Optical modulation unit and phase difference generation device

Abstract

Provided is a phase modulation device capable of controlling a phase by increasing the output of a laser beam. The phase modulation device comprises: at least one mirror including a reflective surface; and a plurality of driving elements arranged on a side opposite to the reflective surface of the at least one mirror, wherein the reflective surface is displaced by the plurality of driving elements.

Description

Optical modulation unit and phase difference generator

[0001] The present disclosure relates to a light modulation unit and a phase difference generating device.

[0002] In laser processing such as laser welding, it has been considered to change the beam profile at the processing point where the laser light is focused.

[0003] For example, Patent Document 1 discloses an optical modulation device including a spatial light modulator, a light source, and a focusing optical system. In the optical modulation device of Patent Document 1, the spatial light modulator includes a modulation unit having a plurality of pixels and modulating the phase or intensity of incident light for each pixel in accordance with the amplitude of a drive signal that periodically changes over time, and a drive circuit that provides the drive signal to the modulation unit. The plurality of pixels in the modulation unit include a first pixel group whose longitudinal direction is a predetermined direction and a second pixel group whose longitudinal direction is the same direction, and the first pixel group and the second pixel group are alternately arranged in a direction intersecting the predetermined direction. The drive circuit controls the phase of the drive signal provided to the first pixel group among the plurality of pixels to be inverted relative to the phase of the drive signal provided to the second pixel group among the plurality of pixels, thereby variably controlling the boundary between the first pixel group and the second pixel group. At least a portion of the first pixel group and at least a portion of the second pixel group are within an illumination area of ​​the incident light. The light source provides the incident light to the modulation unit. The light collecting optical system collects the modulated light output from the modulation section.

[0004] Patent No. 7111678 Publication Special Publication No. 2023-540013

[0005] A phase modulation device according to one aspect of the present disclosure is a phase modulation device for controlling the phase of laser light, and comprises at least one mirror including a reflective surface and a plurality of drive elements arranged on the opposite side of the reflective surface of the at least one mirror, and displaces the reflective surface by the plurality of drive elements.

[0006] A method for manufacturing a phase modulation device according to one aspect of the present disclosure includes the steps of fixing a plurality of driving elements to a base plate, arranging an intermediate substrate so as to cover the plurality of driving elements, arranging at least one mirror so as to cover the intermediate substrate, and irradiating a cutting laser having a wavelength that is transmitted through the mirror through the mirror to cut the intermediate substrate and form a plurality of intermediate plates.

[0007] 1 is a schematic diagram illustrating an optical modulation unit according to a first embodiment of the present disclosure; FIG. 2 is a diagram illustrating an example of a beam pattern of a parallel laser beam after being branched by a branching section when viewed in a direction parallel to the optical axis; FIG. 3 is a perspective view illustrating a phase difference generating section of the optical modulation unit of FIG. 1;Schematic diagrams for explaining the operation that causes a phase difference. A diagram showing an example of the beam profile (a) and the intensity distribution (b) at the collection spot. A diagram showing an example of the beam profile (a) and the intensity distribution (b) at the collection spot. A diagram showing an example of the beam profile (a) and the intensity distribution (b) at the collection spot. A diagram showing an example of the beam profile (a) and the intensity distribution (b) at the collection spot. A diagram showing an example of the beam profile (a) and the intensity distribution (b) at the collection spot. A diagram showing an example of the beam profile (a) and the intensity distribution (b) at the collection spot. A schematic diagram for explaining the positional relationship between a plurality of parallel laser beams and a plurality of mirrors according to a modified example of Embodiment 1. A plan view schematically showing the phase modulation device according to Embodiment 2. A cross-sectional view of the phase modulation device of FIG. 1. A cross-sectional view showing a state in which the intermediate plate is displaced by driving the drive element of the phase modulation device of FIG. 10. A schematic diagram showing a state in which laser light is reflected in the phase modulation device of FIG. 10. A schematic diagram showing a state in which laser light is reflected in the phase modulation device of FIG. 11. A flowchart for explaining the manufacturing method of the phase modulation device. A plan view schematically showing the manufacturing process of the phase modulation device. A cross-sectional view schematically showing the manufacturing process of the phase modulation device. A plan view schematically showing the manufacturing process of the phase modulation device. A cross-sectional view schematically showing the manufacturing process of the phase modulation device. A plan view schematically showing the manufacturing process of the phase modulation device. A cross-sectional view schematically showing the manufacturing process of the phase modulation device. A plan view schematically showing the manufacturing process of the phase modulation device. A cross-sectional view schematically showing the manufacturing process of the phase modulation device. A plan view schematically showing the manufacturing process of the phase modulation device. A cross-sectional view schematically showing the manufacturing process of the phase modulation device. A flowchart for explaining the manufacturing method of the phase modulation device according to Modified Example 1 of Embodiment 2. A diagram schematically showing the laser welding device according to Embodiment 3. A diagram for explaining the generation of stray light in the phase modulation device. A block diagram schematically showing the configuration of the phase modulation device according to Embodiment 4. A schematic diagram showing an example of a segment in the phase modulation device of FIG. 28. A schematic diagram showing an example of a segment in the phase modulation device of FIG. 28. A schematic diagram showing an example of a segment in the phase modulation device of FIG. 28,

[0008] In the optical modulation device described in Patent Document 1, there is still room for improvement in terms of increasing the output of the laser light and dynamically changing the beam profile.

[0009] The present disclosure provides a light modulation unit and a phase difference generating device that can dynamically change the beam profile by increasing the output of laser light.

[0010] An optical modulation unit according to one aspect of the present disclosure is an optical modulation unit for controlling the beam profile of laser light, and includes: a branching section that branches laser light emitted from a laser oscillator into a plurality of parallel laser beams; and a phase difference generating section that generates a phase difference and reflects the plurality of parallel laser beams, wherein the phase difference generating section has: a plurality of first reflecting surfaces that reflect the plurality of parallel laser beams; and a plurality of modulating sections that change the optical path lengths of the plurality of parallel laser beams by changing the positions of the plurality of first reflecting surfaces.

[0011] A phase difference generating device according to one aspect of the present disclosure is a phase difference generating device that generates a phase difference and reflects a plurality of parallel laser beams, and includes: a plurality of reflecting surfaces that reflect the plurality of parallel laser beams; and a plurality of modulation units that change the optical path lengths of the plurality of parallel laser beams by changing the positions of the plurality of reflecting surfaces.

[0012] According to the present disclosure, it is possible to provide a light modulation unit and a phase difference generating device that can dynamically change the beam profile by increasing the output of laser light.

[0013] (Background to the present disclosure) Changing the beam profile at the processing point of laser processing has been studied. For example, a technology for generating a phase difference using a reflective liquid crystal display panel called LCOS (Liquid Crystal On Silicon), in which a reflective layer and liquid crystal are formed on a silicon substrate, is known. In LCOS, a phase difference is generated by transmitting laser light through liquid crystal. The beam profile at the processing point is changed by changing the pattern displayed on the liquid crystal. For example, Patent Document 1 describes an example of an optical modulation device using LCOS.

[0014] In the conventional LCOS configuration, laser light is transmitted through a liquid crystal panel, which poses a problem in that the beam profile cannot be dynamically changed by increasing the output of the laser light.

[0015] Furthermore, studies are being conducted to change the beam profile using coherent beam combining (CBC) technology.

[0016] Although CBC technology can increase the output of laser light and dynamically change the beam profile, it requires a dedicated laser oscillator, which has the drawback that it cannot be retrofitted to the laser oscillator of an existing laser processing device. Another drawback is that laser oscillators configured using CBC technology are very expensive.

[0017] The inventors have studied an optical modulation unit and a phase difference generating device that can increase the output of laser light to dynamically change the beam profile and that can be retrofitted to existing laser processing equipment, and have arrived at the following invention.

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In each drawing, elements are exaggerated for ease of explanation.

[0019] As used herein, terms such as "first," "second," etc. are used for descriptive purposes only and should not be understood as expressing or implying relative importance or ranking of technical features. Features qualified as "first" and "second" expressly or imply the inclusion of one or more of that feature.

[0020] First Embodiment [Overall Configuration] FIG. 1 is a schematic diagram illustrating an optical modulation unit according to a first embodiment of the present disclosure.

[0021] The light modulation unit 100 according to this embodiment is a device that splits a laser beam 2 emitted from a laser oscillator 1 into a plurality of parallel laser beams 13, generates a phase difference between the beams, and reflects the beams toward a condenser lens 31. The light modulation unit 100 includes a splitting section 10 and a phase difference generating section 20. In this embodiment, the light modulation unit 100 includes a folding optical element 15, but the folding optical element 15 is not an essential component of the light modulation unit 100.

[0022] As shown in FIG. 1 , a laser beam 2 emitted from a laser oscillator 1 is branched into multiple parallel laser beams 13 by a branching unit 10. The multiple parallel laser beams 13 are reflected by a mirror 16 of a folding optical element 15 and reach a phase difference generating unit 20. The phase difference generating unit 20 generates a phase difference in the multiple parallel laser beams 13 and reflects them. The phase difference generating unit 20 imparts a different phase difference to each parallel laser beam 13. The multiple parallel laser beams 13 reflected by the phase difference generating unit 20 are reflected by a mirror 17 of the folding optical element 15 and converged at a convergence point 32 on a workpiece 33 via a condenser lens 31. Due to the phase difference applied by the phase difference generating unit 20, an arbitrary beam profile can be obtained when the multiple parallel laser beams 13 are converged at the convergence point 32. In this embodiment, the wavelength of the laser beam 2 emitted from the laser oscillator 1 is, for example, 1070 nm.

