Distance measuring device and distance measuring method

Abstract

To provide a distance measuring device with which it is possible to obtain a distance measurement value in a saturated pixel even when a pixel whose sensor value is saturated exists in a sensor for detecting reflected light.SOLUTION: A light emission unit 12 irradiates with light an object (subject 20) whose distance is to be measured. A TOF sensor 13 generates a sensor value corresponding to the distance to the object corresponding to each pixel of each frame. A distance conversion unit 14 converts the sensor value corresponding to each pixel of each frame to a distance, and generates a distance measurement image composed of a distance measurement value corresponding to each pixel of each frame. A distance correction unit 15 divides the distance measurement image of each frame into a plurality of sections, and when a pixel without a distance measurement value exists in any section, corrects the distance measurement image by allocating the average value of distance measurement values of pixels, except the pixel without a distance measurement value, to the pixel without a distance measurement value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distance measuring device and a distance measuring method. [Background technology]

[0002] For example, in various fields such as object detection in automobiles, self-driving robots using SLAM (Simultaneous Localization and Mapping) technology, and conveyors used in factories, distance measuring devices are used that irradiate an object with light, receive the light reflected from the object, and measure the distance from the point where the light is irradiated to the object (see Patent Document 1 or 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-275331 [Patent Document 2] Japanese Patent Application Publication No. 2019-66185 Summary of the Invention [Problem to be solved by the invention]

[0004] In some distance measuring devices, the amount of light to be emitted is set so that when light is shone onto a white board with a reflectivity of 94%, known as a white chart, the sensor value of the sensor that detects the reflected light does not become saturated and distance can be measured. The sensor value is the electrical signal level obtained by the sensor detecting the light and performing photoelectric conversion. In such distance measuring devices, if the object being measured for distance is a reflector (hereinafter referred to as a retroreflector) that uses retroreflection technology to reflect light from a light source back toward the light source, the incident light will be reflected with a higher intensity than if it were reflected by a white chart. Therefore, the sensor value of the sensor that detects the reflected light will become saturated, resulting in distance measurement failure or erroneous distance measurement.

[0005] There is a need for a distance measuring device and a distance measuring method that can obtain distance measurement values ​​at saturated pixels even when the sensor detecting reflected light includes pixels whose sensor values ​​are saturated. [Means for solving the problem]

[0006] The present invention provides a distance measuring device comprising: a light emitting unit that irradiates light onto an object to be measured; a sensor that detects reflected light from the object, generates one or more frames consisting of a plurality of pixels arranged horizontally and vertically, and generates a sensor value according to the distance to the object corresponding to each pixel in each frame; a distance conversion unit that converts the sensor value corresponding to each pixel in each frame into a distance and generates a distance measurement image consisting of distance measurement values ​​corresponding to each pixel in each frame; and a distance correction unit that divides the distance measurement image of each frame into a plurality of sections, and when there is a pixel in any section for which no distance measurement value has been obtained, corrects the distance measurement image by assigning the average distance measurement value of pixels in any section excluding the pixel for which no distance measurement value has been obtained to the pixel for which no distance measurement value has been obtained.

[0007] The present invention provides a distance measurement method that irradiates an object to be measured with light emitted from an light emitting unit, detects the light reflected by the object, generates one or more frames consisting of a plurality of pixels arranged horizontally and vertically, generates a sensor value corresponding to the distance to the object corresponding to each pixel in each frame, converts the sensor value corresponding to each pixel in each frame into a distance, generates a distance measurement image consisting of distance measurement values ​​corresponding to each pixel in each frame, divides the distance measurement image of each frame into a plurality of sections, and when there is a pixel in any section for which no distance measurement value has been obtained, corrects the distance measurement image by assigning to the pixel for which no distance measurement value has been obtained the average value of the distance measurement values ​​of pixels in any section excluding the pixels for which no distance measurement value has been obtained. [Effects of the Invention]

