6a, i.e., at a position through which light refracted at the inner surface 6a passes. By decentering the outer surface 6b with respect to the optical axis 10a of the resonator 10, the center of curvature O2 of the outer surface 6b can be located at a position offset from the optical axis 10a of the resonator 10. Note that the center of curvature O2 of the outer surface 6b may also be located at a position offset from the optical axis 10a of the resonator 10 by partially changing the thickness of the partial reflecting mirror 6 in the direction along the optical axis 10a (the dimension in the Z-axis direction in the illustrated example). As shown in FIG. 3, the center of curvature O1 of the inner surface 6a and the center of curvature O2 of the outer surface 6b may be located outside the resonator 10.

[0028] The center of curvature O2 of the outer surface 6b of the partial reflecting mirror 6 can be calculated as follows. Here, the radius of curvature of the inner surface 6a of the partial reflecting mirror 6 shown in Figure 4 is R1, and the radius of curvature of the outer surface 6b of the partial reflecting mirror 6 is R2. The thickness of the partial reflecting mirror 6 on the optical axis 10a is d, and the amount of eccentricity of the outer surface 6b of the partial reflecting mirror 6 from the optical axis 10a is Δ2. The amount of eccentricity Δ2 is the distance along the X-axis between the position where light r5 parallel to the optical axis 10a of the resonator 10 intersects perpendicularly with the outer surface 6b of the partial reflecting mirror 6, and the optical axis 10a of the resonator 10. The refractive index of the partial reflecting mirror 6 is n2. The refractive index n1 of the laser gas is approximately 1. The conditions under which light propagates from a certain position (for example, the position O2 in FIG. 4 ) a distance L to the right on the page, is refracted by and passes through the inner surface 6a of the partial reflecting mirror 6, then reaches the outer surface 6b, is reflected by the outer surface 6b, is again refracted by and passes through the inner surface 6a, propagates a distance L to the left on the page, and returns to the same position (the position O2 in FIG. 4 ) can be calculated using the following equation (1). X is the position of the light, and X' is the tilt of the light. e and f in equation (1) can be calculated using the following equation (2).

[0029]

[0030]

[0031] The conditions under which X is constant regardless of X' can be found by solving these two equations (1) and (2) simultaneously, resulting in the following equations (3) and (4). The center of curvature O2 of the radius of curvature R2 of the outer surface 6b of the partial reflecting mirror 6 can be found from these two equations (3) and (4). However, here, a paraxial approximation is used when the angle of incidence of light on the inner surface 6a of the partial reflecting mirror 6 is small. The center of curvature O2 of the outer surface 6b is located at a position distance L from the inner surface 6a and a position distance X from the optical axis 10a.

[0032]

[0033]

[0034] For example, when the reflecting surface 7a of the total reflecting mirror 7 is flat as shown in Fig. 3, the optical axis 11 of the light when it is reflected by the outer surface 6b of the partial reflecting mirror 6 to oscillate as a laser is parallel to the optical axis 10a of the resonator 10, which is the optical axis of the light when it is reflected by the inner surface 6a of the partial reflecting mirror 6 to oscillate as a laser, and is located a distance X away from the optical axis 10a of the resonator 10. Therefore, for example, if the light reflected by the outer surface 6b of the partial reflecting mirror 6 is blocked by the aperture 8 or aperture 9 inside the resonator 10, the light reflected by the outer surface 6b of the partial reflecting mirror 6 will not oscillate as a laser. The condition for this to hold is that the radii of the openings 8a and 9a of the apertures 8 and 9 are set to R a Then, the following equation (5) is obtained.

[0035]

[0036] Furthermore, when the distance X≠0, even if the light is reflected by the outer surface 6b of the partial reflecting mirror 6 to cause laser oscillation, it propagates in a direction different from the light that has been oscillated by reflection by the inner surface 6a of the partial reflecting mirror 6. This state is shown in Fig. 5. Fig. 5 is a diagram for explaining the operation of the resonator 10 of the laser device 200 according to the first embodiment. Fig. 5 illustrates a laser beam r1 that has been oscillated by reflection by the inner surface 6a of the partial reflecting mirror 6 and transmitted through the partial reflecting mirror 6, and a laser beam r2 that has been oscillated by reflection by the outer surface 6b of the partial reflecting mirror 6 and transmitted through the partial reflecting mirror 6.

