Laser radar device

Abstract

To provide a laser radar device that improves in detection accuracy in a sparse region of an irradiation pattern of a laser beam.SOLUTION: A laser radar device comprises: a laser beam irradiation part for irradiating a target region R0 with a laser beam; and a pattern control part for controlling an irradiation pattern of a laser beam radiated to a target region R0. The pattern control part controls a beam diameter of a laser beam, and sets beam diameters of laser beams to different sizes in a region R1 where the density of measured points P of an irradiation pattern is relatively large density and in a sparse region R2 elsewhere. In the sparse region R2, a beam diameter of at least some of the measured points P is set to be larger compared to the beam diameter in the dense region R1.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a laser radar device that irradiates a target area with laser light and receives reflected light to detect an object. [Background technology]

[0002] Conventionally, LiDAR has been known as this type of laser radar device. LiDAR is an abbreviation for Light Detection and Ranging. This laser radar device irradiates a target area with laser light, receives reflected light of the irradiated laser light, and analyzes the reflected light to detect an object and obtain various information such as the distance to the object and the shape of the object. LiDAR can measure long distances, have a wide measurement range, and has high resolution, and is applied, for example, to collision prevention devices mounted on moving objects such as automobiles. However, increasing the resolution of LiDAR increases the number of ranging points, which in turn increases the calculation cost.

[0003] Therefore, a laser radar device that can reduce calculation costs due to higher resolution has been proposed, for example, as described in Patent Document 1. This laser radar device is mounted on a vehicle, and has a preset laser light irradiation pattern that corresponds to the vehicle's driving pattern, and changes the density distribution of the laser light irradiation pattern within the target area as appropriate depending on the vehicle's driving conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-329971 Summary of the Invention [Problem to be solved by the invention]

[0005] The laser radar device described in Patent Document 1 changes the density distribution of the laser beam irradiation pattern within the target area depending on the driving conditions, thereby enabling high resolution limited to the necessary area without excessively increasing the number of ranging points. However, areas of the laser beam irradiation pattern where the density of ranging points is relatively high are called dense areas, and other areas are called sparse areas, and the sparse areas have lower resolution than the dense areas. For this reason, the above-mentioned laser radar device may not be able to detect small objects cutting in or nearby objects in sparse areas.

[0006] In view of the above, an object of the present disclosure is to provide a laser radar device that can improve detection accuracy in sparse areas of a laser light irradiation pattern. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a laser radar device includes: A laser radar device that irradiates a target area with laser light and detects an object present in the target area, a laser light irradiation unit (3) that irradiates a target area with laser light; a pattern control unit (6) that controls the irradiation pattern of the laser light to be irradiated onto the target area; Each irradiation site of the laser light in the irradiation pattern is defined as a distance measurement point, and the area in the irradiation pattern where the density of the distance measurement points is higher than other areas is defined as a dense area (R1), and the other areas are defined as a sparse area (R2), and the diameter of the laser light is defined as the beam diameter. The pattern control unit sets the beam diameter in at least the sparse region to a different size from the beam diameter in the dense region.

[0008] This laser radar device includes a laser beam irradiation unit that irradiates a target area with laser beam and a pattern control unit that controls the irradiation pattern of the laser beam. The pattern control unit sets the beam diameter of the laser beam in at least the sparse areas, which are areas of the irradiation pattern where the density of ranging points is higher than in other areas, to a different size than in the dense areas. As a result, this laser radar device reduces the areas in the sparse areas where the laser beam does not reach, improving the accuracy of detecting objects in the sparse areas of the target area.