[0023] Next, the components of the light modulation unit 100 will be described.

[0024] The branching unit 10 includes a diffractive optical element (DOE) 11 and a collimator lens 12. The diffractive optical element 11 is an optical element that can branch a laser beam by utilizing the diffraction phenomenon of light. The collimator lens 12 is a lens that converts multiple laser beams into parallel beams. In the branching unit 10, the multiple laser beams branched by the diffractive optical element 11 are collimated using the collimator lens 12 to form multiple parallel laser beams 13.

[0025] 2 is a diagram illustrating an example of a beam pattern of the collimated laser beam 13 after being split by the splitter 10, as viewed in a direction parallel to the optical axis. In this embodiment, as shown in FIG. 2, the laser beam 2 from the laser oscillator 1 can be split into a plurality of collimated laser beams 13 in a 5×5 lattice pattern by the diffractive optical element 11 and the collimator lens 12. In this embodiment, the plurality of collimated laser beams 13 are arranged in a square lattice array.

[0026] 1 , the phase difference generating unit 20 has a plurality of first reflecting surfaces 22 that reflect the plurality of collimated laser beams 13, and a plurality of modulating units 23 that change the optical path lengths of the plurality of collimated laser beams 13 by changing the positions of the plurality of first reflecting surfaces 22. The phase difference generating device 20 corresponds to the "phase difference generating device" of the present disclosure.

[0027] 3 is a perspective view schematically illustrating the phase difference generating section 20 of the light modulation unit 100 of FIG. 1. As shown in FIG. 3, in this embodiment, the phase difference generating section 20 has a plurality of mirrors 22 arranged in a 5×5 lattice pattern and a plurality of piezoelectric elements 23 bonded to the opposite sides of the reflective surfaces of the plurality of mirrors 22. In this embodiment, the plurality of mirrors 22 are arranged in a square lattice array. The plurality of mirrors 22 correspond to a plurality of first reflective surfaces, and the plurality of piezoelectric elements 23 correspond to a plurality of modulation sections. That is, in this embodiment, the plurality of modulation sections are composed of a plurality of piezoelectric elements 23. As shown in FIG. 3, one piezoelectric element 23 is arranged for one mirror 22.

[0028] An electrode (not shown) is provided on each of the plurality of piezoelectric elements 23. By applying a voltage to the electrode provided on each of the plurality of piezoelectric elements 23, the plurality of piezoelectric elements 23 can be expanded and contracted in a direction intersecting with the reflective surface of the mirror 22.

[0029] In the example of FIG. 3, the mirror 22 and the piezoelectric element 23 have bonding surfaces of the same size, but the bonding surface of the piezoelectric element 23 may be smaller than the bonding surface of the mirror 22 .

[0030] Furthermore, in this embodiment, the phase difference generating unit 20 has a temperature maintaining base 24 that maintains the temperature of the multiple piezoelectric elements 23 constant, and the multiple piezoelectric elements 23 are arranged on the temperature maintaining base 24. The temperature maintaining base 24 is not an essential component of the phase difference generating unit 20 and does not have to be included in the phase difference generating unit 20. The temperature maintaining base 24 can maintain the multiple piezoelectric elements 23 at a constant temperature, for example, by circulating water at a constant temperature inside. Alternatively, the temperature maintaining base 24 can be configured, for example, with a temperature sensor and a Peltier element, and can maintain the temperature of the multiple piezoelectric elements 23 constant by detecting the temperature of the multiple piezoelectric elements 23 and heating or cooling them.

[0031] The multiple parallel laser beams 13 from the branching section 10 are reflected by the mirror 16 of the folding optical element 15 toward the phase difference generating section 20, and the multiple parallel laser beams 13 reflected by the phase difference generating section 20 are reflected by the mirror 17 of the folding optical element 15 toward the focusing lens 31.

[0032] The folding optical element 15 has a second reflecting surface and a third reflecting surface. The second reflecting surface corresponds to a mirror 16 and reflects the plurality of parallel laser beams 13 from the branching unit 10 toward the phase difference generating unit 20. The third reflecting surface corresponds to a mirror 17 and reflects the plurality of parallel laser beams 13 reflected by the phase difference generating unit 20 toward a focusing position.

[0033] The mirror 16 of the folding optical element 15 is arranged so that the reflection angle of the parallel laser beams 13 at the mirrors 22 of the phase difference generating unit 20 is as small as possible. Specifically, the mirror 16 is arranged so that the reflection angle of the parallel laser beams 13 at each of the reflecting surfaces of the mirrors 22 is 30 degrees or less. By making the reflection angle of the parallel laser beams 13 at each mirror 22 30 degrees or less, it is possible to prevent the generated phase difference from deviating from a desired value.

[0034] Fig. 4 is a perspective view schematically showing a state in which a plurality of parallel laser beams 13 are irradiated onto the phase difference generating unit 20 of Fig. 3. As shown in Fig. 4, one beam of the plurality of parallel laser beams 13 is irradiated onto one of the plurality of mirrors 22. Therefore, the plurality of mirrors 22 are arranged in the same manner as the plurality of parallel laser beams 13. Specifically, as described above, the plurality of parallel laser beams 13 are laser beams branched into a 5 x 5 lattice pattern, and therefore the plurality of mirrors 22 are also arranged in a 5 x 5 lattice pattern. Therefore, there is a one-to-one correspondence between the plurality of parallel laser beams 13 and the plurality of mirrors 22.

[0035] Fig. 5 is an enlarged view of region R1 in Fig. 4. The positional relationship between the collimated laser beams 13 and the mirror 22 will be described with reference to Fig. 5. The plurality of collimated laser beams 13 are, for example, laser beams having a beam diameter Φ of 3 mm. In this embodiment, the pitch p1 between adjacent collimated laser beams 13 is 5 mm. That is, the distance between the centers c1 of adjacent collimated laser beams 13 is 5 mm.

[0036] As shown in FIG. 5 , the mirror 22 is, for example, a square mirror with a side length d1 of 5 mm. The side length d1 of the mirror 22 is set to be larger than the beam diameter Φ of the parallel laser beam 13. The mirrors 22 are arranged in a 5×5 square lattice array to match the arrangement of the parallel laser beams 13. The mirrors 22 are arranged so that a gap s1 is formed between adjacent mirrors 22. The size of the gap s1 is, for example, 20 μm, which is set to a size that prevents contact between adjacent mirrors 22 and adjacent piezoelectric elements 23. By forming the gap s1 so that the adjacent mirrors 22 and adjacent piezoelectric elements 23 do not contact each other, interference between the piezoelectric elements 23 can be suppressed. The size of the gap s1 can be set within a range that prevents the parallel laser beams 13 from entering the gap s1. For example, the size of the gap s1 can be set within a range of 1 μm to 100 μm. By setting the size of the gap s1 in the range of 1 μm to 100 μm, irradiation of the gap s1 with multiple parallel laser beams 13 can be suppressed, thereby reducing energy loss. Furthermore, by setting the size of the gap s1 in the range of 1 μm to 100 μm, the laser beams are less likely to reach the gap s1. Therefore, even when the laser oscillator 1 emits high-power laser beams on the kW level, damage to the phase difference generating unit 20 by the laser beams can be suppressed. Therefore, high-power laser beams can be stably used in the optical modulation unit 100.

[0037] The plurality of mirrors 22 can be set to any shape and size depending on the beam diameter Φ of the plurality of parallel laser beams 13 and the distribution of the lattice arrangement, etc. For example, the length of one side of the plurality of mirrors 22 can be set to 2 mm or more and 10 mm or less.

[0038] 6 is a schematic diagram for explaining the operation of generating a phase difference in the phase difference generating unit 20 of FIG. 3. As shown in FIG. 6, in the phase difference generating unit 20, the multiple modulation units 23, i.e., the multiple piezoelectric elements 23, expand and contract in a direction intersecting the reflecting surfaces of the multiple mirrors 22. By expanding and contracting each of the multiple piezoelectric elements 23, the positions of the reflecting surfaces of the multiple mirrors 22 can be moved in a direction intersecting the reflecting surfaces of the mirrors 22. By changing the positions of the reflecting surfaces of the multiple mirrors 22, the optical path lengths of the multiple parallel laser beams 13 can be changed. The amount of expansion and contraction of the piezoelectric elements 23 can be adjusted by the voltage applied to the piezoelectric elements 23.

[0039] 6, the mirrors 22a to 22c are arranged at different positions in the direction perpendicular to the reflecting surface due to the expansion and contraction of the piezoelectric element 23. Therefore, the parallel laser beams 13a to 13c irradiated onto the mirrors 22a to 22c have different optical path lengths.

[0040] 6, the phase of the collimated laser beam 13b reflected by the central mirror 22b is advanced by δ1 relative to the phase of the collimated laser beam 13a reflected by the left mirror 22a. On the other hand, the phase of the collimated laser beam 13c reflected by the right mirror 22c is delayed by δ2 relative to the phase of the collimated laser beam 13a reflected by the left mirror 22a. In this way, by controlling the voltage applied to the piezo element 23, the phase of each collimated laser beam 13 can be controlled, and a desired phase difference can be imparted to the plurality of collimated laser beams 13.

[0041] The voltage applied to the piezo elements 23 is generated by a drive signal generator 40 shown in Fig. 1. The voltage generated by the drive signal generator 40 is applied to each piezo element 23. The drive signal generator 40 applies to each piezo element 23 a voltage sufficient to move the piezo element 23 a distance equal to or greater than the wavelength of the laser light 2 emitted from the laser oscillator 1.

