Wavefront measuring device and wavefront measuring method

Abstract

To provide a wavefront measurement device and a wavefront measurement method capable of both expanding a dynamic range and improving spatial resolution.SOLUTION: A wavefront measurement device 1 comprises: a phase modulation section 2 having a spatial light modulator 7 into which incident light L0 enters; a pattern generation section 3 for generating a phase pattern 11 to be input to the spatial light modulator 7; an imaging section 4 having an imaging area 14 for capturing an image of a part of the incident light L0 modulated by the spatial light modulator 7 as measurement light L1; and an analysis section 5 for analyzing wavefront of the incident light L1 on the basis of an imaging result by the imaging section 4. The pattern generation section 3 generates a plurality of phase patterns 11 for which a virtual pattern 12 for measurement is shifted to positions different from each other so that a focused spot 16 of the measurement light L1 modulated by the spatial light modulator 7 shifts over time to different positions in the imaging area 14.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a wavefront measuring apparatus and a wavefront measuring method. [Background technology]

[0002] Spatial light modulators (SLMs) are known as devices that electrically control and modulate the spatial distribution of light from a light source. Spatial light modulators have a variety of applications, including optical waveform shaping, optical pulse shaping, optical measurement, and optical computing. In addition to fields such as laser processing, spatial light modulators are also expected to be applied to optical wavefront measurement.

[0003] For example, in the technology described in Non-Patent Document 1, a beam is modulated using a spatial light modulator displaying a dual microlens array pattern, and the linear spots focused by each microlens and the displacement of the focused spots from a reference position are acquired by a camera. The detection area is shifted according to the displacement of the linear spots and the focused spots, and the displacement of the 2 × 2 focused spots in each detection area is acquired to measure the phase gradient in the beam cross section.

[0004] Furthermore, for example, in the technology described in Non-Patent Document 2, a spatial light modulator displaying a micro-hologram array pattern is used to modulate a beam, and the amount of displacement from a reference position at any multi-point spot is obtained by a camera. In Non-Patent Document 2, by measuring the phase gradient in the beam cross section based on the amount of displacement at any multi-point spot, it is possible to recognize the amount of displacement from the reference position even when the focal points overlap in adjacent detection areas. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] “Shack-Hartmannwavefront sensor with large dynamic range by adaptive spot search method” Hironobu Shinto et al., Applied Optics Vol. 55, Issue 20, pp. 5413-5418(2016) [Non-patent document 2] "Study on Optical Applications of Functional Phase Modulation Patterns," by Yusuke Saida, Graduate School of System Informatics, Kobe University, Dissertation No. 6649, published March 1, 2017 Summary of the Invention [Problem to be solved by the invention]

[0006] In beam wavefront measurement, achieving both an expansion of the dynamic range and an improvement of the spatial resolution is a technical challenge. In the technology described in Non-Patent Document 1, when a wavefront with a large curvature is modulated by a microlens pattern or an astigmatic microlens pattern, a problem can arise in that the shapes of the linear spot and the focused spot are distorted. If the spot shape cannot be recognized due to distortion, pattern matching will fail, and it is thought that it will be difficult to ensure the dynamic range.

[0007] Furthermore, the technology described in Non-Patent Document 2 has the problem that a certain number of pixels is required to generate a micro-hologram that can obtain a good reconstructed image. As a result, the spatial resolution is dependent on the number of pixels of the spatial light modulator used.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a wavefront measuring device and a wavefront measuring method that can achieve both an expansion of the dynamic range and an improvement in spatial resolution. [Means for solving the problem]

[0009] A wavefront measuring device according to one aspect of the present disclosure includes a phase modulation unit having a spatial light modulator that modulates incident light, a pattern generation unit that generates a phase pattern to be input to the spatial light modulator, an imaging unit having an imaging area that images at least a portion of the incident light modulated by the spatial light modulator as measurement light, and an analysis unit that analyzes the wavefront of the incident light based on the imaging results of the imaging unit, and the pattern generation unit generates multiple phase patterns in which the measurement virtual patterns are shifted to different positions so that the focal spot of the measurement light modulated by the spatial light modulator shifts to different positions in the imaging area over time.

[0010] In this wavefront measurement device, the virtual measurement patterns are shifted to different positions in multiple phase patterns input to the spatial light modulator, so that the focal spots of the measurement light modulated by the spatial light modulator shift to different positions in the imaging area over time. This allows the pitch (center-to-center distance) of the virtual measurement patterns to be increased in multiple phase patterns, thereby increasing the arrangement pitch of the focal spots in the imaging area. Increasing the arrangement pitch of the focal spots widens the detectable range per focal spot, thereby enabling an expansion of the dynamic range. Furthermore, by shifting the focal spots over time, the spatial resolution can be improved while the dynamic range is expanded. That is, when imaging using multiple phase patterns, imaging is performed with the arrangement pitch of the focal spots increased, and the spatial resolution is improved by overlaying the imaging results obtained by shifting the focal spots using multiple phase patterns. Therefore, this wavefront measurement device can achieve both an expansion of the dynamic range and an improvement of the spatial resolution.

[0011] The pattern generation unit may form multiple virtual patterns for measurement in each of the multiple phase patterns. In this case, the spatial resolution of the image obtained by one imaging can be improved, and the number of times the focused spot is shifted (the number of imaging times) can be reduced. Therefore, the scanning time within the cross section of the incident light by the virtual patterns for measurement can be shortened.

[0012] The pattern generation unit may form a single virtual measurement pattern for each of the multiple phase patterns. In this case, a sufficient detectable range per unit of the focused spot of the measurement light can be ensured. Therefore, the dynamic range can be further expanded.

[0013] The pattern generating unit may generate each phase pattern so that the virtual patterns for measurement do not overlap when the multiple phase patterns are superimposed over time. In this case, wavefront measurement can be performed in the entire modulation region of the spatial light modulator with a minimum of scanning compared to when multiple phase patterns are generated so that the virtual patterns for measurement partially overlap each other.

[0014] The pattern generator may generate each phase pattern so that when a plurality of phase patterns are superimposed over time, parts of the virtual patterns for measurement overlap with each other. In this case, the arrangement pitch of the focused spots in the imaging region can be reduced, thereby further improving the spatial resolution.

