DISTANCE MEASURING DEVICE

Abstract

A distance measuring device (1) comprises: a first imaging part (10) and a second imaging part (20) which are provided to be aligned such that their fields of view (10a, 20a) overlap; a projection part (30) configured to project pattern light (30a) in which a plurality of types of light regions having wavelength bands that differ from one another are distributed in a predetermined pattern onto an area in which the fields of view (10a, 20a) overlap; and a measuring part (45) configured to measure a distance to an object surface onto which the pattern light (30a) is projected by performing a search process for stereocorrespondence points on images acquired by the first imaging part (10) and the second imaging part (20), respectively.

Description

TECHNICAL FIELD

[0001] The present invention relates to a distance measuring device for processing images captured by a stereo camera and for measuring the distance to an object. STATE OF THE ART

[0002] Previously, a distance measuring device for processing images captured by a stereo camera and measuring the distance to an object was known. In this device, parallax is detected from an image captured by each camera. A pixel block that has the highest correlation with a target pixel block in one image (standard image) is searched for another image (reference image). The search area is set in the separation direction between the cameras with a position that is the same as that of the target pixel block as the standard position. The pixel deviation amount of the pixel block extracted by the search relative to the standard position is detected as parallax. The distance to an object is calculated from this parallax by a triangulation method.

[0003] Furthermore, with such a distance measuring device, a specific light pattern can be projected onto the object. Accordingly, even if the object's surface is monochromatic, the above search can be performed accurately.

[0004] Patent Document 1 below describes a configuration in which a dot pattern of light is generated by a diffractive optical element from laser light emitted by a semiconductor laser. In this configuration, the diffractive optical element has a multi-level diffraction efficiency difference, and a dot pattern exhibiting multi-level luminance gradation is formed due to this diffraction efficiency difference. REFERENCES[PATENTS]

[0005] [PTL 1] Japanese Patent Application No. 2013-190394 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, the surface of an object may have a low reflectance or a high light absorption rate in a certain wavelength band. With the configuration of Patent Document 1 above, if the wavelength of the laser light is within this wavelength band, the luminance gradation of the dot pattern may not be properly captured by the camera. Therefore, it becomes difficult to properly perform a search process for stereo-corresponding points for a pixel block, and therefore the distance to the object surface cannot be accurately measured.

[0007] In view of the above problem, an object of the present invention is to provide a distance measuring device which can accurately measure the distance to an object surface regardless of the reflectance and the light absorption rate of the object surface. PROBLEM SOLVING

[0008] A distance measuring device according to a main aspect of the present invention includes: a first imaging part and a second imaging part provided so as to be aligned so that their fields of view overlap; a projection part configured to project pattern light in which a plurality of types of light regions having wavelength bands different from each other are distributed in a predetermined pattern onto an area where the fields of view overlap; and a measuring part configured to measure a distance to an object surface onto which the pattern light is projected by performing a stereo correspondence point search process on images respectively acquired by the first imaging part and the second imaging part.

[0009] In the distance measuring device according to the present aspect, pattern light in which the plurality of types of light regions having wavelength bands different from each other are distributed in a predetermined pattern is projected onto the object surface. Therefore, even if the object surface has a low reflectance or a high light absorption rate with respect to one of these wavelength bands, the pattern corresponding to the lights in the other wavelength bands is included in the captured images captured by the first imaging part and the second imaging part. Therefore, the specificity of each pixel block is preserved by the distribution pattern of the lights in the other wavelength bands, and the search for stereo correspondence points can be accurately performed. Therefore, the distance to the object surface can be accurately measured. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0010] As described above, according to the present invention, it is possible to provide a distance measuring device which can accurately measure the distance to the object surface regardless of the reflectance and the light absorption rate of the object surface.

[0011] The effects and significance of the present invention will be further clarified by the description of the following embodiment. However, the following embodiment is only an example of the implementation of the present invention. The present invention is by no means limited to the description of the following embodiment. BRIEF DESCRIPTION OF THE DRAWINGS [ Fig. 1] Fig. 1 is a diagram showing a basic configuration of a distance measuring device according to an embodiment. [ Fig. 2] Fig. 2 is a diagram showing a configuration of the distance measuring device according to the embodiment. [ Fig. 3a-3b] Fig. 3(a) and Fig. 3(b) are diagrams showing a method of setting a pixel block for a first image according to the embodiment. [ Fig. 4a-4b] Fig. 4(a) is a diagram schematically showing a state in which a target pixel block is set in the first image according to the embodiment. Fig. Fig. 4(b) is a diagram schematically showing a search area formed in a second image for searching for the target pixel block in Fig. 4(a) is set according to the embodiment. [ Fig. 5a-5b] Fig. 5(a) is a diagram schematically showing a configuration of a filter according to the embodiment. Fig. 5(b) is a diagram showing an enlarged partial region of the filter according to the embodiment. [ Fig. 6a-6b] Fig. 6(a) and Fig. 6(b) are diagrams schematically showing light regions of lights having passed through various filter regions according to the embodiment. [ Fig. 7a-7b] Fig. 7(a) and Fig. 7(b) are diagrams schematically showing light regions of lights that have passed through various filter regions according to the embodiment. [ Fig. 8a-8e] Fig. 8(a) to Fig. 8(d) are graphs showing various kinds of spectral characteristics according to the embodiment. Fig. 8(e) is a graph showing the maximum luminance of each spot light according to the embodiment. [ Fig. 9a-9e] Fig. 9(a) to Fig. 9(d) are graphs showing various kinds of spectral characteristics according to the embodiment. Fig. 9(e) is a graph showing the maximum luminance of each spot light according to the embodiment. [ Fig. 10a-10e] Fig. 10(a) to Fig. 10(d) are graphs showing various kinds of spectral characteristics according to the embodiment. Fig. 10(e) is a graph showing the maximum luminance of each spot light according to the embodiment. [ Fig. 11] Fig. 11 is a flowchart showing an adjustment process of a light emission amount (drive current) of each light source according to the embodiment. [ Fig. 12] Fig. 12 is a diagram showing a configuration of the distance measuring device according to the variant 1. [ Fig. 13a-13e] Fig. 13(a) to Fig. 13(d) are graphs showing various types of spectral characteristics according to variant 1. Fig. Figure 13(e) is a graph showing the maximum luminance of each point light according to variant 1. [ Fig. 14a-14b] Fig. 14(a) is a diagram schematically showing a configuration of the filter according to variant 2. Fig. 14(b) is a diagram showing an enlarged partial region of the filter according to variant 2.

[0012] It should be noted that the drawings are for descriptive purposes only and in no way limit the scope of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

[0013] An embodiment of the present invention will be described below with reference to the drawings. For convenience, in each drawing, the X, Y, and Z axes are additionally shown orthogonal to each other. The X-axis direction is an alignment direction of a first imaging part and a second imaging part, and the positive direction of the Z-axis is the imaging direction of each imaging part.

[0014] Fig. 1 is a diagram showing a basic configuration of a distance measuring device 1.

[0015] The distance measuring device 1 comprises a first imaging part 10, a second imaging part 20 and a projection part 30.

