Laser processing device

Abstract

Laser processing device, comprising the following: a laser oscillator (1) for emitting laser light (L); a worktable (2) for arranging an object to be processed; an optical transmission system for transmitting the laser light (L) emitted from the laser oscillator (1) to the processing table (2); a processing head (4) for focusing and emitting the laser light (L) transmitted via the optical transmission system onto the object to be processed; and a movement device (5) for changing a relative position between the object to be processed and the laser light (L) to be emitted onto the object to be processed, the optical transmission system includes: a reflective beam expansion mechanism (6) for collimating and expanding the laser light (L) from the laser oscillator (1) consisting of three mirrors, namely a spherical mirror (67) with variable curvature, a spherical mirror (63) and a mirror (62) which has different curvatures in two orthogonal axes, and wherein the spherical mirror (67) with variable curvature in the direction of propagation of the laser light (L) is arranged between the spherical mirror (63) and the mirror (62) which has different curvatures in two orthogonal axes.

Description

Technical area

[0001] The present invention relates to a laser processing apparatus for processing an object to be processed by concentrating laser light emitted from a laser oscillator and irradiating it onto the object to be processed. State of the art

[0002] Heretofore, a laser processing apparatus for processing an object to be processed using laser light emitted from a laser oscillator has been well known (see, for example, Patent Document 1).

[0003] Fig. 7 is a block diagram schematically illustrating an optical path configuration of a related art laser processing apparatus described in Patent Document 1.

[0004] In Fig. 7, laser light L generated by a laser oscillator 1 is transmitted via an optical transmission system to a processing lens (not shown) in a processing head 4 to be collimated and irradiated onto an object (not shown) arranged on a processing table 2.

[0005] The processing table 2 and the processing head 4 comprise a movement device 5 capable of moving the processing table 2 and the processing head 4 in at least one axial direction. The movement device 5 can move a relative position between the laser light L and the object to be processed in a desired direction and can arrange the relative position at a desired position.

[0006] In this case, the moving device 5 is designed to move the machining table 2 in an X-axis direction and to move the machining head 4 in a Y-axis direction.

[0007] The optical transmission system for the laser light L includes a reflective beam expansion mechanism 106 into which the laser light L from the laser oscillator 1 enters, and a reflection mirror 8 for introducing the laser light L emitted from the reflective beam expansion mechanism 106 into the processing head 4.

[0008] The reflective beam expanding mechanism 106 includes a reflection mirror 68 into which the laser light L from the laser oscillator 1 enters, a spherical convex mirror 63 into which the laser light L reflected by the reflection mirror 68 enters, and a spherical concave mirror 65 into which the laser light L reflected by the spherical convex mirror 63 enters.

[0009] The reflective beam expansion mechanism 106 enlarges a beam diameter of the laser light L by a desired scale factor regardless of a divergence angle of the laser light L generated by the laser oscillator 1, and maintains a corresponding condensed light diameter at a processing position on the processing table 2.

[0010] It is known that, in general, astigmatism occurs in accordance with an incident angle in light reflected by a spherical mirror such as the spherical convex mirror 63 or the spherical concave mirror 65. Specifically, when astigmatism occurs in laser light L in a laser processing device, the light converging ability is degraded, and the beam shape at the processing location becomes anisotropic.

[0011] In this way, in a laser processing apparatus of the type in which the processing head 4 moves, the reflective beam expanding mechanism 106 is provided for expanding and collimating the laser light L in the optical path to maintain a suitable condensed light diameter at the processing location of the object to be processed. When a spherical mirror is used in the reflective beam expanding mechanism 106, in order to prevent astigmatism, it is necessary to limit the angle of incidence with respect to the spherical mirror to an acute angle.

[0012] Therefore, when a spherical mirror is used in the optical transmission system of the laser processing device, in order to avoid a reduction in processing quality and an occurrence of anisotropy in processing due to astigmatism, it is necessary to limit the incident angle of the laser light L with respect to the spherical mirror to an acute angle so that the astigmatism does not adversely affect the processing quality.

[0013] It is known that, in general, when the angle of incidence with respect to the spherical mirror is set to an acute angle (desirably 15° or less), a reduction in processing quality due to astigmatism is negligible.

