Distance measurement method, distance measurement device, and program

Abstract

A distance measurement method according to the present disclosure includes: causing a computer to shift an irradiation spot of laser light from a position of a light-receiving pixel corresponding to the irradiation spot such that the laser light is emitted to the shifted irradiation spot; causing reflected light, from an object to be measured, of the emitted laser light to be received by the light-receiving pixel corresponding to the irradiation spot; and measuring, on the basis of the light emission timing of the laser light and the light reception timing of the reflected light, the distance to the object to be measured.

Description

Distance measurement method, distance measurement device, and program

[0001] The present disclosure relates to a distance measurement method, a distance measurement device, and a program.

[0002] 2. Description of the Related Art In recent years, AGVs (Automated Guided Vehicles) and AMRs (Autonomous Mobile Robots) have become known.

[0003] Such AGVs and AMRs use location recognition markers (called landmarks) to identify their own positions. Landmarks are generally made of printed matter or retroreflective material.

[0004] Retroreflective materials reflect light from a light source in a direction that is roughly parallel to the optical path of the incident light over a wide angle of incidence. This type of reflection is called retroreflection.

[0005] When using retroreflective materials to measure distances for the robot's self-localization, an error in distance measurement called range walking occurs. This error occurs because the time it takes for the intensity to exceed the detection threshold is shortened due to the strong reflected light from the retroreflective material, resulting in an error in depth and the occurrence of lens ghosting.

[0006] If such an error occurs in the distance measurement, the robot's own position will be recognized incorrectly.

[0007] Conventionally, in order to prevent strong reflected light from a retroreflective material, a technique has been disclosed in which a plurality of light sources with different irradiation angles and half-value angles of irradiated light are used.

[0008] Japanese Patent Application Laid-Open No. 2017-90202

[0009] However, this technology simply changes the way light from the light source spreads, so if the area of ​​the retroreflective material is large, strong reflected light will return, and it cannot solve the problem of preventing strong reflected light.

[0010] The present disclosure has been made in consideration of the above-mentioned situation, and provides a distance measurement method, a distance measurement device, and a program that can accurately measure distance even when a large-area retroreflective material is used as a marker.

[0011] The distance measurement method disclosed herein includes a computer shifting an irradiation spot of laser light from the position of a light-receiving pixel corresponding to the irradiation spot, emitting the laser light to the shifted irradiation spot, receiving reflected light from a measurement object in response to the emitted laser light at the light-receiving pixel corresponding to the irradiation spot, and measuring the distance to the measurement object based on the timing of emitting the laser light and the timing of receiving the reflected light.

[0012] 9 is a diagram showing a state in which a retroreflective material is attached to a window glass installed on a wall. FIG. 10 is a diagram showing the light intensity of the reflected light when infrared light is emitted to the wall, window glass, and retroreflective material shown in FIG. 1. FIG. 11 is a diagram for explaining diffuse reflection. FIG. 12 is a diagram for explaining specular reflection. FIG. 13 is a diagram for explaining retroreflection. FIG. 14 is a diagram showing a corner cube type retroreflective material. FIG. 15 is a diagram showing the relationship between incident light incident on a corner cube type retroreflective material and the reflected light. FIG. 16 is a diagram showing the relationship between incident light incident on a glass bead type retroreflective material and the reflected light. FIG. 17 is a diagram showing a state in which a retroreflective material is attached to the back of a chair. FIG. 18 is a diagram showing a background light image, a depth image, and a reflected light image around the chair to which the retroreflective material shown in FIG. 9 is attached. FIG. 19 is a diagram showing the area around the chair to which the retroreflective material is attached using a point cloud (point cloud data). FIG. 19 is a diagram showing an example of a distance measurement sensor. FIG. 19 is a functional block diagram of a TOF camera according to a first embodiment. FIG. 19 is a diagram showing an example for explaining the relationship between the light-receiving pixels and the illumination spot of the TOF camera according to the first embodiment. 1 is a diagram showing a first example of the direction of laser light scanning by the light-emitting unit and the light-receiving unit when the light-emitting pixel and the light-receiving pixel match. FIG. 2 is a diagram showing a second example of the direction of laser light scanning by the light-emitting unit and the light-receiving unit when the light-emitting pixel and the light-receiving pixel match. FIG. 3 is a diagram showing an example of the relationship between a robot equipped with a TOF camera according to the first embodiment and a subject, as viewed from above. FIG. 4 is a diagram showing the configuration of a robot equipped with a TOF camera according to the first embodiment. FIG. 5 is a flowchart for explaining the operation of a TOF camera according to the first embodiment. FIG. 6 is a functional block diagram of a TOF camera according to the second embodiment. FIG. 7 is a diagram showing the configuration of a robot equipped with a TOF camera according to the second embodiment. FIG. 8 is a flowchart for explaining the operation of a TOF camera according to the second embodiment. FIG. 9 is a diagram for explaining a case where a camera mounted on a conventional vehicle recognizes a retroreflective material. FIG. 10 is a diagram for explaining a low-reflection mode according to the first embodiment. FIG. 11 is a diagram for explaining a low-reflection mode according to the first embodiment. FIG. 12 is a timing chart for explaining a synchronization signal for emitting and receiving light by the camera.10 is a diagram for explaining a case where a camera mounted on a vehicle according to a third embodiment recognizes retroreflective material S. FIG. 11 is a diagram for explaining a case where a retroreflective material is recognized using a light source and a camera mounted on a vehicle according to a fourth embodiment. FIG. 12 is a diagram showing switching between normal mode and low-reflection mode of a camera mounted on a vehicle according to a fifth embodiment. FIG. 13 is a functional block diagram of a TOF camera 650 according to a sixth embodiment. FIG. 14 is a flowchart for explaining the operation of a TOF camera according to a sixth embodiment. FIG. 15 is a hardware configuration diagram showing an example of a computer that realizes a TOF camera, which is an information processing device according to the first to sixth embodiments, and a robot arithmetic device.

[0013] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted. The description will be given in the following order.

[0014] 1. Regarding Retroreflective Materials 2. Embodiments 2.1. First Embodiment 2.1.1. Configuration 2.1.1.1. Distance Measuring Sensor 2.1.1.2. Functional Block Diagram of TOF Camera 150 2.1.1.2.1. Relationship Between Light-Receiving Pixels and Illumination Spot 2.1.1.2.2. Relationship Between TOF Camera 150 and Subject T 2.1.1.3. Configuration of Robot Equipped with TOF Camera 150 2.1.2. Operation 2.2. Second Embodiment 2.2.1. Configuration 2.2.1.1.1. Functional Block Diagram of TOF Camera 350 2.2.1.1.2. Configuration of Robot 400 Equipped with TOF Camera 350 2.2.2. Operation 2.2.2.1. Flowchart 2.2.2.2. Low Reflection Mode 2.2.2.3. Timing of light emission and light reception 2.3. Third embodiment 2.4. Fourth embodiment 2.5. Fifth embodiment 2.6. Sixth embodiment 2.6.1. Functional block diagram of TOF camera 650 2.6.2. Flowchart 2.7. Effects 2.8. Other embodiments 2.9. Hardware configuration

[0015] <1. Regarding retroreflective materials> First, we will explain retroreflective materials. Fig. 1 is a diagram showing a state in which a retroreflective material 3 is attached to a window pane 2 installed in a wall 1. Fig. 2 is a diagram showing the light intensity of the reflected light when infrared light is emitted to the wall 1, window pane 2, and retroreflective material 3 shown in Fig. 1.

[0016] As shown in Figure 2, strong reflected light is detected from a certain portion of the retroreflective material 3. Therefore, the retroreflective material 3 is suitable for use as a landmark. However, extremely strong reflected light is detected from the retroreflective material 3. Therefore, as described above, there is a problem in that the depth offset causes errors in distance measurement of the retroreflective material.

[0017] The technology disclosed herein accurately measures the distance to the retroreflective material 3 by weakening the intensity of the reflected light from the retroreflective material 3, even when the reflected light from the retroreflective material 3 is strong.

[0018] Next, retroreflection will be explained by comparing diffuse reflection and specular reflection. Figure 3 is a diagram for explaining diffuse reflection. As shown in Figure 3, diffuse reflection is the component of light reflection that occurs near the surface of a non-metallic material m when incident light i from a light source 10 is incident on the non-metallic material m, excluding specular reflection (reflected light r in Figure 3).

[0019] Fig. 4 is a diagram for explaining specular reflection. Specular reflection occurs at the interface between two materials. Specular reflection follows the law of reflection, and as shown in Fig. 4, the angle of incidence θi and the angle of reflection θr are equal.

[0020] Fig. 5 is a diagram for explaining retroreflection. Retroreflection is a reflection in which incident light i from a light source 10 is reflected in a direction substantially along the optical path of the incident light i (reflected light r in Fig. 5) over a wide irradiation angle, as shown in Fig. 5.

[0021] Retroreflective materials that provide such retroreflection include corner cube type retroreflective materials and glass bead type retroreflective materials.

[0022] Fig. 6 shows a corner cube retroreflective material c. Corner cube retroreflective material c forms a cube corner with an incident surface perpendicular to the cube diagonal, as shown in Fig. 6. The cube corner has three mirror surfaces mr1, mr2, and mr3 that form 90° angles with each other.

[0023] 7 is a diagram showing the relationship between incident light i and reflected light r that is incident on corner cube retroreflective material C. As shown in Fig. 7, when incident light i is incident on corner cube retroreflective material C, all reflected light r is reflected in the direction of incident light i, regardless of the incident direction.

[0024] Figure 8 shows the relationship between incident light i incident on a glass bead-type retroreflective material c and reflected light r. As shown in Figure 8, the glass bead-type retroreflective material c has a release paper 11, a synthetic resin layer 13 formed on top of the release paper 11 via an adhesive 12, and a surface film 14 (colorant) formed on the synthetic resin layer 13. Here, the release paper 11 is a laminated paper in which a thin film-like resin is laminated on paper to give it properties such as releasability, water resistance, heat resistance, and abrasion resistance.