[0037] By installing a spatial filter 13 such as an aperture behind the laser device 200, only the laser beam r2 can be blocked. In other words, if the distance X≠0, filtering only the laser beam r2 in the laser processing machine 300 (see FIG. 1) installed behind the laser device 200 prevents the laser beam r2 from reaching the workpiece 400 (see FIG. 1), thereby suppressing processing defects caused by the laser beam r2. In the illustrated example, only the spatial filter 13 is installed. However, a lens, spherical mirror, or the like (not shown) may be installed in front of the spatial filter 13 to focus the laser beam r1 or the laser beam r2 and promote separation of the two laser beams r1 and r2. The conditions for the distance X≠0 are expressed by the following formulas (6) and (7).

[0038]

[0039]

[0040] The condition under which the absolute value of the distance X becomes maximum and the effect is greatest is given by the following equation (8).

[0041]

[0042] FIG. 6 shows the relationship between the radius of curvature R, the radius of curvature R, the distance X, and the amount of eccentricity Δ in the laser device 200 according to the first embodiment. This figure shows the relationship between the radius of curvature R of the inner surface 6 a of the partial reflecting mirror 6, the radius of curvature R of the outer surface 6 b of the partial reflecting mirror 6, the distance X between the optical axis 11 of the light reflected by the outer surface 6 b of the partial reflecting mirror 6 and the optical axis 10 a of the resonator 10, and the amount of eccentricity Δ from the optical axis 10 a of the outer surface 6 b of the partial reflecting mirror 6. For example, when R / R is approximately 0.4 to 1.2, X / Δ>2. In other words, as shown in the above-mentioned formula (5), if the amount of eccentricity Δ is set to be equal to or greater than half the radius Ra of the openings 8 a and 9 a of the apertures 8 and 9, the light reflected by the outer surface 6 b of the partial reflecting mirror 6 is blocked by the apertures 8 and 9, preventing laser oscillation. Therefore, in order to suppress laser oscillation of the light reflected by the outer surface 6b of the partial reflecting mirror 6, the range of R1 / R2 from about 0.4 to 1.2 is most effective.

[0043] Next, the effects of the laser device 200 according to this embodiment will be described.

[0044] First, a conventional laser device 500 will be described with reference to FIG. 7 . FIG. 7 is a structural diagram showing an example of a laser device 500 in which the center of curvature O5 of the outer surface 520b is located on the optical axis 560a of the resonator 560. The laser device 500 includes a discharge region 510, a partial reflecting mirror 520, a total reflecting mirror 530, a bend mirror 540, and a retarder 550. The partial reflecting mirror 520 and the total reflecting mirror 530 are disposed with the discharge region 510 interposed therebetween. The bend mirror 540 is disposed between the discharge region 510 and the total reflecting mirror 530. The bend mirror 540 is a metal mirror for bending the optical path (optical axis 560a) by 90 degrees. The retarder 550 is disposed on the opposite side of the partial reflecting mirror 520 from the discharge region 510. If the center of curvature O5 of the outer surface 520b is on the optical axis 560a of the resonator 560, which passes through the center of curvature O4 of the inner surface 520a of the partial reflecting mirror 520, as in the conventional laser device 500, there is a problem in that the light reflected by the outer surface 520b of the partial reflecting mirror 520 oscillates, generating parasitic oscillation light, and the parasitic oscillation light is emitted in approximately the same direction as the optical axis 560a of the laser beam (the optical axis 560a of the resonator 560). Also, if the center of curvature O5 of the outer surface 520b is on the optical axis 560a of the resonator 560, as in the conventional laser device 500, the outer surface 520b and the inner surface 520a of the partial reflecting mirror 520 are oriented in approximately the same direction, and stray light generated when the laser beam emitted from the laser device 500 is reflected by the outer surface 520b and the inner surface 520a of the partial reflecting mirror 520 is emitted in approximately the same direction as the optical axis of the laser beam (the optical axis 560a of the resonator 560). This makes it difficult to separate the laser beam used to process the workpiece from parasitic oscillation light, stray light, etc. that are not necessary for processing the workpiece, and there is a possibility that processing defects will occur due to the parasitic oscillation light, stray light, etc. entering the laser processing machine and being irradiated onto the workpiece.

[0045] 3 , the outer surface 6 b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is offset from the optical axis 10 a of the resonator 10. Therefore, the light reflected by the outer surface 6 b of the partial reflecting mirror 6 does not travel back and forth between the partial reflecting mirror 6 and the total reflecting mirror 7 and does not oscillate, or even if it does oscillate back and forth between the partial reflecting mirror 6 and the total reflecting mirror 7, it propagates in a direction different from the optical axis 10 a of the resonator 10. In other words, no parasitic oscillation light is generated, or even if parasitic oscillation light is generated, it propagates in a direction different from the optical axis 10 a of the resonator 10. Therefore, even if the laser apparatus 200 of this embodiment is mounted on the laser processing apparatus 100, the parasitic oscillation light is not irradiated onto the workpiece 400, and therefore, it is possible to suppress the occurrence of processing defects caused by the parasitic oscillation light being irradiated onto the workpiece 400.