[0015] The pattern generation unit may generate each of the multiple phase patterns so that the measurement virtual pattern included in each of the multiple phase patterns occupies only a part of the modulatable area of ​​the spatial light modulator. In this case, measurement light modulated by the measurement virtual pattern and light modulated by a part other than the measurement virtual pattern can be generated simultaneously. Therefore, it is possible to perform wavefront measurement of incident light using the measurement light while extracting light other than the measurement light to the outside as output light.

[0016] The pattern generating unit may generate each phase pattern so that, when a plurality of phase patterns are superimposed over time, the virtual pattern for measurement overlaps the entire incident area of ​​the incident light on the spatial light modulator, in which case wavefront measurement can be performed over the entire incident area of ​​the incident light.

[0017] The pattern generator may generate and update a wavefront modulation pattern for the incident light based on the analysis result of the analyzer, thereby enabling wavefront modulation of the incident light while measuring the wavefront of the incident light.

[0018] Of the incident light, the focal length of the measurement light modulated by the virtual measurement pattern and the focal length of the light modulated by a portion other than the virtual measurement pattern may be different from each other. In this case, even if the light modulated by a portion other than the virtual measurement pattern is extracted as output light while performing wavefront measurement of the incident light, it is possible to prevent the output light from concentrating on the imaging region of the imaging unit and to prevent the measurement light from concentrating at the extraction destination of the output light.

[0019] A wavefront measurement method according to one aspect of the present disclosure includes a pattern input step of inputting a phase pattern into a spatial light modulator, a phase modulation step of inputting incident light into the spatial light modulator into which the phase pattern has been input and phase-modulating the incident light, an imaging step of imaging a portion of the incident light modulated by the spatial light modulator as measurement light in an imaging area of ​​an imaging unit, and an analysis step of analyzing the wavefront of the incident light based on the imaging results in the imaging step, wherein in the pattern input step, multiple phase patterns are input in which measurement virtual patterns are shifted to different positions so that the measurement light modulated by the spatial light modulator is focused at different positions in the imaging area.

[0020] In this wavefront measurement method, the measurement virtual patterns are shifted to different positions in multiple phase patterns input to the spatial light modulator, thereby shifting the focal spots of the measurement light modulated by the spatial light modulator to different positions in the imaging area over time. This allows the pitch (center-to-center distance) of the measurement virtual patterns to be increased in multiple phase patterns, thereby increasing the arrangement pitch of the focal spots in the imaging area. Increasing the arrangement pitch of the focal spots widens the detectable range per focal spot, thereby expanding the dynamic range. Furthermore, by shifting the focal spots over time, the spatial resolution can be improved while the dynamic range is expanded. That is, when imaging using multiple phase patterns, imaging is performed with the arrangement pitch of the focal spots increased, and the imaging results obtained by shifting the focal spots using multiple phase patterns are superimposed to improve the spatial resolution. Therefore, this wavefront measurement method achieves both an expansion of the dynamic range and an improvement of the spatial resolution. [Effects of the Invention]

[0021] According to the present disclosure, it is possible to achieve both an expansion of the dynamic range and an improvement of the spatial resolution. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating the principle of general wavefront measurement using a spatial light modulator. [Figure 2] 1A is a schematic diagram showing an example of a focused spot on an imaging area, and FIG. 1B is a schematic diagram showing an example of a case where it is difficult to detect the focused spot. [Figure 3] FIG. 2 is a diagram illustrating the principle of wavefront measurement when the arrangement pitch of the virtual measurement pattern is larger than that in FIG. [Figure 4] 1 is a diagram illustrating the principle of a wavefront measuring device according to an embodiment of the present invention. [Figure 5] 1 is a schematic diagram showing the configuration of a wavefront measuring apparatus according to an embodiment of the present invention. [Figure 6]5(a) to 5(d) are schematic diagrams showing examples of phase patterns generated by a pattern generating section. [Figure 7] 6(a) to 6(d) are schematic diagrams showing examples of focused spots captured by an imaging section when the phase patterns shown in FIGS. 6(a) to 6(d) are used. [Figure 8] 10 is a schematic diagram showing an example of a phase pattern in which a virtual pattern for measurement is superimposed on a wavefront modulation pattern. FIG. [Figure 9] 6 is a flowchart showing an example of the operation of the wavefront measuring apparatus shown in FIG. 5. [Figure 10] FIG. 10 is a schematic diagram showing the configuration of a wavefront measuring device according to a modified example. [Figure 11] FIG. 10 is a schematic diagram showing the configuration of a wavefront measuring device according to another modified example. [Figure 12] 10(a) and 10(b) are schematic diagrams showing modified examples of the phase pattern generated by the pattern generating unit. [Figure 13] 12(a) and 12(b) are schematic diagrams showing an example of a focused spot imaged by an imaging section when the phase patterns shown in FIGS. 12(a) and 12(b) are used. [Figure 14] 10(a) and 10(b) are schematic diagrams showing other modified examples of the phase pattern generated by the pattern generating section. [Figure 15] 14(a) and 14(b) are schematic diagrams showing an example of a focused spot imaged by an imaging section when the phase patterns shown in FIGS. 14(a) and 14(b) are used. [Figure 16] 10(a) and 10(b) are schematic diagrams showing another example of how to shift the virtual pattern for measurement 12. FIG. [Figure 17] 10(a) and 10(b) are schematic diagrams showing yet another example of how to shift the virtual pattern for measurement 12. FIG. [Figure 18] FIG. 10 is a schematic diagram showing yet another example of how to shift the virtual pattern for measurement. [Figure 19] FIG. 10 is a schematic diagram showing another example of a virtual pattern for measurement. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, preferred embodiments of a wavefront measuring device and a wavefront measuring method according to one aspect of the present disclosure will be described in detail with reference to the drawings. [General principle of wavefront measurement using spatial light modulator]

[0024] 1 is a diagram illustrating the principle of general wavefront measurement using a spatial light modulator. As shown in the figure, in general wavefront measurement using a spatial light modulator, a phase pattern 111 is input to a modulatable area 113 of a spatial light modulator 107. Measurement virtual patterns 112, which are, for example, microlens-shaped, are arranged in a matrix on the phase pattern 111. When incident light L100 enters the spatial light modulator 107 to which the phase pattern 111 has been input, the incident light L100 is modulated by the measurement virtual pattern 112 to generate measurement light L101. Then, a plurality of focused spots 116 due to the measurement light L101 are formed in an imaging area 114 of the imaging unit.