[0016] The first imaging part 10 captures an image of the area of ​​a field of view 10a oriented in the positive Z-axis direction. The second imaging part 20 captures an image of the area of ​​a field of view 20a oriented in the positive Z-axis direction. The first imaging part 10 and the second imaging part 20 are provided to be aligned in the X-axis direction such that their fields of view 10a, 20a overlap. The imaging direction of the first imaging part 10 may be slightly inclined in the direction of the second imaging part 20 from the positive Z-axis direction, and the imaging direction of the second imaging part 20 may be slightly inclined in the direction of the first imaging part 10 from the positive Z-axis direction. The positions in the Z-axis direction and the positions in the Y-axis direction of the first imaging part 10 and the second imaging part 20 are identical.

[0017] The projection part 30 projects pattern light 30a, in which light is distributed in a predetermined pattern, onto an area where the field of view 10a of the first imaging part 10 and a field of view 20a of the second imaging part 20 overlap. The projection direction of the pattern light 30a by the projection part 30 is the positive Z-axis direction. The pattern light 30a is projected onto the surface of an object A1 located in an area where the fields of view 10a, 20a overlap.

[0018] The distance measuring device 1 measures a distance D0 to the object A1 through a stereo correspondence point search using captured images captured by the first imaging part 10 and the second imaging part 20, respectively. Now, the pattern light 30a is projected from the projection part 30 onto the surface of the object A1. Accordingly, the pattern of the pattern light 30a is projected in the captured images captured by the first imaging part 10 and the second imaging part 20. Therefore, even if the surface of the object A1 is monochromatic, the stereo correspondence point search can be accurately performed, and the distance D0 to the surface of the object A1 can be accurately measured.

[0019] In this case, the surface of the object A1 may have a high light absorption rate or a low reflectance in a certain wavelength band. In this case, if the wavelength band of the pattern light 30a is included in this wavelength band, the first imaging part 10 and the second imaging part 20 may not properly capture the images of the pattern of the pattern light 30a. Therefore, there are cases where the previously described search for stereo correspondence points cannot be performed properly, and as a result, the distance D0 to the surface of the object A1 cannot be accurately measured.

[0020] Therefore, in the present embodiment, the pattern light 30a is configured such that a plurality of types of light regions having wavelength bands different from each other are distributed in a predetermined pattern. Even if the surface of the object A1 has a low reflectance or a high light absorption rate with respect to one of these wavelength bands, images of the pattern according to the lights in the other wavelength bands are captured by the first imaging part 10 and the second imaging part 20. Therefore, the search for stereo correspondence points based on the pattern of lights in the other wavelength bands can be properly performed, and the distance to the surface of the object A1 can be accurately measured.

[0021] Fig. 2 is a diagram showing a configuration of the distance measuring device 1.

[0022] The first imaging part 10 comprises an imaging lens 11 and an imaging element 12. The imaging lens 11 concentrates light from the field of view 10a onto an imaging surface 12a of the imaging element 12. The imaging lens 11 does not necessarily have to be a single lens and can be configured as a combination of a plurality of lenses. The imaging element 12 is a monochrome image sensor. The imaging element 12 is, for example, a CMOS image sensor. The imaging element 12 can be a CCD.

[0023] The second imaging part 20 has the same configuration as the first imaging part 10. The second imaging part 20 includes an imaging lens 21 and an imaging element 22. The imaging lens 21 concentrates light from the field of view 20a onto an imaging surface 22a of the imaging element 22. The imaging lens 21 does not necessarily have to be a single lens and can be configured as a combination of a plurality of lenses. The imaging element 22 is a monochrome image sensor. The imaging element 22 is, for example, a CMOS image sensor. The imaging element 22 can be a CCD.

[0024] The projection part 30 comprises the light sources 31 to 33, an optic 34, a filter 35 and a projection lens 36.

[0025] Light sources 31 to 33 emit light in wavelength bands that differ from one another. For example, light source 31 emits light in a wavelength band close to orange, light source 32 emits light in a wavelength band close to green, and light source 33 emits light in a wavelength band close to blue. Light sources 31 to 33 are each light-emitting diodes. Light sources 31 to 33 may each be a different type of light source, such as a semiconductor laser.

[0026] The optics 34 comprises the collimator lenses 341 to 343 and the dichroic mirrors 344, 345.

[0027] Collimator lenses 341 to 343 convert the light emitted from light sources 31 to 33 into substantially collimated light, respectively. Dichroic mirror 344 transmits light incident from collimator lens 341 and reflects light incident from collimator lens 342. Dichroic mirror 345 transmits light incident from dichroic mirror 344 and reflects light incident from collimator lens 343. Accordingly, the light emitted from light sources 31 to 33, respectively, is integrated to be guided to filter 35.

[0028] The filter 35 generates the pattern light 30a from the lights in the respective wavelength bands guided by the optics 34, in which a plurality of types of light regions having wavelength bands that differ from each other are distributed in a predetermined pattern. The configuration and effect of the filter 35 will be described later with reference to Fig. 5(a), Fig. 5(b).

[0029] The projection lens 36 projects the pattern light 30a generated by the filter 35. The projection lens 36 does not necessarily have to be a single lens and may be configured as a combination of a plurality of lenses.

[0030] The distance measuring device 1 comprises, as components of the circuit part, a first image processing part 41, a second image processing part 42, a light source control part 43, a luminance adjustment part 44, a measuring part 45, a control part (“controller”) 46 and a communication interface 47.

[0031] The first image processing part 41 and the second image processing part 42 control the imaging elements 12, 22 and respectively perform processing such as luminance correction and camera calibration on the pixel signals of a first image and a second image output from the imaging elements 12, 22.

[0032] The light source driving part 43 drives the light sources 31 to 33 with driving current values ​​which are respectively set by the luminance adjusting part 44.

[0033] The luminance adjustment part 44 sets the driving current values ​​of the light sources 31 to 33 to the light source driving part 43 based on a pixel signal (luminance) of the second image input from the second image processing part 42. More specifically, the luminance adjustment part 44 sets the driving current values ​​(light emission amounts) of the light sources 31 to 33 such that the maximum luminances differ from each other based on the lights from the light sources 31 to 33 detected based on a pixel signal from the second imaging part 20. The processing performed by the luminance adjustment part 44 will be described later with reference to Fig. 11 described.

[0034] The measuring part 45 compares and processes the first image and the second image, which are respectively input from the first image processing part 41 and the second image processing part 42, and performs the search for stereo correspondence points to detect the distance to the surface of the object A1 with respect to each pixel block in the first image. The measuring part 45 transmits the detected distance information about all pixel blocks to an external device via the communication interface 47.

[0035] That is, the measuring part 45 sets a pixel block (hereinafter referred to as a "target pixel block") in the first image as a distance detection target, and searches for a pixel block corresponding to this target pixel block, that is, a pixel block (hereinafter referred to as a "matching pixel block") that best matches the target pixel block, within a search range defined in the second image. Then, the measuring part 45 performs a process of detecting a pixel deviation amount between a pixel block (hereinafter referred to as a "standard pixel block") in the same position as the target pixel block in the second image and the matching pixel block extracted from the second image by the above search, and calculates the distance to the surface of the object A1 at the position of the target pixel block from the detected pixel deviation amount.

[0036] The measuring part 45 and the communication interface 47 can each be configured by a semiconductor integrated circuit consisting of an FPGA (User Programmable Logic Array). Alternatively, these components can each be configured by another semiconductor integrated circuit, such as a DSP (Digital Signal Processor), a GPU (Graphics Processing Unit), and an ASIC (Application Specific Integrated Circuit).

[0037] The control part 46 is configured by a microcomputer or the like and controls each component according to a predetermined program stored in an internal memory.