[0046] Furthermore, in this embodiment, the inner surface 6a of the partial reflecting mirror 6 is a curved surface having a center of curvature O1 located on the optical axis 10a of the resonator 10, and the outer surface 6b is a curved surface having a center of curvature O2 offset from the optical axis 10a of the resonator 10. This creates an angle between the inner surface 6a and the outer surface 6b of the partial reflecting mirror 6. As a result, stray light generated when the laser beam r1 emitted from the laser device 200 is reflected by the outer surface 6b and the inner surface 6a of the partial reflecting mirror 6 is emitted in a different direction at an angle relative to the optical axis of the laser beam r1 (the optical axis 10a of the resonator 10). This makes it possible to separate the laser beam r1 used to process the workpiece 400 from stray light unnecessary for processing the workpiece 400. Therefore, by installing an aperture or the like in the optical path after the laser device 200 to block only the stray light, the stray light will not reach the workpiece 400, thereby suppressing processing defects caused by irradiating the workpiece 400 with stray light.

[0047] As shown in Fig. 1, when the laser beam r1 emitted from the laser device 200 is incident on an optical component (not shown) of the laser processing machine 300, a portion of the laser beam r1 may be reflected and return to the laser device 200 as reflected light r3. At this time, if the center of curvature O5 of the outer surface 520b of the partial reflecting mirror 520 and the center of curvature O4 of the inner surface 520a are on the same optical axis 560a as shown in Fig. 7, the reflected light r3 returning from the laser processing machine 300 shown in Fig. 1 is irradiated onto the outer surface 520b of the partial reflecting mirror 520 shown in Fig. 7, and a portion of the irradiated reflected light r3 is reflected again and enters the laser processing machine 300. When this reflected light r3 is irradiated onto the workpiece 400, processing defects may occur. In this regard, in this embodiment, as shown in Fig. 3, the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is offset from the optical axis 10a of the resonator 10. Therefore, reflected light r3 from the laser processing machine 300 shown in Fig. 1 is irradiated onto the outer surface 6b of the partial reflecting mirror 6, and reflected light r4, which is a portion of the irradiated reflected light r3 that is reflected again, propagates in a direction that is offset from the optical axis of the laser beam r1 (the optical axis 10a of the resonator 10). In other words, the reflected light r4 is not irradiated onto the workpiece 400. This makes it possible to suppress the occurrence of processing defects caused by the reflected light r4 being irradiated onto the workpiece 400.

[0048] 1, since the outer surface 6b of the partial reflecting mirror 6 is a curved surface, the divergence angle of the laser beam r1 emitted from the laser device 200 can be set to a predetermined value, and therefore the diameter of the laser beam r1 incident on the laser processing machine 300 installed after the laser device 200 can be made to an appropriate size. For example, if the laser device 200 emits a collimated laser beam r1 (i.e., a divergence angle of 0), the design of the optical components of the laser processing machine 300 can be simplified.

[0049] If the outer surface 6b of the partial reflecting mirror 6 is flat, and the reflected light r3 from the laser processing machine 300 is perpendicularly incident on the outer surface 6b of the partial reflecting mirror 6, it may be reflected directly toward the work-piece 400. In this regard, if the outer surface 6b of the partial reflecting mirror 6 is curved as in the present embodiment, the reflected light r4 reflected by the outer surface 6b of the partial reflecting mirror 6 propagates toward the work-piece 400 while diverging, and is therefore attenuated when it reaches the work-piece 400. This makes it possible to suppress the occurrence of processing defects caused by the reflected light r4 being irradiated onto the work-piece 400.

[0050] Next, a modification of the laser device 200 according to the first embodiment will be described.

[0051] 3 is a flat surface in this embodiment, but may be a curved surface. For example, the reflecting surface 7a of the total reflecting mirror 7 may be a concave surface that is concave in the direction away from the electrodes 2 and 3 in the Z-axis direction.

[0052] Second Embodiment Next, a laser device 200A according to a second embodiment will be described with reference to FIGS. 8 and 9. FIG. 8 is a perspective view showing the laser device 200A according to the second embodiment. FIG. 9 is a configuration diagram showing a resonator 10A of the laser device 200A according to the second embodiment. FIG. 9 is a view of the resonator 10A of the laser device 200A according to the second embodiment, viewed from the positive direction to the negative direction of the Y-axis. FIG. 9 shows apertures 8 and 9, which are omitted in FIG. 8. This embodiment differs from the first embodiment in that the laser device 200A further includes a folding mirror 14. Note that in the second embodiment, parts that overlap with those in the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted.

