Distance measuring device

Abstract

To minimize the increase in measurement time while ensuring detection performance for distant objects. [Solution] In this distance measuring device, the unit frame for distance measurement is divided into multiple subframes, and the groups of measurement directions assigned to each of the multiple subframes are set to be mutually exclusive. When multiple reflection points are detected in a first subframe which is relatively earlier than the multiple subframes, the controller sets a first region including each of the reflection points based on the time of flight of light at each of the reflection points or a converted value equivalent to the time of flight of light. In a second subframe which is at least one of the multiple subframes which is relatively later than the first subframe, the controller controls the operation of the light source and the deflector so that measurement light is not irradiated from the group of measurement directions included in the second subframe in one or more measurement directions that overlap with the first region, and measurement light is irradiated in measurement directions that do not overlap with the first region.

Description

Technical Field

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

Background Art

[0002] Devices that perform object detection by irradiating laser light and detecting the reflected light thereof are known. For example, Japanese Unexamined Patent Application Publication No. 2022-112828 (Patent Document 1) discloses a light conversion element that generates charges according to incident light, a plurality of pixel circuits each including N (N≧3) charge accumulation units that accumulate charges in a frame period, a pixel drive circuit that performs on / off processing of a transfer transistor that transfers charges to the charge accumulation units at an accumulation timing synchronized with an optical pulse and distributes and accumulates the charges, a light source unit that irradiates an optical pulse, a distance image processing unit that obtains the distance to a subject based on the amount of accumulated charges in the charge accumulation units, and a measurement control unit that accumulates charges for an integration count set for a measurement zone set to a zone threshold value set corresponding to the distance in any one of the measurement zones to which the measured distance belongs, and irradiates the optical pulse by increasing the pulse period, which is the emission interval of the optical pulse, as the integration count increases. A distance image capturing device is described.

[0003] The above distance image capturing device is considered to have the advantage of satisfying the safety standard (eye-safe) for the human body even when pulsed light is continuously irradiated. However, when the subject is located far away, as the integration count increases and the pulse period, which is the emission interval of the pulsed light, becomes longer, there is room for improvement in that the measurement time increases.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the specific aspects of this disclosure is to provide a technology for a distance measuring device using laser light that can suppress the increase in measurement time while also ensuring detection performance for distant objects. [Means for solving the problem]

[0006] A distance measuring device according to one embodiment of the present disclosure is: A device for measuring the distance between an object, A light source that emits laser light, A deflector that generates measurement light by deflecting the aforementioned laser light, A sensor that receives reflected light generated when the measurement light is irradiated onto the object, A controller that controls the operation of the light source and the deflector, and measures the distance to the object based on the reflected light received by the sensor, Includes, In the distance measurement by the controller, the unit frame is divided into a plurality of subframes, and the group of measurement directions assigned to each of the plurality of subframes is set to be mutually exclusive. The aforementioned controller, If multiple reflection points are detected in the first subframe, which is relatively earlier among the multiple subframes, a first region including each of those reflection points is set based on the optical time of flight at each of those reflection points or an equivalent value. In a second subframe which is at least one of a plurality of subframes that occur relatively later than the first subframe, the operation of the light source and the deflector is controlled such that the measurement light is not irradiated in one or more of the measurement directions that overlap with the first region from the group of measurement directions included in the second subframe, and the measurement light is irradiated in the measurement directions that do not overlap with the first region. It is a distance measuring device.

[0007] According to the above configuration, it is possible to provide a technology for a distance measuring device using laser light that can suppress the increase in measurement time while also ensuring detection performance for distant objects. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows the configuration of a distance measuring device according to one embodiment. [Figure 2] Figure 2 is a diagram illustrating an example of the arrangement of the light source and light receiver, as well as the field of view for light reception. [Figure 3] Figure 3 is a diagram illustrating the measurement direction group based on the measurement light. [Figure 4] Figure 4 is a schematic diagram showing objects present within the scanning area FOI. [Figure 5] Figure 5 illustrates the assignment of sub-direction groups. [Figure 6] Figure 6A is a diagram illustrating the measurement direction and reflection point in subframe 0. Figure 6B is a diagram illustrating the measurement direction and reflection point in subframe 1. [Figure 7] Figure 7A is a diagram illustrating the measurement direction and reflection point in subframe 2. Figure 7B is a diagram illustrating the measurement direction and reflection point in subframe 3. [Figure 8] Figure 8 is a diagram illustrating the measurement direction and reflection point for one frame, which combines subframes 0 to 3. [Figure 9] Figure 9 is a flowchart showing the information processing flow related to measurement for one frame in the distance measuring device of this embodiment. [Figure 10] Figures 10A and 10B are diagrams illustrating the method for setting the region B that is subject to thinning in the measurement direction, respectively. [Figure 11] Figures 11A and 11B are diagrams illustrating the method for setting the region B that will be subjected to thinning in the measurement direction, respectively. [Figure 12]Figure 12A shows the region BOA,SF0, which is the union of the regions BOA,SF0,m, BOA,SF0,n, BOA,SF0,o, and BOA,SF0,p. Figure 12B is a diagram illustrating how to set region B, which is subject to thinning in the measurement direction. [Figure 13] Figure 13 shows an example of a pre-defined pattern for region B. [Figure 14] Figure 14A illustrates an example of setting a small number of sub-direction groups to be subject to decimation. Figure 14B illustrates an example of sequentially changing the assignment pattern P1 to P4 every frame. [Figure 15] Figure 15 is a flowchart showing the information processing flow for one frame of measurement in the distance measuring device of Modified Example 1. [Figure 16] Figure 16A illustrates an example of how to divide the scanning target area (FOI) into multiple parts. Figure 16B illustrates the enlarged central region. [Figure 17] Figure 17 illustrates a method for changing the decimation parameters for each portion of the scanned area (FOI). [Figure 18] Figure 18 shows an example of a modified configuration of the light source unit. [Modes for carrying out the invention]

