Laser device, mirror and laser processing device

Abstract

The laser device (200) includes a mirror used as a partial reflector (6) that constitutes one end of the resonator (10). The mirror has an inner surface (6a) 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 (6b) that faces away from the inner surface (6a) and is coated with a total transmission coating for a specific wavelength. The inner surface (6a) is a curved surface having a center of curvature (O1) located on the optical axis (10a) of the resonator (10). The outer surface (6b) is a curved surface having a center of curvature (O2) that is offset from the optical axis (10a) of the resonator (10).

Description

[Technical field]

[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 including the laser device. [Background technology]

[0002] A laser device is known that amplifies light by making it travel back and forth between a partial reflector and a total reflector, and emits a portion of the amplified light (laser beam). The partial reflector constitutes one end of a resonator, and the total reflector constitutes the other end of the resonator.

[0003] The partial reflector has an inner surface facing toward 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, as a conventional example, a partial reflector having an inner surface that is a curved concave surface and an outer surface that is a curved convex surface. 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 that passes through the center of curvature of the inner surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-198880 Summary of the Invention [Problem to be solved by the invention]

[0006] In a laser device, a part 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 surface and inner surface of the partial reflecting mirror will be oriented in roughly the same direction, and there is a problem in that stray light generated when the laser beam emitted from the laser device is reflected by the outer surface and inner surface of the partial reflecting mirror is 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, and this 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 consideration of the above, and has an object to provide a laser device that can suppress the occurrence of processing defects. [Means for solving the problem]

[0010] In order to solve the above 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. Effect of the Invention

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

[0012] [Figure 1] FIG. 1 is a block diagram showing a laser processing apparatus equipped with a laser device according to a first embodiment. [Diagram 2] FIG. 1 is a perspective view showing a laser device according to a first embodiment; [Diagram 3] FIG. 2 is a partial enlarged view of FIG. 1, showing the configuration of a resonator of the laser device according to the first embodiment; [Figure 4] FIG. 4 is a partial enlarged view of FIG. 3, showing the configuration of a partial reflector of the laser device according to the first embodiment; [Diagram 5] FIG. 1 is a diagram for explaining the operation of a resonator of a laser device according to a first embodiment; [Figure 6] FIG. 1 is a diagram showing the relationship between the radius of curvature of the inner surface of a partial reflector, the radius of curvature of the outer surface of the partial reflector, the distance between the optical axis of light that is oscillated by being 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 in the laser device according to the first embodiment. [Figure 7] FIG. 1 is a diagram showing an example of a laser device in which the center of curvature of the outer surface is located on the optical axis of the resonator. [Figure 8] FIG. 13 is a perspective view showing a laser device according to a second embodiment. [Figure 9] FIG. 13 is a configuration diagram showing a resonator of a laser device according to a second embodiment. [Figure 10] FIG. 13 is a perspective view showing a laser device according to a third embodiment. [Figure 11] FIG. 13 is a configuration diagram showing a resonator of a laser device according to a third embodiment. [Figure 12] FIG. 13 is a block diagram showing a laser processing apparatus equipped with a laser device according to a fourth embodiment. [Figure 13] FIG. 13 is a perspective view showing a laser device according to a fourth embodiment. [Figure 14] FIG. 13 is a partial enlarged view of FIG. 12, showing the configuration of a resonator of a laser device according to a fourth embodiment; [Figure 15] FIG. 13 is a diagram for explaining the operation of the laser device according to the fourth embodiment. [Figure 16] FIG. 13 is a perspective view showing a laser device according to a fifth embodiment. [Figure 17] FIG. 13 is a configuration diagram showing a resonator of a laser device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 drawings.

[0014] Embodiment 1 FIG. 1 is a configuration diagram showing a laser processing apparatus 100 including a laser device 200 according to the first embodiment. In the following, when directions are described, the right-handed XYZ coordinate system shown in FIG. 1 is used. The X-axis direction, the Y-axis direction, and the Z-axis direction are mutually orthogonal directions. The laser processing apparatus 100 is an apparatus for processing an object 400 by irradiating the object 400 with a laser beam r1. The processing includes, for example, cutting, welding, and drilling. The object 400 is, for example, a metal plate or a 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 object 400 with the collected light. The laser device 200 will be described in detail later. The laser processing machine 300 includes optical components such as a mirror and a lens (not shown) for guiding the laser beam r1 to the object 400, and a housing 300a that accommodates the optical components. Although not shown, the laser processing device 100 includes a driving 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 device 200 in FIG. 1 is viewed along the up-down direction, but the laser processing machine 300 in FIG. 1 is viewed along a direction perpendicular to the up-down direction. In reality, the laser beam r1 and the workpiece 400 shown by dot hatching are positioned in the negative direction of the Y-axis direction. In FIG. 1, the laser processing machine 300 is rotated 90 degrees from the actual state for convenience of explanation. The directions shown in FIG. 1 are set for convenience of explanation of the laser device 200 and the laser processing machine 300, and do not specify the posture in which the laser device 200 and the laser processing machine 300 are used.

