Laser processing equipment

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

Technical Field

[0001] The present disclosure relates to a laser processing apparatus that irradiates a workpiece with a laser beam to process the workpiece.

Background Art

[0002] Conventionally, a laser processing apparatus including a laser oscillator, a galvanometer, a condenser lens, and a table is known. In such a laser processing apparatus, after a laser beam emitted from the laser oscillator is reflected by a galvanometer mirror of the galvanometer, it is irradiated onto the workpiece by the condenser lens to process the workpiece held on the table. Since the area that can be scanned by the galvanometer, that is, the scan area, is limited to several tens of millimeters square, the entire area of the workpiece is processed by moving the table holding the workpiece to switch the scan area.

[0003] The galvanometer has the characteristics that the scan area is narrow but the operating speed is fast. On the other hand, the table has the characteristics that the operating speed is slower than that of the galvanometer, but the moving range is wider than the scan area of the galvanometer. Therefore, after the workpiece is processed 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 has been processed, and the workpiece is again processed at high speed in the scan area that can be scanned by the galvanometer. By repeating such a series of operations, the processing time spent on processing the entire area of the workpiece is reduced.

[0004] In order to further reduce processing time, as disclosed in Patent Document 1, an acousto-optic element is placed between the laser oscillator and the galvanometer in the optical path of the laser beam, and the irradiation position of the laser beam on the workpiece is changed by combining the acousto-optic element, the galvanometer, and the table. The acousto-optic element has a smaller scan area compared to the scan area of ​​the galvanometer and the movement range of the table, but it has the advantage of operating at a faster speed than the galvanometer and the table.

[0005] Generally, the diffraction efficiency of acousto-optic elements, which are diffraction gratings, is 80% to 90%. This means that when a laser beam is incident on an acousto-optic element, not only the primary light but also the zeroth and secondary light are emitted from the element. If the zeroth and secondary light reach the surface of the workpiece, undesired areas of the workpiece will be processed, leading to a problem of workpiece defects.

[0006] As a way to avoid such problems, Patent Document 1 discloses a method of shielding the zeroth-order light emitted from an acoustic-optic element with a shielding plate. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2003-136270 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, the angular difference between the 0th-order light and the 1st-order light emitted from the acousto-optic element is usually around 10 mrad to 100 mrad. Therefore, in order to shield only the 0th-order light using the method disclosed in Patent Document 1, the shielding plate needs to be placed about 1 m away from the acousto-optic element. This leads to problems such as the laser processing equipment becoming larger and the optical path becoming longer.

[0009] This disclosure has been made in view of the above, and aims to provide a laser processing apparatus that can suppress processing defects in the workpiece caused by the 0th and 2nd order light emitted from the acousto-optic element, while suppressing the need for a larger laser processing apparatus and a longer optical path compared to conventional devices. [Means for solving the problem]

[0010] To solve the above-mentioned problems and achieve the objective, the laser processing apparatus according to this disclosure comprises 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 at least one of the 0th-order and 2nd-order light from the 1st-order light of the laser beam emitted from the acousto-optic element. The angle filter is A portion of the primary light and a portion of the zeroth light are positioned close to the acousto-optic element where a portion of the primary light and a portion of the secondary light overlap, and The angle filter is configured such that the pass-through rate of primary light passing through the angle filter is higher than at least one of the pass-through rate of zero-order light passing through the angle filter and the pass-through rate of secondary light passing through the angle filter. [Effects of the Invention]

[0011] The laser processing apparatus described herein has the effect of suppressing processing defects in the workpiece caused by the 0th and 2nd order light emitted from the acousto-optic element, while also suppressing the need for a larger laser processing apparatus and longer optical path compared to conventional devices. [Brief explanation of the drawing]

[0012] [Figure 1] Perspective view showing a laser processing apparatus according to Embodiment 1 [Figure 2] A diagram illustrating the operation of the angle filter in Embodiment 1. [Figure 3] Enlarged view of section A shown in Figure 2 [Figure 4] This figure shows the relationship between the incident angle of the laser beam and the diffraction efficiency in the angle filter of Embodiment 1. [Figure 5] A perspective view illustrating an example of a method for absorbing 0th and 2nd order light emitted from an acoustic-optic element. [Figure 6]Figure for explaining the operation of the angle filter according to the modified example of Embodiment 1 [Figure 7] Perspective view showing the laser processing apparatus according to Embodiment 2 [Figure 8] Perspective view showing the angle filter of Embodiment 2 [Figure 9] Figure for explaining the operation of the angle filter of Embodiment 2, which is a cross-sectional view of the angle filter [Figure 10] Perspective view showing the angle filter of Modified Example 1 of Embodiment 2 [Figure 11] Perspective view showing the angle filter of Modified Example 2 of Embodiment 2 [Figure 12] Perspective view showing the laser processing apparatus according to Embodiment 3 [Figure 13] Cross-sectional view of the angle filter of Embodiment 3 [Figure 14] Angle characteristic diagram showing the relationship between the incident angle and the transmittance of the angle filter of Embodiment 3 at the wavelength of the laser beam when the gap is appropriately set [Figure 15] Figure obtained by expanding the range surrounded by the thick dashed line in FIG. 14 [Figure 16] Transmission spectrum diagram showing the relationship between the wavelength and the transmittance of the angle filter of Embodiment 3 at the incident angle of the transmission peak of the primary light shown in FIG. 15 [Figure 17] Figure obtained by expanding the range surrounded by the thick dashed line in FIG. 16 [Figure 18] Perspective view showing the laser processing apparatus according to Embodiment 4 [Figure 19] Figure for explaining the operation of the angle filter of Embodiment 4 [Figure 20] Angle characteristic diagram showing the relationship between the incident angle to the wavelength plate and the transmittance of the angle filter of Embodiment 4 at the wavelength of the laser beam when the thickness of the wavelength plate is appropriately set [Figure 21] Figure obtained by expanding the range surrounded by the thick dashed line in FIG. 20 [Figure 22] Transmission spectrum diagram showing the relationship between the wavelength and the transmittance of the angle filter of Embodiment 4 at the incident angle of the transmission peak of the primary light shown in FIG. 21 [Figure 23] An enlarged view of the area enclosed by the thick dashed line in Figure 22. [Modes for carrying out the invention]

[0013] The laser processing apparatus according to this embodiment will be described in detail below with reference to the drawings.

[0014] Embodiment 1. Figure 1 is a perspective view showing a laser processing apparatus 1 according to Embodiment 1. The laser processing apparatus 1 is a device that processes a workpiece 11 by irradiating it 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 comprises 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 focusing lens 9, and a table 10. In addition to the mirror 3, the laser processing apparatus 1 also comprises a plurality of other mirrors, which are not shown in the figure.

[0015] The laser beam r emitted from the laser oscillator 2 is reflected by the mirror 3 and passes through the acousto-optic element 4, the half-wave plate 5, and the angle filter 6. Subsequently, the laser beam r is reflected by the galvanometer 8, positioned on the workpiece 11 by the focusing 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 processed such as drilled or marked. In the following explanation, directions will be described according to the X-axis, Y-axis, and Z-axis directions shown in Figure 1. The X-axis and Y-axis directions shown in Figure 1 are parallel to the horizontal direction and perpendicular to each other. The Z-axis direction shown in Figure 1 is the vertical direction and is perpendicular to the X-axis and Y-axis directions.

[0016] The laser oscillator 2 is responsible for emitting the laser beam r. The mirror 3 is responsible for reflecting the laser beam r emitted from the laser oscillator 2 toward the acousto-optic element 4.

[0017] The acousto-optic element 4 plays the role of diffracting the laser beam r emitted from the laser oscillator 2 and emitting primary light. The acousto-optic element 4 is a diffraction grating in which the diffraction direction of the laser beam r is variable. When ultrasonic waves are applied to the acousto-optic element 4, a change in refractive index occurs due to compression waves inside the transparent material that transmits the laser beam r. By modulating the frequency of the ultrasonic waves applied to the acousto-optic element 4, the diffraction direction of the laser beam r can be changed. However, the acousto-optic element 4 also emits undesirable zero-order and secondary light in addition to primary 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 spaced apart from each other 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] Acousto-optic element 4a diffracts the laser beam r emitted from the laser oscillator 2 when ultrasonic waves are applied to it. Acousto-optic element 4a changes the irradiation position of the laser beam r on the workpiece 11 in the X-axis direction. Acousto-optic element 4b diffracts the laser beam r emitted from acousto-optic element 4a when ultrasonic waves are applied to it. 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 both the X-axis and Y-axis directions using the two acousto-optic elements 4a and 4b. The laser processing apparatus 1 can scan an area on the workpiece 11 ranging from 0.1 mm to several mm square at a speed of several hundred m / s using the two acousto-optic elements 4a and 4b.