[0009] Figure 1 shows the configuration of a distance measuring device according to one embodiment. The distance measuring device (object detection device) of this embodiment uses laser light, which is a measuring light (emitted light), to perform an optical scan into the target space, receives the reflected light generated when the measuring light strikes an object, and uses the time it takes to obtain the reflected light (time of flight of light) to detect the position and relative distance of objects in the target space. It is composed of a control unit (controller) 1, a light source unit 2, and a light receiving unit 3. In other words, the distance measuring device of this embodiment operates using the time of flight method.

[0010] The control unit 1 controls the overall operation of the distance measuring device, and can be realized, for example, by using a computer system equipped with a CPU, ROM, RAM, etc., and having the computer system execute a predetermined operation program. To make the functions realized by the execution of the operation program in the control unit 1 easier to understand, each function is represented as a functional block, and the control unit 1 is composed of a measurement control unit (measurement control function) 11, a deflection control unit (deflection control function) 12, a lighting control unit (lighting control function) 13, a distance measuring unit (distance measuring function) 14, and a communication unit (communication function) 15.

[0011] The measurement control unit 11 controls the operation of the deflection control unit 12, the lighting control unit 13, and the distance measuring unit 14. The measurement control unit 11 also has a thinning processing unit (thinning processing function) for performing a thinning process to reduce the emission direction (measurement direction) of the measurement light.

[0012] The deflection control unit 12 controls the mirror 22 via the driver 21 of the light source unit 2 to periodically deflect it in a specified angle change pattern (typically a raster scan with uniform scan line spacing).

[0013] The lighting control unit 13 controls the PCSEL 24 via the light source driver 23 so that it emits laser light according to the pulse conditions instructed by the measurement control unit 11.

[0014] The distance measuring unit 14 uses the timing of the measurement light generation instruction by the lighting control unit 13 and the received light signal obtained from the light receiving circuit 34 of the light receiving unit 3 to measure the distance between objects in the target space based on the timing of the measurement light emission and reception and the time difference. In addition, the measurement control unit 11 detects the three-dimensional position of the object based on the timing of the measurement light emission and reception.

[0015] The communication unit 15 receives point cloud information (a collection of three-dimensional positions) obtained by the distance measurement unit 14 from the measurement control unit 11 and transmits this point cloud information to an external device (not shown).

[0016] The light source unit 2 generates measurement light, which is a narrow-angle beam laser light, and emits it in various directions within a predetermined range. It consists of a driver 21, a mirror 22, a light source driver 23, and a PCSEL 24.

[0017] The driver 21 is connected to both the control unit 1 and the mirror 22, and under the control of the deflection control unit 12 of the control unit 1, generates a drive signal to control the operation of the mirror 22 and supplies it to the mirror 22.

[0018] Mirror 22 has a reflective surface and is configured to rotate around two orthogonal axes, and is a two-dimensional deflector that deflects the laser light emitted from the Photonic-Crystal Surface-Emitting Laser (PCSEL) 24. Mirror 22 rotates, for example, around a main axis (first axis) and a secondary axis (second axis) orthogonal to the main axis, and is constructed using, for example, a MEMS mirror. This mirror 22 rotates based on a drive signal supplied from the driver 21, scanning the laser light along two directions within the target space. The measurement light generated by the scanning by mirror 22 is emitted into the external space (scanning target area) from an opening 25 appropriately provided in the light source unit 2. In the figure, RH indicates the deflection direction due to rotation of mirror 22 in the main axis direction, and RV indicates the deflection direction due to rotation of mirror 22 in the secondary axis direction.

[0019] The light source driver 23 is connected to both the control unit 1 and the PCSEL 24. Under the control of the lighting control unit 13 of the control unit 1, it generates a drive signal to control the operation of the PCSEL 24 and supplies it to the PCSEL 24.