[0038] Fig. 3(a), Fig. 3(b) are diagrams schematically showing a method of setting a pixel block 102 for a first image 100. Fig. 3(a) shows a method for setting the pixel block 102 for the entire first image 100, and Fig. 3(b) shows an enlarged partial region of the first image 100.

[0039] As in Fig. 3(a), Fig. 3(b), the first image 100 is divided into a plurality of pixel blocks 102, each comprising a predetermined number of pixel regions 101. Each pixel region 101 is a region corresponding to a pixel on the imaging element 12. That is, the pixel region 101 is the smallest unit of the first image 100. In the example in Fig. 3(a), Fig. 3(b), a pixel block 102 consists of nine pixel regions 101 arranged in three rows and three columns. The number of pixel regions 101 included in a pixel block 102 is not limited thereto.

[0040] Fig. 4(a) is a diagram schematically showing a state in which a target pixel block TB1 is set in the first image 100, and Fig. Fig. 4(b) is a diagram schematically showing a search area R0 formed in a second image 200 for searching for the target pixel block in Fig. 4(a) is discontinued.

[0041] In Fig. 4(b), for practical purposes, similar to the first image 100, the second image 200 captured by the second imaging part 20 is divided into a plurality of pixel blocks 202. Each pixel block 202 comprises pixel regions whose number is the same as that in the previously described pixel block 102.

[0042] In Fig. 4(a), the target pixel block TB1 is a pixel block 102 to be processed from the pixel blocks 102 in the first image 100. In addition, in Fig. 4(b) a standard pixel block TB2 a pixel block 202 in the second image 200 in the same position as the target pixel block TB1.

[0043] The measuring part 45 in Fig. 2 identifies the standard pixel block TB2 in the same position as the target pixel block TB1 in the second image 200. Then, the measuring part 45 sets the position of the identified standard pixel block TB2 as a standard position P0 of the search area R0, and sets an area extending from this standard position P0 in the direction of separation between the first imaging part 10 and the second imaging part 20 as the search area R0.

[0044] The direction in which the search area R0 extends is set to a direction in which the pixel block (matching pixel block MB2) corresponding to the target pixel block TB1 deviates from the standard position P0 in the second image 200 due to parallax. Here, the search area R0 is set as a range of 12 pixel blocks 202 extending in the right direction (direction corresponding to the X-axis direction in Fig. 1) are aligned from the standard position P0. However, the number of pixel blocks 202 included in the search area R0 is not limited to this number. Furthermore, the starting point of the search area R0 is not limited to the standard pixel block TB2, and, for example, a position shifted from the standard pixel block TB2 in the right direction by several blocks can be set as the starting point of the search area R0.

[0045] The measuring section 45 searches for the pixel block (matching pixel block MB2) corresponding to the target pixel block TB1 within the search range R0 set as described above. Specifically, while shifting the search position pixel by pixel from the standard pixel block TB2 in the right direction, the measuring section 45 calculates a correlation value between the target pixel block TB1 and each search position. SSD or SAD, for example, is used as the correlation value. Then, the measuring section 45 identifies the pixel block at the search position exhibiting the highest correlation within the search range R0 as the matching pixel block MB2.

[0046] Further, the measuring part 45 detects a pixel deviation amount of the matching pixel block MB2 with respect to the standard pixel block TB2. Then, the measuring part 45 calculates the distance to the surface of the object A1 by triangulation from the detected pixel deviation amount and the separating distance between the first imaging part 10 and the second imaging part 20. The measuring part 45 performs the same process on all pixel blocks 102 (the target pixel block TB1) in the first image 100. Then, when the distances for all pixel blocks 102 have been detected, the measuring part 45 transmits this distance information to the external device via the communication interface 47.

[0047] The distance measuring device 1 having the above configuration is mounted for use, or in another case, installed, on an end effector (e.g., a gripping section) of a robot arm operating in, for example, a factory. In this case, the control part 46 of the distance measuring device 1 receives a distance detection instruction from a robot controller via the communication interface 47 during a work step of the robot arm. According to this instruction, the control part 46 causes the measuring part 45 to measure the distance between the position of the end effector and the surface of the object A1 as the work target, and transmits the measurement result to the robot controller via the communication interface 47. The robot controller performs feedback control of the operation of the end effector based on the received distance information.Thus, when the distance measuring device 1 is installed on an end effector, the distance measuring device 1 is desirably small in size and light in weight.

[0048] Fig. Fig. 5(a) is a diagram schematically showing a configuration of the filter 35 in Fig. 2 shows. Fig. Figure 5(b) is a diagram showing an enlarged partial region of Fig. 5(a) shows. Fig. 5(a), Fig. 5(b) each shows a state of the filter 35 as viewed from the side of an incident surface 35a of light.

[0049] As in Fig. 5(a), Fig. As shown in Fig. 5(b), a plurality of types of filter regions 351 to 354 are formed on the incident surface 35a of the filter 35 in a predetermined pattern. In Fig. 5(a), Fig. In Figure 5(b), the types of filter regions 351 to 354 are indicated by different hatchings. Filter regions 351 to 353 selectively transmit lights in wavelength bands that differ from each other. The transmission wavelength bands of filter regions 351 to 353 correspond to the wavelength bands of lights emitted by light sources 31 to 33, respectively.

[0050] That is, the filter region 351 mainly has a high transmittance with respect to the wavelength band of the light from the light source 31 and a low transmittance with respect to the other wavelength bands. The filter region 352 mainly has a high transmittance with respect to the wavelength band of the light from the light source 32 and a low transmittance with respect to the other wavelength bands. The filter region 353 mainly has a high transmittance with respect to the wavelength band of the light from the light source 33 and a low transmittance with respect to the other wavelength bands.

[0051] With respect to the filter region 354, the transmittance is set to be low with respect to all wavelength bands of the lights from the light sources 31 to 33. That is, the filter region 354 substantially blocks the lights from the light sources 31 to 33.

[0052] The size of each of the filter regions 351 to 354 is set to a size that, for example, substantially corresponds to one pixel at the imaging elements 12, 22. For example, a region B1 that is Fig. 5(b) by a dashed line, a region corresponding to the region of a pixel block (the pixel block 102, 202 to be used in the previously described search for stereo correspondence points) consisting of three vertically arranged pixels and three horizontally arranged pixels on the imaging elements 12, 22. That is, when the distance D0 to the surface of the object A1 is a standard distance (e.g., an average distance in a distance measuring range), the light in this region B1 is projected into the region of a pixel block consisting of three vertically arranged pixels and three horizontally arranged pixels on the imaging elements 12, 22.

[0053] However, 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 may be larger or smaller than the size corresponding to one pixel. Fig. 5(b), each of the filter regions 351 to 354 is rectangular and has the same size. However, the sizes of the respective filter regions 351 to 354 may be different from each other, and their shapes may be other shapes, such as a square or a circle.

[0054] Preferably, the filter regions 351 to 354 are provided such that various types of filter regions are included in the regions B1 corresponding to all pixel blocks used in the search for stereo correspondence points, and more preferably, such that the filter regions 351 to 354 of all types are included in these regions B1. Furthermore, preferably, the provided pattern of the filter regions included in the region B1 corresponding to a pixel block is specific (random) for each pixel block in each search position, at least in the search range R0 in the search for stereo correspondence points.

[0055] By providing filter regions 351 to 354 in this way, if the luminances of the lights that have passed through filter regions 351 to 354 are made different, as will be described later, the luminance distribution of the lights in the pixel block can be made specific for each pixel block. Accordingly, the accuracy of searching for stereo correspondence points can be improved, and thereby the accuracy of distance measurement can be improved.