[0014] Therefore limited in Fig. 7 (Patent Document 1), the reflection mirror 68 in the reflective beam expanding mechanism 106 sets the angle of incidence of the laser light L with respect to the spherical mirrors (the spherical convex mirror 63 and the spherical concave mirror 65) to acute angles, respectively.

[0015] However, if the reflection mirror 68 is provided to limit the angle of incidence with respect to the spherical mirrors, the optical path becomes complicated, and furthermore, astigmatism cannot be prevented in the strict sense. Furthermore, thermal lensing occurs due to absorption of laser light by optical elements in the complicated optical path, and thus, an increase in the number of optical elements is a factor in generating instability for processing.

[0016] US 5 754 219 A discloses a device for producing a screen printing stencil with a rotatably mounted printing cylinder, a laser for generating a laser beam that can be moved onto the printing cylinder and a focusing optic for focusing the laser beam onto the surface of the printing cylinder.

[0017] US 2008 / 0 259 425 A1, on the other hand, discloses a scanner head for processing a workpiece using a focused laser beam. The lens-based arrangements described therein lead to significant disadvantages, as they comprise, among other things, at least four lenses.

[0018] DE 199 33 825 B4 discloses a reflective beam expansion mechanism suitable for collimating and expanding laser light from a laser oscillator. The described beam expansion mechanism consists of at least four mirrors. Quotation listPatent literature

[0019] Patent Document 1: JP H05-305 473 A Summary of the inventionTechnical problems

[0020] In the related art laser processing apparatus, when the reflective beam expanding mechanism including the spherical mirror is used as the optical transmission system, the reflection mirror for restricting the incident angle with respect to the spherical mirror is provided as in Patent Document 1, but there are problems in that the optical path design is complicated and, further, astigmatism cannot be satisfactorily prevented.

[0021] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to achieve a laser processing apparatus capable of satisfactorily restricting a beam divergence angle and irradiating laser light without aberration and with a desired beam diameter to an object to be processed by using a reflective beam expanding mechanism whose optical path design is not particularly complicated. Solution to the problems

[0022] According to one embodiment of the present invention, there is provided a laser processing apparatus comprising: a laser oscillator for emitting laser light; a processing table for arranging an object to be processed; an optical transmission system for transmitting the light emitted from the laser oscillator to the processing table; a processing head for converging and irradiating the laser light transmitted via the optical transmission system onto the object to be processed;and a moving device for changing a relative position between the object to be processed and the laser light to be irradiated onto the object to be processed, wherein the optical transmission system comprises: a reflective beam expanding mechanism for collimating and expanding the laser light from the laser oscillator consisting of three mirrors, namely a spherical mirror with variable curvature, a spherical mirror, and a mirror having different curvatures in two orthogonal axes, and wherein the spherical mirror with variable curvature is arranged between the spherical mirror and the mirror having different curvatures in two orthogonal axes in the beam propagation direction of the laser light. Advantageous effects of the invention

[0023] According to an embodiment of the present invention, in the reflective beam expanding mechanism constituting the optical transmission system, by using the mirror having different curvatures in two orthogonal axes, the beam divergence angle can be satisfactorily restricted, and the laser light can be irradiated onto the object to be processed without aberration and with a desired beam diameter without using the optical transmission system having a particularly complicated structure. Short description of the drawings Fig. 1 is a block diagram schematically illustrating an optical path configuration of a laser processing apparatus according to a first embodiment not according to the present invention. Fig. 2 is a block diagram schematically illustrating an optical path layout of a laser processing apparatus according to a second embodiment not according to the invention. Fig. 3 is a block diagram schematically illustrating an optical path layout of a laser processing apparatus according to a third embodiment not according to the invention. Fig. 4 is a block diagram schematically illustrating a main part of a laser processing apparatus according to a fourth embodiment not according to the present invention. Fig. 5 is a block diagram schematically illustrating a main part of a laser processing apparatus according to a fifth embodiment of the present invention. Fig. 6 is a block diagram schematically illustrating a main part of a laser processing apparatus according to a sixth embodiment not according to the present invention. Fig. 7 is a block diagram schematically illustrating an optical path layout of a laser processing apparatus according to the related art. Fig. 8 is a structural view schematically illustrating a mirror adjusting mechanism according to a seventh embodiment not according to the present invention. Description of the embodimentsFirst embodiment

[0024] Fig. 1 is a block diagram schematically illustrating an optical path configuration of a laser processing apparatus according to a first embodiment not according to the present invention.