[0020] PCSEL24 is a near-infrared photonic crystal surface-emitting laser that emits a narrow-angle beam of laser light onto mirror 22. The laser light emitted from PCSEL24 is a beam with a divergence angle that is equivalent to (or less than) the angular resolution of the distance measuring device. Although PCSEL24 is an example of a light source, the light sources that can be used in this disclosure are not limited to this, and various laser light sources can be used, preferably those that can emit a narrow-angle beam of laser light. The laser light emitted from PCSEL24 can be, for example, pulsed light with a wavelength of 940 nm and a divergence angle of 0.1°. In other words, the light emitted from the light source unit 2 should be a beam with a divergence angle that is equivalent to (or less than) the angular resolution of the distance measuring device. Furthermore, the light source unit 2 may also be equipped with an optical system that shapes the beam shape of the emitted light.

[0021] The light-receiving unit 3 receives reflected light generated when measurement light is irradiated onto an object and generates a light-receiving signal, and is composed of a lens 31, an optical filter 32, a sensor 33, and a light-receiving circuit 34.

[0022] Lens 31 collects the reflected light generated when the measurement light from PCSEL24 is shone onto an object.

[0023] The optical filter 32 is positioned after the lens 31 and blocks light in a different wavelength range than the measurement light, while transmitting light in the same wavelength range as the measurement light.

[0024] The sensor 33 detects light incident on it via the optical filter 32. The sensor 33 in this embodiment includes a plurality of light-receiving elements arranged along two directions.

[0025] The light receiving circuit 34 generates a light-receiving signal by applying predetermined signal processing (e.g., amplification, frequency filtering, current-to-voltage conversion, etc.) to the output of the sensor 33. The generated light-receiving signal is supplied to the distance measuring unit 14 of the control unit 1.

[0026] Figure 2 is a diagram illustrating an example of the arrangement of the light source and light receiver and the field of view. In the illustrated example, the light source 2 and light receiver 3 are arranged along the Y direction (vertical direction). The measurement light L(α,β) emitted from the light source 2 is scanned in two dimensions along the X and Y directions (see scanning trajectory a). In this example, the scanning direction along the X direction is considered the main scanning direction. The entire range scanned by the measurement light L(α,β) corresponds to the field of view D of the sensor 33. Each region obtained by dividing the field of view D at predetermined intervals in the X and Y directions is defined as a partial field of view DS. This partial field of view DS may correspond to one of the multiple light-receiving elements included in the sensor 33, or it may correspond to a cluster of several adjacent light-receiving elements. Note that α and β are variables representing the rotation angle of the MEMS mirror 22, where α is the principal axis rotation angle θ. H β is the sub-axis rotation angle θ V This corresponds to the measurement light L(α,β), which is the rotation angle of the principal axis θ. H =α, sub-axis rotation angle θ V The measurement light when =β is shown.

[0027] The deflection control unit 12 of the control unit 1 controls the pre-set spindle rotation angle θ. H and sub-axis rotation angle θ V The deflection angle of the mirror 22 is controlled by controlling the driver 21 of the light source unit 2 based on this. This controls the preset main axis rotation angle θ. H and sub-axis rotation angle θ V Measurement light is emitted in a direction determined based on each of these factors. The reflected light generated by the measurement light is received by the light receiving unit 3, and the group of received signals is processed to obtain the distance between the reflective object and each receiving portion of the field of view DS.

[0028] Figure 3 is a diagram illustrating the measurement direction group using measurement light. The measurement control unit 11 controls the direction in which the measurement light is irradiated (hereinafter referred to as "measurement direction") by controlling the deflection control unit 12 and the lighting control unit 13. Specifically, the measurement direction is set at approximately fixed angles set based on the angular resolution so as to cover the scanning target area FOI. The scanning target area FOI is the area irradiated by the measurement light. The measurement direction group can also be said to be a group of deflection angles corresponding to the position of the target to which the measurement light is irradiated. As an example, the measurement direction is set in 0.1° increments in both the H direction and the V direction. In the figure, each measurement direction is shown as a circle. As another example, the scanning target area FOI can be set to a range where the H direction is 90° and the V direction is 12°. Note that the measurement direction does not necessarily have to be uniform throughout the entire scanning target area FOI, but here we use an example where the measurement direction is evenly distributed for the sake of clarity in the explanation.

[0029] The measurement direction group can be divided into four sub-direction groups A0, A1, A2, and A3, as shown in the example. In other words, the smallest unit frame for acquiring data of the measurement direction group covering the scanning target area FOI can be divided into subframes corresponding to each sub-direction group for measurement. The measurement direction groups included in each sub-direction group A0, A1, A2, and A3 are mutually exclusive. That is, the measurement direction groups included in sub-direction group A0 are not included in the other sub-direction groups A1, A2, and A3. Similarly, the measurement direction groups included in sub-direction group A1 are not included in the other sub-direction groups A0, A2, and A3, the measurement direction groups included in sub-direction group A2 are not included in the other sub-direction groups A0, A1, and A3, and the measurement direction groups included in sub-direction group A3 are not included in the other sub-direction groups A0, A1, and A2.

