IMAGE SCANNING DEVICE

Abstract

An image scanning device (1) comprises an illumination device (10) having a light source emitting an optical beam and an illumination optical system that scans a linear illumination region (13) extending linearly in a first direction (X) on a virtual reference surface (24) as an illumination region onto which the optical beam is projected, in a second direction (Y) as a direction orthogonal to the first direction (X), a camera (20) that performs a photographic process of scanning a linear image pickup region (23), which is a region extending linearly in the first direction (X) on the reference surface (24), in the second direction (Y), and a control circuit (30) that controls the operation of the illumination device (10, 50, 60) and the photographic process of the camera (20).so that the linear illumination region (13) and the linear image recording region (23) continue to overlap on the reference surface (24). An optical axis (11) of the illumination device (10) and an optical axis (21) of the camera (20) are not parallel to each other and intersect on the reference surface (24).

Description

TECHNICAL FIELD

[0001] The present invention relates to an image scanning device. STATE OF THE ART

[0002] An image scanning device composed of a projector, a camera, and a synchronizing circuit is known, which obtains an image of a target object by epipolar photography (see, for example, Patent Reference 1). The projector is an illumination device that scans a light spot, which is an illumination area formed by a laser beam, in the horizontal and vertical directions. The camera is, for example, a rolling shutter camera and a photographic device that scans a photographic area in the horizontal and vertical directions. The camera and the projector are arranged so that they are adjacent to each other in the X direction, and the optical axis of the camera axis and the optical axis of the projector are parallel to each other. The synchronizing circuit controls the operation of the projector and the camera so that an illumination area of ​​the projector and a photographic area of ​​the camera coincide with each other.

[0003] By using epipolar photography, photographing an object that causes strong reflection scattering (e.g., a metallic object with luster) can be performed in a state where reflected scattered light (e.g., reflected stray light) is suppressed, and three-dimensional measurement with a reduced error is enabled (see, for example, non-patent reference 1). LITERATURE ON THE STATE OF THE ART PATENT REFERENCE

[0004] Patent Reference 1: US Patent No. 10359277 NON-PATENT REFERENCE

[0005] Non-Patent Reference 1: Matthew O'Toole et al., “Homogeneous Codes for Energy-Efficient Illumination and Imaging,” ACM SIGGRAPH, 2015 SUMMARY OF THE INVENTION OBJECT

[0006] However, in the devices described in the above references, the camera and projector must be arranged so that an optical axis of the camera and an optical axis of the projector are parallel to each other to perform epipolar imaging. In this case, the problem is that a scanning area, which is the overlap area between an illuminable area of ​​the projector and a photographable area of ​​the camera, is narrow.

[0007] An object of the present invention is to provide an image scanning device having a wide scanning range. MEANS TO SOLVE THE TASK

[0008] An image scanning apparatus according to the present invention comprises an illumination device including a light source that emits an optical beam and an illumination optical system that scans a linear illumination region that extends linearly in a first direction on a virtual reference surface as an illumination region onto which the optical beam is projected, in a second direction as a direction orthogonal to the first direction; a camera that performs a photographic operation of scanning a linear image pickup region that is an image pickup region that extends linearly in the first direction on the reference surface in the second direction; and a control circuit that controls the operation of the illumination device and the photographic operation of the camera such that the linear illumination region and the linear image pickup region on the reference surface continue to overlap with each other.An optical axis of the illumination device and an optical axis of the camera are not parallel to each other and intersect on the reference surface. EFFECT OF THE INVENTION

[0009] According to the present invention, the scanning range can be widened. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view schematically showing a main configuration of an image sensing apparatus according to a first embodiment. Fig. 2 is a plan view schematically showing the main configuration of the image sensing device in Fig. 1 shows. Fig. 3 is a perspective view schematically showing a main configuration of a laser scanner in Fig. 1 shows. Fig. Figure 4 is a plan view schematically showing the main configuration of the laser scanner in Fig. 1 shows. Fig. 5 is a side view schematically showing the main configuration of the laser scanner in Fig. 1 shows. Fig. 6(A) is a diagram showing the operation of an image sensing device in a comparative example (in a case where the device does not include a trapezoidal distortion generating element), and the Fig. 6(B) to 6(E) are diagrams showing the operation of the image sensing device in Fig. Show 1. Fig. 7 is a plan view showing the operation of a camera in Fig. 1 shows. Fig. 8 is a plan view showing the operation of the laser scanner in Fig. 1 shows. Fig. 9 is a plan view showing the operation of the camera and laser scanner in Fig. 1 shows. Fig. 10 is a plan view schematically showing a main configuration of an image sensing apparatus according to a modification of the first embodiment. Fig. 11 is a perspective view schematically showing a main configuration of an image scanning device in a comparative example (in a case where an optical axis of the camera and an optical axis of the laser scanner are parallel to each other). Fig. 12 is a plan view schematically showing the main configuration of the image sensing device in Fig. 11 shows. Fig. 13(A) to 13(C) are diagrams showing the operation of the image sensing device in Fig. Show 11. Fig. 14 is a schematic plan view showing a main configuration of an image scanning device in a comparative example (in a case where the optical axis of the laser scanner is inclined with respect to the optical axis of the camera). The Fig. 15(A) to 15(C) are diagrams showing the operation of the image sensing device in Fig. 14 (in the case where the optical axis of the laser scanner is tilted). Fig. 16 is a perspective view schematically showing a main configuration of a laser scanner of an image scanning apparatus according to a second embodiment. Fig. 17 is a plan view schematically showing the main configuration of the laser scanner in Fig. 16 shows. Fig. 18 is a side view schematically showing the main configuration of the laser scanner in Fig. 16 shows. Fig. 19 is a schematic plan view showing a main configuration of the image sensing apparatus according to the second embodiment. Fig. 20(A) and Fig. 20(B) are diagrams showing the operation of the image sensing apparatus according to the second embodiment. Fig. 21(A) and Fig. 21(B) are diagrams showing angular functions of galvanometer mirrors of the image pickup device according to the second embodiment. Fig. 22(A) to 22(C) are diagrams showing the angular functions of the galvanometer mirrors for correcting distortions on an illumination reference surface in the image sensing apparatus according to the second embodiment. Fig. 23(A) to 23(C) are diagrams showing the angular functions of the galvanometer mirrors for correcting distortions on an image pickup reference surface in the image pickup apparatus according to the second embodiment. Fig. 24 is a perspective view schematically showing a main configuration of a laser scanner of an image scanning apparatus according to a third embodiment. Fig. 25 is a plan view schematically showing the main configuration of the laser scanner in Fig. 24 shows. Fig. 26 is a side view schematically showing the main configuration of the laser scanner in Fig. 24 shows. Fig. 27 is a diagram for explaining distortion on the illumination reference surface in an image sensing apparatus in a comparative example (in a case where the apparatus does not include a lens for generating trapezoidal distortion). Fig. 28 is a diagram for explaining the distortion on the image pickup reference surface in the image pickup apparatus in the comparative example (in the case where the apparatus does not include a lens for generating trapezoidal distortion). Fig. 29 is a diagram showing the location of the beam on the illumination reference surface in the image sensing apparatus according to the third embodiment. Fig. 30 is a diagram showing the location of the beam on the image pickup reference surface in the image pickup apparatus according to the third embodiment. Fig. 31 is a perspective view schematically showing a main configuration of a laser scanner including a free-form surface lens in the image scanning apparatus according to the third embodiment. Fig. 32 is a side view schematically showing the main configuration of the laser scanner in Fig. 31 shows. Fig. 33 is a plan view schematically showing the main configuration of the laser scanner in Fig. 31 shows. Fig. 34 is a diagram showing cross-sectional profiles of a first surface and a second surface of the free-form surface lens of the image sensing device according to the third embodiment. Fig. 35 is a diagram showing cross-sectional profiles of the first surface and the second surface of the free-form surface lens of the image sensing device according to the third embodiment. Fig. 36 is a diagram showing the locus of the laser beam on the image pickup reference surface obtained by controlling a slow wave of a two-dimensional MEMS mirror of the image pickup device according to the third embodiment. Fig. Figure 37 is a diagram showing a stripe pattern produced when the laser beam is switched on and off at regular intervals. Fig. Figure 38 is a diagram showing a vertical stripe pattern produced by controlling the on and off times of the laser beam. Fig. 39 is a schematic plan view showing a main configuration of an image sensing apparatus according to a fourth embodiment. EMBODIMENT OF THE INVENTION

