Three-dimensional measuring device and light source device

Abstract

A three-dimensional measuring device is provided that can eliminate the shift in initial phase in each of a plurality of stripe patterns that is caused by the positional shift of a light source unit. [Solution] A three-dimensional measuring device 101B includes a plurality of light source units 102 that irradiate an object to be measured with measurement light having a predetermined pattern, an imaging unit 103 that images the object to be measured irradiated with the measurement light, and a measurement unit 104 that measures the three-dimensional shape of the object to be measured based on the imaging results by the imaging unit 103. The predetermined pattern of the measurement light includes a stripe pattern, and the stripe patterns of the measurement light irradiated from the plurality of light source units 102 are each different. The plurality of light source units 102 are arranged in a direction parallel to the stripes in the stripe pattern. The measurement unit 104 measures the three-dimensional shape of the object to be measured based on a three-dimensional shape measurement method using the stripe pattern.

Description

[Technical field]

[0001] The present disclosure relates to a three-dimensional measuring device and a light source device. [Background technology]

[0002] A conventional three-dimensional measurement method is, for example, the method described in Patent Document 1. In the method of Patent Document 1, a random dot pattern is projected onto the object to be measured, and two cameras capture the dot patterns at the same positions. Then, based on the parallax between the two dot patterns, three-dimensional measurement of the object is performed according to the principle of triangulation.

[0003] For example, the method described in Patent Document 2 is a measurement method using a phase shift method. In the method of Patent Document 2, a reference plate having a reference surface onto which a grating pattern is projected is prepared, and the reference plate is translated in the normal direction by a stage. An image of the grating pattern projected onto the reference surface and an image of the grating pattern projected onto the object to be measured are captured, and the spatial coordinates of the object to be measured are calculated using a table that associates the phase of the grating pattern with spatial coordinates. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2008 / 0240502 [Patent Document 2] JP 2011-242178 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure aims to provide a three-dimensional measurement device and a light source device that can eliminate the initial phase shift in each of multiple stripe patterns caused by misalignment of the light source unit in a measurement method using multiple stripe patterns. [Means for solving the problem]

[0006] A three-dimensional measuring device according to one aspect of the present disclosure includes a plurality of light source units that irradiate a measurement object with measurement light having a predetermined pattern, an imaging unit that images the measurement object irradiated with the measurement light, and a measurement unit that measures a three-dimensional shape of the measurement object based on an imaging result by the imaging unit. The predetermined pattern of the measurement light includes a stripe pattern, and the stripe patterns of the measurement light irradiated from the plurality of light source units each have a different pattern. The plurality of light source units are arranged in a direction parallel to the stripes in the stripe pattern. The measurement unit measures the three-dimensional shape of the measurement object based on a three-dimensional shape measurement method using the stripe pattern.

[0007] A light source device according to one aspect of the present disclosure is a light source device used in a three-dimensional measuring device that measures a three-dimensional shape of a measurement object based on a three-dimensional shape measurement method using a stripe pattern, and includes a plurality of light source units that irradiate the measurement object with measurement light having a predetermined pattern. The predetermined pattern of the measurement light includes a stripe pattern, and the stripe patterns of the measurement light irradiated from the plurality of light source units each have a different pattern. The plurality of light source units are arranged in a direction parallel to the stripes in the stripe pattern.

[0008] According to these three-dimensional measuring apparatus and light source device, it is possible to eliminate the shift in the initial phase in each of the plurality of sinusoidal stripe patterns, which is caused by the positional deviation of the light source unit.

[0009] Each of the light source units may be composed of an M-point oscillating S-iPMSEL. In the method of Patent Document 1 described above, a projector is used as the light source, and in the method of Patent Document 2, an LED array is used as the light source. This causes a problem that the three-dimensional measuring device becomes relatively large. As an imaging device, for example, an ultra-small camera of 1 mm square or less has been developed, so miniaturization of the light source is important for miniaturizing the entire three-dimensional measuring device. If the entire three-dimensional measuring device can be miniaturized, it is considered that it is possible to apply it to applications such as oral examination, endoscopic examination, inspection of narrow places such as the inside of a tube or a gap in a wall, inspection of furniture and equipment from under the floor, and to construct a handy type three-dimensional measuring device. In addition, when applying a light source to a three-dimensional measuring device, it is preferable that the light source has reduced noise and distortion of the output light from the viewpoint of improving the measurement accuracy. The S-iPMSEL has a phase modulation layer having a basic layer and a plurality of modified refractive index areas having a refractive index different from that of the basic layer, and the center of gravity position of each modified refractive index area is shifted from the lattice point position of a virtual square lattice according to the output light image. The S-iPMSEL is configured to be, for example, the size of a needle tip, and can output a two-dimensional pattern light image in a direction perpendicular to or inclined to the main surface of a substrate on which a phase modulation layer is provided. Therefore, by using an S-iPMSEL as a light source, it is possible to reduce the overall size of a three-dimensional measurement device, thereby expanding the range of application of the device. In addition, by using an M-point oscillation S-iPMSEL, it is possible to eliminate the output of zero-order light (diffracted wave components that are not phase-modulated), which differs from the desired two-dimensional pattern light image. This makes it possible to irradiate the measurement object with measurement light of a pattern that is free of noise and distortion due to zero-order light, thereby improving measurement accuracy.

[0010] The predetermined pattern of the measurement light may be a superimposed pattern in which a periodic stripe pattern and a random dot pattern are superimposed, and the measurement unit may measure the three-dimensional shape of the measurement object based on a phase shift method using the superimposed pattern. In the phase shift method, discontinuity at phase 2π is an issue. In contrast, by using a random dot pattern, it is possible to improve the discontinuity at phase 2π, and high-precision three-dimensional measurement can be achieved with a small number of patterns.

[0011] The stripe patterns of the measurement light irradiated from the multiple light source units may be gray code patterns including different gray codes, and the measurement unit may measure the three-dimensional shape of the measurement object based on a triangulation method using the gray code patterns. The number of patterns of the gray code patterns may be small compared to the number of pixels of the imaging unit, so irradiation of the measurement light having the gray code pattern can be realized with a small number of light source units. When the gray code is used, the Hamming distance between adjacent pixels is 1, and even if a bit error occurs when restoring a bit string, the error is contained within 1. In other words, the gray code provides a code that is resistant to noise. In addition, in the phase shift method, discontinuity at the phase 2π is an issue. In contrast, by using the gray code, it is possible to improve the discontinuity at the phase 2π, and high-precision three-dimensional measurement can be realized with a small number of patterns.

[0012] The stripe pattern of the measurement light irradiated from the multiple light source units is a periodic stripe pattern, each having a different phase shift, and the measurement unit may measure the three-dimensional shape of the object to be measured based on a phase shift method using the stripe pattern.

[0013] The stripe pattern may be a sinusoidal stripe pattern.

[0014] The phases of the stripe patterns of the measurement light irradiated from the multiple light source units may be shifted by 2π / N (N is the number of phase shifts of the stripe pattern). Effect of the Invention

[0015] According to the present disclosure, there is provided a three-dimensional measuring device that can eliminate the shift in initial phase in each of a plurality of sinusoidal stripe patterns caused by misalignment of a light source unit in a measurement method using a plurality of stripe patterns. [Brief description of the drawings]