[0025] 2(a), in an area where there is no distortion in the wavefront of the incident light L100, the light-focusing spot 116 is focused at a reference position K0 on the imaging area 114, which coincides with the optical axis of the virtual pattern for measurement 112. On the other hand, in an area where there is distortion in the wavefront of the incident light L100, the light-focusing spot 116 is focused at a displacement position K1 displaced by (Δx, Δy) from the reference position K0. By detecting the amount of displacement from the reference position K0 for each light-focusing spot 116, it is possible to detect the distortion in the wavefront of the incident light L100 in the cross-sectional area where it is incident on the virtual pattern for measurement 112 corresponding to that light-focusing spot 116.

[0026] The arrangement pitch of the multiple focused spots 116 in the imaging region 114 is determined by the arrangement pitch of the virtual measurement patterns 112 (the center-to-center distance of the virtual measurement patterns 112). The size of the detectable range R per unit of the focused spots 116 is determined by the arrangement pitch of the focused spots 116. As shown in FIG. 2(b), if there is no focused spot 116 within the detectable range R (detectable range R at the lower right), if there are two or more focused spots 116 within one detectable range R (detectable range R at the upper right), or if there is a focused spot 116 on the boundary between adjacent detectable ranges R, R, it becomes difficult to detect which detectable range R the focused spot 116 has displaced from its reference position K0. The upper limit of the detectable displacement of the focused spot 116 is limited within the detectable range R.

[0027] Therefore, the dynamic range of the wavefront measurement of the incident light L100 depends on the size of the detectable range R, that is, the arrangement pitch of the measurement virtual pattern 112. The larger the arrangement pitch of the measurement virtual pattern 112, the sparser the intervals between the condensed spots 116 in the imaging region 114, and the larger the detectable range R, resulting in a larger dynamic range of the wavefront measurement. The smaller the arrangement pitch of the measurement virtual pattern 112, the denser the intervals between the condensed spots 116 in the imaging region 114, and the smaller the detectable range R, resulting in a smaller dynamic range of the wavefront measurement.

[0028] On the other hand, in the general wavefront measurement shown in FIG. 1, the spatial resolution of the wavefront measurement of the incident light L100 depends on the arrangement pitch of the measurement virtual pattern 112. For example, in the embodiment of FIG. 3, the arrangement pitch of the measurement virtual pattern 112 is larger than that of the embodiment of FIG. 1. The smaller the arrangement pitch of the measurement virtual pattern 112, the closer the intervals between the focused spots 116 in the imaging region 114, and the higher the spatial resolution of the wavefront measurement. The larger the arrangement pitch of the measurement virtual pattern 112, the sparser the intervals between the focused spots 116 in the imaging region 114, and the lower the spatial resolution of the wavefront measurement. Therefore, in general wavefront measurement using the spatial light modulator 107, there can be said to be a trade-off between the dynamic range and the spatial resolution. [Wavefront measuring device according to this embodiment]

[0029] In response to the above-mentioned problems, the wavefront measuring device according to this embodiment aims to achieve both an expanded dynamic range and improved spatial resolution. FIG. 4 is a principle diagram of the wavefront measuring device according to this embodiment. As shown in the figure, in the wavefront measuring device 1 according to this embodiment, the virtual measurement patterns 12 are shifted to different positions in multiple phase patterns 11 input to the spatial light modulator 7. In the wavefront measuring device 1, the multiple phase patterns 11 are sequentially input to the spatial light modulator 7, thereby displacing the virtual measurement patterns 12 in the modulatable region 13 of the spatial light modulator 7 over time. As a result, the focal spot 16 of the measurement light L1 modulated by the spatial light modulator 7 and the detectable range R per unit of the focal spot 16 are shifted to different positions in the imaging region 14 over time.

[0030] The configuration of the wavefront measuring device 1 described above will be described in detail below. Fig. 5 is a schematic diagram showing the configuration of a wavefront measuring device according to an embodiment of the present disclosure. As shown in the figure, the wavefront measuring device 1 includes a phase modulation unit 2, a pattern generation unit 3, an imaging unit 4, an analysis unit 5, and an output unit 6. In the example of Fig. 5, the wavefront measuring device 1 is configured as a laser processing device. The wavefront measuring device 1 as a laser processing device processes a workpiece P by irradiating the workpiece P with output light L2 whose wavefront has been corrected by the phase modulation unit 2.

[0031] The phase modulation unit 2 has a spatial light modulator 7 (see FIG. 4) into which the incident light L0 is incident. The spatial light modulator 7 is a device that electrically controls and modulates the spatial distribution of light from a light source. The incident light L0 is light that is the source of the measurement light L1 and the output light L2. Here, the portion of the incident light L0 that is modulated by a measurement virtual pattern 12 (described later) becomes the measurement light L1, and the portion modulated by a portion other than the measurement virtual pattern 12 becomes the output light L2. Examples of a light source (not shown) that outputs the incident light L0 include a fiber laser and a solid-state laser. The oscillation form of the laser light may be either pulsed oscillation or continuous oscillation.

[0032] The pattern generation unit 3 is a part that generates a phase pattern to be input to the spatial light modulator 7. Physically, the pattern generation unit 3 is a computer system that includes memories such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a hard disk. Examples of such computer systems include personal computers, cloud servers, smart devices (smartphones, tablet terminals, etc.), microcomputers, and FPGAs (field-programmable gate arrays). The pattern generation unit 3 functions as a controller for the spatial light modulator 7 by executing a program stored in the memory on the CPU of the computer system.

[0033] 6(a) to 6(d) are schematic diagrams showing examples of phase patterns generated by the pattern generation unit. As shown in FIGS. 6(a) to 6(d), the pattern generation unit 3 repeatedly generates, in this order, multiple phase patterns 11A to 11D in which the virtual pattern for measurement 12 is shifted to different positions. Here, the pattern generation unit 3 forms multiple virtual pattern groups for measurement 12A to 12D in each of the phase patterns 11A to 11D.