[0019] The half-wave plate 5 plays the role of rotating the polarization direction of the laser beam r emitted from the acousto-optic element 4 or the angle filter 6 by 90 degrees around the optical axis of the laser beam r. The material of the half-wave plate 5 can be any birefringent material. A birefringent material is, for example, quartz. In this embodiment, there are two half-wave plates 5. In the following description, when distinguishing between the two half-wave plates 5, they will be referred to as half-wave plate 5a and half-wave plate 5b. Half-wave plate 5a is positioned between multiple acousto-optic elements 4a and 4b. Half-wave plate 5a plays the role of rotating 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. Half-wave plate 5b is positioned between multiple angle filters 6a and 6b. The half-wave plate 5b plays the role of rotating 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 angle filter 6 plays the role of separating the desired laser beam r, the primary light, from the unwanted zero-order and secondary light of the laser beam r emitted from the acousto-optic element 4. In this embodiment, there are two angle filters 6. The two angle filters 6 are arranged spaced apart from each other on the optical path of the laser beam r. In the following description, when distinguishing between the two angle filters 6, they will be referred to as angle filter 6a and angle filter 6b. Angle filter 6a diffracts the primary light of the laser beam r emitted from the acousto-optic element 4a. The zero-order and secondary light pass through angle filter 6a without being diffracted. The primary light emitted from angle filter 6a passes through the half-wave plate 5b and is incident on angle filter 6b. Angle filter 6b diffracts the primary light emitted from the acousto-optic element 4b. The zero-order and secondary light pass through angle filter 6b without being diffracted. Details about angle filter 6 will be described later.

[0021] The damper 7 plays the role of absorbing the 0th and 2nd order light of the laser beam r emitted from the acousto-optic element 4. In this embodiment, there are two dampers 7. In the following description, the two dampers 7 will be referred to as damper 7a and damper 7b. Damper 7a is positioned near the angle filter 6a and absorbs the 0th and 2nd order light of the laser beam r emitted from the acousto-optic element 4a. Damper 7b is positioned near the angle filter 6b and absorbs the 0th and 2nd order light of the laser beam r emitted from the acousto-optic element 4b.

[0022] The galvanometer 8 plays the role of reflecting the laser beam r emitted from the angle filter 6. In this embodiment, there are two galvanometers 8. The two galvanometers 8 are spaced apart from each other on the optical path of the laser beam r. In the following description, when distinguishing 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 changes the irradiation position of the laser beam r on the workpiece 11 in the X-axis direction by rotating the galvanometer mirror 8c within a specific range of swing angles. The galvanometer 8b changes the irradiation position of the laser beam r on the workpiece 11 in the Y-axis direction by rotating the galvanometer mirror 8c within a specific range of swing angles. The laser processing apparatus 1 can change the irradiation position of the laser beam r on the workpiece 11 in both the X-axis and Y-axis directions using the two galvanometers 8a and 8b. The laser processing apparatus 1 can scan an area of ​​several tens of mm square on the workpiece 11 at a speed of several m / s using the two galvanometers 8a and 8b.

[0024] The focusing lens 9 plays the role of focusing the laser beam r reflected by the galvanometer 8 and irradiating it onto the workpiece 11. The focusing lens 9 is an fθ lens. The focusing lens 9 irradiates the focused laser beam r onto the workpiece 11 perpendicularly.

[0025] Table 10 holds the workpiece 11 and also moves the position of the workpiece 11. Table 10 holds the workpiece 11 by means of suction or other methods. In this embodiment, Table 10 is movable in the X-axis direction and the Y-axis direction, and the workpiece 11 is movable in the X-axis direction and the Y-axis direction. 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 direction and the Y-axis direction using Table 10. The laser processing apparatus 1 can scan an area of ​​several hundred mm x several hundred mm on the workpiece 11 at a speed of approximately 1 m / s using Table 10. Note that Table 10 may be movable in only one of the X-axis direction or the Y-axis direction.

[0026] The laser processing apparatus 1 can change the irradiation position of the laser beam r on the workpiece 11 using an acousto-optic element 4, a galvanometer 8, and a 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 compared to the scan area of ​​the galvanometer 8 and the movement range of the table 10, but it has a faster operating speed than the galvanometer 8 and the table 10. The galvanometer 8 has a wider scan area compared to the scan area of ​​the acousto-optic element 4, and a narrower scan area compared to the movement range of the table 10, but it has 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 compared to the acousto-optic element 4 and the galvanometer 8, but it has a wider movement range than the scan area 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 illustrating the operation of the angle filter 6 of Embodiment 1. Figure 3 is an enlarged view of part A shown in Figure 2.

[0028] As shown in Figure 2, the angle filter 6 is a transmission-type diffraction grating that transmits the incident laser beam r to produce diffracted light. More specifically, the angle filter 6 is a transmission-type diffraction grating that diffracts the primary light rp such that the angular difference between the primary light ro and the primary light rp is large when the primary light ro and primary light rp emitted from the acousto-optic element 4 pass through the angle filter 6, and the angular difference between the primary light rp and the secondary light rq is large when the primary light rp and secondary light rq emitted from the acousto-optic element 4 pass through the angle filter 6. The angle filter 6 is a blazed diffraction grating capable of obtaining the maximum diffraction efficiency for the diffracted light of the primary light rp.

[0029] Generally speaking, by designing a diffraction grating by specifying the incident direction of the laser beam incident on the diffraction grating and the exit direction of the primary light emitted from the diffraction grating, it is possible to achieve a diffraction efficiency of 95% or more for the primary light. Furthermore, it is possible to make the angular difference between the zeroth-order light and the primary light emitted from the diffraction grating large, for example, 10 degrees or more. Typically, the angular difference between the zeroth-order light ro and the primary light rp, and between the primary light rp and the secondary light rq, emitted from the acousto-optic element 4 are between 0.1 degrees and several degrees. Therefore, in this embodiment, when the zeroth-order light ro and the secondary light rq emitted from the acousto-optic element 4 pass through the angle filter 6, the zeroth-order light ro and the secondary light rq are transmitted without diffraction, while when the primary light rp emitted from the acousto-optic element 4 passes through the angle filter 6, it is possible to diffract the angular difference between the zeroth-order light ro and the primary light rp, and between the primary light rp and the secondary light rq, thereby increasing the angular difference between the zeroth-order light ro and the primary light rp and the secondary 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 Figure 3 will be referred to as the vertical direction. The line passing through the center of the thickness direction of the angle filter 6 along the vertical direction will be referred to as the center line C. The angle filter 6 includes a surface 6c into which the laser beam r is incident and a back surface 6d from which the laser beam r is emitted. Surface 6c is one surface of the angle filter 6 in the thickness direction. Back surface 6d is the other surface of the angle filter 6 in the thickness direction. For simplicity, the surface 6c and back surface 6d of the angle filter 6 are assumed to be symmetrical with respect to the center line C. A grid pattern 6e is provided at regular intervals on both the surface 6c and the back surface 6d. That is, multiple grooves 6f forming the grid pattern 6e are engraved on each of the surface 6c and back surface 6d.

[0031] The groove 6f is composed of a stepped surface 6g and a blazed surface 6h. The stepped surface 6g extends in the direction of the plate thickness. The blazed surface 6h is inclined to approach the center line C as it extends vertically from the tip of the stepped 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 primary light rp can be diffracted, and the zeroth light ro and secondary light rq cannot be diffracted. The zeroth light ro and secondary 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, with reference to Figure 3, the operation of the angle filter 6 of Embodiment 1 will be explained. Here, we assume the case where the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are incident on the same blaze surface 6i on the surface 6c of the angle filter 6. In Figure 3, for ease of understanding, the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are each drawn with a single line. In reality, since the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are wide laser beams compared to the vertical length of a single blaze surface 6h, the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are incident on multiple blaze surfaces 6h. In Figure 3, the blaze surface 6h on the back surface 6d that faces the blaze surface 6i in the thickness direction is defined as blaze surface 6j. Also, the blaze surface 6h located next to blaze surface 6j in one of the vertical directions of blaze surface 6j is defined as blaze surface 6k. Furthermore, the blaze surface 6h located adjacent to blaze surface 6j in the other direction perpendicular to blaze surface 6j is defined as blaze surface 6m.

[0033] The primary light rp is refracted at blaze surface 6i and propagates only to blaze surface 6j. On the other hand, the zeroth-order light ro is refracted at blaze surface 6i and propagates to both blaze surface 6j and blaze surface 6k. The secondary light rq is refracted at blaze surface 6i and propagates to both blaze surface 6j and blaze surface 6m. Since the wavefront of the zeroth-order light ro propagates to both blaze surface 6j and blaze surface 6k, the wavefronts cancel each other out due to the phase difference between blaze surfaces 6j and 6k, i.e., the path difference between blaze surfaces 6j and 6k, and the diffraction efficiency of the zeroth-order light ro is suppressed to approximately 0%. Similarly, since the wavefront of the secondary light rq propagates to both blaze surface 6j and blaze surface 6m, the wavefronts cancel each other out due to the phase difference between blaze surfaces 6j and 6m, i.e., the path difference between blaze surfaces 6j and 6m, and the diffraction efficiency of the secondary light rq is suppressed to approximately 0%. The 0th-order light ro and 2nd-order light rq emitted from the acousto-optic element 4 are not diffracted by the angle filter 6 and are emitted from the back surface 6d at the same angle they were incident on the front surface 6c. On the other hand, the 1st-order light rp propagates only to the blaze surface 6j and not to the blaze surfaces 6k and 6m, so the 1st-order light rp is diffracted with high diffraction efficiency. Only the 1st-order light rp emitted from the acousto-optic element 4 is diffracted by the angle filter 6.