[0016] [Figure 1]FIG. 2 is a partially sectional perspective view showing the configuration of an S-iPMSEL. [Diagram 2] FIG. 1 is a cross-sectional view showing a layered structure of an S-iPMSEL. [Diagram 3] FIG. 2 is a plan view of a phase modulation layer. [Figure 4] 2 is an enlarged view of a unit constituent region R. FIG. [Diagram 5] 11 is a plan view showing an example in which a substantially periodic refractive index structure is applied within a specific region of a phase modulation layer. FIG. [Figure 6] 1A and 1B are diagrams illustrating the relationship between an optical image obtained by focusing an output beam pattern of an S-iPMSEL and a rotation angle distribution in a phase modulation layer. [Figure 7] FIG. 2 is a diagram for explaining coordinate conversion from spherical coordinates to coordinates in an XYZ orthogonal coordinate system. [Figure 8] FIG. 1 is a plan view showing a reciprocal lattice space for a phase modulation layer of an M-point lasing S-iPMSEL. [Figure 9] FIG. 1 is a conceptual diagram illustrating a state in which a diffraction vector is added to an in-plane wave vector. [Figure 10] FIG. 13 is a diagram for illustrating a schematic structure surrounding a light line. [Figure 11] FIG. 13 is a diagram conceptually illustrating an example of a rotation angle distribution φ2(x, y). [Figure 12] 1 is a conceptual diagram for explaining a state in which a diffraction vector is added to a vector obtained by removing a wave number spread from an in-plane wave number vector in a direction. [Figure 13] FIG. 13 is a plan view of a phase modulation layer according to a modified example. [Figure 14] 13A and 13B are diagrams illustrating the positional relationship of modified refractive index areas in a phase modulation layer according to a modified example. [Figure 15] 1 is a schematic diagram showing the configuration of a three-dimensional measuring apparatus according to a first embodiment. [Figure 16] FIG. 2 is a diagram showing an example of a periodic pattern used in the first embodiment. [Figure 17] FIG. 1 is a diagram showing an example of a far-field pattern of a periodic pattern. [Figure 18]FIG. 3 is a diagram showing an example of a random dot pattern used in the first embodiment. [Figure 19] FIG. 4 is a diagram showing an example of a pattern having a uniform density used in the first embodiment. [Figure 20] FIG. 1 shows an example of an FFP with a pattern having uniform density. [Figure 21] FIG. 11 is a schematic diagram showing the configuration of a three-dimensional measuring apparatus according to a second embodiment. [Figure 22] FIG. 11 is a diagram showing an example of a Gray code pattern used in the second embodiment. [Figure 23] FIG. 11 is a diagram showing an example of a sine wave stripe pattern used in the second embodiment. [Figure 24] FIG. 11 is a diagram showing an example of a sinusoidal matrix pattern used in the second embodiment. [Diagram 25] FIG. 13 is a diagram showing the improvement of discontinuity at a phase of 2π. [Figure 26] FIG. 11 is a diagram showing an example of a moire fringe pattern used in the second embodiment. [Figure 27] FIG. 11 is a diagram showing an example of a superimposition pattern used in the second embodiment. [Figure 28] FIG. 11 is a diagram showing another example of a superimposition pattern used in the second embodiment. [Figure 29] FIG. 11 is a schematic diagram showing the configuration of a three-dimensional measuring apparatus according to a third embodiment. [Diagram 30] 4 is a schematic perspective view showing an example of the arrangement of a light source unit and an imaging unit. FIG. [Diagram 31] 13 is a schematic perspective view showing another example of the arrangement of the light source unit and the imaging unit. FIG. [Diagram 32] FIG. 11 is a perspective view showing an example of forming a sine wave stripe pattern. [Diagram 33] 1A and 1B are schematic diagrams showing an example of a multi-point pattern laser light and a stripe pattern using the same. [Diagram 34] 11A to 11C are schematic diagrams showing another example of a multi-point pattern laser light and a stripe pattern using the same. [Diagram 35]FIG. 1 is a schematic cross-sectional view showing an example configuration of a metalens structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, preferred embodiments of a three-dimensional measuring apparatus according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0018] A three-dimensional measuring device 101 according to this embodiment is configured to include one or more light source units 102 that irradiate a measurement object SA with measurement light 105 having a predetermined pattern, one or more imaging units 103 that image the measurement object SA irradiated with the measurement light 105, and a measurement unit 104 that measures the three-dimensional shape of the measurement object SA based on the imaging results by the imaging units 103 (see FIG. 15, etc.). The light source unit 102 is configured of M-point oscillation S-iPMSELs (Static-integrable Phase Modulating Surface Emitting Lasers) 1.

[0019] In the three-dimensional measuring device 101, the light source unit 102 is configured using an S-iPMSEL1 configured the size of a needle tip, thereby making it possible to miniaturize the entire device and expanding the range of application of the device. In addition, in the three-dimensional measuring device 101, by using an M-point oscillation S-iPMSEL1, it is possible to eliminate the output of zero-order light (diffracted wave components that are not phase-modulated) that differs from the optical image of the desired two-dimensional pattern. This makes it possible to irradiate the measurement object SA with measurement light 105 of a pattern that is free of noise and distortion due to zero-order light, thereby improving the measurement accuracy. [M-point oscillation S-iPMSEL]

[0020] First, the M-point oscillation S-iPMSEL1 will be described. Fig. 1 is a partially sectional perspective view showing the configuration of the S-iPMSEL. Fig. 2 is a sectional view showing the layered structure of the S-iPMSEL. Fig. 1 defines an XYZ orthogonal coordinate system in which the axis extending in the thickness direction of the S-iPMSEL1 at the center of the S-iPMSEL1 is the Z axis.

[0021] The S-iPMSEL1 is a laser light source that forms a standing wave in the XY plane direction and outputs a phase-controlled plane wave in the Z axis direction. The S-iPMSEL1 outputs a two-dimensional optical image of any shape in a direction perpendicular to the main surface 10a of the semiconductor substrate 10 (i.e., the Z axis direction), in a direction inclined relative to the Z axis direction, or in both directions.

[0022] 1 and 2, the S-iPMSEL 1 includes an active layer 12 as a light emitting portion provided on a semiconductor substrate 10, a pair of cladding layers 11 and 13 sandwiching the active layer 12, and a contact layer 14 provided on the cladding layer 13. The semiconductor substrate 10, the cladding layers 11 and 13, and the contact layer 14 are made of a compound semiconductor such as a GaAs-based semiconductor, an InP-based semiconductor, or a nitride-based semiconductor. The energy band gaps of the cladding layer 11 and the cladding layer 13 are larger than the energy band gap of the active layer 12. The thickness directions of the semiconductor substrate 10 and the layers 11 to 14 coincide with the Z-axis direction.

[0023] The S-iPMSEL1 further includes a phase modulation layer 15 optically coupled to the active layer 12. In this embodiment, the phase modulation layer 15 is provided between the active layer 12 and the cladding layer 13. The thickness direction of the phase modulation layer 15 coincides with the Z-axis direction. The phase modulation layer 15 may be provided between the cladding layer 11 and the active layer 12. An optical guide layer may be provided, if necessary, between at least one of the active layer 12 and the cladding layer 13 and the active layer 12 and the cladding layer 11. The optical guide layer may include a carrier barrier layer for efficiently confining carriers in the active layer 12.

[0024] The phase modulation layer 15 is configured to include a base layer 15a made of a first refractive index medium, and a plurality of modified refractive index areas 15b made of a second refractive index medium having a refractive index different from that of the first refractive index medium and present in the base layer 15a. The plurality of modified refractive index areas 15b include a substantially periodic structure. When the equivalent refractive index of the mode is n, the wavelength λ selected by the phase modulation layer 15 is 0(=(√2)a×n, a is the lattice spacing) is included in the emission wavelength range of the active layer 12. The phase modulation layer 15 has a wavelength λ 0 The laser light incident on the phase modulation layer 15 forms a predetermined mode according to the arrangement of the modified refractive index areas 15b in the phase modulation layer 15, and is output to the outside from the surface of the S-iPMSEL1 as a laser beam having a desired pattern.

[0025] The S-iPMSEL1 further includes an electrode 16 provided on the contact layer 14 and an electrode 17 provided on the back surface 10b of the semiconductor substrate 10. The electrode 16 is in ohmic contact with the contact layer 14, and the electrode 17 is in ohmic contact with the semiconductor substrate 10. The electrode 17 has an opening 17a. The electrode 16 is provided in a central region of the contact layer 14. A portion of the contact layer 14 other than the electrode 16 is covered with a protective film 18 (see FIG. 2). The contact layer 14 not in contact with the electrode 16 may be removed to limit the current range. A portion of the back surface 10b of the semiconductor substrate 10 other than the electrode 17 is covered with an anti-reflection film 19, including the inside of the opening 17a. The anti-reflection film 19 in the region other than the opening 17a may be removed.

[0026] In the S-iPMSEL1, when a driving current is supplied between the electrodes 16 and 17, recombination of electrons and holes occurs in the active layer 12, causing the active layer 12 to emit light. The electrons and holes that contribute to this emission, and the light generated in the active layer 12, are efficiently confined between the cladding layers 11 and 13.

[0027] The light emitted from the active layer 12 enters the phase modulation layer 15 and forms a predetermined mode according to the lattice structure inside the phase modulation layer 15. The laser light emitted from the phase modulation layer 15 is directly output from the back surface 10b through the opening 17a to the outside of the S-iPMSEL1. Alternatively, the laser light emitted from the phase modulation layer 15 is reflected by the electrode 16 and then output from the back surface 10b through the opening 17a to the outside of the S-iPMSEL1. At this time, the signal light (measurement light 105) contained in the laser light is output in an arbitrary two-dimensional direction including a direction perpendicular to the main surface 10a or a direction inclined thereto. It is this signal light that forms a desired optical image. The signal light is mainly 1st order light and −1st order light of the laser light. The 0th order light of the laser light is not output from the phase modulation layer 15 of this embodiment.

[0028] FIG. 3 is a plan view of the phase modulation layer 15. As shown in the figure, the phase modulation layer 15 includes a base layer 15a made of a first refractive index medium and a plurality of modified refractive index areas 15b made of a second refractive index medium having a refractive index different from that of the first refractive index medium. In FIG. 3, a virtual square lattice is set in the XY plane for the phase modulation layer 15. One side of the square lattice is parallel to the X axis, and the other side is parallel to the Y axis. A square unitary constituent region R having a lattice point O of the square lattice as its center is set two-dimensionally over a plurality of columns along the X axis and a plurality of rows along the Y axis. When the XY coordinates of each unitary constituent region R are defined by the center of gravity of each unitary constituent region R, these center of gravity positions coincide with the lattice point O of the virtual square lattice. The plurality of modified refractive index areas 15b are provided, for example, one by one, in each unitary constituent region R. The planar shape of the modified refractive index area 15b is, for example, a circular shape. The lattice point O may be located outside the modified refractive index area 15b, or may be included inside the modified refractive index area 15b.