[0053] As shown in FIGS. 8 and 9 , the resonator 10A is composed of a partial reflecting mirror 6, a total reflecting mirror 7, and a folding mirror 14. The folding mirror 14 is disposed on the optical axis 10a of the resonator 10A between the partial reflecting mirror 6 and the total reflecting mirror 7. As shown in FIG. 9 , the folding mirror 14 and the partial reflecting mirror 6 are disposed at an interval in the Z-axis direction. The folding mirror 14 and the total reflecting mirror 7 are disposed at an interval in the X-axis direction. The partial reflecting mirror 6 and the total reflecting mirror 7 are disposed at an interval in both the X-axis direction and the Z-axis direction. The folding mirror 14 is a metal mirror for folding the optical path (optical axis 10a) at 90°. In this embodiment, there is one folding mirror 14, but two or more mirrors may be used. The folding mirror 14 has a reflective surface 14a that totally reflects light toward the partial reflecting mirror 6 and the total reflecting mirror 7. In this embodiment, the reflective surface 14a is flat. The other aperture 9 is disposed between the folding mirror 14 and the electrodes 2 and 3 in the Z-axis direction.

[0054] Next, the effects of the laser device 200A according to this embodiment will be described.

[0055] In this embodiment, laser device 200A includes folding mirror 14 that is disposed on optical axis 10a of resonator 10A between partial reflecting mirror 6 and total reflecting mirror 7. Even in this embodiment, outer surface 6b of partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is shifted from optical axis 10a of resonator 10A, and therefore the same effects as those of the first embodiment can be achieved.

[0056] Next, a modification of the laser device 200A according to the second embodiment will be described.

[0057] 9 is located at a position offset in the X-axis direction from the optical axis 10a of the resonator 10A in this embodiment, but may be located at a position offset in a direction intersecting the optical axis 10a of the resonator 10A. For example, the center of curvature O2 of the outer surface 6b of the partial reflecting mirror 6 may be located at a position offset in the Y-axis direction from the optical axis 10a of the resonator 10A. Note that the center of curvature O2 of the outer surface 6b may be located at a position offset from the optical axis 10a of the resonator 10A by partially changing the thickness of the partial reflecting mirror 6 in the direction along the optical axis 10a (the dimension in the Z-axis direction in the illustrated example).

[0058] 9 is a flat surface in this embodiment, but may be a curved surface. For example, the reflecting surface 7a of the total reflecting mirror 7 may be a concave surface that is concave in the X-axis direction away from the folding mirror 14.

[0059] 9 is a flat surface in the present embodiment, but may be a curved surface. For example, the reflecting surface 14a of the reflecting mirror 14 may be a concave surface that is concave in the direction away from the electrodes 2 and 3.

[0060] Third Embodiment Next, a laser device 200B according to a third embodiment will be described with reference to FIGS. 10 and 11 . FIG. 10 is a perspective view showing the laser device 200B according to the third embodiment. FIG. 11 is a configuration diagram showing a resonator 10B of the laser device 200B according to the third embodiment. FIG. 11 is a view of the resonator 10B of the laser device 200B according to the third embodiment, viewed from the positive direction to the negative direction of the Y-axis. FIG. 11 shows apertures 8 and 9, which are omitted in FIG. 10 . This embodiment differs from the second embodiment in that the total reflection mirror 7 is a one-dimensional retroreflection mirror. Note that in the third embodiment, parts that overlap with the first and second embodiments are designated by the same reference numerals, and descriptions thereof will be omitted.

[0061] As shown in Figures 10 and 11, the total reflecting mirror 7 is a one-dimensional retroreflecting mirror having two mutually orthogonal reflecting surfaces 7a. The two reflecting surfaces 7a are parallel to the Y-axis direction. The extension direction of the boundary line 7b between the two reflecting surfaces 7a is also parallel to the Y-axis direction. As shown in Figure 11, the center of curvature O2 of the outer surface 6b is located at a position offset from the optical axis 10a of the resonator 10B. Note that, because a one-dimensional retroreflecting mirror is used as the total reflecting mirror 7, the optical axis 11 of the light that is reflected by the outer surface 6b of the partial reflecting mirror 6 and oscillates as a laser passes through the boundary line 7b of the total reflecting mirror 7.