[0015] Next, the laser device 200 will be described in detail with reference to Fig. 2 and Fig. 3. Fig. 2 is a perspective view showing the laser device 200 according to the first embodiment. Fig. 3 is a partial enlarged view of Fig. 1, and is a configuration diagram showing 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 in the Y-axis direction. In Fig. 3, the apertures 8 and 9 omitted in Fig. 2 are illustrated. 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 reflector 6, a total reflector 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 communicates between 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 FIG. 2, two electrodes 2, 3 are installed inside a housing 1. The two electrodes 2, 3 are arranged with a gap between them in the Y-axis direction. The space between the two electrodes 2, 3 becomes a discharge region 12 that excites the laser gas. When light is amplified by traveling back and forth between the partial reflector 6 and the total reflector 7 (when the light is oscillated into a laser), a high-frequency voltage is applied between the two electrodes 2, 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 discharge area 12 with respect to the electrode 3 in the Y-axis direction. The blower 4 plays a role in circulating the laser gas as shown by the arrows A and B in FIG. 2. In the illustrated example, the blower 4 circulates the laser gas in the rotational direction around the Z-axis. Specifically, the laser gas flows from the blower 4 toward the discharge area 12 in the direction shown by the arrow A, and then flows through the discharge area 12 in the negative direction in the X-axis direction. The laser gas that has passed through the discharge area 12 flows toward the heat exchanger 5 in the direction shown by the 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 flows again from the blower 4 toward the discharge area 12 in the direction shown by the arrow A. The gas flow direction in the discharge area 12 coincides with the X-axis direction. The gas flow direction may be opposite to the direction shown by the arrows A and B. In the case of such a gas flow direction, the laser gas flows through the discharge area 12 in the positive direction in the X-axis direction. The number of fans 4 is two in this embodiment, but may be one or three or more. The two fans 4 are disposed 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 serves to cool the laser gas that has passed through the discharge region 12, and 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 disposed 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 disposed in 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. The dashed line protruding from the outer surface 6b in FIG. 3 indicates an extension of the outer surface 6b. The partial reflector 6 will be described in detail later.

[0021] The total reflecting mirror 7 constitutes 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, 3 between them in the Z-axis direction. The total reflecting mirror 7 is arranged apart from the other end of the electrodes 2, 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 reflector 6 and the center of curvature of the reflecting surface 7a of the total reflector 7. However, if the reflecting surface 7a of the total reflector 7 is flat, 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 reflector 6 and perpendicularly incident on the total reflector 7, that is, on a perpendicular line to the total reflector 7. Note that the line includes the optical axis when the light is optically folded via a folding mirror. The center of curvature O1 of the inner surface 6a of the partial reflector 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 reflector 6 and the reflecting surface 7a of the total reflector 7. Specifically, the light is amplified by traveling back and forth between the inner surface 6a of the partial reflector 6 and the reflecting surface 7a of the total reflector 7 through the excited laser gas in the discharge region 12, and a part of the amplified light (laser beam r1) passes through the partial reflector 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 in 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) and the discharge direction (Y-axis direction) in the discharge region 12 are mutually orthogonal. Note that FIG. 3 also illustrates the optical axis 11 of the light amplified by traveling back and forth between the outer surface 6b of the partial reflector 6 and the reflecting surface 7a of the total reflector 7.