[0029] The ratio of the area S of the modified refractive index area 15b to one unit constituent area R is called a filling factor (FF). If the lattice spacing of the square lattice is a, the filling factor FF of the modified refractive index area 15b is S / a 2where S is the area of ​​the modified refractive index area 15b in the XY plane. For example, if the shape of the modified refractive index area 15b is a perfect circle, the filling factor FF is given by S=π(d / 2) where d is the diameter of the perfect circle. 2 When the modified refractive index area 15b has a square shape, the filling factor FF is given by S=LA where LA is the length of one side of the square. 2 is given as:

[0030] FIG. 4 is an enlarged view of the unitary constituent region R. As shown in the figure, each of the modified refractive index areas 15b has a center of gravity G. Here, the angle between the vector from the lattice point O toward the center of gravity G and the X-axis is φ(x, y). x indicates the position of the x-th lattice point on the X-axis, and y indicates the position of the y-th lattice point on the Y-axis. When the rotation angle φ is 0°, the direction of the vector connecting the lattice point O and the center of gravity G coincides with the positive direction of the X-axis. In addition, the length of the vector connecting the lattice point O and the center of gravity G is r(x, y). In one example, r(x, y) is constant throughout the phase modulation layer 15, regardless of x and y.

[0031] As shown in FIG. 3, the direction of the vector connecting the lattice point O and the center of gravity G, i.e., the rotation angle φ of the center of gravity G of the modified refractive index area 15b around the lattice point O, is set individually for each lattice point O according to a phase pattern corresponding to a desired optical image. The phase pattern, i.e., the rotation angle distribution φ(x, y) has a specific value for each position determined by the values ​​of x and y, but is not necessarily expressed by a specific function. The rotation angle distribution φ(x, y) is determined by extracting the phase distribution from the complex amplitude distribution obtained by Fourier transforming the desired optical image. When obtaining the complex amplitude distribution from the desired optical image, it is possible to improve the reproducibility of the beam pattern by applying an iterative algorithm such as the Gerchberg-Saxton (GS) method, which is commonly used in calculations for generating holograms.

[0032] FIG. 5 is a plan view showing an example in which a refractive index approximately periodic structure is applied in a specific region of the phase modulation layer. In the example shown in FIG. 5, an approximately periodic structure (for example, the structure shown in FIG. 3) for emitting a target beam pattern is formed inside a square inner region RIN. Meanwhile, in the outer region ROUT surrounding the inner region RIN, a perfect circular modified refractive index region whose center of gravity coincides with the lattice point position of a square lattice is arranged. The filling factor FF in the outer region ROUT is set to, for example, 12%. The lattice interval of the virtually set square lattice is the same (=a) inside the inner region RIN and in the outer region ROUT. In the case of this structure, light is also distributed in the outer region ROUT, so that it is possible to suppress the generation of high-frequency noise (so-called window function noise) caused by a sudden change in light intensity in the periphery of the inner region RIN. In addition, it is possible to suppress light leakage in the in-plane direction, and a reduction in threshold current can be expected.

[0033] FIG. 6 is a diagram for explaining the relationship between an optical image obtained by focusing the output beam pattern of the S-iPMSEL1 and the rotation angle distribution φ(x, y) in the phase modulation layer 15. The center Q of the output beam pattern is not necessarily located on an axis perpendicular to the main surface 10a of the semiconductor substrate 10, but it can be located on a perpendicular axis. For convenience of explanation, in FIG. 6, the center Q is assumed to be on an axis perpendicular to the main surface 10a. In FIG. 6, four quadrants with the center Q as the origin are shown. In the example of FIG. 6, the letter "A" appears in the third quadrant, and the letter "A" rotated 180 degrees appears in the first quadrant. When the output beam pattern is a rotationally symmetric optical image (for example, a cross, a circle, a double circle, etc.), they are overlapped and observed as one optical image. As shown in Figure 4, when the center of gravity G of the modified refractive index area 15b in the S-iPMSEL1 is shifted in the circumferential direction around the lattice point O, there is no intensity difference between the output beam pattern in the first quadrant and the output beam pattern in the third quadrant, as shown in Figure 6. However, when the center of gravity G of the modified refractive index area 15b in the S-iPMSEL1 is shifted onto a straight line passing through the lattice point O, as shown in Figure 14 described below, it is possible to create an intensity difference between the output beam pattern in the first quadrant and the output beam pattern in the third quadrant.

[0034] The optical image of the output beam pattern of the S-iPMSEL1 includes at least one of a spot, a dot, a straight line, a cross, a line drawing, a grid pattern, a photograph, a striped pattern, CG (computer graphics), and a character. To obtain a desired optical image, the rotation angle distribution φ(x, y) of the modified refractive index area 15b in the phase modulation layer 15 is determined by the following procedure.

[0035] As a first prerequisite, in an XYZ orthogonal coordinate system defined by a Z axis coinciding with the normal direction and an XY plane coinciding with one surface of phase modulation layer 15 including multiple modified refractive index areas 15b, a virtual square lattice composed of M1 (an integer greater than or equal to 1) × N1 (an integer greater than or equal to 1) unit constituent regions R having a square shape is set on the XY plane.

[0036] As a second precondition, the coordinates (ξ, η, ζ) in the XYZ orthogonal coordinate system satisfy the relationships shown in the following formulas (1) to (3) with respect to the spherical coordinates (r, θrot, θtilt) defined by the length r of the moving radius, the tilt angle θtilt from the Z axis, and the rotation angle θrot from the X axis specified on the XY plane, as shown in Fig. 7. Fig. 7 is a diagram for explaining the coordinate conversion from the spherical coordinates (r, θrot, θtilt) to the coordinates (ξ, η, ζ) in the XYZ orthogonal coordinate system, and the coordinates (ξ, η, ζ) express a designed light image on a predetermined plane set in the XYZ orthogonal coordinate system, which is a real space.

[0037] When the beam pattern corresponding to the optical image output from the S-iPMSEL1 is a set of bright points facing the direction defined by the angles θtilt and θrot, the angles θtilt and θrot are converted into a coordinate value kx on the Kx axis corresponding to the X axis, which is a normalized wave number defined by the following formula (4), and a coordinate value ky on the Ky axis corresponding to the Y axis and perpendicular to the Kx axis, which is a normalized wave number defined by the following formula (5). The normalized wave number means a wave number normalized by setting the wave number 2π / a corresponding to the lattice interval of a virtual square lattice to 1.0. At this time, in the wave number space defined by the Kx axis and the Ky axis, a specific wave number range including the beam pattern corresponding to the optical image is composed of M2 (an integer equal to or greater than 1)×N2 (an integer equal to or greater than 1) image regions FR each having a square shape. Note that the integer M2 does not need to match the integer M1. Similarly, the integer N2 does not need to match the integer N1. Furthermore, formulas (4) and (5) are disclosed, for example, in Y. Kurosaka et al., "Effects of non-lasing band intwo-dimensional photonic-crystal lasers clarified using omnidirectional bandstructure," Opt. Express 20, 21773-21783 (2012).

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[0038] As a third precondition, in wavenumber space, image regions FR(kx,ky) specified by coordinate component kx (an integer between 0 and M2-1) in the Kx direction and coordinate component ky (an integer between 0 and N2-1) in the Ky direction are transformed into unit constituent regions R(x,y) on the XY plane specified by coordinate component x (an integer between 0 and M1-1) in the X direction and coordinate component y (an integer between 0 and N1-1) in the Y direction, to obtain complex amplitude F(x,y), where j is the imaginary unit, as given by the following formula (6). When the amplitude term is A(x,y) and the phase term is P(x,y), the complex amplitude F(x,y) is defined by the following formula (7). As a fourth prerequisite, the unit constituent region R(x,y) is defined by s-axis and t-axis which are parallel to the X-axis and Y-axis, respectively, and perpendicular to each other at the lattice point O(x,y) which is the center of the unit constituent region R(x,y).

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[0039] Under the above first to fourth prerequisites, the phase modulation layer 15 is configured to satisfy the following fifth and sixth conditions. That is, the fifth condition is satisfied when the center of gravity G is disposed in a state separated from the lattice point O(x, y) in the unit constituent region R(x, y). The sixth condition is satisfied when, in a state in which the line segment length r2(x, y) from the lattice point O(x, y) to the corresponding center of gravity G is set to a common value in each of the M1×N1 unit constituent regions R, the angle φ(x, y) between the line segment connecting the lattice point O(x, y) and the corresponding center of gravity G and the s-axis is φ(x,y)=C×P(x,y)+B C: proportionality constant, e.g. 180° / π B: Any constant, e.g. 0 This is satisfied by arranging the corresponding modified refractive index area 15b within the unit constituent area R(x, y) so as to satisfy the following relationship.

[0040] Next, the M-point oscillation of the S-iPMSEL1 will be described. For the M-point oscillation of the S-iPMSEL1, it is preferable that the lattice spacing a of a virtual square lattice, the emission wavelength λ of the active layer 12, and the equivalent refractive index n of the mode satisfy the condition λ=(√2)n×a. FIG. 8 is a plan view showing a reciprocal lattice space related to the phase modulation layer of the S-iPMSEL for M-point oscillation. Point P in the figure represents a reciprocal lattice point. Arrow B1 in the figure represents a fundamental reciprocal lattice vector, and arrows K1, K2, K3, and K4 represent four in-plane wave number vectors. Each of the in-plane wave number vectors K1 to K4 has a wave number spread SP due to the rotation angle distribution φ(x, y).