[0056] The filter regions 351 to 354 are formed, for example, by the following steps.

[0057] First, a color reserve is applied to the surface of a transparent glass substrate to form the filter region 351. Next, in a state where the region other than the filter region 351 is masked, an ultraviolet ray is applied to insolubilize the color reserve in the region corresponding to the filter region 351. After insolubilization is completed, the mask is removed, and unnecessary color reserve is removed with an alkaline developing liquid. Then, a post-baking process is performed to harden the color reserve at the filter region 351. Accordingly, the filter region 351 is formed on the glass substrate.

[0058] The above step is performed sequentially with respect to the filter regions 352 to 354. Accordingly, the filter regions 352 to 354 are formed sequentially on the glass substrate. Thus, all the filter regions 351 to 354 are formed on the glass substrate. Then, a protective film is formed on the surface of the filter regions 351 to 354. Accordingly, the formation of the filter 35 is completed.

[0059] Fig. 6(a), Fig. 6(b) and Fig. 7(a), Fig. 7(b) are diagrams schematically showing light regions of lights that have passed through the filter regions 351 to 354, respectively, when lights from the light sources 31 to 33 are applied to the entire Fig. 5(b).

[0060] Fig. Fig. 6(a) shows a distribution state of light (spot light DT1) passing through the filter region 351 in Fig. 5(b) was passed, and Fig. Figure 6(b) shows the distribution of light (spot light DT2) passing through the filter region 352 in Fig. 5(b) was passed. Fig. Fig. 7(a) shows a distribution state of light (spot light DT3) passing through the filter region 353 in Fig. 5(b) was passed, and Fig. Fig. 7(b) shows a distribution state of a region (lightless point DT4) in which light passes through the filter region 354 in Fig. 5(b) is shielded.

[0061] From the region in Fig. 5(b), the point lights DT1 to DT3 and the lightless point DT4 are Fig. 6(a) to Fig. 7(b) are integrated to be projected. From the other region of the filter 35, the spot lights DT1 to DT3 and the lightless spot DT4 are also projected in a distribution according to the distribution of the filter regions 351 to 354. Then, the spot lights DT1 to DT3 and the lightless spot DT4 projected from the filter 35 are applied to the surface of the object A1 as the pattern light 30a. Then, the spot lights DT1 to DT3 and the lightless spot DT4 are reflected from the surface of the object A1 and then brought into the first imaging part 10 and the second imaging part 20. Accordingly, the first image 100 and the second image 200 in which the spot lights DT1 to DT3 and the lightless spot DT4 are projected are acquired.

[0062] At this time, the light emission amounts of the light sources 31 to 33 are adjusted such that the maximum luminances of the spot lights DT1 to DT3 and the lightless spot DT4 in the second image 200 are different. More specifically, the light emission amounts of the light sources 31 to 33 are adjusted such that the maximum luminances of the spot lights DT1 to DT3 and the lightless spot DT4 in the second image 200 are approximately uniformly different in the order of luminance.

[0063] Fig. 8(a) to 8(e) are diagrams for describing a method of adjusting the light emission amounts of the light sources 31 to 33.

[0064] Fig. Figure 8(a) is a graph showing the spectral output powers of light sources 31 to 33. The spectral output powers of light sources 31 to 33 are indicated by a solid line, a dotted line, and a dashed line, respectively. The vertical axis of the graph has been normalized based on the maximum output power of light source 31.

[0065] Light source 31 emits light having a center wavelength of approximately 610 nm and an emission bandwidth of approximately 80 nm. Light source 32 emits light having a center wavelength of approximately 520 nm and an emission bandwidth of approximately 150 nm. Light source 33 emits light having a center wavelength of approximately 470 nm and an emission bandwidth of approximately 100 nm.

[0066] Fig. Figure 8(b) is a graph showing the spectral transmittances of filter regions 351 to 353. The spectral transmittances of filter regions 351 to 353 are indicated by a solid line, a dotted line, and a dashed line, respectively. The vertical axis of the graph has been normalized based on the maximum transmittance of filter region 351.

[0067] With respect to the filter region 351, the transmittance increases in association with the increase in wavelength from about 570 nm, and the maximum transmittance is maintained at about 650 nm or more. The filter region 352 has a spectral characteristic in which the maximum transmittance is about 520 nm and the transmission bandwidth is about 150 nm. The filter region 353 has a spectral characteristic in which the maximum transmittance is about 460 nm and the transmission bandwidth is about 150 nm.

[0068] The spectral transmittance of filter region 354 is not shown. The spectral transmittance of filter region 354 is essentially zero at the emission bands (here 400 to 650 nm) of light sources 31 to 33.

[0069] Fig. Figure 8(c) is a graph showing the spectral reflectance of the surface of object A1, which is the measurement surface. A case where the reflectance of the measurement surface is constant regardless of wavelength—that is, a case where the reflectance of the measurement surface exhibits no wavelength dependence—is shown as an example. The vertical axis of the graph has been normalized based on the maximum reflectance.

[0070] Fig. Figure 8(d) is a graph showing the spectral sensitivity of the first imaging part 10 and the second imaging part 20. The spectral sensitivity of the first imaging part 10 and the second imaging part 20 is mainly determined by the spectral transmittance of the imaging lenses 11, 21 and the spectral sensitivity of the imaging elements 12, 22. The vertical axis of the graph has been normalized based on the maximum sensitivity. The spectral sensitivity is approximately 600 nm at the most.

[0071] Fig. Fig. 8(e) is a graph showing the maximum luminances of the point lights DT1 to DT3 and the lightless point DT4 in the second image 200 when the spectral output powers of the light sources 31 to 33, the spectral transmittances of the filter regions 351 to 354, the spectral reflectance of the measurement surface (the surface of the object A1), and the spectral sensitivity of the first imaging part 10 and the second imaging part 20 respectively have the characteristics in Fig. 8(a) to 8(d). The vertical axis of the graph was normalized based on the maximum luminance of the point light DT1.

[0072] In this case, the maximum luminance of the spot light DT3 is approximately 1 / 3 of the maximum luminance of the spot light DT1, and the maximum luminance of the spot light DT2 is approximately 2 / 3 of the maximum luminance of the spot light DT1. That is, if the reflectance of the measuring surface has no wavelength dependence, if the peak values ​​of the spectral output powers of the light sources 31 to 33 are as shown in Fig. 8(a), the maximum luminances of the spot lights DT1 to DT3 based on the lights from the light sources 31 to 33 can be made approximately uniformly different in the order of luminance.

[0073] The luminance adjustment part 44 in Fig. 2 performs an initial adjustment, as described above, of the light emission amounts (drive current values) of the light sources 31 to 33 so that the maximum luminances of the spot lights DT1 to DT3 based on the lights from the light sources 31 to 33 are approximately uniformly different in the order of luminance. Accordingly, if the reflectance of the measurement surface (the surface of the object A1) has no wavelength dependence, the maximum luminances of the spot lights DT1 to DT3 in the first image 100 and the second image 200 have a substantially uniform gradation difference. Therefore, during the search for stereo correspondence points described above, a correlation value that remarkably reaches the maximum value at the search position of the matching pixel block MB2 is calculated. Therefore, the position of the matching pixel block MB2 can be accurately identified, and then distance measurement can be accurately performed.