[0010] Image sensing devices according to embodiments will be described below with reference to the drawings. The following embodiments are only examples, and it is possible to combine embodiments as appropriate and modify each embodiment as appropriate. In the drawings, components with the same or similar functions are denoted by the same reference numerals. (1) First Embodiment(1-1) Configuration

[0011] Fig. 1 and Fig. 2 is a perspective view and a plan view schematically showing a main configuration of an image scanning device 1 according to a first embodiment. The image scanning device 1 is a device that performs epipolar imaging. The image scanning device 1 includes a camera 20 as an image pickup device, a laser scanner 10 as an illumination device, a control circuit 30 including a synchronizing circuit, and a trapezoidal distortion generating element 40. The camera 20 and the laser scanner 10 are arranged side by side in an X direction, and an optical axis 21 of the camera 20 and an optical axis 11 of the laser scanner 10 are not parallel to each other and intersect at a position in front of the camera 20 and the laser scanner 10. In the first embodiment, the trapezoidal distortion generating element 40 is inserted in front of the laser scanner 10.

[0012] An image pickup reference surface 24 (also referred to as an "image pickup screen"), which is a planar virtual screen orthogonal to the optical axis 21 of the camera 20, is set at a position separated from the camera 20 by a certain distance Z0. Further, an illumination reference surface 14 (also referred to as an "illumination screen"), which is a planar virtual screen orthogonal to the optical axis of the laser scanner 10 and is a laser projection reference surface inclined at an angle θ with respect to the image pickup reference surface 24, is set. The image pickup reference surface 24 and the illumination reference surface 14 are not physical entities but represent virtual planes for explanation. Incidentally, the optical axis 21 of the camera 20 and the optical axis 11 of the laser scanner 10 intersect on the illumination reference surface 14 as a virtual reference surface.

[0013] Fig. 3 to Fig. 5 are a perspective view, a top view and a side view schematically showing the configuration of the laser scanner 10 in Fig. 1. A laser beam (also referred to as an "expanding beam") that expands fan-shaped in the X direction as the first direction is emitted from the laser scanner 10. On the illumination reference surface 14, the laser beam forms a linear illumination region 13, which is an expanded laser beam extending in the X direction (i.e., a linear beam with a linear cross-section).

[0014] The laser scanner 10 includes a laser light source 110 as a light source that emits a laser beam as an optical beam, and an illumination optical system that scans the linear illumination region 13 in a Y direction as a second direction orthogonal to the X direction. The linear illumination region 13 extends linearly in the X direction on the illumination reference surface 14 as an illumination region onto which the laser beam is projected and as a virtual reference surface. The laser beam is emitted from the laser light source 110, reflected by a mirror 111, and then forms the linear illumination region 13 as a linear beam extending in the X direction by means of an optical beam expanding element 112, which is a lens. The optical element for beam expanding 112 is an optical lens, for example, a cylindrical lens or a Powell lens. As shown in Fig. 5, the linear illumination region 13 is deflected in the Z direction by a galvanometer mirror 113 as an optical scanning unit. The galvanometer mirror 113 can oscillate around an X-axis within a predetermined angular range ±(α / 2), whereby the linear illumination region 13 is scanned around the X-axis within an angular range ±α that is twice as large as the predetermined angular range (i.e., it is scanned within a range between a linear illumination region 13a and a linear illumination region 13c in Fig. 5). On the image recording reference surface 24, the linear illumination area 13 is scanned in the Y direction and thus an area of ​​an entire laser scanning area 12 in Fig. 1 irradiated.

[0015] The camera 20 performs a photographic operation of scanning a linear image pickup area 23 in the Y direction. The linear image pickup area 23 is an image pickup area that extends linearly in the X direction on the image pickup direction surface 24. The control circuit 30 controls the operation of the laser scanner 10 and the photographing operation of the camera 20 such that the linear illumination area 13 and the linear image pickup area 23 on the image pickup direction surface 24 continue to overlap with each other. The control circuit 30 may be constituted by a memory in which a software program is stored and a processor. In this case, the function of the control circuit 30 is implemented by the processor executing the software program stored in the memory.

[0016] Fig. 6(A) is a diagram showing the operation of an image sensing device in a comparative example (in a case where the device does not include the trapezoidal distortion generating element). Fig. 6(A) shows the linear illumination region 13 on the illumination reference surface 14 of the image sensing device in the comparative example.

[0017] Fig. 6(B) to 6(E) are diagrams showing the operation of the image sensing device 1 in the first embodiment. Fig. 6(B) shows the linear illumination area 13 on the illumination reference surface 14, Fig. 6(C) shows the linear illumination area 13 on the image pickup reference surface 24 in the first embodiment, Fig. 6 (D) shows the linear image pickup area 23 on the image pickup reference surface 24 and Fig. 6(E) shows the linear illumination area 13 and the linear image pickup area 23 on the image pickup reference surface 24.

[0018] As in Fig. As shown in Fig. 6(A), in the image scanning device in the comparative example without the trapezoidal distortion generating element 40 on the illumination reference surface 14, the scanning of the linear illumination region 13 in the -Y direction is repeated at a speed VL in the entire laser scanning region 12 from its upper end to its lower end. At a time t = ta, the linear illumination region 13 exists as the linear illumination region 13a at the upper end of the entire laser scanning region 12. At a time t = tb, the linear illumination region 13 is specified as the linear illumination region 13b. At a time t = tc, the linear illumination region 13 exists as the linear illumination region 13c at the lower end of the entire laser scanning region 12. After reaching the lower end, the linear illumination region 13 returns to the upper end at high speed and repeats the above-described operation.

[0019] In the first embodiment, the entire laser scanning area 12 on the illumination reference surface 14 has a trapezoidal shape due to the presence of the trapezoidal distortion generating element 40, as shown in Fig. 6(B). Specifically, the linear illumination region 13a at time t = ta is a straight line rising to the right. The rotation of the linear illumination region 13 in an XY plane progresses with the progress of the scan in the -Y direction, and the linear illumination region 13c at the lower end is a straight line falling to the right. The reference surface 24 for capturing images, which is orthogonal to the optical axis 21, is inclined (inclined to approach the X direction) with respect to a plane orthogonal to the optical axis 11. The trapezoidal distortion generating element 40 has a function of making an extension direction of the linear illumination region 13 close to an extension direction of the linear image pickup region 23 on the illumination reference surface 14. On the image recording reference surface 24, the linear illumination area 13, which is parallel to the X-direction, is scanned from t = ta to t = tc, as shown in Fig. 6(C). While the trapezoidal distortion generating element 40 is designed to generate the Fig. 6(C), the concrete configuration of the trapezoidal distortion generating element 40 will be described later.