[0025] In addition, a reflective layer 15, a focusing layer 16, and glass spheres 17 are provided between the synthetic resin layer 13 and the surface film 14. The reflective layer 15 is formed on top of the synthetic resin layer 13. The focusing layer 16 is formed on top of the reflective layer 15. The focusing layer 16 covers the bottom of the glass spheres 17. As shown in Figure 8, the glass cube-shaped retroreflective material c reflects all reflected light r in the direction of incident light i.

[0026] Next, we will explain erroneous detection of the depth of retroreflective material c. FIG. 9 is a diagram showing a state in which retroreflective material c is attached to the backrest of a chair ch. FIG. 10 is a diagram showing a background light (ambient) image, a depth image, and a reflected light (intensity) image of the surroundings of the chair ch to which the retroreflective material c shown in FIG. 9 is attached. As shown in FIG. 10, in the background light image, the intensity of light from retroreflective material c is stronger than that of the surroundings. In the reflected light image, the intensity of light from retroreflective material c is relatively stronger than that of the surroundings. Therefore, the light intensities of the background light image and reflected light image affect the depth of retroreflective material c in the depth image, which can indirectly lead to erroneous detection of the depth.

[0027] 11 is a diagram showing a point cloud (point cloud data) of the area around a chair ch to which a retroreflective material c is attached. In the example shown in FIG. 11 , the depth of the retroreflective material c is shown as approximately 30 cm behind the chair ch in the point cloud image. The distance measuring device of the present disclosure can appropriately display the depth of the retroreflective material c and accurately measure the distance to the retroreflective material c.

[0028] 2. Embodiments 2.1. First embodiment In the first embodiment, a distance measurement method using one TOF (Time of Flight) camera will be described. In the first embodiment, a light emitting unit of the TOF camera changes the irradiation spot to perform distance measurement, thereby accurately measuring the distance to a measurement target.

[0029] Here, the term "irradiation spot" refers to the position (x1, y1) of a light-emitting pixel of the light-emitting unit that is irradiated with the emitted laser light. The term "light-emitting pixel" refers to an element that is irradiated with the laser light corresponding to the irradiation spot.

[0030] <2.1.1. Configuration> <2.1.1.1. Distance Measuring Sensor> First, a technical overview of the distance measuring sensor of the TOF camera will be described.

[0031] 12 is a diagram showing an example of a distance measurement sensor 102. The distance measurement sensor 102 includes a light-emitting unit 110 that emits light and a light-receiving unit 120 that receives the light emitted by the light-emitting unit 110. The distance measurement sensor 102 measures the distance Lx from the distance measurement sensor 102 to the object X by emitting light from the light-emitting unit 110 to the object X and receiving the light reflected from the object X with the light-receiving unit 120. The light-receiving side of the light-receiving unit 120 is provided with, for example, a lens structure that efficiently collects the light reflected from the object X. Furthermore, the light-emitting side of the light-emitting unit 110 is provided with, for example, a diffuser so that light can be irradiated onto the entire object X.

[0032] Such a distance measuring sensor 102 measures the round-trip time of light to the object X, assuming that the light emission timing indicating the start of light irradiation by the light emitting unit 110 and the light reception timing indicating the start of light reception by the light receiving unit 120 are known. The distance measuring sensor 102 calculates the distance from the distance measuring sensor 102 to the object X by multiplying the round-trip time of light by the speed of light and dividing the result by 2.

[0033] However, if the object X is made of a retroreflective material, the reflected light from the retroreflective material will be too strong, causing lens ghosting. Therefore, if a retroreflective material is used as a marker for the robot to recognize its own position, the light rising from the light receiving unit 120 will be fast, shortening the time it takes to exceed the detection threshold, and increasing the error in the measured distance due to range walking.

[0034] In the measurement method disclosed herein, a computer emits laser light from light-emitting unit 110 at an irradiation spot shifted from the light-receiving pixel corresponding to the irradiation spot, receives the light reflected from the emitted laser light from the retroreflective material at light-receiving unit 120, and measures the distance to the retroreflective material based on the emission timing of the light and the reception timing of the reflected light. In this way, the measurement method disclosed herein can suppress the intensity of the reflected light from the retroreflective material and can accurately measure the distance to the retroreflective material.

[0035] 13 is a functional block diagram of the TOF camera 150 according to the first embodiment. As shown in Fig. 13, the TOF camera 150 includes a synchronization signal generation unit 151, an irradiation spot designation unit 152, a light emission unit 153, a light reception unit 154, a signal processing unit 155, and an image output unit 156.

[0036] The synchronization signal generating unit 151 outputs a synchronization pulse signal indicating the timing of emitting laser light to the light emitting unit 153. The synchronization signal generating unit 151 also outputs a synchronization pulse signal indicating the timing of receiving laser light to the light receiving unit 154. The synchronization pulse signal may be a timestamp.

[0037] The irradiation spot designation unit 152 designates an irradiation spot of the laser light to be emitted by the light emitting unit 153. Furthermore, when the brightness of a light-receiving pixel of the light-receiving unit 154 corresponding to the irradiation spot exceeds a threshold value, the irradiation spot designation unit 152 designates the irradiation spot of the emitted laser light so as to be shifted from the position of the light-receiving pixel corresponding to the irradiation spot.

[0038] Typically, the positions of the light-emitting pixels of the light-emitting unit 153 in the illumination spot are the same as the positions of the light-receiving pixels of the light-receiving unit 154 (illumination spot = light-emitting pixel (X, Y) = light-receiving pixel (X, Y)). Even when a retroreflective material is used on the subject and the reflected light received by the light-receiving pixel is strong, the technology disclosed herein makes the positions of the illumination spot and the light-receiving pixel different, preventing strong reflected light and measuring the accurate distance to the retroreflective material.

[0039] In the first embodiment, when the brightness of the light-receiving pixel of the light-receiving unit 154 corresponding to the irradiation spot exceeds a threshold, the irradiation spot designation unit 152 designates the irradiation spot of the emitted laser light to be shifted from the position of the light-receiving pixel corresponding to the irradiation spot (irradiation spot ≠ light-receiving pixel (X, Y)). In other words, when the brightness of the light-receiving pixel of the light-receiving unit 154 corresponding to the irradiation spot exceeds a threshold, the irradiation spot designation unit 152 instructs the light-emitting unit 153 to emit light to a light-emitting pixel at a position different from the light-receiving pixel.

[0040] The method of shifting the irradiation spot (light-emitting pixel) relative to the light-receiving pixel is not particularly limited. For example, the irradiation spot and the light-receiving pixel may be shifted in a point-symmetric manner. When shifting in a point-symmetric manner, for example, the irradiation spot designation unit 152 may instruct the light-receiving unit 154 to irradiate the irradiation spot in the upper left of the screen with laser light and to receive the reflected light at the light-receiving pixel in the lower right of the screen.

[0041] If the luminance of the reflected light received by the pixel of interest (light-receiving pixel) does not exceed a threshold value, the illumination spot instruction unit 152 instructs the light-emitting unit 153 to illuminate the illumination spot of the light-emitting pixel at the same position as the light-receiving pixel.

[0042] If the brightness of the pixel of interest (light-receiving pixel corresponding to the irradiation spot) does not exceed the threshold, the irradiation spot designation unit 152 designates the position of the light-receiving pixel corresponding to the irradiation spot to the light-receiving unit 154 .

[0043] Similarly, the irradiation spot designation unit 152 designates to the light receiving unit 154 the position of the light receiving pixel corresponding to the irradiation spot that receives the reflected light of the laser light emitted from the retroreflective material at a position shifted from the irradiation spot.

[0044] For example, in the case of VGA (Video Graphics Array) resolution, the irradiation spot designation unit 152 designates an irradiation spot with an X coordinate of 0 to 640 and a Y coordinate of 0 to 480. In this case, scanning by the light-emitting unit 153 and the light-receiving unit 154 is performed in order from the top left to the bottom right of the screen.

[0045] In the first embodiment, when the luminance of the pixel of interest exceeds a threshold, the illumination spot designation unit 152 shifts the light-emitting pixels of the illumination spot from the light-receiving pixels to emit light. When the luminance of the pixel of interest exceeds a threshold, the light-emitting unit 153 may not shift the positions of the light-emitting pixels of the illumination spot from the positions of the light-receiving pixels, but the light-receiving unit 154 may shift the positions of the light-receiving pixels from the position of the illumination spot.

[0046] Furthermore, when the luminance of the pixel of interest exceeds a threshold, the irradiation spot designation unit 152 may select a pixel whose luminance value is lower than the threshold, and then designate the position of the selected light-receiving pixel with the lower luminance value as the irradiation spot.

[0047] The light emitting unit 153 emits laser light to the retroreflective material to be measured at the irradiation spot of the laser light specified by the irradiation spot specifying unit 152 at the emission timing of the synchronization pulse signal from the synchronization signal generating unit 151.

[0048] The light emitting unit 153 also outputs the intensity and duration of the emitted laser light to the signal processing unit 155. The light emitting unit 153 is, for example, a VCSEL (Vertical Cavity Surface Emitting Laser).

[0049] When the device disclosed herein uses a VCSEL for the light-emitting unit 153, it is possible to control the position and diameter of the irradiation spot. Therefore, like a projector, the device disclosed herein can illuminate only a specific location. Therefore, when the device disclosed herein detects reflected light that is too strong and exceeds a threshold, it can prevent an increase in the error of the measured distance by irradiating the laser light while avoiding the retroreflective material.

[0050] The light receiving unit 154 receives a light receiving signal from the specified light receiving pixel based on the instruction for the light receiving pixel of the light receiving unit 154 from the irradiation spot instruction unit 152. The light receiving unit 154 also outputs the intensity and time of the light receiving signal from the light receiving pixel that received the light to the signal processing unit 155.

[0051] The light receiving unit 154 may receive light at least by an IR (infrared) method, for example. For example, the light receiving unit 120 may be an RGB sensor including an infrared sensor. The light receiving unit 154 may also be a stacked direct time-of-flight (dToF) distance measurement sensor (2D-LiDAR, 3D-LiDAR) for in-vehicle LiDAR (Light Detection and Ranging) using PAD (Single Photon Avalanche Diode) pixels, or a CMOS (Complementary Metal-Oxide-Semiconductor).