[0008] According to the distance measuring device and distance measuring method of the present invention, even if there are pixels in which the sensor value is saturated in the sensor that detects reflected light, it is possible to obtain a distance measurement value at the saturated pixel. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a distance measuring device according to the first embodiment. [Figure 2] FIG. 2 is a characteristic diagram showing the reflection level of the reflected light when near-infrared light is irradiated onto a white chart and the reflection level of the reflected light when near-infrared light is irradiated onto a retroreflective material. [Figure 3] FIG. 3 is a diagram showing a state in which a distance measurement image is divided into a plurality of sections. [Figure 4] FIG. 4 shows the enlarged sections set at the right and bottom edges when the distance measurement image is divided into a plurality of sections. [Figure 5] FIG. 5 is a diagram showing an example in which there are pixels in one section for which no distance measurement value has been obtained. [Figure 6] FIG. 6 is a diagram showing an example of a method for selecting a section for correcting a section in which distance measurement values ​​are not obtained for all pixels. [Figure 7] FIG. 7 is a diagram showing an example in which the method of selecting a section for correcting a section in which distance measurement values ​​are not obtained for all pixels is different between the left and right regions of each frame. [Figure 8] FIG. 8 is a block diagram showing a distance measuring device according to the second embodiment. [Figure 9] FIG. 9 is a diagram conceptually showing a distance measurement image captured by the distance measuring device according to the second embodiment in close-distance mode of an object, and a corrected distance measurement image. [Figure 10] FIG. 10 is a diagram conceptually showing a distance measurement image captured by the distance measuring device according to the second embodiment in the medium distance mode of an object, and a corrected distance measurement image. [Figure 11] FIG. 11 is a conceptual diagram showing a distance measurement image captured by the distance measuring device according to the second embodiment in long distance mode of an object, and a corrected distance measurement image. [Figure 12]FIG. 12 is a block diagram showing a distance measuring device according to the third embodiment. [Figure 13] FIG. 13 is a block diagram showing a distance measuring device according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Distance measuring devices and distance measuring methods according to first to fourth embodiments will be described below with reference to the accompanying drawings. In the distance measuring devices according to first to fourth embodiments, the same parts are given the same reference numerals, and their description may be omitted.

[0011] First Embodiment 1 shows a TOF (Time Of Flight) camera 101, which is a distance measuring device according to the first embodiment. The TOF camera 101 includes a lens 11, a light emitter 12, a TOF sensor 13, a distance conversion unit 14, and a distance correction unit 15. The TOF camera 101 captures an image of a subject 20, which includes a retroreflective material 21, as an object to be measured. A distance measurement value utilization device 30 that utilizes the distance measurement values ​​generated by the TOF camera 101 is connected to the TOF camera 101.

[0012] For example, the retroreflective material 21 has a honeycomb structure and includes beads or prisms to increase the amount of reflected light. The retroreflective material 21 may be a retroreflective plate such as a road sign, or a guide or warning sign used inside or outside a building. If the subject 20 is a security guard or worker, the retroreflective material 21 may be a retroreflective sheet attached to the uniform worn by the security guard or the work clothes worn by the worker.

[0013] The distance measurement value utilization device 30 may be an object recognition device, or may be a device that estimates the self-position of a moving object using SLAM technology and creates an environmental map. The distance measurement value utilization device 30 may be provided within the TOF camera 101.

[0014] The light-emitting unit 12 is, for example, a vertical cavity surface-emitting laser (VCSEL), and irradiates the subject 20 with near-infrared light having a wavelength of, for example, 940 nm within a predetermined irradiation range. The light-emitting unit 12 sets the amount of emitted near-infrared light so that when the near-infrared light is irradiated onto a white chart with a reflectance of 94%, the TOF sensor 13 can generate a sensor value that can measure distance within any distance measurement range without saturating. The sensor value is an electrical signal level obtained by the TOF sensor 13 detecting light and performing photoelectric conversion.

[0015] Near-infrared light reflected by the subject 20 is collected by the lens 11 and enters the TOF sensor 13. Here, an indirect sensor is used as the TOF sensor 13. In the indirect distance measurement method, the light emitting unit 12 irradiates the subject 20 with pulsed near-infrared light. The light reflected from the subject 20 is collected by the lens 11 and forms an image on the TOF sensor 13. The TOF sensor 13 detects the light reflected from the subject 20 and obtains an electrical signal level by photoelectrically converting it. The TOF sensor 13 changes the phase of the shutter timing pulse multiple times relative to the generation timing of the pulsed near-infrared light generated by the light emitting unit 12. The TOF sensor 13 indirectly calculates the distance to the subject 20 based on the ratio of sensor values ​​obtained at each phase of the shutter timing pulse.