[0041] The shape and size of the wave number spread SP are the same as those of the above-mentioned Γ-point oscillation. In the M-point oscillation S-iPMSEL1, the magnitude of the in-plane wave number vectors K1 to K4 (i.e., the magnitude of the standing wave in the in-plane direction) is smaller than the magnitude of the primitive reciprocal lattice vector B1. Therefore, the vector sum of the in-plane wave number vectors K1 to K4 and the primitive reciprocal lattice vector B1 does not become 0, and the wave number in the in-plane direction cannot become 0 due to diffraction, so diffraction does not occur in the direction perpendicular to the plane (Z-axis direction). In this state, the M-point oscillation S-iPMSEL1 does not output the 0th order light in the direction perpendicular to the plane (Z-axis direction), and the 1st order light and the -1st order light in the direction inclined with respect to the Z-axis direction.

[0042] In this embodiment, the following device is applied to the phase modulation layer 15 in the M-point oscillation S-iPMSEL1, so that it is possible to output a part of the 1st order light and the -1st order light without outputting the 0th order light. Specifically, as shown in Fig. 9, a diffraction vector V having a certain magnitude and direction is added to the in-plane wave vectors K1 to K4, so that the magnitude of at least one of the in-plane wave vectors K1 to K4 (the in-plane wave vector K3 in the figure) is made smaller than 2π / λ. In other words, at least one of the in-plane wave vectors K1 to K4 (the in-plane wave vector K3) after the diffraction vector V is added is contained within a circular region (light line) LL with a radius of 2π / λ.

[0043] In FIG. 9, the in-plane wave vectors K1 to K4 shown by dashed lines represent the wave vectors before the addition of the diffraction vector V, and the in-plane wave vectors K1 to K4 shown by solid lines represent the wave vectors after the addition of the diffraction vector V. The light line LL corresponds to the total reflection condition, and a wave vector having a magnitude that falls within the light line LL has a component in the direction perpendicular to the surface (Z-axis direction). In one example, the direction of the diffraction vector V is along the Γ-M1 axis or the Γ-M2 axis. The magnitude of the diffraction vector V is within the range of 2π / (√2)a-2π / λ to 2π / (√2)a+2π / λ, and is, for example, 2π / (√2)a.

[0044] Next, the magnitude and direction of the diffraction vector V for placing at least one of the in-plane wave vectors K1 to K4 within the light line LL will be considered. The following formulas (8) to (11) show the in-plane wave vectors K1 to K4 before the diffraction vector V is added.

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[0045] When the diffraction vector V is expressed as in the following formula (14), the in-plane wave number vectors K1 to K4 after the diffraction vector V is added become the following formulas (15) to (18).

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[0046] In formulas (15) to (18), if it is considered that any of the wave vectors K1 to K4 falls within the light line LL, the relationship of the following formula (19) holds.

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[0047] The size (radius) of the light line LL is set to 2π / λ for the following reason. FIG. 10 is a diagram for explaining a schematic structure around the light line LL. This diagram shows the boundary between the device and air as viewed from a direction perpendicular to the Z-axis direction. The magnitude of the wave vector of light in a vacuum is 2π / λ, but when light propagates through a device medium as shown in FIG. 10, the magnitude of the wave vector Ka in the medium with a refractive index of n is 2πn / λ. At this time, in order for light to propagate through the boundary between the device and air, the wave number components parallel to the boundary must be continuous (law of conservation of wave number).

[0048] In FIG. 10, when the wave vector Ka and the Z axis form an angle θ, the length of the wave vector Kb projected onto the plane (i.e., the in-plane wave vector) is (2πn / λ)sinθ. On the other hand, due to the relationship of the refractive index of the medium, n>1, the law of conservation of wave numbers does not hold true when the in-plane wave vector Kb in the medium is at an angle greater than 2π / λ. In this case, the light is totally reflected and cannot be extracted to the air side. The magnitude of the wave vector corresponding to this total reflection condition is the magnitude of the light line LL, i.e., 2π / λ.

[0049] As an example of a specific method for adding the diffraction vector V to the in-plane wave vectors K1 to K4, a method of superimposing a rotation angle distribution φ2(x,y) (second phase distribution) that is unrelated to the optical image on a rotation angle distribution φ1(x,y) (first phase distribution) that is a phase distribution according to the optical image can be considered. In this case, the rotation angle distribution φ(x,y) of the phase modulation layer 15 is expressed as φ(x,y)=φ1(x,y)+φ2(x,y). As described above, φ1(x,y) corresponds to the phase of the complex amplitude when the optical image is Fourier transformed. Also, φ2(x,y) is a rotation angle distribution for adding the diffraction vector V that satisfies the above formula (19).

[0050] FIG. 11 is a diagram conceptually illustrating an example of the rotation angle distribution φ2(x,y). In the example of the figure, a first phase value φA and a second phase value φB different from the first phase value φA are arranged in a checkered pattern. In one example, the phase value φA is 0 (rad), and the phase value φB is π (rad). In this case, the first phase value φA and the second phase value φB change by π. By arranging the phase values ​​in this way, a diffraction vector V along the Γ-M1 axis or the Γ-M2 axis can be suitably realized. In the case of the checkered arrangement, V=(±π / a, ±π / a), and the diffraction vector V and the wave number vectors K1 to K4 in FIG. 8 are exactly offset. The angular distribution θ2(x,y) of the diffraction vector V is expressed as the inner product of the diffraction vector V(Vx,Vy) and the position vector r(x,y). In other words, the angular distribution θ2(x,y) of the diffraction vector V is expressed as θ2(x,y) = V r = Vxx + Vyy.

[0051] In the above embodiment, when the wave number spread based on the angular spread of the optical image is included in a circle of radius Δk centered on a certain point in the wave number space, it can be simply considered as follows. By adding a diffraction vector V to the in-plane wave number vectors K1 to K4 in four directions, the magnitude of at least one of the in-plane wave number vectors K1 to K4 in four directions is made smaller than 2π / λ (light line LL). This can be considered as making the magnitude of at least one of the in-plane wave number vectors K1 to K4 in four directions smaller than the value {(2π / λ)-Δk} obtained by subtracting the wave number spread Δk from 2π / λ by adding a diffraction vector V to the in-plane wave number vectors K1 to K4 in four directions.

[0052] FIG. 12 is a diagram conceptually illustrating the above state. As shown in the figure, when a diffraction vector V is added to the in-plane wave vectors K1 to K4 excluding the wave number spread Δk, the magnitude of at least one of the in-plane wave vectors K1 to K4 becomes smaller than {(2π / λ)-Δk}. In FIG. 12, the region LL2 is a circular region with a radius of {(2π / λ)-Δk}. In FIG. 12, the in-plane wave vectors K1 to K4 shown by the dashed lines represent the state before the diffraction vector V is added, and the in-plane wave vectors K1 to K4 shown by the solid lines represent the state after the diffraction vector V is added. The region LL2 corresponds to the total reflection condition considering the wave number spread Δk, and the wave vectors whose magnitude falls within the region LL2 will also propagate in the direction perpendicular to the surface (Z-axis direction).

[0053] In this embodiment, the magnitude and direction of the diffraction vector V for placing at least one of the in-plane wave vectors K1 to K4 within the region LL2 will be described. The following formulas (20) to (23) show the in-plane wave vectors K1 to K4 before the diffraction vector V is added.

number

number

number

number

[0054] Here, when the diffraction vector V is expressed as in the above-mentioned formula (14), the in-plane wave number vectors K1 to K4 after the diffraction vector V is added become the following formulas (24) to (27).

number

number

number

number

[0055] In formulas (24) to (27), if it is considered that any of the in-plane wave vectors K1 to K4 falls within region LL2, the relationship of the following formula (28) is established. That is, by adding a diffraction vector V that satisfies formula (28), any of the in-plane wave vectors K1 to K4 excluding the wave number spread Δk falls within region LL2. Even in such a case, it is possible to output a part of the 1st order light and the −1st order light without outputting the 0th order light.

number

[0056] Fig. 13 is a plan view of a phase modulation layer according to a modified example. Fig. 14 is a diagram showing the positional relationship of modified refractive index areas in a phase modulation layer according to a modified example. As shown in Figs. 13 and 14, the center of gravity G of each modified refractive index area 15b of a phase modulation layer 15 according to a modified example is disposed on a straight line D. The straight line D passes through a lattice point O corresponding to each unit constituent area R and is inclined with respect to each side of the square lattice. In other words, the straight line D is inclined with respect to both the X-axis and the Y-axis. The inclination angle of the straight line D with respect to one side (X-axis) of the square lattice is θ.

[0057] The tilt angle θ is constant in the phase modulation layer 15B. The tilt angle θ satisfies 0°<θ<90°, and in one example, θ=45°. Alternatively, the tilt angle θ satisfies 180°<θ<270°, and in one example, θ=225°. When the tilt angle θ satisfies 0°<θ<90° or 180°<θ<270°, the straight line D extends from the first quadrant to the third quadrant of the coordinate plane defined by the X-axis and the Y-axis. The tilt angle θ satisfies 90°<θ<180°, and in one example, θ=135°. Alternatively, the tilt angle θ satisfies 270°<θ<360°, and in one example, θ=315°. When the inclination angle θ satisfies 90°<θ<180° or 270°<θ<360°, the straight line D extends from the second quadrant to the fourth quadrant of the coordinate plane defined by the X-axis and the Y-axis. Thus, the inclination angle θ is an angle excluding 0°, 90°, 180°, and 270°.