[0009] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram illustrating an example of the configuration of a laser radar device according to an embodiment. [Figure 2] FIG. 10 is an explanatory diagram of a laser light irradiation unit when an optical phased array is used. [Figure 3] FIG. 10 is a diagram showing an example of a conventional laser light irradiation pattern. [Figure 4] 4 is an explanatory diagram of object detection using the irradiation pattern of FIG. 3. FIG. [Figure 5] FIG. 3 is a diagram showing an irradiation pattern of laser light according to the first embodiment. [Figure 6] 6 is an explanatory diagram of object detection using the irradiation pattern of FIG. 5. FIG. [Figure 7] FIG. 10 is a diagram showing an irradiation pattern of laser light according to a second embodiment. [Figure 8] FIG. 10 is a diagram showing an irradiation pattern of laser light according to a third embodiment. [Figure 9] FIG. 10 is a diagram showing an irradiation pattern of laser light according to a fourth embodiment. [Figure 10] FIG. 10 is a diagram showing an irradiation pattern of laser light according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

[0012] (Embodiment) A laser radar device 1 according to an embodiment will now be described. The laser radar device 1 is suitable for application to, for example, an object detection device or a collision prevention device mounted on a moving body such as an automobile, but can of course also be used for other purposes.

[0013] [Basic configuration] 1, a laser radar device 1 according to the embodiment includes a light source 2, a laser light emitting unit 3, a detector 4, a phase controller 5, and a pattern control unit 6. The laser radar device 1 is housed in a housing (not shown), for example, and detects an object and measures the distance to the object by emitting laser light as a transmission wave to the outside from an opening in the housing and receiving the reflected light.

[0014] The light source 2 is a device that generates laser light. For example, the light source 2 generates FM modulated continuous wave laser light having a wavelength in the 1.5 μm band or 1.3 μm band, but is not limited to this.

[0015] The laser light irradiation unit 3 uses, for example, an optical phased array (OPA) to perform beam formation and beam steering of the laser light from the light source 2. OPA is an abbreviation for Optical Phased Array. When an OPA is used, for example, the laser light irradiation unit 3 is configured to include a splitter 31, a phase shifter 32, and an antenna array 33.

[0016] The splitter 31 distributes the incident light from the light source 2 to a waveguide array composed of multiple waveguides. The splitter 31 also generates mixed light by mixing the incident light from the waveguide array. This mixed light is incident on the detector 4 together with the incident light from the light source 2.

[0017] The phase shifter 32 is provided for each of the multiple waveguides that make up the waveguide array, and changes the refractive index of the waveguide by utilizing the electro-optic effect, thermo-optic effect, etc. based on instructions from the phase controller 5, thereby individually changing the phase of the light passing through each waveguide.

[0018] The antenna array 33 has a plurality of elements 331 arranged at regular intervals, as shown in FIG. 2, for example. The antenna array 33 has, for example, several hundred to several thousand elements 331. The antenna array 33 irradiates light supplied from the waveguide array toward an FOV, and receives light arriving from the FOV and supplies the light to the waveguide array. FOV is an abbreviation for Field Of View, and is the angular range scanned by the light beam irradiated from the OPA, i.e., the scanning range. The antenna array 33 may be configured to irradiate and receive light via a diffraction grating that diffracts and interferes with light.

[0019] The laser light emitting unit 3 utilizes, for example, optical interference to control the phase of the light supplied from the waveguide array to each element 331, thereby enabling control of the direction in which the light emitted from the entire antenna array 33 is reinforced and the size of the beam diameter. The beam diameter is the diameter of the laser light irradiated at the range-finding point. Note that θ shown in FIG. 2 is the irradiation direction of the light beam from the antenna array 33. Furthermore, the laser light emitting unit 3 is not limited to a configuration in which the antenna array 33 transmits laser light and receives reflected waves, and may be configured such that the part that transmits laser light and the part that receives reflected light are separate entities.

[0020] The detector 4 is configured using a light receiving element such as a photodiode, etc. The detector 4 converts the mixed light generated by the splitter 31 of the laser light irradiation unit 3 into an electric signal, and outputs it to the pattern control unit 6 as a light receiving signal.