[0016] In this way, the TOF sensor 13 generates a sensor value corresponding to the distance to the subject 20 corresponding to each pixel of each frame. The TOF sensor 13 generates one or more frames each consisting of a plurality of pixels arranged in the horizontal and vertical directions. The TOF sensor 13 generates a sensor value corresponding to the distance to the subject 20 corresponding to each pixel of each frame.

[0017] A direct-type sensor may be used as the TOF sensor 13. The TOF sensor 13 may generate a sensor value corresponding to each pixel of each frame, which directly or indirectly indicates the time from when the light-emitting unit 12 emits near-infrared light to when it receives the reflected light.

[0018] The distance conversion unit 14 converts the sensor values ​​corresponding to each pixel in each frame into distances, and generates a distance image (depth image) made up of distance values ​​corresponding to each pixel in each frame. The distance image is a moving image or a still image. In the case of a moving image, the distance conversion unit 14 generates, for example, 30 distance images per second. The method of converting sensor values ​​into distance values ​​is well known, so a detailed description will be omitted.

[0019] FIG. 2 shows the reflection level of the reflected light when near-infrared light is irradiated onto a white chart, and the reflection level of the reflected light when near-infrared light is irradiated onto a retroreflective material 21. In FIG. 2, in order to grasp the reflection level, the sensor value obtained by the TOF sensor 13 receiving the reflected light is shown as a code value representing the reflection level. The reflection level when near-infrared light is irradiated onto a white chart attenuates as the distance from the TOF camera 101 to the white chart increases. The reflection level when near-infrared light is irradiated onto the retroreflective material 21 is significantly higher than the reflection level from the white chart and varies greatly depending on the distance. Moreover, the reflection level becomes too high above a certain distance, saturating and reaching a constant value at the saturation level.

[0020] If the amount of near-infrared light that light-emitting unit 12 irradiates subject 20 is reduced so that the reflection level does not become saturated, the reflection level of light reflected from a normal subject that does not have retroreflective material 21 will be low, making it impossible to measure distance or reducing the accuracy of distance measurement. Therefore, the amount of near-infrared light that light-emitting unit 12 irradiates subject 20 cannot be reduced.

[0021] TOF sensor 13 is configured to output a sensor value of 0 when the reflection level is saturated. Therefore, distance conversion unit 14 cannot calculate the distance measurement value of a pixel whose reflection level is saturated. Even if TOF sensor 13 is not configured to output a sensor value of 0 when the reflection level is saturated and instead outputs the saturated value as the sensor value, distance conversion unit 14 cannot correctly calculate the distance measurement value of a pixel whose reflection level is saturated.

[0022] Therefore, distance correction unit 15 corrects the distance measurement image output from distance conversion unit 14 as follows: Distance conversion unit 14 supplies distance correction unit 15 with a distance measurement image of each frame, for example, 640 pixels horizontally and 480 pixels vertically.

[0023] 3, distance correction unit 15 divides the distance measurement image of each frame into multiple sections S. As an example, each section S has 28 pixels in the horizontal and vertical directions, but the number of pixels in the horizontal and vertical directions may be different, such as 24 pixels in the horizontal direction and 32 pixels in the vertical direction.

[0024] When the ranging image of each frame, which is 640 pixels horizontally and 480 pixels vertically, is divided into sections S of 28 pixels horizontally and vertically, a first fractional region of less than 28 pixels horizontally occurs, and a second fractional region of less than 28 pixels vertically occurs. In such a case, as shown in Fig. 4, the distance correction unit 15 sets, for example, an enlarged section S1 of 52 pixels horizontally and 28 pixels vertically at the right end of each frame by combining the first fractional region generated at the right end with the section S adjacent to it on its left, excluding the enlarged section S3 at the lower right corner.

[0025] Furthermore, the distance correction unit 15 sets an enlarged section S2 of 28 pixels horizontally and 32 pixels vertically at the bottom of each frame, for example, by combining the second fractional area occurring at the bottom, excluding the enlarged section S3, with the section S adjacent thereto above. The distance correction unit 15 sets an enlarged section S3 of 52 pixels horizontally and 32 pixels vertically at the bottom right corner.