[0052] The signal processing unit 155 calculates and outputs the distance of a single pixel (X, Y) to the retroreflective material based on the intensity and time of the received light signal output from the light receiving unit 154 and the intensity and time of the laser light (light emitting signal) output from the light emitting unit 153.

[0053] In this case, the signal processing unit 155 may generate a histogram with the vertical axis representing frequency and the horizontal axis representing time (proportional to distance), and use this generated histogram to determine the distance of a single pixel (X, Y) to the retroreflective material. Alternatively, the signal processing unit 155 may perform noise removal processing based on the time of the received light signal and the time of the emitted light signal, and then determine the distance of a single pixel (X, Y) to the retroreflective material.

[0054] The image output unit 156 combines the information of all the pixels and outputs it as a single image.

[0055] 14 is a diagram illustrating an example of the relationship between the light-receiving pixels and the illumination spot of the TOF camera 150 according to the first embodiment. As shown in FIG. 14 , the TOF camera 150 includes a lens 161, a light-emitting unit 153, a light-receiving unit 154, and a MEMS (Micro Electro Mechanical Systems) mirror 157.

[0056] Laser light emitted from the light-emitting pixels of the light-emitting unit 153 is reflected by the MEMS mirror 157 and irradiated onto the subject. The positions of the laser light reflected by the MEMS mirror 157 correspond to the positions of the pixels of the image. Fig. 14 shows an example in which the reflected light of the laser light emitted by the light-emitting pixels of the light-emitting unit 153 is collected by the lens 161 and acquired as a single image of 168 (H) x 63 (V) by the light-receiving pixels of the light-receiving unit 154.

[0057] As described above, in the first embodiment, the positions of the light-emitting pixels of the light-emitting unit 153 and the light-receiving pixels of the light-receiving unit 154 are usually the same. However, if the subject is made of a retroreflective material and the brightness of the reflected light from the retroreflective material is high, an error will occur in measuring the distance to the retroreflective material. The distance measurement method of the first embodiment accurately measures the distance to the subject even if the subject is made of a retroreflective material by shifting the position of the irradiation spot from the position of the light-receiving element.

[0058] Fig. 15 is a diagram showing a first example of the direction of laser light scanning by the light-emitting unit 153 and the light-receiving unit 154 when the light-emitting pixels and the light-receiving pixels coincide with each other. As shown in the right diagram of Fig. 15, the light-emitting unit 153 emits the laser light irradiation spot from the upper left pixel to the upper right pixel, from the upper right pixel to the lower left pixel, and from the lower left pixel to the lower right pixel in that order.

[0059] As shown in the left diagram of Figure 15, the light receiving unit 154, like the light emitting unit 153, scans the light receiving pixels in order from the top left pixel to the top right pixel, from the top right pixel to the bottom left pixel, and from the bottom left pixel to the bottom right pixel.

[0060] 16 is a diagram showing a second example of the direction of laser beam scanning by the light-emitting unit 153 and the light-receiving unit 154 when the light-emitting pixels and the light-receiving pixels are aligned. The light-emitting unit 153 scans the laser beam from top to bottom, line by line. The light-receiving unit 154, like the light-emitting unit 153, scans the light-receiving pixels from top to bottom, line by line.

[0061] The distance measurement method of the present disclosure shifts the positions of the light-receiving pixels so that they are different from the irradiation spot when the intensity of the reflected light from the object being measured and received by the light-receiving pixels is strong. By performing this control, the distance measurement method of the first embodiment reduces the effect of strong reflected light on the distance measurement results.

[0062] 17 is a diagram showing an example of the relationship between the robot 200 equipped with the TOF camera 150 according to the first embodiment and the subject T, as viewed from above. As shown in Fig. 17, the robot 200 has the TOF camera 150, a power supply 162, and a central processing unit 203. The TOF camera 150 has a light emitting unit 153, a light receiving unit 154, and a lens 161.

[0063] A lens 161 is provided on the incident side of the light receiving section 154. The lens 161 guides the reflected laser light from the subject T to the light receiving section 154.

[0064] The transmitted laser light emitted from the light-emitting unit 153 scans the subject T. The reflected laser light reflected by the subject T passes through a lens 161 and is received by the light-receiving unit 154. The received reflected light is input to a signal processing unit (not shown) of the TOF camera 150 for each row. A power supply 162 is supplied to the light-emitting unit 153, the light-receiving unit 154, and the signal processing unit. The central processing unit 203 performs various controls, such as depth processing, of the robot 200, based on an image obtained based on a light-receiving signal of the reflected light output from the light-receiving unit 154.

[0065] 17 , the illumination spot (position of the light-emitting pixel) of the light-emitting unit 153 is normally at the same position as the position of the light-receiving pixel of the light-receiving unit 154. However, if the brightness of the reflected light from the subject T received by the light-receiving pixel of the light-receiving unit 154 is high, the light-emitting unit 153 changes the position of the illumination spot to the position of the light-receiving pixel. By performing such control, the distance measurement method of the first embodiment reduces the effect of strong reflected light on the distance measurement result.

[0066] 2.1.1.3. Configuration of Robot Mounted with TOF Camera 150 FIG. 18 is a diagram showing the configuration of robot 200 mounted with TOF camera 150 according to the first embodiment.

[0067] As shown in FIG. 18, the robot 200 includes a TOF camera 150 , a battery 201 , a wireless communication unit 202 , a central processing unit 203 , a memory unit 204 , and a motor drive unit 205 .

[0068] The TOF camera 150 outputs a captured image in which information from all pixels is combined. The battery 201 supplies power to the TOF camera 150, wireless communication unit 202, central processing unit 203, and motor drive unit 205.

[0069] The wireless communication unit 202 performs wireless communication with the outside of the robot 200. The central processing unit 203 performs processing such as recognizing the self-position of the robot 200 based on the captured image sent from the TOF camera 150.

[0070] The storage unit 204 is a storage device such as a hard disk drive (HDD) or a solid state drive (SSD), and stores programs and data for controlling the robot 200. The motor drive unit 205 controls the drive of motors provided in each part of the robot 200 based on control commands from the central processing unit 203.

[0071] 2.1.2. Operation FIG. 19 is a flowchart for explaining the operation of the TOF camera 150 according to the first embodiment.

[0072] The processor of the TOF camera 150 reads the brightness threshold Ith at the start of distance measurement (step S1). The brightness threshold Ith is an initial brightness threshold.

[0073] Next, the processor of the TOF camera 150 receives the intensity and time of the laser light emitted from the light-emitting unit 153 and the intensity and time of the received light signal received by the light-receiving unit 154, and generates and reads a brightness image based on the intensity and time of the received laser light and the intensity and time of the received light signal (step S2).

[0074] Next, the processor of the TOF camera 150 extracts the luminance I(x, y) of the pixel of interest (x, y) from the generated luminance image (step S3). The extraction of the luminance I(x, y) of the pixel of interest (x, y) in step S3 is performed for all pixels.

[0075] Next, the processor of the TOF camera 150 determines whether the luminance I(x, y) of the extracted pixel of interest (x, y) is smaller than a luminance threshold Ith (step S4).

[0076] In step S4, if the brightness I(x, y) of the extracted target pixel (x, y) is not less than the brightness threshold Ith (No in step S4), the irradiation spot designation unit 152 instructs the light-emitting unit 153 to shift the irradiation spot from the light-receiving pixel (step S5), and returns to the processing of step S2.

[0077] In step S4, if the luminance I(x, y) of the extracted pixel of interest (x, y) is smaller than the luminance threshold Ith (Yes in step S4), the processor of the TOF camera 150 performs normal distance measurement (step S6) and returns to the processing of step S2. In normal distance measurement, the irradiation spot is aligned with the position of the light-receiving pixel, and the laser light is scanned.

[0078] <2.2. Second Embodiment> Next, a distance measurement device that performs a distance measurement method according to a second embodiment of the present disclosure will be described. The distance measurement device according to the second embodiment can measure distance more accurately than the distance measurement device according to the first embodiment. <2.2.1. Configuration> <2.2.1.1. Functional Block Diagram of TOF Camera 350> FIG. 20 is a functional block diagram of a TOF camera 350 according to the second embodiment. As shown in FIG. 20 , the TOF camera 350 includes a TOF camera A and a TOF camera B. The TOF camera 350 according to the second embodiment includes two TOF cameras, A and B, in comparison with the TOF camera 150 according to the first embodiment. TOF camera A includes a light-emitting unit 353a and a light-receiving unit 354a. TOF camera B includes a light-emitting unit 353b and a light-receiving unit 354b.

[0079] The TOF camera 350 further includes a synchronization signal generating unit 351 , an irradiation angle specifying unit 352 , signal processing units 355 a and 355 b , and an image output unit 356 .

[0080] The synchronization signal generation unit 351 outputs a synchronization pulse signal indicating the timing of emitting laser light to the light emitters 353a and 353b. The synchronization signal generation unit 351 also outputs a synchronization pulse signal indicating the timing of receiving laser light to the light receivers 354a and 354b. The synchronization pulse signal may be a time stamp.

[0081] The irradiation angle instructing unit 352 outputs an irradiation instruction to the light-emitting unit 353 a to change the irradiation angle of the laser light. Specifically, when the luminance of the pixel of interest exceeds a threshold, the irradiation angle instructing unit 352 instructs the light-emitting unit 353 a and the light-emitting unit 353 b to switch the laser light emitted from the light-emitting unit 353 a to the laser light emitted from the light-emitting unit 353 b.

[0082] Furthermore, when the brightness of the pixel of interest exceeds a threshold value, the irradiation angle instruction unit 352 instructs the light-emitting units 353a and 353b to switch the laser light emitted from the light-emitting unit 353b to the laser light emitted from the light-emitting unit 353a.

[0083] Furthermore, the irradiation angle instruction section 352 instructs the light emitting sections 353a and 353b as to which pixels to emit light, and instructs the light receiving sections 354a and 354b as to which pixels to receive light.

[0084] The light-emitting units 353a and 353b irradiate the irradiation spot with laser light from the instructed light-emitting pixel based on an irradiation instruction to change the irradiation angle from the irradiation angle instructing unit 352. Furthermore, the light-emitting units 353a and 353b output the intensity and duration of the irradiated laser light to the signal processing unit 155.