[0023] The two apertures 8, 9 are disposed inside the housing 1. The apertures 8, 9 have openings 8a, 9a formed therein that penetrate in the Z-axis direction. One of the apertures 8 is disposed between the partial reflector 6 and the electrodes 2, 3 in the Z-axis direction. The aperture 8 is disposed 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 disposed between the total reflector 7 and the electrodes 2, 3 in the Z-axis direction. The aperture 9 is disposed 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 partially enlarged view of Fig. 3, and is a configuration diagram showing 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 6a is a concave surface that is concave toward the direction away from the electrodes 2 and 3 in the Z-axis direction. The inner surface 6a 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 6a is a curved surface having a center of curvature O1 located on the optical axis 10a of the resonator 10. The inner surface 6a is a curved surface having a curvature radius R1 centered on the center of curvature O1. The shape of the inner surface 6a is, for example, a spherical crown shape, but may be changed as appropriate. The shape of the inner surface 6a may 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 6b is a surface facing away from the inner surface 6a, and is coated with a total transmission coating for a specific wavelength. In this embodiment, the outer surface 6b is a convex surface that is convex toward the direction away from the electrodes 2 and 3 in the Z-axis direction. As shown in FIG. 4, the outer surface 6b is a curved surface having a center of curvature O2 that is shifted in the X-axis direction from the optical axis 10a of the resonator 10. The outer surface 6b is a curved surface with a curvature radius R2 centered on the center of curvature O2. The center of curvature O2 of the outer surface 6b is eccentric in the X-axis direction with respect to the optical axis 10a of the resonator 10 and the center of curvature O1 of the inner surface 6a. The shape of the outer surface 6b is, for example, a spherical crown shape, but may be changed as appropriate. The shape of the outer surface 6b may be a shape with a one-dimensional curvature, such as a cylindrical surface. The shape of the outer surface 6b may be a shape in which arcs of the same shape and size are continuous over 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 shifted in the X-axis direction from the optical axis 10a of the resonator 10, but may be located at a position shifted 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 shifted 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 consideration the refraction of light at the inner surface 6a, that is, at a position where the light refracted at the inner surface 6a passes through. 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 provided at a position shifted from the optical axis 10a of the resonator 10. The center of curvature O2 of the outer surface 6b may be provided at a position shifted 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 FIG. 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 direction between the position where the light r5 parallel to the optical axis 10a of the resonator 10 perpendicularly intersects 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 indicated by symbol O2 in Figure 4) a distance L to the right on the page, is refracted at and transmitted through the inner surface 6a of the partial reflecting mirror 6, then reaches the outer surface 6b, and is reflected by the outer surface 6b, is refracted and transmitted again at the inner surface 6a, propagates a distance L to the left on the page, and returns to the same position (the position indicated by symbol O2 in Figure 4) can be calculated using the following formula (1). X is the position of the light, and X' is the inclination of the light. e and f in formula (1) can be calculated using the following formula (2).

[0029]

number

[0030]

number

[0031] The condition for X to be constant regardless of X' is 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 we use a paraxial approximation where 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 distance X from the optical axis 10a.

[0032]

number

[0033]

number

[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 when the radius of the openings 8a, 9a of the apertures 8, 9 is set to R a This results in the following equation (5).

[0035]

number

[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, the light propagates in a direction different from that of the light that is reflected by the inner surface 6a of the partial reflecting mirror 6 to cause laser oscillation. This state is shown in Fig. 5. Fig. 5 is a diagram for explaining the action of the resonator 10 of the laser device 200 according to the first embodiment. Fig. 5 illustrates a laser beam r1 that is transmitted through the partial reflecting mirror 6 after the light is reflected by the inner surface 6a of the partial reflecting mirror 6 to cause laser oscillation, and a laser beam r2 that is transmitted through the partial reflecting mirror 6 after the light is reflected by the outer surface 6b of the partial reflecting mirror 6 to cause laser oscillation.

[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, the laser beam r2 will not reach the workpiece 400 (see FIG. 1) by filtering only the laser beam r2 in the laser processing machine 300 (see FIG. 1) installed behind the laser device 200, and processing defects caused by the laser beam r2 can be suppressed. In the illustrated example, only the spatial filter 13 is installed, but a lens, a spherical mirror, etc. (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 condition for the distance X≠0 is the following formula (6) and formula (7).