[0026] In this way, distance correction unit 15 divides each frame into sections S each having a pixel count of (x × y), where x and y are integers equal to or greater than 2, and where x is the number of pixels in the horizontal direction and y is the number of pixels in the vertical direction. When a first fractional area having a pixel count less than x occurs in the horizontal direction of each frame, distance correction unit 15 may set horizontally expanded sections S1 and S3 by merging the first fractional area with section S having a pixel count of (x × y) that is adjacent to the left or right of the first fractional area.

[0027] When a second fractional area having a pixel count of less than y occurs in the vertical direction of each frame, the distance correction unit 15 may set vertically enlarged sections S2 and S3 by merging the second fractional area with a section S having a pixel count of (x × y) adjacent to the upper or lower side of the second fractional area.

[0028] In section S shown in FIG. 5, the six black pixels are pixels for which the sensor value output by the TOF sensor 13 is 0 and for which no distance measurement value has been obtained. The distance correction unit 15 calculates the average value of the distance measurement values ​​of the pixels in section S excluding the pixels for which no distance measurement value has been obtained. The distance correction unit 15 assigns the average value to the six black pixels for which no distance measurement value has been obtained. This results in a state in which distance measurement values ​​are associated with all pixels in section S. If any of the six black pixels contains an invalid value that does not indicate a correct distance measurement value, the distance correction unit 15 simply replaces the invalid value with the average value. Assigning the average value includes replacing the invalid value with the average value.

[0029] 6, the blacked-out sections Sb are sections S in which the sensor value output from the TOF sensor 13 is 0 for all pixels within the sections S and no distance measurement values ​​have been obtained. The distance correction unit 15 assigns to each pixel of the sections Sb in which no distance measurement values ​​have been obtained for all pixels the average value of the distance measurement values ​​obtained in the section Sa adjacent above (directly above) the section Sb.

[0030] If there are no pixels in the section Sa for which no distance measurement values ​​have been obtained, the average distance measurement values ​​obtained in the section Sa is the average distance measurement values ​​of all pixels in the section Sa. As in Figure 5, if there are pixels in the section Sa for which no distance measurement values ​​have been obtained, the average distance measurement values ​​obtained in the section Sa is the average distance measurement values ​​of the pixels excluding the pixels in the section Sa for which no distance measurement values ​​have been obtained.

[0031] Regardless of whether or not there is an adjacent section Sa above, distance correction unit 15 may assign to each pixel of section Sb the average value of the distance measurements obtained in section Sc adjacent to the left of section Sb or section Sd adjacent to the right of section Sb. If there is no adjacent section Sa above, distance correction unit 15 assigns to each pixel of section Sb the average value of the distance measurements obtained in section Sc or Sd.

[0032] As shown in Figure 7, the distance correction unit 15 may use different methods for selecting sections S to correct sections S in which distance measurements have not been obtained for all pixels in the left and right regions of each frame.

[0033] In Figure 7, the blacked-out sections Sf and Si are sections S where the sensor value output from the TOF sensor 13 is 0 for all pixels within the section S and no distance measurement value is obtained. If the 640 horizontal pixels of each frame are divided into sections S of 28 pixels each in the horizontal and vertical directions, 22 sections S (including the expanded section S1) are set in the horizontal direction. If 11 sections S are assigned to the left side of each frame in the horizontal direction, the left side of each frame becomes an area of ​​308 pixels in the horizontal direction, as shown in Figure 7. The right side of each frame becomes an area of ​​332 pixels in the horizontal direction consisting of the remaining 11 sections S.

[0034] 7, in the horizontal 308-pixel region on the left side of each frame, distance correction unit 15 assigns to each pixel of section Sf, for which no distance measurement values ​​have been obtained, the average value of the distance measurement values ​​obtained in section Sg, which is adjacent to the right side of the section Sf. The same applies if there is another section S, for which no distance measurement values ​​have been obtained, in the horizontal 308-pixel region on the left side.

[0035] In the horizontal 332-pixel region on the right side of each frame, distance correction unit 15 assigns to each pixel of section Si, for which no distance measurement values ​​have been obtained, the average value of the distance measurement values ​​obtained in section Sh, which is adjacent to the left of the section Si. The same applies if there is another section S, for which no distance measurement values ​​have been obtained, in the horizontal 332-pixel region on the right side.