[0062] Here, if the resonator length of the laser device 200B according to this embodiment is Lr and the distance along the X-axis direction between the optical axis 11 of the light that is reflected by the outer surface 6b of the partial reflecting mirror 6 and the optical axis 10a of the resonator 10B is ds, the distance ds can be calculated using the following formulas (9) and (10). Note that the resonator length Lr is the length from the inner surface 6a of the partial reflecting mirror 6 to the reflecting surface 7a of the total reflecting mirror 7.

[0063]

[0064]

[0065] From these two formulas (9) and (10), if the radius Ra of the opening 8a of the aperture 8 near the partial reflecting mirror 6 is set so as to satisfy the following formula (11), laser oscillation of the light reflected by the outer surface 6b of the partial reflecting mirror 6 can be suppressed.

[0066]

[0067] Next, the effects of the laser device 200B according to this embodiment will be described.

[0068] In this embodiment, the laser device 200B is a one-dimensional retroreflecting mirror and includes a total reflecting mirror 7 that forms the other end of the resonator 10B. A laser beam r1 is generated along the optical axis 10a of the resonator 10B between the inner surface 6a of the partial reflecting mirror 6 and the total reflecting mirror 7. Even in this configuration, the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is offset from the optical axis 10a of the resonator 10B, thereby achieving the same effect as in the first embodiment. That is, even if light is reflected by the outer surface 6b of the partial reflecting mirror 6 to cause laser oscillation, it propagates in a direction different from the laser-oscillated light reflected by the inner surface 6a of the partial reflecting mirror 6. Therefore, by filtering only the laser beam r2 (see FIG. 5) in the laser processing machine 300 (see FIG. 1) installed after the laser device 200B, the laser beam r2 does not reach the workpiece 400 (see FIG. 1), thereby suppressing processing defects caused by the laser beam r2.

[0069] Next, a modification of the laser device 200B according to the third embodiment will be described.

[0070] In this embodiment, the center of curvature O2 of the outer surface 6b shown in FIG. 11 is shifted in the X-axis direction from the optical axis 10a of the resonator 10B, but it may be shifted in a direction intersecting the optical axis 10a of the resonator 10B. For example, the center of curvature O2 of the outer surface 6b of the partial reflecting mirror 6 may be shifted in the Y-axis direction from the optical axis 10a of the resonator 10B. In this configuration, laser oscillation of light reflected by the outer surface 6b of the partial reflecting mirror 6 is suppressed under the condition that the above-mentioned formula (5) is satisfied, as in the first embodiment. On the other hand, in this embodiment, since the total reflecting mirror 7 is a one-dimensional (X-axis direction) retroreflecting mirror, when the center of curvature O2 of the outer surface 6b of the partial reflecting mirror 6 is shifted in the X-axis direction from the optical axis 10a of the resonator 10B, laser oscillation of light reflected by the outer surface 6b of the partial reflecting mirror 6 is suppressed under the condition that the above-mentioned formula (11) is satisfied. In other words, by comparing the condition of Equation (5) with the condition of Equation (11), shifting the center of curvature O2 of the outer surface 6b of the resonator 10B in a direction in which the value increases (in the X-axis direction or the Y-axis direction) increases, the effect of suppressing laser oscillation of light reflected by the outer surface 6b of the partial reflecting mirror 6 is greater. Furthermore, the radii of curvature R1 and R2 of the partial reflecting mirror 6 may be changed in the X-axis direction and the Y-axis direction so as to satisfy either the condition of Equation (5) or the condition of Equation (11). For example, the outer surface 6b of the partial reflecting mirror 6 may be a toroidal or cylindrical surface. The center of curvature O2 of the outer surface 6b may be positioned offset from the optical axis 10a of the resonator 10B by partially changing the thickness of the partial reflecting mirror 6 in the direction along the optical axis 10a (the dimension in the Z-axis direction in the illustrated example).