[0020] The camera 20 is a rolling shutter camera and is capable of repeating the operation of scanning the linear image pickup area extending in the X direction in the Y direction by shortening an exposure time. The scan of the image pickup area of ​​the camera 20 was performed in Fig. 13 and explained, for example, in non-patent reference 1. On the image recording reference surface 24, the image recording area 12 of the camera 20 is scanned from the upper end to the lower end of the entire image recording area 22 of the camera 20. The manner of scanning is described in Fig. 6(D). The linear image pickup area 23 of the camera 20 is scanned at a speed Vc from a linear image pickup area 23a at the upper end of the entire image pickup area 22 to a linear image pickup area 23c at the lower end of the entire image pickup area 22. In this case, the configuration of the device is previously set so that the linear image pickup area 23a of the camera 20 and the linear illumination area 13a overlap each other in the Y direction on the image pickup direction surface 24. The adjustment can be made by adjusting the zooming of the lens of the camera 20, the ROI (Region of Interest) that restricts an image pickup area of ​​the camera 20, a scanning range of the linear illumination area 13 in the Y direction, and the like. A device for finely adjusting the installation positions of the camera 20 and the laser scanner 10 is also important.

[0021] By the control circuit 30, an image pickup time of the linear image pickup area 23a and an irradiation time of the linear illumination area 13a are set to coincide with each other at t = ta. Further, the scanning speed Vc of the linear image pickup area 23 in the -Y direction and the scanning speed VL of the linear illumination area 13 in the -Y direction are set to coincide with each other. Then, as shown in Fig. As shown in Figure 6(E), the linear image pickup region 23 and the linear illumination region 13 are scanned from top to bottom during a cycle from time t = ta to time t = tc, with their positions in the Y direction constantly overlapping (preferably while constantly overlapping). The linear image pickup region 23 and the linear illumination region 13 are moved by repeating this cycle. An overlapping region of the entire image pickup region 22 and the entire laser scanning region 12 of the linear illumination region 13 is a region where epipolar imaging is possible.

[0022] It is important that the camera 20 and the laser scanner 10 are arranged next to each other in the X direction, i.e., the camera 20 and the laser scanner 10 are located at the same position coordinates in the Y direction and in the Z direction (condition A). This arrangement ensures that the linear illumination area 13 and the linear image acquisition area 23 continue to overlap, as shown in Fig. 6(E), regardless of the distance Z from the camera 20 to the image recording reference surface 24 in front of the camera 20. The reason for this is explained below using Fig. 7 to Fig. 9 described. Fig. 7 to Fig. 9 are diagrams for explaining the movement of the linear image pickup section of the image sensing device 1 according to the first embodiment and a line laser beam as a beam constituting the linear illumination section 13 in cross-sectional directions (in a YZ plane). In particular, Fig. 7 a plan view showing the operation of the camera in Fig. 1 shows, Fig. 8 is a plan view showing the operation of the laser scanner in Fig. 1 shows, and Fig. 9 is a plan view showing the operation of the camera and laser scanner in Fig. 1 shows.

[0023] Fig. 7 is a diagram showing the scanning range of the linear image pickup area 23 by the camera 20 projected onto the YZ plane. Fig. Figure 8 is a diagram showing the scanning range of the linear illumination area 13 projected onto the YZ plane by the laser scanner 10. Only when the above condition A is satisfied, the scanning areas in Fig. 7 and Fig. 8, and furthermore, the locations of the linear image pickup area 23b and the linear illumination area 13b on the YZ plane coincide at any time t = tb. The manner of the coincidence is shown in Fig. 9. Therefore, a scanning area 25 is defined as a wide area like that shown in Fig. 9 hatched area is formed and epipolar imaging is enabled at any position in the Z-direction. As can be seen from Fig. However, as can be seen in Figure 2, in an area where Z is small (an area extremely close to the camera), the image pickup area of ​​the camera 20 and the scanning area of ​​the linear illumination area 13 do not overlap on an XZ plane, so epipolar imaging cannot be performed. Incidentally, in Fig. 2 and Fig. 9, a distant portion of the scanning area 25 is delimited by the reference surface 24 for capturing images, with the scanning area 25 actually extending further than the reference surface 24 for capturing images. The actual boundary of the scanning area 25 is determined by the amount of detectable signals, since the amount of light received by the camera 20 decreases with increasing distance.

[0024] Specifically, the function of the trapezoidal distortion generating element 40 can be achieved by using a wedge-shaped prism. Patent Reference 2 shows an example in which the trapezoidal distortion of a projected pattern on a screen in the vertical direction is corrected by inserting a wedge-shaped prism onto a light-emitting surface of a projector that projects an image obliquely upward.

[0025] Patent Reference 2: Japanese Patent Application, Publication No. 2016-105179

[0026] Fig. Figure 10 is a diagram showing a configuration example of the image scanning device according to the first embodiment. The trapezoidal distortion in the horizontal direction is generated by inserting a wedge-shaped prism in front of the laser scanner 10. Fig. 10, the tip of the wedge-shaped prism 41 is located on the right side, and the optical axis 11 passing through the wedge-shaped prism 41 is deflected to the left. Here, the illumination reference surface 14 is perpendicular to the optical axis 11 after exiting the wedge-shaped prism 41. In addition, an angle formed by the optical axis 11 and a normal to the image pickup reference surface 24 is defined as θ. It is desirable to determine the shape, material, and installation angle of the wedge-shaped prism 41 and the installation angle of the laser scanner 10 so that the trapezoidal distortion in the horizontal direction on the image pickup reference surface 24 is eliminated, and all the linear illumination areas 13a to 13C on the image pickup reference surface 24 are parallel to the X-axis, as shown in Fig. 9 shown. (1-3) Comparison example

[0027] Fig. 11 and Fig. 12 shows a perspective view and a plan view schematically showing a main configuration of an image sensing device 1a in a comparative example that performs epipolar imaging. The image sensing device 1a in the comparative example is constituted by the camera 20, the laser scanner 10, and the control circuit 30. The camera 20 and the laser scanner 10 are arranged side by side in the X direction, and the optical axis 21 of the camera 20 and the optical axis 11 of the laser scanner 10 are parallel to each other and aligned in the Z direction. It is assumed that the reference surface 24 for capturing images as a virtual screen is arranged orthogonally to the optical axis 21 of the camera 20 at a position separated from the camera 20 by a certain distance Z0.

[0028] Fig. 13 (A) to 13 (C) are diagrams for explaining the operation of the image sensing device 1a in the comparative example which performs epipolar imaging. Fig. Figure 13 (A) shows the manner of scanning the linear image pickup area 23 on the image pickup reference surface 24 by the rolling shutter camera. This movement is the same as that previously described with respect to Fig. 6 (D) described movement.

[0029] Fig. 13(B) shows the movement of the linear illumination area 13 and Fig. 13(C) shows the state in which the linear image pickup area 23 and the linear illumination area 13 overlap each other.

[0030] Fig. 13(B) shows the manner of scanning the linear illumination area 13 on the image pickup reference surface 24 by the laser scanner 10. In the configuration in the Fig. 11 and Fig. 12, the reference surface 24 for capturing the image is orthogonal to the laser scanner 10, and therefore the linear illumination area 13 is formed from the linear illumination area 13a to the linear illumination area 13c parallel to the X direction similar to the example described previously with reference to Fig. 6(A) described case.