[0036] In this way, distance correction unit 15 divides the distance measurement image of each frame into multiple sections S. As shown in Fig. 5, there may be pixels in one of the sections S in each frame for which no distance measurement value has been obtained. Distance correction unit 15 corrects the distance measurement image by assigning to the pixel for which no distance measurement value has been obtained the average value of the distance measurement values ​​of the pixels in that section S excluding the pixels for which no distance measurement value has been obtained.

[0037] 6 or 7, each frame may contain a section S in which distance measurement values ​​have not been obtained for all pixels within the section S. Distance correction unit 15 corrects the distance measurement image by assigning to all pixels in the section S in which distance measurement values ​​have not been obtained the average value of the distance measurement values ​​of the pixels in the section S adjacent to the upper, left, or right side of the section S.

[0038] Distance correction unit 15 calculates the average value of the distance measurement values ​​for each section S in the topmost horizontal row of sections S in each frame, in the order from the leftmost section S to the rightmost section S. After the average value of the distance measurement values ​​for all sections S in the topmost row has been calculated, distance correction unit 15 assigns the average value to pixels in section S for which no distance measurement value has been obtained or to all pixels in section S for which no distance measurement value has been obtained, in the order from the leftmost section S to the rightmost section S, as necessary.

[0039] In parallel with the correction for the top row of sections S, distance correction unit 15 calculates the average value of the distance measurement values ​​for each section S in the second horizontal row of sections S, in the order from the leftmost section S to the rightmost section S. Once the average value of the distance measurement values ​​for all sections S in the second row has been calculated, distance correction unit 15 assigns the average value to pixels in sections S for which no distance measurement values ​​have been obtained or to all pixels in sections S for which no distance measurement values ​​have been obtained, in the order from the leftmost section S to the rightmost section S, as necessary.

[0040] In parallel with the correction for the section S in the second row, distance correction unit 15 calculates the average value of the distance measurement values ​​for each section S in the third row of horizontal sections S, starting from the leftmost section S to the rightmost section S. Thereafter, distance correction unit 15 repeats the same operation up to the lowest horizontal section S.

[0041] The example described above is an example in which the section S in each row is processed from the top to the bottom of each frame. In this example, the distance correction unit 15 corrects the distance measurement image by assigning the average value of the distance measurement values ​​of the pixels in the section S adjacent to the upper, left, or right side of the section S in which distance measurement values ​​have not been obtained for all pixels. As another example, the section S in each row may be processed from the bottom to the top of each frame. In this case, the distance correction unit 15 corrects the distance measurement image by assigning the average value of the distance measurement values ​​of the pixels in the section S adjacent to the lower, left, or right side of the section S in which distance measurement values ​​have not been obtained for all pixels. In this way, the distance correction unit 15 can correct the distance measurement image by assigning the average value of the distance measurement values ​​of the pixels in the section S adjacent to the upper, lower, left, or right side of the section S in which distance measurement values ​​have not been obtained for all pixels.

[0042] According to the TOF camera 101 and the ranging method executed by the TOF camera 101 described above, even if there are pixels in which the sensor value of the TOF sensor 13 that detects reflected light is saturated due to the presence of retroreflective material 21 in the subject 20, it is possible to obtain ranging values ​​for the saturated pixels. According to the TOF camera 101 and the ranging method executed by the TOF camera 101, it is possible to correct the ranging image in either a state in which ranging values ​​are not obtained for some pixels in the section S or a state in which ranging values ​​are not obtained for all pixels in the section S.

[0043] Second Embodiment 8 shows a TOF camera 102, which is a distance measuring device according to the second embodiment. In addition to the configuration of the TOF camera 101, the TOF camera 102 includes a mode selection unit 16 and a mode control unit 17. As with the TOF camera 101, the distance correction unit 15 divides the distance measurement image of each frame into multiple sections S in order to correct pixels for which no distance measurement values ​​have been obtained. The method of correcting the distance measurement image in the distance correction unit 15 is the same as that in the TOF camera 101.