[0071] Fourth Embodiment Next, a laser apparatus 200C according to a fourth embodiment will be described with reference to FIGS. 12 to 15. FIG. 12 is a configuration diagram showing a laser processing apparatus 100C including the laser apparatus 200C according to the fourth embodiment. FIG. 13 is a perspective view showing the laser apparatus 200C according to the fourth embodiment. FIG. 14 is a partial enlarged view of FIG. 12, showing the configuration of a resonator 10C of the laser apparatus 200C according to the fourth embodiment. FIG. 15 is a diagram for explaining the operation of the laser apparatus 200C according to the fourth embodiment. FIG. 14 is a view of the resonator 10C of the laser apparatus 200C according to the fourth embodiment, viewed from the positive to the negative Y-axis direction. FIGS. 12, 14, and 15 show apertures 8 and 9, which are omitted in FIG. 13. This embodiment differs from the second embodiment in that the partial reflector 6 is made of diamond and the total reflector 7 is a concave mirror. In the fourth embodiment, parts that overlap with those of the first to third embodiments are designated by the same reference numerals, and their description will be omitted. If the Y-axis direction in Fig. 12 is the up-down direction, the laser device 200C in Fig. 12 is viewed in the up-down direction, but the laser processing machine 300 in Fig. 12 is viewed in a direction perpendicular to the up-down direction. In reality, the laser processing machine 300 is positioned so that the laser beam r1 and the workpiece 400, represented by dot hatching, are positioned in the negative direction of the Y-axis. For ease of explanation, Fig. 12 illustrates the laser processing machine 300 rotated 90 degrees from its actual state. The directions shown in Fig. 12 are set for the sake of convenience in explaining the laser device 200C and the laser processing machine 300, and do not specify the orientation in which the laser device 200C and the laser processing machine 300 are used.

[0072] The material of the partial reflecting mirror 6 shown in Figures 12 to 15 is diamond. The partial reflecting mirror 6 is formed of a thin diamond, for example, with a thickness of about 1 mm. In this embodiment, the material of the partial reflecting mirror 6 contains only diamond, but it may also contain other substances in addition to diamond. Examples of other substances include zinc selenide, germanium, silicon, zinc sulfide, and chalcogenide glass. The inner surface 6a side of the partial reflecting mirror 6 shown in Figure 14 is in a laser gas atmosphere, and the outer surface 6b side of the partial reflecting mirror 6 is in the air. In other words, at the opening 1a, the partial reflecting mirror 6 separates the inside and outside of the housing 1.

[0073] The laser gas pressure is set to a pressure lower than atmospheric pressure. Because the partial reflector 6 is made of thin diamond, pressure distortion occurs in the partial reflector 6 due to the pressure difference between the laser gas pressure and atmospheric pressure during laser oscillation. As a result, the shape of the partial reflector 6 changes before laser oscillation begins and during laser oscillation. Before laser oscillation begins, for example, refers to when the partial reflector 6 is attached to the housing 1 or before the partial reflector 6 is attached to the housing 1. Before laser oscillation begins, the inner surface 6a and outer surface 6b of the partial reflector 6 are flat.

[0074] During laser oscillation, the inner surface 6a of the partial reflector 6 becomes a curved surface having a center of curvature O1 located on the optical axis 10a of the resonator 10C. The inner surface 6a becomes a convex surface that is convex in the Z-axis direction toward the electrodes 2 and 3. During laser oscillation, the outer surface 6b of the partial reflector 6 becomes a curved surface having a center of curvature O2 that is offset from the optical axis 10a of the resonator 10C. The outer surface 6b becomes a concave surface that is concave in the Z-axis direction toward the electrodes 2 and 3. The center of curvature O1 of the inner surface 6a and the center of curvature O2 of the outer surface 6b are located on the opposite side of the outer surface 6b from the inner surface 6a. For example, when the laser gas pressure is 200 Torr and the diamond diameter is 25.4 mm, the radii of curvature of the inner surface 6a and the outer surface 6b due to pressure distortion are approximately 55 m. In addition, by partially changing the thickness of the partial reflecting mirror 6 in the direction along the optical axis 10a (the dimension in the Z-axis direction in the illustrated example), the center of curvature O2 of the outer surface 6b may be set at a position shifted from the optical axis 10a of the resonator 10C.

[0075] The total reflection mirror 7 is a concave mirror having a reflective surface 7a that is concave. The reflective surface 7a is a concave surface that becomes concave in the X-axis direction away from the folding mirror 14. In this embodiment, the reflective surface 14a of the folding mirror 14 is flat, but it may also be a concave surface that becomes concave in the direction away from the electrodes 2 and 3. That is, the folding mirror 14 may be a concave mirror. For example, if the reflective surface 14a of the folding mirror 14 is a toroidal or cylindrical surface, the circularity of the laser beam r1 (see FIG. 12) can be set to an appropriate value. Furthermore, if the reflective surface 14a of the folding mirror 14 is concave, the reflective surface 7a of the total reflection mirror 7 may be flat. That is, the reflective surface 7a of the total reflection mirror 7 or the reflective surface 14a of the folding mirror 14 may be concave. In this embodiment, the inner surface 6a of the partial reflecting mirror 6 is convex, and by giving curvature to the reflecting surface 7a of the total reflecting mirror 7 or the reflecting surface 14a of the folding mirror 14, the partial reflecting mirror 6, the total reflecting mirror 7, and the folding mirror 14 form a stable resonator 10C.