[0021] The phase controller 5 outputs the amount of phase adjustment in the phase shifter 32 based on, for example, an output signal from the pattern control unit 6. The phase controller 5 changes the phase of the light supplied from the waveguide array to the element 331 by the phase shifter 32 in accordance with the irradiation direction θ of the light beam from the laser light irradiation unit 3, thereby realizing scanning with the light beam.

[0022] The laser radar device 1 uses one of the multiple elements 331 as a reference, as in the OPA described in JP 2022-57637 A, and achieves scanning of the light beam by adjusting the distance from the reference element 331 to each of the other elements 331 and the phase of the light. The laser radar device 1 may also employ a configuration and control method using, for example, another known OPA.

[0023] The pattern control unit 6 includes, for example, a microcomputer having a CPU and a recording medium such as a ROM or RAM mounted on a circuit board (not shown). CPU, ROM, and RAM are abbreviations for Central Processing Unit, Read Only Memory, and Random Access Memory, respectively. The pattern control unit 6 stores, for example, various programs for executing scanning with the light beam by the laser light irradiation unit 3 and various information such as irradiation patterns according to the situation, recorded on a recording medium (not shown). The pattern control unit 6 is a signal processing unit in which a CPU (not shown) reads and executes various programs and executes various processes such as control signals for scanning the light beam.

[0024] For example, in the case of an in-vehicle application, the pattern control unit 6 is configured to preset sensing requirements such as a ranging range and distance according to the vehicle speed, a resolution according to the ranging range, and an irradiation pattern according to the driving scene, and this information is stored on a recording medium. For example, the pattern control unit 6 acquires various information such as vehicle speed, steering angle, and driver status from various sensors such as a vehicle speed sensor mounted on the vehicle and on-board devices, and determines a preset irradiation pattern according to the driving scene based on the acquired information. As a result, in the case of an in-vehicle application, the laser radar device 1 is configured so that the pattern control unit 6 can execute scanning control of the light beam according to the driving scene of the vehicle.

[0025] The above is the basic configuration of the laser radar device 1. The laser radar device 1 uses the pattern control unit 6 to change the irradiation pattern depending on the situation and executes ROI control to perform necessary sensing in the necessary area, thereby improving detection accuracy without excessively increasing the number of ranging points. ROI is an abbreviation for Region of Interest.

[0026] Note that, although the laser radar device 1 is preferably configured to control the light beam irradiation pattern using an OPA, which offers a high degree of freedom in ROI control, the configuration is not limited to using an OPA. For example, the laser radar device 1 may be configured such that the laser light irradiation unit 3 includes, instead of an OPA, an aperture that controls the beam diameter of the laser light from the light source 2, an irradiation lens, and a lens actuator that supports the irradiation lens and controls the angle of the irradiation lens. In this way, the laser radar device 1 only needs to be able to control the beam diameter and irradiation pattern of the laser light irradiated onto an external target area, and may use an optical control method using an OPA or a mechanical control method that drives lenses, mirrors, etc.

[0027] [Control of irradiation pattern] Next, the control of the irradiation pattern of the laser light irradiated onto the target area by the laser radar device 1 and its effects will be described in comparison with a conventional example. For ease of explanation, the irradiation pattern of the laser light irradiated onto the target area will be simply referred to as the "irradiation pattern." The irradiation pattern may also be referred to as a scan pattern.

[0028] In a conventional irradiation pattern, as shown in Fig. 3, for example, there are multiple laser light irradiation sites within a target region R0. In Fig. 3, the laser light irradiation sites are designated as distance measurement points P, and the distance measurement points P are indicated by black circles. This is also true for Figs. 5 and 7 to 10. For example, the left-right direction in Fig. 3 is the horizontal direction, and the laser light is sequentially irradiated (scanned) from the left end to the right end of the top line along the horizontal direction. Next, the laser light is irradiated from the left end to the right end of the second line from the top in the same manner, for example, and thereafter irradiated to each line in the third, fourth, and fifth lines from the top in the same scanning trajectory.

