Laser processing apparatus

Abstract

This laser processing apparatus (1D) comprises a laser oscillator (2) that emits a laser beam (r), an acoustic optical element (4) that refracts the laser beam (r), and an angle filter (6) that separates first-order light from at least one of zero-order light and second-order light within the laser beam (r) emitted from the acoustic optical element (4). The angle filter (6) is configured so that the transmission rate of the first-order light being transmitted through the angle filter (6) is higher than at least one of the transmission rate of the zero-order light being transmitted through the angle filter (6) and the transmission rate of the second-order light being transmitted through the angle filter (6).

Description

Laser Processing Equipment

[0001] The present disclosure relates to a laser processing apparatus that processes a workpiece by irradiating the workpiece with a laser beam.

[0002] Conventionally, laser processing devices have been known that include a laser oscillator, a galvanometer, a condenser lens, and a table. In such laser processing devices, a laser beam emitted from the laser oscillator is reflected by a galvanometer mirror of the galvanometer and then irradiated onto the workpiece by the condenser lens, thereby processing the workpiece held on the table. Since the area that can be scanned by the galvanometer on the workpiece, i.e., the scan area, is limited to several tens of millimeters square, the entire area of ​​the workpiece is processed by moving the table that holds the workpiece and switching the scan area.

[0003] A galvanometer is characterized by a narrow scan area but a fast operating speed. On the other hand, a table is characterized by a slower operating speed than a galvanometer but a wider range of movement than the galvanometer's scan area. Therefore, after the workpiece is machined at high speed in the scan area that can be scanned by the galvanometer, the table is moved by the size of the scan area where the workpiece was machined, and the workpiece is again machined at high speed in the scan area that can be scanned by the galvanometer. By repeating this series of operations, the machining time required to machine the entire area of ​​the workpiece is reduced.

[0004] In order to further shorten the processing time, an acousto-optic element is disposed between the laser oscillator and the galvanometer on the optical path of the laser beam, and the acousto-optic element, the galvanometer, and the table are combined to change the irradiation position of the laser beam on the workpiece, as disclosed in Patent Document 1. The acousto-optic element has a narrower scanning area than the scanning area of ​​the galvanometer and the moving range of the table, but is characterized by a faster operating speed than the galvanometer and the table.

[0005] Generally, the diffraction efficiency of an acousto-optical element, which is a diffraction grating, is 80% to 90%. In other words, when a laser beam is incident on an acousto-optical element, in addition to first-order light, zero-order light and second-order light also exit the acousto-optical element. If the zero-order light and second-order light reach the surface of the workpiece, undesired portions of the workpiece may be processed, resulting in processing defects.

[0006] As a method for avoiding such a problem, Japanese Patent Application Laid-Open No. 2003-144999 discloses a method for blocking the zero-order light emitted from the acousto-optic element with a blocking plate.

[0007] Japanese Patent Application Laid-Open No. 2003-136270

[0008] However, the angular difference between the zeroth-order light and the first-order light emitted from the acousto-optic element is usually about 10 mrad to 100 mrad, and in order to block only the zeroth-order light using the method disclosed in Patent Document 1, the blocking plate needs to be separated from the acousto-optic element by about 1 m, which causes problems such as an increase in the size of the laser processing device and a lengthened optical path.

[0009] The present disclosure has been made in consideration of the above, and aims to provide a laser processing apparatus that can suppress processing defects on the workpiece caused by zero-order light and second-order light emitted from an acousto-optical element, while suppressing an increase in the size of the laser processing apparatus and an increase in the length of the optical path compared to conventional apparatuses.

[0010] In order to solve the above-mentioned problems and achieve the object, the laser processing apparatus according to the present disclosure includes a laser oscillator that emits a laser beam, an acousto-optic element that diffracts the laser beam emitted from the laser oscillator, and an angle filter that separates the laser beam emitted from the acousto-optic element into first-order light and at least one of zeroth-order light and second-order light, The angle filter is configured so that the transmittance of the first-order light passing through the angle filter is higher than at least one of the transmittance of the zeroth-order light and the transmittance of the second-order light passing through the angle filter.

[0011] The laser processing apparatus according to the present disclosure has the advantage of being able to suppress processing defects in the workpiece caused by the zero-order light and second-order light emitted from the acousto-optic element, while suppressing the increase in size of the laser processing apparatus and the lengthening of the optical path compared to conventional apparatuses.

[0012] a perspective view showing a laser processing apparatus according to a first embodiment; a diagram for explaining the action of the angular filter of the first embodiment; an enlarged view of part A shown in FIG. 2; a diagram showing the relationship between the angle of incidence of a laser beam and the diffraction efficiency in the angular filter of the first embodiment; a perspective view showing an example of a method for absorbing the zeroth-order light and the second-order light emitted from an acousto-optic element; a diagram for explaining the action of the angular filter of a modified example of the first embodiment; a perspective view showing a laser processing apparatus according to a second embodiment; a perspective view showing an angular filter of the second embodiment; a diagram for explaining the action of the angular filter of the second embodiment, and a cross-sectional view of the angular filter; a perspective view showing an angular filter of a modified example 1 of the second embodiment; a perspective view showing an angular filter of a modified example 2 of the second embodiment; a perspective view showing a laser processing apparatus according to a third embodiment; a cross-sectional view of the angular filter of the third embodiment; 14 is an enlarged view of the area surrounded by the thick dashed line in FIG. 14; 15 is a transmission spectrum diagram showing the relationship between the wavelength and transmittance of the angular filter of the third embodiment at the incident angle of the transmission peak of the primary light shown in FIG. 15; 16 is an enlarged view of the area surrounded by the thick dashed line in FIG. 16; 17 is a perspective view of a laser processing apparatus according to the fourth embodiment; 18 is a diagram for explaining the action of the angular filter of the fourth embodiment; 19 is an angle characteristic diagram showing the relationship between the incident angle to the wave plate of the angular filter of the fourth embodiment at the wavelength of the laser beam and the transmittance when the thickness of the wave plate is appropriately set; 20 is an enlarged view of the area surrounded by the thick dashed line in FIG. 20;

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser processing apparatus according to an embodiment will be described in detail below with reference to the accompanying drawings.

[0014] First Embodiment. Figure 1 is a perspective view showing a laser processing apparatus 1 according to a first embodiment. The laser processing apparatus 1 processes a workpiece 11 by irradiating the workpiece 11 with a laser beam r. Processing includes, for example, drilling and marking. The workpiece 11 is, for example, a substrate. The laser processing apparatus 1 includes a laser oscillator 2, a mirror 3, a plurality of acousto-optic elements 4, a plurality of half-wave plates 5, a plurality of angle filters 6, a plurality of dampers 7, a plurality of galvanometers 8, a condenser lens 9, and a table 10. In addition to the mirror 3, the laser processing apparatus 1 also includes a plurality of mirrors (not shown).

[0015] The laser beam r emitted from the laser oscillator 2 is reflected by a mirror 3 and passes through an acousto-optical element 4, a half-wave plate 5, and an angular filter 6. The laser beam r is then reflected by a galvanometer 8, positioned above a workpiece 11 by a condenser lens 9, and irradiated onto the workpiece 11. The workpiece 11 irradiated with the laser beam r is burned, melted, or sublimated. As a result, the workpiece 11 is subjected to processing such as drilling and marking. In the following description, directions will be described in accordance with the X-axis, Y-axis, and Z-axis directions shown in FIG. 1. The X-axis and Y-axis directions shown in FIG. 1 are parallel to the horizontal direction and perpendicular to each other. The Z-axis direction shown in FIG. 1 is vertical and perpendicular to the X-axis and Y-axis directions.

[0016] The laser oscillator 2 serves to emit a laser beam r. The mirror 3 serves to reflect the laser beam r emitted from the laser oscillator 2 toward the acousto-optic element 4.

[0017] The acousto-optic element 4 diffracts the laser beam r emitted from the laser oscillator 2 to emit first-order light. The acousto-optic element 4 is a diffraction grating that changes the diffraction direction of the laser beam r. When ultrasonic waves are applied to the acousto-optic element 4, a change in refractive index occurs due to compressional waves within the transparent material through which the laser beam r passes. The diffraction direction of the laser beam r can be changed by modulating the frequency of the ultrasonic waves applied to the acousto-optic element 4. However, the acousto-optic element 4 also emits unwanted zero-order and second-order light in addition to the first-order light. The transparent material is, for example, a glass material such as germanium, quartz, or synthetic quartz. In this embodiment, there are two acousto-optic elements 4. The two acousto-optic elements 4 are arranged at an interval on the optical path of the laser beam r. In the following description, when distinguishing between the two acousto-optic elements 4, they will be referred to as acousto-optic element 4a and acousto-optic element 4b.

[0018] The acousto-optic element 4a is applied with ultrasonic waves to diffract the laser beam r emitted from the laser oscillator 2. The acousto-optic element 4a changes the irradiation position of the laser beam r on the workpiece 11 in the X-axis direction. The acousto-optic element 4b is applied with ultrasonic waves to diffract the laser beam r emitted from the acousto-optic element 4a. The acousto-optic element 4b changes the irradiation position of the laser beam r on the workpiece 11 in the Y-axis direction. The laser processing apparatus 1 can change the irradiation position of the laser beam r on the workpiece 11 in the X-axis direction and the Y-axis direction using the two acousto-optic elements 4a and 4b. The laser processing apparatus 1 can scan an area of ​​0.1 mm to several mm square on the workpiece 11 at a speed of several hundred m / s using the two acousto-optic elements 4a and 4b.