[0030] In the illustrated example, for each of the sub-direction groups A0 to A3, the measurement directions are arranged intermittently with one space between them in each of the H direction and the V direction. The sub-direction group A1 has the measurement directions arranged with a shift of one in the H direction with respect to the sub-direction group A0. The sub-direction group A2 has the measurement directions arranged with a shift of one in the V direction with respect to the sub-direction group A0. The sub-direction group A3 has the measurement directions arranged with a shift of one in each of the H direction and the V direction with respect to the sub-direction group A0. It can also be said that the sub-direction group A3 has the measurement directions arranged with a shift of one in the V direction with respect to the sub-direction group A1, and it can also be said that the sub-direction group A3 has the measurement directions arranged with a shift of one in the H direction with respect to the sub-direction group A2.

[0031] The density (i.e., the number of measurement direction groups) of the measurement direction groups included in each of the sub-direction groups A0 to A3 is substantially the same. Here, "substantially the same" means that there may be an error of about several (for example, 5 to 10) in the number of measurement direction groups included in each of the sub-direction groups A0 to A3. Note that the number of divisions of the sub-direction group is not limited to four. Also, the measurement direction groups included in each sub-direction group only need to be arranged mutually exclusively, and are not limited only to the arrangement in the above example.

[0032] FIG. 4 is a diagram schematically showing an object existing in the scanning target area FOI. Here, an object existing at a position relatively close to the distance measuring device is O A and an object existing at a relatively distant position is O B In the present embodiment, a unit frame, which is the minimum unit for performing three-dimensional measurement, is divided into four sub-frames, and the above-described sub-direction groups A0 to A3 are respectively assigned to each sub-frame for measurement (see FIG. 5). At this time, in the sub-frame 0, which is the first sub-frame (i.e., the sub-frame with an earlier timing relatively), reflection points corresponding to each of the objects O A and O B are detected. Correspondingly, in the subsequent sub-frames, i.e., sub-frames 1 to 3, which are sub-frames with a relatively later timing, the object O AMeasurement light in the direction containing the corresponding reflection point is omitted. Below, this process will be explained in detail, assuming the arrangement of each object as exemplified in Figure 4.

[0033] Figure 6A illustrates the measurement direction and reflection point in subframe 0. Figure 6B illustrates the measurement direction and reflection point in subframe 1. Figure 7A illustrates the measurement direction and reflection point in subframe 2. Figure 7B illustrates the measurement direction and reflection point in subframe 3. Figure 8 also illustrates the measurement direction and reflection point for a unit frame combining subframes 0 to 3. Note that in each figure, the number of measurement directions has been reduced compared to the example in Figure 3 above for simplicity of explanation.

[0034] As shown in Figure 6A, region GR OA,SF0 Object O A Multiple reflection points (shown with patterns in the figure) are detected due to reflected light from the region GR, and OB,SF0 Object O B A single reflection point (shown as a pattern in the figure) is detected due to the reflected light from the source. Correspondingly, as shown in Figure 6B, region B is the area where measurement is omitted in the following subframes, i.e., the area where the measurement direction is reduced. OA,SF0 B OB,SF0 Each of these is set. In the diagram, each area B OA,SF0 B OB,SF0 Each region B is shown as a rectangle. OA,SF0 B OB,SF0 Detailed instructions on how to configure this will be provided later. Configured area B OA,SF0 B OB,SF0 Each measurement direction included in each of these is then filtered out from the respective measurement direction groups A1 to A3 in the subsequent subframes, subframes 1, 2, and 3.

[0035] As shown in Figure 6B, for example, from sub-direction group A1 in subframe 1, region B OA,SF0Correspondingly, a total of 6 measurement directions are thinned out: 3 in the H direction and 2 in the V direction. Note that in the example of Figure 6B, region B OB,SF0 Since there are no measurement directions included in region B OB,SF0 There are no measurement directions that are thinned out in response to this. Also, in subframe 1, region GR OB,SF1 Object O B A corresponding reflection point is detected.

[0036] As shown in Figure 7A, from sub-direction group A2 in subframe 2, region B OA,SF0 Correspondingly, a total of 6 measurement directions are thinned out: 2 in the H direction and 3 in the V direction. Also, region GR OB,SF0 , area GR OB,SF1 If there are measurement directions corresponding to each of these, they are thinned out. Note that in Figure 7A, region GR OB,SF0 , area GR OB,SF1 The case where there is no measurement direction to be thinned out corresponding to each of the values ​​is shown.