[0034] 6(a) to 6(d), the measurement virtual pattern groups 12A to 12D included in the phase patterns 11A to 11D, respectively, are formed so as to occupy only a part of the modulatable region 13 in the spatial light modulator 7. In other words, when the phase patterns 11A to 11D are input to the spatial light modulator 7, there is an area in the modulatable region 13 of the spatial light modulator 7 where the measurement virtual patterns 12 are not formed.

[0035] In the example of the same figure, in phase patterns 11A to 11D, virtual pattern groups for measurement 12A to 12D are configured with a total of nine virtual patterns for measurement 12 in a 3 × 3 matrix. The virtual patterns for measurement 12 are, for example, square microlens-shaped patterns. Adjacent virtual patterns for measurement 12, 12 are spaced apart by a distance equivalent to one virtual pattern for measurement 12. That is, in the example of FIGS. 6(a) to 6(d), the arrangement pitch of virtual patterns for measurement 12 (the center-to-center distance between adjacent virtual patterns for measurement 12, 12) is equal to twice the length of one side of the square virtual pattern for measurement 12. This prevents the virtual patterns for measurement 12A to 12D from overlapping with each other when phase patterns 11A to 11D are overlapped over time.

[0036] When the position of measurement virtual pattern group 12A of phase pattern 11A is taken as the reference position, measurement virtual pattern group 12B of phase pattern 11B is shifted in the +x direction (to the right on the paper) by one measurement virtual pattern 12 relative to measurement virtual pattern group 12A of phase pattern 11A (see FIG. 6(b)). Measurement virtual pattern group 12C of phase pattern 11C is shifted in the +y direction (downward on the paper) by one measurement virtual pattern 12 relative to measurement virtual pattern group 12B of phase pattern 11B (see FIG. 6(c)).

[0037] The measurement virtual pattern group 12D of the phase pattern 11D is shifted in the -x direction (leftward on the paper) by one measurement virtual pattern 12 relative to the measurement virtual pattern group 12C of the phase pattern 11C (see FIG. 6(d)). The measurement virtual pattern group 12A of the phase pattern 11A is shifted in the -y direction (upward on the paper) by one measurement virtual pattern 12 relative to the measurement virtual pattern group 12D of the phase pattern 11D (see FIG. 6(a)). This allows the measurement virtual pattern groups 12A to 12D included in the phase patterns 11A to 11D, respectively, to overlap with the entire incident region of the incident light L0 on the spatial light modulator 7 when the phase patterns 11A to 11D are superimposed over time.

[0038] The imaging unit 4 is a part that captures the measurement light L1 modulated by the spatial light modulator 7. A CCD camera, a CMOS camera, or the like can be used as a device that constitutes the imaging unit 4. As shown in the figure, the imaging unit 4 has a two-dimensional imaging area 14 (see FIGS. 7(a) to 7(d)) ​​that is configured by a plurality of pixels (not shown). In the imaging area 14, the measurement light L1 condensed by the measurement virtual pattern groups 12A to 12D included in the phase patterns 11A to 11D is repeatedly imaged in this order. The imaging unit 4 sequentially captures optical images of the condensed spot groups 16A to 16D formed by the measurement virtual pattern groups 12A to 12D, and outputs each image data to the analysis unit 5.

[0039] 7(a) to 7(d) are schematic diagrams showing examples of focused spots imaged by the imaging unit when the phase patterns shown in FIGS. 6(a) to 6(d) are used. Here, for the convenience of explaining the relationship between the shift of the virtual measurement pattern 12 and the shift of the focused spot 16, the focused spot 16 is shown at the reference position K0 (see FIG. 2) when there is no wavefront distortion in the incident light L0. As shown in the figures, the focused spot groups 16A to 16D correspond to the virtual measurement pattern groups 12A to 12D in the phase patterns 11A to 11D shown in FIGS. 6(a) to 6(d), respectively, and are composed of a total of nine focused spots 16 arranged in a 3×3 matrix.

[0040] The diameter of each of the focused spots 16 constituting the focused spot groups 16A to 16D is inversely proportional to the diameter of the microlens represented by the virtual pattern for measurement 12 (i.e., the size of the virtual pattern for measurement 12). The reference positions K0, K0 of adjacent focused spots 16, 16 are spaced apart at an interval corresponding to the arrangement pitch of the virtual pattern for measurement 12. The detectable range R per unit of the focused spot 16 of the measurement light L1 formed by the virtual pattern groups for measurement 12A to 12D is determined according to the arrangement pitch of the virtual pattern for measurement 12. The smaller the arrangement pitch of the virtual pattern for measurement 12, the smaller the detectable range R per unit of the focused spot 16. The larger the arrangement pitch of the virtual pattern for measurement 12, the larger the detectable range R per unit of the focused spot 16.

[0041] When the position of the light-focusing spot group 16A formed by the measurement virtual pattern group 12A is set as a reference position, the position of the light-focusing spot group 16B is shifted in the +x direction (to the right on the paper) relative to the light-focusing spot group 16A by the arrangement pitch of the measurement virtual pattern 12 (see FIG. 7(b)). The position of the light-focusing spot group 16C is shifted in the +y direction (to the bottom on the paper) relative to the light-focusing spot group 16B by the arrangement pitch of the measurement virtual pattern 12 (see FIG. 7(c)).

[0042] The position of the condensed spot group 16D is shifted in the -x direction (leftward on the paper) relative to the condensed spot group 16C by the arrangement pitch of the virtual pattern for measurement 12 (see FIG. 7(d)). The position of the condensed spot group 16A is shifted in the -y direction (upward on the paper) relative to the condensed spot group 16D by the arrangement pitch of the virtual pattern for measurement 12 (see FIG. 7(a)).

[0043] The analysis unit 5 is a part that analyzes the wavefront of the incident light L0 based on the imaging results of the imaging unit 4. Physically, the analysis unit 5 is a computer system that includes memories such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, and a storage unit such as a hard disk. Examples of such computer systems include personal computers, cloud servers, smart devices (smartphones, tablet terminals, etc.), microcomputers, and FPGAs (field-programmable gate arrays). The analysis unit 5 may be a system integrated with the pattern generation unit 3. The analysis unit 5 analyzes the wavefront of the incident light L0 by executing a program stored in the memory on the CPU of the computer system.