[0019] The half-wave plate 5 serves to rotate the polarization direction of the laser beam r emitted from the acousto-optic element 4 or the angular filter 6 by 90 degrees around the optical axis of the laser beam r. The half-wave plate 5 may be made of any birefringent material. The birefringent material may be, for example, quartz. In this embodiment, there are two half-wave plates 5. In the following description, when the two half-wave plates 5 need to be distinguished, they will be referred to as half-wave plate 5a and half-wave plate 5b. The half-wave plate 5a is disposed between the multiple acousto-optic elements 4a and 4b. The half-wave plate 5a serves to rotate the polarization direction of the laser beam r emitted from the acousto-optic element 4a by 90 degrees around the optical axis of the laser beam r. The half-wave plate 5b is disposed between the multiple angular filters 6a and 6b. The half-wave plate 5b serves to rotate the polarization direction of the laser beam r emitted from the angle filter 6a by 90 degrees around the optical axis of the laser beam r.

[0020] The angular filter 6 serves to separate the desired laser beam r, which is the first-order light, from the undesired zeroth-order light and second-order light, among the laser beam r emitted from the acousto-optical element 4. In this embodiment, there are two angular filters 6. The two angular filters 6 are arranged at an interval on the optical path of the laser beam r. In the following description, the two angular filters 6 are referred to as angular filter 6a and angular filter 6b when distinguishing between them. The angular filter 6a diffracts the first-order light of the laser beam r emitted from the acousto-optical element 4a. The zeroth-order light and second-order light pass through the angular filter 6a without being diffracted by the angular filter 6a. The first-order light emitted from the angular filter 6a passes through the half-wave plate 5b and enters the angular filter 6b. The angular filter 6b diffracts the first-order light emitted from the acousto-optical element 4b. The zeroth-order light and second-order light pass through the angular filter 6b without being diffracted by the angular filter 6b. The angle filter 6 will be described in detail later.

[0021] The damper 7 serves to absorb the zeroth-order and second-order light of the laser beam r emitted from the acousto-optical device 4. In this embodiment, there are two dampers 7. In the following description, when the two dampers 7 need to be distinguished, they will be referred to as damper 7a and damper 7b. The damper 7a is disposed near the angle filter 6a and absorbs the zeroth-order and second-order light of the laser beam r emitted from the acousto-optical device 4a. The damper 7b is disposed near the angle filter 6b and absorbs the zeroth-order and second-order light of the laser beam r emitted from the acousto-optical device 4b.

[0022] The galvanometer 8 serves to reflect the laser beam r emitted from the angular filter 6. In this embodiment, there are two galvanometers 8. The two galvanometers 8 are arranged at an interval on the optical path of the laser beam r. In the following description, when it is necessary to distinguish between the two galvanometers 8, they will be referred to as galvanometer 8a and galvanometer 8b. The galvanometer 8 has a galvanometer mirror 8c that reflects the laser beam r and a galvanometer motor 8d that rotates the galvanometer mirror 8c.

[0023] The galvanometer 8a rotates the galvanometer mirror 8c within a specific range of oscillation angle, thereby changing the irradiation position of the laser beam r on the workpiece 11 in the X-axis direction. The galvanometer 8b rotates the galvanometer mirror 8c within a specific range of oscillation angle, thereby changing the irradiation position of the laser beam r on the workpiece 11 in the Y-axis direction. The laser processing apparatus 1 can change the irradiation position of the laser beam r on the workpiece 11 in the X-axis direction and the Y-axis direction using the two galvanometers 8a and 8b. The laser processing apparatus 1 can scan an area of ​​several tens of millimeters square on the workpiece 11 at a speed of several meters per second using the two galvanometers 8a and 8b.

[0024] The condenser lens 9 serves to condense the laser beam r reflected by the galvanometer 8 and irradiate the workpiece 11. The condenser lens 9 is an fθ lens. The condenser lens 9 irradiates the condensed laser beam r perpendicularly onto the workpiece 11.

[0025] The table 10 holds the workpiece 11 and also serves to move the position of the workpiece 11. The table 10 holds the workpiece 11 by, for example, suctioning the workpiece 11. In this embodiment, the table 10 is movable in the X-axis and Y-axis directions, allowing the workpiece 11 to be moved in the X-axis and Y-axis directions. The table 10 has a drive mechanism and a guide mechanism (not shown). The drive mechanism is, for example, a ball screw. The guide mechanism is, for example, an LM Guide (registered trademark). The laser processing apparatus 1 can change the irradiation position of the laser beam r on the workpiece 11 in the X-axis and Y-axis directions using the table 10. The laser processing apparatus 1 can scan an area of ​​several hundred mm by several hundred mm square on the workpiece 11 at a speed of approximately 1 m / s using the table 10. Note that the table 10 may be movable in only one of the X-axis and Y-axis directions.

[0026] The laser processing apparatus 1 can change the irradiation position of the laser beam r on the workpiece 11 using the acousto-optic element 4, the galvanometer 8, and the table 10. The acousto-optic element 4, the galvanometer 8, and the table 10 constitute a beam scanning mechanism that changes the irradiation position of the laser beam r on the workpiece 11. The acousto-optic element 4 has a narrower scan area than the scan area of ​​the galvanometer 8 and the movement range of the table 10, but is characterized by a faster operating speed than the galvanometer 8 and the table 10. The galvanometer 8 has a wider scan area than the scan area of ​​the acousto-optic element 4 and a narrower scan area than the movement range of the table 10, but is characterized by a slower operating speed than the acousto-optic element 4 and a faster operating speed than the table 10. The table 10 has a slower operating speed than the acousto-optic element 4 and the galvanometer 8, but is characterized by a wider movement range than the scan areas of the acousto-optic element 4 and the galvanometer 8.

[0027] Next, the angle filter 6 of this embodiment will be described in detail with reference to Figures 2 and 3. Figure 2 is a diagram for explaining the operation of the angle filter 6 of embodiment 1. Figure 3 is an enlarged view of part A shown in Figure 2.

[0028] 2, the angular filter 6 is a transmission type diffraction grating that transmits the incident laser beam r to generate diffracted light. More specifically, the angular filter 6 is a transmission type diffraction grating that diffracts the first-order light rp so that the angular difference between the zeroth-order light ro and the first-order light rp emitted from the acousto-optical element 4 becomes large when the zeroth-order light ro and the first-order light rp pass through the angular filter 6, and so that the angular difference between the first-order light rp and the second-order light rq emitted from the acousto-optical element 4 becomes large when the first-order light rp and the second-order light rq pass through the angular filter 6. The angular filter 6 is a blazed diffraction grating that can obtain the maximum diffraction efficiency for the diffracted light of the first-order light rp.

[0029] Generally speaking, if a diffraction grating is designed by specifying the direction of incidence of a laser beam incident on the diffraction grating and the direction of emission of first-order light from the diffraction grating, the diffraction efficiency of first-order light can be increased to 95% or more. Furthermore, the angular difference between the zeroth-order light and the first-order light emitted from the diffraction grating can be increased, for example, to 10 degrees or more. The angular difference between the zeroth-order light ro and the first-order light rp emitted from the acousto-optical element 4 and the angular difference between the first-order light rp and the second-order light rq are generally 0.1 degrees to several degrees. Therefore, in this embodiment, when the zeroth-order light ro and the second-order light rq emitted from the acousto-optical element 4 pass through the angular filter 6, the zeroth-order light ro and the second-order light rq pass through without being diffracted, and when the first-order light rp emitted from the acousto-optical element 4 passes through the angular filter 6, the first-order light rp is diffracted. This increases the angular difference between the zeroth-order light ro and the first-order light rp and the first-order light rp and the second-order light rq.

[0030] The angle filter 6 is a plate-shaped member. In the following description, the direction perpendicular to the thickness direction of the angle filter 6 shown in FIG. 3 is referred to as the vertical direction. Furthermore, a line along the vertical direction passing through the center of the thickness direction of the angle filter 6 is referred to as the center line C. The angle filter 6 includes a surface 6c on which the laser beam r is incident and a back surface 6d from which the laser beam r is emitted. The surface 6c is one surface of the angle filter 6 in the thickness direction. The back surface 6d is the other surface of the angle filter 6 in the thickness direction. For simplicity, the surface 6c and the back surface 6d of the angle filter 6 are assumed to be linearly symmetrical with respect to the center line C. A grating pattern 6e is provided at regular intervals on the surface 6c and the back surface 6d. That is, a plurality of grooves 6f forming the grating pattern 6e are engraved on each of the surface 6c and the back surface 6d.

[0031] The groove 6f is composed of a step surface 6g and a blazed surface 6h. The step surface 6g extends in the plate thickness direction. The blazed surface 6h is inclined so as to approach the center line C as it extends vertically from the tip of the step surface 6g. The period T, which is the vertical distance of the groove 6f, is constant. The shapes of the front surface 6c and back surface 6d of the angle filter 6 are such that only the first-order light rp can be diffracted, but the zeroth-order light ro and the second-order light rq cannot be diffracted. The zeroth-order light ro and the second-order light rq are emitted from the back surface 6d at the same angle at which they were incident on the front surface 6c.

[0032] Next, the operation of the angular filter 6 of embodiment 1 will be described with reference to FIG. 3 . Here, it is assumed that the zeroth-order light ro, the first-order light rp, and the second-order light rq are incident on the same blaze surface 6i on the surface 6c of the angular filter 6. In FIG. 3 , for ease of understanding, the zeroth-order light ro, the first-order light rp, and the second-order light rq are each depicted by a single line. In reality, the zeroth-order light ro, the first-order light rp, and the second-order light rq are laser beams that are wider than the vertical length of a single blaze surface 6h, so the zeroth-order light ro, the first-order light rp, and the second-order light rq are incident on multiple blaze surfaces 6h. In FIG. 3 , the blaze surface 6h on the back surface 6d that faces the blaze surface 6i in the plate thickness direction is referred to as blaze surface 6j. Furthermore, the blaze surface 6h located adjacent to the blaze surface 6j on one side of the blaze surface 6j in the vertical direction is referred to as blaze surface 6k. Furthermore, the blazed surface 6h located adjacent to the blazed surface 6j on the other side of the perpendicular direction to the blazed surface 6j is referred to as a blazed surface 6m.