[0074] On the other hand, when the light emission amounts (drive current values) of the light sources 31 to 33 are initially set as described above, if the reflectance of the measurement surface (the surface of the object A1) has a wavelength dependency, the maximum luminances of the spot lights DT1 to DT3 in the first image 100 and the second image 200 do not have a substantially uniform gradation difference.

[0075] Fig. 9(c) is a graph showing the spectral reflectance of the reflectance of the measuring surface when the reflectance of the measuring surface (the surface of the object A1) has a wavelength dependence, and Fig. 9(e) is a graph showing the maximum luminances of the point lights DT1 to DT3 and the lightless point DT4 in the second image 200 in this case. Fig. 9(a), Fig. 9(b), Fig. 9(d) are the same as Fig. 8(a), Fig. 8(b), Fig. 8(d).

[0076] If the reflectance of the measuring surface has the spectral reflectance as in Fig. 9(c) if the light sources 31 to 33 have the spectral output powers as shown in Fig. 9(a), the gradation difference between the maximum luminance of the spot light DT2 and the maximum luminance of the spot light DT1 becomes smaller than in Fig. 9(e). Therefore, in the second image 200, the region of point light DT1 and the region of point light DT2 are less likely to differ from each other except in luminance, and these regions are more likely to be integrated into a region to be detected. Therefore, the specificity of the point distribution in each pixel block decreases accordingly, and the search accuracy for stereo correspondence points decreases.

[0077] Although the specificities due to the spot lights DT1 and DT2 decrease in this case within the pixel block, the specificity due to the spot light DT3 is preserved. Even if the regions of the spot lights DT1 and DT2 are integrated into one region, as mentioned above, the pixel position at which this region is distributed in each pixel block is more likely to differ between pixel blocks. Therefore, in this case, the specificity of the dot pattern in each pixel block is also readily preserved. Therefore, even in this case, even if each light source is controlled with the initial setting value, the search accuracy for stereo correspondence points can be maintained at a high level.

[0078] In order to more accurately perform the search for stereo correspondence points when the reflectance of the measurement surface has a wavelength dependence as before, it is preferable that the light emission amounts (drive current values) of the light sources 31 to 33 be changed from the initial setting values ​​according to the spectral reflectance of the reflectance of the measurement surface to ensure the luminance difference at the maximum luminances between point lights.

[0079] Fig. 10(a) is a graph showing a method of adjusting the output powers of the light sources 31 to 33 in this case. Fig. 10(b) to 10(d) are the same as Fig. 9(b) to 9(d).

[0080] At this time, the light emission amount (drive current value) of the light source 32 is set to be lower than in the case of Fig. 9(a). Accordingly, as in Fig. 10(e), the maximum luminance of the spot light DT2, and the gradation difference of the luminance between the spot light DT1 and the spot light DT2 is determined as in the case of Fig. 8(e). Accordingly, the maximum luminances of the spot lights DT1 to DT3 based on the lights from the light sources 31 to 33 are approximately uniformly different in the order of luminance.

[0081] Accordingly, the specificity of the pattern of the point lights DT1 to DT3 and the lightless point DT4 in each pixel block is determined as in the case of Fig. 8(e). Therefore, the search for stereo correspondence points can be performed accurately.

[0082] Fig. Fig. 11 is a flowchart showing an adjustment process of light emission amounts (drive currents) of the light sources 31 to 33. This process is controlled by the Fig. 2 before an actual distance measurement is carried out on the object A1.

[0083] The luminance adjustment part 44 sets the driving current values ​​of the light sources 31 to 33 to initial setting values ​​(S101). The initial setting value of each light source is set such that when the reflectance of the surface of the object A1 has no wavelength dependence, the maximum luminances based on the lights from the light sources 31 to 33 are in the order of luminance as shown in Fig. 8(e) are approximately uniformly different. Furthermore, the initial setting value of each light source is set such that, when the reflectance of the surface of the object A1 has a predetermined value (assuming a normal value), the maximum luminances based on the lights from the light sources 31 to 33 appropriately fall within the gradation range (e.g., 0 to 255) that defines the luminance in the first image processing part 41 and the second image processing part 42. For example, the initial setting value of each light source is set such that the largest maximum luminance of the light source 31 becomes slightly smaller (e.g., approximately 80 to 90% of the maximum gradation) than the maximum gradation in the gradation range that defines the luminance.

[0084] Next, the luminance adjustment part 44 sets one of the light sources 31 to 33 as the target light source and drives this light source with a drive current value set for this light source (S102). For example, the light source 31 is set as the target light source. Then, in a state where only the target light source is caused to emit light, the luminance adjustment part 44 causes one of the first imaging part 10 and the second imaging part 20 to perform image capturing (S103). In the present embodiment, the image capturing in step S103 is performed by the second imaging part 20.

[0085] The luminance adjustment part 44 acquires the maximum luminance of the pixels from the captured image (S104). Here, image acquisition is performed by the second imaging part 20, and the luminance adjustment part 44 acquires the maximum luminance of the pixels from the second image 200 acquired by the second imaging part 20. Accordingly, in the second image 200, the luminance is acquired, which is the maximum of the luminances output by the pixels onto which the spot light (here, the spot light DT1) from the target light source (the light source 31) is incident.

[0086] Then, the luminance adjustment part 44 determines whether the processing in steps S102 to S104 has been performed with respect to all light sources 31 to 33 (S105). If a light source that has not undergone processing remains (S105: NO), the luminance adjustment part 44 sets the next light source as the target light source and drives this light source with an initial setting value (current value) corresponding to this light source (S102). For example, light source 32 is set as the target light source. Then, the luminance adjusting part 44 executes the processes in steps S103, S104 as well and detects the maximum luminance of the pixels from the second image 200. Accordingly, in the second image 200, the luminance is detected, which is the maximum of the luminances output from the pixels on which the point light (here, the point light DT2) from the target light source (the light source 32) is incident.

[0087] In this case, too, since there is still an unprocessed light source (the light source 33) (S105: NO), the luminance adjustment part 44 sets the next light source as the target light source and controls this light source with an initial setting value (current value) corresponding to this light source (S102). Accordingly, the last light source 33 is set as the target light source. Then, the luminance adjustment part 44 executes the processes in steps S103 and S104 in the same way and acquires the maximum luminance of the pixels from the second image 200. Accordingly, in the second image 200, the luminance is acquired, which is the maximum of the luminances output by the pixels onto which the point light (here, the point light DT3) from the target light source (the light source 33) is incident.

[0088] Then, when the maximum luminance has been detected based on the initial setting value with respect to all light sources 31 to 33 (S105: YES), the luminance adjustment part 44 determines whether the rest of the detected maximum luminances are correct or not (S506). Specifically, the luminance adjustment part 44 determines whether the maximum luminances detected during the light emission by the light sources 31 to 33 are in the order of magnitude of the luminance as shown in Fig. 8(e) are approximately uniformly different or not.

[0089] That is, the luminance adjustment part 44 determines whether or not the ratio of the maximum luminance (corresponding to the maximum luminance of the spot light DT2) detected during the light emission by the light source 32 with respect to the maximum luminance (corresponding to the maximum luminance of the spot light DT1) detected during the light emission by the light source 31 is included in a predetermined allowable range centered on 66%. Further, the luminance adjustment part 44 determines whether or not the ratio of the maximum luminance (corresponding to the maximum luminance of the spot light DT3) detected during the light emission by the light source 33 with respect to the maximum luminance (corresponding to the maximum luminance of the spot light DT1) detected during the light emission by the light source 31 is included in a predetermined allowable range centered on 33%.