[0042] In this embodiment, the wavelength of the laser light 2 emitted from the laser oscillator 1 is 1070 nm. For example, if the voltage generated by the drive signal generator 40 to move the laser light 2 over a distance of approximately 1070 nm, which is the same as the wavelength of the laser light 2, is Vmax, the drive signal generator 40 can control the voltage applied to the piezoelectric element 23 in, for example, 64 steps between 0 and Vmax. The voltage generated by the drive signal generator 40 may also be controlled in 16 steps or more and 256 steps or less.

[0043] The plurality of parallel laser beams 13 to which phase differences have been added in the phase difference generating unit 20 are reflected by the mirror 17 of the folding optical element 15 and directed toward a focusing position. In this embodiment, the plurality of parallel laser beams 13 are focused at a focusing point 32 on a processing object 33 via a focusing lens 31 shown in FIG.

[0044] The condensing lens 31 is a lens for condensing the plurality of parallel laser beams 13 to which a phase difference has been added, at a condensing point 32. By controlling the phase difference of the plurality of parallel laser beams 13, the plurality of parallel laser beams 13 are condensed via the condensing lens 31, and various beam profiles can be generated at the condensing point 32.

[0045] 7A to 7F are diagrams showing an example of a beam profile (a) and an intensity distribution (b) at the focal point 32. FIG.

[0046] For example, Figure 7B shows an example in which the most intense part of the beam is located at the intersection of the x-axis and y-axis. In Figure 7A, the most intense part of the beam is shifted in the -x direction from Figure 7B. In Figure 7C, the most intense part of the beam is shifted in the +x direction from Figure 7B. Therefore, by imparting a phase difference to the collimated laser light 13 so that the beam moves in the order of Figures 7A, 7B, and 7C, it is possible to move the most intense part of the beam.

[0047] Also, as shown in Fig. 7D, a ring-shaped beam profile can be generated. As shown in Fig. 7E, two branched beam profiles can be generated at the focal point 32. Furthermore, as shown in Fig. 7F, a line-shaped beam profile can be generated. In this way, by controlling the phases of the respective parallel laser beams 13 with the phase difference generating unit 20, a desired beam profile can be obtained at the focal point 32.

[0048] [Effects] According to the above-described embodiment, the following effects can be achieved.

[0049] The optical modulation unit 100 is a unit for controlling the beam profile of laser light. The optical modulation unit 100 includes a branching unit 10 and a phase difference generating unit 20. The branching unit 10 branches the laser light 2 emitted from the laser oscillator 1 into a plurality of parallel laser light beams 13. The phase difference generating unit 20 includes a plurality of first reflecting surfaces 22 that reflect the plurality of parallel laser light beams 13, and a plurality of modulators 23 that change the optical path lengths of the plurality of parallel laser light beams 13 by changing the positions of the plurality of first reflecting surfaces 22.

[0050] This configuration provides a light modulation unit 100 and a phase difference generating device that can dynamically change the beam profile by increasing the output of the laser beam. Because the branching unit 10 and the phase difference generating unit 20 can be attached to an existing laser processing device, a desired beam profile can be achieved using the light modulation unit 100 in the existing laser processing device. By using the light modulation unit 100, any desired beam profile and intensity profile can be obtained at the focal point 32 on the workpiece 33. Furthermore, because the optimal profile can be obtained in real time during laser processing, it is possible to improve the productivity of laser processing by suppressing spatter during laser welding or increasing the cutting speed during laser cutting. Furthermore, the light modulation unit 100 can be used with high-power laser beams without being damaged. Furthermore, it can be retrofitted to existing laser processing devices.

[0051] The branching section 10 has a diffractive optical element 11 that branches the laser light 2 emitted from the laser oscillator 1 into multiple laser lights, and a collimator lens 12 that collimates the multiple branched laser lights to generate multiple parallel laser lights 13.

[0052] With this configuration, the laser light 2 from the laser oscillator 1 can be branched in a desired pattern.

[0053] The plurality of first reflecting surfaces are formed by a plurality of mirrors 22 .

[0054] With this configuration, a phase difference can be easily given to the plurality of parallel laser beams 13 .

[0055] The plurality of first reflecting surfaces are arranged in a grid pattern when viewed from a direction perpendicular to the reflecting surfaces.

[0056] With this configuration, the plurality of first reflecting surfaces can be arranged in accordance with the branching pattern of the plurality of parallel laser beams 13 .

[0057] The plurality of first reflecting surfaces are arranged in a square lattice array when viewed from a direction perpendicular to the first reflecting surfaces.

[0058] With this configuration, the phase difference generating section 20 can have a simple configuration.

[0059] A gap of 1 μm or more and 100 μm or less is formed between adjacent first reflecting surfaces.

[0060] With this configuration, the gap is less likely to be irradiated with laser light, and damage to the light modulation unit 100 can be suppressed.

[0061] The plurality of modulation sections are configured by a plurality of expansion and contraction sections that expand and contract in a direction intersecting the first reflecting surface.

[0062] With this configuration, the position of the first reflecting surface can be easily changed.

[0063] The plurality of modulation sections are constituted by a plurality of piezoelectric elements 23. The plurality of piezoelectric elements 23 are bonded to the opposite side of each of the plurality of first reflecting surfaces.

[0064] With this configuration, the position of the first reflecting surface can be changed with high precision.

[0065] The temperature maintaining base is further provided to maintain the temperature of the plurality of modulation sections constant. The plurality of modulation sections are disposed on the temperature maintaining base.

[0066] With this configuration, the temperature of the modulation section can be kept constant, and therefore, changes in the position of the modulation section or the first reflecting surface due to a rise or fall in temperature can be suppressed.

[0067] Furthermore, it is provided with a folding optical element 15 having a second reflecting surface that reflects the multiple parallel laser beams 13 from the branching section 10 toward the phase difference generating section 20, and a third reflecting surface that reflects the multiple parallel laser beams 13 reflected by the phase difference generating section 20 toward a focusing position.

[0068] With this configuration, the angle of reflection on the first reflecting surface of the phase difference generating section 20 can be controlled, and therefore the phase difference between the plurality of parallel laser beams 13 can be controlled more accurately.

[0069] The second reflecting surfaces are arranged at positions where the reflection angles of the parallel laser beams 13 on each of the plurality of reflecting surfaces are 30 degrees or less.

[0070] With this configuration, it is possible to prevent the generated phase difference from deviating from a desired value.

[0071] In the above-described embodiment, an example has been described in which the plurality of first reflecting surfaces of the phase difference generating unit 20 are configured by the plurality of mirrors 22, but the present invention is not limited to this. The plurality of first reflecting surfaces may be optical elements having reflecting surfaces, such as prisms.

[0072] In the above-described embodiment, the multiple modulation sections of the phase difference generating section 20 are configured with multiple piezoelectric elements 23, but the present invention is not limited to this. The multiple modulation sections may be any device that can change the position of the reflecting surface, such as a voice coil. Alternatively, the multiple modulation sections may be configured with multiple expansion sections that expand and contract in a direction intersecting the multiple reflecting surfaces.

[0073] In the above-described embodiment, the folding optical element 15 has two mirrors 16 and 17. However, the folding optical element 15 is not limited to this. The folding optical element 15 may be an optical element having two reflecting surfaces, such as a prism.

[0074] In the above-described embodiment, the branching unit 10 branches the laser beam 2 into a plurality of parallel laser beams 13 arranged in a square lattice pattern, but the present invention is not limited to this. The plurality of parallel laser beams 13 may be arranged in a lattice pattern, a radial pattern, or a concentric pattern, for example.

[0075] In the above-described embodiment, the plurality of mirrors 22 are arranged in a square lattice pattern, but the present invention is not limited to this. The plurality of mirrors 22 can be arranged in a lattice pattern, a radial pattern, or a concentric pattern depending on the arrangement of the plurality of parallel laser beams 13 branched by the branching unit 10.

[0076] 8 is a schematic diagram for explaining the positional relationship between the plurality of parallel laser beams 113 and the plurality of mirrors 122 according to the modification of the first embodiment. As shown in Fig. 8, the plurality of parallel laser beams 13 may be arranged concentrically or radially when viewed from a direction parallel to the optical axis, and the plurality of mirrors 122 may be arranged concentrically or radially in accordance with the arrangement of the plurality of parallel laser beams 13.

[0077] More specifically, in the example of Fig. 8, when viewed from a direction parallel to the optical axis, the multiple parallel laser beams 113 include a first parallel laser beam 113a located at the center, multiple second parallel laser beams 113b arranged concentrically around the first parallel laser beam 113a, and multiple third parallel laser beams 113c arranged concentrically around the multiple second parallel laser beams 113b. Also, in the example of Fig. 8, the multiple mirrors 122 include a first mirror 122a located at the center, multiple second mirrors 122b arranged concentrically around the first mirror 122a, and multiple third mirrors 122c arranged concentrically around the multiple second mirrors 122b, in accordance with the arrangement of the multiple parallel laser beams 113. The multiple second mirrors 122b are arranged at the same intervals, and the multiple third mirrors 122c are arranged at the same intervals. The first mirror 122a is formed, for example, in a circular shape. The second mirror 122b and the third mirror 122c can be formed, for example, in a shape like a partially cut-out circular ring.

[0078] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0079] (Technology 1) An optical modulation unit for controlling the beam profile of laser light, comprising: a branching section that branches laser light emitted from a laser oscillator into multiple parallel laser beams; and a phase difference generating section that generates a phase difference and reflects the multiple parallel laser beams, wherein the phase difference generating section has multiple first reflecting surfaces that reflect the multiple parallel laser beams, and multiple modulating sections that change the optical path lengths of the multiple parallel laser beams by changing the positions of the multiple first reflecting surfaces.

[0080] With this configuration, it is possible to provide a light modulation unit that can increase the output of laser light and dynamically change the beam profile.