[0025] In Fig. 1, the laser processing apparatus according to the first embodiment includes a laser oscillator 1 that emits laser light L, a processing table 2 on which an object to be processed (not shown) is placed, a transmission optical system including a reflective beam expanding mechanism 6 and a reflection mirror 8, and a processing head 2 that radiates the laser light L that has passed through the transmission optical system to the object to be processed.

[0026] The laser light L emitted from the laser oscillator 1 is collimated and expanded by the reflective beam expanding mechanism 6 provided in the optical transmission system, and is then introduced into the processing head 4 by means of the reflection mirror 8. Thereafter, the laser light L is collimated in the processing head 4 by a processing lens (not shown) and then irradiated onto the object to be processed on the processing table 2.

[0027] The machining table 2 and the machining head 4 are provided with a movement device 5. The movement device 5 moves the machining table 2 and the machining head 4 horizontally in ranges from positions indicated by the solid lines to positions 2' and 4', respectively, indicated by the dashed lines.

[0028] The moving device 5 moves the machining table 2 in an X-axis direction (broken arrow direction) and moves the machining head 4 in a Y-axis direction (broken arrow direction) under the control of a control device (not shown), thereby changing a relative position between the laser light L and the object to be machined to enable machining at a desired machining position.

[0029] It should be noted that in Fig. 1, in order to adjust the relative position between the laser light L and the object to be processed, the moving device 5 is used to change the relative position between the processing table 2 and the processing head 4, but also a moving device can be used to control only the processing head.

[0030] The reflective beam expansion mechanism 6 comprises at least one mirror with different curvatures in two orthogonal axes.

[0031] In Fig. 1, the reflective beam expanding mechanism 6 comprises a spherical convex mirror 63 that reflects the laser light L from the laser oscillator 1, and a concave mirror 62 with different curvatures in two orthogonal axes.

[0032] The two orthogonal axes of the concave mirror 62 have different curvatures from each other, and the concave mirror 62 further reflects the laser light L reflected by the spherical convex mirror 63 to cause the laser light L to enter the reflection mirror 8 on the side of the processing table 2.

[0033] It should be noted that in this case, the concave mirror 62 having different curvatures in two orthogonal axes and the spherical convex mirror 63 are used in the reflective beam expanding mechanism 6, but a convex mirror having different curvatures in two orthogonal axes and a spherical concave mirror may also be used.

[0034] Furthermore, the arrangement order of the concave mirror 62 and the spherical convex mirror 63 is not limited to the Fig. 1, and the arrangement order of the mirrors may be in reverse order.

[0035] It is conceivable to use a spherical convex mirror and a spherical concave mirror as the simplest reflective beam expanding mechanism that collimates and enlarges the beam diameter of the laser light L, but as described above, astigmatism occurs according to an incident angle in light reflected by a spherical mirror, and a processing quality is significantly lowered due to the anisotropic beam shape, and the light converging ability caused by the astigmatism is degraded.

[0036] In the first embodiment, on the other hand, the concave mirror 62 having different curvatures in two orthogonal axes is used in the reflective beam expanding mechanism 6, and the curvatures of the two axes of the concave mirror 62 are designed so as not to cause aberration in the reflected light.

[0037] As a result, no restriction is imposed on the incident angle of the laser light L, and thus an optical path design using the concave mirror 62 as a reflection mirror is possible. Thus, the beam diameter can be expanded and collimated not only without restricting the incident angle at the spherical convex mirror 63, but also without causing astigmatism.

[0038] As described above, the laser processing apparatus according to the first embodiment ( Fig. 1) the laser oscillator 1 for emitting the laser light L, the processing table 2 on which the object to be processed is placed, the optical transmission system for transmitting the laser light L emitted from the laser oscillator 1 to the processing table 2, the processing head 4 for concentrating and radiating the laser light L transmitted via the optical transmission system onto the object to be processed, and the moving device 5 for changing the relative position between the object to be processed and the laser light L to be radiated onto the object to be processed.

[0039] The optical transmission system includes the reflective beam expanding mechanism 6 for collimating and expanding the laser light L from the laser oscillator 1, and the reflective beam expanding mechanism 6 includes a mirror having different curvatures in two orthogonal axes.