[0058] Here, the distance between the lattice point O and the center of gravity G is r(x,y). x is the position of the x-th lattice point on the X-axis, and y is the position of the y-th lattice point on the Y-axis. When the distance r(x,y) is a positive value, the center of gravity G is located in the first quadrant (or the second quadrant). When the distance r(x,y) is a negative value, the center of gravity G is located in the third quadrant (or the fourth quadrant). When the distance r(x,y) is 0, the lattice point O and the center of gravity G coincide with each other. The tilt angles are preferably 45°, 135°, 225°, and 275°. At these tilt angles, only two of the four wave vectors (for example, in-plane wave vectors (±π / a, ±π / a)) that form the standing wave at point M are phase modulated, and the other two are not phase modulated, so that a stable standing wave can be formed.

[0059] The distance r(x, y) between the center of gravity G of each modified refractive index area and the lattice point O corresponding to each unit constituent area R is set individually for each modified refractive index area 15b according to a phase pattern corresponding to the desired optical image. The phase pattern, i.e., the distribution of distance r(x, y) has a specific value for each position determined by the values ​​of x and y, but is not necessarily expressed by a specific function. The distribution of distance r(x, y) is determined from the phase distribution extracted from the complex amplitude distribution obtained by performing an inverse Fourier transform on the desired optical image.

[0060] That is, as shown in FIG. 14, the phase P(x, y) at a certain coordinate (x, y) is P 0 If so, set the distance r(x,y) to 0 and the phase P(x,y) to π+P 0 If so, the distance r(x,y) is set to the maximum value R 0 and the phase P(x,y) is set to -π+P 0 If so, set the distance r(x,y) to the minimum value -R 0 For the intermediate phase P(x,y), r(x,y) = {P(x,y) - P 0}×R 0 The distance r(x,y) is taken so that the initial phase P 0 can be set arbitrarily.

[0061] If the lattice spacing of a virtual square lattice is a, the maximum value of r(x,y) is R 0 is within the range of the following formula (29), for example: When determining the complex amplitude distribution from a desired optical image, it is possible to improve the reproducibility of the beam pattern by applying an iterative algorithm such as the Gerchberg-Saxton (GS) method, which is commonly used in calculations for generating holograms.

number

[0062] In this embodiment, a desired optical image can be obtained by determining the distribution of the distance r(x, y) of the modified refractive index area 15b of the phase modulation layer 15. Under the same first to fourth preconditions as those of the above-mentioned embodiment, the phase modulation layer 15 is configured to satisfy the following condition. That is, the distance r(x, y) from the lattice point O(x, y) to the center of gravity G of the corresponding modified refractive index area 15b is r(x,y)=C×(P(x,y)-P 0 ) C: Proportional constant, e.g. R 0 / π P 0 : Any constant, e.g. 0 The corresponding modified refractive index area 15b is disposed within the unit constituent area R(x, y) so as to satisfy the following relationship.

[0063] That is, the distance r(x,y) is the distance between the phase P(x,y) at a certain coordinate (x,y) and the 0 If so, it is set to 0 and the phase P(x,y) is π+P 0 If R is the maximum value 0 and the phase P(x,y) is set to -π+P 0 If -R is the minimum 0 When a desired optical image is to be obtained, the optical image is subjected to an inverse Fourier transform, and a distribution of distances r(x,y) according to the phase P(x,y) of the complex amplitude is provided to the multiple modified refractive index areas 15b. The phase P(x,y) and the distances r(x,y) may be proportional to each other.

[0064] In this embodiment, similarly to the above-described embodiment, the lattice spacing a of the virtual square lattice and the emission wavelength λ of the active layer 12 satisfy the condition for M-point oscillation. Furthermore, when considering the reciprocal lattice space in the phase modulation layer 15, the magnitude of at least one of the in-plane wave vectors in four directions each including the wave number spread due to the distribution of the distance r(x, y) can be made smaller than 2π / λ (light line).

[0065] In this embodiment, the following device is applied to the phase modulation layer 15 in the S-iPMSEL 1 oscillating at point M, so that the 0th order light is not outputted into the light line, and a part of the 1st order light and the -1st order light is outputted. Specifically, as shown in FIG. 9, a diffraction vector V having a certain magnitude and direction is added to the in-plane wave vectors K1 to K4, so that the magnitude of at least one of the in-plane wave vectors K1 to K4 is made smaller than 2π / λ. That is, at least one of the in-plane wave vectors K1 to K4 after the diffraction vector V is added is placed within a circular region (light line) LL of radius 2π / λ. By adding the diffraction vector V that satisfies the above-mentioned formula (19), one of the in-plane wave vectors K1 to K4 is placed within the light line LL, and a part of the 1st order light and the -1st order light is outputted.

[0066] 12, by adding a diffraction vector V to the in-plane wave vectors K1 to K4 in four directions minus the wave number spread Δk (i.e., the in-plane wave vectors in four directions in an M-point oscillation square lattice PCSEL), the magnitude of at least one of the in-plane wave vectors K1 to K4 in four directions may be made smaller than the value obtained by subtracting the wave number spread Δk from 2π / λ {(2π / λ)-Δk}. That is, by adding a diffraction vector V that satisfies the above-mentioned formula (28), any one of the in-plane wave vectors K1 to K4 falls within the region LL2, and a part of the 1st order light and the −1st order light is output.

[0067] As an example of a specific method of adding the diffraction vector V to the in-plane wave vectors K1 to K4, a method of superimposing a distance distribution r2(x,y) (second phase distribution) that is unrelated to the optical image on a distance distribution r1(x,y) (first phase distribution) that is a phase distribution according to the optical image can be considered. In this case, the distance distribution r(x,y) of the phase modulation layer 15 is r(x,y)=r1(x,y)+r2(x,y) As described above, r1(x,y) corresponds to the phase of the complex amplitude when the optical image is Fourier transformed. r2(x,y) is a distance distribution for adding the diffraction vector V that satisfies the above formula (19) or formula (28). A specific example of the distance distribution r2(x,y) is the same as that shown in FIG. [First embodiment of three-dimensional measuring device]

[0068] FIG. 15 is a schematic diagram showing the configuration of a three-dimensional measuring apparatus 101A according to the first embodiment. As shown in the figure, the three-dimensional measuring apparatus 101A includes a single light source unit 102, a plurality (a pair) of imaging units 103, and a measuring unit 104. The light source unit 102 is configured by the above-mentioned M-point oscillation S-iPMSEL1. The measuring light 105 emitted from the light source unit 102 is irradiated onto a certain area on the surface of the measurement object SA placed on the stage 106. The stage 106 may be a scanning stage capable of scanning in two-dimensional or three-dimensional directions. Note that when the irradiation range of the measuring light 105 is sufficiently wide compared to the measurement range of the measurement object SA, the arrangement of the stage 106 may be omitted.

[0069] In this embodiment, the predetermined pattern of the measurement light 105 is a periodic pattern W1 consisting of any one of a dot pattern, a stripe pattern, and a grid pattern. In the example of FIG. 16, the periodic pattern W1 of the measurement light 105 is a periodic dot pattern shown in an image area of ​​100×100 pixels. In this dot pattern, dots are arranged in a matrix shape, and the dot period is 5 pixels in both the vertical and horizontal directions. FIG. 17 is a diagram showing an example of a far-field image of a periodic pattern. FIG. 17(a) is a far-field image of 40×40 dots, FIG. 17(b) is a far-field image of 60×60 dots, FIG. 17(c) is a far-field image of 80×80 dots, and FIG. 17(d) is a far-field image of 120×120 dots. The driving conditions of the light source unit 102 are a current of 0.5 A, a pulse width of 50 ns, a pulse interval of 5 μs, and a temperature of 25° C. The center of the figure is the center of the measurement light 105 in the direction perpendicular to the surface, and the scale bar in the figure corresponds to 15°. The far-field patterns shown in these figures are designed so that the dots are arranged in a matrix on a flat screen, and the distortion of the arrangement away from the center is caused by the optical system of the measurement system.

[0070] The imaging unit 103 is configured by a device having sensitivity to the measurement light 105 emitted from the light source unit 102. For example, a CCD (Charge Coupled Device) camera, a CMOS (Complementary MOS) camera, or other two-dimensional image sensors can be used as the imaging unit 103. The imaging unit 103 images the measurement object SA in a state where the measurement light 105 is irradiated thereon, and outputs an output signal indicating the imaging result to the measurement unit 104.

[0071] The measurement unit 104 is configured by a computer system including, for example, a processor, a memory, and the like. The measurement unit 104 executes various control functions by the processor. Examples of the computer system include a personal computer, a microcomputer, a cloud server, and a smart device (such as a smartphone or a tablet terminal). The measurement unit 104 may be configured by a programmable logic controller (PLC) or an integrated circuit such as a field-programmable gate array (FPGA).