[0038]

number

[0039]

number

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

[0041]

number

[0042] Here, the relationship between the radius of curvature R1, the radius of curvature R2, the distance X, and the amount of eccentricity Δ2 is shown in FIG. 6. FIG. 6 is a diagram showing the relationship between the radius of curvature R1 of the inner surface 6a of the partial reflecting mirror 6, the radius of curvature R2 of the outer surface 6b of the partial reflecting mirror 6, the distance X between the optical axis 11 of the light that is reflected by the outer surface 6b of the partial reflecting mirror 6 to cause laser oscillation and the optical axis 10a of the resonator 10, and the amount of eccentricity Δ2 from the optical axis 10a of the outer surface 6b of the partial reflecting mirror 6 in the laser device 200 according to the first embodiment. For example, when R1 / R2 is about 0.4 to 1.2, X / Δ2>2. In other words, as shown in the above formula (5), if the amount of eccentricity Δ2 is set to half or more of the radius Ra of the openings 8a, 9a of the apertures 8, 9, the light reflected by the outer surface 6b of the partial reflecting mirror 6 is blocked by the apertures 8, 9, and laser oscillation does not occur. 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 configuration 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 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°. The retarder 550 is disposed on the opposite side of the discharge region 510 with respect to the partial reflecting mirror 520. If the center of curvature O5 of the outer surface 520b is on the optical axis 560a of the resonator 560 passing through the center of curvature O4 of the inner surface 520a of the partial reflecting mirror 520 as in the conventional laser device 500, the light reflected by the outer surface 520b of the partial reflecting mirror 520 oscillates, generating parasitic oscillation light, which is emitted in approximately the same direction as the optical axis of the laser beam (optical axis 560a of the resonator 560). In addition, 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 approximately in the same direction, and stray light generated by the laser beam emitted from the laser device 500 being 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 (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 irradiating the workpiece.

[0045] 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 shifted from the optical axis 10a of the resonator 10, so that the light reflected by the outer surface 6b of the partial reflecting mirror 6 does not oscillate with the total reflecting mirror 7, or even if it oscillates with the total reflecting mirror 7, it propagates in a direction different from the optical axis 10a of the resonator 10. In other words, parasitic oscillation light is not generated, or even if parasitic oscillation light is generated, it propagates in a direction different from the optical axis 10a of the resonator 10. Therefore, even if the laser device 200 of this embodiment is mounted on the laser processing device 100, the parasitic oscillation light is not irradiated on the workpiece 400, so that the occurrence of processing defects caused by the parasitic oscillation light being irradiated on the workpiece 400 can be suppressed.

[0046] In addition, 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 shifted from the optical axis 10a of the resonator 10, so that an angle is formed between the inner surface 6a and the outer surface 6b of the partial reflecting mirror 6. The 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 with respect to the optical axis of the laser beam r1 (the optical axis 10a of the resonator 10). Therefore, it is possible to separate the laser beam r1 used for processing the workpiece 400 from the 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 does not reach the workpiece 400, and the occurrence of processing defects due to the stray light being irradiated onto the workpiece 400 can be suppressed.

[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 part of the laser beam r1 may be reflected and return to the laser device 200 as reflected light r3. At this time, as shown in Fig. 7, 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, 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 part 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 processing target 400, a processing defect may occur. 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 offset from the optical axis 10a of the resonator 10, so that 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 part of the irradiated reflected light r3 that is reflected again, propagates in a direction deviating 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 curved, the divergence angle of the laser beam r1 emitted from the laser device 200 can be set to a predetermined value, so that the diameter of the laser beam r1 incident on the laser processing machine 300 installed behind the laser device 200 can be set to an appropriate size. For example, if the laser device 200 emits a collimated laser beam r1 (i.e., the divergence angle is 0), the design of the optical components of the laser processing machine 300 can be simplified.

[0049] When the outer surface 6b of the partial reflecting mirror 6 is flat, if 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 workpiece 400. In this regard, when 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 workpiece 400 while diverging, and is therefore attenuated when it reaches 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.

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

[0051] 3 is a flat surface in the present 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 Z-axis direction away from the electrodes 2 and 3.

[0052] Embodiment 2 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 omitted in Fig. 8. This embodiment differs from the first embodiment in that the laser device 200A further includes a folding mirror 14. In the second embodiment, the same reference numerals are used for parts that overlap with the first embodiment, and description thereof will be omitted.

