Distance measuring device

Abstract

The purpose of the present invention is to suppress the time taken for distance measurement while improving resolution. A distance measurement device (1) is provided with: a first imaging unit (10) and a second imaging unit (20); a light projection unit (30) that projects the pattern light (30a); and a measurement unit (45) that measures the distance to the surface of the object (A1) on which the pattern light (30a) has been projected, on the basis of images captured by the first imaging unit (10) and the second imaging unit (20), respectively. The light projection unit (30) is provided with: light sources (31)-(33) including a plurality of wavelength ranges; an optical filter (35) in which a plurality of types of optical filter regions for forming each of the plurality of types of optical regions are distributed in the same pattern as the pattern of the optical regions; and a plurality of optical elements disposed on at least one of the incident surface side and the exit surface side of the filter region. The optical element projects the light region so as to have a first focal point (F1) and have a second focal point (F2) farther from the distance measurement device (1) than the first focal point (F1).

Description

Technical Field

[0001] The present disclosure relates to a distance measuring device. Background Art

[0002] Conventionally, a distance measuring device that processes an image acquired by a stereo camera to measure the distance to an object has been known. In this device, parallax is detected based on images captured by a pair of cameras. A pixel block having the highest correlation with an object pixel block in an image captured by one camera (reference image) is searched for in an image captured by the other camera. A search range is set along the separation direction of the cameras with the same position as the object pixel block as the reference position. The pixel offset amount of the pixel block extracted by the search relative to the reference position is detected as parallax. The distance to the object is calculated based on this parallax by triangulation.

[0003] In the mapping method in three-dimensional optical ranging of Patent Document 1, a light beam is divided into a plurality of light spots, and light spots having shape characteristics that change in a prescribed manner according to the distance along the optical axis of the light beam are formed, and the pattern of the light spots is projected onto an object. In Patent Document 1, the positions of the light spots within the pattern are in an uncorrelated state.

[0004] The three-dimensional measurement system of Patent Document 2 has a first imaging unit and a second imaging unit that are separated from each other. In the three-dimensional measurement system of Patent Document 2, images of an object captured by the first imaging unit and the second imaging unit are used, and the parallax of a first feature point in the image of the object is calculated by image processing based on the pattern projection method. In addition, in the three-dimensional measurement system of Patent Document 2, images of the object captured by both the first imaging unit and the second imaging unit are used, and a corresponding point for a second feature point in the image of the object is searched for by image processing based on the stereo camera method. Based on the search result, the parallax of the second feature point is calculated, and the three-dimensional shape of the object is determined based on the parallax of the first feature point and the parallax of the second feature point.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 5592070 Gazette

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2021-192064 Summary of the Invention

[0009] However, in the distance measuring device of Patent Document 1, since the positions of the light spots within the pattern are in an uncorrelated state, the interval between the light spots cannot be reduced. Therefore, the portion where the light of the light spots is not projected becomes larger, and the resolution of the distance measuring device cannot be improved.

[0010] In addition, in the three-dimensional measurement system of Patent Document 2, after performing image processing based on the pattern projection method on the images of the object captured by the first imaging unit and the second imaging unit, corresponding points are searched through image processing based on the stereo camera method. Therefore, it takes time for distance measurement.

[0011] An object of the present disclosure is to provide a distance measurement device capable of suppressing the time taken for distance measurement while improving the resolution.

[0012] To solve the above problems, a distance measurement device according to an embodiment of the present disclosure includes: a first imaging unit and a second imaging unit, which are arranged and configured so as to form a range where the fields of view overlap with each other; a light projecting unit that projects pattern light in which a plurality of light regions having different wavelength ranges are distributed in a predetermined pattern onto the overlapping range of the fields of view; and a measurement unit that measures the distance to the surface of an object onto which the pattern light is projected based on the images respectively captured by the first imaging unit and the second imaging unit. The light projecting unit includes: a light source that includes the wavelength range; a filter in which a plurality of filter regions for respectively forming the plurality of light regions are distributed in the same pattern as the predetermined pattern of the light regions; and a plurality of optical elements that are disposed on at least one of the incident surface side and the exit surface side of the filter region, and the optical element has two different focal points and forms the light region.

[0013] According to the distance measurement device of the present disclosure, it is possible to suppress the time taken for distance measurement while improving the resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing the basic structure of the distance measurement device according to the embodiment.

[0015] Figure 2 It is a diagram showing the structure of the distance measurement device according to the embodiment.

[0016] Figure 3A It is a diagram schematically showing a method for setting pixel blocks for the entire first image according to the embodiment.

[0017] Figure 3B It is a diagram schematically showing a method for setting pixel blocks for the first image by magnifying a partial region of the first image according to the embodiment.