[0033] The first-order light rp is refracted by the blaze surface 6i and travels only through the blaze surface 6j. On the other hand, the zeroth-order light ro is refracted by the blaze surface 6i and travels through the blaze surfaces 6j and 6k. The second-order light rq is refracted by the blaze surface 6i and travels through the blaze surfaces 6j and 6m. Because the wavefront of the zeroth-order light ro travels through both the blaze surfaces 6j and 6k, the wavefronts are canceled out by the phase difference between the blaze surfaces 6j and 6k, i.e., the path difference between the blaze surfaces 6j and 6k, and the diffraction efficiency of the zeroth-order light ro is reduced to approximately 0%. Furthermore, because the wavefront of the second-order light rq travels on both the blaze surfaces 6j and 6m, the wavefronts are offset by the phase difference between the blaze surfaces 6j and 6m, i.e., the path difference between the blaze surfaces 6j and 6m, and the diffraction efficiency of the second-order light rq is reduced to approximately 0%. The zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4 are not diffracted by the angular filter 6 and are emitted from the back surface 6d at the same angle at which they were incident on the front surface 6c. On the other hand, the first-order light rp travels only on the blaze surface 6j and does not travel on the blaze surfaces 6k and 6m, so the first-order light rp is diffracted with high diffraction efficiency. Only the first-order light rp emitted from the acousto-optic element 4 is diffracted by the angular filter 6.

[0034] In order for only the first-order light rp emitted from the acousto-optic element 4 to be diffracted by the angular filter 6, and for the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 to be emitted from the back surface 6d at the same angle at which they were incident on the front surface 6c without being diffracted by the angular filter 6, it is preferable to satisfy the following formula (1): In the following formula (1), the thickness of the angular filter 6 is d, the refractive index of the angular filter 6 is n, the period which is the vertical distance of the grooves 6f is T, and the angular difference between the zeroth-order light ro and first-order light rp emitted from the acousto-optic element 4, and the angular difference between the first-order light rp and second-order light rq emitted from the acousto-optic element 4 are δ, respectively. d ≈ nT / 2δ (1)

[0035] Note that even if the following formula (2) is satisfied, the same effect as when formula (1) is satisfied can be achieved: d=0.8 to 1.2×nT / 2δ (2)

[0036] FIG. 4 is a diagram showing the relationship between the angle of incidence of the laser beam r and the diffraction efficiency in the angular filter 6 of the first embodiment. FIG. 4 also shows the angles of incidence of the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optic element 4. Because the acousto-optic element 4 is a diffraction grating with a variable diffraction direction, the angles of incidence of the first-order light rp and the second-order light rq have angular ranges. As is clear from FIG. 4, the diffraction efficiency of the first-order light rp is higher than the diffraction efficiencies of the zeroth-order light ro and the second-order light rq. In other words, the diffraction efficiencies of the zeroth-order light ro and the second-order light rq are kept lower than those of the first-order light rp.

[0037] Next, the effects of the laser processing device 1 according to this embodiment will be described.

[0038] First, a technique for blocking the zeroth-order light ro and the second-order light rq so that they are not guided toward the workpiece 11 will be described. FIG. 5 is a perspective view showing an example of a method for absorbing the zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4. The laser processing apparatus 1B includes a Keplerian afocal lens 12 disposed between the acousto-optic element 4 and the galvanometer 8. The afocal lens 12 includes a pair of convex lenses 13 and 14 and a damper 15 disposed between the pair of convex lenses 13 and 14. The damper 15 has an opening 15a. In the laser processing apparatus 1B, the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optic element 4 are temporarily focused by the convex lens 13, and only the first-order light rp passes through the opening 15a of the damper 15 at the focused portion. The zeroth-order light ro and the second-order light rq are absorbed by the damper 15. However, in the laser processing apparatus 1B, the opening 15a must be positioned offset in the optical axis direction from the focal point P of the zeroth-order light ro and the focal point P of the second-order light rq so that the zeroth-order light ro and the second-order light rq do not process the opening 15a, and the zeroth-order light ro, the first-order light rp, and the second-order light rq must be separated from each other by several mm so that the zeroth-order light ro and the second-order light rq do not pass through the opening 15a. This results in a focal length of the convex lens 13 that is as long as several hundred mm, which causes problems such as an increase in the size of the laser processing apparatus 1B and a lengthened optical path.

[0039] Although not specifically shown, another technique is to separate the acousto-optic element from the galvanometer so that the zeroth-order and second-order light emitted from the acousto-optic element misses the galvanometer mirror of the galvanometer, thereby reflecting only the first-order light toward the focusing lens. However, the angular difference between the zeroth-order and first-order light and the angular difference between the first-order and second-order light emitted from the acousto-optic element are typically about 0.1 degrees to several degrees. In order to use this method to ensure that the zeroth-order and second-order light emitted from the acousto-optic element misses the galvanometer mirror of the galvanometer, the acousto-optic element and the galvanometer must be separated by about 1 meter. This leads to problems such as an increase in the size of the laser processing apparatus and a long optical path.

[0040] 1 to 3, the laser processing apparatus 1 includes an angular filter 6 that separates the zeroth-order light ro and second-order light rq from the first-order light rp of the laser beam r emitted from the acousto-optical element 4. In this embodiment, the angular filter 6 is a transmission type diffraction grating that diffracts the first-order light rp so that the angular difference between the zeroth-order light ro and the first-order light rp increases when the zeroth-order light ro and the first-order light rp emitted from the acousto-optical element 4 pass through the angular filter 6, and so that the angular difference between the first-order light rp and the second-order light rq emitted from the acousto-optical element 4 increases when the first-order light rp and the second-order light rq pass through the angular filter 6. This configuration separates the first-order light rp from the zeroth-order light ro and the second-order light rq, and allows only the first-order light rp required for processing the workpiece 11 to be guided toward the workpiece 11, while cutting out the zeroth-order light ro and second-order light rq that are unnecessary for processing the workpiece 11. Therefore, processing defects of the workpiece 11 caused by the zeroth-order light ro and the second-order light rq emitted from the acousto-optical element 4 are suppressed, resulting in a high-quality workpiece 11. Furthermore, with the above-described configuration, when the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optical element 4 pass through the angular filter 6, the angular difference between the zeroth-order light ro and the first-order light rp and the angular difference between the first-order light rp and the second-order light rq are widened, allowing the first-order light rp to be separated from the zeroth-order light ro and the second-order light rq over a shorter distance than with the above-described technology. This prevents the laser processing apparatus 1 from becoming larger and the optical path from becoming longer, thereby stabilizing the accuracy of the processing position despite environmental changes such as temperature. Therefore, in this embodiment, high-speed processing can be achieved with high quality and precision using a beam scanning mechanism composed of the acousto-optical element 4, the galvanometer 8, and the table 10.

[0041] 1, the laser processing apparatus 1 includes a damper 7 that absorbs the zeroth-order light ro and the second-order light rq of the laser beam r emitted from the acousto-optic element 4. This configuration makes it possible to prevent the zeroth-order light ro and the second-order light rq, which are unnecessary for processing the workpiece 11, from being irradiated onto unintended locations.

[0042] In this embodiment, the damper 7a is disposed near the angular filter 6a, so that the zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4a are absorbed by the damper 7a. Furthermore, in this embodiment, the damper 7b is disposed near the angular filter 6b, so that the zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4b are absorbed by the damper 7b. The damper 7 may be disposed, for example, at a distance of several tens of millimeters from the angular filter 6. By disposing the damper 7 in this manner, the zeroth-order light ro and the second-order light rq transmitted through the angular filter 6 are absorbed by the damper 7, so that the size of the laser processing apparatus 1 and the length of the optical path caused by the damper 7 can be suppressed.

[0043] 1, there are a plurality of acousto-optical elements 4 and a plurality of angular filters 6. With this configuration, the acousto-optical elements 4 can diffract the laser beam r in two directions, the X-axis direction and the Y-axis direction, and the irradiation position of the laser beam r on the workpiece 11 can be changed in the X-axis direction and the Y-axis direction.

[0044] 1, the laser processing apparatus 1 includes a half-wave plate 5b disposed between a plurality of angular filters 6a and 6b. This configuration allows the polarization direction of the primary light rp emitted from the angular filter 6a to be rotated by 90 degrees around the optical axis of the laser beam r. Generally, a diffraction grating has a higher diffraction efficiency for TE waves, i.e., S-polarized light. Therefore, by rotating the polarization direction of the primary light rp emitted from the angular filter 6a by 90 degrees around the optical axis of the laser beam r, the diffraction efficiency of the primary light rp in the angular filter 6b is increased, and the primary light rp with higher energy can be guided toward the workpiece 11.

[0045] 1, the laser processing apparatus 1 includes a half-wave plate 5a disposed between the plurality of acousto-optic elements 4a and 4b. This configuration allows the polarization direction of the first-order light rp emitted from the acousto-optic element 4a to be rotated by 90 degrees around the optical axis of the laser beam r. Generally, a diffraction grating has a higher diffraction efficiency for TE waves, i.e., S-polarized light. Therefore, by rotating the polarization direction of the first-order light rp emitted from the acousto-optic element 4a by 90 degrees around the optical axis of the laser beam r, the diffraction efficiency of the first-order light rp in the acousto-optic element 4b can be increased, and higher-energy first-order light rp can be guided toward the workpiece 11.