[0034] For only the primary light rp emitted from the acousto-optic element 4 to be diffracted by the angle filter 6, and for the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 to be emitted from the back surface 6d at the same angle as when they were incident on the front surface 6c without being diffracted by the angle filter 6, it is preferable that the following equation (1) is satisfied. In the following equation (1), let d be the thickness of the angle filter 6, n be the refractive index of the angle filter 6, T be the period which is the vertical distance of the groove 6f, and δ be the angle difference between the zeroth light ro and primary light rp emitted from the acousto-optic element 4, and the angle difference between the primary light rp and secondary light rq emitted from the acousto-optic element 4. d ≈ nT / 2δ···(1)

[0035] Furthermore, satisfying equation (2) below can produce the same effect as satisfying equation (1). d = 0.8 ~ 1.2 × nT / 2δ ... (2)

[0036] Figure 4 shows the relationship between the incident angle of the laser beam r and the diffraction efficiency in the angle filter 6 of Embodiment 1. Figure 4 also shows the incident angles of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4. Since the acousto-optic element 4 is a diffraction grating with a variable diffraction direction, the incident angles of the 1st-order light rp and the 2nd-order light rq have an angular range. As is clear from Figure 4, the diffraction efficiency of the 1st-order light rp is higher than that of the 0th-order light ro and the 2nd-order light rq. In other words, the diffraction efficiency of the 0th-order light ro and the 2nd-order light rq are kept lower than that of the 1st-order light rp.

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

[0038] First, we will explain a technique for cutting so that the 0th-order light ro and 2nd-order light rq are not guided toward the workpiece 11. Figure 5 is a perspective view showing an example of a method for absorbing the 0th-order light ro and 2nd-order light rq emitted from the acousto-optic element 4. The laser processing apparatus 1B is equipped with a Keplerian afocal lens 12 positioned between the acousto-optic element 4 and the galvanometer 8. The afocal lens 12 has a pair of convex lenses 13 and 14 and a damper 15 positioned between the pair of convex lenses 13 and 14. An aperture 15a is formed in the damper 15. In the laser processing apparatus 1B, the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4 are first focused by the convex lens 13, and in the focused portion, only the 1st-order light rp passes through the damper 15 through the aperture 15a. The 0th-order light ro and 2nd-order light rq are absorbed by the damper 15. However, in the laser processing apparatus 1B, in order to prevent the 0th-order light ro and 2nd-order light rq from processing the aperture 15a, the aperture 15a is offset in the optical axis direction from the focal point P of the 0th-order light ro and the focal point P of the 2nd-order light rq. Furthermore, in order to prevent the 0th-order light ro and 2nd-order light rq from passing through the aperture 15a, the 0th-order light ro, 1st-order light rp, and 2nd-order light rq must be separated from each other by several millimeters. As a result, the focal length of the convex lens 13 becomes several hundred millimeters, which leads to the problem of increasing the size of the laser processing apparatus 1B and lengthening the optical path.

[0039] While a detailed illustration is omitted, another technique involves separating the acousto-optic element from the galvanometer so that the 0th and 2nd order light emitted from the acousto-optic element misses the galvanometer's galvanometer mirror, thereby reflecting only the 1st order light toward the focusing lens. However, the angular difference between the 0th and 1st order light emitted from the acousto-optic element, and between the 1st and 2nd order light, is usually only about 0.1 to several degrees. Therefore, in order to ensure that the 0th and 2nd order light emitted from the acousto-optic element misses the galvanometer's galvanometer mirror using this method, the acousto-optic element and the galvanometer need to be separated by about 1 meter. This leads to problems such as the need for larger laser processing equipment and longer optical paths.

[0040] In this embodiment, as shown in Figures 1 to 3, the laser processing apparatus 1 is equipped with an angle filter 6 that separates the 0th-order light ro and 2nd-order light rq from the 1st-order light rp of the laser beam r emitted from the acousto-optic element 4. In this embodiment, the angle filter 6 is a transmission-type diffraction grating that diffracts the 1st-order light rp such that the angle difference between the 0th-order light ro and the 1st-order light rp becomes large when the 0th-order light ro and the 1st-order light rp emitted from the acousto-optic element 4 pass through the angle filter 6, and the angle difference between the 1st-order light rp and the 2nd-order light rq becomes large when the 1st-order light rp and the 2nd-order light rq emitted from the acousto-optic element 4 pass through the angle filter 6. With this configuration, the 1st-order light rp is separated from the 0th-order light ro and 2nd-order light rq, guiding only the 1st-order light rp necessary for processing the workpiece 11 toward the workpiece 11, and cutting out the 0th-order light ro and 2nd-order light rq that are unnecessary for processing the workpiece 11. Therefore, processing defects in the workpiece 11 caused by the 0th-order light ro and 2nd-order light rq emitted from the acousto-optic element 4 are suppressed, resulting in a high-quality workpiece 11. Furthermore, with the above configuration, when the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4 pass through the angle filter 6, the angle difference between the 0th-order light ro and 1st-order light rp, and the angle difference between the 1st-order light rp and 2nd-order light rq widens, allowing the 1st-order light rp to be separated from the 0th-order light ro and 2nd-order light rq over a shorter distance than the above technique. This suppresses the need to increase the size of the laser processing apparatus 1 and lengthen the optical path, thus stabilizing the accuracy of the processing position against environmental changes such as temperature. Therefore, in this embodiment, high-speed processing using a beam scanning mechanism composed of the acousto-optic element 4, galvanometer 8, and table 10 can be achieved with high quality and high precision.

[0041] In this embodiment, as shown in Figure 1, the laser processing apparatus 1 is equipped with a damper 7 that absorbs the 0th-order light ro and the 2nd-order light rq of the laser beam r emitted from the acousto-optic element 4. This configuration prevents the 0th-order light ro and the 2nd-order light rq, which are unnecessary for processing the workpiece 11, from irradiating unintended areas.

[0042] In this embodiment, the damper 7a is positioned near the angle filter 6a, so that the 0th-order light ro and 2nd-order light rq emitted from the acousto-optic element 4a are absorbed by the damper 7a. Also in this embodiment, the damper 7b is positioned near the angle filter 6b, so that the 0th-order light ro and 2nd-order light rq emitted from the acousto-optic element 4b are absorbed by the damper 7b. The damper 7 can be positioned, for example, at a distance of several tens of millimeters from the angle filter 6. By positioning the damper 7 in this way, the 0th-order light ro and 2nd-order light rq that have passed through the angle filter 6 are absorbed by the damper 7, thus suppressing the increase in size of the laser processing apparatus 1 and the lengthening of the optical path caused by the placement of the damper 7.

[0043] In this embodiment, as shown in Figure 1, the number of acousto-optic elements 4 and angle filters 6 is multiple. This configuration allows the diffraction direction of the laser beam r by the acousto-optic elements 4 to be 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] In this embodiment, as shown in Figure 1, the laser processing apparatus 1 is equipped with a half-wave plate 5b positioned between a plurality of angle filters 6a and 6b. This configuration allows the polarization direction of the primary light rp emitted from the angle filter 6a to be rotated by 90 degrees around the optical axis of the laser beam r. Generally, diffraction gratings have a higher diffraction efficiency for TE waves, i.e., S-polarized light. By rotating the polarization direction of the primary light rp emitted from the angle filter 6a by 90 degrees around the optical axis of the laser beam r, the diffraction efficiency of the primary light rp in the angle filter 6b can be increased, and higher energy primary light rp can be guided toward the workpiece 11.

[0045] In this embodiment, as shown in Figure 1, the laser processing apparatus 1 includes a half-wave plate 5a positioned between a plurality of acousto-optic elements 4a and 4b. This configuration allows the polarization direction of the primary 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, diffraction gratings have a higher diffraction efficiency for TE waves, i.e., S-polarized light. By rotating the polarization direction of the primary 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 primary light rp in the acousto-optic element 4b can be increased, and higher energy primary light rp can be guided toward the workpiece 11.

[0046] The angle filter 6 only needs to be able to separate the primary light rp from at least one of the 0th-order light ro and the 2nd-order light rq of the laser beam r emitted from the acousto-optic element 4. In other words, the angle filter 6 only needs to be a transmission-type diffraction grating that diffracts the primary light rp such that the angle difference between one of the 0th-order light ro and the 2nd-order light rq and the primary light rp becomes large when the primary light rp passes through the angle filter 6.