[0018] Figure 4A It is a diagram schematically showing the structure of the filter according to the embodiment.

[0019] Figure 4B It is toFigure 4A A diagram showing a magnified view of a part of the structure of the filter involved in the embodiment.

[0020] Figure 5A A perspective view of the filter involved in the embodiment.

[0021] Figure 5B A perspective view of the filter involved in the embodiment with the microlens omitted.

[0022] Figure 6A A schematic diagram showing an example of the pattern light involved in the embodiment when the height of the object is h1.

[0023] Figure 6B A schematic diagram showing an example of the pattern light involved in the embodiment when the height of the object is h2.

[0024] Figure 6C A schematic diagram showing an example of the pattern light involved in the embodiment when the height of the object is h3.

[0025] Figure 6D A schematic diagram showing an example of the pattern light involved in the embodiment when the height of the object is h4.

[0026] Figure 7A A chart showing the spectral output of the light source for explaining the wavelength range output by the light source involved in the embodiment.

[0027] Figure 7B A chart showing the spectral transmittance of the filter region for explaining the wavelength range output by the light source involved in the embodiment.

[0028] Figure 8 A flowchart for explaining the calculation method of the distance index value of the measurement unit involved in the embodiment.

[0029] Figure 9A A diagram showing an example of the luminance value in the pixel block involved in the embodiment when the height of the object is h1.

[0030] Figure 9B A diagram showing an example of the luminance value in the pixel block involved in the embodiment when the height of the object is h2.

[0031] Figure 9C A diagram showing an example of the luminance value in the pixel block involved in the embodiment when the height of the object is h3.

[0032] Figure 9D A diagram showing an example of the luminance value in the pixel block involved in the embodiment when the height of the object is h4.

[0033] Figure 10A It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions. Figure 9A It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions.

[0034] Figure 10B It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions. Figure 9B It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions.

[0035] Figure 10C It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions. Figure 9C It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions.

[0036] Figure 10D It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions. Figure 9D It is a schematic diagram showing an example of the luminance values when the pixel block involved is divided into four regions.

[0037] Figure 11A It is a diagram schematically showing the state of setting an object pixel block on a first image for explaining a method of searching for an object pixel block involved in an embodiment.

[0038] Figure 11B It is a diagram schematically showing, for explaining a method of searching for an object pixel block involved in an embodiment, the search range set on a second image for searching for Figure 11A the object pixel block.

[0039] Figure 12 It is a diagram showing the structure of a distance measurement device involved in a modification.

[0040] Figure 13A It is a diagram showing the spectral output of a light source for explaining the wavelength range output by a light source involved in a modification.

[0041] Figure 13B It is a diagram showing the spectral transmittance of a filter region for explaining the wavelength range output by a light source involved in a modification.

[0042] Figure 14 It is a perspective view of a filter involved in a modification. Detailed Description of the Embodiment

[0043] Hereinafter, embodiments of the present disclosure will be described in detail based on the drawings. The following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the technology of the present disclosure, its applications, or its uses.

[0044] (Embodiment)

[0045] Figure 1 It is a diagram showing the basic structure of a distance measurement device 1 involved in an embodiment.

[0046] As shown Figure 1 in FIG. 1, the distance measuring device 1 includes a first imaging unit 10, a second imaging unit 20, and a light projecting unit 30.

[0047] The first imaging unit 10 captures an image of a field of view 10a facing the positive Z-axis direction. The second imaging unit 20 captures an image of a field of view 20a facing the positive Z-axis direction. The first imaging unit 10 and the second imaging unit 20 are arranged and configured to be separated by a predetermined distance (baseline length) in the X-axis direction so as to form a range where the fields of view 10a and 20a overlap with each other. The imaging direction of the first imaging unit 10 may be slightly inclined from the positive Z-axis direction toward the second imaging unit 20, and the imaging direction of the second imaging unit 20 may be slightly inclined from the positive Z-axis direction toward the first imaging unit 10. The positions of the first imaging unit 10 and the second imaging unit 20 in the Z-axis direction and the Y-axis direction are the same as each other. Herein, the "imaging direction" is the direction of the optical axis of the first imaging unit 10 or the direction of the optical axis of the second imaging unit 20.

[0048] The light projecting unit 30 projects a pattern light 30a in which light is distributed in a predetermined pattern onto the overlapping range of the fields of view 10a and 20a. The projection direction of the pattern light 30a of the light projecting unit 30 is the positive Z-axis direction. The pattern light 30a is projected onto the surface of an object A1 existing in the overlapping range of the fields of view 10a and 20a.