[0046] The angular filter 6 only needs to be able to separate the first-order light rp from at least one of the zeroth-order light ro and the second-order light rq of the laser beam r emitted from the acousto-optical element 4. In other words, the angular filter 6 only needs to be a transmission type diffraction grating that diffracts the first-order light rp so that the angular difference between the first-order light rp and at least one of the zeroth-order light ro and the second-order light rq emitted from the acousto-optical element 4 and the first-order light rp becomes large when the first-order light rp and at least one of the zeroth-order light ro and the second-order light rq emitted from the acousto-optical element 4 pass through the angular filter 6.

[0047] In this embodiment, the surface 6c and rear surface 6d of the angular filter 6 shown in Figure 3 are symmetrical about the center line C. However, they may be non-symmetrical about the center line C as long as the periods T of the surface 6c and rear surface 6d are the same. For example, the grating pattern 6e on the surface 6c and the grating pattern 6e on the rear surface 6d may be offset from each other in the vertical direction of the paper in Figure 3. There are incident angles of the zeroth-order light ro, the first-order light rp, and the second-order light rq such that only the first-order light rp is diffracted by the angular filter 6, and the zeroth-order light ro and the second-order light rq are not diffracted by the angular filter 6 and are emitted from the rear surface 6d at the same angles at which they were incident on the surface 6c. The angular filter 6 may be appropriately adjusted to achieve such angles of incidence.

[0048] Furthermore, the depth of the blazed surface 6 h on the front surface 6 c and the back surface 6 d, i.e., the length of the blazed surface 6 h in the plate thickness direction, may be different from each other. Even in this case, as long as the grating pattern 6 e is provided on each of the front surface 6 c and the back surface 6 d, the same effect as that of this embodiment can be achieved.

[0049] In this embodiment, the number of acousto-optical elements 4, half-wave plates 5, angular filters 6, dampers 7, and galvanometers 8 is two, but may be one or three or more. The half-wave plate 5 may be omitted. The arrangement of the angular filters 6a, 6b and dampers 7a, 7b is not limited to the example shown in the figure. For example, the angular filter 6a and damper 7a may be arranged after the acousto-optical element 4a, and the angular filter 6b and damper 7b may be arranged after the acousto-optical element 4b.

[0050] FIG. 6 is a diagram for explaining the function of the angular filter 6 according to a modification of the first embodiment. The angular filter 6 may be a volume phase holographic (VPH) diffraction grating as shown in FIG. 6. The angular filter 6 is a diffraction grating having stripes with high refractive index and stripes with low refractive index in the vertical direction along the surface 6c. In order for only the first-order light rp emitted from the acousto-optic element 4 to be diffracted by the angular filter 6, and for the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 to be emitted from the back surface 6d at the same angle at which they were incident on the surface 6c without being diffracted by the angular filter 6, it is preferable that the following formula (3) be satisfied: In the following formula (3), d denotes the thickness of the portion of the angular filter 6 that forms stripes with a refractive index, n denotes the average value of the refractive index of the high-refractive-index stripes and the low-refractive-index stripes, T denotes the period that is the vertical distance between the high-refractive-index stripes and the low-refractive-index stripes, and δ denotes the angular difference between the zeroth-order light ro and the first-order light rp emitted from the acousto-optic element 4, and the angular difference between the first-order light rp and the second-order light rq emitted from the acousto-optic element 4. d ≈ nT / 2δ (3)

[0051] Note that even if the following formula (4) is satisfied, the same effect as when formula (3) is satisfied can be achieved: d=0.8 to 1.2×nT / 2δ (4)

[0052] Second Embodiment Next, a laser processing apparatus 1A according to a second embodiment will be described with reference to Figures 7 to 9. In this embodiment, the configuration of the angle filter 6 differs from that of the first embodiment. In the second embodiment, parts that overlap with those of the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0053] FIG. 7 is a perspective view showing a laser processing apparatus 1A according to a second embodiment. As shown in FIG. 7, the angle filter 6 is a plate-shaped element formed of a material that is opaque to the laser beam r. The angle filter 6 has a thickness along the optical axis direction of the laser beam r. The outer shape of the angle filter 6 is not particularly limited, but in this embodiment, it is circular. The material of the plate-shaped element is not particularly limited as long as it is opaque to the wavelength of the laser beam r. The material of the plate-shaped element may be, for example, metal, resin, glass, or semiconductor. The angle filter 6 has multiple openings 6n formed therethrough in the plate thickness direction. Note that a half-wave plate 5 may be disposed between the multiple acousto-optic elements 4a and 4b. FIG. 8 is a perspective view showing the angle filter 6 according to the second embodiment. The shape of the openings 6n when viewed along the penetration direction is circular. The multiple openings 6n are arranged side by side in a direction intersecting the optical axis direction of the laser beam r. The multiple openings 6n are arranged adjacent to each other.

[0054] Next, the operation of the angle filter 6 of the second embodiment will be described with reference to FIG. 9 . FIG. 9 is a diagram for explaining the operation of the angle filter 6 of the second embodiment, and is a cross-sectional view of the angle filter 6. Here, it is assumed that the zeroth-order light ro, the first-order light rp, and the second-order light rq are incident on the same opening 6n on the surface 6c of the angle filter 6. For ease of understanding, FIG. 9 depicts the zeroth-order light ro, the first-order light rp, and the second-order light rq as a single line. In reality, the zeroth-order light ro, the first-order light rp, and the second-order light rq are laser beams that are wider than the size D of a single opening 6n, and therefore the zeroth-order light ro, the first-order light rp, and the second-order light rq are incident on multiple openings 6n.

[0055] The angular filter 6 is configured so that the transmittance of the first-order light rp passing through the angular filter 6 is higher than at least one of the transmittance of the zeroth-order light ro passing through the angular filter 6 and the transmittance of the second-order light rq passing through the angular filter 6. The angular filter 6 is an element disposed so that the transmission direction in which the laser beam r can pass through the angular filter 6 is parallel to the traveling direction of the first-order light rp and so that the transmission direction intersects with the traveling directions of the zeroth-order light ro and the second-order light rq. The transmission direction is the penetration direction of the opening 6n. In other words, the traveling direction of the first-order light rp coincides with the penetration direction of the opening 6n. The penetration direction of the opening 6n intersects with the traveling directions of the zeroth-order light ro and the second-order light rq. In this way, when the penetration direction of the opening 6n is made parallel to the propagation direction of the primary light rp and the penetration direction of the opening 6n is made intersecting with the propagation directions of the zeroth-order light ro and the secondary light rq, only the primary light rp passes through the opening 6n, while the zeroth-order light ro and the secondary light rq are blocked by the inner wall surface of the opening 6n, and the zeroth-order light ro and the secondary light rq can be absorbed or scattered by the inner wall surface of the opening 6n.

[0056] In order for only the first-order light rp emitted from the acousto-optic element 4 to pass through the opening 6n and for the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 to be blocked by the inner wall surface of the opening 6n, it is preferable to satisfy the following formula (5): In the following formula (5), the thickness of the angular filter 6 is d, the size of the opening 6n is D, and the angular difference between the zeroth-order light ro and the first-order light rp emitted from the acousto-optic element 4, and the angular difference between the first-order light rp and the second-order light rq emitted from the acousto-optic element 4 are δ, respectively. d≧D / δ (5)

[0057] In this embodiment, as shown in Figures 7 to 9, the angular filter 6 is a plate-shaped element made of a material that is opaque to the laser beam r, and multiple openings 6n are formed in the angular filter 6, penetrating the plate in the thickness direction. With this configuration, only the first-order light rp passes through the openings 6n, while the zeroth-order light ro and the second-order light rq are blocked by the inner wall surfaces of the openings 6n, allowing the zeroth-order light ro and the second-order light rq to be absorbed or scattered by the inner wall surfaces of the openings 6n. This separates the first-order light rp from the zeroth-order light ro and the second-order light rq, allowing only the first-order light rp required for processing the workpiece 11 to be guided toward the workpiece 11, while the zeroth-order light ro and the second-order light rq, which are unnecessary for processing the workpiece 11, are cut off. This suppresses processing defects of the workpiece 11 due to the zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4, resulting in a high-quality workpiece 11. Furthermore, with the above-described configuration, only the first-order light rp emitted from the acousto-optic element 4 passes through the angular filter 6, while the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 do not pass through the angular filter 6, so that the first-order light rp can be separated from the zeroth-order light ro and second-order light rq over a short distance. This prevents the laser processing apparatus 1A from becoming larger and the optical path from becoming longer, thereby stabilizing the accuracy of the processing position against environmental changes such as temperature. Therefore, in this embodiment, high-speed processing can be achieved with high quality and precision using a beam scanning mechanism composed of the acousto-optic element 4, galvanometer 8, and table 10.

[0058] 8 and 9, in this embodiment, the opening 6n has a circular shape when viewed along the penetration direction, and therefore the angular filter 6 does not have directionality in the X-axis and Y-axis directions. Therefore, the angular filter 6 can cut the zeroth-order light ro and second-order light rq in the X-axis direction output from the acousto-optical element 4a, and can also cut the zeroth-order light ro and second-order light rq in the Y-axis direction output from the acousto-optical element 4b. Therefore, in this embodiment, at least one angular filter 6 is required after the acousto-optical element 4. Furthermore, in this embodiment, the zeroth-order light ro and second-order light rq are absorbed or scattered by the inner wall surface of the opening 6n, so the damper 7 can be omitted.