[0040] The reflective beam expansion mechanism 6 includes the spherical convex mirror 63 and the concave mirror 62 with different curvatures along two orthogonal axes. Alternatively, the reflective beam expansion mechanism 6 includes a spherical concave mirror and a convex mirror with different curvatures along two orthogonal axes.

[0041] By using a mirror designed such that two of its orthogonal axes have different curvatures from each other to prevent aberration when light is reflected in the reflective beam expanding mechanism 6 for expanding and collimating the laser light L in this way, a beam divergence angle can be satisfactorily restricted, and the laser light L can be irradiated without aberration and with a desired beam diameter onto an object to be processed using the reflective beam expanding mechanism 6 whose optical path design is not particularly complicated.

[0042] Furthermore, no restriction is imposed on the incident angle of the laser light L with respect to the mirror having different curvatures in two orthogonal axes, and thus the design flexibility for the optical path is increased and the optical system is simplified.

[0043] Furthermore, the reflection mirror 68 may be used to adjust the angle of incidence with respect to a spherical mirror as in the device ( Fig. 7) according to the related art are eliminated, and the number of optical elements in the optical transmission system can be reduced to simplify the optical structure. Thus, the influence of the thermal lensing effect of the optical elements is reduced, enabling stable processing over a long period of time.

[0044] It should be noted that in Fig. 1, in order to prevent aberration during reflection, the angle of incidence of the laser light L with respect to the spherical convex mirror 63 is limited to an acute angle. However, if the curvatures of the concave mirror 62 are designed so that an astigmatism that occurs when the concave mirror 62 reflects and an astigmatism of reflected light that occurs in accordance with the angle of incidence with respect to the spherical mirror 63 cancel each other, the angle of incidence of the laser light L with respect to the spherical convex mirror 63 is not limited to an acute angle. Second embodiment

[0045] It should be noted that in the above first embodiment ( Fig. 1) the reflective beam expanding mechanism 6 comprising the concave mirror 62 with different curvatures in two orthogonal axes and the spherical convex mirror 63 is used, but as in Fig. 2, a reflective beam expanding mechanism 6A may also be used, which comprises a convex mirror 61 having different curvatures in two orthogonal axes and the concave mirror 62 having different curvatures in two orthogonal axes.

[0046] Fig. Fig. 2 is a block diagram schematically illustrating an optical path configuration of a laser processing apparatus according to a second embodiment of the present invention. The same components as those described above (see Fig. 1) are designated by the same reference numerals as those described above, and their detailed description is omitted here.

[0047] In Fig. 2, the reflective beam expanding mechanism 6A includes the convex mirror 61 having different curvatures in two orthogonal axes, and the concave mirror 62 having different curvatures in two orthogonal axes.

[0048] In the above-described ( Fig. 1) reflective beam expanding mechanism 6, only one mirror with different curvatures in two orthogonal axes is used, but in the reflective beam expanding mechanism 6A according to the second embodiment ( Fig. 2) two mirrors with different curvatures in two orthogonal axes (convex mirror 61 and concave mirror 62) are used.

[0049] By using two mirrors each with different curvatures along two orthogonal axes in the reflective beam expansion mechanism 6A in this way, no restriction is imposed on the incident angles of the laser light L with respect to the mirrors in the reflective beam expansion mechanism 6A. Thus, the design flexibility for the optical path is increased, and the reflection mirror 68 for restricting the incident angle becomes unnecessary, reducing the influence of the thermal lens effect to stabilize the machining accuracy.

[0050] Furthermore, all the mirrors in the transmission optical system can be used as reflection mirrors, and thus the reflection mirror 8 on the processing table 2 side becomes unnecessary. Thus, the transmission optical system can be further simplified.

[0051] Furthermore, the influence of the thermal lens effect of the optical elements is further reduced, which enables stable processing over a long period of time. Third embodiment

[0052] It should be noted that in the above first and second embodiments ( Fig. 1 and Fig. 2) the machining table 2 movable in the X-axis direction is used, but a fixed machining table 2A can also be used, as in Fig. 3 is shown.

[0053] Fig. Fig. 3 is a block diagram schematically illustrating an optical path configuration of a laser processing apparatus according to a third embodiment of the present invention. The same components as those described above (see Fig. 1 and Fig. 2) are designated by the same reference numerals as those described above, and their detailed description is omitted here.