[0049] The distance measuring device 1 measures the distance D0 to the object A1 by performing a stereo correspondence point search using the captured images respectively captured by the first imaging unit 10 and the second imaging unit 20. At this time, the pattern light 30a is projected from the light projecting unit 30 onto the surface of the object A1. As a result, the pattern of the pattern light 30a is projected onto the captured images of the first imaging unit 10 and the second imaging unit 20. Therefore, even when the surface of the object A1 is a single color, the stereo correspondence point search can be performed with high accuracy, and the distance D0 to the surface of the object A1 can be accurately measured.

[0050] Figure 2 FIG. 1 is a diagram showing the structure of the distance measuring device according to the embodiment.

[0051] The first imaging unit 10 includes an imaging lens 11 and an imaging element 12. The imaging lens 11 has a focal length and is used to converge the light from the field of view 10a onto the imaging surface 12a of the imaging element 12. The imaging lens 11 may not be a single lens or may be composed of a combination of multiple lenses. The imaging element 12 is a monochromatic image sensor. The imaging element 12 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor. In addition, the imaging element 12 may also be a CCD (Charge Coupled Device).

[0052] The second imaging unit 20 has the same structure as the first imaging unit 10. Specifically, the second imaging unit 20 includes an imaging lens 21 and an imaging element 22. The imaging lens 21 has the same focal length as the imaging lens 11 and is used to converge the light from the field of view 20a onto the imaging surface 22a of the imaging element 22. The imaging lens 21 may not be a single lens or may be composed of a combination of multiple lenses. The imaging element 22 is a monochromatic image sensor. In addition, the imaging element 22 is, for example, a CMOS image sensor. The imaging element 22 may also be a CCD.

[0053] The light projecting unit 30 includes light sources 31 to 33, an optical system 34, a filter 35, and a projection lens 36.

[0054] The light sources 31 to 33 emit light in mutually different wavelength ranges. For example, the light source 31 emits light in a wavelength range near red, the light source 32 emits light in a wavelength range near green, and the light source 33 emits light in a wavelength range near blue. The light sources 31 to 33 are, for example, light emitting diodes. In addition, the light sources 31 to 33 may also be other types of light sources such as semiconductor lasers.

[0055] The optical system 34 includes collimating lenses 341 to 343, dichroic mirrors 344, 345. The collimating lenses 341 to 343 respectively convert the light emitted from the light sources 31 to 33 into substantially parallel light. The dichroic mirror 344 allows the light incident from the collimating lens 341 to pass through and reflects the light incident from the collimating lens 342. The dichroic mirror 345 allows the light incident from the dichroic mirror 344 to pass through and reflects the light incident from the collimating lens 343. In this way, the light emitted from the light sources 31 to 33 is combined and guided to the filter 35.

[0056] The filter 35 generates pattern light 30a in which a plurality of light regions with mutually different wavelength bands are distributed in a specified pattern according to the light in each wavelength range guided out from the optical system 34. In addition, the specific structure of the filter 35 will be described later.

[0057] The projection lens 36 projects the pattern light 30a generated by the filter 35. The projection lens 36 may not be a single lens, or may be constituted by combining a plurality of lenses.

[0058] The distance measurement device 1 has a structure including a first imaging processing unit 41, a second imaging processing unit 42, a light source driving unit 43, a brightness adjustment unit 44, a measurement unit 45, a control unit 46, and a communication interface 47 as circuit units.

[0059] The first imaging processing unit 41 and the second imaging processing unit 42 control the imaging elements 12 and 22, and perform processing such as brightness correction and camera calibration on the pixel signals of the first image and the second image output from the imaging elements 12 and 22 respectively.

[0060] The light source driving unit 43 drives the light sources 31 to 33 with the driving current values set by the brightness adjustment unit 44.

[0061] The brightness adjustment unit 44 sets the driving current values of the light sources 31 to 33 in the light source driving unit 43 based on the pixel signals (brightness) of the second image input from the second imaging processing unit 42. Specifically, the brightness adjustment unit 44 sets the driving current values (light emission amounts) of the light sources 31 to 33 so that the maximum brightness based on the light from the light sources 31 to 33 obtained based on the pixel signals from the second imaging unit 20 is not saturated.

[0062] The measurement unit 45 performs a comparison process on the first image and the second image respectively input from the first imaging processing unit 41 and the second imaging processing unit 42 to perform a stereo corresponding point search, and obtains the distance to the surface of the object A1 for each pixel block on the first image. The measurement unit 45 sends the distance information of the amounts of all the pixel blocks obtained to an external device via the communication interface 47.