[0059] FIG. 10 is a perspective view of the angular filter 6 according to Modification 1 of Embodiment 2. FIG. 11 is a perspective view of the angular filter 6 according to Modification 2 of Embodiment 2. In this embodiment, the shape of the opening 6n when viewed along the penetration direction is circular, but it may be other than circular. For example, the shape of the opening 6n when viewed along the penetration direction may be a triangle, a square as shown in FIG. 10, or a hexagon as shown in FIG. 11. Furthermore, the shape of the opening 6n when viewed along the penetration direction may be an ellipse or a rectangle, but is preferably a circle or a regular polygon. In this way, the angular filter 6 can be made to have no directionality in the X-axis and Y-axis directions. That is, the shape of the angular filter 6 is symmetrical in the X-axis and Y-axis directions. Regarding the size D of the opening 6n, if the shape of the opening 6n when viewed along the penetration direction is circular, the diameter of the circle is defined as the size D of the opening 6n. If the shape of the opening 6n when viewed along the penetration direction is elliptical, the major axis of the ellipse is defined as the size D of the opening 6n. When the shape of the opening 6n when viewed along the penetration direction is polygonal, the diameter of the circumscribing circle of the polygon is taken as the size D of the opening 6n.

[0060] Examples of methods for manufacturing the angular filter 6 include machining, etching, and die-sinking electrical discharge machining. Alternatively, a plurality of thin plates, each having openings 6n formed therein by etching or the like, may be stacked together until the thickness reaches a predetermined d, and the outer peripheries of the plates may be clamped by screws or the like, or the plates may be joined by diffusion bonding, ultrasonic bonding, or the like.

[0061] The angular filter 6, which is a plate-shaped element, may be an element formed by bundling a plurality of circular tubes. In such a configuration, the axial direction of the circular tubes is parallel to the traveling direction of the first-order light rp, and the axial direction of the circular tubes is intersected with the traveling directions of the zeroth-order light ro and the second-order light rq. The axial direction of the circular tubes is the transmission direction in which the laser beam r can pass through the angular filter 6.

[0062] The angular filter 6, which is a plate-shaped element, may be an element formed by bundling multiple fibers made of a material that transmits the laser beam r. For example, the angular filter 6 may be formed by bundling multiple glass fibers and sealing them with resin or the like, cutting the sealed multiple glass fibers in a direction perpendicular to the length of the glass fibers, polishing the cut surfaces, and then applying an anti-reflection film to the cut surfaces. In such a configuration, the length direction of the fibers may be parallel to the traveling direction of the primary light rp, and may intersect with the traveling directions of the zeroth-order light ro and the secondary light rq. The length direction of the fibers is the transmission direction in which the laser beam r can pass through the angular filter 6.

[0063] The angular filter 6 only needs to be able to separate at least one of the zeroth-order light ro and the second-order light rq from the first-order light rp of the laser beam r emitted from the acousto-optical element 4. That is, the angular filter 6 is a plate-shaped element, and it only needs to be arranged so that the transmission direction in which the laser beam r can pass through the angular filter 6 is parallel to the traveling direction of the first-order light rp, and so that the transmission direction intersects with at least one of the traveling directions of the zeroth-order light ro and the second-order light rq. In other words, it only needs to be configured so that even when the diffraction direction of the second-order light rq is changed, the transmittance of the first-order light rp passing through the angular filter 6 is higher than at least one of the transmittance of the zeroth-order light ro passing through the angular filter 6 and the transmittance of the second-order light rq passing through the angular filter 6.

[0064] The numbers of acousto-optical elements 4, angular filters 6 and galvanometers 8 are not limited to those shown in the figures and may be changed as appropriate.

[0065] Third Embodiment Next, a laser processing apparatus 1C according to a third embodiment will be described with reference to Figures 12 to 17. In this embodiment, the configuration of the angle filter 6 differs from that of the second embodiment. In the third embodiment, parts that overlap with those of the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0066] FIG. 12 is a perspective view of a laser processing apparatus 1C according to a third embodiment. The angular filter 6 shown in FIG. 12 is an etalon. The etalon is a wavelength filter that utilizes multiple interference between two opposing partial reflecting mirrors 6q. The etalon has a periodic transmission spectrum and a sharp transmission peak with a narrow half-width. The material of the etalon is not particularly limited as long as it can transmit the wavelength of the laser beam r. The etalon material may be, for example, glass, quartz, or a semiconductor. The etalon used as the angular filter 6 may be a solid etalon, but in this embodiment, an air-gap etalon is used, which has better angular characteristics than a solid etalon. However, if a solid etalon can be fabricated using a metamaterial with a refractive index of 0.3 or less relative to the wavelength of the laser beam r, it is preferable to use a solid etalon as the angular filter 6 because it can achieve more favorable angular characteristics than an air-gap etalon. The half-wave plate 5 may be disposed between the multiple acousto-optic elements 4a and 4b.

[0067] 13 is a cross-sectional view of the angular filter 6 of the third embodiment. The angular filter 6 is configured so that the transmittance of the first-order light rp passing through the angular filter 6 is higher than the transmittance of the zeroth-order light ro passing through the angular filter 6 and the transmittance of the second-order light rq passing through the angular filter 6. The angular filter 6 includes two transmitting members 6o and 6p facing each other across a gap G. Each of the transmitting members 6o and 6p has a flat plate shape. The two transmitting members 6o and 6p are arranged parallel to each other. The surface of each transmitting member 6o and 6p facing the gap G is a partially reflecting mirror 6q.

[0068] Next, the operation of the angular filter 6 of the third embodiment will be described with reference to Fig. 13. The laser beam r incident on the transmitting member 6o of the angular filter 6 at an incident angle θ passes through the transmitting member 6o and enters the gap G, then undergoes multiple reflection between the two partial reflecting mirrors 6q and is emitted from the transmitting member 6p.

[0069] In this case, if the following formula (6) is satisfied, the angular filter 6 will exhibit high transmittance. In the formula (6), the gap between the transparent members 6o and 6p is G, the incident angle of the laser beam r is θ, the wavelength of the laser beam r is λ, and m is an integer (natural number) equal to or greater than 1. 2G×cosθ=mλ (6)

[0070] According to the above formula (6), when the gap G and the incident angle θ are fixed and the wavelength λ is changed, high transmittance is obtained at a specific number of discrete and periodic wavelengths λ. In other words, the angular filter 6 exhibits a transmission spectrum with periodic transmission peaks. On the other hand, when the gap G and the wavelength λ are fixed and the incident angle θ is changed, high transmittance is obtained at a specific number of incident angles θ, and the specific number of incident angles θ become discrete. In this embodiment, the latter angular characteristic of the etalon is utilized. That is, the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optic element 4 have different exit angles and different incident angles θ on the angular filter 6. Therefore, in this embodiment, only the incident angle θ of the first-order light rp is adjusted to match the transmission peak of the angular filter 6. Note that the design parameters of the etalon are the gap G and the reflectivity of the partial reflecting mirror 6q. The reflectivity of the partial reflecting mirror 6q is preferably 50% or higher.

[0071] Next, the angular characteristics and transmission spectrum of the angle filter 6 of the third embodiment will be described with reference to FIGS.

[0072] FIG. 14 is an angular characteristic diagram showing the relationship between the incident angle θ and the transmittance of the angular filter 6 of the third embodiment at the wavelength λ of the laser beam r when the gap G is appropriately set. FIG. 14 illustrates a wide range of the incident angle θ. The center of the paper in the horizontal direction of FIG. 14 represents an incident angle θ of 0 degrees, i.e., the laser beam r is perpendicularly incident on the angular filter 6. As is clear from FIG. 14 , the transmission peaks are discrete, and the period of the transmission peaks narrows as the incident angle θ increases. In other words, by considering the angular difference between the zeroth-order light ro and the first-order light rp emitted from the acousto-optic device 4 and the angular difference between the first-order light rp and the second-order light rq, and selecting an appropriate incident angle θ for the first-order light rp, it is possible to achieve a high transmittance for only the first-order light rp and to keep the transmittances of the zeroth-order light ro and the second-order light rq low.

[0073] FIG. 15 is an enlarged view of the area surrounded by the thick dashed line in FIG. 14. FIG. 15 also shows the angles of incidence θ of the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optical element 4. FIG. 15 also shows the angle of incidence θ at which only the first-order light rp has high transmittance. Because the acousto-optical element 4 is a diffraction grating that varies the diffraction direction of the laser beam r, the angles of incidence θ of the first-order light rp and the second-order light rq have angular ranges. As is clear from FIG. 15, the transmittance of the first-order light rp is higher than that of the zeroth-order light ro and the second-order light rq. In other words, the transmittance of the zeroth-order light ro and the second-order light rq is kept lower than that of the first-order light rp. That is, by placing the angle filter 6 shown in Figures 12 and 13 at an appropriate angle in the optical path of the laser processing apparatus 1C, the first-order light rp emitted from the acousto-optic element 4 is transmitted, and the zeroth-order light ro and second-order light rq are reflected, thereby separating the first-order light rp from the zeroth-order light ro and second-order light rq.

[0074] FIG. 16 is a transmission spectrum diagram showing the relationship between wavelength λ and transmittance of the angular filter 6 of embodiment 3 at the incident angle θ of the transmission peak of the primary light rp shown in FIG. 15. FIG. 16 shows a wide wavelength range of wavelength λ. FIG. 17 is an enlarged view of the area surrounded by the thick dashed line in FIG. 16. As is clear from FIG. 16, the transmission peaks are discrete and periodic. FIG. 17 also shows a very narrow oscillation wavelength range in which the width of the laser beam r emitted from the laser oscillator 2 is less than 0.5 nm. The dot-hatched area in FIG. 17 is the oscillation wavelength range.