[0044] Mode selection unit 16 selects a mode according to the distance from light-emitting unit 12 to subject 20 in accordance with a user operation. Mode selection unit 16 may be a menu for selecting a mode, or may be a button for selecting a mode. The modes according to distance include, for example, three modes: a close-distance mode of 30 cm or more and less than 1.5 m, a medium-distance mode of 1.5 m or more and less than 3 m, and a long-distance mode of 3 m or more and less than 8 m.

[0045] The mode control unit 17 controls the distance correction unit 15 to change the size of the section S according to the mode selected by the mode selection unit 16. The mode control unit 17 controls the light-emitting unit 12 to change the amount of near-infrared light emitted from the light-emitting unit 12 according to the mode selected by the mode selection unit 16. The mode control unit 17 may increase the amount of near-infrared light in the order of short-distance mode, medium-distance mode, and long-distance mode. The mode control unit 17 may change the shutter timing of the TOF sensor 13 according to the mode selected by the mode selection unit 16.

[0046] In FIG. 9, (a) conceptually shows a distance measurement image of the subject 20 captured by the TOF camera 102 in close-distance mode. A large retroreflective material 21 is present within the frame. When the mode selection unit 16 sets the close-distance mode, the mode control unit 17 sets the amount of near-infrared light to a relatively small amount so that the sensor value does not saturate even if, for example, a white chart with a reflectance of 94% is positioned within the close-distance measurement range of the subject 20. As a result, the near-infrared light is reflected with high intensity only from a small area of ​​the retroreflective material 21, and only a small number of pixels saturate the sensor value of the TOF sensor 13. Therefore, the area in the frame where no distance measurement value is obtained due to sensor value saturation is represented by a small area shaded in black.

[0047] In the close-distance mode, it is preferable to make the section S small. As an example, the mode control unit 17 controls the distance correction unit 15 to set the section S to 20 pixels in the horizontal and vertical directions. By the mode control unit 17 controlling the distance correction unit 15 to set the section S to a small size in the close-distance mode, the distance measurement image is corrected so that there are no areas where distance measurement values ​​are not obtained, as shown in (b) of FIG.

[0048] 10, (a) conceptually shows a distance measurement image captured by the TOF camera 102 in medium distance mode of the subject 20. In the medium distance mode, the mode control unit 17 sets the amount of near-infrared light to a level greater than that in the short distance mode so that the near-infrared light irradiated on the subject 20 does not become weaker due to the longer distance measurement range than in the short distance mode. As the distance from the TOF camera 102 to the subject 20 increases, the retroreflective material 21 is captured small within the frame. Because the near-infrared light is reflected with high intensity by the entire retroreflective material 21, the sensor value becomes saturated, and therefore no distance measurement value is obtained for the entire retroreflective material 21, as if the entire retroreflective material 21 is painted black.

[0049] In the medium distance mode, it is preferable to make the section S larger than the section S in the short distance mode. As an example, the mode control unit 17 controls the distance correction unit 15 to set the section S to 28 pixels in the horizontal and vertical directions. By the mode control unit 17 controlling the distance correction unit 15 to set the section S in the medium distance mode to be larger than the section S in the short distance mode, the distance measurement image is corrected so that there are no areas of the entire retroreflective material 21 for which distance measurement values ​​have not been obtained, as shown in (b) of Figure 10.

[0050] In FIG. 11, (a) conceptually shows a distance measurement image of the subject 20 captured by the TOF camera 102 in long-distance mode. The mode control unit 17 sets the amount of near-infrared light in long-distance mode to a greater amount than in medium-distance mode. As the distance from the TOF camera 102 to the subject 20 becomes longer, the retroreflective material 21 is captured even smaller within the frame. Because the sensor value saturates due to the high intensity of near-infrared light reflected from the entire retroreflective material 21, no distance measurement value is obtained over the entire retroreflective material 21, as if the entire retroreflective material 21 is painted black. The area where no distance measurement value is obtained is smaller than that in medium-distance mode.

[0051] In the long distance mode, it is preferable to make the section S smaller than the section S in the medium distance mode. As an example, the mode control unit 17 controls the distance correction unit 15 to set the section S to 18 pixels in the horizontal and vertical directions. By the mode control unit 17 controlling the distance correction unit 15 to set the section S in the long distance mode smaller than the section S in the medium distance mode, the distance measurement image is corrected so that there are no areas of the entire retroreflective material 21 for which distance measurement values ​​have not been obtained, as shown in (b) of Figure 11.