[0063] That is, the measurement unit 45 sets a pixel block (hereinafter referred to as "object pixel block") on the first image as an object for obtaining the distance, and searches for a pixel block corresponding to the object pixel block, that is, the pixel block that best matches the object pixel block (hereinafter referred to as "matching pixel block") within a specified search range on the second image. Then, the measurement unit 45 performs the following processing: obtains the pixel offset amount between the pixel block (hereinafter referred to as "reference pixel block") at the same position as the object pixel block on the second image and the matching pixel block extracted from the second image through the above search, and calculates the distance to the surface of the object A1 at the position of the object pixel block based on the obtained pixel offset amount.

[0064] The measurement unit 45 and the communication interface 47 may also be constituted by a semiconductor integrated circuit formed by an FPGA (Field Programmable Gate Array). In addition, each of these units may be constituted by other semiconductor integrated circuits such as a DSP (Digital Signal Processor), a GPU (Graphics Processing Unit), and an ASIC (Application Specific Integrated Circuit).

[0065] The control unit 46 is constituted by a microcomputer or the like, and controls each unit according to a predetermined program stored in the built-in memory.

[0066] Figure 3A and Figure 3B FIGS. are diagrams schematically showing a method of setting pixel blocks for a first image. Specifically, Figure 3A shows a method of setting pixel blocks 102 for the entire first image 100, Figure 3B and shows a part of the first image 100 in an enlarged manner.

[0067] As Figure 3A and Figure 3B shown, the first image 100 is divided into a plurality of pixel blocks 102 each including a predetermined number of pixel regions 101. The pixel region 101 is a region corresponding to one pixel on the imaging element 12. That is, the pixel region 101 is the smallest unit of the first image 100. In the examples of Figure 3A and Figure 3B , one pixel block 102 is constituted by nine pixel regions 101 arranged in three rows and three columns. However, the number of pixel regions 101 included in one pixel block 102 is not limited to this.

[0068] Figure 4A and Figure 4B FIGS. are diagrams showing the structure of the filter according to the embodiment. Specifically, Figure 4A is a diagram schematically showing the structure of the filter 35. Figure 4B is a diagram showing a part of Figure 4A in an enlarged manner. In Figure 4A and Figure 4B , the state of the filter 35 is shown when observed from the light incident surface 35a side.

[0069] As Figure 4A and Figure 4B shown, in the filter 35, a plurality of filter regions 351 to 354 are formed in a predetermined pattern. In Figure 4A and Figure 4BThe types of the filter regions 351 to 354 are shown by different types of shading. The filter regions 351 to 354 selectively transmit lights of different wavelength ranges to form light regions of different hues. Here, the filter region 351 forms a light region corresponding to the hue "red", the filter region 352 forms a light region corresponding to the hue "orange", the filter region 353 forms a light region corresponding to the hue "green", and the filter region 354 forms a light region corresponding to the hue "blue". The characteristics of the light sources 31 to 33 and the filter regions 351 to 354 will be described later.

[0070] The size of each of the filter regions 351 to 354 is set, for example, to a size substantially corresponding to one pixel block on the imaging elements 12 and 22. For example, in Figure 4B the region B1 shown by the dashed line is a region corresponding to the region of a pixel block (the pixel block 102 used in the above-mentioned stereo corresponding point search) composed of three pixels in the vertical direction and three pixels in the horizontal direction on the imaging elements 12 and 22. That is, when the distance D0 to the surface of the object A1 is a reference distance (for example, the middle distance of the ranging range), the light in this region B1 is projected onto the region of a pixel block composed of three pixels in the vertical direction and three pixels in the horizontal direction on the imaging elements 12 and 22. In addition, the size of each of the filter regions 351 to 354 is not necessarily limited to the size corresponding to one pixel. The size of each of the filter regions 351 to 354 can be larger or smaller than the size corresponding to one pixel block. In addition, in Figure 4B each of the filter regions of the filter regions 351 to 354 is rectangular and has the same size, but the sizes of the filter regions 351 to 354 can also be different from each other, and in addition, its shape can also be other shapes such as a square or a circle.

[0071] The filter regions 351 to 354 are preferably arranged so as to include different types of filter regions in the region B1 corresponding to all the pixel blocks used for stereo corresponding point search, and more preferably arranged so as to include all the types of filter regions 351 to 354 in these regions B1 respectively. In addition, preferably, the arrangement pattern of the filter regions included in the region B1 corresponding to the pixel block is special (random) for each pixel block at least in the search range R0 (refer to Figure 11B ) in the stereo corresponding point search.

[0072] When the filter regions 351 to 354 are arranged in this way, as described later, by making the brightnesses of the lights passing through the filter regions 351 to 354 different from each other, the brightness distribution of the light in the pixel block can be made special for each pixel block. Thereby, the accuracy of the stereo corresponding point search can be improved, and as a result, the accuracy of the distance measurement can be improved.