[0081] (Technology 2) The optical modulation unit according to Technology 1, wherein the branching section has a diffractive optical element that branches the laser light emitted from the laser oscillator into multiple laser light beams, and a collimator lens that collimates the multiple branched laser light beams to generate multiple parallel laser light beams.

[0082] With this configuration, the laser light from the laser oscillator can be branched in a desired pattern.

[0083] (Technology 3) The light modulation unit according to Technology 1 or 2, wherein the plurality of first reflecting surfaces are configured by a plurality of mirrors.

[0084] With this configuration, a phase difference can be easily imparted to a plurality of parallel laser beams.

[0085] (Technology 4) The light modulation unit according to any one of Technologies 1 to 3, wherein the plurality of first reflecting surfaces are arranged in a grid pattern, a radial pattern, or a concentric pattern when viewed from a direction perpendicular to the first reflecting surfaces.

[0086] With this configuration, the plurality of first reflecting surfaces can be arranged in accordance with the branching pattern of the plurality of parallel laser beams.

[0087] (Technology 5) The light modulation unit according to Technology 4, wherein the plurality of first reflecting surfaces are arranged in a square lattice array when viewed from a direction perpendicular to the first reflecting surfaces.

[0088] With this configuration, the phase difference generating section can be made to have a simple configuration.

[0089] (Technology 6) The light modulation unit according to any one of Technologies 1 to 5, wherein a gap of 1 μm or more and 100 μm or less is formed between the adjacent first reflecting surfaces.

[0090] With this configuration, the gap is less likely to be irradiated with laser light, and damage to the optical modulation unit can be suppressed.

[0091] (Technology 7) The light modulation unit according to any one of Technologies 1 to 6, wherein the plurality of modulation sections are configured by a plurality of expansion and contraction sections that expand and contract in a direction intersecting the first reflecting surface.

[0092] With this configuration, the position of the first reflecting surface can be easily changed.

[0093] (Technology 8) The optical modulation unit according to any one of Technologies 1 to 7, wherein the plurality of modulation sections are configured by a plurality of piezoelectric elements, and the plurality of piezoelectric elements are bonded to opposite sides of the plurality of first reflecting surfaces, respectively.

[0094] With this configuration, the position of the first reflecting surface can be changed with high precision.

[0095] (Technology 9) The optical modulation unit according to any one of Technologies 1 to 8, further comprising a temperature maintaining base that maintains the temperatures of the plurality of modulation sections constant, the plurality of modulation sections being disposed on the temperature maintaining base.

[0096] With this configuration, the temperature of the modulation section can be kept constant, and therefore, changes in the position of the modulation section or the first reflecting surface due to a rise or fall in temperature can be suppressed.

[0097] (Technology 10) The optical modulation unit according to any one of Technologies 1 to 9, further comprising a folding optical element having a second reflecting surface that reflects the plurality of parallel laser beams from the branching section toward the phase difference generating section, and a third reflecting surface that reflects the plurality of parallel laser beams reflected by the phase difference generating section toward a focusing position.

[0098] With this configuration, the angle of reflection on the first reflecting surface of the phase difference generating section can be controlled, and therefore the phase differences of the plurality of parallel laser beams can be controlled more accurately.

[0099] (Technology 11) The optical modulation unit according to Technology 10, wherein the second reflecting surface is disposed at a position where the reflection angles of the plurality of parallel laser beams on each of the plurality of first reflecting surfaces are 30 degrees or less.

[0100] With this configuration, it is possible to prevent the generated phase difference from deviating from a desired value.

[0101] (Technology 12) A phase difference generating device that generates a phase difference and reflects a plurality of parallel laser beams, the phase difference generating device comprising: a plurality of reflecting surfaces that reflect the plurality of parallel laser beams; and a plurality of modulation units that change the optical path lengths of the plurality of parallel laser beams by changing the positions of the plurality of reflecting surfaces.

[0102] With this configuration, it is possible to provide a phase difference generating device that can dynamically change the beam profile using a high-power laser beam.

[0103] Next, second to fourth embodiments of the present disclosure will be described below.

[0104] Laser processing techniques, such as laser welding, are known in which a workpiece is irradiated with a laser beam to melt and vaporize it, thereby welding it to another workpiece. Laser processing techniques are widespread in the manufacturing of a wide range of products, including household appliances, precision instruments, and automobile parts.

[0105] In order to achieve stable laser processing, a technique for controlling the intensity distribution at the focal point of the laser beam is required. For example, Patent Document 2 discloses a method for selectively irradiating a plurality of regions of a ceramic material layer with laser beam using a digital micromirror device.

[0106] The method of Patent Document 2 still has room for improvement in terms of controlling the phase by increasing the output of the laser beam.

[0107] The present disclosure provides a phase modulation device capable of increasing the output of a laser beam and controlling the phase, a laser welding device including the phase modulation device, and a method for manufacturing the phase modulation device.

[0108] A phase modulation device according to one aspect of the present disclosure is a phase modulation device for controlling the phase of laser light, comprising: a plurality of intermediate plates having parallel main surfaces and arranged at equal intervals with a predetermined gap; a mirror arranged across the plurality of intermediate plates so as to cover the main surfaces of the plurality of intermediate plates; and a plurality of drive elements arranged on the opposite side of the main surfaces of each of the plurality of intermediate plates and moving the plurality of intermediate plates in a direction perpendicular to the main surfaces, wherein the mirror is deformable in accordance with the movement of the plurality of intermediate plates.

[0109] A laser welding apparatus according to one aspect of the present disclosure includes: a laser oscillator; the above-described phase modulation device that modulates the phase of laser light from the laser oscillator; and an optical system that suppresses stray light from the phase modulation device.

[0110] A method for manufacturing a phase modulation device according to one aspect of the present disclosure includes the steps of: fixing a plurality of drive elements to a base plate; arranging an intermediate substrate so as to cover the plurality of drive elements; arranging a mirror so as to cover the intermediate substrate; and irradiating a cutting laser having a wavelength that is transmitted through the mirror through the mirror to cut the intermediate substrate and form a plurality of intermediate plates.

[0111] According to the present disclosure, there are provided a phase modulation device capable of controlling the phase by increasing the output of a laser beam, a laser welding device including the phase modulation device, and a method for manufacturing the phase modulation device.

[0112] (Background to the present disclosure) When performing laser processing, it is necessary to control the beam profile of the laser light, which indicates the beam diameter, spatial intensity distribution, etc. For example, Patent Document 2 discloses a method in which a digital micromirror device (DMD) is used to selectively irradiate a laser beam onto multiple regions of a ceramic material layer.

[0113] However, the DMD is an assembly of minute mechanical structures, and there are gaps between the multiple micromirrors in the DMD. Therefore, when a high-power laser is used, the laser beam that passes through the gaps between the micromirrors or that is irradiated onto the side surfaces of the micromirrors is absorbed by the DMD, leading to damage or thermal distortion of the DMD itself. Therefore, if the laser beam is not accurately irradiated onto the desired area, there is a concern that the operating characteristics will deteriorate.

[0114] In recent years, the quality and stability of fiber lasers have improved, leading to their use in many processes, such as welding and cutting. As the performance of laser oscillators has also improved, fiber lasers have also become increasingly powerful. On the other hand, technologies that modulate the phase of laser light, such as the DMD or LCOS (Liquid Crystal on Silicon) mentioned above, are difficult to use with high-power lasers. For example, with LCOS, which uses liquid crystal for phase modulation, there is a concern that the operating characteristics may be degraded due to damage or thermal distortion of the liquid crystal itself. Therefore, there is a problem in that it is difficult to appropriately control the beam profile of laser light when processing using high-power lasers.

[0115] The present inventor(s) have studied a phase modulation device capable of modulating the phase of a high-power laser including a fiber laser to control the beam profile, a laser welding device equipped with a phase modulation device, and a method for manufacturing a phase modulation device, and have arrived at the following invention.

[0116] (Embodiment 2) [Overall Configuration] Fig. 9 is a plan view schematically showing a phase modulation device 220 according to embodiment 2. Fig. 10 is a cross-sectional view of the phase modulation device 220 of Fig. 9. Note that the X-Y-Z Cartesian coordinate system shown in the figure is intended to facilitate understanding of the present disclosure and does not limit the embodiments of the present disclosure. The X-axis direction indicates the width direction of the phase modulation device 220, the Y-axis direction indicates the depth direction of the phase modulation device 220, and the Z-axis direction indicates the height direction of the phase modulation device 220.

[0117] The phase modulation device 220 is a device for modulating the phase of laser light. As shown in Figures 9 and 10, the phase modulation device 220 includes a plurality of intermediate plates 203, a mirror 204, and a plurality of driving elements 202. The phase modulation device 220 modulates the phase of the laser light emitted from a laser oscillator while reflecting the laser light by the mirror 204. The laser oscillator that can be used is one that emits laser light with a wavelength λ = 1.070 µm, for example.

[0118] As shown in Figures 9 and 10, in this embodiment, the phase modulation device 220 has 16 drive elements 202 and 16 intermediate plates 203, and the drive elements 202 and the intermediate plates 203 correspond one-to-one.

[0119] 10 , in this embodiment, the phase modulation device 220 includes a base plate 201, and driving elements 202 are aligned and arranged on a main surface 201a of the base plate 201. Note that the base plate 201 is not an essential component of the phase modulation device 220. The base plate 201 is a plate-shaped member for fixing the components of the phase modulation device 220 on the same plane. It is desirable that the base plate 201 be made of a material with high rigidity and a small thermal expansion coefficient.