[0031] Similarly to the above, the synchronization of the camera 20 and the laser scanner 10 is established using the control circuit 30, and the image scanning device is operated so that the positions of the linear image pickup area 23 and the linear illumination area 13 in the Y direction on the image pickup reference surface 24 continue to overlap each other (preferably, constantly overlap each other). Fig. 13(C) shows the manner of overlapping the linear illumination area 13 and the linear image pickup area 23 on the image pickup reference surface 24. An overlapping area of ​​the two areas 13 and 23 on the image pickup reference surface 24 is smaller than that described above with respect to Fig. 6(E). In Fig. 12, the scanning area 25 is indicated as an overlapping area by hatching. If the scanning area 25 in Fig. 2 and the scanning area 25 in Fig. 12, it is clear that the image scanning device 101 in the comparative example has a problem in that the scanning range 25 in which epipolar imaging is possible is small. To enlarge the scanning range 25, it suffices to reduce the distance between the camera 20 and the laser scanner 10 while maintaining the parallelism of the optical axis 21 and the optical axis 11, but there is a limitation due to the size of the devices. As will be described later in the explanation of a second embodiment and a configuration example 2 in a third embodiment, a main application of epipolar imaging is 3D scanning by fringe pattern projection. Since the fringe pattern projection method uses the principle of triangulation, it is desirable to increase the distance between the laser scanner 10 and the camera 20 in the X direction in order to increase the measurement accuracy in the depth direction.However, in conventional epipolar imaging, the optical axis 21 and the optical axis 11 remain parallel to each other, and therefore there is a problem that the scanning area 25, the area in which 3D scanning is possible, is small.

[0032] Fig. 14 and Fig. 15(A) to 15(C) are diagrams for explaining the operation in a case where the optical axis of the laser scanner 10 is inclined in the image pickup device in the comparative example that performs the epipolar imaging. Fig. 14 is a main configuration diagram, Fig. 15(A) shows the movement of the linear illumination area 13 on the illumination reference surface 14, Fig. 15(B) shows the movement of the linear illumination area 13 on the reference surface 24 for taking pictures, and Fig. 15(C) shows the movement of the linear image pickup area 23 and the linear illumination area 13 overlapping each other on the reference surface 24 for picking up images.

[0033] If the optical axis 11 of the laser scanner 10 is inclined in the X direction, as in Fig. 1, in order to increase the width of the scanning area 25 in the X direction, the optical axis 21 and the optical axis 11 are not parallel to each other. Since the image pickup reference surface 24 orthogonal to the optical axis 21 of the camera 20 is inclined with respect to the optical axis 11, the linear illumination area 13 on the image pickup reference surface 24 is such that, for example, the linear illumination area 13a at the upper end is a straight line sloping to the right, as shown in Fig. 15(B), the rotation in the XY plane progresses with the progress of the scan, and the linear illumination area 13c at the lower end is a straight line rising to the right. On the other hand, the linear image pickup area on the image pickup reference surface 24 is scanned from top to bottom while maintaining parallelism, as shown in Fig. 13(A). Fig. 15(C) shows the manner of overlap of the linear image pickup area 23 and the linear illumination area 13 on the image pickup direction surface 24 when the control circuit 30 controls the positions of the linear image pickup area 23 and the linear illumination area 13 in the Y direction so that they coincide with each other on the image pickup direction surface 24. As can be seen from Fig. As can be seen from Fig. 15(C), it is impossible to scan the linear image pickup area 23 and the linear illumination area 13 while they overlap each other because the inclination of the linear illumination area 13 rotates on the image pickup direction surface 24. Although the linear image pickup area 23 and the linear illumination area 13 are parallel to each other only for a moment at an intermediate position in the Y direction, the scanning range in the Y direction is extremely narrow, and it is difficult to use the image pickup device as a sensor for epipolar imaging. (1-4) Effect

[0034] In the image scanning device 1 according to the first embodiment, the trapezoidal distortion generating element 40, which is appropriately set, is inserted in front of the laser scanner 10, which makes it possible to scan the line laser beam parallel to the X direction in the Y direction on the image pickup reference surface 24, which is inclined with respect to the optical axis 21. Accordingly, there are advantages in that epipolar imaging can be performed even when the optical axis 11 is inclined with respect to the optical axis 21, and thus the scanning area 25 can be enlarged.

[0035] Incidentally, the above description cited examples where the galvanometer mirror 113 is used as a beam scanning device, but the same advantages can also be achieved by using a one-dimensional MEMS (Micro Electromechanical Systems) mirror with a high-speed rotating oscillation function. It is also possible to use a scanner that rotates a polygon mirror as a polyhedral mirror with a motor instead of the galvanometer mirror 113. (2) Second Embodiment (2-1) Configuration

[0036] Fig. 16 is a perspective view schematically showing a main configuration of a laser scanner 50 as an illumination device of an image scanning apparatus 2 according to a second embodiment. Fig. 17 and Fig. 18 are a plan view and a side view schematically showing the main configuration of the laser scanner 50 in Fig. Show 16. Fig. Fig. 19 is a plan view schematically showing a main configuration of the image sensing device 2 according to the second embodiment. Here, the XYZ coordinate axes in Fig. 16 to Fig. 18 local coordinates of the laser scanner 50, and a Z-axis in Fig. 16 to Fig. 18 extends in the direction of the optical axis 11. The Z-direction in Fig. 19 and the Z-direction in Fig. 16 to Fig. 18 differ from each other. The second embodiment differs from the first embodiment in that the laser scanner 50 is formed by two galvanometer mirrors 511 and 512. A laser beam 90 emitted from a laser light source 510 travels in the Z-axis direction and is reflected by the galvanometer mirror 511 as the first optical scanning unit. The galvanometer mirror 511 can change the rotation angle θy of a mirror about a rotation axis at high speed within a range of ±10 degrees. As shown in Fig. As shown in Figure 18, the rotation axis is inclined by an angle θ1 with respect to the Y-axis.

[0037] The laser beam 90 reflected by the galvanometer mirror 511 reaches the galvanometer mirror 512 as the second optical scanning unit. Since the galvanometer mirror 511 reciprocates at high speed, the laser beam 90 reaching the galvanometer mirror 512 draws a curved locus that is convex upward, as indicated by reference character 93 in Fig. 16. The locus is formed not as a straight line, but as a curved line, since the light incident obliquely from above in the Y direction onto the galvanometer mirror 511 is scanned in the X direction. The galvanometer mirror 512 can change the rotation angle θx of a mirror about a rotation axis within a range of ±6 degrees, and the rotation axis is aligned in the X-axis direction. The position of the galvanometer mirror 512 at θx = 0 was determined such that an emission direction of the laser beam 90, namely the optical axis 11, is aligned in the Z-axis direction at θy = 0 and θx = 0. The laser beam 90 reflected by the galvanometer mirror 512 is the laser beam 90a in Fig. 18, when the galvanometer mirror 512 is at -6 degrees, and the laser beam is 90c in Fig. 18 when the galvanometer mirror 512 is at +6 degrees. (2-2) Operation

[0038] Fig. 20(A) and Fig. 20(B) and Fig. 21(A) and Fig. 21(B) are diagrams for explaining distortion on a screen in the image sensing apparatus 2 according to the second embodiment. Fig. 20(A) shows the geometric location of the laser beam on the illumination reference surface 14 and Fig. 20(B) shows the geometric location of the laser beam on the image pickup reference surface 24. Fig. 21(A) shows an angular function θx(t) of the galvanometer mirror 512 and Fig. Figure 21(B) shows an angular function θy(t) of the galvanometer mirror 511.