[0073] Figure 5A and Figure 5B are perspective views of the filter involved in the embodiment. Specifically, Figure 5A shows a perspective view of the filter 35, Figure 5B shows a perspective view of the filter 35 with the microlenses 53 omitted.

[0074] As Figure 5A shown, the filter 35 includes a transparent substrate 51, a filter layer 52, and microlenses 53 (optical elements).

[0075] The transparent substrate 51 is disposed on the incident surface 35a side of the filter layer 52 and is for allowing the light incident from the light sources 31 to 33 to pass through. The transparent substrate 51 is, for example, a transparent glass substrate or the like.

[0076] The filter layer 52 is formed with a plurality of filter regions including filter regions 351 to 354 in a predetermined pattern. As Figure 5B shown, each of the filter regions formed in the filter layer 52 is formed in a square shape in plan view.

[0077] The microlenses 53 are disposed on the exit surface side of the filter layer 52. The microlenses 53 receive the light incident from the light sources 31 to 33 via the transparent substrate 51 and the filter layer 52 and project the pattern light 30a. Specifically, the microlenses 53 are arranged in an array along the X direction and the Y direction in a manner corresponding to the filter regions respectively.

[0078] Here, the microlenses 53 have different radii of curvature in two intersecting directions. In Figure 5A , the radius of curvature R1 of the microlens 53 in the first direction S1 is different from the radius of curvature R2 in the second direction S2. Specifically, in the microlens 53, the radius of curvature R1 in the first direction S1 is set such that the focal position F1 in the first direction S1 is closer to the distance measuring device 1 than the measurement range S0 of the distance measuring device 1. In addition, in the microlens 53, the radius of curvature R2 in the second direction S1 is set such that the focal position F2 in the second direction S1 is farther from the distance measuring device 1 than the measurement range S0 of the distance measuring device 1 (see Figure 1 ). Further, the first direction S1 and the second direction S2 are orthogonal in plan view (when observed from the incident surface 35a side). In addition, in the calculation of the distance index value described later, more preferably, the angle of the second direction S2 with respect to the X axis is set to about 45 degrees. From the above, it can be seen that for the microlens 53, the focal length in the first direction S1 is smaller than the focal length in the second direction S2.

[0079] Here, as an embodiment of the optical element, a microlens having an optical surface formed of a continuous surface has been described, but it is not limited thereto. For example, a Fresnel lens having a plurality of annular zones, a diffractive lens, etc. can be used.

[0080] Figures 6A - 6D is a schematic diagram showing an example of the pattern light according to the embodiment. Here, the measurement surface of the object A1 onto which the pattern light is projected is a plane having the same height H (refer to Figure 1 ), which is a plane parallel to the XY plane in Figure 1 . Specifically, Figures 6A - 6D is a schematic diagram of the pattern light 30a when the height H of the object A1 is h1 to h4, respectively. In addition, the heights h1 to h4 of the object A1 are such that h1 > h2 > h3 > h4. That is, the measurement distance D0 from the measurement device 1 is the shortest at the height h1 and the longest at the height h4.

[0081] As shown in Figures 6A - 6D , each pattern light 30a includes point lights DT1 to DT4 formed of a plurality of light regions in an array. The hues of the plurality of point lights DT1 to DT4 are different from each other. Here, the point light DT1 is of the hue "red", the point light DT2 is of the hue "orange", the point light DT3 is of the hue "green", and the point light DT4 corresponds to the hue "blue". The same shading indicates point lights of the same hue.

[0082] As shown in Figure 6A , in the case of the height h1 of the object A1, the surface of the object A1 is close to the focal position F1 in the first direction S1 and away from the focal position F2 in the second direction. Therefore, the length L1 of the point light DT1 in the first direction S1 becomes shorter, and the length L2 in the second direction S2 becomes longer. Since they are projected onto the surface of the object A1 at the same height, the pattern lights DT2 to DT4 having different hues also have the same shape.

[0083] As shown in Figure 6B , in the case of the height h2 of the object A1, the surface of the object A1 is at a position slightly away from the focal position F1 in the first direction S1 and closer to the focal position F2 in the second direction. Therefore, the length L1 of the point light DT1 in the first direction S1 is slightly shorter than the length L2 in the second direction S2. The same applies to the point lights DT2 to DT4.

[0084] As shown in Figure 6C , in the case of the height h3 of the object A1, the surface of the object A1 is disposed at a substantially intermediate position between the focal position F1 in the first direction S1 and the focal position F2 in the second direction. Therefore, the length L1 of the point light DT1 in the first direction S1 is substantially the same as the length L2 in the second direction S2. The same applies to the point lights DT2 to DT4.