[0120] The driving element 202 is fixed to the main surface 201a of the base plate 201. Driving the driving element 202 in the Z direction moves the intermediate plate 203 in a direction perpendicular to a main surface 231 of the intermediate plate 203 (described later). The driving element 202 vibrates in the Z direction at a frequency of, for example, 0.1 Hz or higher. The driving element 202 is preferably driven at a frequency of 1 kHz or higher. More preferably, the driving element 202 is driven at a frequency of 20 kHz or higher. A driving frequency of 20 kHz or higher allows the laser light to be scanned while rapidly changing the reflection position at which the light is reflected in the phase modulation device 220. The displacement of the driving element 202 in the Z direction may be, for example, ½ or more of the wavelength of the laser light reflected by the mirror 204. The driving element 202 may be configured, for example, by a piezoelectric element. A piezoelectric element is a driving element that vibrates in the Z direction using a piezoelectric method.

[0121] The intermediate plate 203 is a plate-shaped member for fixing the mirror 204. In this embodiment, as shown in FIG. 9 , the intermediate plate 203 has a square shape in a plan view. The intermediate plates 203 are equally spaced apart at a predetermined interval sp1. In this embodiment, 16 intermediate plates 203 are arranged in a 4×4 grid. Each of the intermediate plates 203 has a main surface 231 that is parallel to one another. The intermediate plate 203 is preferably made of a material that is unlikely to bend due to vibration of the drive element 202. As a material for the intermediate plate 203, a highly rigid material such as silicon, glass containing synthetic quartz, sapphire, SiC (silicon carbide), ceramics, and metal can be used.

[0122] The mirror 204 is disposed across multiple intermediate plates 203 so as to cover the main surfaces 231 of the multiple intermediate plates 203. As shown in FIG. 9 , the mirror 204 is disposed so as to cover the main surfaces 231 of all 16 intermediate plates 203. The mirror 204 is formed to a thickness equal to or less than one-tenth of the predetermined spacing sp1. By setting the thickness of the mirror 204 equal to or less than one-tenth of the predetermined spacing sp1, the mirror 204 can deform in response to movement of the intermediate plates 203 in the Z direction. To achieve higher reliability, the thickness of the mirror 204 should be equal to or less than one-hundredth of the predetermined spacing. In this embodiment, the thickness of the mirror 204 is equal to or less than 10 μm. By setting the thickness of the mirror 204 to equal to or less than 10 μm, the mirror 204 can deform in response to movement of the intermediate plates 203. The thickness of the mirror 204 may be selected depending on the drive frequency of the drive element 202. The thickness of the mirror 204 includes the thickness of the substrate and the thickness of the reflective coating, which will be described later.

[0123] The mirror 204 can be formed by applying a reflective coating to the surface of a substrate having a thickness of 10 μm or less. Examples of materials that can be used for the substrate of the mirror 204 include silicon, glass containing synthetic quartz, sapphire, SiC, GaN (gallium nitride), ZnSe (zinc selenide), and Ge (germanium). The reflective coating applied to the surface of the substrate is preferably a coating that reflects 90% or more of the light having the wavelength of the laser beam emitted from the laser oscillator and transmits 10% or more of light other than the wavelength of the laser beam.

[0124] The mirror 204 is deformable in response to movement of the plurality of intermediate plates 203. The deformation of the mirror 204 will be described with reference to FIG. 11 . FIG. 11 is a cross-sectional view showing a state in which the intermediate plate 203 is displaced by driving the driving elements 202 of the phase modulation device 220 of FIG. 10 . For ease of explanation, in FIG. 11 , the four illustrated driving elements 202 are referred to as driving elements 202a, 202b, 202c, and 202d, respectively, and the four illustrated intermediate plates 203 are referred to as intermediate plates 203a, 203b, 203c, and 203d, respectively.

[0125] 11 shows that two of the four drive elements 202a to 202d, 202b and 202c, are displaced in the -Z direction, and that the main surfaces 231b and 231c of two of the four intermediate plates 203a to 203d, 203b and 203c, are displaced in the -Z direction by a distance h1. At this time, in the mirror 204, a portion 241 between the adjacent intermediate plates 203a and 203b and a portion 242 between the adjacent intermediate plates 203c and 203d are deformed. When the drive elements 202 and the intermediate plate 203 are in the state shown in FIG. 10, the mirror 204 has a flat shape. However, as shown in FIG. 11, when the intermediate plates 203b and 203c move, portions of the mirror 204 (portions 241 and 242) are deformed. Due to the deformation of a portion of the mirror 204, the reflecting surface of the mirror 204 is displaced in accordance with the movement of the main surface 231 of the intermediate plate 203. As described above, the main surfaces 231b and 231c of the intermediate plates 203b and 203c are displaced by a distance h1 in the −Z direction. At this time, the reflecting surface 244 of the mirror 204 located in the portion overlapping the intermediate plates 203b and 203c when viewed from the Z direction is also displaced by a distance h1 in the −Z direction in accordance with the displacement of the main surfaces 231b and 231c of the intermediate plates 203b and 203c. Therefore, as shown in the cross-sectional view of FIG. 11 , when the intermediate plates 203b and 203c move in the −Z direction, the portions of the mirror 204 located in the gap between the intermediate plates 203a and 203b and the gap between the intermediate plates 203c and 203d are deformed, and the mirror 204 as a whole assumes a partially recessed shape. In this way, by moving any one of the intermediate plates 203 in the Z direction, the position of the mirror 204 in the Z direction can be displaced.

[0126] Next, phase modulation by the phase modulation device 220 will be described with reference to Fig. 12 and Fig. 13. Fig. 12 is a schematic diagram showing a state in which the laser light L1 is reflected by the phase modulation device 220 of Fig. 10. Fig. 13 is a schematic diagram showing a state in which the laser light L1 is reflected by the phase modulation device 220 of Fig. 11.

[0127] 12 shows a case where the main surfaces 231a to 231d of the respective intermediate plates 203a to 203d are at the same position in the Z direction. That is, in FIG. 12, the main surfaces 231a to 231d of the intermediate plates 203a to 203d are on the same plane. When the laser light L1 enters the phase modulation device 220, the laser light L1 is reflected by the reflecting surface 243 of the mirror 204. At this time, since the phases of the laser light L1 are equal, the wavefront A1 is flat, and the wavefront B1 of the laser light R1 reflected by the reflecting surface 243 is also flat.

[0128] 13 shows a case where the driving elements 202b and 202c are driven to move the intermediate plates 203b and 203c in the -Z direction. In FIG. 13, a portion (reflecting surface 244) of the reflecting surface 243 of the mirror 204 located at the portion overlapping with the intermediate plates 203b and 203c when viewed from the Z direction is displaced in the -Z direction. When the laser light L1 enters the phase modulation device 220, the laser light L1 is reflected by the reflecting surfaces 243 and 244 of the mirror 204. A difference occurs in the optical path length of the laser light L1 from when it enters the phase modulation device 220 until it exits, between the portion of the laser light reflected by the reflecting surface 244 displaced in the -Z direction and the portion reflected by the reflecting surface 243 that is not displaced. Therefore, while the wavefront A1 of the laser light L1 incident on the phase modulation device 220 is flat, the wavefront B2 of the reflected laser light R2 is not flat but concave, resulting in a phase difference. Specifically, if the refractive index of the medium through which the laser light L1 propagates is n, the amount of displacement of the reflecting surface 243 due to the displacement of the intermediate plate is C, and the angle of incidence of the laser light L1 is θ, the optical path length difference L can be expressed by the formula L = (C / tan θ) × n × 2. The optical path length difference L represents the phase difference in the laser light R1.

[0129] For example, if the medium through which the laser light propagates is air with a refractive index n = 1.0 and the wavelength λ of the laser light L1 is 1.070 μm, then in order to generate an optical path length difference of 2π, i.e., a phase difference of 2π, the displacement amount C can be determined to satisfy the formula L = λ = 1.070 μm = (C / tan θ) × 1.0 × 2.

[0130] Since each of the multiple intermediate plates 203 can be moved individually, the phase of the laser light L1 can be modulated by using the intermediate plate 203 as one pixel. In this embodiment, the phase of the laser light L1 can be modulated within a range of 4 × 4 pixels.

[0131] Since the mirror 204 is disposed across the multiple intermediate plates 203, when the laser light L1 enters the phase modulation device 220, it is possible to prevent the laser light L1 from being irradiated onto the gaps in the intermediate plates 203. Therefore, in the phase modulation device 220, it is possible to reduce damage to the phase modulation device caused by a high-power laser or deterioration of operating characteristics caused by thermal distortion.

[0132] [Manufacturing Method] A method for manufacturing the phase modulation device 220 will be described with reference to Fig. 14 to Fig. 24. Fig. 14 is a flowchart for explaining the method for manufacturing the phase modulation device 220. Fig. 15 to Fig. 24 are plan views or cross-sectional views that schematically show the manufacturing process of the phase modulation device 220.

[0133] In step S201, as shown in Figures 15 and 16, a plurality of drive elements 202 are fixed to the base plate 201. In this embodiment, as shown in Figure 15, 16 drive elements 202 are arranged in a 4x4 grid and fixed to the base plate 201. The drive elements 202 can be fixed to the base plate 201 by, for example, room temperature bonding. In this case, since no material such as an adhesive is interposed between the base plate 201 and each drive element 202, variation in the up and down vibration of the drive elements 202 can be suppressed. Alternatively, an adhesive or the like may be used to fix the drive elements 202 to the base plate 201.