[0039] When the galvanometer mirror 511 is scanned back and forth at a constant high speed and the galvanometer mirror 512 repeats the operation of scanning from the direction of +6 degrees to the direction of -6 degrees at a constant speed, the laser beam 90 records on the illumination reference surface 14 in Fig. 19 a place indicated by an arrow with an upwardly convex curved line in Fig. 20(A). The laser beam 90 on the illumination reference surface 14 moves in a direction from -X to +X, as indicated by a solid arrow in a forward path, and moves in the opposite direction, as indicated by a dotted arrow in a reverse path. Since the galvanometer mirror 512 is scanned slowly compared to the galvanometer mirror 511, the linear illumination region 13 as the location of the laser beam moves on the entire screen in a direction from +Y to -Y. If the location of the laser beam in this one-way movement is photographed for a time longer than or equal to the time required for the one-way movement (that is, if the exposure time of the camera 20 is set sufficiently long), it can be considered that the illumination reference surface 14 is irradiated with a laser beam in the form of a curved line. Incidentally, the dots in Fig. 20(A) shows the arrival points of the laser beam on the illumination reference surface 14 when the rotation angles θx and θy of the galvanometer mirrors 511 and 512 are discretely changed in steps of 1 degree.

[0040] A geometric locus of the laser beam on the reference surface 24 for taking images, which is arranged to be orthogonal to the optical axis 21 but oblique to the optical axis 11, has a shape like an arrow with solid lines or an arrow with dashed lines in Fig. 20(B). Similar to the points in Fig. 20(A) give the points in Fig. 20(B) Arrival points of the laser beam on the image pickup reference surface 24 when the rotation angles θx and θy of the galvanometer mirrors 511 and 512 are discretely changed in steps of 1 degree. On the image pickup reference surface 24, the linear illumination region 13, which represents the location of the high-speed scan in the substantially horizontal direction, is not only convex in the Y direction but also undergoes a rotation of its overall inclination in the period from time t = ta to time t = tc, as shown by the linear illumination regions 13a to 13c in Fig. 20(B). Since such a distorted linear illumination area 13 cannot overlap with the linear image pickup area 23 of the camera 20, epipolar imaging cannot be performed.

[0041] Here in Fig. 21(A) and Fig. 21(B) shows simple illustrations of the angular functions of the galvanometer mirror 511 and the galvanometer mirror 512 forming, for example, a linear illumination region 13 in a time frame of an image. Fig. 21(A) and Fig. 21(B) show cases where the rotation angle θx of the galvanometer mirror 512 is indicated by step angles of 2 degrees and the rotation angle θy of the galvanometer mirror 511 changes only in the positive direction from -10 degrees to +10 degrees. The galvanometer mirror 512 in Fig. 21(A) performs an operation to maintain a constant angle during a scan time by the galvanometer mirror 511 (defined as a time Tx). However, in actual operation, where the step with respect to θx is finer, it is also possible for the galvanometer mirror 512 to change the angle slowly at a constant angular velocity during the movement from -6 degrees to +6 degrees. This is because the angle θx can be considered constant in the short time Tx. Fig. 21(B), the galvanometer mirror 511 performs an operation to change the angle θy at a constant speed during the time Tx.

[0042] The distortion is corrected by corrections to the trigonometric functions of the Fig. 21(A) and Fig. 21(B). In particular, correction functions for correcting the patterns of laser beam arrival positions in the areas indicated by the points in Fig. 20(A) and Fig. 20(B) are generated into square grid patterns at 1-degree angular intervals.

[0043] Fig. 22(A) to 22(C) and Fig. 23(A) to 23(C) are diagrams for explaining the distortion on the screen in the image sensing apparatus 2 according to the second embodiment. Fig. 22(A) and Fig. 22(B) show the angular functions of the galvanometer mirrors for correcting the distortion on the illumination reference surface 14, and Fig. 22(C) shows the location of the laser beam on the illumination reference surface 14. Fig. 23(A) and Fig. 23(B) show the angular functions of the galvanometer mirrors for correcting the distortion on the reference surface 24 on which the image is taken, and Fig. 23(C) shows the geometric location of the laser beam on the reference surface 24 on which the image is taken.

[0044] First, angular functions θy(t) and θx(t) are generated, which eliminate the distortion on the illumination reference surface 14. To obtain these functions, it is desirable to obtain a set of angles θy and θx of the two galvanometer mirrors at which the laser beam arrives at each grid point on the illumination reference surface 14, as shown in Fig. 22(C). The position coordinates (X, Y) on the illumination reference surface 14 are in a 1:1 correspondence with the two angles θy and θx. Thus, the angles θy and θx at which the laser beam arrives at the coordinate position (X, Y) are numerically determined with respect to a specific coordinate position (X, Y). For example, functions related to θy and θx such as those shown in the Fig. 22(A) and Fig. 22(B). In this example, for the convenience of illustration in the drawings, it is assumed that the function with respect to θy is a function in which the galvanometer mirror 511 moves at a constant angular velocity from -10 degrees to +10 degrees and then immediately returns to -10 degrees, and that the function with respect to θx is a function in which θx changes stepwise by about 2 degrees from about -6 degrees to about +6 degrees. Each step of the function with respect to θx is a curved line that is convex downward. In this case, a locus, which is a line segment parallel to the X-axis, is represented as the rightward arrow of the linear illumination area 13a in Fig. 22(C). In actual operation, even when the galvanometer mirror 511 returns from +10 degrees to -10 degrees, the laser beam is scanned by a similar control of the galvanometer mirror 512. It is also possible to change the angle θx in even finer steps. The geometric location of the laser beam in the return path is indicated by a dashed arrow pointing to the left in Fig. 22(C). Although the arrival positions of the laser beam on the illumination reference surface 14 when the set of θy and θx is swung in steps of 1 degree as shown in Fig. 20(A) are distorted as described above, the linear illumination area 13a is considered to be a location in Fig. 22(C) by using the functions in Fig. 22(A) and Fig. 22(B) to a straight line. Similarly, it is possible to generate a sequence of the sets of θy and θx that represents the square grid in Fig. 22(C) arranged points from top left to right.

[0045] However, on the image pickup reference surface 24, which is inclined with respect to the optical axis 11, the geometric location is not parallel to the X-axis, as indicated by the linear illumination areas 13a and 13c in Fig. 15(B), and epipolar imaging cannot be adequately implemented by this method alone. However, in this case, since the linear illumination area 13, which is horizontal and straight, is determined by the functions in Fig. 22(A) and Fig. 22(B), the linear illumination area 13, which is horizontal and straight, can be formed on the image pickup reference surface 24, and epipolar imaging is enabled by disposing the trapezoidal distortion generating element 40 in front of the laser scanner 50 as described in the first embodiment.