[0052] In the TOF camera 102, the mode selection unit 16 may switch the mode between short-distance mode, medium-distance mode, and long-distance mode for each frame, and the mode control unit 17 may control the distance correction unit 15 to set the size of the section S according to the short-distance mode, medium-distance mode, or long-distance mode for each frame.

[0053] According to the TOF camera 102 and the ranging method executed by the TOF camera 102 described above, in addition to the effects achieved by the first embodiment, ranging images can be accurately corrected in accordance with each of the short-distance mode, medium-distance mode, and long-distance mode.

[0054] Third Embodiment 12 shows a TOF camera 103, which is a distance measuring device according to the third embodiment. Instead of the lens 11 in the TOF camera 101, the TOF camera 103 has an interchangeable lens 311 that is detachable by a lens mount 312. In addition to the configuration of the TOF camera 101, the TOF camera 103 also has a focal length selection unit 18. The lens mount 312 may be a lens mount standard, for example, a C-mount.

[0055] Similar to the TOF camera 101, the distance correction unit 15 divides the distance measurement image of each frame into multiple sections S in order to correct pixels for which no distance measurement values ​​have been obtained. The method of correcting the distance measurement image in the distance correction unit 15 is similar to that in the TOF camera 101.

[0056] When the user changes the interchangeable lens 311, the user selects the focal length of the interchangeable lens 311 attached to the lens mount 312 using the focal length selection unit 18. As an example, assume that the focal length of the first interchangeable lens 311 is 14 mm and the focal length of the second interchangeable lens 311 is 280 mm. When the second interchangeable lens 311 is attached to the lens mount 312, the size of the subject 20 to be photographed is twice as large as when the first interchangeable lens 311 is attached to the lens mount 312.

[0057] Therefore, the distance correction unit 15 changes the size of the section S depending on the focal length of the interchangeable lens 311 being used. For example, suppose that the distance correction unit 15 sets the section S to 20 pixels in the horizontal and vertical directions when using a first interchangeable lens 311 with a focal length of 14 mm. In this case, the distance correction unit 15 may set the section S to 40 pixels in the horizontal and vertical directions when using a second interchangeable lens 311 with a focal length of 28 mm.

[0058] An electronic contact may be provided on the lens mount 312, and the distance correction unit 15 may be configured to automatically obtain the focal length of the interchangeable lens 311 from the electronic contact. In this case, the focal length selection unit 18 may be omitted. The electronic contact transmits the focal length of the interchangeable lens 311 to the distance correction unit 15. The distance correction unit 15 may change the size of the section S according to the received focal length of the interchangeable lens 311.

[0059] According to the TOF camera 103 and the distance measurement method executed by the TOF camera 103, in addition to the effects achieved by the first embodiment, it is possible to accurately correct the distance measurement image in accordance with the focal length of each interchangeable lens 311.

[0060] The second and third embodiments may be combined. In this case, the distance correction unit 15 determines the size of the section S in accordance with each of the close-distance mode, the medium-distance mode, and the long-distance mode, and also determines the size of the section S in accordance with the focal length of each interchangeable lens 311.

[0061] <Fourth embodiment> 13 shows a TOF camera 104, which is a distance measuring device according to the fourth embodiment. The TOF camera 104 has a zoom lens 411 attached by a lens mount 412, instead of the lens 11 in the TOF camera 101. The lens mount 412 may be, for example, a C-mount. The lens mount 412 has electronic contacts 413. The electronic contacts 413 transmit the focal length of the zoom lens 411 to the distance correction unit 15.

[0062] As an example, suppose that the focal length of the zoom lens 411 at the wide end is 14 mm, and the zoom lens 411 is zoomed to a focal length of 28 mm. At this time, the size of the subject 20 being photographed will be twice as large as when the zoom lens 411 is at the wide end.

[0063] Therefore, distance correction unit 15 changes the size of section S according to the received focal length of zoom lens 411. For example, assume that distance correction unit 15 sets section S to 20 pixels in the horizontal and vertical directions when zoom lens 411 is at the wide end. When the focal length of zoom lens 411 becomes 28 mm, distance correction unit 15 sets section S to 40 pixels in the horizontal and vertical directions.