[0134] Next, in step S202, as shown in FIGS. 17 and 18 , an intermediate substrate 213 is arranged so as to cover the plurality of drive elements 202. The intermediate substrate 213 is a member that is cut to a predetermined size to form the intermediate plate 203. Therefore, the intermediate substrate 213 is made of the same material as the intermediate plate 203. The intermediate substrate 213 is a plate that is sized and shaped to cover all of the plurality of drive elements 202 in a plan view. As will be described later, the intermediate substrate 213 is cut to form the plurality of intermediate plates 203 of predetermined sizes. Grooves 212 are formed in the intermediate substrate 213 in advance. The grooves 212 serve as guides for irradiating a cutting laser 214 (see FIG. 22 ) when cutting the intermediate substrate 213 later. The intermediate substrate 213 may be prepared with the grooves 212 formed in advance, or the grooves 212 may be formed after the intermediate substrate 213 is placed on the drive elements 202. The grooves 212 can be formed in the intermediate substrate 213 by, for example, processing with a laser beam, or processing with a grindstone or a cutting machine, etc. The intermediate substrate 213 can be fixed to the plurality of drive elements 202 using an adhesive or the like.

[0135] Next, in step S203, as shown in Figures 19 and 20, the mirror 204 is arranged so as to cover the intermediate substrate 213. As shown in Figure 20, the intermediate substrate 213 is a single plate, and therefore the surface 213a of the intermediate substrate 213 is a flat surface. Therefore, by arranging the mirror 204 on the intermediate substrate 213, the flatness of the mirror 204 can be ensured. The mirror 204 can be fixed to the intermediate substrate 213 using an adhesive or the like.

[0136] Next, in step S204, as shown in FIGS. 21 and 22, a cutting laser 214 is incident from the mirror 204 to cut the intermediate substrate 213 to form a plurality of intermediate plates 203. A pulsed laser or a continuous wave laser may be used as the cutting laser 214. The cutting laser 214 has a wavelength that is transmitted through the mirror 204. Therefore, the cutting laser 214 passes through the mirror 204 without being focused, and is focused by the grooves 212 in the intermediate substrate 213, thereby cutting the intermediate substrate 213. The cutting laser 214 preferably has a wavelength that is transmitted through the mirror 204 by 10% or more so that the cutting laser 214 is not focused on the substrate of the mirror 204. Furthermore, the cutting laser 214 preferably has a wavelength that is absorbed by the intermediate substrate 213 by at least 20%. A cutting laser 214 having a wavelength that is absorbed by the intermediate substrate 213 by 20% or more can improve the cutting efficiency of the intermediate substrate 213. The preferred wavelength of the cutting laser 214 varies depending on the material of the intermediate substrate 213. For example, if the material of the intermediate substrate 213 is silicon, the wavelength of the cutting laser 214 is preferably 1 μm or longer. If the material of the intermediate substrate 213 is glass, sapphire, or SiC, the wavelength of the cutting laser 214 is preferably 0.3 μm or longer. If the material of the intermediate substrate 213 is GaN or ZnSe, the wavelength of the cutting laser 214 is preferably 0.4 μm or longer. If the material of the intermediate substrate 213 is Ge, the wavelength of the cutting laser 214 is preferably 2 μm or longer. By repeatedly scanning the cutting laser 214 along the groove 212, the intermediate substrate 213 can be cut to form the intermediate plate 203.

[0137] When the intermediate substrate 213 is cut to form the intermediate plates 203, the phase modulation device 220 is completed as shown in Figures 23 and 24. Note that, when the intermediate substrate 213 is cut, deposits may be formed on the portions of the mirror 204 that cover the gaps 232 between the adjacent intermediate plates 203 due to melting or evaporation of the material of the intermediate substrate 213.

[0138] [Effects] According to the above-described embodiment, the following effects can be achieved.

[0139] The phase modulation device 220 is a device for controlling the phase of laser light, and includes a plurality of intermediate plates 203, a mirror 204, and a plurality of drive elements 202. The plurality of intermediate plates 203 have main surfaces 231 parallel to one another and are arranged at equal intervals at a predetermined interval sp1. The mirror 204 is arranged across the plurality of intermediate plates 203 so as to cover the main surfaces 231 of the plurality of intermediate plates 203. The plurality of drive elements 202 are arranged on the opposite side of the main surfaces 231 of the plurality of intermediate plates 203, and move the plurality of intermediate plates 203 in a direction perpendicular to the main surfaces 231. The mirror 204 is deformable in accordance with the movement of the plurality of intermediate plates 203.

[0140] With this configuration, it is possible to provide a phase modulation device that can control the phase by increasing the output of a laser beam.

[0141] The mirror 204 is deformable in the portions between adjacent intermediate plates.

[0142] With this configuration, the beam shape of the laser light L1 can be controlled with higher precision.

[0143] The mirror 204 is composed of a substrate containing at least one of silicon, glass including synthetic quartz, sapphire, SiC, GaN, ZnSe, and Ge, and a reflective coating applied to the surface of the substrate.

[0144] With this configuration, the mirror 204 can be deformed with high precision in accordance with the movement of the plurality of intermediate plates 203 .

[0145] The reflective coating reflects 90% or more of the light with the wavelength of the laser light L1, and transmits 10% or more of the light with wavelengths other than the laser light L1.

[0146] With this configuration, the mirror 204 can efficiently reflect light other than the laser light L1.

[0147] The thickness of the mirror 204 is equal to or less than one tenth of the predetermined spacing sp1.

[0148] With this configuration, high reliability of the phase modulation device 220 can be ensured.

[0149] The plurality of driving elements 202 move the plurality of intermediate plates 203 by a piezoelectric method.

[0150] With this configuration, the plurality of intermediate plates 203 can be moved by a desired amount of displacement.

[0151] The manufacturing method of the phase modulation device 220 includes the steps of fixing a plurality of driving elements 202 to a base plate 201, arranging an intermediate substrate 213 so as to cover the plurality of driving elements 202, arranging a mirror 204 so as to cover the intermediate substrate 213, and irradiating a cutting laser 214 having a wavelength that is transmitted through the mirror 204 from the mirror 204 to cut the intermediate substrate 213 and form a plurality of intermediate plates 203.

[0152] With this configuration, it is possible to provide a method for manufacturing a phase modulation device that can control the phase by increasing the output of a laser beam.

[0153] In the above-described embodiment, the laser beam L1 emitted from the laser oscillator has a wavelength λ of 1.070 μm, but is not limited to this. The laser beam L1 may have any wavelength that can be used for laser processing, and the wavelength λ may be, for example, 0.1 μm or more and 11 μm or less.

[0154] Furthermore, in the above-described embodiment, an example has been described in which the reflective coating of the mirror 204 reflects 90% or more of the light of the wavelength of the laser light L1, but this is not limiting. The reflective coating of the mirror 204 can be changed depending on the output of the laser light L1 to be reflected. For example, when the power of the laser light L1 is low, even a coating with a reflectivity of about 50% can be sufficient to function as the phase modulation device 220. On the other hand, when a high-output laser light L1 is used, it is preferable to use a coating with a high reflectivity.

[0155] In the above-described embodiment, the plurality of driving elements 202 move the plurality of intermediate plates 203 by a piezoelectric method, but the present invention is not limited to this. The plurality of driving elements 202 may move the plurality of intermediate plates 203 by, for example, an electrostatic method or an electromagnetic method.

[0156] In the above-described embodiment, the plurality of drive elements 202 and the plurality of intermediate plates 203 include 16 drive elements 202 and 16 intermediate plates 203 arranged in a 4×4 grid pattern. However, this is not limiting. Any number of drive elements 202 and intermediate plates 203 may be selected. Since a larger number of pixels is preferable for more accurate control of the beam profile of the laser light, it is preferable that the phase modulation device 220 has a larger number of drive elements 202 and intermediate plates 203. For example, the number of pixels may be 64×64 or more, or 1024×1024 or more, and therefore the plurality of drive elements 202 and the plurality of intermediate plates 203 may be arranged in a 64×64 or 1024×1024 pattern.

[0157] 25 is a flowchart for explaining a manufacturing method of a phase modulation device 220 according to Modification 1 of Embodiment 2. As shown in Fig. 25 , after fixing the plurality of drive elements 202 to the base plate 201 in step S211, a step of aligning the heights of the plurality of drive elements 202 from the base plate 201 may be executed in step S212. By aligning the heights of the plurality of drive elements 202, it is possible to align the positions in the Z direction of the main surfaces of the plurality of intermediate plates 203 when the phase modulation device 220 is completed.

[0158] 26 and 27, a third embodiment will be described. In the third embodiment, the same or equivalent components as those in the second embodiment will be denoted by the same reference numerals. In the third embodiment, descriptions that overlap with those in the second embodiment will be omitted.

[0159] Fig. 26 is a diagram schematically showing a laser welding apparatus 200 according to a third embodiment. Fig. 27 is a diagram for explaining generation of stray light in a phase modulation device 220. As shown in Fig. 26, in this embodiment, a laser welding apparatus 200 including a phase modulation device 220 will be described. The configuration of the phase modulation device 220 is the same as that of the second embodiment, and therefore description thereof will be omitted.

[0160] The laser welding apparatus 200 includes a laser oscillator 250, a phase modulator 220, and an optical system 260. The laser welding apparatus 200 controls the beam profile of laser light L1 emitted from the laser oscillator 250 using the phase modulator 220, suppresses stray light using the optical system 260, and irradiates the workpiece with the laser light to perform laser welding of the workpiece.

[0161] The laser oscillator 250 is an oscillator that emits laser light with a wavelength λ=1.070 μm, for example. Laser light L1 from the laser oscillator 250 is incident on the phase modulation device 220. As described in the second embodiment, laser light R2 is reflected by the mirror 204 and has its phase modulated, and is then emitted from the phase modulation device 220. The laser light reflected by the phase modulation device 220 contains stray light R3 and R4.