[0085] As Figure 6D shown, when the height of the object A1 is h4, the surface of the object A1 is far from the focal position F1 in the first direction S1 and close to the focal position F2 in the second direction. Therefore, the length L1 of the point light DT1 in the first direction S1 becomes longer, and the length L2 in the second direction S2 becomes shorter. The same applies to the point lights DT2 to DT4.

[0086] As described above, in the present embodiment, the shape of each point light included in the pattern light 30a changes according to the height H (measurement distance D0) of the object A1.

[0087] Figure 7A and Figure 7B is a diagram for explaining the wavelength range output by the light source according to the embodiment.

[0088] Figure 7A is a graph showing the spectral outputs of the light sources 31 to 33. The spectral outputs of the light sources 31, 32, and 33 are represented by a solid line E11, a dashed line E12, and a dotted line E13, respectively. Here, the vertical axis of the graph is normalized according to the maximum output of the light source 31.

[0089] The light source 31 emits light with a center wavelength of around 610 nm and an emission bandwidth of around 80 nm. The light source 32 emits light with a center wavelength of around 520 nm and an emission bandwidth of around 150 nm. The light source 33 emits light with a center wavelength of around 470 nm and an emission bandwidth of around 100 nm.

[0090] Figure 7B is a graph showing the spectral transmittances of the filter regions 351, 352, 353, and 354. The spectral transmittances of the filter regions 351 to 354 are represented by a solid line E21, a dot-and-dash line E22, a dashed line E23, and a dotted line E24, respectively. Here, the vertical axis of the graph is normalized according to the maximum transmittance of the filter region 351.

[0091] In the filter region 351, the transmittance increases as the wavelength increases from around 570 nm, and the maximum transmittance is maintained above around 650 nm. The filter region 351 mainly transmits the light from the light source 31 to form a light region (spot light) with a "red" hue. The filter region 352 has spectral characteristics with a maximum transmittance of around 560 nm and a transmission wavelength width of around 160 nm, and mainly transmits the light from the light source 31 and the light from the light source 32 to form a light region (spot light) with an "orange" hue. The filter region 353 has spectral characteristics with a maximum transmittance of around 520 nm and a transmission frequency band width of around 150 nm, and mainly transmits the light from the light source 32 to form a light region (spot light) with a "green" hue. The filter region 354 has spectral characteristics with a maximum transmittance of around 460 nm and a transmission frequency band width of around 150 nm, and mainly transmits the light from the light source 33 to form a light region (spot light) with a "blue" hue.

[0092] Here, a filter having four types of spectral transmittances has been described, but it is not limited thereto. For example, by adding a filter having a spectral transmittance that transmits multiple wavelength regions according to the wavelength regions of the light sources 31 to 33, a large number of different-hued light regions (spot lights) can be further formed.

[0093] Next, the measurement unit 45 explains a method for calculating a distance index value based on the first image and the second image.

[0094] Figure 8 It is a flowchart for explaining the calculation method of the distance index value of the measurement unit 45 according to the embodiment. Figures 9A - 9D It is a schematic diagram showing an example of the luminance values in a pixel block. Figures 10A - 10D It is a schematic diagram showing an example of the luminance values when a pixel block is divided into four regions. Specifically, Figures 9A - 9D It shows the luminance values when the height of the object A1 is h1 to h4. In addition, Figures 10A - 10D It shows respectively when Figures 9A - 9D the pixel block is divided into four regions.

[0095] The measurement unit 45 extracts the luminance values of the respective pixels included in one pixel block (step S1). For example, in the case where a pixel block is composed of nine pixel regions 101 arranged in three rows and three columns, the luminance values of the respective pixels constituting the pixel block are extracted (refer to Figures 9A - 9D ).

[0096] Next, the measurement unit 45 calculates the luminance center of gravity of the pixel block based on the extraction result in step S1 (step S2). The measurement unit 45 divides the pixel block into four regions centered on the luminance center of gravity of the pixel block, and calculates the luminance values in each region (step S3). For example, the pixel block is divided into four regions by a straight line extending in the X direction and a straight line extending in the Y direction centered on the luminance center of gravity. At this time, the pixels existing on these straight lines are assigned luminance to each region according to the area divided by the straight line. In this way, the luminance values in each region are calculated (refer to Figures 10A - 10D ).

[0097] Then, the measurement unit 45 calculates a distance index value (step S4). Specifically, when the luminance values of the upper-right region, upper-left region, lower-left region, and lower-right region in a pixel block are set as D1 to D4 respectively (specifically refer to Figure 10A ), the distance index value is represented by the following formula (1).