[0037] Similarly, as shown in Figure 7B, from sub-direction group A3 in subframe 3, region B OA,SF0 Correspondingly, a total of 6 measurement directions are thinned out: 3 in the H direction and 2 in the V direction. Also, region GR OB,SF01 , area GR OB,SF1 If there are corresponding measurement directions for each of these, they are thinned out. Note that in Figure 7B, region GR OB,SF01 , area GR OB,SF1 The case where there is no measurement direction to be thinned out corresponding to each of the values ​​is shown.

[0038] As shown in Figure 8, when viewed as a single unit frame encompassing all subframes 0-3, object O A Four measurement directions corresponding to object O B Two corresponding measurement directions are obtained. Each measurement direction is indicated by a pattern in the figure. Also, object O A The H direction and V direction each contain five measurement directions, including four corresponding measurement directions, for object O AThe measurement directions are thinned out, except for the four measurement directions corresponding to the specified area. The thinned-out measurement directions are indicated by dashed circles in the figure. In other words, when viewed as a whole unit frame, light is shone on each measurement direction represented by solid circles in Figure 8. The dashed circles represent area B. OA,SF0 The measurement direction overlaps with the measurement direction where the measurement light is not irradiated, and the solid circle represents region B. OA,SF0 This is a measurement direction that does not overlap with the other direction and is the measurement direction in which the measurement light is irradiated.

[0039] Figure 9 is a flowchart showing the information processing flow related to the measurement of one frame (one unit frame) in the distance measuring device of this embodiment. Note that the flowchart shown here is an example, and the order of each process can be changed or other processes can be added as long as it does not cause contradictions or inconsistencies in the results of the information processing.

[0040] The measurement control unit 11 creates (N+1) sub-direction groups from the measurement direction group set corresponding to the angular resolution (step S1). Specifically, for example, as shown in Figure 3 above, four sub-direction groups are created. Then, the measurement control unit 11 assigns a sub-direction group to each subframe (step S2). Specifically, for example, as shown in Figure 5 above, a correspondence relationship between each subframe and each sub-direction group is set.

[0041] Furthermore, if the correspondence between each sub-direction group and each subframe is predetermined, steps S1 and S2 can be omitted. For example, data indicating the correspondence between each sub-direction group and each subframe can be prepared in advance and stored in memory (not shown), and steps S1 and S2 can be omitted by the measurement control unit 11 reading this data. Alternatively, information such as each sub-direction group may be pre-programmed into the operation program.

[0042] While the measurement process for all subframes is not yet complete (step S3;N), the measurement control unit 11 controls the deflection control unit 12 and the lighting control unit 13 to irradiate measurement light in each measurement direction based on the corresponding sub-direction group, starting from subframe 0, and controls the distance measurement unit 14 to measure the distance based on the reflected light (step S4). The measurement control unit 11 also performs a omission process (decimation process) for measurement directions in subsequent subframes based on each reflection point obtained by the measurement (step S5). After that, the process returns to step S3, and while the measurement process for all subframes is not yet complete (step S3;N), the processes in steps S4 and S5 are repeated.

[0043] When the measurement process is completed for all subframes (step S3; Y), the measurement control unit 11 combines the measurement results for each subframe to obtain the measurement result for one unit frame (step S6). This completes the measurement for one unit frame. Thereafter, steps S1 to S6 are repeated according to the required number of unit frames.

[0044] Figures 10A, 10B, 11A, and 11B are diagrams illustrating the method for setting the region B that will be subjected to thinning in the measurement direction. Here again, the object O shown in Figure 4 above is shown. A The explanation will proceed on the premise that object O exists. In each figure, object O A The four reflection points are P SF0,m , P SF0,n , P SF0,o , P SF0,p This is how it is expressed. Region GR OA,SF0 This includes these four reflection points.

[0045] As shown in Figure 10A, there is a certain reflection point P SF0,m Assuming a circle with radius d centered at a certain distance, and with the direction of the reflection point set to 0°, the angle conversion value of the circle is S. OA,SF0,m Therefore, the area B to be thinned out OA,SF0,m The size is the angle equivalent value S OA,SF0,mIt is set to enclose the area. The radius d of the circle can be set to a value of, for example, 5 to 15 mm. This is a value that corresponds to the distance from the reflection point to the human pupil (pupil diameter when open). That is, area GR OA,SF0 From the light source 2 to the reflection point P SF0,m The distance to is D(P SF0,m ) If the reflection point P SF0,m The radius is the angle-converted value centered at arctan(d / D(P)). SF0,m Circle S in [rad] OA,SF0,m To omit measurements in the direction included in circle S (emission of light), OA,SF0,m Region B which contains OA,SF0,m This is set. Other reflection point P SF0,n , P SF0,o , P SF0,p The same applies to the angle conversion value S, as shown in Figures 10B, 11A, and 11B, respectively. OA,SF0,n、 S OA,SF0,o、 S OA,SF0,p Corresponding to each of them, region B OA,SF0,n B OA,SF0,o B OA,SF0,p The size is set. As a result, as shown in Figure 12A, region GR OA,SF0 In the vicinity of region B OA,SF0,m B OA,SF0,n B OA,SF0,o B OA,SF0,p The region B is the union of the sets B. OA,SF0 Each measurement direction included within will be filtered out from each sub-direction group A0 to A3.