[0162] Here, the occurrence of stray light will be described with reference to Figure 27. Laser light L1 from laser oscillator 250 is incident on phase modulator 220 and reflected by reflecting surface 243 of mirror 204. At this time, as shown in Figure 27, intermediate plates 203b and 203c are moved by drive elements 202b and 202c, and a part of reflecting surface 243, i.e., the part of reflecting surface 244 that overlaps with intermediate plates 203b and 203c when viewed from the Z direction, is displaced in the -Z direction relative to the undisplaced reflecting surface 243. At this time, portions 241 and 242 connecting reflecting surface 244 displaced in the -Z direction and the undisplaced reflecting surface 243 are deformed, and therefore become surfaces inclined with respect to main surface 231 of intermediate plate 203. Because the portions 241 and 242 are inclined with respect to the main surface 231 of the intermediate plate 203, the laser beams R3 and R4 reflected by the portions 241 and 242 exit the phase modulation device 220 at an angle different from that of the laser beam R1 reflected by the reflecting surfaces 243 and 244, and become stray light. The stray light beams R3 and R4 are light beams whose phases cannot be controlled by the phase modulation device 220.

[0163] In this embodiment, an optical system 260 is provided to suppress stray light whose phase cannot be controlled. The optical system 260 includes, for example, a first lens 207, a second lens 209, a condenser lens 210, and a filter 208. As shown in Fig. 26 , the first lens 207, the second lens 209, the condenser lens 210, and the filter 208 are disposed on the optical axis G of the laser light R2 reflected by the phase modulation device 220. Furthermore, a workpiece 211 is also disposed on the optical axis G.

[0164] The laser light R2 reflected by the phase modulation device 220 is focused by the first lens 207 onto a pinhole P provided in the filter 208. At this time, stray light R3 and R4 pass through the first lens 207 but are not focused onto the pinhole P, but are blocked by the outer periphery of the pinhole P in the filter 208. The laser light R2 focused onto the pinhole P is collimated by the second lens 209. The laser light R2 collimated by the second lens is focused onto the workpiece 211 by the condenser lens 210. The stray light R3 and R4 generated by the phase modulation device 220 cannot pass through the pinhole P and do not reach the workpiece 211. Therefore, by providing the optical system 260, it is possible to suppress stray light and reduce its impact on the processing of the workpiece 211. The filter 208 can be made of, for example, metal. In order to prevent overheating when stray light is irradiated onto the filter 208, a coating capable of reflecting the laser light R2 may be applied around the pinhole P of the filter 208, or a cooling section may be provided to water-cool the filter 208.

[0165] For example, when the diameter of laser light R2 is 20 mm and the wavelength of laser light R2 is 1.070 μm, lenses having a focal length of 250 mm, a diameter of 50 mm, and transmitting 90% or more of the wavelength of laser light R2 can be used as lenses 207, 209, and 210 of optical system 260. That is, first lens 207 has a focal length f1 = 250 mm and a diameter D7 = 50 mm, second lens 209 has a focal length f2 = 250 mm and a diameter D9 = 50 mm, and condenser lens 210 has a focal length f3 = 250 mm and a diameter D10 = 50 mm.

[0166] When a single-mode fiber laser is focused using an optical system with an optical magnification of 3, if the single-mode fiber core diameter is about 10 μm, the focused beam diameter S at the focusing position by the first lens 207 will be about 30 μm. Considering the spread of the laser beam to its base, it is preferable that the pinhole P of the filter 208 has a diameter DP of about 50 μm.

[0167] [Effects] According to the above-described embodiment, the following effects can be achieved.

[0168] The laser welding device 200 includes a laser oscillator 50 , a phase modulation device 220 , and an optical system 260 for suppressing stray light from the phase modulation device 220 .

[0169] With this configuration, the influence of stray light generated by the phase modulation device 220 during laser welding can be reduced.

[0170] In the above-described embodiment, the focal length f1 of the first lens 207 and the focal length f2 of the second lens 209 are equal to each other, but the present invention is not limited to this. The focal length f1 of the first lens 207 and the focal length f2 of the second lens 209 may be different from each other.

[0171] 26 , the diameter of the laser light R2 reflected by the phase modulation device 220 when passing through the first lens 207 is D5, and the diameter when passing through the second lens 209 is D6. In this case, if the focal length f1 of the first lens 207 and the focal length f2 of the second lens 209 are equal, D5=D6 holds in the optical system 260. On the other hand, if the focal length f1 of the first lens 207 and the focal length f2 of the second lens 209 are different, D5×(f2 / f1)=D6 holds in the optical system 260. In this case, if f1<f2, D5<D6 holds, and the optical system 260 becomes a magnifying optical system. If f1>f2, D5>D6 holds, and the optical system 260 becomes a reducing optical system.

[0172] Furthermore, in the above-described embodiment, an example has been described in which the focal length f1 of the first lens 207 is equal to the distance S1 between the first lens 207 and the filter 208, the focal length f2 of the second lens 209 is equal to the distance S2 between the filter 208 and the second lens 209, and the focal length f3 of the condenser lens 210 is equal to the distance S3 between the condenser lens 210 and the workpiece 211, but this is not limiting. For example, by adjusting the distances S1 to S3, it is possible to adjust the convergence angle of the laser light R2 transmitted through the first lens 207 or the divergence angle of the laser light R2 passed through the pinhole P. Adjusting the convergence angle or divergence angle also makes it possible to control the diameter DP of the pinhole P or the transmittance of the pinhole P.

[0173] 28 to 31, a fourth embodiment will be described. In the fourth embodiment, the same or equivalent components as those in the second embodiment will be denoted by the same reference numerals. In the fourth embodiment, descriptions that overlap with those in the second embodiment will be omitted.

[0174] Fig. 28 is a block diagram showing a schematic configuration of a phase modulation device 220A according to a fourth embodiment. Figs. 29 to 31 are schematic diagrams showing examples of segments in the phase modulation device 220A of Fig. 28. As shown in Fig. 28, the fourth embodiment differs from the second embodiment in that the phase modulation device 220A includes a control unit 270. The fourth embodiment also differs from the second embodiment in that the multiple intermediate plates are configured by multiple segments each made up of a predetermined number of adjacent intermediate plates 203.

[0175] The control unit 270 can individually control each of the multiple drive elements 202. The control unit 270 includes, for example, a memory that stores a program and a processing circuit corresponding to a processor such as a CPU (Central Processing Unit). The functions of the control unit 270 may be configured solely by hardware, or may be realized by combining hardware and software. The control unit 270 realizes predetermined functions by reading data and programs stored in the memory and performing various arithmetic processing.

[0176] 29, the plurality of intermediate plates 203 are configured by 16 segments 205a each configured by one intermediate plate 203. In this case, each segment 205a corresponds to one pixel.

[0177] In the example of FIG. 30 , four intermediate plates 203 arranged in a 2×2 pattern constitute one segment 205b. Therefore, in the example of FIG. 30 , the multiple intermediate plates 203 are configured from four segments 205b. In this case, the control unit 270 controls the drive elements 202 so that the intermediate plates 203 included in one segment 205b move synchronously. That is, the control unit 270 controls the drive elements 202 included in one segment 205b so that the main surfaces of the intermediate plates 203 included in that segment 205b are positioned on the same plane. For example, of the four segments 205b shown in FIG. 30 , the control unit 270 controls the drive elements 202 included in the upper left segment 205b so that the main surfaces of the four intermediate plates 203 included in the upper left segment 205b are positioned on the same plane. Similarly, the control unit 270 controls the multiple drive elements 202 so that the main surfaces of the four intermediate plates 203 included in the other three segments 205b are also positioned on the same plane. In the case of FIG. 30, each of the four segments 205b corresponds to one pixel.

[0178] In the example of Fig. 31, two intermediate plates 203 arranged in the X direction constitute one segment 205c. Therefore, in the example of Fig. 31, the multiple intermediate plates 203 are constituted by eight segments 205c. In this case, as in the example of Fig. 30, the control unit 270 controls the multiple drive elements 202 so that the main surfaces of the intermediate plates 203 included in one segment 205c are positioned on the same plane. In the case of Fig. 31, each of the eight segments 205c constitutes one pixel.

[0179] 29 to 31, in the phase modulation device 220A, the control unit 270 can change the number of intermediate plates 203 included in a segment. By changing the number of intermediate plates 203 included in a segment, the size and shape of each pixel can be changed.

[0180] The phase modulation device 220A allows for the design of an appropriate CGH (Computer-Generated Hologram). The phase modulation device 220A performs phase modulation for each segment based on the CGH, causing the laser light reflected by each segment to interfere, thereby controlling the branching or shape of the laser light. The center-to-center distance between the above-mentioned multiple segments 205a-205c corresponds to the pixel pitch of the CGH. In the CGH, the smaller the pixel pitch, the larger the diffraction angle, and vice versa, depending on the desired pattern, such as the beam shape of the laser light. Changing the number of intermediate plates 203 included in the segments can reduce constraints on the CGH design.

[0181] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0182] (Technology 1) A phase modulation device for controlling the phase of laser light, comprising: a plurality of intermediate plates having parallel main surfaces and arranged at equal intervals with a predetermined gap between them; a mirror arranged across the plurality of intermediate plates so as to cover the main surfaces of the plurality of intermediate plates; and a plurality of drive elements arranged on the opposite side of each of the main surfaces of the plurality of intermediate plates and moving the plurality of intermediate plates in a direction perpendicular to the main surfaces, wherein the mirror is deformable in accordance with the movement of the plurality of intermediate plates.

[0183] With this configuration, it is possible to provide a phase modulation device that can control the phase by increasing the output of a laser beam.