[0075] The transmission peak at the center in the horizontal direction of the page in Figure 14, i.e., where the incident angle θ is 0 degrees, is flatter than the other transmission peaks and has high transmittance over a wide angular range. Therefore, it is preferable to make the first-order light rp emitted from the acousto-optic element 4 perpendicularly incident on the angular filter 6 in order to maintain a uniform transmittance of the first-order light rp when the diffraction direction of the first-order light rp is changed. However, the angular difference from the transmission peak at an incident angle θ of 0 degrees to the adjacent bottom with lower transmittance is wider than the angular difference between the zeroth-order light ro and the first-order light rp or the angular difference between the first-order light rp and the second-order light rq, making it difficult to keep the transmittance of the zeroth-order light ro and the second-order light rq sufficiently low. In this case, widening the gap G can narrow the period of the transmission peaks in Figure 14, and the incident angle θ of the adjacent bottom with lower transmittance can be adjusted to match the incident angle θ of the zeroth-order light ro and the second-order light rq. However, when the gap G is widened, the period of the transmission peaks shown in Fig. 16 also narrows, and depending on the width of the oscillation wavelength range of the laser beam r, several transmission peaks may be included in the oscillation wavelength range of the laser beam r shown in Fig. 17. As a result, the transmittance of the primary light rp decreases.

[0076] In order to increase the transmittance of the first-order light rp and keep the transmittance of the zeroth-order light ro and the second-order light rq low, it is important to adjust the incidence angle θ of the first-order light rp, the incidence angle θ of the zeroth-order light ro, and the incidence angle θ of the second-order light rq by placing the angle filter 6 shown in Figures 12 and 13 in the optical path of the laser processing apparatus 1C at an appropriate angle with respect to the optical axis, and to adjust the gap G. It is also possible to fabricate a solid etalon using a metamaterial with a refractive index of 0.3 or less for the wavelength of the laser beam r. When this solid etalon is used as the angle filter 6, both the angular characteristics and the transmission spectrum described above can be satisfied. In other words, the first-order light rp can be incident perpendicularly on the angle filter 6, and the oscillation wavelength range of the laser beam r can be contained within a single transmission peak in the transmission spectrum.

[0077] 12 and 13 , in this embodiment, the angular filter 6 is an etalon configured so that the transmittance of the first-order light rp passing through the angular filter 6 is higher than the transmittance of the zeroth-order light ro passing through the angular filter 6 and the transmittance of the second-order light rq passing through the angular filter 6. With this configuration, only the first-order light rp passes through the angular filter 6, while the zeroth-order light ro and the second-order light rq are reflected by the angular filter 6. This separates the first-order light rp from the zeroth-order light ro and the second-order light rq, and allows only the first-order light rp required for processing the workpiece 11 to be guided toward the workpiece 11, while the zeroth-order light ro and the second-order light rq unnecessary for processing the workpiece 11 are cut off. This suppresses processing defects of the workpiece 11 due to the zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4, thereby obtaining a high-quality workpiece 11. Furthermore, with the above configuration, only the first-order light rp emitted from the acousto-optic element 4 passes through the angular filter 6, while the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 do not pass through the angular filter 6, so the first-order light rp can be separated from the zeroth-order light ro and second-order light rq over a short distance. This makes it possible to prevent the laser processing apparatus 1C from becoming larger and the optical path from becoming longer, thereby stabilizing the accuracy of the processing position against environmental changes such as temperature. Therefore, in this embodiment, high-speed processing can be achieved with high quality and precision using a beam scanning mechanism composed of the acousto-optic element 4, galvanometer 8, and table 10.

[0078] Furthermore, in this embodiment, the first-order light rp shown in FIG. 13 is incident on the etalon, which is the angle filter 6, at an angle other than perpendicular, so that it is possible to increase the transmittance of the first-order light rp while keeping the transmittance of the zeroth-order light ro and the second-order light rq low.

[0079] 14 and 15 , in this embodiment, the transmittance of the angular filter 6 changes depending on the incident angle θ, and therefore the angular filter 6 does not have directionality in the X-axis and Y-axis directions. Therefore, the zero-order light ro and second-order light rq in the X-axis direction output from the acousto-optical device 4a can be cut by the angular filter 6, and the zero-order light ro and second-order light rq in the Y-axis direction output from the acousto-optical device 4b can also be cut by the angular filter 6. Therefore, in this embodiment, at least one angular filter 6 is required after the acousto-optical device 4.

[0080] The angular filter 6 only needs to be able to separate the first-order light rp from at least one of the zeroth-order light ro and the second-order light rq of the laser beam r emitted from the acousto-optical element 4. In other words, the angular filter 6 only needs to be configured so that the transmittance of the first-order light rp passing through the angular filter 6 is higher than at least one of the transmittance of the zeroth-order light ro passing through the angular filter 6 and the transmittance of the second-order light rq passing through the angular filter 6.

[0081] The numbers of acousto-optical elements 4, angular filters 6 and galvanometers 8 are not limited to those shown in the figures and may be changed as appropriate.

[0082] Fourth Embodiment Next, a laser processing apparatus 1D according to a fourth embodiment will be described with reference to Figures 18 to 23. This embodiment differs from the second embodiment in that it includes the configuration of an angle filter 6 and a damper 7. In the fourth embodiment, parts that overlap with those in the second embodiment are designated by the same reference numerals and will not be described again.

[0083] FIG. 18 is a perspective view showing a laser processing apparatus 1D according to a fourth embodiment. FIG. 19 is a diagram for explaining the function of the angular filter 6 according to the fourth embodiment. The double-headed arrows Y0, Y1, and Y2 shown in FIG. 19 represent the polarization directions of the zeroth-order light ro, the first-order light rp, and the second-order light rq, respectively. The double-headed arrow Y3 shown in FIG. 19 represents the polarization direction of the laser beam r when it enters the acousto-optic element 4. The angular filter 6 shown in FIG. 18 is an attenuator including a wave plate 6r and a polarizing beam splitter 6s. As shown in FIG. 19, the wave plate 6r causes the polarization direction Y1 of the first-order light rp to differ by 90 degrees from the polarization direction Y0 of the zeroth-order light ro and the polarization direction Y2 of the second-order light rq. The polarizing beam splitter 6s is disposed after the wave plate 6r on the optical path of the laser beam r, and either transmits only the first-order light rp and reflects the zeroth-order light ro and the second-order light rq, or reflects only the first-order light rp and transmits the zeroth-order light ro and the second-order light rq. The attenuator can adjust the intensity ratio between the light transmitted through the polarizing beam splitter 6s and the light reflected by the polarizing beam splitter 6s. The angle filter 6 is configured so that the transmittance of the first-order light rp passing through the angle filter 6 is higher than the transmittance of the zeroth-order light ro and the second-order light rq passing through the angle filter 6. Here, "pass" means that when the first-order light rp passes through the polarizing beam splitter 6s, the zeroth-order light ro and the second-order light rq are also transmitted, and when the first-order light rp is reflected by the polarizing beam splitter 6s, the zeroth-order light ro and the second-order light rq are also reflected. Furthermore, the transmittance refers to the transmittance when the primary light rp passes through the polarizing beam splitter 6s, and refers to the reflectance when the primary light rp is reflected by the polarizing beam splitter 6s. The material of the wave plate 6r is not particularly limited as long as it is a birefringent material that can transmit the wavelength of the laser beam r. The birefringent material may be a uniaxial crystal or a biaxial crystal. The material of the wave plate 6r is, for example, quartz. In this embodiment, the wave plate 6r used as the angular filter 6 is a multi-order wave plate.

[0084] As shown in FIG. 18 , the number of angular filters 6 is two in this embodiment. In the following description, when the two angular filters 6 need to be distinguished, they are referred to as angular filter 6a and angular filter 6b. When the wave plates 6r of the two angular filters 6 need to be distinguished, they are referred to as wave plates 6r1 and 6r2. When the polarizing beam splitters 6s of the two angular filters 6 need to be distinguished, they are referred to as polarizing beam splitters 6s1 and 6s2. In this embodiment, the wave plate 6r2 and polarizing beam splitter 6s2 are arranged after the acousto-optic element 4b on the optical path of the laser beam r, and the wave plate 6r1 and polarizing beam splitter 6s1 are arranged after the acousto-optic element 4a on the optical path of the laser beam r. Note that the half-wave plate 5 may be arranged between the polarizing beam splitter 6s2 and the acousto-optic element 4a.

[0085] The damper 7 serves to absorb the zeroth-order light ro and the second-order light rq of the laser beam r emitted from the angular filter 6. In this embodiment, there are two dampers 7. In the following description, when the two dampers 7 need to be distinguished, they will be referred to as damper 7a and damper 7b. The damper 7a is disposed near the angular filter 6a and absorbs the zeroth-order light ro and the second-order light rq of the laser beam r emitted from the angular filter 6a. The damper 7b is disposed near the angular filter 6b and absorbs the zeroth-order light ro and the second-order light rq of the laser beam r emitted from the angular filter 6b.

[0086] Next, the operation of the angular filter 6 of the fourth embodiment will be described with reference to FIG. 19 . Because the angular filters 6a and 6b have the same operation, only the operation of the angular filter 6b, which is disposed after the acousto-optic element 4b on the optical path of the laser beam r, will be described here, and the operation of the angular filter 6a will be omitted. The zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optic element 4b are incident on the wave plate 6r2 at different angles. Each of the zeroth-order light ro, the first-order light rp, and the second-order light rq is linearly polarized light. The arrow marked V on the surface of the wave plate 6r2 indicates the direction of the optical axis of the wave plate 6r2. The polarization directions Y0, Y1, and Y2 of the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the wave plate 6r2 rotate or do not rotate depending on the optical path length within the wave plate 6r2. The design parameter of the wave plate 6r is its thickness (optical path length).