[0047] In this embodiment, the front surface 6c and back surface 6d of the angle filter 6 shown in Figure 3 are symmetrical with respect to the center line C. However, as long as the period T of the front surface 6c and back surface 6d coincide, they may be asymmetrical with respect to the center line C. For example, the lattice pattern 6e of the front surface 6c and the lattice pattern 6e of the back surface 6d may be offset from each other in the vertical direction of the paper in Figure 3. There exists an incident angle for the 0th-order light ro, 1st-order light rp, and 2nd-order light rq such that only the 1st-order light rp is diffracted by the angle filter 6, and the 0th-order light ro and 2nd-order light rq are not diffracted by the angle filter 6 and are emitted from the back surface 6d at the same angle as when they were incident on the front surface 6c. The angle filter 6 can be adjusted appropriately to achieve such an incident angle.

[0048] Furthermore, the depth of the blaze surface 6h, i.e., the length of the blaze surface 6h in the thickness direction, may differ between the front surface 6c and the back surface 6d. Even in this case, as long as a grid pattern 6e is provided on both the front surface 6c and the back surface 6d, the same effects as in this embodiment can be achieved.

[0049] In this embodiment, there were two acousto-optic elements 4, half-wave plates 5, angle filters 6, dampers 7, and galvanometers 8, but there may be one or three or more. The half-wave plate 5 may also be omitted. Furthermore, the arrangement of angle filters 6a, 6b and dampers 7a, 7b is not limited to the illustrated example. For example, angle filters 6a and dampers 7a may be placed after acousto-optic element 4a, and angle filters 6b and dampers 7b may be placed after acousto-optic element 4b.

[0050] Figure 6 is a diagram illustrating the operation of an angle filter 6 in a modified example of Embodiment 1. The angle filter 6 may be a volume phase holographic (VPH) diffraction grating as shown in Figure 6. The angle filter 6 is a diffraction grating having fringes of high refractive index and fringes of low refractive index in the perpendicular direction along the surface 6c. In order for only the primary light rp emitted from the acousto-optic element 4 to be diffracted by the angle filter 6, and the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 to be emitted from the back surface 6d at the same angle as when incident on the surface 6c without being diffracted by the angle filter 6, it is preferable that the following equation (3) is satisfied. In equation (3) below, let d be the thickness of the fringed portion of the angle filter 6 that has a refractive index, n be the average refractive index of the fringe with a high refractive index and the fringe with a low refractive index, T be the period which is the vertical distance between the fringe with a high refractive index and the fringe with a low refractive index, and δ be the angular difference between the 0th-order light ro and the 1st-order light rp emitted from the acousto-optic element 4, and the angular difference between the 1st-order light rp and the 2nd-order light rq emitted from the acousto-optic element 4. d ≈ nT / 2δ···(3)

[0051] Furthermore, satisfying equation (4) below can produce the same effect as satisfying equation (3). d = 0.8 ~ 1.2 × nT / 2δ ... (4)

[0052] Embodiment 2. Next, with reference to Figures 7 to 9, the laser processing apparatus 1A according to Embodiment 2 will be described. In this embodiment, the configuration of the angle filter 6 differs from that of Embodiment 1 described above. In Embodiment 2, parts that overlap with those of Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted.

[0053] Figure 7 is a perspective view showing a laser processing apparatus 1A according to Embodiment 2. As shown in Figure 7, the angle filter 6 is a plate-shaped element formed of a material that the laser beam r cannot penetrate. The angle filter 6 has a thickness along the optical axis direction of the laser beam r. The external 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 cannot penetrate 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 a plurality of apertures 6n that penetrate in the direction of the plate thickness. Note that a half-wave plate 5 may be arranged between a plurality of acousto-optic elements 4a, 4b. Figure 8 is a perspective view showing the angle filter 6 of Embodiment 2. The shape of the apertures 6n when viewed along the penetration direction is circular. The plurality of apertures 6n are arranged in a direction intersecting the optical axis direction of the laser beam r. The plurality of apertures 6n are arranged adjacent to each other.

[0054] Next, the operation of the angle filter 6 of Embodiment 2 will be explained with reference to Figure 9. Figure 9 is a diagram illustrating the operation of the angle filter 6 of Embodiment 2, and is a cross-sectional view of the angle filter 6. Here, we assume the case where the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are incident on the same aperture 6n on the surface 6c of the angle filter 6. In Figure 9, for ease of understanding, the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are each drawn with a single line. In reality, since the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are broad laser beams compared to the size D of a single aperture 6n, the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq are incident on multiple apertures 6n.

[0055] The angle filter 6 is configured such that the transmittance of the primary light rp passing through the angle filter 6 is higher than at least one of the transmittance of the zeroth light ro passing through the angle filter 6 and the transmittance of the secondary light rq passing through the angle filter 6. The angle filter 6 is an element arranged such that the transmission direction through which the laser beam r can pass through the angle filter 6 is parallel to the direction of propagation of the primary light rp, and the transmission direction intersects with the direction of propagation of the zeroth light ro and the secondary light rq. The transmission direction is the direction through which the aperture 6n penetrates. That is, the direction of propagation of the primary light rp and the direction through which the aperture 6n penetrates coincide. The direction through which the aperture 6n penetrates with the direction of propagation of the zeroth light ro and the secondary light rq penetrates. By making the penetration direction of aperture 6n parallel to the propagation direction of primary light rp, and intersecting the penetration direction of aperture 6n with the propagation direction of zeroth light ro and secondary light rq, only primary light rp is transmitted through aperture 6n, while zeroth light ro and secondary light rq are blocked by the inner wall surface of aperture 6n, causing zeroth light ro and secondary light rq to be absorbed or scattered by the inner wall surface of aperture 6n.

[0056] For only the primary light rp emitted from the acousto-optic element 4 to pass through the aperture 6n, and for the zeroth-order light ro and secondary light rq emitted from the acousto-optic element 4 to be blocked by the inner wall surface of the aperture 6n, it is preferable that the following equation (5) is satisfied. In the following equation (5), let d be the thickness of the angle filter 6, D be the size of the aperture 6n, δ be the angular difference between the zeroth-order light ro and the primary light rp emitted from the acousto-optic element 4, and δ be the angular difference between the primary light rp and the secondary light rq emitted from the acousto-optic element 4. d≧D / δ···(5)

[0057] In this embodiment, as shown in Figures 7 to 9, the angle filter 6 is a plate-shaped element made of a material that the laser beam r cannot penetrate, and the angle filter 6 has a plurality of apertures 6n that penetrate in the plate thickness direction. With this configuration, only the primary light rp is transmitted through the apertures 6n, and the zeroth light ro and secondary light rq are blocked by the inner wall surface of the apertures 6n, causing the zeroth light ro and secondary light rq to be absorbed or scattered by the inner wall surface of the apertures 6n. This separates the primary light rp from the zeroth light ro and secondary light rq, guiding only the primary light rp necessary for processing the workpiece 11 toward the workpiece 11, and cutting out the zeroth light ro and secondary light rq that are unnecessary for processing the workpiece 11. Therefore, processing defects in the workpiece 11 caused by the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 are suppressed, and a high-quality workpiece 11 can be obtained. Furthermore, with the above configuration, only the primary light rp emitted from the acousto-optic element 4 passes through the angle filter 6, while the zeroth-order light ro and secondary light rq emitted from the acousto-optic element 4 do not pass through the angle filter 6. Therefore, the primary light rp, zeroth-order light ro, and secondary light rq can be separated over a short distance. This suppresses the need to increase the size of the laser processing apparatus 1A and lengthen the optical path, thereby stabilizing the accuracy of the processing position against environmental changes such as temperature. Accordingly, in this embodiment, high-speed processing using a beam scanning mechanism composed of the acousto-optic element 4, galvanometer 8, and table 10 can be achieved with high quality and high precision.

[0058] Furthermore, in this embodiment, as shown in Figures 8 and 9, the shape of the aperture 6n when viewed along the through-direction is circular, so the angle filter 6 does not have directionality in the X-axis and Y-axis directions. Therefore, the angle filter 6 can cut off the 0th-order light ro and 2nd-order light rq in the X-axis direction emitted from the acousto-optic element 4a, and also cut off the 0th-order light ro and 2nd-order light rq in the Y-axis direction emitted from the acousto-optic element 4b. Thus, in this embodiment, at least one angle filter 6 after the acousto-optic element 4 is sufficient. Also, in this embodiment, since the 0th-order light ro and 2nd-order light rq are absorbed or scattered by the inner wall surface of the aperture 6n, the damper 7 can be omitted.