[0184] (Technology 2) The phase modulation device according to Technology 1, wherein the mirror is deformable in the portions between the adjacent intermediate plates.

[0185] With this configuration, the beam shape of the laser light can be controlled with higher precision.

[0186] (Technology 3) The phase modulation device of Technology 1 or 2 further includes a control unit that controls the plurality of drive elements, wherein the plurality of intermediate plates are configured by a plurality of segments each made up of a predetermined number of adjacent intermediate plates, and the control unit controls the drive elements so that the predetermined number of intermediate plates included in each of the plurality of segments move synchronously.

[0187] This configuration makes it possible to branch the laser light and shape it into various shapes.

[0188] (Technology 4) The phase modulation device according to Technology 3, wherein the control unit controls the plurality of drive elements so that the respective main surfaces of a predetermined number of intermediate plates included in each of the plurality of segments are positioned on the same plane.

[0189] This configuration makes it possible to branch the laser light and shape it into various shapes.

[0190] (Technology 5) The phase modulation device according to any one of technologies 1 to 4, wherein the mirror is composed of a substrate including at least one of silicon, glass including synthetic quartz, sapphire, SiC, GaN, ZnSe, or Ge, and a reflective coating applied to the surface of the substrate.

[0191] With this configuration, the mirror can be deformed with high precision in accordance with the movement of the plurality of intermediate plates.

[0192] (Technology 6) A phase modulation device according to Technology 5, wherein the reflective coating reflects 90% or more of light having the wavelength of the laser light and transmits 10% or more of light having wavelengths other than the laser light.

[0193] With this configuration, the mirror can efficiently reflect light other than the laser beam.

[0194] (Technology 7) The phase modulation device according to any one of technologies 1 to 6, wherein the thickness of the mirror is one-tenth or less of the predetermined interval.

[0195] With this configuration, high reliability of the phase modulation device can be ensured.

[0196] (Technology 8) The phase modulation device according to any one of technologies 1 to 7, wherein the plurality of drive elements move the plurality of intermediate plates by a piezoelectric method, an electrostatic method, or an electromagnetic method.

[0197] With this configuration, the plurality of intermediate plates can be moved by a desired amount of displacement.

[0198] (Technology 9) A laser welding device comprising: a laser oscillator; a phase modulation device according to any one of technologies 1 to 8 that modulates the phase of laser light from the laser oscillator; and an optical system that suppresses stray light from the phase modulation device.

[0199] With this configuration, the influence of stray light generated in the phase modulation device during laser welding can be reduced.

[0200] (Technology 10) A method for manufacturing a phase modulation device, comprising the steps of fixing a plurality of drive elements to a base plate, arranging an intermediate substrate so as to cover the plurality of drive elements, arranging a mirror so as to cover the intermediate substrate, and irradiating a cutting laser having a wavelength that is transmitted through the mirror from the mirror to cut the intermediate substrate and form a plurality of intermediate plates.

[0201] With this configuration, it is possible to provide a method for manufacturing a phase modulation device that can control the phase by increasing the output of a laser beam.

[0202] (Technology 11) The method for manufacturing a phase modulation device according to Technology 10, further comprising the step of adjusting the height of the plurality of drive elements from the base plate before the step of arranging an intermediate substrate so as to cover the plurality of drive elements.

[0203] With this configuration, the positions of the main surfaces of the plurality of intermediate plates can be aligned when the phase modulation device is completed.

[0204] (Technology 12) The method for manufacturing a phase modulation device according to Technology 10 or 11, wherein the intermediate substrate is provided with a groove serving as a guide for irradiating a cutting laser.

[0205] With this configuration, the intermediate substrate can be cut with high precision.

[0206] (Technology 13) The method for manufacturing a phase modulation device according to any one of Technologies 10 to 12, wherein the cutting laser has a wavelength that is transmitted by the mirror at a rate of 10% or more and absorbed by the intermediate substrate at a rate of 20% or more.

[0207] With this configuration, the intermediate substrate can be cut efficiently.

[0208] (Technology 14) The method for manufacturing a phase modulation device according to any one of Technologies 10 to 13, wherein the wavelength of the cutting laser is 0.3 μm or more.

[0209] This configuration allows cutting of intermediate substrates of various materials.

[0210] The present disclosure provides a light modulation unit and a phase difference generating device that can be applied to a laser processing device such as laser welding or laser cutting.

[0211] REFERENCE SIGNS LIST 1 laser oscillator 10 branching section 11 diffractive optical element 12 collimator lens 13, 113 parallel laser light 15 folding optical element 16 mirror (second reflecting surface) 17 mirror (third reflecting surface) 20 phase difference generating section (phase difference generating device) 22, 122 first reflecting surface 22 mirror (first reflecting surface) 23 piezoelectric element (modulation section) 24 temperature maintaining base 31 condenser lens 32 condenser point 33 workpiece 40 drive signal generating device 100 light modulation unit 201 base plate 202, 202a to 202d drive element 203, 203a to 203d intermediate plate 204 mirror 205a segment 205b segment 205c segment 207 first lens 208 filter 209 Second lens 210 Condenser lens 211 Workpiece 212 Groove 213 Intermediate substrate 214 Cutting laser 220, 220A Phase modulation device 231, 231a to 231d Main surface 232 Gap 243 Reflecting surface 244 Reflecting surface 250 Laser oscillator 260 Optical system 270 Control unit 200 Laser welding device

Claims

1. A phase modulation device for controlling the phase of laser light, comprising: at least one mirror including a reflecting surface; and a plurality of drive elements arranged on the opposite side of the at least one mirror from the reflecting surface, wherein the reflecting surface is displaced by the plurality of drive elements.

2. The phase modulation device according to claim 1, wherein the at least one mirror includes a plurality of mirrors, and each of the plurality of mirrors is provided for each of the plurality of drive elements.

3. The phase modulation device according to claim 2, wherein the plurality of mirrors are arranged in a grid pattern, a radial pattern, or a concentric pattern when viewed from a direction perpendicular to the reflecting surface.

4. A phase modulation device according to claim 2, wherein a gap of 1 μm or more and 100 μm or less is formed between adjacent ones of the plurality of mirrors.

5. An optical modulation unit comprising: a branching section that branches laser light emitted from a laser oscillator into a plurality of parallel laser beams; and a phase modulation device according to any one of claims 1 to 4, wherein the phase modulation device changes the optical path lengths of the plurality of parallel laser beams.

6. The optical modulation unit according to claim 5, wherein the branching section comprises a diffractive optical element that branches the laser light emitted from the laser oscillator into a plurality of laser light beams, and a collimator lens that collimates the plurality of branched laser light beams to generate the plurality of parallel laser light beams.

7. A phase modulation device as described in claim 1, further comprising a plurality of intermediate plates having parallel main surfaces and arranged at equal intervals with a predetermined gap between them, wherein the at least one mirror is arranged across the plurality of intermediate plates so as to cover the main surfaces of the plurality of intermediate plates, the plurality of drive elements are arranged on the opposite side of the main surfaces of each of the plurality of intermediate plates and move the plurality of intermediate plates in a direction perpendicular to the main surfaces, and the at least one mirror is deformable in accordance with the movement of the plurality of intermediate plates.

8. The phase modulation device according to claim 7, wherein the at least one mirror is deformable in portions between adjacent ones of the plurality of intermediate plates.

9. A phase modulation device according to claim 7, further comprising a control unit that controls the plurality of drive elements, wherein the plurality of intermediate plates are configured as a plurality of segments each made up of a predetermined number of adjacent intermediate plates, and wherein the control unit controls the plurality of drive elements so that the predetermined number of intermediate plates included in each of the plurality of segments move synchronously.

10. The phase modulation device according to claim 9, wherein the control unit controls the plurality of drive elements so that the main surfaces of the predetermined number of intermediate plates included in each of the plurality of segments are positioned on the same plane.

11. The phase modulation device according to claim 7, wherein the at least one mirror is a single mirror.

12. The phase modulation device according to claim 1, wherein the at least one mirror is composed of a substrate containing at least one of silicon, glass containing synthetic quartz, sapphire, SiC, GaN, Zn, Se, and Ge, and a reflective coating applied to the surface of the substrate.

13. A phase modulation device according to claim 12, wherein the reflective coating reflects 90% or more of light having the wavelength of the laser light and transmits 10% or more of light other than the wavelength of the laser light.

14. A phase modulation device according to claim 1, wherein the thickness of said at least one mirror is equal to or less than one tenth of said predetermined interval.

15. The phase modulation device according to claim 1, wherein the plurality of driving elements are of a piezoelectric type, an electrostatic type, or an electromagnetic type.

16. A method for manufacturing a phase modulation device, comprising the steps of: fixing a plurality of drive elements to a base plate; arranging an intermediate substrate so as to cover the plurality of drive elements; arranging at least one mirror so as to cover the intermediate substrate; and irradiating a cutting laser having a wavelength that is transmitted through the mirror through the mirror to cut the intermediate substrate and form a plurality of intermediate plates.

17. A method for manufacturing a phase modulation device according to claim 16, further comprising a step of adjusting the height of the plurality of drive elements from the base plate before the step of placing an intermediate substrate so as to cover the plurality of drive elements.

18. The method for manufacturing a phase modulation device according to claim 16, wherein the intermediate substrate is provided with a groove that serves as a guide for irradiating the cutting laser.

19. The method for manufacturing a phase modulation device according to claim 16, wherein the cutting laser has a wavelength that is transmitted by 10% or more through the at least one mirror and absorbed by 20% or more by the intermediate substrate.

20. The method for manufacturing a phase modulation device according to claim 16, wherein the wavelength of the cutting laser is 0.3 μm or more.

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