[0098] [Equation 1]

[0099]

[0100] Figure 11A And Figure 11B are diagrams for explaining the search method of the target pixel block related to the embodiment. Specifically, Figure 11A is a diagram schematically showing the state in which the target pixel block TB1 is set on the first image 100, Figure 11B is a diagram schematically showing the search range R0 set on the second image 200 in order to search for the Figure 11A target pixel block.

[0101] In Figure 11B , for convenience, the second image 200 acquired from the second imaging unit 20 is divided into a plurality of pixel blocks 202 in the same manner as the first image 100. The pixel block 202 includes the same number of pixel regions as the above-mentioned pixel block 102.

[0102] In Figure 11A , the target pixel block TB1 is the pixel block 102 to be processed among the pixel blocks 102 on the first image 100. In addition, in Figure 11B , the reference pixel block TB2 is the pixel block 202 on the second image 200 corresponding to the target pixel block TB1.

[0103] The measurement unit 45 determines a reference pixel block TB2 corresponding to the target pixel block TB1 on the second image 200. Then, the measurement unit 45 sets the position of the determined reference pixel block TB2 as the reference position P0 of the search range R0, and sets the range extending in the separation direction of the first imaging unit 10 and the second imaging unit 20 from the reference position P0 as the search range R0.

[0104] Here, the measurement unit 45 determines the reference pixel block TB2 corresponding to the target pixel block TB1 in the first image based on the distance index value calculated in Figure 8 step S4. For example, the measurement unit 45 sets the pixel block corresponding to the calculated distance index value in the pixel blocks of the second image as the reference pixel block TB2. More specifically, using the distance value corresponding to the distance index value measured in advance and tabulated, the parallax amount with respect to the distance index value is calculated based on the focal lengths of the imaging lenses 11, 21, the distance (baseline length) between the first imaging unit 10 and the second imaging unit 20, and the pixel size of the imaging element. Thereby, the reference position P0 of the search range R0 can be set to be close to the pixel block (matching pixel block MB2) corresponding to the target pixel block TB1, so that the processing load can be reduced.

[0105] The extending direction of the search range R0 is set to the direction in which the pixel block (matching pixel block MB2) corresponding to the target pixel block TB1 on the second image 200 is shifted from the reference position P0 due to parallax. Here, the search range R0 is set to the range of eleven pixel blocks 202 arranged in the right direction (the direction corresponding to the X-axis direction of Figure 1 ). However, the number of pixel blocks 202 included in the search range R0 is not limited to this.

[0106] The measurement unit 45 searches for the pixel block (matching pixel block MB2) corresponding to the target pixel block TB1 in the set search range R0. Specifically, the measurement unit 45 calculates the correlation value between the target pixel block TB1 and each search position while moving the search position pixel by pixel in the right direction from the reference pixel block TB2. The correlation value uses, for example, SSD (Sum of Squared Difference) or SAD (Sum of Absolute Difference). Then, the measurement unit 45 determines the pixel block at the search position with the highest correlation in the search range R0 as the matching pixel block MB2.

[0107] Further, the measurement unit 45 obtains the pixel offset of the matching pixel block MB2 with respect to the reference pixel block TB2. Then, the measurement unit 45 calculates the distance to the surface of the object A1 by triangulation based on the obtained pixel offset and the separation distance between the first imaging unit 10 and the second imaging unit 20. The measurement unit 45 performs the same process on all the pixel blocks 102 (target pixel blocks TB1) on the first image 100. Thus, when the distances of all the pixel blocks 102 are obtained, the measurement unit 45 transmits the distance information to an external device via the communication interface 47.

[0108] In addition to being fixed to a conveying device such as a belt conveyor for use, the distance measuring device 1 is also provided at the end effector (holding part, etc.) of a robotic arm that performs work operations in a factory. When provided at the end effector of the robotic arm, the control unit 46 of the distance measuring device 1 receives an instruction to obtain a distance from a robot controller via the communication interface 47 during the work process of the robotic arm. According to this instruction, the control unit 46 causes the measurement unit 45 to measure the distance between the position of the end effector and the surface of the object A1 serving as the work target, and transmits the measurement result to the robot controller via the communication interface 47. The robot controller performs feedback control on the movement of the end effector based on the received distance information. Thus, when the distance measuring device 1 is provided at the end effector, it is desirable for the distance measuring device 1 to be small and lightweight.

[0109] (Modification example)

[0110] Figure 12 FIG. is a diagram showing the structure of the distance measuring device according to the modification example. In the above-described embodiment, the three light sources 31 to 33 are arranged in the light projecting unit 30, but in this modification example, only one light source is arranged in the light projecting unit 30.