[0053] As shown in FIG. 8 and FIG. 9, the resonator 10A is composed of a partial reflector 6, a total reflector 7, and a folding mirror 14. The folding mirror 14 is disposed on the optical axis 10a of the resonator 10A between the partial reflector 6 and the total reflector 7. As shown in FIG. 9, the folding mirror 14 and the partial reflector 6 are disposed at an interval from each other in the Z-axis direction. The folding mirror 14 and the total reflector 7 are disposed at an interval from each other in the X-axis direction. The partial reflector 6 and the total reflector 7 are disposed at an interval from each other in 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°. The number of folding mirrors 14 is one in this embodiment, but may be two or more. The folding mirror 14 has a reflecting surface 14a that totally reflects light toward the partial reflector 6 and the total reflector 7. The reflecting surface 14a is a flat surface in this embodiment. The other aperture 9 is disposed between the folding mirror 14 and the electrodes 2, 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, the laser device 200A includes a folding mirror 14 that is disposed on the optical axis 10a of the resonator 10A between the partial reflecting mirror 6 and the total reflecting mirror 7. Even in this embodiment, the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is shifted from the optical axis 10a of the 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 shifted in the X-axis direction from the optical axis 10a of the resonator 10A in this embodiment, but may be located at a position shifted 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 shifted in the Y-axis direction from the optical axis 10a of the resonator 10A. The center of curvature O2 of the outer surface 6b may be located at a position shifted 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).

[0058] 9 is a flat surface in the present 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] Embodiment 3 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 in the Y-axis direction. In Fig. 11, apertures 8 and 9 omitted in Fig. 10 are shown. In this embodiment, the total reflection mirror 7 is a one-dimensional retroreflection mirror, which is different from the above-mentioned second embodiment. In addition, in the third embodiment, the parts overlapping with the first and second embodiments are given the same reference numerals and the description thereof is omitted.

[0061] As shown in Figs. 10 and 11, the total reflection mirror 7 is a one-dimensional retroreflection mirror having two mutually orthogonal reflection surfaces 7a. The two reflection surfaces 7a are parallel to the Y-axis direction. The extension direction of the boundary line 7b of the two reflection surfaces 7a is parallel to the Y-axis direction. As shown in Fig. 11, the center of curvature O2 of the outer surface 6b is located at a position shifted from the optical axis 10a of the resonator 10B. Since a one-dimensional retroreflection mirror is used as the total reflection mirror 7, the optical axis 11 of the light that is reflected by the outer surface 6b of the partial reflection mirror 6 to oscillate as a laser passes through the boundary line 7b of the total reflection 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 to produce laser oscillation 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]

number

[0064]

number

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

[0066]

number

[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 constitutes the other end of the resonator 10B, and a laser beam r1 along the optical axis 10a of the resonator 10B is generated between the inner surface 6a of the partial reflecting mirror 6 and the total reflecting mirror 7. Even in this case, the outer surface 6b of the partial reflecting mirror 6 is a curved surface having a center of curvature O2 that is shifted from the optical axis 10a of the resonator 10B, so that the same effect as in the above-mentioned embodiment 1 can be achieved. That is, 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 oscillated by reflection 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 behind the laser device 200B, the laser beam r2 does not reach the workpiece 400 (see FIG. 1), and processing defects caused by the laser beam r2 can be suppressed.

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

[0070] In the present 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 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 reflector 6 may be shifted in the Y-axis direction from the optical axis 10a of the resonator 10B. In this configuration, the laser oscillation of the light reflected by the outer surface 6b of the partial reflector 6 is suppressed under the condition that satisfies the above-mentioned formula (5) as in the first embodiment. On the other hand, in the present embodiment, since the total reflector 7 is a one-dimensional (X-axis direction) retroreflector, when the center of curvature O2 of the outer surface 6b of the partial reflector 6 is shifted in the X-axis direction from the optical axis 10a of the resonator 10B, the laser oscillation of the light reflected by the outer surface 6b of the partial reflector 6 is suppressed under the condition that satisfies the above-mentioned formula (11). That is, by comparing the condition of the formula (5) with the condition of the formula (11), the effect of suppressing the laser oscillation of the light reflected by the outer surface 6b of the partial reflecting mirror 6 is increased by shifting the center of curvature O2 of the outer surface 6b of the partial reflecting mirror 6 in the direction in which the value increases (X-axis direction or Y-axis direction) from the optical axis 10a of the resonator 10B. In addition, 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 the formula (5) or the condition of the formula (11). For example, the outer surface 6b of the partial reflecting mirror 6 may be a toroidal surface or a cylindrical surface. The center of curvature O2 of the outer surface 6b may be located at a position shifted 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).