[0076] Next, the effects of the laser device 200C according to this embodiment will be described.

[0077] 14, the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is offset from the optical axis 10a of the resonator 10C, thereby achieving the same effect as in the first embodiment. That is, even if light is reflected by the outer surface 6b of the partial reflecting mirror 6 to generate a laser beam r2 through laser oscillation, the laser beam r2 propagates in a different direction from the laser beam r1 that is generated through laser oscillation through reflection by the inner surface 6a of the partial reflecting mirror 6. Therefore, by filtering only the laser beam r2 in the laser processing machine 300 (see FIG. 12) installed after the laser device 200C, the laser beam r2 does not reach the workpiece 400, and processing defects caused by the laser beam r2 can be suppressed.

[0078] As shown in FIG. 12 , when the laser beam r1 emitted from the laser device 200C is incident on an optical component (not shown) of the laser processing machine 300, a portion of the laser beam r1 may be reflected and return to the laser device 200 as reflected light r3. In this case, in this embodiment, as shown in FIG. 14 , the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 offset from the optical axis 10a of the resonator 10C. Therefore, the reflected light r3 from the laser processing machine 300 shown in FIG. 12 is irradiated onto the outer surface 6b of the partial reflecting mirror 6, and a portion of the irradiated reflected light r3 is reflected again as reflected light r4, which propagates in a direction deviating from the optical axis of the laser beam r1 (the optical axis 10a of the resonator 10C). In other words, the reflected light r4 is not irradiated onto the workpiece 400. This makes it possible to suppress processing defects caused by the reflected light r4 being irradiated onto the workpiece 400. 15, in this embodiment, the outer surface 6b of the partial reflecting mirror 6 is concave, and therefore the reflected light r4 after being reflected by the outer surface 6b is condensed, and the reflected light r4 is irradiated onto a more limited area than in Embodiment 1. Therefore, by installing a damper 15 or the like ahead of the direction in which the reflected light r4 travels, the reflected light r4 can be reliably blocked.

[0079] As described above, the scope of the present disclosure is not limited to cases where the outer surface 6 b of the partial reflecting mirror 6 becomes a curved surface having a center of curvature O2 that is offset from the optical axis 10 a of the resonator 10C before laser oscillation is started. The scope of the present disclosure also includes cases where, as in the present embodiment, deformation and a change in curvature of the partial reflecting mirror 6 occur during laser oscillation, causing the outer surface 6 b of the partial reflecting mirror 6 to become a curved surface having a center of curvature O2 that is offset from the optical axis 10 a of the resonator 10C. Furthermore, factors that cause deformation and a change in curvature of the partial reflecting mirror 6 during laser oscillation include, in addition to the pressure difference between the laser gas pressure and atmospheric pressure described above, physical forces applied to the inner surface 6 a, outer surface 6 b, etc. of the partial reflecting mirror 6, and temperature differences between the inner surface 6 a and outer surface 6 b of the partial reflecting mirror 6.

[0080] Fifth Embodiment Next, a laser device 200D according to a fifth embodiment will be described with reference to FIGS. 16 and 17. FIG. 16 is a perspective view showing the laser device 200D according to the fifth embodiment. FIG. 17 is a configuration diagram showing a resonator 10D of the laser device 200D according to the fifth embodiment. FIG. 17 is a view of the resonator 10D of the laser device 200D according to the fifth embodiment, viewed from the positive direction to the negative direction of the Y-axis. FIG. 17 shows apertures 8 and 9, which are omitted in FIG. 16. This embodiment differs from the second embodiment in that the partial reflector 6 is made of diamond, the total reflector 7 is a one-dimensional retroreflector, and the folding mirror 14 is a concave mirror. Note that in the fifth embodiment, parts that overlap with the first to fourth embodiments are designated by the same reference numerals and will not be described again.

[0081] As shown in Figures 16 and 17, the configuration of the partial reflecting mirror 6 is the same as that of the fourth embodiment described above. The configuration of the total reflecting mirror 7 is the same as that of the third embodiment described above. As shown in Figure 17, the folding mirror 14 is a concave mirror having a reflective surface 14a that is concave. The reflective surface 14a of the folding mirror 14 is a concave surface that becomes concave in the direction away from the electrodes 2 and 3. Because the inner surface 6a of the partial reflecting mirror 6 is convex, by imparting a curvature to the reflective surface 14a of the folding mirror 14, the partial reflecting mirror 6, the total reflecting mirror 7, and the folding mirror 14 form a stable resonator 10D. Note that the center of curvature O2 of the outer surface 6b may be located at a position offset from the optical axis 10a of the resonator 10D by partially changing the thickness of the partial reflecting mirror 6 in the direction along the optical axis 10a (the dimension in the Z-axis direction in the illustrated example).