[0054] In Fig. 3, the machining head 4 on the machining table 2A is provided with a moving device 5A for moving the machining head 4 in the X-axis direction and the Y-axis direction in ranges from the position indicated by the solid lines to positions 4' indicated by the broken lines.

[0055] Furthermore, in the optical transmission system for the laser light L, a mechanism 7 for setting the optical path length between the reflective beam expanding mechanism 6A and the reflection mirror 8 on the side of the processing table 2A is used.

[0056] In this case, the machining table 2A is larger than the above-described machining table 2 and has a machining area larger than that of the machining table 2. It is not efficient to drive the machining table 2A, and therefore the moving device 5A changes the relative position between the laser light L and an object to be machined only by driving the machining head 4.

[0057] It should be noted that when the machining head 4 is moved in the Y-axis direction, a reflection mirror 28 is also moved in a range from a position indicated by the solid lines to a position 28' indicated by the broken lines.

[0058] Furthermore, in this state, an optical path length of the laser light L from the laser oscillator 1 to the machining head varies greatly depending on a machining position on the machining table 2A, which may cause an error in the condensed light diameter of a beam irradiated onto an object to be machined. Therefore, the optical path length setting mechanism 7 is provided to compensate for fluctuations in the optical path length.

[0059] The optical path length setting mechanism 7 includes a mirror group 78 including a plurality of mirrors for causing a direction of incident light and a direction of outgoing light to be opposite and parallel to each other.

[0060] Furthermore, the optical path length setting mechanism 7 includes a movement mechanism 79 for translationally displacing the mirror group 78 in a range from a position indicated by the solid lines to a position 78' indicated by the broken lines.

[0061] The moving mechanism 79, under the control of the control device (not shown), adjusts the optical path length of the laser light L so that it is always at a predetermined value by moving the position of the mirror group 78 so as to cancel out a change in the optical path length caused by the movement of the processing head 4.

[0062] It should be noted that in Fig. 3, the optical path length setting mechanism 7 is used with respect to the processing table 2A, which changes the relative position between the laser light L and an object to be processed only by moving the processing head 4, but the optical path length setting mechanism 7 can also be applied to a configuration in which both the processing head 4 and the processing table 2 are as described above ( Fig. 1 and Fig. 2) be moved.

[0063] Further, a case is described in which the reflective beam expanding mechanism 6A according to the above-mentioned second embodiment ( Fig. 2), but this embodiment can be similarly applied to a case where the reflective beam expanding mechanism 6 according to the above-mentioned first embodiment ( Fig. 1) is used.

[0064] The laser light L emitted from the reflective beam expansion mechanism 6A is collimated, and thus, ideally, the condensate diameter of the laser light L irradiated onto a workpiece to be processed located on the processing table 2A does not change even if the optical path length changes. However, in a strict sense, it is impossible to completely restrict the divergence angle, and thus, an increase in the condensate diameter accompanying the increase in the optical path length cannot be completely avoided.

[0065] However, as in Fig. 3, the optical path length fixing mechanism 7 is employed, even a laser processing apparatus using the large processing table 2A which causes the optical path length to be longer can maintain a fixed condensate diameter on the processing table 2A, and the processing quality can be maintained.

[0066] As described above, the optical transmission system according to the third embodiment ( Fig. 3) the optical path length setting mechanism 7, and the optical path length setting mechanism 7 includes the mirror group 78 composed of a plurality of mirrors and the moving mechanism 79 for translating the mirror group 78. The plurality of mirrors constituting the mirror group 78 are arranged such that the direction of light incident on the mirror group 78 and the direction of light emerging from the mirror group 78 are opposite and parallel to each other.

[0067] Furthermore, the moving mechanism 79 translates the mirror group 78 with respect to the directions of the incident light and the outgoing light to cancel a change in the relative position between the laser light L to be irradiated onto an object to be processed and the object to be processed, in order to maintain a fixed optical path length of the laser light L irradiated onto the object to be processed.

[0068] The optical path length fixing mechanism 7 is provided in this way, and therefore, the condensed light diameter of the laser light L irradiated onto an object to be processed can be maintained regardless of the relative position between the laser light L and the object to be processed, and thus high-quality processing can be maintained. Fourth embodiment

[0069] It should be noted that in the above third embodiment ( Fig. 3) the reflective beam expanding mechanism 6A is used, which comprises the convex mirror 61 with different curvatures in two orthogonal axes and the concave mirror 62 with different curvatures in two orthogonal axes, but as in Fig. 4, a reflective beam expanding mechanism 6B may also be used, which comprises the concave mirror 62 with different curvatures in two orthogonal axes, the spherical convex mirror 63, a spherical mirror 67 with variable curvature and the reflection mirror 68.