[0046] On the other hand, as shown in Figure 12B, a relatively distant object O B The corresponding reflection point P SF1,s Corresponding circle S OB,SF1,s The same method is used for setting this circle S OB,SF1,s Because the size is less than the angular resolution of the measurement direction group, region B is subject to decimation. OB,SF0 The reflection point P SF1,s This means that it will not include any measurement directions other than the corresponding one.

[0047] In the above embodiment, it was assumed that the region B to be thinned out was set each time. However, patterns of region B corresponding to the distance between reflection points (or an equivalent converted value, such as the time of flight of light measured at the reflection point) may be set in advance and stored in a memory not shown, and those patterns of region B may be used. That is, depending on the distance between reflection points obtained, patterns b1, b2, b3, and b4, as exemplified in Figure 13, can be selected.

[0048] In the illustrated example, the horizontal axis represents distance (or time of light flight), and the value increases as you move to the right in the figure. Pattern b1 is the pattern for when the distance is relatively short, i.e., when the object is nearby, and is set as a rectangle with a relatively large area. Pattern b2 is for when the distance is farther than in pattern b1, and is set as a rectangle with the four corners of pattern b1 removed. Pattern b3 is for when the distance is farther than in pattern b2, and is set as a rectangle similar to pattern b1, but with a smaller area than patterns b1 and b2. Pattern b4 is for when the distance is farther than in pattern b3, and, similar to pattern b2, is set as a rectangle with the four corners of pattern b2 removed, and has a smaller area than patterns b1, b2, and b3. By arranging each of these patterns b1 to b4 around the reflection point according to the relative distance (or time of light flight) of the reflection point, the area B to be thinned can also be defined. As illustrated, the shape of each pattern, i.e., the area to be thinned that encloses the circle centered on the direction of the reflection point, does not necessarily have to be rectangular. The shape may consist of a single rectangle or a collection of multiple rectangles. In other words, it is preferable to minimize the area included in region B but not included in the angle conversion value S, so that the number of measurement directions that are thinned out does not become unnecessarily large.

[0049] According to the embodiments described above, a technology can be obtained for a distance measuring device using laser light that suppresses the increase in measurement time while also ensuring detection performance for distant objects.

[0050] According to this embodiment, by thinning the measurement direction of the measurement light in response to objects located at a relatively close distance, it is possible to prevent excessive light from being shone on nearby objects in a short period of time. As a result, even if the intensity of the light used for measurement is increased, the safety of people within the measurement range is not compromised. Furthermore, there is no need to extend the time required for measurement of a unit frame.

[0051] Furthermore, according to this embodiment, since no thinning of the measurement direction occurs for objects located at a distance, there is the advantage that the detectability of distant objects is not impaired. Even for nearby objects, a certain angular resolution is guaranteed even if thinning occurs, and since nearby objects are illuminated with measurement light at narrow intervals, the object detection performance is ensured. The above operation does not require increasing or decreasing the output of measurement light from the light source, so the device configuration can be simple, and therefore the device can be made smaller.

[0052] This disclosure is not limited to the embodiments described above, and can be implemented in various modified forms within the scope of the gist of this disclosure. For example, the number of sub-direction groups and sub-frames in the embodiments described above was four, but this is not limited to these and can be set as appropriate. Furthermore, the arrangement of measurement directions included in each sub-direction group is not limited to the embodiments described above, as long as they are mutually exclusive.

[0053] (Variation 1) In the embodiment described above, all sub-direction groups corresponding to subframes other than the first subframe were subject to decimation (omission). However, the number of sub-direction groups subject to decimation may be reduced. As an example, consider four subframes 0 to 3 and four corresponding sub-direction groups A0 to A3, similar to the embodiment described above. In this case, as shown in Figure 14A, for example, two sub-direction groups A2 and A3 corresponding to two subframes 2 and 3 may be subject to decimation, while sub-direction group A1 corresponding to subframe 1 may be excluded from decimation. This is just one example, and other combinations are possible. For example, sub-direction groups A1 and A3 corresponding to subframes 1 and 3 may be subject to decimation.

[0054] Figure 15 is a flowchart showing the information processing flow for one frame of measurement in the distance measuring device of Modification 1. Note that this flowchart is an example, and the order of each process can be changed or other processes can be added, as long as it does not result in contradictions or inconsistencies in the information processing results.