[0085] Specifically, light-emitting unit 353a stops emitting laser light when it receives an instruction from irradiation angle instruction unit 352 to switch from laser light emitted from light-emitting unit 353a to laser light emitted from light-emitting unit 353b. Light-emitting unit 353b emits laser light based on the pulse signal input from synchronization signal generation unit 351 when it receives an instruction from irradiation angle instruction unit 352 to switch from laser light emitted from light-emitting unit 353a to laser light emitted from light-emitting unit 353b.

[0086] Light-emitting unit 353b stops emitting laser light when it receives an instruction from irradiation angle specifying unit 352 to switch from laser light emitted from light-emitting unit 353b to laser light emitted from light-emitting unit 353a. Light-emitting unit 353a emits laser light based on the pulse signal input from synchronization signal generating unit 351 when it receives an instruction from irradiation angle specifying unit 352 to switch from laser light emitted from light-emitting unit 353b to laser light emitted from light-emitting unit 353a.

[0087] The light receiving units 354a and 354b receive the light receiving signals of the instructed light receiving pixels based on the pulse signal input from the synchronization signal generation unit 351, in accordance with the irradiation instruction to change the irradiation angle from the irradiation angle instruction unit 352. The light receiving unit 354a outputs the intensity and time of the light receiving signal of the light receiving pixel that received light to the signal processing unit 355a. The light receiving unit 354b outputs the intensity and time of the light receiving signal of the light receiving pixel that received light to the signal processing unit 355b.

[0088] The signal processing unit 355a calculates and outputs the distance of a single pixel (x, y) based on the intensity and time of the received light signal output from the light receiving unit 354a and the intensity and time of the irradiated laser light output from the light emitting unit 353a.

[0089] The signal processing unit 355b calculates and outputs the distance of a single pixel (x, y) based on the intensity and time of the received light signal output from the light receiving unit 354b and the intensity and time of the irradiated laser light output from the light emitting unit 353b.

[0090] The image output unit 356 synthesizes the information of all pixels based on the distance of a single pixel (x, y) output from the signal processing unit 355a and the distance of a single pixel (x, y) output from the signal processing unit 355b, and outputs the synthesized information as a single image.

[0091] <2.2.1.1.2. Configuration of Robot 400 Mounted with TOF Camera 350> FIG. 21 is a diagram showing the configuration of a robot 400 mounted with a TOF camera 350 according to the second embodiment.

[0092] As shown in FIG. 21, the robot 400 includes a TOF camera A and a TOF camera B of the TOF camera 350, a battery 401, a wireless communication unit 402, a central processing unit 403, a memory unit 404, and a motor drive unit 405.

[0093] The TOF cameras A and B output captured images in which information from all pixels is combined. The battery 401 supplies power to the TOF cameras A and B, the wireless communication unit 402, the central processing unit 403, and the motor drive unit 405.

[0094] The wireless communication unit 402 performs wireless communication with the outside of the robot 400. The central processing unit 403 performs processing such as recognizing the self-position of the robot 400 based on the captured images sent from the TOF camera A and the TOF camera B.

[0095] The storage unit 404 is a storage device such as a hard disk drive (HDD) or a solid state drive (SSD), and stores programs and data for controlling the robot 400. The motor drive unit 405 controls the drive of motors provided in each part of the robot 400 based on control commands from the central processing unit 403.

[0096] <2.2.2. Operation> <2.2.2.1. Flowchart> Next, a description will be given of the operation of the TOF camera 350 according to the second embodiment. Fig. 22 is a flowchart for explaining the operation of the TOF camera 350 according to the second embodiment.

[0097] The processor of the TOF camera 350 reads the brightness threshold Ith at the start of distance measurement (step S11). The brightness threshold Ith is an initial brightness threshold.

[0098] Next, the processor of the TOF camera 350 receives the intensity and time of the laser light emitted from the light-emitting unit 353a and the intensity and time of the light-receiving signal received by the light-receiving unit 354a, and generates and reads a brightness image based on the intensity and time of the received laser light and the intensity and time of the light-receiving signal (step S12).

[0099] Next, the processor of the TOF camera 350 extracts the luminance I(x, y) of the pixel of interest (x, y) from the generated luminance image (step S13). The extraction of the luminance I(x, y) of the pixel of interest (x, y) in step S13 is performed for all pixels.

[0100] Next, the processor of the TOF camera 350 determines whether the luminance I(x, y) of the extracted pixel of interest (x, y) is smaller than a luminance threshold Ith (step S14).

[0101] In step S14, if the brightness I(x, y) of the extracted target pixel (x, y) is equal to or greater than the brightness threshold Ith (No in step S14), the irradiation angle instruction unit 352 outputs an irradiation instruction to change the irradiation angle of the laser light to the light emitters 353a and 353b (step S15), and the process returns to step S12.

[0102] In step S15, the irradiation angle instruction unit 352 outputs an irradiation instruction to change the irradiation angle of the laser light to the light-emitting units 353a and 353b, whereby the light-emitting unit 353a that emits laser light is switched to the light-emitting unit 353b, or the light-emitting unit 353b that emits laser light is switched to the light-emitting unit 353a.

[0103] In step S14, if the luminance I(x, y) of the extracted pixel of interest (x, y) is smaller than the luminance threshold Ith (Yes in step S14), the processor of the TOF camera 350 performs normal distance measurement (step S16) and returns to the processing of step S12. The normal distance measurement is performed in a state where the irradiation spot and the light-receiving pixel are aligned.

[0104] 2.2.2.2. Low Reflection Mode FIG. 23 is a diagram illustrating a case where cameras A and B mounted on a conventional vehicle C recognize a retroreflective material S. In FIG.

[0105] 23, camera A irradiates a transmitted laser beam Tx, indicated by a thick line, onto a retroreflective material S, and receives a reflected laser beam Rx, indicated by a thick line, that is reflected by the retroreflective material S. Camera A recognizes the distance to the retroreflective material S based on the transmission timing of the transmitted laser beam Tx and the reception timing of the reflected laser beam Rx.

[0106] Camera B irradiates the transmitted laser light Tx onto the retroreflective material S and receives the reflected laser light Rx reflected by the retroreflective material S. Camera B recognizes the distance to the retroreflective material S based on the transmission timing of the transmitted laser light Tx and the reception timing of the reflected laser light Rx.

[0107] Furthermore, vehicle C recognizes its own position based on the distance to the retroreflective material S, the recognized images of cameras A and B, etc. However, when retroreflective material S is used, the intensity of the reflected laser light Rx is so strong that an error occurs in measuring the distance to the retroreflective material S.

[0108] The device of the present disclosure is provided with cameras A and B, where camera A emits transmitted laser light Tx and camera B receives reflected laser light Rx. Also, camera B emits transmitted laser light Tx and camera A receives reflected laser light Rx. This mode is called a "low reflection mode."

[0109] 24 and 25 are diagrams for explaining the low-reflection mode according to the first embodiment. Fig. 24 shows a case where camera A irradiates a retroreflective material S with transmitted laser light Tx, and camera B receives reflected laser light Rx from the retroreflective material S. Fig. 25 shows a case where camera B irradiates a retroreflective material S with transmitted laser light Tx, and camera A receives reflected laser light Rx from the retroreflective material S.

[0110] Camera A and camera B are positioned at a distance from each other. Therefore, the reflection angle between the transmitted laser light Tx from camera A and the reflected laser light Rx from camera B is wider than when there is only one camera. Therefore, the distance measurement device of the present disclosure is not affected by strong reflected light from the retroreflective material S (lens ghost), and can reduce errors in the measured distance.

[0111] <2.2.2.3. Timing of Light Emission and Light Reception> Next, a description will be given of the timing of light emission and light reception by camera A and camera B. Fig. 26 is a timing chart for explaining synchronization signals for light emission and light reception by camera A and camera B.

[0112] As shown in FIG. 26, the transmission timing of the transmission laser light Tx_1 from the camera A and the transmission timing of the transmission laser light Tx_2 from the camera B alternate.

[0113] The timing of reception of the reflected laser light Rx_1 by the camera A and the timing of reception of the reflected laser light Rx_2 by the camera B operate in a complementary manner.

[0114] That is, while camera A is transmitting the transmitted laser light Tx_1, camera B is receiving the reflected laser light Rx_2, and while camera B is transmitting the transmitted laser light Tx_2, camera A is receiving the reflected laser light Rx_1.

[0115] 2.3. Third embodiment Fig. 27 is a diagram illustrating a case where cameras A and B mounted on a vehicle C according to a third embodiment recognize a retroreflective material S. Fig. 27 is a diagram of the vehicle C as seen from above.

[0116] 27, cameras A and B are positioned facing the inside of vehicle C. More specifically, the angle formed by a first imaginary line connecting the light-emitting part of camera A and the retroreflective material S and a second imaginary line connecting the light-receiving part of camera B and the retroreflective material S is smaller than 90 degrees.

[0117] By arranging cameras A and B in this way, the distance measurement device of the present disclosure can reduce blind spots at close range, thereby improving the stopping position accuracy when, for example, vehicle C is docked at an automatic charger that has retroreflective material attached as a landmark.

[0118] 2.4. Fourth Embodiment FIG. 28 is a diagram illustrating a case where a retroreflective material S is recognized using a light source o and a camera Ca mounted on a vehicle C according to a fourth embodiment.

[0119] The distance measurement device according to the fourth embodiment includes a light source o and one camera Ca. As shown in Fig. 28, a transmitted laser beam Tx emitted from the light source o is irradiated onto a retroreflective material S. A reflected laser beam Rx reflected by the retroreflective material S is received by a light receiving unit of the camera Ca.

[0120] The signal processing unit of the camera Ca calculates and outputs the distance of a single pixel (X, Y) based on the intensity and time of the received light signal output from the light receiving unit of the camera Ca and the intensity and time of the laser light output from the light source o.

[0121] Therefore, the distance measurement device according to the fourth embodiment can be configured with only one camera and light source o, and can take a wide angle between the irradiation of the laser light and the reflected light, thereby preventing errors in distance measurement caused by excessively strong reflected light from the retroreflective material S. Furthermore, because the distance measurement device according to the fourth embodiment requires only one camera Ca, costs can be reduced.