[0070] Fig. Fig. 4 is a block diagram schematically illustrating a main part of a laser processing apparatus according to a fourth embodiment not according to the present invention. The same components as those described above (see Fig. 1 to Fig. 3) are designated by the same reference numerals as those described above, and their detailed description is omitted here.

[0071] In Fig. 4, the reflective beam expanding mechanism 6B according to the fourth embodiment includes, as a transmission optical system, the spherical mirror 67 with variable curvature that reflects the laser light L from the laser oscillator 1, the reflection mirror 68 that reflects the laser light L reflected by the spherical mirror 67 with variable curvature, and the convex mirror 61 and the concave mirror 62 that reflect the laser light L reflected by the reflection mirror 68. Two orthogonal axes of each of the convex mirror 61 and the concave mirror 62 have curvatures different from each other.

[0072] The concave mirror 62 having different curvatures in two orthogonal axes reflects the laser light L reflected by the convex mirror 63 having different curvatures in two orthogonal axes and introduces it into the optical path length setting mechanism 7.

[0073] It should be noted that the arrangement order of the spherical mirror 67 with variable curvature and the reflection mirror 68 is not limited to the Fig. 4 is limited and the arrangement sequence of the mirrors can be set in the reverse order.

[0074] With the reflection mirror 68, it is possible to restrict the angle of incidence of the laser light L with respect to the spherical mirror 67 with variable curvature to a range in which the processing quality is not affected in order to prevent astigmatism occurring in the laser light L reflected by the spherical mirror 67 with variable curvature.

[0075] In the above-mentioned first to third embodiments ( Fig. 1 to Fig. 3) the condensed light diameter of the laser light L at a processing point on an object to be processed is invariable, but by using the spherical mirror 67 with variable curvature in the reflective beam expanding mechanism 6B as in Fig. 4, the condensation diameter of the laser light can be changed.

[0076] In general, in drilling machining such as piercing machining, machining can be performed at a higher speed compared to the case where the condensate diameter is fixed by appropriately changing the condensate diameter during machining.

[0077] Furthermore, when machining a corner portion or the like, heat tends to accumulate in the object to be machined and a cut surface may become rough, but by changing the condensate diameter during machining to change the radiation area of ​​the laser light to the object to be machined, high-quality and high-accuracy machining can be performed.

[0078] As described above, the optical transmission system according to the fourth embodiment ( Fig. 4) the spherical mirror 67 with variable curvature and can change the condensation diameter of the laser light L radiated onto an object to be processed, and therefore processing with a higher speed and a higher quality can be realized. Fifth embodiment

[0079] It should be noted that in the above-mentioned fourth embodiment ( Fig. 4) the reflective beam expanding mechanism 6B is used, which has the reflection mirror 68, but as in Fig. 5, a reflective beam expanding mechanism 6C can also be used, which does not require the reflection mirror 68.

[0080] Fig. Fig. 5 is a block diagram schematically illustrating a main part of a laser processing apparatus according to a fifth embodiment of the present invention. The same components as those described above (see Fig. 4) are designated by the same reference numerals as those described above, and their detailed description is omitted here.

[0081] In Fig. 5, the reflective beam expanding mechanism 6C according to the fifth embodiment of the present invention includes, as a transmission optical system, the spherical convex mirror 63 that reflects the laser light L from the laser oscillator 1, the spherical mirror 67 with variable curvature that reflects the laser light L reflected by the spherical convex mirror 63, and the concave mirror 62 with different curvatures in two orthogonal axes.

[0082] The spherical convex mirror 63 and the spherical variable curvature mirror 67 are arranged substantially opposite to each other so that the laser light L having entered the corresponding mirror is emitted in an opposite direction.

[0083] The concave mirror 62 reflects the laser light L reflected by the spherical mirror 67 with variable curvature to guide the laser light L to the side of the optical path length setting mechanism 7.