[0071] Embodiment 4 Next, the laser device 200C according to the fourth embodiment will be described with reference to Figs. 12 to 15. Fig. 12 is a configuration diagram showing a laser processing device 100C including the laser device 200C according to the fourth embodiment. Fig. 13 is a perspective view showing the laser device 200C according to the fourth embodiment. Fig. 14 is a partial enlarged view of Fig. 12, showing the configuration diagram of the resonator 10C of the laser device 200C according to the fourth embodiment. Fig. 15 is a diagram for explaining the operation of the laser device 200C according to the fourth embodiment. Fig. 14 is a view of the resonator 10C of the laser device 200C according to the fourth embodiment, viewed from the positive direction to the negative direction in the Y-axis direction. Figs. 12, 14, and 15 show the apertures 8 and 9 omitted in Fig. 13. This embodiment is different from the second embodiment in that the material of the partial reflector 6 is diamond and the total reflector 7 is a concave mirror. In the fourth embodiment, the same reference numerals are used for the parts overlapping with the first to third embodiments, and the description thereof is omitted. Assuming that the Y-axis direction in FIG. 12 is the up-down direction, the laser device 200C in FIG. 12 is in a state when viewed along the up-down direction, but the laser processing machine 300 in FIG. 12 is in a state when viewed along a direction perpendicular to the up-down direction, and the laser beam r1 and the workpiece 400, which are actually represented by dot hatching, are positioned so that they are located in the negative direction of the Y-axis direction. In FIG. 12, for convenience of explanation, the laser processing machine 300 is shown rotated 90 degrees from the actual state. The directions shown in FIG. 12 are set for convenience of explanation of the laser device 200C and the laser processing machine 300, and do not specify the posture in which the laser device 200C and the laser processing machine 300 are used.

[0072] The material of the partial reflector 6 shown in FIG. 12 to FIG. 15 is diamond. The partial reflector 6 is formed of a thin diamond having a thickness of about 1 mm, for example. The material of the partial reflector 6 contains only diamond in this embodiment, but may 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 reflector 6 shown in FIG. 14 is in a laser gas atmosphere, and the outer surface 6b side of the partial reflector 6 is in the air. That is, at the opening 1a, the partial reflector 6 separates the inside and the outside of the housing 1.

[0073] The laser gas pressure is set to a pressure lower than atmospheric pressure. Since 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. This causes the shape of the partial reflector 6 to change before laser oscillation starts and during laser oscillation. Before laser oscillation starts refers to, for example, 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 starts, the inner surface 6a and outer surface 6b of the partial reflector 6 are flat.

[0074] The inner surface 6a of the partial reflector 6 during laser oscillation is a curved surface having a center of curvature O1 located on the optical axis 10a of the resonator 10C. The inner surface 6a is a convex surface that is convex toward the electrodes 2 and 3 in the Z-axis direction. The outer surface 6b of the partial reflector 6 during laser oscillation is 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 is a concave surface that is concave toward the electrodes 2 and 3 in the Z-axis direction. 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 inner surface 6a with respect to the outer surface 6b. For example, when the laser gas pressure is 200 Torr and the diameter of the diamond is 25.4 mm, the radius of curvature of the inner surface 6a and the outer surface 6b due to pressure distortion is about 55 m. In addition, by partially changing the thickness of the partial reflector 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 located 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 reflecting surface 7a that is concave. The reflecting surface 7a is a concave surface that is concave in the X-axis direction away from the folding mirror 14. In this embodiment, the reflecting surface 14a of the folding mirror 14 is a flat surface, but it may be a concave surface that is 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 reflecting surface 14a of the folding mirror 14 is a toroidal surface or a cylindrical surface, the circularity of the laser beam r1 (see FIG. 12) can be set to an appropriate value. In addition, when the reflecting surface 14a of the folding mirror 14 is a concave surface, the reflecting surface 7a of the total reflection mirror 7 may be a flat surface. That is, the reflecting surface 7a of the total reflection mirror 7 or the reflecting surface 14a of the folding mirror 14 may be a concave surface. In this embodiment, the inner surface 6a of the partial reflecting mirror 6 is convex, and therefore, by giving a 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] 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 shifted from the optical axis 10a of the resonator 10C, and thus the same effect as that of the above-mentioned embodiment 1 can be achieved. 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 direction different from that of the laser beam r1 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 behind 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 part of the laser beam r1 may be reflected and return to the laser device 200 as reflected light r3. 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 shifted from the optical axis 10a of the resonator 10C, so that 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 the reflected light r4, which is a part of the irradiated reflected light r3 that is reflected again, 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 the occurrence of processing defects caused by the reflected light r4 being irradiated onto the workpiece 400. In particular, in this embodiment, as shown in Fig. 15, 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, so that 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 traveling direction of the reflected light r4, the reflected light r4 can be reliably blocked.