[0122] 2.5. Fifth Embodiment FIG. 29 is a diagram showing how cameras A and B mounted on a car C according to a fifth embodiment are switched between the normal mode and the low-reflection mode.

[0123] As shown in Fig. 29, the distance measurement device may automatically switch between the normal mode and the low-reflection mode. As described in step S14 of the second embodiment, the switching may be performed by determining whether the luminance I(x, y) of the pixel of interest (x, y) is smaller than the luminance threshold value Ith, or may be performed based on a switching instruction from the user.

[0124] The width of the blind spot is low reflection mode > short-distance low reflection mode > normal mode. Therefore, the distance measurement device according to the fifth embodiment can reduce the blind spot at short distances, which is a drawback of the low reflection mode, by switching to the normal mode.

[0125] <2.6. Sixth embodiment> A distance measurement device according to the sixth embodiment is a device that can change the irradiation spot described in the first embodiment, change the irradiation angle described in the second embodiment, and perform normal distance measurement.

[0126] <2.6.1. Functional Block Diagram of TOF Camera 650> Fig. 30 is a functional block diagram of the TOF camera 650 according to the sixth embodiment. As shown in Fig. 30, the TOF camera 650 has a TOF camera A and a TOF camera B. TOF camera A has a light-emitting unit 654a and a light-receiving unit 655a. TOF camera B has a light-emitting unit 654b and a light-receiving unit 655b.

[0127] The TOF camera 650 further includes a synchronization signal generation unit 651 , an irradiation angle instruction unit 652 , an irradiation spot instruction unit 653 , signal processing units 656 a and 656 b , and an image output unit 657 .

[0128] The synchronization signal generating unit 651 outputs a synchronization pulse signal indicating the timing of emitting laser light to the light emitting units 654a and 654b. The synchronization signal generating unit 651 also outputs a synchronization pulse signal indicating the timing of receiving laser light to the light receiving units 655a and 655b. The synchronization pulse signal may be a time stamp.

[0129] The irradiation angle instruction unit 652 outputs an irradiation instruction to the light-emitting unit 654 a to change the irradiation angle of the laser light. Specifically, when the luminance of the pixel of interest exceeds a threshold, the irradiation angle instruction unit 652 instructs the light-emitting unit 654 a and the light-emitting unit 654 b to switch the laser light emitted from the light-emitting unit 654 a to the laser light emitted from the light-emitting unit 654 b.

[0130] Furthermore, when the brightness of the pixel of interest exceeds a threshold value, the irradiation angle instruction unit 652 instructs the light-emitting units 654a and 654b to switch the laser light emitted from the light-emitting unit 654b to the laser light emitted from the light-emitting unit 654a.

[0131] Furthermore, the irradiation angle instruction section 652 instructs the light emitting sections 654a and 654b as to which pixels to emit light, and instructs the light receiving sections 655a and 655b as to which pixels to receive light.

[0132] The irradiation spot designation unit 653 designates the irradiation spot of the laser light to be emitted by the light-emitting units 654 a and 654 b. When the brightness of the light-receiving pixel of the light-receiving units 655 a and 655 b corresponding to the irradiation spot exceeds a threshold, the irradiation spot designation unit 653 designates the irradiation spot of the emitted laser light so as to be shifted from the position of the light-receiving pixel corresponding to the irradiation spot.

[0133] Typically, the positions of the light-emitting pixels of the light-emitting units 654a and 654b of the illumination spot are the same as the positions of the light-receiving pixels of the light-receiving units 655a and 655b (illumination spot = light-emitting pixel (X, Y) = light-receiving pixel (X, Y)). Even if a retroreflective material is used on the subject and the reflected light received by the light-receiving pixels is strong, the technology disclosed herein makes the positions of the illumination spot and the light-receiving pixels different, preventing strong reflected light and measuring the accurate distance to the retroreflective material.

[0134] In the sixth embodiment, when the brightness of the light-receiving pixel of the light-receiving units 655a, 655b corresponding to the irradiation spot exceeds a threshold, the irradiation spot designation unit 653 designates the irradiation spot of the emitted laser light to be shifted from the position of the light-receiving pixel corresponding to the irradiation spot (irradiation spot ≠ light-receiving pixel (X, Y)). In other words, when the brightness of the light-receiving pixel of the light-receiving units 655a, 655b corresponding to the irradiation spot exceeds a threshold, the irradiation spot designation unit 653 instructs the light-emitting units 654a, 654b to emit light to a light-emitting pixel at a position different from the light-receiving pixel.

[0135] The method of shifting the irradiation spot (light-emitting pixel) relative to the light-receiving pixel is not particularly limited. For example, the irradiation spot and the light-receiving pixel may be shifted in a point-symmetric manner. When shifting in a point-symmetric manner, for example, the irradiation spot designation unit 653 may instruct the light-receiving units 655 a and 655 b to irradiate the irradiation spot in the upper left of the screen with laser light and to receive the reflected light at the light-receiving pixel in the lower right of the screen.

[0136] If the luminance of the reflected light received by the pixel of interest (light-receiving pixel) does not exceed a threshold value, the illumination spot instruction unit 653 instructs the light-emitting units 654a and 654b to illuminate the illumination spot of the light-emitting pixel at the same position as the light-receiving pixel.

[0137] When the brightness of the pixel of interest (the light-receiving pixel corresponding to the irradiation spot) does not exceed the threshold, the irradiation spot designation unit 653 designates the position of the light-receiving pixel corresponding to the irradiation spot to the light-receiving units 655 a, 655 b. Similarly, the irradiation spot designation unit 653 designates the position of the light-receiving pixel corresponding to the irradiation spot that receives reflected light of the laser light emitted from the retroreflective material at a position shifted from the irradiation spot to the light-receiving units 655 a, 655 b.

[0138] Furthermore, the irradiation spot designation unit 653 may designate light-emitting pixels to the light-emitting units 654a and 654b, and designate light-receiving pixels to the light-receiving units 655a and 655b.

[0139] For example, in the case of VGA (Video Graphics Array) resolution, the irradiation spot designation unit 653 designates an irradiation spot with an X coordinate of 0 to 640 and a Y coordinate of 0 to 480. In this case, scanning by the light-emitting units 654a, 654b and the light-receiving units 655a, 655b is performed in order from the top left to the bottom right of the screen.

[0140] In the sixth embodiment, when the brightness of the pixel of interest exceeds a threshold value, the illumination spot designation unit 653 shifts the light-emitting pixels of the illumination spot from the light-receiving pixels to emit light. When the brightness of the pixel of interest exceeds a threshold value, instead of the light-emitting units 654a and 654b shifting the positions of the light-emitting pixels of the illumination spot from the positions of the light-receiving pixels, the light-receiving units 655a and 655b may shift the positions of the light-receiving pixels from the position of the illumination spot.

[0141] Furthermore, when the luminance of the pixel of interest exceeds a threshold, the irradiation spot designation unit 653 selects a pixel whose luminance value is lower than the threshold, and may designate the position of the selected light-receiving pixel with the lower luminance value as the irradiation spot.

[0142] The light emitters 654 a and 654 b emit laser light to the retroreflective material to be measured at the irradiation spot of the laser light specified by the irradiation spot specifying unit 653 at the emission timing of the synchronization pulse signal from the synchronization signal generating unit 151 .

[0143] The light emitting units 654a and 654b output the intensity and duration of the emitted laser light to the signal processing units 656a and 656b. The light emitting units 654a and 654b are, for example, VCSELs (Vertical Cavity Surface Emitting Lasers).

[0144] The light emitters 654a and 654b irradiate the irradiation spot with laser light based on an irradiation instruction to change the irradiation angle from the irradiation angle instruction unit 652. Furthermore, the light emitters 654a and 654b output the intensity and duration of the irradiated laser light to the signal processing units 656a and 656b.

[0145] Specifically, light-emitting unit 654a stops emitting laser light when it receives an instruction from irradiation angle instruction unit 652 to switch from laser light emitted from light-emitting unit 654a to laser light emitted from light-emitting unit 654b. Light-emitting unit 654b emits laser light when it receives an instruction from irradiation angle instruction unit 652 to switch from laser light emitted from light-emitting unit 654a to laser light emitted from light-emitting unit 654b.

[0146] Light-emitting unit 654b stops emitting laser light when it receives an instruction from irradiation angle instruction unit 652 to switch from laser light emitted from light-emitting unit 654b to laser light emitted from light-emitting unit 654a. Light-emitting unit 654a emits laser light when it receives an instruction from irradiation angle instruction unit 652 to switch from laser light emitted from light-emitting unit 654b to laser light emitted from light-emitting unit 654a.

[0147] The light receiving units 655a and 655b receive light receiving signals from the specified light receiving pixels based on instructions from the irradiation spot designation unit 653. Furthermore, the light receiving units 655a and 655b output the intensity and time of the light receiving signals from the light receiving pixels that received light to the signal processing units 656a and 656b.

[0148] The light receiving units 655a and 655b may receive light at least by an IR (infrared) method, for example. For example, the light receiving unit 120 may be an RGB sensor including an infrared sensor. The light receiving units 655a and 655b may also be a stacked dToF distance measurement sensor (2D-LiDAR, 3D-LiDAR) for in-vehicle LiDAR using PAD pixels, or a CMOS (Complementary Metal-Oxide-Semiconductor).

[0149] The light receiving units 655a and 655b receive light receiving signals from the instructed light receiving pixels based on irradiation instructions to change the irradiation angle from the irradiation angle instruction unit 652. The light receiving unit 655a outputs the intensity and time of the light receiving signal from the light receiving pixel that received light to the signal processing unit 656a. The light receiving unit 655b outputs the intensity and time of the light receiving signal from the light receiving pixel that received light to the signal processing unit 656b.

[0150] The signal processing unit 656 includes a signal processing unit 656 a and a signal processing unit 656 b. The signal processing unit 656 a determines and outputs the distance of a single pixel (x, y) based on the intensity and time of the received light signal output from the light receiving unit 655 a and the intensity and time of the irradiated laser light output from the light emitting unit 654 a.