[0084] The above-described ( Fig. 4) The reflective beam expanding mechanism 6B requires the reflection mirror 68 to restrict the angle of incidence with respect to the spherical mirror 67 with variable curvature to prevent astigmatism. Fig. The reflective beam expanding mechanism 6C shown in Fig. 5 does not need the reflection mirror 68 because the spherical convex mirror 63 is arranged on an incident side of the spherical variable curvature mirror 67, and the spherical variable curvature mirror 67 and the spherical convex mirror 63 are arranged opposite to each other.

[0085] What is special is that the Fig. 5 is used, the reflection mirror 68 is unnecessary, and the incident angles of the laser light L with respect to the spherical variable curvature mirror 67 and the spherical convex mirror 63 can be limited to a range in which astigmatism does not affect the processing quality.

[0086] Furthermore, the simplification of the optical transmission system reduces the influence of thermal lenses on the optical elements, thus enabling stable processing. Furthermore, the simplification of the optical transmission system increases the design flexibility of the optical path.

[0087] As described above, the reflective beam expanding mechanism 6C according to the fifth embodiment ( Fig. 5) of the present invention, the spherical mirror 67 with variable curvature and the spherical convex mirror 63 (spherical mirror), and the spherical mirror 67 with variable curvature is arranged opposite to the spherical convex mirror 63 in the reflective beam expanding mechanism 6C.

[0088] This improves the machining accuracy as described above, and by arranging the spherical convex mirror 63 and the spherical variable curvature mirror 67 opposite each other, the reflection mirror 68 becomes unnecessary to limit the incident angles of the laser light L to acute angles with respect to the mirrors, respectively. Thus, machining can be stabilized by simplifying the optical path and reducing the thermal lensing effect. Sixth embodiment

[0089] It should be noted that in the above fifth embodiment ( Fig. 5) the reflective beam expanding mechanism 6C is used, which comprises the concave mirror 62 having different curvatures in two orthogonal axes and the spherical mirror 67 with variable curvature, but as in Fig. 6, a reflective beam expanding mechanism 6D may also be used, which includes a variable curvature mirror 64 having variable curvatures in two orthogonal axes.

[0090] Fig. Fig. 6 is a block diagram schematically illustrating a main part of a laser processing apparatus according to a sixth embodiment not according to the present invention. The same components as those described above (see Fig. 5) are designated by the same reference numerals as those described above, and their detailed description is omitted here.

[0091] In Fig. 6, the reflective beam expanding mechanism 6D according to the sixth embodiment includes, as a transmission optical system, the spherical convex mirror 63 that reflects the laser light L from the laser oscillator 1, and the variable curvature mirror 64 that has variable curvatures in two orthogonal axes.

[0092] The variable curvature mirror 64, which has variable curvatures in two orthogonal axes, has the function of both the concave mirror 62, which has different curvatures in two orthogonal axes, and the previously described ( Fig. 5) spherical convex mirror 67 with variable curvature, and the variable curvature mirror 64 reflects the laser light L reflected by the spherical convex mirror 63 to guide the laser light L to the side of the optical path length setting mechanism 7.

[0093] By Fig. By using the reflective beam expansion mechanism 6D shown in Figure 6, the optical transmission system is simplified and the number of optical elements is reduced. Thus, the influence of thermal lenses can be further reduced and stable processing can be achieved. Furthermore, the optical transmission system is simplified, and thus the design flexibility of the optical path can be increased.

[0094] As described above, the reflective beam expanding mechanism 6D according to the sixth embodiment ( Fig. 6) The variable curvature mirror 64, which has variable curvatures along two orthogonal axes. The variable curvature mirror 64 allows both the mirror with different curvatures along two orthogonal axes and the spherical mirror with variable curvature described above to be combined into a single optical element.

[0095] Therefore, the number of optical elements can be reduced and the stabilization of the machining accuracy can be achieved by simplifying the optical path and reducing the thermal lens effect. Seventh embodiment

[0096] It should be noted that the convex mirror 61 having different curvatures in two orthogonal axes and the concave mirror 62 having different curvatures in two orthogonal axes of the above-mentioned first to sixth embodiments ( Fig. 1 to Fig. 6) in a Fig. 8 can be provided with the mirror adjustment mechanism 90 shown.