[0044] The analysis unit 5 analyzes the wavefront of the incident light L0 based on a plurality of image data that are the imaging results of the light-focus spot groups 16A-16D generated using the measurement virtual pattern groups 12A-12D that are shifted over time by the spatial light modulator 7. The analysis unit 5 detects the amount of displacement (Δx, Δy) of the light-focus spot 16 from the reference position K0 for each of the detectable ranges R of the light-focus spot 16 based on the image data received from the imaging unit 4 (see FIG. 2). By detecting the amount of displacement of each light-focus spot 16 from the reference position K0, the analysis unit 5 detects the distortion of the wavefront of the incident light L0 in the cross-sectional area incident on the measurement virtual pattern 12 corresponding to each light-focus spot 16.

[0045] The analysis unit 5 may map the wavefront distortion in each cross-sectional region of the incident light L0 and generate a wavefront modulation pattern 18 (see FIG. 8) for modulating the wavefront of the incident light L0 into a desired wavefront depending on the application of the output light L2. The wavefront modulation pattern 18 is a pattern for modulating the wavefront of the incident light L0 entering the spatial light modulator 7, and is generated separately from the measurement virtual pattern 12. By outputting the design information generated by the analysis unit 5 to the pattern generation unit 3 and inputting the wavefront modulation pattern 18 generated by the pattern generation unit 3 to the spatial light modulator 7, it becomes possible to correct the wavefront of the incident light L0 so that the beam pattern of the output light L2 has various types, such as a top-hat type or a Gaussian type.

[0046] The wavefront modulation pattern 18 is updated as needed in accordance with the detection results of the wavefront distortion of the incident light L0. By modulating the incident light L0 using the wavefront modulation pattern 18, the wavefront of the output light L2 irradiated onto the workpiece P can be maintained at a desired wavefront. As shown in FIG. 8, when the phase patterns 11A to 11D and the wavefront modulation pattern 18 are input to the spatial light modulator 7 in an overlapping manner, it is possible to simultaneously perform wavefront measurement of the incident light L0 and wavefront modulation of the incident light L0.

[0047] The output unit 6 is a part that outputs the output light L2 to the outside. In this embodiment, as shown in FIG. 5, a beam splitter 19 is arranged on the optical path of the measurement light L1 and output light L2 traveling from the phase modulation unit 2 to the imaging unit 4. The measurement light L1 passes through the beam splitter 19 toward the imaging unit 4, and the output light L2 is reflected by the beam splitter 19 and travels toward the workpiece P. The output light L2 is collected by a collecting lens 20 and irradiated onto the surface of the workpiece P. The beam splitter 19 is an element for adjusting the light intensity and has, for example, a transmittance of approximately 5% (a reflectance of approximately 95%). Although not shown in FIG. 5, in reality, the light traveling toward the imaging unit 4 may contain a portion of the output light L2, and the light traveling toward the workpiece P may contain a portion of the measurement light L1.

[0048] In this embodiment, the focus of measurement light L1 is adjusted to coincide with the imaging region 14 of the imaging unit 4, and the focus of output light L2 is adjusted to coincide with the surface of the workpiece P. Furthermore, in this embodiment, the focal length of measurement light L1 modulated by the measurement virtual pattern 12 is different from the focal length of light (output light L2) modulated by a portion other than the measurement virtual pattern 12. If the focal length of measurement light L1 transmitted from the spatial light modulator 7 through the beam splitter 19 to form an image on the imaging region 14 of the imaging unit 4 is F1, and the focal length of output light L2 reflected from the spatial light modulator 7 by the beam splitter 19 to form an image on the surface of the workpiece P via the condenser lens 20 is F2, then F1≠F2. The magnitude relationship between F1 and F2 is arbitrary. It may be F1>F2 or F2>F1.

[0049] 9 is a flowchart showing an example of the operation of the wavefront measuring device shown in FIG. 5. As shown in the figure, in the wavefront measuring device 1, first, incident light L0 is input to the spatial light modulator 7, and output light L2 is irradiated onto the workpiece P (step S01). Next, a plurality of phase patterns 11 are input to the spatial light modulator 7 (step S02: pattern input step). In step S02, phase patterns 11A to 11D in which measurement virtual pattern groups 12A to 12D are shifted to different positions are repeatedly input to the spatial light modulator 7 in this order. When the incident light L0 enters the spatial light modulator 7 to which the phase patterns 11A to 11D have been sequentially input, the incident light L0 is phase-modulated, and measurement light L1 is generated (step S03: phase modulation step).

[0050] Next, the measurement light L1 modulated by the spatial light modulator 7 is imaged (step S04: imaging step). In step S04, the optical images of the condensed spot groups 16A to 16D formed by the measurement virtual pattern groups 12A to 12D are sequentially imaged. That is, image data of the optical images of the condensed spot groups 16A to 16D that shift over time to different positions in the imaging region 14 by the measurement virtual pattern groups 12A to 12D are sequentially acquired.

[0051] After acquiring the image data, the wavefront of the incident light L0 is analyzed based on the imaging results of step S04 (step S05: analysis step). In step S05, the wavefront of the incident light L0 is analyzed based on a plurality of image data, which are imaging results of the focused spot groups 16A to 16D generated using the measurement virtual pattern groups 12A to 12D shifted over time by the spatial light modulator 7. In step S05, the amount of displacement of each focused spot 16 from the reference position K0 is detected, thereby detecting distortion of the wavefront of the incident light L0 in the cross-sectional area incident on the measurement virtual pattern 12 corresponding to each focused spot 16. After detecting the wavefront distortion, a wavefront modulation pattern 18 is generated (step S06). If the wavefront modulation pattern 18 has already been generated, the wavefront modulation pattern 18 is updated based on the new wavefront detection result.

[0052] Next, the wavefront modulation pattern 18 generated or updated in step S06 is input to the spatial light modulator 7 (step S07). The wavefront modulation pattern 18 is superimposed on the phase patterns 11A to 11D and input to the spatial light modulator 7, and analysis of the wavefront of the incident light L0 and irradiation of the output light L2 onto the workpiece P are simultaneously performed. Thereafter, it is determined whether or not processing of the workpiece P has been completed (step S08). If it is determined in step S08 that processing of the workpiece P has been completed, the process ends. If it is determined in step S08 that processing of the workpiece P has not been completed, the process returns to step S02, and the processes of steps S02 to S08 are executed again.