[0072] The measuring unit 104 is communicably connected to the imaging unit 103, and performs three-dimensional shape measurement of the measurement object SA based on an output signal input from the imaging unit 103. In this embodiment, the measuring unit 104 measures the three-dimensional shape of the measurement object SA based on an active stereo method using the periodic pattern W1. Here, as an example, a three-dimensional shape measurement method based on the principle of parallel equipotential stereo is shown. If the parallax of the pair of imaging units 103, 103 is D, the distance between the pair of imaging units 103, 103 is b, the focal length of the pair of imaging units 103, 103 is f, and the distance from the pair of imaging units 103, 103 to the measurement object SA is Z, the parallax D is given by D = (f / Z)b. Since the distance b between the imaging units 103, 103 and the focal length of the imaging units 103, 103 are both unique values, the distance Z to the measurement object SA can be obtained by obtaining the parallax D.

[0073] In this embodiment, the measurement light 105 having a periodic pattern W1 is irradiated onto the measurement object SA. At this time, the measurement unit 104 can distinguish the same points of the periodic pattern W1 captured by each of the imaging units 103, 103. In addition, it is possible to perform three-dimensional measurement using an image with little texture and three-dimensional measurement in a dark area, which have been problems in the passive stereo method. By using the periodic pattern W1 represented by periodic dots, bias in the pattern density of the measurement light 105 is suppressed, and it is possible to suppress unevenness in the measurement accuracy due to the illumination position of the measurement light 105.

[0074] In this embodiment, instead of the periodic pattern W1, for example, a random dot pattern W2 as shown in Fig. 18 may be used. The random dot pattern W2 is a pattern in which each dot of the dot pattern shown in Fig. 16 is two-dimensionally randomly shifted from the position of the lattice point within the range of a basic periodic area (a rectangular area surrounded by line segments perpendicular to the midpoint between adjacent lattice points). As an example, a random number φ(ix, iy) may be assigned to each dot located at a lattice point, and each dot may be shifted from the position of the lattice point based on the random number φ.

[0075] In this case, since the random dot pattern W2 has pseudo-periodicity, bias in the pattern density of the measurement light 105 is suppressed, and it is possible to suppress unevenness in the measurement accuracy due to the illumination position of the measurement light 105. Furthermore, by using the random dot pattern W2 instead of a periodic dot pattern, it is possible to suppress erroneous recognition when the same point of the dot pattern is imaged by different imaging units 103. Therefore, it is possible to improve the measurement accuracy of the parallax D and increase the accuracy of the three-dimensional shape measurement.

[0076] In addition, in this embodiment, instead of the periodic pattern W1, a pattern W3 having a uniform density as shown in FIG. 19 may be used. Since the light emitted from the S-iPMSEL1 is a laser light, speckles may occur in the scattered light. In addition, in phase calculation, unintended speckle-like noise may be mixed in. Therefore, even when the pattern W3 having a uniform density is used, a random dot pattern is formed in the pattern of the measurement light 105. By using this random dot pattern, it is possible to suppress erroneous recognition when the same point of the dot pattern is imaged by different imaging units 103.

[0077] 20 is a diagram showing an example of a far field pattern (FFP) of a pattern W3 having a uniform density. In the example shown in the figure, the pulse width of the measurement light 105 is 50 ns, the repetition interval is 5 μs, and the FFP is observed at room temperature. In addition, color correction is performed with a brightness of +40% and a contrast of -40%. In the figure, it can be seen that a random dot pattern is formed in the pattern of the measurement light 105 even when the pattern W3 having a uniform density is used.

[0078] 15, the three-dimensional measuring apparatus 101A includes a single light source unit 102, but the three-dimensional measuring apparatus 101A may include multiple light source units 102. In this case, by irradiating different areas of the measurement object SA with the measuring light 105 from each light source unit 102, the measurement area can be expanded without scanning the stage 106. When this configuration is adopted, the arrangement of the stage 106 may be omitted. [Second embodiment of three-dimensional measuring device]

[0079] 21 is a schematic diagram showing the configuration of a three-dimensional measuring apparatus according to the second embodiment. As shown in the figure, a three-dimensional measuring apparatus 101B according to the second embodiment includes a plurality of light source units 102, a single imaging unit 103, and a measuring unit 104. The configurations of the imaging unit 103, the light source unit 102, and the measuring unit 104 are the same as those in the first embodiment. In this embodiment, the predetermined pattern of the measuring light 105 is a Gray code pattern, and the measuring unit 104 measures the three-dimensional shape of the measurement object SA based on a triangulation method using the Gray code pattern.

[0080] FIG. 22 is a diagram showing an example of a Gray code pattern. In the example of the figure, the pixels of the imaging unit 103 are Nx×Ny, and are shown in the X direction. If the pixel position n (n is an integer from 0 to Nx-1) in the X direction is a binary number of Mx digits, the Gray code pattern W4 is expressed by the exclusive OR of the binary expression of the target number and the number obtained by shifting the binary expression of the target number one bit to the right and adding 0 to the beginning of the binary expression. In other words, if the number of targets is n, the Gray code pattern W4 is given by the logical expression n^(n>>1). In the example of FIG. 22, Gray code patterns W4a to W4d in the case of 4 bits (4 patterns) are shown. For example, OpenCV or the like can be used to generate the Gray code pattern W4.

[0081] In Gray code, the Hamming distance between adjacent pixels is 1. Hamming distance refers to the number of different digits in corresponding positions when comparing two values ​​with the same number of digits. Therefore, in Gray code, which has a Hamming distance of 1, even if a bit error occurs when restoring the bit string, the error is contained to 1. In simple binary code, if an error occurs in the upper bit, the position error becomes large, but Gray code produces a code that is resistant to noise.

[0082] When using the Gray code, the number of light source units 102 may be the number of patterns corresponding to each digit of the binary number. That is, the Gray code patterns W4a to W4d are configured by a plurality of stripe patterns in which the 0s and 1s of each pixel of each digit from the most significant bit to the least significant bit are set to be different from each other. When the imaging unit 103 captures images while sequentially switching between the Gray code pattern W4a of the most significant bit to the Gray code pattern W4d of the least significant bit in the light source unit 102, a value X is obtained by capturing Mx images. It can be seen that the position of the Xth pixel is measured based on this value X. Similarly, in the Y direction, the Gray code patterns W4a to W4d are sequentially switched while capturing images in the imaging unit 103, and a value Y is obtained by capturing My images. It can be seen that the position of the Yth pixel is measured based on this value Y.

[0083] In order to avoid erroneous recognition due to the color of the surface of the object to be measured SA, a gray code pattern in which black and white are inverted may be used in addition to the gray code patterns W4a to W4d shown in Fig. 22. In this case, the number of light source units 102 to be arranged may be 2Mx+2My.

[0084] In this embodiment, instead of the Gray code pattern W4, a sinusoidal stripe pattern W5 may be used, for example, as shown in FIG. 23. The sinusoidal stripe pattern W5 shown in FIG. 23 is a periodic stripe pattern shown in an image area of ​​100×100 pixels. The period of the sinusoidal stripe pattern W5 is a 20-pixel period. The measurement unit 104 measures the three-dimensional shape of the measurement object SA based on a phase shift method using the sinusoidal stripe pattern W5. In this embodiment, for example, a plurality of sinusoidal stripe patterns W5 are used, each of which is given a phase shift (positional deviation) that is an equal division of one period of the grating pitch. The phase shift pattern may be prepared with a phase shift of 2π / N (N is an integer).

[0085] Here, an example is shown in which four sinusoidal stripe patterns W5 having different phase shifts are used. If the light intensities of the measurement light 105 having the four sinusoidal stripe patterns W5 are I0 to I3, respectively, and the pixels of the imaging unit 103 are (x, y), the light intensities I0 to I3 on ​​the surface of the measurement object SA are expressed by the following formulas (30) to (33). Ia(x, y) is the amplitude of the lattice pattern, Ib(x, y) is the background intensity, and θ(x, y) is the initial phase.

number

number

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[0086] The initial phase θ can be calculated by tan θ=-(I3-I1) / (I2-I0). When the phase shift number of the sinusoidal stripe pattern W5 is N, the initial phase θ can be calculated by the following formula (34).

number

[0087] When such a phase shift method is used, the measured phase is converted into height, so that the height of the measurement object SA can be measured at intervals smaller than the pitch of the sinusoidal stripe pattern W5. In configuring the three-dimensional measuring device 101B, the light source unit 102 may be arranged in a direction parallel to the stripes in the sinusoidal stripe pattern W5. In this case, it is possible to eliminate the phase shift caused by the positional deviation of the light source unit 102, and the deviation of the initial phase in each of the plurality of sinusoidal stripe patterns W5 can be eliminated.

[0088] In this embodiment, the light source units 102 may be arranged in two mutually orthogonal axial directions. In this case, the height profile of the object SA can be acquired in two axes by switching the measurement light 105 on and off for each axis. Also, instead of the sinusoidal stripe pattern W5, a matrix pattern W6 that changes sinusoidally in the two mutually orthogonal axial directions may be used, for example, as shown in FIG. 24. When such a matrix pattern W6 is used, the height profile of the object SA can be measured in two axial directions simultaneously.

[0089] In this embodiment, the light source units 102 may output sinusoidal stripe patterns W5 having different periods. In the above-mentioned phase shift method, discontinuity at phase 2π is an issue. In contrast, when using sinusoidal stripe patterns W5 having different periods, as shown in FIG. 25, for example, by selecting coordinates that match at all frequencies, it is possible to improve the discontinuity at phase 2π, and high-precision three-dimensional measurement can be realized with a small number of patterns. By improving the discontinuity at phase 2π, it is possible to expand the measurement range of three-dimensional shape measurement and to achieve high-precision measurement of a measurement target SA with significant unevenness.