[0151] The signal processing unit 656b calculates and outputs the distance of a single pixel (x, y) based on the intensity and time of the received light signal output from the light receiving unit 655b and the intensity and time of the irradiated laser light output from the light emitting unit 654b.

[0152] The image output unit 657 synthesizes the information of all pixels based on the distance of a single pixel (x, y) output from the signal processing unit 656a and the distance of a single pixel (x, y) output from the signal processing unit 656b, and outputs the synthesized information as a single image.

[0153] <2.6.2. Flowchart> FIG. 31 is a flowchart for explaining the operation of the TOF camera 650 according to the sixth embodiment.

[0154] The processor of the TOF camera 650 reads the brightness threshold Ith at the start of distance measurement (step S21). The brightness threshold Ith is an initial brightness threshold. The signal processing unit 155 also reads the irradiation spot change flag (LD_f=0) (step S22). The value of the irradiation spot change flag LD_f may be changed based on, for example, an instruction from the user. The order of reading the brightness threshold Ith in step S21 and reading the irradiation spot change flag (LD_f=0) in step S22 may be reversed.

[0155] Next, the TOF camera 650 processor receives the intensity and time of the laser light emitted from the light-emitting unit 654a and the intensity and time of the received light signal received by the light-receiving unit 655b, and generates and reads a brightness image based on the intensity and time of the received laser light and the intensity and time of the received light signal (step S23).

[0156] Next, the TOF camera 650 processor extracts the intensity I(x, y) of the pixel of interest (x, y) from the generated intensity image (step S24). The extraction of the intensity I(x, y) of the pixel of interest (x, y) in step S24 is performed for all pixels.

[0157] Next, the TOF camera 650 processor determines whether the brightness I(x, y) of the extracted pixel of interest (x, y) is smaller than a brightness threshold Ith (step S25).

[0158] In step S25, if the brightness I(x, y) of the extracted pixel of interest (x, y) is not less than the brightness threshold Ith (No in step S25), the TOF camera 650 processor determines whether the illumination spot change flag LD_f = 0 (step S27).

[0159] If the irradiation spot instruction unit 653 determines in step S27 that the irradiation spot change flag LD_f=0, it instructs the light emitter 654a to shift the irradiation spot from the light-receiving pixel (step S28). Next, the processing of the TOF camera 650 processor sets the irradiation spot change flag LD_f to LD_f=1 (step S29), and returns to the processing of step S23.

[0160] If the TOF camera 650 processor determines in step S27 that the irradiation spot change flag LD_f is not 0 (No in step S27), the irradiation angle instruction unit 652 outputs an irradiation instruction to change the irradiation angle of the laser light to the light emitters 654a and 654b (step S30), and the processing of the TOF camera 650 processor returns to the processing of step S23.

[0161] In step S25, if the luminance I(x, y) of the extracted pixel of interest (x, y) is smaller than the luminance threshold Ith (Yes in step S25), the TOF camera 650 processor performs normal distance measurement (step S26) and returns to the processing of step S12. The normal distance measurement is performed in a state where the illumination spot and the light-receiving pixel are aligned.

[0162] 2.7. Effects As described above, the distance measurement method according to the present disclosure includes: a computer shifting an irradiation spot of laser light from the position of a light-receiving pixel corresponding to the irradiation spot, emitting laser light to the shifted irradiation spot (in the embodiment, the synchronization signal generation unit 151, the irradiation spot designation unit 152, and the light-emitting unit 153); receiving reflected light of the emitted laser light from the measurement target at the light-receiving pixel corresponding to the irradiation spot (in the embodiment, the synchronization signal generation unit 151 and the light-receiving unit 154); and measuring the distance to the measurement target based on the timing of emitting the laser light and the timing of receiving the reflected light (in the embodiment, the signal processing unit 155).

[0163] In the distance measurement method according to the present disclosure, the irradiation spot of the laser light emitted from the light-emitting unit is shifted from the position of the light-receiving pixel. Therefore, the distance measurement method according to the present disclosure can prevent the influence of strong reflected light from the retroreflective material even when the retroreflective material is used as a landmark. Therefore, the distance measurement method according to the present disclosure can accurately measure the distance to the retroreflective material. Furthermore, the distance measurement method according to the present disclosure can accurately measure the distance even when a single imaging device such as a camera uses the retroreflective material as a landmark, thereby reducing the cost of the distance measurement device.

[0164] Furthermore, the distance measurement method according to the present disclosure includes, before emitting light, determining whether the luminance intensity of reflected light received by a light-receiving pixel corresponding to an arbitrary irradiation spot exceeds a threshold, and emitting light shifts the irradiation spot corresponding to the light-receiving pixel whose luminance intensity is determined to exceed the threshold. Such a distance measurement method according to the present disclosure can select a distance measurement method by setting a threshold. Furthermore, the distance measurement method according to the present disclosure can accurately measure an area where the high luminance of reflected light from the measurement object affects the distance measurement.

[0165] In the distance measurement method according to the present disclosure, the emitting of laser light is performed by emitting laser light to a shifted illumination spot that is a point target position on the screen relative to the light-receiving pixels. In this distance measurement method according to the present disclosure, the illumination spot is irradiated onto the point target position on the screen relative to the light-receiving pixels. Therefore, accurate distance measurement is possible even when a retroreflective material is used as a landmark.

[0166] The emitting of light includes aligning the illumination spot with the position of the light-receiving pixel when the luminance of the reflected light received by the light-receiving pixel does not exceed a threshold. In the distance measurement method according to the present disclosure, when the luminance of the reflected light received by the light-receiving pixel does not exceed a threshold, a conventional distance measurement method can be used in combination with the distance measurement method according to the present disclosure.

[0167] A distance measurement method according to the present disclosure includes, when the luminance of reflected light received by a light-receiving pixel exceeds a threshold, selecting a light-receiving pixel whose luminance of the reflected light is lower than the threshold, and designating the position of the selected light-receiving pixel as an illumination spot. When the luminance of reflected light received by a light-receiving pixel exceeds the threshold, the distance measurement method according to the present disclosure selects a light-receiving pixel whose luminance of the reflected light is lower than the threshold. The distance measurement method according to the present disclosure then designates the position of the selected light-receiving pixel as an illumination spot. Therefore, even when a retroreflective material is used as a landmark, the distance measurement method according to the present disclosure can prevent the influence of strong reflected light from the retroreflective material, enabling accurate distance measurement.

[0168] Furthermore, the light receiving unit having a plurality of light receiving pixels is a 3D-LiDAR using PAD pixels. By using 3D-LiDAR using PAD pixels, the distance measurement method according to the present disclosure can acquire three-dimensional geometric characteristics of the measurement object to which the retroreflective material is attached in addition to the intensity of the reflected light from the retroreflective material, which is advantageous for extracting characteristics of the measurement object and can more appropriately measure the distance accurately even if the reflected light from the measurement object is weak.

[0169] In addition, the distance measurement method disclosed herein is a distance measurement method in a distance measurement device having a first device having a first light-emitting unit (light-emitting unit 353a in the embodiment) that emits laser light to an irradiation spot, a second device having a second light-emitting unit (light-emitting unit 353b in the embodiment) that emits laser light to the irradiation spot, and a second light-receiving unit (light-receiving unit 354b in the embodiment) that receives reflected light from the object to be measured, the method including a computer emitting laser light from the first light-emitting unit to the irradiation spot, receiving reflected light from the object to be measured of the emitted laser light at a light-receiving pixel corresponding to the irradiation spot of the second light-receiving unit, and measuring the distance to the object to be measured based on the timing of emission of the laser light from the first light-emitting unit and the timing of reception of the reflected light by the second light-receiving unit.

[0170] In the distance measurement method according to the present disclosure, even when a retroreflective material is used as a landmark, the first of the two imaging devices emits laser light and the second device receives the reflected light. This allows for a wide reflection angle between the laser light and the reflected light, preventing the influence of strong reflected light from the retroreflective material. Therefore, the distance measurement method according to the present disclosure can accurately measure the distance to the retroreflective material.

[0171] In addition, the distance measurement method according to the present disclosure includes a first device having a first light receiving unit (light receiving unit 354a in the embodiment) that receives reflected light of laser light from an object to be measured, and when the brightness intensity of the reflected light received by a light receiving pixel corresponding to the irradiation spot exceeds a threshold, emitting laser light from a second light emitting unit to the irradiation spot, receiving reflected light of the laser light emitted from the second light emitting unit from the object to be measured at a light receiving pixel corresponding to the irradiation spot of the first light receiving unit, and measuring the distance to the object to be measured based on the timing of emitting the laser light from the second light emitting unit and the timing of receiving the reflected light by the first light receiving unit.

[0172] In the distance measurement method according to the present disclosure, when the luminance of the reflected light exceeds a threshold, the illumination angle is changed and the distance to the measurement object is measured, thereby enabling the distance measurement method according to the present disclosure to measure the distance to the measurement object more accurately than before the illumination angle was changed.

[0173] The distance measurement method according to the present disclosure also includes aligning the positions of the irradiation spot and the light receiving pixel when the luminance intensity of the reflected light received by the light receiving pixel corresponding to the irradiation spot does not exceed a threshold value.

[0174] The distance measurement method according to the present disclosure can be used in conjunction with conventional scanning by aligning the illumination spot with the light-receiving pixel. Therefore, the distance measurement method according to the present disclosure can be used in a wide range of applications even when the luminance of the reflected light received by the light-receiving pixel does not exceed a threshold. Furthermore, by having two measurement methods, the distance measurement method according to the present disclosure can be used even if one of the devices breaks down.

[0175] The distance measurement method according to the present disclosure also includes alternately controlling the timing of emission of laser light from the first light-emitting unit and the timing of emission of laser light from the second light-emitting unit.

[0176] The distance measurement method according to the present disclosure alternately controls the timing of light emission of the first light-emitting unit and the timing of light emission of the second light-emitting unit, thereby enabling effective use of both the first imaging device and the second imaging device.

[0177] The distance measurement method according to the present disclosure also includes complementarily controlling the timing of reception of reflected light by the first light receiving unit and the timing of emission of laser light by the second light receiving unit.