[0053] As described above, in the wavefront measuring device 1, the measurement virtual pattern groups 12A-12D are shifted to different positions in the multiple phase patterns 11A-11D input to the spatial light modulator 7, and the focused spot groups 16A-16D of the measurement light L1 modulated by the spatial light modulator 7 are shifted to different positions in the imaging region 14 over time. This makes it possible to increase the pitch (center-to-center distance) of the measurement virtual patterns 12 included in the measurement virtual pattern groups 12A-12D in the multiple phase patterns 11A-11D, and to increase the arrangement pitch of the focused spots 16 of the focused spot groups 16A-16D in the imaging region 14. Increasing the arrangement pitch of the focused spots 16 widens the detectable range R per unit of the focused spots 16, thereby enabling an expansion of the dynamic range. Furthermore, by shifting the focused spots 16 over time, the spatial resolution can be improved while the dynamic range is expanded. That is, when imaging using the plurality of phase patterns 11A to 11D, imaging is performed with the arrangement pitch of the light-focusing spots 16 increased, and the imaging results obtained by shifting the light-focusing spots 16 using the plurality of phase patterns 11A to 11D are superimposed, thereby improving the spatial resolution. Therefore, the wavefront measuring device 1 can achieve both an expansion of the dynamic range and an improvement of the spatial resolution.

[0054] In this embodiment, the pattern generation unit 3 forms a plurality of virtual patterns for measurement (groups of virtual patterns for measurement 12A to 12D) for each of the plurality of phase patterns 11A to 11D. This improves the spatial resolution of the image obtained by one imaging, thereby reducing the number of times the focused spot 16 is shifted (number of imaging operations). Therefore, the scanning time of the incident light L0 within the cross section by the virtual pattern for measurement 12 can be shortened.

[0055] In this embodiment, the pattern generation unit 3 generates each of the phase patterns 11A to 11D so that the measurement virtual pattern groups 12A to 12D do not overlap each other when the multiple phase patterns 11A to 11D are superimposed over time. For example, in the measurement virtual pattern groups 12A to 12D, adjacent measurement virtual patterns 12, 12 are spaced apart by an interval equivalent to one measurement virtual pattern 12 (see FIGS. 6(a) to 6(d)). This makes it possible to perform wavefront measurement in the entire modulation region of the spatial light modulator 7 with a minimum amount of scanning, compared to when the phase patterns 11A to 11D are generated so that the measurement virtual pattern groups 12A to 12D partially overlap each other.

[0056] In this embodiment, the pattern generation unit 3 generates each phase pattern such that the measurement virtual pattern groups 12A to 12D included in each of the multiple phase patterns 11A to 11D occupy only a portion of the modulatable region 13 in the spatial light modulator 7. This makes it possible to simultaneously generate measurement light L1 modulated by the measurement virtual pattern groups 12A to 12D and light modulated by a portion other than the measurement virtual pattern groups 12A to 12D. Therefore, it is possible to perform wavefront measurement of the incident light L0 using the measurement light L1, while extracting light other than the measurement light L1 to the outside as output light L2.

[0057] In this embodiment, the pattern generation unit 3 generates each of the phase patterns 11A to 11D so that, when the multiple phase patterns 11A to 11D are superimposed over time, the measurement virtual pattern 12 overlaps the entire incident area of ​​the incident light L0 in the spatial light modulator 7. This makes it possible to perform wavefront measurement over the entire incident area of ​​the incident light L0. As a result, it becomes possible to apply the wavefront modulation pattern 18 to the entire cross section of the output light L2, and it is possible to easily bring the wavefront of the output light L2 closer to a desired wavefront.

[0058] In this embodiment, the pattern generation unit 3 generates and updates the wavefront modulation pattern 18 for the incident light L0 based on the analysis results of the analysis unit 5. This makes it possible to perform wavefront modulation of the incident light L0 while performing wavefront measurement of the incident light L0. Furthermore, in this embodiment, the focal length of the measurement light L1 modulated by the measurement virtual pattern 12 is different from the focal length of the light (output light L2) modulated in a portion other than the measurement virtual pattern 12. This makes it possible to prevent the output light L2 from being focused on the imaging region 14 of the imaging unit 4, and to prevent the measurement light L1 from being focused on the workpiece P, which is the destination of the output light L2, even if the light modulated in a portion other than the measurement virtual pattern 12 is extracted as output light L2 while performing wavefront measurement of the incident light L0. [Variations]

[0059] The present disclosure is not limited to the above-described embodiments. For example, as in a wavefront measuring device 1A shown in FIG. 10 , an image transfer lens system 21 may be disposed in the optical path of the measurement light L1 between the beam splitter 19 and the imaging unit 4. The image transfer lens system 21 may be configured, for example, by a pair of convex lenses 22, 22. In this case, it is not necessary to directly image the focused spot 16 of the measurement light L1 onto the imaging area 14 of the imaging unit 4, thereby increasing the degree of freedom in optical arrangement. Furthermore, while the above-described embodiments are configured such that the incident light L0 is reflected by the spatial light modulator 7, it may also be configured such that the incident light L0 is transmitted through the spatial light modulator 7, as in a wavefront measuring device 1B shown in FIG. 11 . Even in such a configuration, the same effects as those of the above-described embodiments can be achieved.

[0060] In the above embodiment, a square-shaped virtual pattern for measurement 12 is exemplified, but the shape of the virtual pattern for measurement 12 may be any shape as long as the focused spot 16 can be formed in the imaging area 14 of the imaging unit 4. In other words, the virtual pattern for measurement 12 is not limited to a square shape, and may be other shapes such as a circle, a rectangle, an ellipse, a triangle, or a polygon.

[0061] In the above embodiment, the phase patterns 11A to 11D in which the virtual patterns for measurement 12 are arranged in a 3 × 3 matrix are exemplified, but the number and arrangement pitch of the virtual patterns for measurement 12 can be set arbitrarily. For example, as shown in Fig. 12(a), a phase pattern 11 in which the virtual patterns for measurement 12 are arranged in a 4 × 4 matrix may be used, or as shown in Fig. 12(b), a phase pattern 11 in which the virtual patterns for measurement 12 are arranged in a 2 × 2 matrix may be used.