[0059] Figure 10 is a perspective view showing the angle filter 6 of modification 1 of Embodiment 2. Figure 11 is a perspective view showing the angle filter 6 of modification 2 of Embodiment 2. In this embodiment, the shape of the opening 6n when viewed along the through direction was circular, but it may be other than circular. For example, the shape of the opening 6n when viewed along the through direction may be a triangle, a quadrilateral as shown in Figure 10, or a hexagon as shown in Figure 11. Also, the shape of the opening 6n when viewed along the through direction may be an ellipse or a rectangle, but it is preferable to be circular or a regular polygon. In this way, the angle filter 6 can be made to not have directionality in the X-axis direction and the Y-axis direction. That is, the shape of the angle filter 6 becomes symmetrical in the X-axis direction and the Y-axis direction. Regarding the size D of the opening 6n, if the shape of the opening 6n when viewed along the through direction is circular, the diameter of the circle is set as the size D of the opening 6n. If the shape of the opening 6n when viewed along the through direction is elliptical, the major axis of the ellipse is set as the size D of the opening 6n. If the shape of the opening 6n when viewed along the penetration direction is a polygon, the diameter of the circumscribed circle of the polygon is taken as the size D of the opening 6n.

[0060] Examples of methods for manufacturing the angle filter 6 include machining, etching, and die-sinking electrical discharge machining. Alternatively, multiple thin plates with openings 6n created by etching or other methods may be stacked until a predetermined thickness d is reached, and the outer edges of each plate may be clamped with screws or the like, or the plates may be joined together by diffusion bonding, ultrasonic bonding, or the like.

[0061] The angle filter 6, which is a plate-shaped element, may also be an element made by bundling together multiple cylindrical tubes. In such a configuration, the axial direction of the cylindrical tubes should be parallel to the direction of propagation of the primary light rp, and the axial direction of the cylindrical tubes should intersect with the direction of propagation of the zeroth light ro and the secondary light rq. The axial direction of the cylindrical tubes is the transmission direction that allows the laser beam r to pass through the angle filter 6.

[0062] The angle filter 6, which is a plate-shaped element, may be an element formed by bundling multiple fibers made of a material through which the laser beam r passes. For example, multiple glass fibers may be bundled together and sealed with resin, the sealed glass fibers may be cut perpendicular to the length direction of the glass fibers, the cut surfaces may be polished, and an anti-reflective coating may be applied to the cut surfaces to form an element used as the angle filter 6. In such a configuration, the length direction of the fibers should be parallel to the direction of propagation of the primary light rp, and the length direction of the fibers should intersect with the direction of propagation of the zeroth light ro and the secondary light rq. The length direction of the fibers is the transmission direction through which the laser beam r can pass through the angle filter 6.

[0063] The angle filter 6 only needs to be able to separate the primary light rp from at least one of the 0th-order light ro and the 2nd-order light rq of the laser beam r emitted from the acousto-optic element 4. That is, the angle filter 6 is a plate-shaped element and should be arranged such that the transmission direction through which the laser beam r can pass through the angle filter 6 is parallel to the direction of propagation of the primary light rp, and the transmission direction intersects with at least one of the direction of propagation of the 0th-order light ro and the direction of propagation of the 2nd-order light rq. In other words, even when the diffraction direction of the 2nd-order light rq is varied, the angle filter 6 should be configured such that the transmittance of the primary light rp passing through the angle filter 6 is higher than at least one of the transmittance of the 0th-order light ro passing through the angle filter 6 and the transmittance of the 2nd-order light rq passing through the angle filter 6.

[0064] The number of acousto-optic elements 4, angle filters 6, and galvanometers 8 may be changed as appropriate, without being limited to the example shown.

[0065] Embodiment 3. Next, with reference to Figures 12 to 17, the laser processing apparatus 1C according to Embodiment 3 will be described. In this embodiment, the configuration of the angle filter 6 differs from that of Embodiment 2 described above. In Embodiment 3, parts that overlap with those of Embodiment 2 are denoted by the same reference numerals and their description is omitted.

[0066] Figure 12 is a perspective view showing a laser processing apparatus 1C according to Embodiment 3. The angle filter 6 shown in Figure 12 is an etalon. The etalon is a wavelength filter that utilizes the multiple interference of two opposing partial reflectors 6q. The etalon has a periodic transmission spectrum and a narrow full width at half maximum with a sharp transmission peak. The material of the etalon is not particularly limited as long as it can transmit the wavelength of the laser beam r. The material of the etalon may be, for example, glass, quartz, or semiconductor. The etalon used as the angle 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 made from a metamaterial with a refractive index of 0.3 or less with respect to the wavelength of the laser beam r, it is preferable to use a solid etalon as the angle filter 6 because it can obtain more suitable angular characteristics than an air-gap etalon. Note that the half-wave plate 5 may be arranged between a plurality of acousto-optic elements 4a, 4b.

[0067] Figure 13 is a cross-sectional view of the angle filter 6 of Embodiment 3. The angle filter 6 is configured such that the transmittance of the primary light rp transmitted through the angle filter 6 is higher than the transmittance of the zeroth light ro transmitted through the angle filter 6 and the transmittance of the secondary light rq transmitted through the angle filter 6. The angle filter 6 comprises two transparent members 6o and 6p facing each other across a gap G. Each transparent member 6o and 6p is flat. The two transparent members 6o and 6p are arranged parallel to each other. The surface of each transparent member 6o and 6p facing the gap G is a partial reflector 6q.

[0068] Next, with reference to Figure 13, the operation of the angle filter 6 of Embodiment 3 will be described. The laser beam r, incident on the transparent member 6o of the angle filter 6 at an incident angle θ, passes through the transparent member 6o and enters the gap G, where it undergoes multiple reflections between the two partial reflectors 6q and is emitted from the transparent member 6p.

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

[0070] From equation (6) above, when the gap G and incident angle θ are fixed and the wavelength λ is changed, high transmittance can be obtained at a discrete and periodic set of specific wavelengths λ. In other words, the angle filter 6 exhibits a transmission spectrum with a periodic transmission peak. On the other hand, when the gap G and wavelength λ are fixed and the incident angle θ is changed, high transmittance can be obtained at a specific set of incident angles θ, and these specific set of incident angles θ are discrete. In this embodiment, the latter angular characteristic of the etalon was utilized. That is, the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4 have different emission angles and therefore different incident angles θ to the angle filter 6. In this embodiment, only the incident angle θ of the 1st-order light rp is adjusted to match the transmission peak of the angle filter 6. The design parameters of the etalon are the gap G and the reflectance of the partial reflector 6q. The reflectance of the partial reflector 6q is preferably 50% or more.

[0071] Next, with reference to Figures 14 to 17, the angular characteristics and transmission spectrum of the angular filter 6 of Embodiment 3 will be described.

[0072] Figure 14 is an angular characteristic diagram showing the relationship between the incident angle θ and transmittance of the angular filter 6 of Embodiment 3 at the wavelength λ of the laser beam r when the gap G is appropriately set. Figure 14 shows a wide range of angular values ​​for the incident angle θ. The center of Figure 14 in the left-right direction of the paper represents an incident angle θ of 0 degrees, i.e., the laser beam r is incident perpendicularly on the angular filter 6. As is clear from Figure 14, the transmission peak is discrete, and the period of the transmission peak narrows as the incident angle θ increases. In other words, by considering the angular difference between the 0th-order light ro and the 1st-order light rp emitted from the acousto-optic element 4, and the angular difference between the 1st-order light rp and the 2nd-order light rq, and selecting an incident angle θ suitable for the 1st-order light rp, it is possible to achieve high transmittance only for the 1st-order light rp, while keeping the transmittance of the 0th-order light ro and the 2nd-order light rq low.

[0073] Figure 15 is an enlarged view of the area enclosed by the thick dashed line in Figure 14. Figure 15 also shows the incident angles θ of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4. Figure 15 shows the incident angle θ at which only the 1st-order light rp exhibits high transmittance. Since the acousto-optic element 4 is a diffraction grating in which the diffraction direction of the laser beam r is variable, the incident angle θ of the 1st-order light rp and the incident angle θ of the 2nd-order light rq have an angular range. As is clear from Figure 15, the transmittance of the 1st-order light rp is higher than that of the 0th-order light ro and the 2nd-order light rq. In other words, the transmittance of the 0th-order light ro and the 2nd-order light rq are kept lower than that of the 1st-order light rp. In other words, by arranging 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 primary light rp emitted from the acousto-optic element 4 is transmitted, while the zeroth light ro and secondary light rq are reflected, thereby separating the primary light rp from the zeroth light ro and secondary light rq.

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

[0075] In Figure 14, the transmission peak at the center in the horizontal direction of the paper, i.e., at an incident angle θ of 0 degrees, is flatter than the other transmission peaks and has high transmittance over a wide angular range. For this reason, it is preferable to ensure that the primary light rp emitted from the acousto-optic element 4 is incident perpendicularly to the angle filter 6, in order to maintain uniform transmittance of the primary light rp when the diffraction direction of the primary light rp is varied. However, the angular difference from the transmission peak at an incident angle θ of 0 degrees to the adjacent bottom with low transmittance is wider than the angular difference between the 0th-order light ro and the primary light rp, and the angular difference between the primary light rp and the secondary light rq, making it difficult to sufficiently reduce the transmittance of the 0th-order light ro and the secondary light rq. In this case, widening the gap G can narrow the period of the transmission peak in Figure 14, and the incident angle θ of the adjacent bottom with low transmittance can be matched to the incident angle θ of the 0th-order light ro and the secondary light rq. However, widening the gap G also narrows the period of the transmission peak shown in Figure 16, and depending on the width of the oscillation wavelength range of the laser beam r, several transmission peaks will be included in the oscillation wavelength range of the laser beam r shown in Figure 17. As a result, the transmittance of the primary light rp decreases.