[0055] Steps S101, S102, S104, S105, and S107 in the flowchart shown in Figure 15 are the same processes as steps S1, S2, S3, S4, and S6 in the flowchart shown in Figure 9 of the above-described embodiment, so their explanation is omitted. Step S103 is the step in which the measurement control unit 11 sets the subframes and sub-direction groups (see Figure 14A) that will be subject to decimation processing. In step S106, decimation processing is performed only for the subframes that have been set as targets for decimation processing, in the corresponding sub-direction groups. According to this modified example 1, in addition to obtaining the same effects as the above-described embodiment, the effect of being able to adjust the degree of decimation of the measurement direction groups can be obtained.

[0056] (Modification 2) In the process of assigning sub-direction groups for each subframe in step S2 of the flowchart shown in Figure 9 in the above-described embodiment, or in step S102 of the flowchart shown in Figure 15 in Modification 1, the sub-direction groups assigned to each subframe may be changed every frame. As an example, four subframes 0 to 3 and four corresponding sub-direction groups A0 to A3 are assumed, similar to the above-described embodiment.

[0057] In this case, as illustrated in Figure 14B, the assignment patterns can be sequentially changed from P1 to P4 for each unit frame. Specifically, in one unit frame, sub-direction groups A0, A1, A2, and A3 are assigned to each subframe 0, 1, 2, and 3. In the next unit frame, sub-direction groups A1, A2, A3, and A0 are assigned to each subframe 0, 1, 2, and 3. In the next unit frame, sub-direction groups A2, A3, A0, and A1 are assigned to each subframe 0, 1, 2, and 3. In the next unit frame, sub-direction groups A3, A0, A1, and A2 are assigned to each subframe 0, 1, 2, and 3. By repeating this sequentially, the direction in which measurement directions are thinned out changes even when an object is nearby, thus avoiding a situation where a fixed measurement direction is continuously thinned out and not measured. In other words, by considering a unit frame that combines subframes, even nearby areas can be measured in detail.

[0058] (Variation 3) The parameters for the decimation process may be configured differently for each part of the scanning region FOI. For example, as shown in Figure 16A, the scanning region FOI is divided into a central region FOI_PH and a peripheral region FOI_PL. In this example, the peripheral region FOI_PL is the part of the scanning region FOI other than the central region FOI_PH. As illustrated in Figure 16B, for reflection points in the central region FOI_PH' (see Figure 16B), which is an enlargement of the central region FOI_PH by an angle equivalent to the pupil radius, decimation can be performed in the corresponding sub-direction groups targeting subframes 1 to 3, and for reflection points in the peripheral region FOI_PL' of the central region FOI_PH', decimation can be performed in the corresponding sub-direction groups targeting subframes 2 to 3. In this modified example 3, the intensity of the pulsed light can be changed for each part of the scanning region FOI. Specifically, the intensity of the pulsed light as an integral value per unit frame can be made relatively higher in the peripheral region FOI_PL' than in the central region FOI_PH'. Therefore, the measurement operation can be performed more effectively.

[0059] (Modification 4) The measurement control unit 11 may extract the measurement directions that were subject to the decimation process (or the direction of the original reflection point) and store them in memory, and perform processing to supplement the decimated measurement directions. For example, it can be replaced with distance information corresponding to the original reflection point. This makes it possible to suppress differences in post-processing results such as object recognition on point cloud information between the distance measuring device according to this disclosure and conventional distance measuring devices.

[0060] (Variation 5) In the embodiments described above, an example was given in which a two-dimensional deflector, which is a deflector that can deflect in two directions, is used as the mirror 22 in the light source unit 2. However, the light source unit can also be configured using a light source that emits laser light with a long emission pattern shape in one direction and a mirror that can deflect in one direction. Figure 18 shows an example of the configuration of the light source unit according to Modification 5. The light source unit 2a shown in Figure 18 includes a driver 21, a mirror 22a, a light source driver 23, a VCSEL array 24a, and a lens array 26. The VCSEL array 24a according to Modification 5 is made up of multiple VCSEL light sources (Vertical Cavity Surface-Emitting Lasers) arranged in a straight line, and the overall emission pattern shape is substantially linear. By shaping the measurement light from the VCSEL array 24a with the lens array 26, the measurement light from the lens array 26 becomes light with a long emission pattern shape in one direction as a collection of multiple beams. The VCSEL array 24a is equipped with multiple elements arranged in one direction, and each element can be individually turned on or off. The mirror 22a can be deflected in the direction of RV. Light incident on the mirror 22a is reflected by the mirror 22a, resulting in light with an elongated emission pattern shape in the direction perpendicular to RV. Even with a light source unit 2a configured in this way, the same operation as in the embodiments described above can be achieved.