[0178] The distance measurement method according to the present disclosure complementarily controls the timing of receiving reflected light from the first light receiving unit and the timing of emitting laser light from the second light receiving unit, thereby enabling effective use of both the first imaging device and the second imaging device.

[0179] In addition, the distance measurement method according to the present disclosure includes controlling the timing of emitting laser light from the first light-emitting unit to coincide with the timing of receiving reflected light from the second light-receiving unit, and controlling the timing of receiving reflected light from the first light-receiving unit to coincide with the timing of emitting laser light from the second light-emitting unit.

[0180] The distance measurement method according to the present disclosure controls the light emission timing of the first light-emitting element to coincide with the light reception timing of the second light-receiving element, and the light reception timing of the first light-receiving element to coincide with the light emission timing of the second light-emitting element, thereby enabling effective use of both the first imaging device and the second imaging device.

[0181] Furthermore, the angle formed by the first virtual line connecting the first light-emitting unit of the first device and the object to be measured and the second virtual line connecting the second light-receiving unit of the second device and the object to be measured is smaller than 90 degrees.

[0182] The distance measurement method according to the present disclosure can reduce the blind spots of the first and second devices even when the distance to the measurement target is short. Therefore, the distance measurement method according to the present disclosure improves the stopping position accuracy, for example, when a vehicle docks at an automatic charger to which a robot has attached retroreflective material as a landmark.

[0183] The first device is a light source, and the second device is an imaging device. The distance measurement method according to the present disclosure uses a distance measurement device consisting of only one imaging device and a light source, and the distance measurement device used in the distance measurement method according to the present disclosure can prevent errors in distance measurement caused by excessively strong reflected light from the measurement target. Furthermore, because the distance measurement device according to the present disclosure requires only one imaging device, costs can be reduced.

[0184] The distance measurement method according to the present disclosure also includes switching to a normal mode in which the positions of the irradiation spots and the light-receiving pixels are aligned.

[0185] The distance measurement method according to the present disclosure can reduce the blind spot at close range, which is a drawback of the low reflectivity mode, by switching to the normal mode.

[0186] In addition, the distance measurement method according to the present disclosure includes, when the brightness intensity of the reflected light received by the light-receiving pixel corresponding to the irradiation spot exceeds a threshold value, shifting the laser light from the position of the light-receiving pixel corresponding to the irradiation spot and emitting it onto the object to be measured, receiving the reflected light from the object to be measured in response to the emitted laser light at the light-receiving pixel corresponding to the irradiation spot, and measuring the distance to the object to be measured based on the timing of emitting the laser light and the timing of receiving the reflected light.

[0187] The distance measurement method according to the present disclosure can select a change in the illumination angle and the illumination spot when the brightness of the reflected light received by the light-receiving pixel corresponding to the illumination spot exceeds a threshold, thereby selecting the optimal distance measurement method.

[0188] 2.8. Other Embodiments The processing according to the above-described embodiments may be implemented in various different forms other than the above-described embodiments.

[0189] Furthermore, among the processes described in the above embodiments, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically using known methods. Furthermore, the information, including the processing procedures, specific names, various data, and parameters shown in the above documents and drawings, can be changed as desired unless otherwise specified. For example, the various information shown in each drawing is not limited to the information shown in the drawings.

[0190] Furthermore, the components of each device shown in the figure are conceptual functional components and do not necessarily have to be physically configured as shown in the figure. In other words, the specific form of distribution and integration of each device is not limited to that shown in the figure, and all or part of them can be functionally or physically distributed and integrated in any unit depending on various loads, usage conditions, etc.

[0191] Furthermore, the above-described embodiments and modifications can be combined as appropriate within the scope of not causing any contradiction in the processing content.

[0192] Furthermore, the effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0193] 2.9. Hardware Configuration FIG. 32 is a hardware configuration diagram showing an example of a computer 1000 that realizes the arithmetic units of the TOF cameras 150, 350, and 650 and the robots 200 and 400, which are information processing devices according to the first to sixth embodiments.

[0194] The computer 1000 includes a CPU 1100, a RAM 1200, a ROM (Read Only Memory) 1300, a HDD (Hard Disk Drive) 1400, a communication interface 1500, and an input / output interface 1600. The components of the computer 1000 are connected by a bus 1050.

[0195] The CPU 1100 operates and controls each component based on programs stored in the ROM 1300 or the HDD 1400. For example, the CPU 1100 loads the programs stored in the ROM 1300 or the HDD 1400 into the RAM 1200 and executes processing corresponding to the various programs.

[0196] The ROM 1300 stores boot programs such as a Basic Input Output System (BIOS) that is executed by the CPU 1100 when the computer 1000 is started, as well as programs that depend on the hardware of the computer 1000 .

[0197] HDD 1400 is a computer-readable recording medium that non-temporarily records programs executed by CPU 1100 and data used by such programs. Specifically, HDD 1400 is a recording medium that records an application program according to the present disclosure, which is an example of program data 1450.

[0198] The communication interface 1500 is an interface for connecting the computer 1000 to an external network 1550 (e.g., the Internet). For example, the CPU 1100 receives data from other devices and transmits data generated by the CPU 1100 to other devices via the communication interface 1500.

[0199] The input / output interface 1600 is an interface for connecting the input / output device 1650 and the computer 1000. For example, the CPU 1100 receives data from an input device such as a keyboard or a mouse via the input / output interface 1600. The CPU 1100 also transmits data to an output device such as a display, a speaker, or a printer via the input / output interface 1600. The input / output interface 1600 may also function as a media interface for reading programs and the like recorded on a predetermined recording medium. Examples of media include optical recording media such as DVDs (Digital Versatile Discs) and PDs (Phase Change Rewritable Discs), magneto-optical recording media such as MOs (Magneto-Optical Discs), tape media, magnetic recording media, and semiconductor memories.

[0200] Although the CPU 1100 reads and executes the program data 1450 from the HDD 1400, as another example, the CPU 1100 may obtain these programs from other devices via an external network 1550.

[0201] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the technical scope of the present disclosure is not limited to these examples. It is clear that a person skilled in the art of the present disclosure can conceive of various modified or altered examples within the scope of the technical idea described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0202] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that will be apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0203] Note that the present technology can also be configured as follows. (1) A distance measurement method including: a computer shifting an irradiation spot of laser light from the position of a light-receiving pixel corresponding to the irradiation spot, emitting the laser light to the shifted irradiation spot; receiving reflected light of the emitted laser light from an object to be measured at the light-receiving pixel corresponding to the irradiation spot; and measuring a distance to the object to be measured based on the timing of emitting the laser light and the timing of receiving the reflected light. (2) The distance measurement method according to (1), including, before the emission of the laser light, determining whether the luminance intensity of the reflected light received by the light-receiving pixel corresponding to an arbitrary irradiation spot exceeds a threshold, wherein shifting the irradiation spot includes shifting the irradiation spot corresponding to the light-receiving pixel determined to have the luminance intensity exceed the threshold. (3) The distance measurement method according to (1) or (2), wherein shifting the irradiation spot includes shifting the irradiation spot of the laser light to a position on a screen that is point-symmetrical with respect to the light-receiving pixel of the laser light. (4) The distance measurement method according to (2), wherein the shifting of the illumination spot includes: matching the position of the illumination spot with the position of the light receiving pixel when the luminance intensity of the reflected light received by the light receiving pixel does not exceed the threshold. (5) The distance measurement method according to (2) or (4), wherein the shifting of the illumination spot includes: selecting the light receiving pixel whose luminance intensity of the reflected light is lower than the threshold when the luminance intensity of the reflected light received by the light receiving pixel exceeds the threshold, and shifting the illumination spot to the position of the selected light receiving pixel. (6) The distance measurement method according to any one of (1) to (5), wherein the light receiving unit having a plurality of light receiving pixels is a 3D-LiDAR using PAD pixels.(7) A distance measurement method for a distance measurement device including a first device having a first light-emitting unit that emits laser light to an irradiation spot, and a second device having a second light-emitting unit that emits laser light to the irradiation spot and a second light-receiving unit that receives reflected light from an object to be measured, the distance measurement method including: a computer causing the first light-emitting unit to emit the laser light to the irradiation spot; causing the second light-receiving unit to receive reflected light of the emitted laser light from the object to be measured at a light-receiving pixel corresponding to the irradiation spot; and measuring the distance to the object to be measured based on the timing of emitting the laser light from the first light-emitting unit and the timing of receiving the reflected light by the second light-receiving unit. (8) The distance measurement method according to (7), wherein the first device has a first light-receiving unit that receives reflected light of the laser light from the measurement object, and includes: emitting the laser light from the second light-emitting unit to the irradiation spot when a luminance intensity of the reflected light received by the light-receiving pixel corresponding to the irradiation spot exceeds a threshold; receiving the reflected light of the laser light emitted from the second light-emitting unit from the measurement object at the light-receiving pixel corresponding to the irradiation spot of the first light-receiving unit; and measuring the distance to the measurement object based on the emission timing of the laser light from the second light-emitting unit and the reception timing of the reflected light by the first light-receiving unit. (9) The distance measurement method according to (8), wherein the first device has a first light-receiving unit that receives reflected light of the laser light from the measurement object when a luminance intensity of the reflected light received by the light-receiving pixel corresponding to the irradiation spot does not exceed a threshold. (10) The distance measuring method according to (7) or (8), including alternately controlling the timing of emitting the laser light from the first light emitting unit and the timing of emitting the laser light from the second light emitting unit. (11) The distance measuring method according to any one of (8) to (10), including complementarily controlling the timing of receiving the reflected light from the first light receiving unit and the timing of emitting the laser light from the second light receiving unit.(12) The distance measurement method according to any one of (8) to (11), comprising controlling the emission timing of the laser light from the first light-emitting unit to coincide with the reception timing of the reflected light from the second light-receiving unit, and the reception timing of the reflected light from the first light-receiving unit to coincide with the emission timing of the laser light from the second light-emitting unit. (13) The distance measurement method according to (8), wherein an angle formed by a first virtual line connecting the first light-emitting unit of the first device and the object to be measured and a second virtual line connecting the second light-receiving unit of the second device and the object to be measured is smaller than 90 degrees. (14) The distance measurement method according to (7), wherein the first device is a light source, and the second device is an imaging device. (15) The distance measurement method according to (7), comprising switching to a normal mode in which the irradiation spot and the position of the light-receiving pixel are aligned. (16) The distance measuring method according to (8), comprising: when the luminance intensity of the reflected light received by the light-receiving pixel corresponding to the irradiation spot exceeds a threshold, shifting a laser beam from the position of the light-receiving pixel corresponding to the irradiation spot to emit it toward the measurement object, causing the light-receiving pixel corresponding to the irradiation spot to receive the light reflected from the measurement object of the emitted laser beam, and measuring the distance to the measurement object based on the emission timing of the laser beam and the reception timing of the reflected light. (17) A distance measuring device comprising: an emission control unit that shifts the irradiation spot of laser beam from the position of the light-receiving pixel corresponding to the irradiation spot and emits the laser beam toward the shifted irradiation spot, a light-receiving control unit that receives the light reflected from the measurement object of the emitted laser beam at the light-receiving pixel corresponding to the irradiation spot, and a measurement unit that measures the distance to the measurement object based on the emission timing of the laser beam and the reception timing of the reflected light.(18) A distance measuring device having a first device having a first light-emitting unit that emits laser light to an irradiation spot, and a second device having a second light-emitting unit that emits laser light to the irradiation spot and a second light-receiving unit that receives reflected light from a measurement object, the distance measuring device including: an emission control unit that causes the first light-emitting unit to emit the laser light to the irradiation spot; a light-receiving control unit that causes the second light-receiving unit to receive reflected light of the emitted laser light from the measurement object at a light-receiving pixel corresponding to the irradiation spot; and a measurement unit that measures the distance to the measurement object based on the emission timing of the laser light from the first light-emitting unit and the reception timing of the reflected light by the second light-receiving unit. (19) A program for causing a computer to function as: an emission control unit that shifts an irradiation spot of laser light from the position of a light-receiving pixel corresponding to the irradiation spot and emits the laser light to the shifted irradiation spot; a light-receiving control unit that receives reflected light from a measurement object in response to the emitted laser light at the light-receiving pixel corresponding to the irradiation spot; and a measurement unit that measures the distance to the measurement object based on the timing of emitting the laser light and the timing of receiving the reflected light. (20) A program for a distance measuring device including a first device having a first light-emitting unit that emits laser light to an irradiation spot, and a second device having a second light-emitting unit that emits laser light to the irradiation spot and a second light-receiving unit that receives reflected light from a measurement object, the program causing a computer to function as: an emission control unit that causes the first light-emitting unit to emit the laser light to the irradiation spot; a light-receiving control unit that causes the second light-receiving unit to receive reflected light of the emitted laser light from the measurement object at a light-receiving pixel corresponding to the irradiation spot; and a measurement unit that measures the distance to the measurement object based on the emission timing of the laser light from the first light-emitting unit and the reception timing of the reflected light by the second light-receiving unit.