[0076] To increase the transmittance of the primary light rp and keep the transmittances of the zeroth light ro and secondary light rq low, it is important to adjust the incident angle θ of the primary light rp, the incident angle θ of the zeroth light ro and the incident angle θ of the secondary light rq by arranging 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. A solid etalon can be fabricated from a metamaterial with a refractive index of 0.3 or less relative to the wavelength of the laser beam r, and when this solid etalon is used as the angle filter 6, both the above-mentioned angular characteristics and transmission spectrum can be satisfied. In other words, while the primary light rp is incident perpendicularly on the angle filter 6, the oscillation wavelength range of the laser beam r can be contained within a single transmission peak in the transmission spectrum.

[0077] In this embodiment, as shown in Figures 12 and 13, the angle filter 6 is an etalon configured such that the transmittance of the primary light rp transmitted through the angle filter 6 is higher than the transmittance of the zeroth light ro transmitted through the angle filter 6 and the transmittance of the secondary light rq transmitted through the angle filter 6. With this configuration, only the primary light rp is transmitted through the angle filter 6, while the zeroth light ro and secondary light rq are reflected by the angle filter 6. This separates the primary light rp from the zeroth light ro and secondary light rq, guiding only the primary light rp necessary for processing the workpiece 11 toward the workpiece 11, and cutting out the zeroth light ro and secondary light rq that are unnecessary for processing the workpiece 11. Therefore, processing defects in the workpiece 11 caused by the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 are suppressed, and a high-quality workpiece 11 can be obtained. Furthermore, with the above configuration, only the primary light rp emitted from the acousto-optic element 4 passes through the angle filter 6, while the zeroth-order light ro and secondary light rq emitted from the acousto-optic element 4 do not pass through the angle filter 6. Therefore, the primary light rp, zeroth-order light ro, and secondary light rq can be separated over a short distance. This suppresses the need to increase the size of the laser processing apparatus 1C and lengthen the optical path, thereby stabilizing the accuracy of the processing position against environmental changes such as temperature. Accordingly, in this embodiment, high-speed processing using a beam scanning mechanism composed of the acousto-optic element 4, galvanometer 8, and table 10 can be achieved with high quality and high precision.

[0078] Furthermore, in this embodiment, by having the primary light rp shown in Figure 13 incident on the etalon, which is the angle filter 6, at an angle other than perpendicular, it is possible to increase the transmittance of the primary light rp while keeping the transmittance of the zeroth light ro and the secondary light rq low.

[0079] Furthermore, in this embodiment, as shown in Figures 14 and 15, the transmittance of the angle filter 6 changes depending on the incident angle θ, so the angle filter 6 does not have directionality in the X-axis and Y-axis directions. For this reason, the angle filter 6 can cut out the 0th-order light ro and 2nd-order light rq in the X-axis direction emitted from the acousto-optic element 4a, and also cut out the 0th-order light ro and 2nd-order light rq in the Y-axis direction emitted from the acousto-optic element 4b. Therefore, in this embodiment, at least one angle filter 6 after the acousto-optic element 4 is sufficient.

[0080] Furthermore, the angle filter 6 only needs to be able to separate the primary light rp from at least one of the 0th-order light ro and the 2nd-order light rq of the laser beam r emitted from the acousto-optic element 4. In other words, the angle filter 6 only needs to be configured such that the transmittance of the primary light rp passing through the angle filter 6 is higher than at least one of the transmittance of the 0th-order light ro passing through the angle filter 6 and the transmittance of the 2nd-order light rq passing through the angle filter 6.

[0081] The number of acousto-optic elements 4, angle filters 6, and galvanometers 8 may be changed as appropriate, without being limited to the example shown.

[0082] Embodiment 4. Next, with reference to Figures 18 to 23, a laser processing apparatus 1D according to Embodiment 4 will be described. This embodiment differs from Embodiment 2 described above in the configuration of the angle filter 6 and the inclusion of a damper 7. In Embodiment 4, parts that overlap with Embodiment 2 are denoted by the same reference numerals and their descriptions are omitted.

[0083] Figure 18 is a perspective view showing a laser processing apparatus 1D according to Embodiment 4. Figure 19 is a diagram illustrating the operation of the angle filter 6 of Embodiment 4. The double arrows labeled Y0, Y1, and Y2 in Figure 19 represent the polarization directions of the 0th-order light ro, the 1st-order light rp, and the 2nd-order light rq, respectively. The double arrow labeled Y3 in Figure 19 represents the polarization direction of the laser beam r when incident on the acousto-optic element 4. The angle filter 6 shown in Figure 18 is an attenuator comprising a waveplate 6r and a polarization beam splitter 6s. As shown in Figure 19, the waveplate 6r causes the polarization direction Y1 of the 1st-order light rp, the polarization direction Y0 of the 0th-order light ro, and the polarization direction Y2 of the 2nd-order light rq to differ by 90 degrees. The polarizing beam splitter 6s is positioned after the waveplate 6r in the optical path of the laser beam r, and either transmits only the primary light rp and reflects the zeroth light ro and secondary light rq, or reflects only the primary light rp and transmits the zeroth light ro and secondary light rq. The attenuator can adjust the ratio of the intensity of the light transmitted through the polarizing beam splitter 6s to the light reflected from the polarizing beam splitter 6s. The angle filter 6 is configured such that the pass-through rate of the primary light rp passing through the angle filter 6 is higher than the pass-through rate of the zeroth light ro and the pass-through rate of the secondary light rq passing through the angle filter 6. Here, "pass-through" means that if the primary light rp is transmitted through the polarizing beam splitter 6s, the zeroth light ro and secondary light rq are also transmitted, and if the primary light rp is reflected through the polarizing beam splitter 6s, the zeroth light ro and secondary light rq are also reflected. Furthermore, the transmittance refers to the transmittance when the primary light rp is transmitted through the polarizing beam splitter 6s, and the reflectance refers to the reflectance when the primary light rp is reflected through the polarizing beam splitter 6s. The material of the waveplate 6r is not particularly limited as long as it is a birefringent material capable of transmitting the wavelength of the laser beam r. The birefringent material may be a uniaxial crystal or a biaxial crystal. For example, the material of the waveplate 6r is quartz. In this embodiment, the waveplate 6r used as the angle filter 6 is a multi-order waveplate.

[0084] As shown in Figure 18, there are two angle filters 6 in this embodiment. In the following description, when distinguishing between the two angle filters 6, they will be referred to as angle filter 6a and angle filter 6b. Also, when distinguishing between the respective waveplates 6r of the two angle filters 6, they will be referred to as waveplate 6r1 and waveplate 6r2. Furthermore, when distinguishing between the respective polarizing beam splitters 6s of the two angle filters 6, they will be referred to as polarizing beam splitter 6s1 and polarizing beam splitter 6s2. In this embodiment, waveplate 6r2 and polarizing beam splitter 6s2 are placed after the acousto-optic element 4b in the optical path of the laser beam r, and waveplate 6r1 and polarizing beam splitter 6s1 are placed after the acousto-optic element 4a in the optical path of the laser beam r. Note that a half-wave plate 5 may be placed between the polarizing beam splitter 6s2 and the acousto-optic element 4a.

[0085] The damper 7 plays the role of absorbing the 0th-order light ro and 2nd-order light rq of the laser beam r emitted from the angle filter 6. In this embodiment, there are two dampers 7. In the following description, the two dampers 7 will be referred to as damper 7a and damper 7b. Damper 7a is positioned near the angle filter 6a and absorbs the 0th-order light ro and 2nd-order light rq of the laser beam r emitted from the angle filter 6a. Damper 7b is positioned near the angle filter 6b and absorbs the 0th-order light ro and 2nd-order light rq of the laser beam r emitted from the angle filter 6b.

[0086] Next, with reference to Figure 19, the operation of the angle filter 6 in Embodiment 4 will be described. Since the operations of angle filters 6a and 6b are the same, only the operation of angle filter 6b, which is positioned after the acousto-optic element 4b in the optical path of the laser beam r, will be described here, and the operation of angle filter 6a will be omitted. The 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4b are incident on the waveplate 6r2 at different angles. Each of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq is linearly polarized. The arrows with the sign V on the surface of the waveplate 6r2 represent the direction of the optical axis of the waveplate 6r2. The polarization directions Y0, Y1, and Y2 of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the waveplate 6r2 either rotate or do not rotate depending on the optical path length in the waveplate 6r2. The design parameter of the waveplate 6r is its thickness (optical path length).