[0097] In Fig. 8, the mirror adjusting mechanism 90 includes a mechanism that can move a fixed mirror in a horizontal direction and in a vertical direction and rotate the fixed mirror in a mirror plane about a center of the mirror by using a horizontal direction adjusting screw 91, a vertical direction adjusting screw 92, and a rotation direction adjusting screw 93.

[0098] The convex mirror 61 and the concave mirror 62, each having different curvatures along two orthogonal axes, have curvatures with less precision around their edges due to the difficulty of accurately machining a spherical surface. Thus, it is desired to radiate the laser light L toward the vicinity of their centers. However, a transmission line of the laser light L changes depending on the thermal loads of the optical transmission system and oscillator, and environmental changes such as temperature or humidity.

[0099] Furthermore, when an incident plane of the laser light L deviates from an axis along which the curvature is designed, a beam has a shape of a revolution ellipsoid and the machining quality is lowered.

[0100] Through the Fig.According to the mirror adjustment mechanism 90 shown in Figure 8, even if the transmission line of the laser light L changes, the laser light L is irradiated onto the centers of the convex mirror 61 and the concave mirror 62, each having different curvatures along two orthogonal axes, and the laser light can be transmitted without distorting the beam shape. Note that in this embodiment, the mirror adjustment mechanism 90 is a mechanism that performs adjustment using the horizontal direction adjustment screw 91, the vertical direction adjustment screw 92, and the rotation direction adjustment screw 93, but a piezoelectric element may be used instead of a screw.

Claims

[1] Laser processing device comprising: a laser oscillator (1) for emitting laser light (L); a processing table (2) for arranging an object to be processed; an optical transmission system for transmitting the laser light (L) emitted from the laser oscillator (1) to the machining table (2); a processing head (4) for bundling and radiating the laser light (L) transmitted via the optical transmission system onto the object to be processed; and a movement device (5) for changing a relative position between the object to be processed and the laser light (L) to be radiated onto the object to be processed, wherein the optical transmission system comprises: a reflective beam expanding mechanism (6) for collimating and expanding the laser light (L) from the laser oscillator (1) consisting of three mirrors, namely a spherical mirror (67) with variable curvature, a spherical mirror (63) and a mirror (62) having different curvatures in two orthogonal axes, and wherein the spherical mirror (67) with variable curvature in the beam propagation direction of the laser light (L) is arranged between the spherical mirror (63) and the mirror (62) which has different curvatures in two orthogonal axes. [2] The laser processing apparatus according to claim 1, wherein the reflective beam expanding mechanism (6) comprises a spherical convex mirror (63) and a concave mirror (62) having different curvatures in two orthogonal axes. [3] The laser processing apparatus according to claim 1, wherein the reflective beam expanding mechanism (6) comprises a spherical concave mirror and a convex mirror having different curvatures in two orthogonal axes. [4] Laser processing device according to one of claims 1 to 3, wherein the optical transmission system comprises a mechanism (7) for determining the optical path length, wherein the mechanism (7) for determining the optical path length comprises a mirror group (78) containing a plurality of mirrors and a movement mechanism (79) for translationally moving the mirror group, wherein the plurality of mirrors of the mirror group (78) are arranged such that a direction of light incident on the mirror group (78) and a direction of light emerging from the mirror group (78) are opposite and parallel to each other, and wherein the moving mechanism (79) translates the mirror group (78) with respect to the direction of travel of the incident light and the direction of travel of the outgoing light to cancel a change in a relative position between the object to be processed and the laser light (L) to be irradiated onto the object to be processed, in order to maintain a fixed optical path length of the laser light (L) irradiated onto the object to be processed. [5] The laser processing apparatus according to any one of claims 1 to 4, wherein the spherical mirror (67) with variable curvature is arranged to oppose the spherical mirror in the reflective beam expanding mechanism (6). [6] The laser processing apparatus according to any one of claims 1 to 5, wherein the reflective beam expanding mechanism (6) comprises a variable curvature mirror having variable curvatures in two orthogonal axes. [7] Laser processing apparatus according to one of claims 1, 2, 4, 5, wherein the reflective beam expanding mechanism (6) comprises: a spherical convex mirror; and a concave mirror (62) having different curvatures in two orthogonal axes, wherein the spherical convex mirror and the spherical mirror (67) with variable curvature are arranged opposite each other, and wherein the spherical mirror (67) with variable curvature and the concave mirror (62) having different curvatures in two orthogonal axes are arranged opposite each other.

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