[0204] 153, 353a, 353b, 654a, 654b Light emitting unit 154, 354a, 354b, 655a, 655b Light receiving unit 150, 350, 650 TOF camera 151, 351, 651 Synchronization signal generating unit 152, 653 Irradiation spot designating unit 155, 355a, 355b Signal processing unit 156, 356 Image output unit 352, 652 Irradiation angle designating unit

Claims

1. A distance measuring method comprising: a computer shifting an irradiation spot of laser light from the position of a light receiving pixel corresponding to the irradiation spot, emitting the laser light to the shifted irradiation spot; receiving reflected light of the emitted laser light from an object to be measured at the light receiving pixel corresponding to the irradiation spot; and measuring a distance to the object to be measured based on the timing of emitting the laser light and the timing of receiving the reflected light.

2. The distance measuring method according to claim 1, further comprising judging whether or not the luminance intensity of the reflected light received by a light receiving pixel corresponding to an arbitrary irradiation spot exceeds a threshold value before emitting the light, and shifting the irradiation spot comprises shifting the irradiation spot corresponding to the light receiving pixel of the arbitrary irradiation spot whose luminance intensity is judged to exceed the threshold value.

3. The distance measuring method according to claim 1, wherein shifting the irradiation spot comprises shifting the irradiation spot of the laser light to a point-symmetric position on a screen relative to the light receiving pixel of the laser light.

4. The distance measuring method according to claim 2, wherein shifting the illumination spot includes: matching the position of the illumination spot with the position of the light receiving pixel when the luminance intensity of the reflected light received by the light receiving pixel does not exceed the threshold value.

5. The distance measuring method according to claim 2, wherein shifting the illumination spot includes: when the luminance intensity of the reflected light received by the light receiving pixel exceeds the threshold value, selecting the light receiving pixel having the luminance intensity of the reflected light lower than the threshold value; and shifting the illumination spot to the position of the selected light receiving pixel.

6. The distance measurement method according to claim 1, wherein the light receiving unit having a plurality of light receiving pixels is a 3D-LiDAR using PAD pixels.

7. A distance measuring method for a distance measuring device having a first device having a first light emitting unit that emits laser light to an irradiation spot, and a second device having a second light emitting unit that emits laser light to the irradiation spot and a second light receiving unit that receives reflected light from an object to be measured, the distance measuring method including: a computer causes the first light emitting unit to emit the laser light to the irradiation spot; causes the second light receiving unit to receive reflected light of the emitted laser light from the object to be measured at a light receiving pixel corresponding to the irradiation spot; and measures a distance to the object to be measured based on the emission timing of the laser light from the first light emitting unit and the reception timing of the reflected light by the second light receiving unit.

8. The distance measuring method according to claim 7, wherein the first device has a first light receiving unit that receives reflected light of the laser light from the object to be measured, and includes the steps of: emitting the laser light from the second light emitting unit to the irradiation spot when the luminance intensity of the reflected light received at the light receiving pixel corresponding to the irradiation spot exceeds a threshold value; receiving the reflected light of the laser light emitted from the second light emitting unit from the object to be measured at the light receiving pixel corresponding to the irradiation spot of the first light receiving unit; and measuring the distance to the object to be measured based on the emission timing of the laser light from the second light emitting unit and the reception timing of the reflected light by the first light receiving unit.

9. The distance measuring method according to claim 8, further comprising: matching the positions of the illumination spot and the light receiving pixel when the luminance intensity of the reflected light received by the light receiving pixel corresponding to the illumination spot does not exceed a threshold value.

10. A distance measuring method as described in claim 7, comprising alternately controlling the timing of emission of the laser light from the first light-emitting unit and the timing of emission of the laser light from the second light-emitting unit.

11. A distance measuring method according to claim 8, comprising complementarily controlling the timing of reception of the reflected light by the first light receiving section and the timing of emission of the laser light by the second light receiving section.

12. A distance measuring method as described in claim 8, comprising controlling the timing of emitting the laser light from the first light emitting unit to coincide with the timing of receiving the reflected light from the second light receiving unit, and controlling the timing of receiving the reflected light from the first light receiving unit to coincide with the timing of emitting the laser light from the second light emitting unit.

13. The distance measuring method according to claim 8, wherein an angle formed by a first virtual line connecting the first light emitting unit of the first device and the object to be measured and a second virtual line connecting the second light receiving unit of the second device and the object to be measured is smaller than 90 degrees.

14. The distance measuring method according to claim 7, wherein the first device is a light source, and the second device is an imaging device.

15. The distance measuring method according to claim 7, further comprising: switching to a normal mode in which the position of the irradiation spot coincides with the position of the light receiving pixel.

16. A distance measuring method as described in claim 8, comprising: when the luminance intensity of the reflected light received by the light receiving pixel corresponding to the irradiation spot exceeds a threshold value, shifting a laser light from the position of the light receiving pixel corresponding to the irradiation spot and emitting it to the object to be measured; receiving the reflected light from the object to be measured of the emitted laser light at the light receiving pixel corresponding to the irradiation spot; and measuring the distance to the object to be measured based on the timing of emitting the laser light and the timing of receiving the reflected light.

17. A distance measuring device comprising: an emission control unit that shifts an irradiation spot of laser light from the position of a light receiving pixel corresponding to the irradiation spot and emits the laser light to the shifted irradiation spot; a light receiving control unit that receives reflected light from a measurement object of the emitted laser light at the light receiving pixel corresponding to the irradiation spot; and a measurement unit that measures a distance to the measurement object based on the emission timing of the laser light and the reception timing of the reflected light.

18. A distance measuring device having a first device having a first light emitting unit that emits laser light to an irradiation spot, and a second device having a second light emitting unit that emits laser light to the irradiation spot and a second light receiving unit that receives reflected light from a measurement object, comprising: an emission control unit that causes the first light emitting unit to emit the laser light to the irradiation spot; a light receiving control unit that causes the second light receiving unit to receive reflected light of the emitted laser light from the measurement object at a light receiving pixel corresponding to the irradiation spot; and a measurement unit that measures the distance to the measurement object based on the emission timing of the laser light from the first light emitting unit and the reception timing of the reflected light by the second light receiving unit.

19. A program for causing a computer to function as an emission control unit that shifts an irradiation spot of laser light from the position of a light receiving pixel corresponding to the irradiation spot and emits the laser light to the shifted irradiation spot, a light receiving control unit that receives reflected light from a measurement object of the emitted laser light at the light receiving pixel corresponding to the irradiation spot, and a measurement unit that measures the distance to the measurement object based on the emission timing of the laser light and the reception timing of the reflected light.

20. A program for a distance measuring device including a first device having a first light-emitting unit that emits laser light to an irradiation spot, and a second device having a second light-emitting unit that emits laser light to the irradiation spot and a second light-receiving unit that receives reflected light from a measurement object, the program causing a computer to function as: an emission control unit that causes the first light-emitting unit to emit the laser light to the irradiation spot; a light-receiving control unit that causes the second light-receiving unit to receive reflected light of the emitted laser light from the measurement object at a light-receiving pixel corresponding to the irradiation spot; and a measurement unit that measures the distance to the measurement object based on the emission timing of the laser light from the first light-emitting unit and the reception timing of the reflected light by the second light-receiving unit.

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