[0087] In this embodiment, the angle formed by the direction V of the optical axis of the wave plate 6r2 and the polarization directions Y0, Y1, and Y2 of the zeroth-order light ro, first-order light rp, and second-order light rq incident on the wave plate 6r2 is 45 degrees. Furthermore, in this embodiment, only the polarization direction Y1 of the first-order light rp output from the wave plate 6r2 is rotated by 90 degrees, while the polarization directions Y0 and Y2 of the zeroth-order light ro and second-order light rq are not rotated and are the same as the polarization directions Y0 and Y2 when they entered the wave plate 6r2. Furthermore, in this embodiment, only the first-order light rp passes through the polarizing beam splitter 6s2, and the zeroth-order light ro and second-order light rq are reflected by the polarizing beam splitter 6s2. By adjusting the thickness of the wave plate 6r2 or adjusting the angles of incidence of the zeroth-order light ro, the first-order light rp, and the second-order light rq on the wave plate 6r2, it is possible to rotate only the polarization direction Y1 of the first-order light rp emitted from the wave plate 6r2 by 90 degrees without rotating the polarization directions Y0 and Y2 of the zeroth-order light ro and the second-order light rq, as in the present embodiment, or to rotate the polarization directions Y0 and Y2 of the zeroth-order light ro and the second-order light rq by 90 degrees without rotating the polarization direction Y1 of the first-order light rp emitted from the wave plate 6r2. In the latter case, only the first-order light rp is reflected by the polarizing beam splitter 6s2, and the zeroth-order light ro and the second-order light rq are transmitted through the polarizing beam splitter 6s2.

[0088] Furthermore, by rotating the polarizing beam splitter 6s2 by 90 degrees around the optical axis from the state in Fig. 19, it is also possible to change the polarization directions Y0, Y1, Y2 of the zeroth-order light ro, first-order light rp, and second-order light rq emitted from the wave plate 6r2 from the state in Fig. 19 so that only the first-order light rp is reflected by the polarizing beam splitter 6s2 and the zeroth-order light ro and second-order light rq are transmitted through the polarizing beam splitter 6s2, without changing them from the state in Fig. 19. As described above, by using the wave plate 6r2 to make the polarization direction Y1 of the first-order light rp different from the polarization direction Y0 of the zeroth-order light ro and the polarization direction Y2 of the second-order light rq by 90 degrees, it is possible to transmit only the first-order light rp through the polarizing beam splitter 6s2, or to reflect only the first-order light rp by the polarizing beam splitter 6s2. The damper 7 may be disposed ahead of the zero-order light ro and the second-order light rq in the traveling direction, which are transmitted through the polarizing beam splitter 6s2 or reflected by the polarizing beam splitter 6s2.

[0089] Next, the angular characteristics and transmission spectrum of the angle filter 6 of the fourth embodiment will be described with reference to FIGS.

[0090] FIG. 20 is an angle characteristic diagram showing the relationship between the angle of incidence on the wave plate 6r of the angular filter 6 of embodiment 4 and the transmittance at the wavelength λ of the laser beam r when the thickness of the wave plate 6r is appropriately set. FIG. 20 illustrates a wide range of the angle of incidence. The center of the paper in the horizontal direction of FIG. 20 represents an angle of incidence of 0 degrees, i.e., the laser beam r is perpendicularly incident on the angular filter 6. As is clear from FIG. 20 , the transmission peaks are periodic, and the period of the transmission peaks narrows as the angle of incidence increases. In other words, by considering the angular difference between the zeroth-order light ro and the first-order light rp emitted from the acousto-optic device 4 and the angular difference between the first-order light rp and the second-order light rq, and selecting an appropriate angle of incidence for the first-order light rp, it is possible to achieve a high transmittance for only the first-order light rp and keep the transmittances of the zeroth-order light ro and the second-order light rq low.

[0091] FIG. 21 is an enlarged view of the area surrounded by the thick dashed line in FIG. 20. FIG. 21 also shows the angles of incidence of the zeroth-order light ro, the first-order light rp, and the second-order light rq emitted from the acousto-optical element 4. FIG. 21 shows the angles of incidence at which only the first-order light rp has high transmittance. Because the acousto-optical element 4 is a diffraction grating that varies the diffraction direction of the laser beam r, the angles of incidence of the first-order light rp and the second-order light rq have angular ranges. As is clear from FIG. 21, it can be seen that the transmittance of the first-order light rp is higher than that of the zeroth-order light ro and the second-order light rq. In other words, it can be seen that the transmittance of the zeroth-order light ro and the second-order light rq is kept lower than that of the first-order light rp. That is, by arranging the wave plate 6r of the angle filter 6 shown in FIG. 18 at an appropriate angle in the optical path of the laser processing apparatus 1D, the polarized beam splitter 6s2 shown in FIG. 19 can transmit only the first-order light rp emitted from the acousto-optic element 4 and reflect the zeroth-order light ro and the second-order light rq, thereby separating the first-order light rp from the zeroth-order light ro and the second-order light rq.

[0092] FIG. 22 is a transmission spectrum diagram showing the relationship between wavelength λ and transmittance of the angular filter 6 of embodiment 4 at the incident angle of the transmission peak of the primary light rp shown in FIG. 21. FIG. 22 shows a wide wavelength range of wavelength λ. FIG. 23 is an enlarged view of the area surrounded by the thick dashed line in FIG. 22. As is clear from FIG. 22, the transmission peaks are periodic. FIG. 23 also shows a very narrow oscillation wavelength range in which the width of the laser beam r emitted from the laser oscillator 2 is less than 0.5 nm. The dot-hatched area in FIG. 23 is the oscillation wavelength range.

[0093] The transmission peak at the center of the horizontal direction of the page in Figure 20, i.e., at an incident angle of 0 degrees, is flatter than the other transmission peaks and has high transmittance over a wide angular range. Therefore, it is preferable to make the first-order light rp emitted from the acousto-optic element 4 perpendicularly incident on the wave plate 6r in order to maintain a uniform transmittance of the first-order light rp when the diffraction direction of the first-order light rp is changed. However, the angular difference from the transmission peak at an incident angle of 0 degrees to the adjacent bottom with low transmittance is wider than the angular difference between the zeroth-order light ro and the first-order light rp or the angular difference between the first-order light rp and the second-order light rq, making it difficult to keep the transmittance of the zeroth-order light ro and the second-order light rq sufficiently low. In this case, by increasing the thickness of the wave plate 6r, the period of the transmission peaks in Figure 20 can be narrowed, and the incident angle of the adjacent bottom with low transmittance can be adjusted to match the incident angle of the zeroth-order light ro and the second-order light rq. However, if the thickness of the wave plate 6r is increased, the period of the transmission peaks shown in Fig. 22 also becomes narrower, and depending on the width of the oscillation wavelength range of the laser beam r, several transmission peaks may be included in the oscillation wavelength range of the laser beam r shown in Fig. 23. As a result, the transmittance of the primary light rp decreases.

[0094] Since the secondary light rq emitted from the acousto-optic element 4 has a wide angular range when the diffraction direction is changed, it is preferable to make the secondary light rq perpendicularly incident on the wave plate 6r and to reflect the primary light rp by the angle filter 6 in order to reduce the transmittance of the secondary light rq. Furthermore, it is possible to change the thickness of the wave plate 6r and invert the angle characteristic diagram in Figure 20 upside down. In other words, it is also possible to make the secondary light rq perpendicularly incident on the wave plate 6r be reflected by the polarizing beam splitter 6s and the primary light rp be transmitted through the polarizing beam splitter 6s.

[0095] In order to increase the transmittance of the first-order light rp and keep the transmittance of the zeroth-order light ro and the second-order light rq low, it is important to adjust the angle of incidence of the first-order light rp, the angle of incidence of the zeroth-order light ro, and the angle of incidence of the second-order light rq shown in Figure 19 by placing the wave plate 6r of the angle filter 6 shown in Figure 18 in the optical path of the laser processing device 1D at an appropriate angle with respect to the optical axis, and to adjust the thickness of the wave plate 6r.

[0096] 18 and 19 , in this embodiment, the angular filter 6 is an attenuator configured so that the transmittance of the first-order light rp passing through the angular filter 6 is higher than the transmittance of the zeroth-order light ro passing through the angular filter 6 and the transmittance of the second-order light rq passing through the angular filter 6. Specifically, the angular filter 6 includes a wave plate 6r that makes the polarization direction Y1 of the first-order light rp differ by 90 degrees from the polarization direction Y0 of the zeroth-order light ro and the polarization direction Y2 of the second-order light rq, and a polarizing beam splitter 6s that is arranged after the wave plate 6r on the optical path of the laser beam r and that transmits only the first-order light rp and reflects the zeroth-order light ro and the second-order light rq, or that reflects only the first-order light rp and transmits the zeroth-order light ro and the second-order light rq. With this configuration, only the first-order light rp passes through the angular filter 6, while the zeroth-order light ro and the second-order light rq are reflected by the angular filter 6, or alternatively, only the first-order light rp is reflected by the angular filter 6, while the zeroth-order light ro and the second-order light rq pass through the angular filter 6. This separates the first-order light rp from the zeroth-order light ro and the second-order light rq, allowing only the first-order light rp required for processing the workpiece 11 to be guided toward the workpiece 11, while cutting out the zeroth-order light ro and the second-order light rq that are not required for processing the workpiece 11. This suppresses processing defects in the workpiece 11 caused by the zeroth-order light ro and the second-order light rq emitted from the acousto-optic element 4, allowing a high-quality workpiece 11 to be obtained. Furthermore, with the above configuration, only the first-order light rp emitted from the acousto-optic element 4 passes through the angular filter 6, while the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 are reflected by the angular filter 6, or alternatively, only the first-order light rp emitted from the acousto-optic element 4 is reflected by the angular filter 6, while the zeroth-order light ro and second-order light rq emitted from the acousto-optic element 4 pass through the angular filter 6, thereby enabling the first-order light rp to be separated from the zeroth-order light ro and second-order light rq over a short distance. This prevents the laser processing apparatus 1D from becoming larger and the optical path from becoming longer, thereby stabilizing the accuracy of the processing position despite environmental changes such as temperature. Therefore, in this embodiment, high-speed processing can be achieved with high quality and precision using a beam scanning mechanism composed of the acousto-optic element 4, the galvanometer 8, and the table 10.