[0046] However, if the two galvanometer mirrors 511 and 512 are appropriately controlled, the linear illumination area 13 in the form of a straight line extending in the horizontal direction can be generated on the image pickup reference surface 24 without using the trapezoidal distortion generating element 40. To obtain the linear illumination area 13a by the horizontal laser beam scan on the reference surface 24 for image pickup, as shown in Fig. 23(C), it is sufficient to Fig. 23(A) and Fig. 23(B) to set the angle functions. Fig. 23(A) is a diagram in which the seven Fig. 22(A) have been assigned different rotations, respectively. As described above, in order to correct the trapezoidal distortion occurring on the image pickup reference surface 24, which is inclined with respect to the optical axis 11, it is necessary to generate a trapezoidal distortion in the opposite direction on the illumination reference surface 14, which is orthogonal to the optical axis 11. For this purpose, it is necessary to control θx while drawing a linear illumination area 13 and slightly change its control function line by line. Furthermore, the dot pattern narrows by the 1-degree steps in Fig. 20(B) the point spacing in the X direction gradually increases with increasing value of X. To correct the interval in the X direction, the set of seven straight line segments with a slope of increasing to the right in Fig. 22(B) into a set of slightly downward convex curved lines in Fig. 23(B). The linear illumination area 13, which is horizontal and straight in the X direction and in Fig. 23(C) is calculated from the functions in Fig. 23(A) and Fig. 23(B). The epipolar recording is made possible when the two galvanometer mirrors 511 and 512 are arranged in a plane parallel to each other by using functions such as those in Fig. 23(A) and Fig. 23(B). (2-3) Effect

[0047] In the second embodiment, when the epipolar imaging is performed by raster scanning the laser beam using two galvanometer mirrors 511 and 512, it is possible to perform scanning which was impossible by the epipolar imaging that scans the line laser beam in the vertical direction.

[0048] Furthermore, it is possible to create a vertical stripe pattern by repeating the switching on and off of the laser illumination at high speed. For example, the on / off control of the illumination is performed 100 times while the laser beam is in Fig. 23(C) is moved once from left to right or from right to left, and synchronization control is performed so that the illumination is turned on / off at the same position in the X direction in each line. Then, 100 vertical stripes appear extending in the vertical direction. By performing three-dimensional (3D) measurement using these vertical stripes, error-free scanning can be performed even on a metallic object. When 3D measurement is performed on a metallic object using the stripe pattern projection method, which is not the epipolar representation, false detection may be caused by a pseudo-pattern formed by the stripe pattern reflected by a metallic shiny surface.However, in epipolar imaging, the reflected pseudo-stripe pattern is not recorded by the camera, allowing 3D measurement without false detection. (3) Third Embodiment (3-1) Configuration

[0049] Fig. 24 to 26 show a perspective view, a plan view, and a side view schematically showing the configuration of a laser scanner 60 as an illumination device of an image scanning apparatus 3 according to a third embodiment. The laser scanner 60, which uses a two-dimensional MEMS mirror 620, is shown in Fig. 24 to 26. Since the two-dimensional MEMS mirror 620 is capable of performing the raster scan by deflecting the laser beam in the biaxial directions similar to the configuration with the two galvanometer mirrors, the two-dimensional MEMS mirror 620 can be used as a device for generating the linear illumination region 13 for the purpose of performing the epipolar imaging. The laser scanner 60 using the two-dimensional MEMS mirror 620 has the advantage of being downsized compared to the galvanometer mirrors and being inexpensive. Fig. 24 to 26, the laser beam 90 emitted by a laser light source 610 travels in the Z-axis direction and is reflected by a mirror 611 whose normal is tilted by an angle θ1 with respect to the Z-axis. The reflected light is further reflected by a mirror portion 621 of the two-dimensional MEMS mirror 620.

[0050] As in Fig. As shown in Figure 24, the two-dimensional MEMS mirror 620 is constituted by the mirror portion 621 that reflects the laser beam 90, a hinge 622 that rotates the mirror portion 621 by an angle θy around the Y-axis in the drawings, and a hinge 623 that rotates the mirror portion 621 by an angle θx around the X-axis. The optical axis 11 of the laser scanner 60 is defined in the direction of the laser beam 90 when θy = θx = 0, and the two-dimensional MEMS mirror 620 is installed so that its normal is inclined to form the angle θ1 with the Z-axis, so that the optical axis 11 is parallel to the +Z-axis.

[0051] The two-dimensional MEMS mirror 620 for raster scanning is generally formed by a high-speed shaft, which enables high-speed scanning but cannot be angle-controlled with high accuracy, and a low-speed shaft, which enables low-speed scanning but can be angle-controlled with high accuracy. High-precision control of the motion around the high-speed shaft is difficult because the scan is performed at high speed by setting the scanning frequency to a physical resonance frequency. The scanning angle θy around the high-speed shaft cannot be controlled by any function, and a reciprocating motion is repeated at a constant speed. Fig. 24 to 26, a rotating operation using the hinge 622 corresponds to rotating scanning around the high-speed shaft, and a rotating operation using the hinge 623 corresponds to rotating scanning around the low-speed shaft. By moving by θy, the laser beam is scanned at high speed in the X direction, and the linear illumination region 13 is formed. However, on the YZ plane, the laser beam 90 obliquely impinges on the mirror portion 621, and accordingly, the linear illumination region 13 obtained by rotating the mirror portion 621 around the high-speed shaft draws an arc in the Y-axis direction. (3-2) Configuration example 1 <Fall der Verhinderung von Verzerrung auf einem schrägen Schirm durch eine Freiform-Oberflächen-Linse>

[0052] Fig. 27 is a diagram for explaining the distortion on the illumination reference surface 14 in an image sensing apparatus in a comparative example (in a case where the apparatus does not include a lens for generating trapezoidal distortion). Fig. Fig. 28 is a diagram for explaining the distortion on the image pickup reference surface 24 in the image pickup device in the comparative example (in the case where the device does not include a lens for generating trapezoidal distortion). In contrast, Fig. 29 is a diagram showing the location of the beam on the illumination reference surface in the image sensing device 3 according to the third embodiment (the overall configuration is not shown). Fig. Fig. 30 is a diagram showing the location of the beam on the image pickup reference surface in the image scanning device 3 according to the third embodiment. The laser scanner 60 of the image scanning device according to the third embodiment is shown in Figs. Fig. 24 to 26.

[0053] Fig. 27 shows the linear illumination area 13 as the locus drawn by the laser beam 90 on the illumination reference surface 14 orthogonal to the optical axis 11 when no trapezoidal distortion generating element 40 is present. While the laser beam 90 has a locus similar to the locus on the illumination reference surface 14 in Fig. 20(A) in the case of using two galvanometer mirrors, the locus varies in Fig. 27 in the curvature of the arc depending on the position in the Y direction, and the radius of curvature decreases as the locus advances downward. Namely, the curvature of the arc of the linear illumination region 13c is larger than that of the linear illumination region 13a. In addition, the swing width in the X direction also decreases as the locus moves downward. This is because the joint 622 is located on the inner side of the joint 623 in the two-dimensional MEMS mirror 620, and the angle of incidence on the portion 621 of the mirror on the YZ plane changes to (θ1 + θx) according to the rotation angle θx by the joint 623. Incidentally, the points in Fig. 27 to Fig. 30 similar to the points in Fig. 20(A) shows the arrival points of the laser beam 90 on the illumination reference surface 14 when θx and θy are changed in 1-degree increments. For example, the points near the linear illumination range 13a as the upper end of the linear illumination range 13 are the arrival points of the laser beam when θy is swung from -5 degrees to +5 degrees while θx is fixed at -3 degrees.

[0054] Fig. Fig. 28 shows the arrival points of the laser beam and the linear illumination region 13 on the image pickup reference surface 24, which is set to be orthogonal to the optical axis 21 but oblique to the optical axis 11 when there is no trapezoidal distortion generating element 40, similar to the case of Fig. 20(B). In Fig. 28 is added to the Fig. 27, a trapezoidal distortion due to the obliqueness of the image pickup reference surface 24 is superimposed. Incidentally, this trapezoidal distortion appears as a narrowing of the dot interval in the Y direction with the advance in the -X direction.