[0090] These allowable ranges are set as ranges that allow maximum luminances adjacent to each other in the magnitude direction to be distinguished from each other, that is, ranges that allow the point lights DT1 to DT3 to be distinguished from each other in the pixel block according to the luminances and pattern of the point lights DT1 to DT3 in order to maintain specificity. For example, these allowable ranges are set to a range of approximately ±10% with respect to 66% and 33% as described above.

[0091] If the maximum luminances detected by the light sources 31 to 33 during light emission are approximately uniformly different in the order of magnitude of the luminance, as in Fig. 8(e) (S106: YES), the luminance adjustment part 44 ends the process in Fig. 11. In this case, the actual distance measurement on the object A1 is carried out by the light sources 31 to 33, which are controlled with the respective initial setting values.

[0092] On the other hand, when the maximum luminances detected from the light sources 31 to 33 during light emission do not differ approximately uniformly in the magnitude of the luminance (S106: NO), the luminance adjusting part 44 performs a process of resetting the driving current values ​​of the light sources 31 to 33 (S107).

[0093] Specifically, the luminance adjustment part 44 resets the driving current values ​​of the light sources 31 to 33 such that: based on the relationship between the luminance and the driving current value that were already available and the present respective maximum luminances, the maximum luminance based on the light emission by the light source 31 becomes slightly smaller (e.g., approximately 80 to 90% of the maximum gradation) than the maximum gradation; and with respect to this maximum luminance, the maximum luminances based on the light emission by the light source 32 and the light source 33 reach approximately 66% and 33%, which correspond to the previously described ratios.

[0094] Now, the luminance adjusting part 44 also determines whether or not any of these three maximum luminances detected in step S104 is saturated, that is, has reached the maximum gradation of the gradation (e.g., 0 to 255) that defines the luminance. If any of the maximum luminances is saturated, the luminance adjusting part 44 sets the drive current value for the light source from which this maximum luminance was detected to be a predetermined gradation lower than the drive current value obtained from the maximum gradation and the relationship between the luminance and the drive current value. In this case, too, the luminance adjusting part 44 resets the drive current values ​​of the light sources 31 to 33 such that the maximum luminances are approximately uniformly different in the order of luminance based on the light emission by the light sources 31 to 33.

[0095] After resetting the drive current values ​​for the light sources 31 to 33, the luminance adjustment part 44 then returns the process to step S102 and detects the maximum luminance during light emission of each light source according to the reset drive current value (S102 to S105). The luminance adjustment part 44 then compares the three detected maximum luminances again and determines whether these maximum luminances are approximately uniformly different in the order of luminance (S106).

[0096] If this determination is YES, the luminance adjustment part 44 ends the process in Fig. 11. In this case, the actual distance measurement on the object A1 is carried out by the light sources 31 to 33, which are each controlled with the reset drive current values.

[0097] On the other hand, if the determination in step S106 is NO, the luminance adjustment part 44 resets the driving current values ​​for the light sources 31 to 33 based on the relationship between the luminance and the driving current value from the three maximum luminances detected at that time (S107), as before, and returns the process to step S102. The luminance adjustment part 44 resets the driving current values ​​of the light sources 31 to 33 until the maximum luminances, each detected based on the light emission by the light sources 31 to 33, are approximately uniformly different in the order of luminance (S106: NO, S107). Then, if these maximum luminances are approximately uniformly different in the order of luminance (S106: YES), the luminance adjustment part 44 ends the process in Fig. 11. Accordingly, the light sources 31 to 33 are each driven with the finally set drive current values, and an actual distance measurement is carried out on the object A1. <Auswirkungen der Ausführungsform>

[0098] According to the above embodiment, the following effects are achieved.

[0099] As in Fig. 6(a) to Fig. As shown in Figure 7(a), the pattern light 30a, in which a plurality of types of light regions (the spot lights DT1 to DT3) having wavelength bands different from each other are distributed in a predetermined pattern, is projected onto the surface of the object A1. Therefore, even if the surface of the object A1 has a low reflectance or a high light absorption rate with respect to one of these wavelength bands, the pattern corresponding to the lights in the other wavelength bands is included in the captured images acquired by the first imaging part 10 and the second imaging part 20. Therefore, the specificity of each pixel block 102 is preserved by the distribution pattern of the lights in the other wavelength bands, and the search for stereo correspondence points can be accurately performed. Therefore, the distance to the surface of the object A1 can be accurately measured.

[0100] As in Fig. As shown in Figure 8(e), the maximum luminances differ among the plurality of types of light regions (the spot lights DT1 to DT3). Accordingly, these light regions (the spot lights DT1 to DT3) can be distinguished from each other according to luminance, and the specificity of each pixel block 102 can be improved according to the distribution of these light regions (the spot lights DT1 to DT3). Therefore, the search for stereo correspondence points can be accurately performed, and the distance to the surface of the object A1 can be accurately measured.

[0101] As in Fig. 2 and Fig. 5(a), Fig. As shown in Fig. 5(b), the projection part 30 includes the filter 35 in which a plurality of types of filter regions 351 to 353 for respectively generating the plurality of types of light regions (the spot lights DT1 to DT3) are distributed in the same pattern as the pattern of the light regions (the spot lights DT1 to DT3). Accordingly, the pattern light 30a in which the plurality of types of light regions (the spot lights DT1 to DT3) are distributed in a desired pattern can be easily generated. Since no variation (variation of luminance gradation) of the diffraction difference is caused due to a manufacturing error or an assembly error, unlike a diffractive optical element, the pattern light in which the plurality of types of light regions (the spot lights DT1 to DT3) are distributed in a desired pattern can be stably generated.

[0102] As in Fig. As shown in Figure 2, the projection part 30 includes a plurality of light sources 31 to 33 that emit lights in mutually different wavelength bands; and the optics 34 that guides the lights emitted from the plurality of light sources 31 to 33 to the filter 35. Accordingly, lights for generating the plurality of types of light regions (the spot lights DT1 to DT3) can be easily applied to the filter 35.

[0103] As in Fig. 8(a), Fig. As shown in Fig. 8(b), the plurality of light sources 31 to 33 are provided to correspond to the plurality of types of filter regions 351 to 353, respectively, and each of the filter regions 351 to 353 selectively extracts light from a corresponding one of the light sources 31 to 33. Accordingly, the plurality of types of light regions (the spot lights DT1 to DT3) can be efficiently generated.

[0104] As in Fig. As shown in Figure 8(e), the maximum luminances differ from each other based on the lights from the respective light sources 31 to 33 detected based on a pixel signal from the second imaging part 20. Accordingly, the plurality of types of light regions (the spot lights DT1 to DT3) can be distinguished from each other according to the luminances, and the specificity of each pixel block 102 can be improved according to the distribution of these light regions (the spot lights DT1 to DT3). Therefore, the search for stereo correspondence points can be accurately performed, and the distance to the surface of the object A1 can be accurately measured.