[0087] In this embodiment, the angle between the optical axis direction V of the waveplate 6r2 and the polarization directions Y0, Y1, and Y2 of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq incident on the waveplate 6r2 is 45 degrees. Furthermore, in this embodiment, only the polarization direction Y1 of the 1st-order light rp emitted from the waveplate 6r2 is rotated by 90 degrees, while the polarization directions Y0 and Y2 of the 0th-order light ro and 2nd-order light rq do not rotate and remain the same as the polarization directions Y0 and Y2 when incident on the waveplate 6r2. Moreover, in this embodiment, only the 1st-order light rp is transmitted through the polarizing beam splitter 6s2, while the 0th-order light ro and 2nd-order light rq are reflected by the polarizing beam splitter 6s2. Furthermore, by adjusting the thickness of the waveplate 6r2, or by adjusting the incidence angles of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq to the waveplate 6r2, it is possible to rotate only the polarization direction Y1 of the 1st-order light rp emitted from the waveplate 6r2 by 90 degrees while keeping the polarization directions Y0 and Y2 of the 0th-order light ro and 2nd-order light rq unchanged, as in this embodiment, or to rotate the polarization directions Y0 and Y2 of the 0th-order light ro and 2nd-order light rq by 90 degrees while keeping the polarization direction Y1 of the 1st-order light rp emitted from the waveplate 6r2 unchanged. In the latter case, only the 1st-order light rp is reflected by the polarizing beam splitter 6s2, and the 0th-order light ro and 2nd-order light rq are transmitted through the polarizing beam splitter 6s2.

[0088] Furthermore, by rotating the polarizing beam splitter 6s2 90 degrees around the optical axis from the state shown in Figure 19, it is possible to change the polarization direction Y0, Y1, Y2 of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the waveplate 6r2 without changing them from the state shown in Figure 19, so that only the 1st-order light rp is reflected by the polarizing beam splitter 6s2, while the 0th-order light ro and 2nd-order light rq are transmitted through the polarizing beam splitter 6s2. As described above, by making the polarization direction Y1 of the 1st-order light rp and the polarization direction Y0 of the 0th-order light ro and the polarization direction Y2 of the 2nd-order light rq differ by 90 degrees in the waveplate 6r2, it is possible to either transmit only the 1st-order light rp through the polarizing beam splitter 6s2, or reflect only the 1st-order light rp through the polarizing beam splitter 6s2. The damper 7 should be positioned ahead of the direction of propagation of the 0th-order light ro and 2nd-order light rq, which either pass through the polarizing beam splitter 6s2 or are reflected by the polarizing beam splitter 6s2.

[0089] Next, the angular characteristics and transmission spectrum of the angular filter 6 of Embodiment 4 will be described with reference to Figures 20 to 23.

[0090] Figure 20 is an angular characteristic diagram showing the relationship between the incident angle of the angle filter 6 of Embodiment 4 and the transmittance at the wavelength λ of the laser beam r, when the thickness of the waveplate 6r is appropriately set. Figure 20 shows a wide range of incident angles. The center of Figure 20 in the left-right direction of the paper represents an incident angle of 0 degrees, that is, the laser beam r is incident perpendicularly on the angle filter 6. As is clear from Figure 20, the transmission peak is periodic, and the period of the transmission peak narrows as the incident angle increases. In other words, by considering the angle difference between the 0th-order light ro and the 1st-order light rp emitted from the acousto-optic element 4, and the angle difference between the 1st-order light rp and the 2nd-order light rq, and selecting a suitable incident angle for the 1st-order light rp, it is possible to achieve high transmittance only for the 1st-order light rp, while keeping the transmittance of the 0th-order light ro and the 2nd-order light rq low.

[0091] Figure 21 is an enlarged view of the area enclosed by the thick dashed line in Figure 20. Figure 21 also shows the incident angles of the 0th-order light ro, 1st-order light rp, and 2nd-order light rq emitted from the acousto-optic element 4. Figure 21 shows the incident angle at which only the 1st-order light rp exhibits high transmittance. Since the acousto-optic element 4 is a diffraction grating in which the diffraction direction of the laser beam r is variable, the incident angles of the 1st-order light rp and the 2nd-order light rq have an angular range. As is clear from Figure 21, the transmittance of the 1st-order light rp is higher than that of the 0th-order light ro and the 2nd-order light rq. In other words, the transmittances of the 0th-order light ro and the 2nd-order light rq are kept lower than those of the 1st-order light rp. In other words, by arranging the waveplate 6r of the angle filter 6 shown in Figure 18 at an appropriate angle in the optical path of the laser processing device 1D, the polarizing beam splitter 6s2 shown in Figure 19 can transmit only the primary light rp emitted from the acousto-optic element 4, while reflecting the zeroth light ro and secondary light rq, thereby separating the primary light rp from the zeroth light ro and secondary light rq.

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

[0093] In Figure 20, the transmission peak at the center in the horizontal direction of the paper, i.e., at an incident angle of 0 degrees, is flatter than other transmission peaks and has high transmittance over a wide angular range. For this reason, it is preferable to ensure that the primary light rp emitted from the acousto-optic element 4 is incident perpendicularly to the waveplate 6r, in order to maintain uniform transmittance of the primary light rp when the diffraction direction of the primary light rp is varied. 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 0th-order light ro and the primary light rp, or between the primary light rp and the secondary light rq, and the transmittance of the 0th-order light ro and the secondary light rq cannot be sufficiently reduced. In this case, increasing the thickness of the waveplate 6r can narrow the period of the transmission peak in Figure 20, and the incident angle of the adjacent bottom with low transmittance can be matched to the incident angle of the 0th-order light ro and the secondary light rq. However, increasing the thickness of the waveplate 6r narrows the period of the transmission peak shown in Figure 22, and depending on the width of the oscillation wavelength range of the laser beam r, several transmission peaks will be included in the oscillation wavelength range of the laser beam r shown in Figure 23. As a result, the transmittance of the primary light rp decreases.

[0094] The secondary light rq emitted from the acousto-optic element 4 has a wide angular range when the diffraction direction is varied. Therefore, it is preferable to have the secondary light rq incident perpendicularly to the waveplate 6r and the primary light rp reflected by the angle filter 6, in order to suppress the transmission rate of the secondary light rq. Furthermore, it is possible to change the thickness of the waveplate 6r and invert the angular characteristic diagram in Figure 20. In other words, it is also possible to have the secondary light rq incident perpendicularly to the waveplate 6r reflected by the polarizing beam splitter 6s, and the primary light rp transmitted through the polarizing beam splitter 6s.

[0095] In order to increase the pass-through rate of the primary light rp and keep the pass-through rates of the zeroth light ro and secondary light rq low, it is important to adjust the incident angles of the primary light rp, zeroth light ro, and secondary light rq shown in Figure 19 by positioning the waveplate 6r of the angle filter 6 shown in Figure 18 at an appropriate angle with respect to the optical axis in the optical path of the laser processing device 1D, and to adjust the thickness of the waveplate 6r.

[0096] In this embodiment, as shown in Figures 18 and 19, the angle filter 6 is an attenuator configured such that the pass-through rate of the primary light rp passing through the angle filter 6 is higher than the pass-through rate of the zeroth light ro passing through the angle filter 6 and the pass-through rate of the secondary light rq passing through the angle filter 6. Specifically, the angle filter 6 comprises a waveplate 6r that causes the polarization direction Y1 of the primary light rp to differ by 90 degrees from the polarization direction Y0 of the zeroth light ro and the polarization direction Y2 of the secondary light rq, and a polarizing beam splitter 6s that is placed after the waveplate 6r in the optical path of the laser beam r and transmits only the primary light rp and reflects the zeroth light ro and secondary light rq, or reflects only the primary light rp and transmits the zeroth light ro and secondary light rq. This configuration allows either the primary light rp to pass through the angle filter 6 while the zeroth light ro and secondary light rq are reflected by the angle filter 6, or the primary light rp to be reflected by the angle filter 6 while the zeroth light ro and secondary light rq are passed through the angle filter 6. This separates the primary light rp from the zeroth light ro and secondary light rq, guiding only the primary light rp necessary for processing the workpiece 11 towards the workpiece 11, while cutting out the zeroth light ro and secondary light rq that are not needed for processing the workpiece 11. Therefore, processing defects in the workpiece 11 caused by the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 are suppressed, resulting in a high-quality workpiece 11. Furthermore, with the above configuration, only the primary light rp emitted from the acousto-optic element 4 passes through the angle filter 6, while the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 are reflected by the angle filter 6, or only the primary light rp emitted from the acousto-optic element 4 is reflected by the angle filter 6, while the zeroth light ro and secondary light rq emitted from the acousto-optic element 4 pass through the angle filter 6. This allows the primary light rp to be separated from the zeroth light ro and secondary light rq over a short distance. As a result, the size of the laser processing apparatus 1D and the length of the optical path can be suppressed, and the accuracy of the processing position can be stabilized against environmental changes such as temperature. Therefore, in this embodiment, high-speed processing using a beam scanning mechanism composed of the acousto-optic element 4, galvanometer 8, and table 10 can be achieved with high quality and high precision.