[0064] It is not essential to provide electronic contacts 413 that transmit the focal length of zoom lens 411 to distance correction unit 15, and to have distance correction unit 15 change the size of section S according to the focal length of zoom lens 411 received from electronic contacts 413. Distance correction unit 15 may change the size of section S according to the focal length of zoom lens 411. It is preferable to provide electronic contacts 413 that transmit the focal length of zoom lens 411 to distance correction unit 15, and to have distance correction unit 15 change the size of section S according to the focal length of zoom lens 411 received.

[0065] According to the TOF camera 104 and the ranging method executed by the TOF camera 104, in addition to the effects achieved by the first embodiment, even if the focal length is changed by the zoom lens 411, the ranging image can be accurately corrected according to the focal length.

[0066] The second embodiment and the fourth embodiment may be combined. In this case, the distance correction unit 15 determines the size of the section S corresponding to each of the close distance mode, the medium distance mode, and the long distance mode, and also determines the size of the section S corresponding to the focal length of the zoom lens 411.

[0067] The present invention is not limited to the first to fourth embodiments described above, and various modifications are possible without departing from the gist of the present invention. [Explanation of symbols]

[0068] 11 Lens 12 Light-emitting part 13 TOF sensor 14 Distance conversion unit 15 Distance correction unit 16 Mode selection section 17 Mode control section 18 Focal length selection section 20 Subject (object) 21 Retroreflective material 30 Distance measurement device 101~104 TOF cameras 311 Interchangeable Lens 312,412 lens mount 411 Zoom Lens 413 Electronic Contacts

Claims

1. a light emitting unit that irradiates light onto an object to be measured; a sensor that detects light reflected by the object, generates one or more frames each consisting of a plurality of pixels arranged in horizontal and vertical directions, and generates a sensor value corresponding to the distance to the object for each pixel in each frame; a distance conversion unit that converts the sensor value corresponding to each pixel of each frame into a distance and generates a distance measurement image made up of distance measurement values ​​corresponding to each pixel of each frame; a distance correction unit that divides the distance measurement image of each frame into a plurality of sections, and when a pixel for which a distance measurement value has not been obtained exists in any of the sections, corrects the distance measurement image by assigning to the pixel for which a distance measurement value has not been obtained an average value of the distance measurement values ​​of pixels excluding the pixel for which a distance measurement value has not been obtained in any of the sections; A ranging device comprising:

2. 2. The distance measurement device according to claim 1, wherein when there is a section in which distance measurement values ​​have not been obtained for all pixels within the section, the distance correction unit corrects the distance measurement image by assigning to all pixels of the section in which distance measurement values ​​have not been obtained for all pixels the average value of distance measurement values ​​of pixels in adjacent sections above, below, to the left, or to the right of the section in which distance measurement values ​​have not been obtained for all pixels.

3. 3. The distance measuring device according to claim 1, wherein x and y are integers of 2 or greater, each frame is divided into sections having a pixel count of (x × y), where x is a horizontal pixel count and y is a vertical pixel count, and when a first fractional area having a pixel count less than x occurs in the horizontal direction of each frame, a horizontally expanded section is set by combining the first fractional area with the section having a pixel count of (x × y) adjacent to the left or right of the first fractional area.

4. 4. The distance measuring device of claim 3, wherein when a second fractional area having a pixel count of less than y occurs in the vertical direction of each frame, a vertically expanded section is set by merging the second fractional area with a section having the pixel count of (x x y) adjacent to the upper or lower side of the second fractional area.

5. Irradiating the object to be measured with light emitted from the light emitting unit; Detecting light reflected by the object, generating one or more frames each consisting of a plurality of pixels arranged in horizontal and vertical directions, and generating a sensor value according to the distance to the object corresponding to each pixel in each frame; converting the sensor values ​​corresponding to the pixels of each of the frames into distances to generate a distance measurement image made up of distance measurement values ​​corresponding to the pixels of each of the frames; The distance measurement image of each frame is divided into a plurality of sections, and when a pixel for which a distance measurement value has not been obtained exists in any of the sections, the pixel for which a distance measurement value has not been obtained is assigned an average value of the distance measurement values ​​of pixels excluding the pixel for which a distance measurement value has not been obtained in any of the sections, thereby correcting the distance measurement image. Distance measurement method.

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