[0062] If the size of the virtual patterns for measurement 12 is not changed, the more the number of virtual patterns for measurement 12 is arranged, the smaller the arrangement pitch between adjacent focused spots 16, 16 becomes (see FIG. 13(a)). Therefore, the spatial resolution is improved. By improving the spatial resolution, the number of times of imaging required to obtain a certain spatial resolution can be reduced, and the speed of wavefront measurement is also improved. Furthermore, if the size of the virtual patterns for measurement 12 is not changed, the more the number of virtual patterns for measurement 12 is arranged, the larger the area that the virtual patterns for measurement 12 occupy with respect to the modulatable region 13 of the spatial light modulator 7. Therefore, the number of phase patterns 11 required for wavefront measurement of the entire incident region of the incident light L0 can be reduced, and the number of times of imaging can also be reduced, thereby improving the speed of wavefront measurement.

[0063] If the size of the virtual patterns for measurement 12 is not changed, the fewer the number of virtual patterns for measurement 12 arranged, the larger the arrangement pitch between adjacent focused spots 16, 16 (see FIG. 13(b)). Therefore, the detectable range R per unit of focused spot 16 becomes larger, and the dynamic range is improved. Furthermore, if the size of the virtual patterns for measurement 12 is not changed, the fewer the number of virtual patterns for measurement 12 arranged, the smaller the area occupied by the virtual patterns for measurement 12 with respect to the modulatable region 13 of the spatial light modulator 7 becomes. Therefore, loss of light used for wavefront measurement is suppressed, and wavefront measurement of the incident light L0 becomes possible while sufficiently maintaining the intensity of the output light L2.

[0064] The wavefront of the incident light L0 may change over time due to the influence of self-heating of the light source, etc. When laser processing the workpiece P as in this embodiment, it is useful to measure the wavefront in real time and modulate the wavefront of the incident light L0 (output light L2). In this case, before the output light L2 is irradiated onto the workpiece P, it is preferable to increase the number of arrangements of the measurement virtual patterns 12 and perform wavefront measurement at high speed to generate the wavefront modulation pattern 18. During the stage of irradiating the output light L2 onto the workpiece P, it is also possible to reduce the number of arrangements of the measurement virtual patterns 12 without changing their size, or to reduce the size of the measurement virtual patterns without changing their number, thereby reducing the area occupied by the measurement virtual patterns 12 relative to the modulatable region 13 of the spatial light modulator 7, and perform wavefront measurement in real time while maintaining the intensity of the output light L2.

[0065] The size of the virtual pattern for measurement 12 can also be adjusted arbitrarily. For example, as shown in FIG. 14(a), the size of the virtual pattern for measurement 12 may be approximately twice the size of the virtual pattern for measurement 12 shown in FIGS. 6(a) to 6(d). Alternatively, as shown in FIG. 14(b), the size of the virtual pattern for measurement 12 may be approximately half the size of the virtual pattern for measurement 12 shown in FIGS. 6(a) to 6(d). The size of the focused spot 16 in the imaging area 14 varies depending on the size of the virtual pattern for measurement 12. When the size of the virtual pattern for measurement 12 is increased as shown in FIG. 14(a), the size of the focused spot 16 in the imaging area 14 becomes smaller (see FIG. 15(a)). When the size of the virtual pattern for measurement 12 is reduced as shown in FIG. 14(b), the size of the focused spot 16 in the imaging area 14 becomes larger (see FIG. 15(b)).

[0066] When the size of the focused spot 16 is reduced, the light intensity at the focused spot 16 increases. For example, if the intensity of the incident light L0 is strong at the center of the laser cross section and weak at the periphery, the accuracy of the wavefront measurement can be stabilized by changing the size of the measurement virtual pattern 12 depending on the position to which the measurement virtual pattern 12 is shifted. When the size of the focused spot 16 is increased, the center point of the focused spot 16 can be determined by performing a center calculation based on the intensity distribution of the measurement virtual pattern 12. Therefore, regardless of the size of the measurement virtual pattern 12, it is possible to achieve both an improvement in the dynamic range and an improvement in the spatial resolution.

[0067] In the above embodiment, multiple virtual patterns for measurement 12 are formed in each of the multiple phase patterns 11A to 11D, but the pattern generation unit 3 may form a single virtual pattern for measurement 12 in each of the multiple phase patterns 11. In this case, by generating multiple phase patterns 11 in which the single virtual pattern for measurement 12 is shifted to different positions from each other, the same effects as in the above embodiment can be achieved. Furthermore, when a single virtual pattern for measurement 12 is used, the detectable range R per unit of the condensed spot 16 of the measurement light L1 can be sufficiently ensured. For example, when a single virtual pattern for measurement 12 is used, a single condensed spot 16 is formed in the imaging region 14, so the entire region of the imaging region 14 can be made the detectable range R. Therefore, the dynamic range can be further expanded.

[0068] It is possible to arbitrarily set the way (scan direction) of shifting the virtual pattern for measurement 12 by the multiple phase patterns 11. When each phase pattern 11 includes a single virtual pattern for measurement 12, for example, as shown in Fig. 16(a), the virtual pattern for measurement 12 may be moved back and forth from the initial position in the -x direction (leftward on the paper) and the +x direction (rightward on the paper), and the virtual pattern for measurement 12 may be shifted in the +y direction for each scan in the -x direction and the +x direction.

[0069] 16(b), for example, the virtual pattern for measurement 12 may be moved back and forth from the initial position in the +y direction (downward on the paper) and the -y direction (upward on the paper), and the virtual pattern for measurement 12 may be shifted in the +x direction for each scan in the +y direction and the -y direction. The virtual pattern for measurement 12 may be shifted in a direction that is horizontally inverted from that in FIG. 16(a), or may be shifted in a direction that is vertically inverted from that in FIG. 16(b).

[0070] When each phase pattern 11 includes multiple measurement virtual patterns 12, for example, as shown in FIG. 17(a), each measurement virtual pattern 12 may be reciprocated from its initial position in the +x direction (to the right on the paper) and the −x direction (to the left on the paper), and the measurement virtual pattern 12 may be shifted in the +y direction for each scan in the +x direction and the −x direction.