[0061] This disclosure has the following features: (Note 1) A device for measuring the distance between an object, A light source that emits laser light, A deflector that generates measurement light by deflecting the aforementioned laser light, A sensor that receives reflected light generated when the measurement light is irradiated onto the object, A controller that controls the operation of the light source and the deflector, and measures the distance to the object based on the reflected light received by the sensor, Includes, In the distance measurement by the controller, the unit frame is divided into a plurality of subframes, and the group of measurement directions assigned to each of the plurality of subframes is set to be mutually exclusive. The aforementioned controller, If multiple reflection points are detected in the first subframe, which is relatively earlier among the multiple subframes, a first region including each of those reflection points is set based on the optical time of flight at each of those reflection points or an equivalent value. In a second subframe which is at least one of a plurality of subframes that occur relatively later than the first subframe, the operation of the light source and the deflector is controlled such that the measurement light is not irradiated in one or more of the measurement directions that overlap with the first region from the group of measurement directions included in the second subframe, and the measurement light is irradiated in the measurement directions that do not overlap with the first region. Distance measuring device. (Note 2) The density of the measurement direction group assigned to each of the plurality of subframes is approximately equal. The distance measuring device described in Appendix 1. (Note 3) Each time the unit frame is repeated, the arrangement of the measurement direction group assigned to each of the multiple subframes is rearranged and set. Distance measuring device as described in Appendix 1 or 2. (Note 4) The first region is defined as a region formed by superimposing certain regions with each of the reflection points approximately at its center. The size of the certain region corresponding to each of the aforementioned reflection points is determined based on the optical time of flight or the converted value corresponding to each of the aforementioned reflection points. A distance measuring device as described in any of the appendices 1 to 3. (Note 5) The scanning area of ​​the measurement light includes a first irradiation target area which is a part and a second irradiation target area which is another part. The number of second subframes associated with the first irradiation target area and the number of second subframes associated with the second irradiation target area are set to different values. A distance measuring device as described in any of the appendices 1 to 4. (Note 6) Of the aforementioned plurality of subframes, all subframes other than the first subframe are designated as the second subframe. A distance measuring device as described in any of the appendices 1 to 5. (Note 7) The light source has a configuration in which a plurality of elements capable of individually controlling the emission of the laser light are arranged in one direction, The deflector is a one-dimensional deflector. A distance measuring device as described in any of the appendices 1 to 6. [Explanation of symbols]

[0062] 1: Control unit, 2: Light source unit, 3: Light receiving unit, 11: Measurement control unit, 12: Deflection control unit, 13: Lighting control unit, 14: Distance measurement unit, 15: Communication unit, 21: Driver, 22: Mirror, 23: Light source driver, 24: Light source, 31: Lens, 32: Optical filter, 33: Sensor, 34: Light receiving circuit

Claims

1. A device for measuring the distance between an object, A light source that emits laser light, A deflector that generates measurement light by deflecting the aforementioned laser light, A sensor that receives reflected light generated when the measurement light is irradiated onto the object, A controller that controls the operation of the light source and the deflector, and measures the distance to the object based on the reflected light received by the sensor, Includes, In the distance measurement by the controller, the unit frame is divided into a plurality of subframes, and the group of measurement directions assigned to each of the plurality of subframes is set to be mutually exclusive. The aforementioned controller, If multiple reflection points are detected in the first subframe which is relatively earlier among the multiple subframes, a first region including each of the reflection points is set based on the optical time of flight at each of the reflection points or an equivalent value. In a second subframe which is at least one of a plurality of subframes that occur relatively later than the first subframe, the operation of the light source and the deflector is controlled such that the measurement light is not irradiated in one or more of the measurement directions that overlap with the first region from the group of measurement directions included in the second subframe, and the measurement light is irradiated in the measurement directions that do not overlap with the first region. Distance measuring device.

2. The density of the measurement direction group assigned to each of the plurality of subframes is approximately equal. The distance measuring device according to claim 1.

3. Each time the unit frame is repeated, the arrangement of the measurement direction group assigned to each of the multiple subframes is rearranged and set. The distance measuring device according to claim 1.

4. The first region is defined as a region formed by superimposing certain regions with each of the reflection points approximately at their centers. The size of the certain region corresponding to each of the aforementioned reflection points is determined based on the optical time of flight or the converted value corresponding to each of the aforementioned reflection points. The distance measuring device according to claim 1.

5. The scanning area of ​​the measurement light includes a first irradiation target area which is a part and a second irradiation target area which is another part. The number of second subframes associated with the first irradiation target area and the number of second subframes associated with the second irradiation target area are set to different values. The distance measuring device according to claim 1.

6. Of the plurality of subframes, all except the first subframe are designated as the second subframe. The distance measuring device according to claim 1.

7. The light source has a configuration in which a plurality of elements capable of individually controlling the emission of the laser light are arranged in one direction, The deflector is a one-dimensional deflector. The distance measuring device according to claim 1.

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