[0082] Next, the effects of the laser device 200D according to this embodiment will be described.

[0083] In this embodiment, as shown in FIG. 17 , the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 offset from the optical axis 10a of the resonator 10D, thereby achieving the same effect as in the first embodiment. That is, even if light is reflected by the outer surface 6b of the partial reflecting mirror 6 to generate a laser beam r2, the laser beam r2 propagates in a different direction from the laser beam r1 generated by laser oscillation upon reflection by the inner surface 6a of the partial reflecting mirror 6. Therefore, as in the fourth embodiment, by filtering only the laser beam r2 in the laser processing machine 300 (see FIG. 12 ) installed after the laser device 200D, the laser beam r2 does not reach the workpiece 400 (see FIG. 12 ), thereby suppressing processing defects caused by the laser beam r2. Furthermore, in this embodiment, as in the fourth embodiment, processing defects caused by the reflected light r4 (see FIG. 12 ) being irradiated onto the workpiece 400 can be suppressed. Furthermore, in this embodiment, because the outer surface 6b of the partial reflecting mirror 6 is concave, the reflected light r4 after being reflected by the outer surface 6b is condensed in the same manner as in the above-described embodiment 4, and therefore the reflected light r4 is irradiated onto a more limited area than in embodiment 1. Therefore, by installing a damper 15 (see FIG. 15 ) or the like ahead of the traveling direction of the reflected light r4, the reflected light r4 can be reliably blocked.

[0084] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0085] 1,300a Housing, 1a Opening, 2, 3 Electrode, 4 Fan, 5 Heat exchanger, 6, 520 Partial reflection mirror, 6a, 520a Inner surface, 6b, 520b Outer surface, 7, 530 Total reflection mirror, 7a, 14a Reflecting surface, 7b Boundary line, 8, 9 Aperture, 8a, 9a Opening, 10, 10A, 10B, 10C, 10D, 560 Resonator, 10a, 11, 560a Optical axis, 12, 510 Discharge area, 13 Spatial filter, 14 Bending mirror, 15 Damper, 100, 100C Laser processing device, 200, 200A, 200B, 200C, 200D, 500 Laser device, 300 Laser processing machine, 400 Processing object, 540 Bend mirror, 550 Retarder, O1, O2, O4, O5 Center of curvature.

Claims

1. A laser device comprising a mirror used as a partial reflector constituting one end of a resonator, the mirror having an inner surface that is coated with a partial reflection coating for a specific wavelength or that is not coated with a partial reflection coating, and an outer surface facing away from the inner surface that is coated with a total transmission coating for the specific wavelength, the inner surface being a curved surface having a center of curvature located on the optical axis of the resonator, and the outer surface being a curved surface having a center of curvature offset from the optical axis of the resonator.

2. A laser device according to claim 1, characterized in that it comprises a one-dimensional retroreflecting mirror that forms the other end of the resonator, and a laser beam is generated along the optical axis of the resonator between the inner surface of the mirror and the total reflecting mirror.

3. A laser device according to claim 2, further comprising a folding mirror disposed on the optical axis of the resonator between the mirror and the total reflection mirror.

4. A laser device according to claim 3, wherein said folding mirror has a toroidal surface.

5. A laser device according to any one of claims 1 to 4, wherein the outer surface of the mirror is a toroidal surface.

6. A laser device according to any one of claims 1 to 5, wherein the outer surface of the mirror is a cylindrical surface.

7. A laser device according to any one of claims 1 to 6, characterized in that the material of said mirror contains diamond.

8. A laser device according to any one of claims 1 to 7, wherein the center of curvature of the outer surface is on the opposite side of the outer surface from the inner surface.

9. A mirror used as a partial reflector constituting one end of a resonator, comprising: an inner surface that is either coated with a partial reflection coating for a specific wavelength or that is not coated with a partial reflection coating; and an outer surface facing the opposite side to the inner surface that is coated with a total transmission coating for a specific wavelength, wherein the inner surface is a curved surface having a center of curvature located on the optical axis of the resonator; and the outer surface is a curved surface having a center of curvature that is offset from the optical axis of the resonator.

10. A laser processing device comprising: a laser device according to any one of claims 1 to 8; and a laser processing machine that focuses the laser beam emitted from the laser device and irradiates it onto an object to be processed.

Images