[0090] In this embodiment, the measuring unit 104 may measure the three-dimensional shape of the measurement object SA based on a sampling moiré method using a sine wave stripe pattern W5. The sampling moiré method utilizes the fact that the grid of the sine wave stripe pattern W5 projected on the surface of the measurement object SA deforms according to the height of the measurement object SA. Here, in an image captured by the imaging unit 103, the fringe interval of one sine wave pattern with a phase shift number N at the height of the reference plane is adjusted in advance so as to correspond to N pixels of the camera. Here, the phase shift number N is set to 4. By irradiating one sine wave pattern and sampling the pixels of the imaging unit 103 every N=4 pixels, four patterns P1 to P4 captured every 4 pixels (3 pixels between the captured pixels are thinned out) are obtained as shown in FIG. 26(a). Between these patterns P1 to P4, the captured pixels are shifted by one pixel, and by linearly complementing the luminance values ​​of the captured pixels, moiré fringe patterns M1 to M4 with mutually shifted phases are obtained as shown in FIG. 26(b). By applying the above-mentioned phase shift method using these moire fringe patterns M1 to M4, it is possible to measure the height of the measurement object SA at intervals smaller than the pitch of the sinusoidal stripe pattern W5. According to this method, the number of sinusoidal patterns to be irradiated can be reduced compared to the above-mentioned phase shift method, and the light source unit 102 can be made compact.

[0091] In this embodiment, instead of the sinusoidal stripe pattern W5, a superimposed pattern W7 in which a sinusoidal stripe pattern W5 and a random dot pattern W2 are superimposed may be used, as shown in FIG. 27. By using such a superimposed pattern W7, the height of the measurement object SA can be measured at intervals smaller than the pitch of the sinusoidal stripe pattern W5. In addition, by combining a random dot pattern, it is possible to improve discontinuity at the phase 2π, and a high-precision three-dimensional measurement can be realized with a small number of patterns. The superimposed pattern may be a superimposed pattern W8 in which a sinusoidally changing matrix pattern W6 and a random dot pattern W2 are superimposed, as shown in FIG. 28. In this case, in addition to the above-mentioned effects, the height profile of the measurement object SA can be measured simultaneously in two axial directions.

[0092] In this embodiment, both the sinusoidal stripe pattern W5 and the Gray code pattern W4 may be used. In this case, the measurement unit 104 measures the three-dimensional shape of the measurement target SA based on the phase shift method using the sinusoidal stripe pattern W5 and the triangulation method using the Gray code pattern W4. In this case, pixel-level measurement can be performed by the triangulation method using the Gray code pattern W4, and sub-pixel-level measurement can be performed by the phase shift method using the sinusoidal stripe pattern W5. In addition, by using the Gray code, it is possible to improve discontinuity at the phase 2π, and high-precision three-dimensional measurement can be realized with a small number of patterns. [Third embodiment of three-dimensional measuring device]

[0093] 29 is a schematic diagram showing the configuration of a three-dimensional measuring apparatus according to the third embodiment. As shown in the figure, a three-dimensional measuring apparatus 101C according to the third embodiment includes a plurality of light source units 102, a plurality (pairs) of imaging units 103, and a measuring unit 104. The configurations of the imaging unit 103, the light source unit 102, and the measuring unit 104 are the same as those in the first embodiment. In this embodiment, the predetermined pattern of the measuring light 105 is a sinusoidal stripe pattern W5, and the measuring unit 104 measures the three-dimensional shape of the measurement object SA based on the phase shift method and the active stereo method using the sinusoidal stripe pattern W5.

[0094] In this embodiment, the height of the measurement object SA can be measured at intervals smaller than the pitch of the sinusoidal stripe pattern W5 by converting the measured phase into height. In addition, by combining an active stereo method using multiple image capturing units 103, it is possible to improve discontinuity at the phase 2π, and highly accurate three-dimensional measurement can be achieved with a small number of patterns. When using the active stereo method, the above-mentioned dot patterns may be used while being switched. [Phase shift of sinusoidal stripe pattern by S-iPMSEL]

[0095] In the S-iPMSEL1, in addition to the designed 1st order light, -1st order light symmetrical with respect to the normal to the emission surface is output (see FIG. 6). For this reason, when shifting the phase of the sine wave stripe pattern W5, if a sine wave in which ±1st order light overlaps is considered, the direction in which the stripes shift between the 1st order light and the -1st order light may be reversed, and the pattern may deviate from the design. For the sake of simplicity, if the shift of the stripes in the X-axis direction is considered, the complex amplitude of the 1st order light is expressed by the following formula (35). The complex amplitude of the -1st order light is output at a position symmetrical to the 1st order light with respect to the surface normal, and is expressed by the following formula (36). In the formula, k (= kx, ky, kz) is the wave vector (magnitude 2π / λ), λ is the wavelength, ω is each frequency of light, Δθ is the phase shift, a1 is the first-order light amplitude (the component resulting from the phase distribution of the actual hole arrangement compared to the ideal phase distribution), K is the wave number of the sinusoidal fringes (= 2π / Λ (Λ is the period of the sine wave)), θ is the amount of phase shift of the sine wave, and (x, y, z) are the coordinates of the projected beam.

number

number

[0096] At this time, the composite amplitude A can be calculated based on the amplitudes of the 1st order light and the −1st order light by the following formula (37).

number

number

number

[0097] From these formulas, it can be seen that when the phase shift of the sinusoidal stripe pattern W5 is performed, the stripes are shifted while maintaining the sinusoidal shape even if ±1st order light is superimposed. Also, in a sinusoidal pattern in which ±1st order light is superimposed, the stripe spacing of the light intensity (the square of the sum of the amplitudes of ±1st order light) actually obtained with respect to the design pattern (1st order light amplitude) is halved, and the phase shift amount is doubled for one period. Therefore, for example, to realize a phase shift of π / 2 in the finally obtained light intensity, the design value of the phase shift amount of the 1st order light amplitude should be π / 4. The same is true for the sinusoidal matrix pattern W6 having a period in the two axial directions.

[0098] As shown in Fig. 4, when the modified refractive index area 15b in the S-iPMSEL1 is formed by shifting the center of gravity G of the modified refractive index area 15b in the circumferential direction around the lattice point O, the amplitudes a of the 1st order light and the -1st order light are equal to each other. On the other hand, as shown in Fig. 14, when the modified refractive index area 15b in the S-iPMSEL1 is formed by shifting the center of gravity G onto a straight line D that passes through the lattice point O and is inclined with respect to each side of the square lattice, the amplitudes a of the 1st order light and the -1st order light are different from each other. In either case, a sine wave pattern in which ±1st order light are superimposed can be used.

[0099] In the case where the 1st and -1st light are asymmetrical patterns, there is a problem that the designed pattern cannot be obtained if the 1st and -1st light overlap. One example of such a problem is that the structure per bright spot of the 1st light has an asymmetrical spread, making the designed pattern unclear. In this case, the emission area of ​​the 1st light may be limited to an area where the solid angle is π. For example, when the emission area of ​​the 1st light is limited to the first and second quadrants, the emission area of ​​the -1st light is the fourth and third quadrants, so that the 1st light and the -1st light can be prevented from overlapping. This makes it possible to suppress the spread of the bright spot caused by the overlap of the 1st light and the -1st light. When the grating pattern is shifted by the phase shift method, the shift direction of the -1st light is reversed to the shift direction of the 1st light. Therefore, it is preferable to reverse the phase obtained by the phase shift calculation according to the emission areas of the 1st light and the -1st light. On the other hand, even if the above problem does not occur, if an image with less noise can be obtained without superimposing the 1st order light and the -1st order light, the projection areas of the ±1st order light may be used without superimposing them. [Example of light source and imaging unit layout]

[0100] Fig. 30 is a schematic perspective view showing an example of the arrangement of the light source unit and the imaging unit. As shown in Fig. 30, in constructing the three-dimensional measuring device 101, the light source unit 102 and the imaging unit 103 may be arranged on the surface of a three-dimensional object 111. The three-dimensional object 111 constitutes a portion corresponding to the probe of the three-dimensional measuring devices 101A to 101C. The three-dimensional object 111 is formed in a cylindrical shape from, for example, metal or resin. The three-dimensional object 111 may be rigid or flexible. The three-dimensional object 111 may have an internal space.

[0101] The light source unit 102 and the imaging unit 103 are arranged at a constant interval (here, a phase angle of 45°) in the circumferential direction on the peripheral surface 111a of the cylindrical three-dimensional object 111. In the example of FIG. 30, a group of one imaging unit 103, a group of light source units 102, and a group of the other imaging unit 103 are arranged at a constant interval from the tip side to the base end side of the three-dimensional object 111. When the three-dimensional object 111 is viewed in the longitudinal direction, the one imaging unit 103, the light source unit 102, and the other imaging unit 103 are arranged in a row, and these sets form one measurement area for the measurement object SA. When the three-dimensional object 111 has an internal space, wiring for the light source unit 102 and the imaging unit 103 may be accommodated in the internal space. The light source unit 102 and the imaging unit 103 do not necessarily have to be arranged at equal intervals. Furthermore, when the measurement range for the measurement object SA is covered, a single light source unit 102 and a single image capturing unit 103 may be disposed on the three-dimensional object 111 .