[0071] 17(b), the scanning directions of a pair of virtual patterns for measurement 12, 12 may be reversed. In this case, one virtual pattern for measurement 12 may be moved back and forth from its initial position in the +x direction (to the right on the paper) and the −x direction (to the left on the paper), and the virtual pattern for measurement 12 may be shifted in the +y direction for each scan in the +x direction and the −x direction. The other virtual pattern for measurement 12 may be moved back and forth from its initial position in the −x direction (to the left on the paper) and the +x direction (to the right on the paper), and the virtual pattern for measurement 12 may be shifted in the −y direction for each scan in the −x direction and the +x direction.

[0072] In the examples of Figures 17(a) and 17(b), the scan areas of each virtual measurement pattern 12 do not overlap each other. This reduces the number of phase patterns 11 required for wavefront measurement of the entire incident area of ​​the incident light L0, and also reduces the number of times images are captured, thereby improving the speed of wavefront measurement. As in the cases of Figures 16(a) and 16(b), each virtual measurement pattern 12 may be shifted in a direction that is horizontally inverted from that of Figure 17(a), or in a direction that is vertically inverted from that of Figure 17(b). Even if the number of virtual measurement patterns 12 included in the phase pattern 11 is greater, the shifting methods shown in Figures 17(a) and 17(b) may be applied to each virtual measurement pattern 12.

[0073] In the above embodiment, adjacent measurement virtual patterns 12, 12 in phase patterns 11A to 11D are spaced apart by an interval equivalent to one measurement virtual pattern 12, so that when multiple phase patterns 11 are overlapped over time, the measurement virtual patterns 12 do not overlap. However, the method of shifting the measurement virtual patterns 12 is not limited to this. For example, as shown in FIG. 18 , the pattern generation unit 3 may generate each phase pattern 11 so that when multiple phase patterns 11 are overlapped over time, parts of the measurement virtual patterns 12, 12 overlap.

[0074] With this configuration, even if the number of virtual patterns for measurement 12 arranged in each phase pattern 11 is reduced, the arrangement pitch of the focused spots 16 in the imaging area 14 can be reduced. Therefore, the spatial resolution can be further improved. There is no particular limit to the overlap width between the portions of the virtual patterns for measurement 12, 12. More than half of the areas of the virtual patterns for measurement 12, 12 may overlap, or less than half of the areas of the virtual patterns for measurement 12, 12 may overlap.

[0075] In the above embodiment, a microlens-shaped pattern was exemplified as the measurement virtual pattern 12, but the form of the measurement virtual pattern 12 is not limited to this. The measurement virtual pattern 12 may be, for example, a diffraction grating-shaped pattern or a hologram array-shaped pattern. Alternatively, for example, a 10 × 10 microlens-shaped measurement virtual pattern 12 shown in FIG. 19(a) may be superimposed with a 10 × 10 optical vortex-shaped measurement virtual pattern 12 shown in FIG. 19(b). In this case, as shown in FIG. 19(c), the focused spot 16 on the imaging region 14 is formed by a 10 × 10 multi-point optical vortex beam. Even in this embodiment, the same effects as those of the above embodiment can be achieved by shifting the measurement virtual pattern 12 over time. [Explanation of symbols]

[0076] 1, 1A, 1B... wavefront measurement device, 2... phase modulation section, 3... pattern generation section, 4... imaging section, 5... analysis section, 7... spatial light modulator, 11... phase pattern, 12... virtual pattern for measurement, 13... modulatable area, 14... imaging area, 16... focused spot, 18... wavefront modulation pattern, L0... incident light, L1... measurement light

Claims

1. a phase modulation unit having a spatial light modulator that modulates incident light; a pattern generator that generates a phase pattern to be input to the spatial light modulator; an imaging unit having an imaging area that captures, as measurement light, at least a portion of the incident light modulated by the spatial light modulator; an analysis unit that analyzes a wavefront of the incident light based on an image pickup result by the image pickup unit, The pattern generation unit generates a plurality of phase patterns in which measurement virtual patterns are shifted to different positions so that the focal spot of the measurement light modulated by the spatial light modulator shifts to different positions in the imaging area over time, and generates and updates a wavefront modulation pattern for the incident light based on the analysis results of the analysis unit.

2. The wavefront measuring device according to claim 1 , wherein the pattern generating unit forms a plurality of virtual patterns for measurement in each of the plurality of phase patterns.

3. The wavefront measuring device according to claim 1 , wherein the pattern generating unit forms a single virtual pattern for measurement in each of the plurality of phase patterns.

4. 4. The wavefront measuring device according to claim 1, wherein the pattern generating unit generates each phase pattern so that the measurement virtual patterns do not overlap each other when the plurality of phase patterns are superimposed over time.

5. 4. The wavefront measuring device according to claim 1, wherein the pattern generating unit generates each phase pattern so that, when the plurality of phase patterns are superimposed over time, portions of the measurement virtual patterns overlap with each other.

6. The wavefront measuring device according to any one of claims 1 to 5, wherein the pattern generating unit generates each phase pattern so that the measurement virtual pattern included in each of the plurality of phase patterns occupies only a portion of the modulatable area of ​​the spatial light modulator.

7. The wavefront measuring device according to any one of claims 1 to 6, wherein the pattern generating unit generates each phase pattern so that, when the multiple phase patterns are superimposed over time, the measurement virtual pattern overlaps with the entire incident area of ​​the incident light in the spatial light modulator.

8. 8. The wavefront measuring device according to claim 1, wherein, of the incident light, a focal length of the measurement light modulated by the measurement virtual pattern and a focal length of light modulated by a portion other than the measurement virtual pattern are different from each other.

9. a pattern input step of inputting a phase pattern to the spatial light modulator; a phase modulation step of inputting incident light into the spatial light modulator to which the phase pattern has been input, and phase-modulating the incident light; an imaging step of imaging a part of the incident light modulated by the spatial light modulator as measurement light in an imaging area of ​​an imaging unit; an analyzing step of analyzing a wavefront of the incident light based on an imaging result in the imaging step; generating and updating a wavefront modulation pattern for the incident light based on the analysis result in the analyzing step, a wavefront measurement method in which the pattern input step inputs a plurality of phase patterns in which the measurement virtual pattern is shifted to different positions from each other so that the focused spot of the measurement light modulated by the spatial light modulator shifts to different positions in the imaging area over time;

Images