[0105] As in Fig. As shown in FIG. 11, the luminance adjustment part 44 adjusts the light emission amounts (drive current values) of the plurality of light sources 31 to 33 such that the maximum luminances differ from each other based on the lights from the respective light sources 31 to 33 detected based on a pixel signal from the second imaging part 20 (S101, S107). Accordingly, even if the reflectance or light absorption rate of the surface of the object A1 has a wavelength dependency, the maximum luminances can be caused to differ from each other based on the lights from the respective light sources 31 to 33.Therefore, even if the reflectance or light absorption rate of the surface of the object A1 exhibits wavelength dependence, the plurality of types of light regions (the spot lights DT1 to DT3) can be distinguished from each other according to their luminances, and the specificity of each pixel block 102 can be improved according to the distribution of these light regions (the spot lights DT1 to DT3). Therefore, the search for stereo correspondence points can be accurately performed, and the distance to the surface of the object A1 can be accurately measured.

[0106] In steps S101 and S107 in Fig. 11, the luminance adjusting part 44 adjusts the light emission amounts (drive currents) of the plurality of light sources 31 to 33 such that the maximum luminances based on the lights from the respective light sources 31 to 33 detected based on a pixel signal from the second imaging part 20 are approximately uniformly different in the order of luminance, as shown in Fig. 10(e). Accordingly, the maximum luminances based on the lights from the respective light sources 31 to 33 can be made to differ greatly from each other. Therefore, the plurality of types of light regions (the point lights DT1 to DT3) can be clearly distinguished from each other according to luminance, and the specificity of each pixel block 102 can be significantly improved according to the distribution of these light regions (the point lights DT1 to DT3). Therefore, the search for stereo correspondence points can be performed more accurately, and the distance to the surface of the object A1 can be measured more accurately.

[0107] In the above embodiment, the light sources 31 to 33 are each light-emitting diodes. Accordingly, speckle noise can be prevented from being superimposed on the captured image (the first image 100, the second image 200) of the pattern light 30a. Therefore, the search for stereo correspondence points can be performed accurately, and the distance to the surface of the object A1 can be accurately measured.

[0108] As in Fig. As shown in Figure 7(b), the pattern light 30a includes a lightless region (the lightless point DT4). Accordingly, variation in the luminance gradation of the light regions (the point lights DT1 to DT3, the lightless point DT4) can be increased, and the specificity of each pixel block 102 according to the distribution of these light regions (the point lights DT1 to DT3, the lightless point DT4) can be further improved. Furthermore, superposition of light regions (the point lights DT1 to DT3) having frequency bands different from each other by the lightless region (the lightless point DT4) can be prevented, and the luminance gradation based on these light regions (the point lights DT1 to DT3) can be appropriately preserved. Therefore, the search for stereo correspondence points can be performed more accurately, and the distance to the surface of the object A1 can be measured more accurately. <Variante 1>

[0109] In the above embodiment, the three light sources 31 to 33, corresponding to the spot lights DT1 to DT3, are provided in the projection part 30. However, in Variant 1, only one light source is provided in the projection part 30.

[0110] Fig. 12 is a diagram showing a configuration of the distance measuring device 1 according to the variant 1.

[0111] The projection part 30 includes a light source 37, a collimator lens 38, the filter 35, and the projection lens 36. The light source 37 emits light in a wavelength band that includes selected wavelength bands of the plurality of types of filter regions 351 to 353. The light source 37 is, for example, a white laser diode. The collimator lens 38 collimates the light emitted from the light source 37. The collimator lens 38 forms an optical system that guides the light from the light source 37 to the filter 35. The configurations of the filter 35 and the projection lens 36 are the same as in the above embodiment. The configurations other than the projection part 30 are the same as the configurations in Fig. 2.

[0112] Fig. 13(a) is a graph showing a spectral output of the light source 37, and Fig. 13(b) is a graph showing spectral transmittances of the filter regions 351 to 353. Fig. 13(c) to 13(e) are the same as Fig. 8(c) to 8(e).

[0113] When the light source 37 has the spectral output power characteristic in Fig. 13(a), and the filter regions 351 to 353 have the spectral transmittance characteristics in Fig. 13(b) if the spectral reflectance of the measurement surface (the surface of the object A1) and the spectral sensitivity of the first imaging part 10 and the second imaging part 20 each have the characteristics in Fig. 13(c), Fig. 13(d), the maximum luminances of the point lights DT1 to DT3 are approximately uniformly different in the order of magnitude of the luminance, as shown in Fig. 13(e).

[0114] Therefore, according to the configuration of Variant 1, by only causing the light source 37 to emit light, it is possible to make the maximum luminances of the spot lights DT1 to DT3 different from each other, and to make these maximum luminances differ approximately uniformly in the order of luminance. Therefore, similar to the above embodiment, the distance to the surface of the object A1 can be accurately measured. Furthermore, the number of components of the projection part 30 can be reduced, and the configuration of the projection part 30 can be simplified.

[0115] However, in the configuration of Variant 1, no light source is provided for each of the spot lights DT1 to DT3. Therefore, unlike the above embodiment, the light quantities of the spot lights DT1 to DT3 cannot be adjusted according to the wavelength dependence of the reflectance of the surface of the object A1. Therefore, in order to more accurately perform the search for stereo correspondence points when the reflectance of the surface of the object A1 has a wavelength dependence, it is preferable that the light sources 31 to 33 be provided for the respective spot lights DT1 to DT3 as in the above embodiment.

[0116] In the configuration of Variant 1, the luminance adjustment part 44 adjusts the light emission amount (drive current value) of the light source 37 such that: the maximum luminances based on the spot lights DT1 to DT3 are not saturated; and these maximum luminances appropriately fall within the gradation range (e.g., 0 to 255) that defines the luminance in the first image processing part 41 and the second image processing part 42. In this case, before the distance measurement, the luminance adjustment part 44 causes the light source 37 to emit light at the initial value to capture the second image 200 and captures the maximum luminance from the second image 200.Then, when the maximum luminance is saturated or too low, the luminance adjustment part 44 resets the driving current value of the light source 37 based on the relationship between the luminance and the driving current value, so that the maximum luminance becomes slightly lower than the highest gradation. The maximum luminances of the spot lights DT1 to DT3 fall appropriately within the gradation range (e.g., 0 to 255) that defines the luminance. <Variante 2>

[0117] In variant 2, a light-shielding wall is formed at the boundary between the filter regions that adjoin one another at the filter 35.

[0118] Fig. 14(a) is a diagram schematically showing a configuration of the filter 35 according to Variant 2. Fig. Figure 14(b) is a diagram showing a subregion of Fig. 14(a) shows enlarged.

[0119] As in Fig. 14(a), Fig. As shown in Fig. 14(b), in variant 2, a light-shielding wall 355 is formed at the boundary between the filter regions adjacent to each other on the filter 35. The height of the light-shielding wall 355 is the same as the thickness of the filter regions 351 to 354. The light-shielding wall 355 is formed in a matrix shape in advance on the above-described glass substrate constituting the filter 35. One box of the matrix corresponds to a filter region. On the glass substrate on which the light-shielding wall 355 is thus formed, the filter regions 351 to 354 are formed through the above-described steps. Accordingly, the filter 35 having the configuration in Fig. 14(a), Fig. 14(b).

[0120] By forming the light-shielding wall 355 in this way, overlapping of spot lights due to leakage during transmission through the adjacent filter regions can be prevented. Thus, a good pattern light 30a can be generated in which the respective types of spot lights can be clearly distinguished from each other. Accordingly, the search for stereo correspondence points can be performed more accurately, and the distance to the surface of the object A1 can be measured more accurately. <Sonstige Varianten>

[0121] In Variant 1 above, a single light source 37, which has a spectral output across the wavelength band of the spectral transmittances of the three filter regions 351 to 353, is provided in the projection part 30. However, a light source having a spectral output across the wavelength band of the spectral transmittances of the two filter regions 352, 353 and a light source having a spectral output corresponding to the wavelength band of the spectral transmittance of the filter region 351 may be provided. Alternatively, a light source having a spectral output across the wavelength band of the spectral transmittances of the two filter regions 351, 352 and a light source having a spectral output corresponding to the wavelength band of the spectral transmittance of the filter region 353 may be provided.