[0097] Furthermore, in this embodiment, by having the primary light rp shown in Figure 19 incident on the waveplate 6r of the angle filter 6 at an angle other than perpendicular, it is possible to increase the transmittance of the primary light rp while keeping the transmittance of the zeroth light ro and the secondary light rq low.

[0098] Furthermore, in this embodiment, as shown in Figures 18 and 19, the laser processing apparatus 1D is equipped with a damper 7 that absorbs the 0th-order light ro and 2nd-order light rq that either pass through the polarizing beam splitter 6s or are reflected by the polarizing beam splitter 6s. This configuration prevents the 0th-order light ro and 2nd-order light rq, which are unnecessary for processing the workpiece 11, from being irradiated to unintended locations.

[0099] Furthermore, the angle filter 6 only needs to be able to separate the primary light rp from at least one of the 0th-order light ro and the 2nd-order light rq of the laser beam r emitted from the acousto-optic element 4. In other words, the angle filter 6 should be positioned such that when at least one of the 0th-order light ro and the 2nd-order light rq and the primary light rp pass through the angle filter 6, the angle difference between at least one of the 0th-order light ro and the 2nd-order light rq and the primary light rp is large. In other words, the angle filter 6 should be configured such that the pass-through rate of the primary light rp passing through the angle filter 6 is higher than at least one of the pass-through rate of the 0th-order light ro passing through the angle filter 6 and the pass-through rate of the 2nd-order light rq passing through the angle filter 6.

[0100] The number of acousto-optic elements 4, angle filters 6, and galvanometers 8 may be changed as appropriate, without being limited to the illustrated example. For example, the angle filter 6, which is placed after the acousto-optic element 4b shown in Figure 18, may be omitted.

[0101] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0102] The various aspects of this disclosure are summarized below as an appendix.

[0103] (Note 1) A laser oscillator that emits a laser beam, An acoustic-optic element that diffracts the laser beam emitted from the laser oscillator, The system includes an angle filter that separates at least one of the 0th and 2nd order light from the 1st order light of the laser beam emitted from the acousto-optic element, The laser processing apparatus is characterized in that the angle filter is configured such that the pass-through rate of the primary light passing through the angle filter is higher than at least one of the pass-through rate of the zeroth-order light passing through the angle filter and the pass-through rate of the secondary light passing through the angle filter. (Note 2) The aforementioned angle filter is A waveplate that causes the polarization direction of the primary light, the polarization direction of the zeroth light, and the polarization direction of the secondary light to differ by 90 degrees, A polarizing beam splitter is positioned after the waveplate in the optical path of the laser beam and transmits only the primary light and reflects the zeroth and secondary light, or reflects only the primary light and transmits the zeroth and secondary light. The laser processing apparatus according to Appendix 1, characterized by comprising the following features. (Note 3) The laser processing apparatus according to Appendix 2, characterized in that the primary light is incident on the waveplate at an angle other than perpendicular. (Note 4) The laser processing apparatus according to Appendix 1, characterized in that the angle filter is an etalon. (Note 5) The laser processing apparatus according to Appendix 4, characterized in that the primary light is incident on the etalon at an angle other than perpendicular. (Note 6) The angle filter is a plate-shaped element formed from a material that the laser beam cannot penetrate. The laser processing apparatus according to Appendix 1, characterized in that the plate-shaped element has a plurality of openings that penetrate in the thickness direction of the plate. (Note 7) The laser processing apparatus according to Appendix 6, characterized in that the shape of the opening when viewed along the through-direction is circular or a regular polygon. (Note 8) The laser processing apparatus according to Appendix 1, characterized in that the angle filter is an element formed by bundling together multiple fibers made of a material through which the laser beam passes. (Note 9) A laser oscillator that emits a laser beam, An acoustic-optic element that diffracts the laser beam emitted from the laser oscillator, The system includes an angle filter that separates at least one of the 0th and 2nd order light from the 1st order light of the laser beam emitted from the acousto-optic element, The laser processing apparatus is characterized in that the angle filter is a transmission type diffraction grating that diffracts the primary light such that the angle difference between one of the primary light and the secondary light and the primary light increases when the primary light and at least one of the primary light and the secondary light emitted from the acoustic-optic element pass through the angle filter. (Note 10) The laser processing apparatus according to Appendix 9, characterized in that the transmission type diffraction grating is a volume-phase holographic type diffraction grating. (Note 11) The aforementioned transmission-type diffraction grating includes a surface to which the laser beam is incident and a back surface from which the laser beam is emitted. The laser processing apparatus according to Appendix 9, characterized in that a grid pattern is provided on the surface and the back surface. (Note 12) The laser processing apparatus according to any one of appendices 1 to 11, characterized in that the number of each of the acousto-optic elements and the angle filters is multiple. (Note 13) The laser processing apparatus according to any one of appendices 1 to 12, characterized in that it comprises at least one damper that absorbs at least one of the 0th order light and the 2nd order light of the laser beam emitted from the acousto-optic element. (Note 14) The laser processing apparatus according to Appendix 12, characterized by comprising a half-wave plate positioned between the plurality of angle filters. (Note 15) The laser processing apparatus according to appendix 12 or 14, characterized by comprising a half-wave plate disposed between the plurality of acousto-optic elements. [Explanation of symbols]

[0104] 1,1A,1B,1C,1D Laser processing equipment, 2 Laser oscillator, 3 Mirror, 4,4a,4b Acousto-optic elements, 5,5a,5b Half-wave plate, 6,6a,6b Angle filter, 6c Front surface, 6d Back surface, 6e Grid pattern, 6f Groove, 6g Step surface, 6h,6i,6j,6k,6m Blaze surface, 6n,15a Aperture, 6o,6p Transmitting member, 6q Partial reflector, 6r,6r1,6r2 Waveplate, 6s,6s1,6s2 Polarizing beam splitter, 7,7a,7b,15 Damper, 8,8a,8b Galvanometer, 8c Galvano mirror, 8d Galvano motor, 9 Focusing 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 waveplate, Y0, Y1, Y2, Y3 polarization direction.

Claims

1. A laser oscillator that emits a laser beam, An acoustic-optic element that diffracts the laser beam emitted from the laser oscillator, The system includes an angle filter that separates at least one of the zeroth and second-order light from the first-order light of the laser beam emitted from the acousto-optic element, The laser processing apparatus is characterized in that the angle filter is positioned close to the acousto-optic element such that a portion of the primary light and a portion of the zeroth-order light overlap with a portion of the primary light and a portion of the secondary light, and the pass-through rate of the primary light passing through the angle filter is higher than at least one of the pass-through rate of the zeroth-order light passing through the angle filter and the pass-through rate of the secondary light passing through the angle filter.

2. The aforementioned angle filter is A waveplate that causes the polarization direction of the primary light, the polarization direction of the zeroth light, and the polarization direction of the secondary light to differ by 90 degrees, A polarizing beam splitter is positioned after the waveplate in the optical path of the laser beam and transmits only the primary light and reflects the zeroth and secondary light, or reflects only the primary light and transmits the zeroth and secondary light. The laser processing apparatus according to claim 1, characterized by comprising:

3. The laser processing apparatus according to claim 2, characterized in that the primary light is incident on the waveplate at an angle other than perpendicular.

4. The laser processing apparatus according to claim 1, characterized in that the angle filter is an etalon.

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

6. The angle filter is a plate-shaped element formed from a material that the laser beam cannot penetrate. The laser processing apparatus according to claim 1, characterized in that the plate-shaped element has a plurality of openings that penetrate in the thickness direction of the plate.

7. The laser processing apparatus according to claim 6, characterized in that the shape of the opening when viewed along the through-direction is circular or a regular polygon.

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

9. A laser oscillator that emits a laser beam, An acoustic-optic element that diffracts the laser beam emitted from the laser oscillator, The system includes an angle filter that separates at least one of the zeroth and second-order light from the first-order light of the laser beam emitted from the acousto-optic element, The laser processing apparatus is characterized in that the angle filter is a transmission type diffraction grating that diffracts the primary light such that the angle difference between one of the zeroth-order light and the secondary light and the primary light increases when the primary light and at least one of the zeroth-order light and the secondary light emitted from the acoustic-optic element pass through the angle filter.

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

11. The aforementioned transmission-type diffraction grating includes a surface to which the laser beam is incident and a back surface from which the laser beam is emitted. The laser processing apparatus according to claim 9, characterized in that a grid pattern is provided on the surface and the back surface.

12. The laser processing apparatus according to claim 1 or 9, characterized in that the number of each of the acousto-optic elements and the angle filters is multiple.

13. The laser processing apparatus according to claim 1 or 9, further comprising 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.

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

15. The laser processing apparatus according to claim 12, characterized in that it comprises a half-wave plate disposed between the plurality of acoustic-optic elements.

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