[0111] The light projecting unit 30 includes a light source 37, a collimating lens 38, a filter 35, and a projection lens 36. The light source 37 emits light in a wavelength band including the selected wavelength bands of a plurality of filter regions 351 to 354. The light source 37 is, for example, a white laser diode. The collimating lens 38 collimates the light emitted from the light source 37. The collimating lens 38 constitutes an optical system for guiding the light from the light source 37 to the filter 35. The structures of the filter 35 and the projection lens 36 are the same as those in the above-described embodiment. In addition, the structure other than the light projecting unit 30 is the same as that of Figure 2 .

[0112] Figure 13A FIG. is a chart showing the spectral output of the light source 37. In Figure 13A , the spectral output of the light source 37 is indicated by a solid line E31. Figure 13B FIG. is a chart showing the spectral transmittance of the filter regions 351 to 354. In Figure 13BAmong them, the spectral transmittances of the filter regions 351, 352, 353, and 354 are represented by a solid line E41, a dotted line E42, a dashed line E43, and a dot line E44, respectively.

[0113] If the light source 37 has Figure 13A a spectral output and the filter regions 351 to 354 have Figure 13B a spectral transmittance, then in this modification, the same effects as those of the above-described embodiment can be obtained.

[0114] In addition, in the above-described embodiment, the shape of each filter region formed in the filter 35 (filter layer 52) is square in plan view (refer to Figure 5B ), but it is not limited thereto. For example, as Figure 14 shown, the shape of each filter region formed in the filter 35 (filter layer 52) can be circular or any shape in plan view.

[0115] In addition, a light projection control unit that adjusts the brightness of the light emitted from the light source included in the light projection unit 30 may be provided for the distance measurement device 1. For example, a light projection control unit may be provided as Figure 2 a part of the control unit 46 in Figure 12 .

[0116] Industrial Applicability

[0117] The distance measurement device of the present disclosure can suppress the time taken for distance measurement while improving the resolution. Therefore, the distance measurement device of the present disclosure can perform measurement with higher accuracy and higher efficiency in three-dimensional measurement and is useful in industry.

[0118] Explanation of Reference Numerals

[0119] 1: Distance measurement device; 10: First imaging unit; 20: Second imaging unit; 30: Light projection unit; 30a: Pattern light; 31 to 33, 37: Light sources; 35: Filter; 45: Measurement unit; 53: Microlens (optical element).

Claims

1. A distance measuring device, comprising: a first imaging unit and a second imaging unit, which are arranged and configured in such a way that a range where the fields of view overlap with each other is formed; A light projecting unit that projects pattern light in which a plurality of light regions having different wavelength ranges are distributed in a predetermined pattern onto the overlapping range of the fields of view; and a measuring unit that measures the distance to the surface of an object onto which the specified pattern light is projected, based on the images respectively captured by the first imaging unit and the second imaging unit, wherein the light projecting unit comprises: a light source that includes the wavelength range; a filter, in which multiple filter regions for respectively forming the multiple light regions are distributed in the same pattern as the specified pattern of the light regions; and multiple optical elements that are arranged on at least one of the incident surface side and the exit surface side of the filter region, wherein the optical element has two different focal points and forms the light region.

2. The distance measuring device according to claim 1, wherein the optical element is a lens that has a first focal point and a second focal point with a focal length greater than that of the first focal point, and the first curvature radius is different from the second curvature radius, where the first curvature radius is the curvature radius in the first direction, and the second curvature radius is the curvature radius in the second direction that intersects the first direction.

3. The distance measuring device according to claim 2, wherein the first direction and the second direction are substantially orthogonal.

4. The distance measuring device according to claim 2, wherein the first focal point is set closer to the distance measuring device than the measurement range of the distance measuring device, and the second focal point is set farther from the distance measuring device than the measurement range.

5. The distance measuring device according to claim 1, wherein the light source includes multiple light sources that emit lights with mutually different wavelength ranges, and the light projecting unit further comprises an optical system that guides the lights emitted from the multiple light sources to the filter.

6. The distance measuring device according to claim 1, wherein the multiple filter regions are used to extract the light in the wavelength range corresponding to the hue of the light regions from the light emitted from the light source.

7. The distance measuring device according to claim 1, wherein it further comprises a light projecting control unit that adjusts the brightness of the light emitted from the light source.

8. The distance measuring device according to claim 1, wherein the measuring unit performs a stereo corresponding point search process on a first image captured by the first imaging unit and a second image captured by the second imaging unit.

9. The distance measuring device according to claim 8, wherein in the stereo corresponding point search process, the measuring unit selects a reference block from the first image, extracts a light region pixel block containing the light region within the selected reference block, calculates a distance index value to the surface onto which the light of the light region is projected based on the pixel values of the light region pixel block, and determines the search start position of a reference pixel block in the second image according to the distance index value.

Images