[0055] In the case of the two-dimensional MEMS mirror, not only the trapezoidal distortion but also the complex distortion caused by the two-dimensional MEMS mirror itself is added. Therefore, it is difficult to adequately correct the distortion on the oblique image pickup reference surface 24 by using an element with a simple shape such as the wedge-shaped prism as an example of the trapezoidal distortion generating element 40 in the first embodiment. Therefore, it is desirable to use a free-form surface lens as the trapezoidal distortion generating element. As an example of a functional shape representing a free-form surface, there is the following expression (1): Z(x,y)=∑m=1N∑j=0m1amkm−j,jxm−yyj

[0056] Here, Z(x, y) is the displacement of a curved surface at coordinates (x, y) and represents an N-degree polynomial of the two variables x and y. The variables consist of "a" as the normalization parameter and ki,j as the coefficient for xiyj. Here, the optimization of the freeform surface shape was performed under the assumption that N = 6th degree. Fig. 29 and Fig. 30 respectively show the arrival positions of the laser beam in 1-degree steps and the linear illumination area 13 on the illumination reference surface 14 and the reference surface 24 for taking images after optimization.

[0057] Fig. 31 to Fig. 33 are a perspective view, a side view, and a plan view schematically showing the configuration of the laser scanner 60 including the free-form surface lens in the image scanning apparatus 3 according to the third embodiment. Fig. 31 to Fig. 33 are diagrams showing a lens 70 with a free-form surface arranged after the two-dimensional MEMS mirror 620 in Fig. 24 to Fig. 26 is inserted. Each of a first surface 71 and a second surface 72 of the freeform surface lens 70 is a freeform surface represented by expression (1).

[0058] Fig. 34 and Fig. 35 are diagrams showing cross-sectional profiles of the first surface 71 and the second surface 72 of the free-form surface lens 70 of the image sensing device 3 according to the third embodiment. Fig. 34 and Fig. 35 respectively show the cross-sectional profiles of the first surface 71 and the second surface 72 on a surface passing through the optical axis. The solid line indicates a SAG amount [mm] in the X direction, and the dashed line indicates the SAG amount in the Y direction. The SAG amount is a scraping amount in a direction parallel to the optical axis of the lens. In both Fig. 34 as well as Fig. 35 shows that the curvatures in the X-direction and Y-direction have opposite polarities and the curved surface has a saddle shape. Furthermore, Fig. 34 and Fig. 35 that the curve is bilaterally asymmetric in both X and Y directions and that a freeform surface lens must be used which is asymmetric in both X and Y directions to reduce the asymmetric distortion as in Fig. 35 on the condition in Fig. 30. Furthermore, as in Fig. 32, the freeform surface lens 70 is mounted so as to be rotated clockwise by an angle φ in a YZ plane. An incident ray and an outgoing ray (i.e., optical axes 11) of the laser beam 90 that strikes and exits the freeform surface lens 70 when θy = θx = 0 are both in the Z-axis direction. An angle formed by this incident ray and a normal to the first surface 71 on the optical axis is φ = 30 degrees. In a simulation conducted by the inventors of the present application, it was confirmed that it is possible to design the freeform surface shape so as to minimize the difference in curvature of the linear illumination region 13 on the screens (i.e., the illumination reference surface 14 and the image pickup reference surface 24) as shown in Fig. 27 and Fig. 28, is canceled when φ is in a range of 15 degrees to 45 degrees.

[0059] As described above, by inserting the appropriately designed lens 70 with a freeform surface that is asymmetric in both the X and Y directions behind the two-dimensional MEMS 620, the linear illumination region 13 parallel to the X direction itself can be generated on the image recording reference surface 24 orthogonal to the optical axis 21 of the camera 20, as shown in Fig. 30, and epipolar imaging can be performed. (3-3) Configuration example 2 <Fall der Verzerrungshemmung durch Winkelsteuerung einer Welle mit niedriger Geschwindigkeit>

[0060] While the linear illumination area 13 is formed in the straight line shape on the image pickup reference surface 24 arranged obliquely to the optical axis 11 using the lens 70 with a free-form surface in Configuration Example 1, it is also possible to prevent the distortion by controlling the rotation angles θx and θy of the mirror portion 621 similarly to the case of the two galvanometer mirrors described in the second embodiment. The control method and the angle functions in this case are the same as those described above using Fig. 22 and Fig. 23. If the scanning angle θx around the low-speed shaft (i.e., around the joint 623) and the scanning angle θy around the high-speed shaft (i.e., around the joint 622) are determined by functions such as those in Fig. 23(A) and Fig. 23(B), that is, if the values ​​of θx and θy can be appropriately controlled in the short time of drawing the location of a linear illumination region 13, the linear illumination region 13 formed by the line beam can be transformed into a straight line parallel to the X direction, and the epipolar imaging becomes possible.

[0061] However, the rotation around the high-speed shaft (i.e., around the hinge 622) in the two-dimensional MEMS mirror utilizes the resonance phenomenon described above, and therefore, it is difficult to perform control by setting arbitrary angle functions. Even in such cases, if the scanning angle θx around the low-speed shaft (i.e., around the hinge 623) can be controlled, the linear illumination region 13 can be made parallel to the X direction as the locus of the laser beam on the reference surface 24 for image acquisition.

[0062] Fig. 36 is a diagram showing the locus of the laser beam on the image pickup reference surface 24 obtained by controlling the slow wave of the two-dimensional MEMS mirror of the image pickup device 3 according to the third embodiment. Fig. 37 shows a stripe pattern 81 which is produced when the laser beam is switched on and off at regular time intervals, and Fig. Figure 38 shows an example of a vertical stripe pattern 82 generated vertically by controlling the on / off times of the laser beam. In this case, the linear illumination area 13 and the arrival points of the laser beam are determined by the 1-degree steps on the image pickup reference surface 24 as shown in Fig. 36, Fig. 37 and Fig. 38. In the drawings, each linear illumination region 13 is parallel to the X direction, although the length of the linear illumination region 13 decreases as it advances from top to bottom. Even in such cases, it is possible to perform epipolar imaging.

[0063] For example, the use of the fringe pattern projection method as three-dimensional scanning will be considered below. The fringe pattern projection method is a method of projecting a vertical fringe pattern onto a 3D object, photographing the fringe pattern on the 3D object from an oblique angle, and reconstructing the 3D shape based on the type of distortion of the fringe pattern, and is a method known as a type of active stereographic method. When the laser is turned on and off at regular intervals when the device forms a trapezoidal illumination area as in Fig. 36, a stripe pattern 81 is formed in the vertical direction as shown in Fig. 37. This stripe pattern 81 has a pattern in which the angle from the Y axis increases with increasing distance in the X direction. Although the stripe pattern projection method is possible even with such a pattern, an error is likely to occur because the projected stripe pattern is not formed from parallel lines at equal intervals.