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

[0080] Embodiment 5. Next, a laser device 200D according to a fifth embodiment will be described with reference to FIG. 16 and FIG. 17. FIG. 16 is a perspective view showing the laser device 200D according to the fifth embodiment. FIG. 17 is a configuration diagram showing the 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 direction. In FIG. 17, the apertures 8 and 9 omitted in FIG. 16 are illustrated. In this embodiment, the material of the partial reflector 6 is diamond, the total reflector 7 is a one-dimensional retroreflector, and the folding mirror 14 is a concave mirror, which are different from the above-mentioned second embodiment. In addition, in the fifth embodiment, the same reference numerals are attached to the parts overlapping with the above-mentioned first to fourth embodiments, and the description thereof is omitted.

[0081] As shown in Figs. 16 and 17, the configuration of the partial reflector 6 is the same as that of the above-described embodiment 4. The configuration of the total reflector 7 is the same as that of the above-described embodiment 3. As shown in Fig. 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 is concave in the direction away from the electrodes 2 and 3. Since the inner surface 6a of the partial reflector 6 is a convex surface, the reflective surface 14a of the folding mirror 14 is given a curvature, so that the partial reflector 6, the total reflector 7, and the folding mirror 14 form a stable resonator 10D. Note that the thickness of the partial reflector 6 in the direction along the optical axis 10a (the dimension in the Z-axis direction in the illustrated example) may be partially changed to provide a center of curvature O2 of the outer surface 6b at a position shifted from the optical axis 10a of the resonator 10D.

[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 shifted from the optical axis 10a of the resonator 10D, and thus the same effect as in the above-mentioned embodiment 1 can be achieved. That is, even if the light is reflected by the outer surface 6b of the partial reflecting mirror 6 to generate a laser beam r2 by laser oscillation, the laser beam r2 propagates in a direction different from that of the laser beam r1 generated by laser oscillation by reflection by the inner surface 6a of the partial reflecting mirror 6. Therefore, as in the above-mentioned embodiment 4, by filtering only the laser beam r2 in the laser processing machine 300 (see FIG. 12) installed behind the laser device 200D, the laser beam r2 does not reach the workpiece 400 (see FIG. 12), and processing defects caused by the laser beam r2 can be suppressed. Also, in this embodiment, as in the above-mentioned embodiment 4, the occurrence of processing defects caused by the reflected light r4 (see FIG. 12) being irradiated on the workpiece 400 can be suppressed. In addition, in this embodiment, since 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 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 the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0085] 1,300a housing, 1a opening, 2,3 electrode, 4 blower, 5 heat exchanger, 6,520 partial reflector, 6a,520a inner surface, 6b,520b outer surface, 7,530 total reflector, 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 folding 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 mirror used as a partial reflector constituting one end of a resonator; The mirror is an inner surface that is either partially reflective or uncoated for a particular wavelength; an outer surface facing away from the inner surface, the outer surface being coated with a total transmission coating for a particular wavelength; having the inner surface is a curved surface having a center of curvature located on the optical axis of the resonator, 11. A laser device according to claim 10, wherein the outer surface is a curved surface having a center of curvature offset from the optical axis of the resonator.

2. a one-dimensional retroreflector that constitutes the other end of the resonator; 2. The laser device of claim 1, wherein a laser beam is generated along the optical axis of the resonator between the inner surface of the mirror and the total reflection mirror.

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

5. 2. The laser device of claim 1, wherein the outer surface of the mirror is a toroidal surface.

6. 2. The laser device according to claim 1, wherein the outer surface of the mirror is a cylindrical surface.

7. 2. The laser device of claim 1, wherein the material of the mirror comprises diamond.

8. 2. The laser device according to claim 1, wherein the center of curvature of the outer surface is on an opposite side of the inner surface with respect to the outer surface.

9. A mirror used as a partial reflector constituting one end of a resonator, an inner surface that is either partially reflective for a particular wavelength or that has no partially reflective coating; an outer surface facing away from the inner surface, the outer surface being coated with a total transmission coating for a particular wavelength; having the inner surface is a curved surface having a center of curvature located on the optical axis of the resonator, The mirror, wherein the outer surface is a curved surface having a center of curvature offset from the optical axis of the resonator.

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