[0097] In addition, in this embodiment, the first-order light rp shown in Figure 19 is incident on the wave plate 6r of the angle filter 6 at an angle other than perpendicular, so that it is possible to increase the transmittance of the first-order light rp while keeping the transmittance of the zeroth-order light ro and the second-order light rq low.

[0098] 18 and 19, the laser processing apparatus 1D in this embodiment is provided with a damper 7 that absorbs the zero-order light ro and the second-order light rq that are transmitted through the polarizing beam splitter 6s or reflected by the polarizing beam splitter 6s. This configuration makes it possible to prevent the zero-order light ro and the second-order light rq that are unnecessary for processing the workpiece 11 from being irradiated onto unintended locations.

[0099] The angular filter 6 only needs to be able to separate at least one of the zeroth-order light ro and the second-order light rq from the first-order light rp of the laser beam r emitted from the acousto-optical element 4. That is, the angular filter 6 only needs to be arranged so that the angular difference between at least one of the zeroth-order light ro and the second-order light rq and the first-order light rp becomes large when the zeroth-order light ro and the second-order light rq emitted from the acousto-optical element 4 and the first-order light rp pass through the angular filter 6. In other words, the angular filter 6 only needs to be configured so that the transmittance of the first-order light rp passing through the angular filter 6 is higher than at least one of the transmittance of the zeroth-order light ro and the second-order light rq passing through the angular filter 6.

[0100] The numbers of acousto-optical elements 4, angular filters 6, and galvanometers 8 are not limited to those shown in the example and may be changed as appropriate. For example, the angular filter 6 arranged after the acousto-optical element 4b shown in FIG. 18 may be omitted.

[0101] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0102] Various aspects of the present disclosure are summarized below as appendices.

[0103] (Supplementary Note 1) A laser processing apparatus comprising: a laser oscillator that emits a laser beam; an acousto-optic element that diffracts the laser beam emitted from the laser oscillator; and an angular filter that separates at least one of zeroth-order light and second-order light from the laser beam emitted from the acousto-optic element and the first-order light, wherein the angular filter is configured so that a transmittance of the first-order light passing through the angular filter is higher than at least one of a transmittance of the zeroth-order light passing through the angular filter and a transmittance of the second-order light passing through the angular filter. (Supplementary Note 2) The laser processing apparatus according to Supplementary Note 1, characterized in that the angular filter comprises: a wave plate that shifts the polarization direction of the first-order light from the polarization directions of the zeroth-order light and the second-order light by 90 degrees; and a polarizing beam splitter that is arranged after the wave plate on the optical path of the laser beam and that transmits only the first-order light and reflects the zeroth-order light and the second-order light, or reflects only the first-order light and transmits the zeroth-order light and the second-order light. (Supplementary Note 3) The laser processing apparatus according to Supplementary Note 2, wherein the primary light is incident on the wave plate at an angle other than perpendicular. (Supplementary Note 4) The laser processing apparatus according to Supplementary Note 1, wherein the angular filter is an etalon. (Supplementary Note 5) The laser processing apparatus according to Supplementary Note 4, wherein the primary light is incident on the etalon at an angle other than perpendicular. (Supplementary Note 6) The laser processing apparatus according to Supplementary Note 1, wherein the angular filter is a plate-like element formed from a material that is not transmissive to the laser beam, and wherein the plate-like element has a plurality of openings formed therethrough in the plate thickness direction. (Supplementary Note 7) The laser processing apparatus according to Supplementary Note 6, wherein the shape of the openings when viewed along the penetration direction is a circle or a regular polygon. (Supplementary Note 8) The laser processing apparatus according to Supplementary Note 1, wherein the angular filter is an element formed by bundling a plurality of fibers formed from a material that is transmissive to the laser beam.(Supplementary Note 9) A laser processing apparatus comprising: a laser oscillator that emits a laser beam; an acousto-optic element that diffracts the laser beam emitted from the laser oscillator; and an angular filter that separates at least one of zeroth-order light and second-order light from the laser beam emitted from the acousto-optic element into first-order light, wherein the angular filter is a transmission diffraction grating that diffracts the first-order light so that an angular difference between the zeroth-order light and one of the second-order light and the first-order light becomes large when the zeroth-order light and the second-order light emitted from the acousto-optic element and the first-order light pass through the angular filter. (Supplementary Note 10) The laser processing apparatus according to Supplementary Note 9, wherein the transmission diffraction grating is a volume phase holographic diffraction grating. (Supplementary Note 11) The laser processing apparatus according to Supplementary Note 9, wherein the transmission diffraction grating includes a front surface onto which the laser beam is incident and a back surface from which the laser beam is emitted, and wherein grating patterns are provided on the front surface and the back surface. (Supplementary Note 12) The laser processing apparatus according to any one of Supplements 1 to 11, characterized in that the number of each of the acousto-optic elements and the angular filters is plural. (Supplementary Note 13) The laser processing apparatus according to any one of Supplements 1 to 12, characterized in that it comprises at least one damper that absorbs at least one of the zeroth-order light and the second-order light of the laser beam emitted from the acousto-optic element. (Supplementary Note 14) The laser processing apparatus according to Supplementary Note 12, characterized in that it comprises a half-wave plate arranged between the plurality of angular filters. (Supplementary Note 15) The laser processing apparatus according to Supplementary Note 12 or 14, characterized in that it comprises a half-wave plate arranged between the plurality of acousto-optic elements.

[0104] 1, 1A, 1B, 1C, 1D laser processing device, 2 laser oscillator, 3 mirror, 4, 4a, 4b acousto-optic element, 5, 5a, 5b 1 / 2 wave plate, 6, 6a, 6b angle filter, 6c surface, 6d back surface, 6e grating pattern, 6f groove, 6g step surface, 6h, 6i, 6j, 6k, 6m blazed surface, 6n, 15a aperture, 6o, 6p transparent member, 6q partial reflecting mirror, 6r, 6r1, 6r2 wave plate, 6s, 6s1, 6s2 polarizing beam splitter, 7, 7a, 7b, 15 damper, 8, 8a, 8b galvanometer, 8c galvanometer mirror, 8d galvanometer motor, 9 condenser lens, 10 table, 11 workpiece, 12 afocal lens, 13, 14 Convex lens, C center line, G gap, r laser beam, ro 0th order light, rp 1st order light, rq 2nd order light, V direction of the optical axis of the wave plate, Y0, Y1, Y2, Y3 polarization directions.

Claims

1. a laser oscillator that emits a laser beam; an acousto-optic element that diffracts the laser beam emitted from the laser oscillator; an angle filter that separates at least one of a zero-order light and a second-order light from a first-order light of the laser beam outputted from the acousto-optical element; The laser processing apparatus is characterized in that the angle filter is positioned at a position close to the acousto-optical element where a portion of the first-order light and a portion of the zeroth-order light overlap with a portion of the first-order light and a portion of the second-order light, and is configured so that the transmittance of the first-order light passing through the angle filter is higher than at least one of the transmittance of the zeroth-order light passing through the angle filter and the transmittance of the second-order light passing through the angle filter.

2. The angle filter is A wave plate that makes the polarization direction of the first-order light different from the polarization direction of the zeroth-order light and the polarization direction of the second-order light by 90 degrees; a polarizing beam splitter that is disposed after the wave plate on the optical path of the laser beam and transmits only the first-order light and reflects the zeroth-order light and the second-order light, or reflects only the first-order light and transmits the zeroth-order light and the second-order light; 2. The laser processing apparatus according to claim 1, further comprising:

3. 3. The laser processing apparatus according to claim 2, wherein the primary light is incident on the wave plate at an angle other than perpendicular.

4. 2. The laser processing apparatus according to claim 1, wherein the angle filter is an etalon.

5. 5. The laser processing apparatus according to claim 4, wherein the primary light is incident on the etalon at an angle other than perpendicular.

6. the angular filter is a plate-like element formed of a material that is not transparent to the laser beam, 2. The laser processing apparatus according to claim 1, wherein the plate-like element is formed with a plurality of openings penetrating in a plate thickness direction.

7. 7. The laser processing device according to claim 6, wherein the opening has a shape of a circle or a regular polygon when viewed in the penetrating direction.

8. 2. The laser processing apparatus according to claim 1, wherein the angle filter is an element formed by bundling a plurality of fibers made of a material through which the laser beam passes.

9. a laser oscillator that emits a laser beam; an acousto-optic element that diffracts the laser beam emitted from the laser oscillator; an angle filter that separates at least one of a zero-order light and a second-order light from a first-order light of the laser beam outputted from the acousto-optical element; The laser processing apparatus is characterized in that the angular filter is a transmission type diffraction grating that diffracts the first-order light so that the angular difference between the first-order light and at least one of the zero-order light and the second-order light emitted from the acousto-optical element and the zero-order light is large when the first-order light and at least one of the zero-order light and the second-order light pass through the angular filter.

10. 10. The laser processing apparatus according to claim 9, wherein the transmission type diffraction grating is a volume phase holographic type diffraction grating.

11. the transmission type diffraction grating includes a front surface onto which the laser beam is incident and a back surface from which the laser beam is emitted, 10. The laser processing apparatus according to claim 9, wherein the front surface and the back surface are provided with a lattice pattern.

12. 10. The laser processing apparatus according to claim 1, wherein the number of the acousto-optical elements and the number of the angle filters are each plural.

13. 10. The laser processing apparatus according to claim 1, further comprising at least one damper for absorbing at least one of the zeroth order light and the second order light of the laser beam emitted from the acousto-optical element.

14. The laser processing apparatus according to claim 12, further comprising a half-wave plate disposed between the plurality of angle filters.

15. 13. The laser processing apparatus according to claim 12, further comprising a half-wave plate disposed between the plurality of acousto-optic elements.