[0122] In this case, an optic in which lights from these two light sources are integrated to be guided to the filter 35 is provided in the projection part 30. The light source having the spectral output power across the wavelength bands of the two spectral transmittances may have such a spectral output power characteristic that the maximum luminances based on the lights of these two wavelength bands as well as in Fig. 8(e) differ from each other, and the output power of the other light source can be adjusted such that the maximum luminance based on this light differs from the maximum luminances based on the two lights as in Fig. 8(e).

[0123] In the above embodiment, as shown in Fig. 5(a), Fig. As shown in Fig. 5(b), four types of filter regions 351 to 354 are provided on the filter 35. However, the types of filter regions provided on the filter 35 are not limited thereto. For example, two types of filter regions may be provided on the filter 35, or alternatively, five or more types of filter regions may be provided on the filter 35.

[0124] In this case, a plurality of light sources may be provided to have a one-to-one correspondence with the types of filter regions, or alternatively, a light source having spectral outputs corresponding to the spectral transmittances of a plurality of types of filter regions may be provided. That is, the number of light sources may be set smaller than the number of types of filter regions, and the spot lights in wavelength bands that are respectively different from each other may be generated from a plurality of types of filter regions based on the light from a single light source. Also in this case, the spectral output of each light source and the spectral transmittance of each filter region may be set such that the maximum luminances of spot lights respectively generated by all types of filter regions differ from each other.Further preferably, the spectral output power of each light source and the spectral transmittance of each filter region can be adjusted such that the maximum luminances of these point lights differ approximately uniformly from each other in the order of magnitude of the luminance.

[0125] The spectral characteristics are not limited to those in Fig. 8(a) to 8(d), Fig. 9(a) to 9(d), Fig. 10(a) to 10(d) and Fig. 13(a) to 13(d). The spectral output power of each light source and the spectral transmittance of each filter region can be changed as needed, as long as the maximum luminances of point lights generated by the filter regions are different from each other. Furthermore, the wavelength bands of each light source and each type of filter region are not limited to those shown in the above embodiment and its variants.

[0126] The deployment pattern of each type of filter region is not limited to the Fig. 5(a), Fig. 5(b) is limited and can be changed as needed. Also in this case, the deployment pattern of the filter regions can be set such that the deployment pattern of the respective types of point lights in each pixel block is specific (random), at least in the search area R0.

[0127] In the above embodiment and its variants, the transmission-type filter 35 is shown as an example. However, a reflection-type filter may be used. In this case, for example, a reflection film is formed between the glass substrate constituting the filter 35 and a material layer constituting each filter region.

[0128] In the above embodiment and its variants, a plurality of types of light regions having wavelength bands different from each other are the point lights DT1 to DT3. However, these light regions do not necessarily have to be points, and as long as the distribution pattern of the light regions has specificity (randomness) for each pixel block at least in the search area R0, the plurality of types of light regions may have a shape other than a point.

[0129] In the above embodiment, in step S103 in Fig. 11 an image of the surface of the object A1 is taken by the second imaging part 20. In step S103 in Fig. 11, however, an image of the surface of the object A1 may be captured by the first imaging part 10, and the maximum luminance detecting process in step S104 may be performed using the first image 100 captured by the first imaging part 10.

[0130] In the above embodiment and its variants, two imaging parts, namely the first imaging part 10 and the second imaging part 20, are used, but three or more imaging parts may be used. In this case, these imaging parts are provided such that the fields of view overlap, and the pattern light 30a is projected onto the area where these fields of view overlap. The search for stereo correspondence points is performed between the imaging parts forming a set.

[0131] The form of use of the distance measuring device 1 is not limited to the Fig.1 or a use in which the distance measuring device 1 is installed on an end effector of a robot arm. The distance measuring device 1 may be used in another system in which predetermined control is performed using the distance to an object surface. Furthermore, the configuration of the distance measuring device 1 is not limited to the configuration shown in the above embodiment. For example, a light sensor array in which a plurality of light sensors are provided in a matrix form may be used as the imaging elements 12, 22.

[0132] In addition to the above, various changes may be made to the embodiment of the present invention as needed without departing from the scope of the technical idea defined by the claims. LIST OF REFERENCE SYMBOLS 1 distance measuring device 10 first part of the illustration 10a, 20a field of view 20 second part of the illustration 30 Projection part 30a sample light 31 to 33, 37 light source 34 Optics 35 filters 38 Collimator lens (optics) 44 Luminance adjustment part 45 measuring part 351 to 354 filter region DT1 to DT3 point light (light region) DT4 lightless point (lightless region) 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] JP 2013-190394

[0005]

Claims

[1] Distance measuring device comprising: a first imaging part and a second imaging part provided to be aligned such that their fields of view overlap; a projection part configured to project pattern light in which a plurality of types of light regions having wavelength bands different from each other are distributed in a predetermined pattern onto an area where the fields of view overlap; and a measuring part configured to measure a distance to an object surface onto which the pattern light is projected by performing a stereo correspondence point search process on images respectively acquired by the first imaging part and the second imaging part. [2] The distance measuring device according to claim 1, wherein the maximum luminances differ from each other among the plurality of types of light regions. [3] A distance measuring device according to claim 1 or 2, wherein the projection part comprises a filter in which a plurality of kinds of filter regions for respectively generating the plurality of kinds of light regions are distributed in the same pattern as the pattern of the light regions. [4] A distance measuring device according to claim 3, wherein the projection part comprises: a plurality of light sources configured to emit lights in mutually different wavelength bands; and optics configured to direct the lights emitted by the plurality of light sources to the filter. [5] A distance measuring device according to claim 4, wherein the plurality of light sources are provided to correspond to the plurality of types of filter regions, respectively, and each of the filter regions selectively extracts light from a corresponding one of the light sources. [6] The distance measuring device according to claim 5, wherein the maximum luminances are different from each other based on the lights from the respective light sources detected based on a pixel signal from the first imaging part or the second imaging part. [7] Distance measuring device according to claim 5 or 6, comprising a luminance adjustment part configured to adjust the light emission amounts of the plurality of light sources, respectively, wherein the luminance adjusting part adjusts the light emission amounts of the plurality of light sources such that the maximum luminances differ from each other based on the lights from the respective light sources detected based on a pixel signal from the first imaging part or the second imaging part. [8] The distance measuring device according to claim 7, wherein the luminance adjusting part adjusts the light emission amounts of the plurality of light sources such that the maximum luminances approximately uniformly differ in an order of luminance based on the lights from the respective light sources detected based on the pixel signal from the first imaging part or the second imaging part. [9] Distance measuring device according to claim 3, wherein the projection part comprises: a light source configured to emit light in a wavelength band including selected wavelength bands of the plurality of types of filter regions; and optics configured to guide the light from the light source to the filter, and the light source has a spectral output such that the maximum luminances of lights transmitted through the plurality of types of filter regions differ from each other. [10] Distance measuring device according to one of claims 4 to 9, wherein the light source is a light-emitting diode. [11] A distance measuring device according to any one of claims 1 to 10, wherein the pattern light comprises a lightless region.

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