[0102] FIG. 31 is a schematic perspective view showing another arrangement example of the light source unit and the imaging unit. In the example of FIG. 31, the three-dimensional object 121 has a spherical shape and is provided, for example, at the tip of a cylindrical support unit 122. The light source unit 102 and the imaging unit 103 are arranged at a constant interval (here, a phase angle of 45°) in the longitude direction on the spherical surface 121a of the spherical three-dimensional object 121. One group of imaging units 103, a group of light source units 102, and a group of the other imaging units 103 are arranged at a constant interval in the latitude direction of the three-dimensional object 121. A set of one imaging unit 103, the light source unit 102, and the other imaging unit 103 arranged in the longitude direction of the three-dimensional object 121 constitutes one measurement area for the measured object SA. When the three-dimensional object 121 has an internal space, wiring for the light source unit 102 and the imaging unit 103 may be accommodated in the internal space. 30, the light source unit 102 and the image capturing unit 103 do not necessarily have to be spaced apart at equal intervals. In addition, when the measurement range of the measurement object SA is covered, a single light source unit 102 and a single image capturing unit 103 may be disposed on the three-dimensional object 121.

[0103] According to the above configuration, the three-dimensional objects 111, 121 on which the light source unit 102 and the imaging unit 103 are arranged can be configured as a probe of the three-dimensional measuring device 101. By using such three-dimensional objects 111, 121, each set of the light source unit 102 and the imaging unit 103 can be oriented in different directions, so that it is possible to perform three-dimensional shape measurement of the measurement object SA over a wide solid angle. In addition, it is possible to apply the present invention to applications such as oral cavity examination, endoscopic examination, inspection of narrow places such as the inside of a tube or a gap in a wall, and inspection from under the floor of furniture, equipment, etc., and it is easy to construct a handy type three-dimensional measuring device.

[0104] In Fig. 23, a sinusoidal stripe pattern W5 is shown. In forming such a stripe pattern, it is important to reduce noise (brightness fluctuation) between adjacent patterns. The noise between adjacent patterns may cause position fluctuation when applying a phase shift method, for example, and may affect measurement accuracy. Therefore, in order to realize the formation of a stripe pattern taking into consideration noise reduction between adjacent patterns, a configuration may be adopted in which an S-iPMSEL1 that emits a one-dimensional multi-point pattern and a one-dimensional lens 51 are combined, as shown in Fig. 32, for example.

[0105] In the example of FIG. 32, the one-dimensional lens 51 is a one-dimensional concave lens 52. The medium of the one-dimensional concave lens 52 is, for example, glass. One surface 52a of the one-dimensional concave lens 52 is a flat surface, and the other surface 52b is a concave surface. The one-dimensional concave lens 52 is disposed with the one surface 52a facing the S-iPMSEL1, facing the surface (laser light emission surface) of the S-iPMSEL1. The one-dimensional concave lens 52 may be bonded to the surface of the S-iPMSEL1 and integrated with the S-iPMSEL1. The lens phase of the one-dimensional concave lens 52 is calculated by the following formula (40). In the following formula (40), φ is the lens phase, λ is the wavelength of the laser light in the lens medium, and f is the focal length.

number

[0106] In the examples of Fig. 32 and Fig. 33(a), the multi-point pattern laser light La from the S-iPMSEL1 is arranged at a predetermined interval in the X direction. In the example of Fig. 32, the one-dimensional concave lens 52 is arranged so that the concave surface extends in the X-axis direction. The multi-point pattern laser light La that has passed through the one-dimensional concave lens 52 does not change in the X-axis direction and expands only in the Y-axis direction. Therefore, by passing the multi-point pattern laser light La through the one-dimensional concave lens 52, a stripe pattern W11 is obtained in which the line-shaped laser light Lb expanded in the Y direction are lined up in the X-axis direction, as shown in Fig. 33(b).

[0107] When the stripe pattern is made closer to a sine wave, for example, as shown in Fig. 34(a), a multi-point pattern of laser light La is formed and the luminance of each laser light is controlled to be sinusoidal in the X-axis direction. By passing such a multi-point pattern of laser light La through a one-dimensional concave lens 52, in the stripe pattern W12 shown in Fig. 34(b), line-shaped laser light Lb expanded in the Y direction is aligned in the X-axis direction, and the luminance of each laser light Lb changes sinusoidally in the X-axis direction.

[0108] In Fig. 34(a) and Fig. 35(a), the laser beams La of the multi-point pattern are aligned in a straight line in the X-axis direction, but the laser beams La do not necessarily need to be aligned in a straight line, and may be shifted periodically or randomly in the Y-axis direction. The one-dimensional lens 51 is not limited to the one-dimensional concave lens 52 as long as it can expand the laser beams La of the multi-point pattern in a one-dimensional direction, and may be a Powell lens or a Lineman lens that functions as a line generator. The one-dimensional lens 51 may be a flat lens such as a Fresnel lens, a microlens, or a metalens.

[0109] When a metalens is used, for example, a resonant metalens structure 53A as shown in FIG. 35(a) may be employed, or a refractive index modulation metalens structure 53B as shown in FIG. 35(b) may be employed. As shown in FIG. 35(a), when a resonant metalens structure 53A is employed, the material constituting the metalens structure 53A is a material having a higher refractive index than the underlying layer. For example, when the underlying layer (e.g., anti-reflection film 19) is SiN, amorphous silicon can be used as the material constituting the metalens structure 53A. The height and diameter of the unit cell constituting the metalens structure 53A are set based on the lens phase calculated by the above-mentioned equation (40).

[0110] 35(b), when a refractive index-modulated metalens structure 53B is adopted, the metalens structure 53B can be formed by etching the surface of the S-iPMSEL 1. For example, the refractive index-modulated metalens structure 53B can be formed by forming holes 54 by etching on the surface of the S-iPMSEL 1, the holes 54 extending from the outermost layer (e.g., anti-reflection film 19) to the layer below (e.g., semiconductor substrate 10). The depth and diameter of each hole 54 constituting the metalens structure 53B are set based on the lens phase calculated by equation (40) above. [Explanation of symbols]

[0111] 1...S-iPMSEL, 101 (101A to 101C)...three-dimensional measuring device, 102...light source unit, 103...imaging unit, 104...measurement unit, 105...measurement light, SA...measured object, W1...periodic pattern, W2...random dot pattern, W3...pattern having uniform density, W4...Gray code pattern, W5, W6...sine wave stripe pattern, W7, W8...superimposed pattern, W11, W12...sine wave stripe pattern, 111, 121...three-dimensional object.

Claims

1. A plurality of light source units each irradiating a measurement object with measurement light having a predetermined pattern for each light source unit; an imaging unit that images the object to be measured irradiated with the measurement light; a measurement unit that measures a three-dimensional shape of the measurement object based on an imaging result by the imaging unit, the predetermined pattern of the measurement light includes a stripe pattern, and the stripe patterns of the measurement light irradiated from the plurality of light source units each have a different pattern, the plurality of light source units are arranged in a direction parallel to the stripes of the stripe pattern, the measurement unit measures a three-dimensional shape of the object based on a three-dimensional shape measurement method using the stripe pattern, A three-dimensional measuring device, wherein each of the plurality of light source units is composed of a SiPMSEL.

2. The three-dimensional measuring device according to claim 1 , wherein the SiPMSEL is an M-point oscillation SiPMSEL.

3. the predetermined pattern of the measurement light is a superimposed pattern in which the periodic stripe pattern and a random dot pattern are superimposed, 3. The three-dimensional measuring apparatus according to claim 1, wherein the measurement unit measures the three-dimensional shape of the object based on a phase shift method using the superimposed pattern.

4. the stripe patterns of the measurement light irradiated from the plurality of light source units are gray code patterns including different gray codes, 3. The three-dimensional measuring apparatus according to claim 1, wherein the measurement unit measures the three-dimensional shape of the object based on a triangulation method using the Gray code pattern.

5. the stripe patterns of the measurement light irradiated from the plurality of light source units are periodic stripe patterns each having a different phase shift, 3. The three-dimensional measuring apparatus according to claim 1, wherein the measuring unit measures the three-dimensional shape of the object based on a phase shift method using the stripe pattern.

6. 6. The three-dimensional measuring apparatus according to claim 5, wherein the stripe pattern is a sine wave stripe pattern.

7. 7. The three-dimensional measuring apparatus according to claim 5, wherein the phases of the stripe patterns of the measuring light irradiated from the plurality of light source units are shifted by 2.pi. / N (N is a phase shift number of the stripe pattern).

8. A light source device used in a three-dimensional measuring device that measures a three-dimensional shape of a measurement object based on a three-dimensional shape measurement method using a stripe pattern, A plurality of light source units are provided, each of which irradiates a measurement object with measurement light having a predetermined pattern for each light source unit; the predetermined pattern of the measurement light includes the stripe pattern, and the stripe patterns of the measurement light irradiated from the plurality of light source units each have a different pattern, the plurality of light source units are arranged in a direction parallel to the stripes of the stripe pattern, A light source device, wherein each of the plurality of light source units is constituted by a SiPMSEL.

9. The light source device according to claim 8, wherein the S-iPMSEL is an M-point oscillation S-iPMSEL.

Images