[0064] To form a stripe pattern in which all lines are vertical, it is effective to control the laser on-off time interval. If the on-off time interval is controlled to increase as the linear illumination area 13 progresses from top to bottom, a vertical stripe pattern 82 as shown in Fig. 38. By using such a vertical stripe pattern 82, the error in three-dimensional scanning by the stripe pattern projection method can be reduced. Furthermore, since epipolar imaging is performed, three-dimensional scanning with a reduced error and with little influence of reflected stray light is possible when photographing a metallically shiny surface or the like. (3-4) Configuration example 3 <Fall der Verzerrungshemmung durch Freiform-Oberflächen-Linsen und Spiegelwinkelsteuerung >

[0065] While the case where the distortion on the image pickup reference surface 24, which is set obliquely to the optical axis 11, is inhibited by using the free-form surface lens, and the case where the distortion is inhibited by controlling the scanning angle θx around the low-speed shaft (i.e., around the hinge 623) have been described above, it is also possible to consider a case (hybrid method) where both methods are used. For example, the free-form surface lens has a complicated shape with large deflection amounts, as described above in the Fig. 31 to 35, and an error in the surface shape is likely to occur. In addition, an alignment error is likely to occur because the free-form surface lens is set obliquely to the optical axis. When such an assembly error occurs, the linear illumination area 13 on the reference surface 24 that picks up the image may deviate slightly from the straight line shape. Such a slight deviation from the straight line shape can be corrected by the angle control of the mirror. In this case, with the angle control of the mirror portion, a smaller correction amount of the scanning angle θx around the low-speed shaft (i.e., around the hinge 623) is allowable than in the case where the distortion is prevented by the mirror angle control alone.To correct the mounting error, it is desirable to measure the radiation pattern on the screen after mounting the laser scanner 60 and perform the mirror angle control to correct a deviation from a setting value.

[0066] Furthermore, in the case of attempting to prevent distortion by mirror angle control alone, even controlling only the scanning angle θx around the low-speed shaft (i.e., around the hinge 623) requires a considerably high acceleration / deceleration. Therefore, due to the performance of the two-dimensional MEMS, there are cases where sufficient angle control cannot be performed and distortion cannot be prevented. However, with the hybrid method, the angle of the mirror portion 621 can be controlled with a weaker force, and the control accuracy increases, and thus the linear illumination region 13 with parallelism sufficient for epipolar imaging can be obtained. (4) Fourth embodiment

[0067] Fig. 39 is a plan view schematically showing a main configuration of an image scanning device 4 according to a fourth embodiment. While the trapezoidal distortion generating element 40 is arranged in front (i.e., on a projection side) of the laser scanner 10 in the first embodiment, a trapezoidal distortion generating element 80 is arranged in front (i.e., on an image pickup side) of the camera 20 in the fourth embodiment. The trapezoidal distortion generating element 80 has a function of approximating the extension direction of the linear image pickup area 23 to the extension direction of the linear illumination area 13 on the illumination reference surface 14.

[0068] In Fig. 39, the optical axis 21 of the camera 20 is tilted by an angle θ with respect to the Z direction. While the trapezoidal distortion occurs on the image pickup reference surface 24 orthogonal to the optical axis 21 due to the insertion of the trapezoidal distortion generating element 80, the distortion is corrected on the illumination reference surface 14 orthogonal to the laser scanner 10. In the fourth embodiment, the reference surface that aligns the linear illumination region 13 in the X direction is the illumination reference surface 14.In such cases, when the linear image pickup area 23 of the camera 20 and the linear illumination area 13 are scanned synchronously with each other 4 in the state of mutual overlap (preferably in the state of constant mutual overlap), it is possible to scan the linear image pickup area 23 and the linear illumination area 13 on the illumination reference surface 14 (that is, it is possible to perform the epipolar imaging), similar to the movement on the image pickup reference surface 24 in . Fig. 6(E).

[0069] By intersecting the optical axis 21 with the optical axis 11 by inserting the trapezoidal distortion generating element 80, an advantage is achieved because the scanning area 25 in Fig. 39 is made wider than the scanning area of ​​the image scanning device in the Fig. 11 and Fig. 12 shown comparison example.

[0070] Incidentally, except for the features described above, the fourth embodiment is the same as the first embodiment. DESCRIPTION OF REFERENCE SYMBOLS 1 - 4 image scanning device, 10, 50, 60 laser scanners (illumination device), 11 optical axis, 12 total laser scanning area, 13 linear lighting area, 14 Lighting reference surface (lighting screen), 20 camera, 21 optical axis, 22 total image recording area, 23 linear image recording area, 24 Image capture reference area (image capture screen), 25 scanning range, 30 control circuit, 40 Trapezoidal distortion generation element, 70 freeform surface lens, 80 Trapezoidal distortion generation element, 90 laser beam (optical beam), 110, 510, 610 laser light source (light source), 111, 611 mirrors, 113 galvanometer mirrors (optical scanning unit), 211 galvanometer mirror (first optical scanning unit), 212 galvanometer mirrors (second optical scanning unit), 620: two-dimensional MEMS mirror, X horizontal direction (first direction), Y vertical direction (second direction). QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 10359277

[0004] JP 2016-105179

[0025] Cited non-patent literature

[0000] Matthew O'Toole et al., „Homogeneous Codes for Energy-Efficient Illumination and Imaging“, ACM SIGGRAPH, 2015

[0005]

Claims

[1] An image scanning device comprising: an illumination device comprising a light source that emits an optical beam and an illumination optical system that scans a linear illumination area that extends linearly in a first direction on a virtual reference surface as an illumination area onto which the optical beam is projected, in a second direction as a direction orthogonal to the first direction; a camera that performs a photographic operation of scanning a linear image pickup area, which is an image pickup area extending linearly in the first direction on the reference surface in the second direction; and a control circuit that controls the operation of the illumination device and the photographic process of the camera so that the linear illumination area and the linear image recording area on the reference surface continue to overlap each other, wherein an optical axis of the illumination device and an optical axis of the camera are not parallel to each other and intersect each other on the reference surface. [2] An image scanning device according to claim 1, wherein the illumination optical system comprises: an optical beam expanding element that generates an expanding beam as a beam obtained by expanding the optical beam emitted from the light source in the first direction; and an optical scanning unit that scans the linear illumination area formed on the reference surface by the expansion beam in the second direction. [3] The image sensing device according to claim 2, further comprising a trapezoidal distortion generating element arranged in front of the illumination device, the trapezoidal distortion generating element having a function of approximating an extension direction of the linear illumination area to an extension direction of the linear image pickup area on the reference surface. [4] The image sensing device according to claim 3, wherein the trapezoidal distortion generating element is a free-form surface lens that is asymmetric in the first direction and asymmetric in the second direction. [5] The image sensing device according to claim 2, further comprising a trapezoidal distortion generating element arranged in front of the camera, the trapezoidal distortion generating element having a function of approximating an extension direction of the linear image pickup area to an extension direction of the linear illumination area on the reference surface. [6] An image scanning device according to claim 1, wherein the illumination optical system comprises: a first optical scanning unit that forms the linear illumination region by scanning the optical beam emitted from the light source in the first direction; and a second optical scanning unit that scans the linear illumination area in the second direction. [7] The image scanning apparatus according to claim 1, wherein the illumination optical system performs a first scanning operation for forming the linear illumination region by scanning the optical beam emitted from the light source in the first direction and a second scanning operation for scanning the linear illumination region in the second direction. [8] The image sensing device according to claim 7, wherein the illumination optical system is a two-dimensional MEMS mirror. [9] An image scanning device according to claim 8, wherein the scan in the first direction is performed by controlling the two-dimensional MEMS mirror by rotation around a high-speed shaft, and wherein the scan in the second direction is performed by controlling the two-dimensional MEMS mirror by rotation around a low-speed shaft. [10] An image scanning apparatus according to claim 8 or 9, wherein the scanning angle control of scanning in the first direction and the scanning angle control of scanning in the second direction are performed using previously obtained angle functions. [11] An image sensing device according to any one of claims 7 to 10, further comprising a free-form surface lens disposed in front of the illumination device.

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