[0029] In a conventional irradiation pattern, for example, in an area where it is desired to increase the resolution in the horizontal direction, a dense area R1 is formed where the density of ranging points P, i.e., the frequency of laser light irradiation, is higher than in other areas. The dense area R1 corresponds to the ROI. In addition, in the conventional irradiation pattern, in order to prevent an excessive increase in the number of ranging points, a sparse area R2 is formed where the density of ranging points P is lower than in the dense area R1 in areas other than the dense area R1. In addition, in the conventional irradiation pattern, the diameter of the laser light, i.e., the beam diameter, is the same at all ranging points P.

[0030] The above-described conventional irradiation pattern is an example of a case where a vehicle V equipped with a laser radar device mounted in front of the vehicle is traveling straight on a two-lane road, and the center region ahead of the vehicle is set as the ROI, as shown in FIG. 4. In the conventional irradiation pattern, the dense region R1 has a relatively large number of ranging points P, and therefore the intensity of the reflected wave when an object is present is high, resulting in high accuracy of ranging and detection. On the other hand, the sparse region R2 has a small number of ranging points P, resulting in areas within the target region where the laser light is not irradiated, i.e., gaps. Therefore, with the conventional irradiation pattern, even if a target T exists in the gaps in the sparse region R2, it may not be possible to detect the target T, or the detection accuracy may be reduced. For example, the conventional irradiation pattern may not be able to handle a sudden cut-in by a small object or a nearby vehicle in the sparse region R2.

[0031] 4 does not show a cross section, but the area irradiated with laser light from the laser radar device is indicated by hatching, and the outline of the sparse area R2 is indicated by a dashed line. This is also true for FIG. 6, which will be described later.

[0032] In contrast, in the laser radar device 1, in an irradiation pattern subjected to ROI control, the beam diameters of at least some of the multiple ranging points P in the sparse region R2 are made larger than the beam diameters of the ranging points P in the dense region R1, as shown in Fig. 5, for example. Although Fig. 5 does not show a cross section, the portions of the ranging points P in the sparse region R2 whose beam diameters are larger than those in the dense region R1 are indicated by diagonal hatching. This is also true for Figs. 7 to 10. In other words, the areas irradiated with the laser light shown in Figs. 5 and 7 to 10 are the areas indicated by black circles and hatching.

[0033] 5, for example, the beam diameter of the ranging points P in one row adjacent to the dense region R1 among the ranging points P in the sparse region R2 is the same as that in the dense region R1, while the beam diameter of the ranging points P in the remaining sparse region R2 is made larger than that in the dense region R1. The ranging points P in the sparse region R2 are controlled to have different beam diameters for each row, for example, and the beam diameter of the row farther from the dense region R1 becomes larger.

[0034] 5, the beam diameter of the laser light is adjusted by aligning the phase of the light emitted from the multiple elements 331 in the dense region R1 and partially shifting and blurring the light in the sparse region R2. For example, the irradiation pattern in the first embodiment has a beam diameter of φ1 mm and a horizontal resolution of 0.05 deg in the dense region R1, and a beam diameter of φ1 to 10 mm and a horizontal resolution of 0.05 to 0.5 deg in the sparse region R2.

[0035] 5, for ease of understanding whether the phases in the elements 331 are aligned, horizontal lines are used to conveniently indicate the phase positions of the light beams emitted from each of the elements 331. In FIG. 5, when the phases of the light beams emitted from each of the elements 331 are aligned, the horizontal lines are shown aligned in the vertical direction of FIG. 5, and when they are not aligned, the horizontal lines are shown shifted in position.

[0036] In the irradiation pattern of the first embodiment, the beam diameter in part of the sparse region R2 is made larger than that in the dense region R1, thereby reducing the gap area in the sparse region R2 where the laser light is not irradiated, as shown in Fig. 6. This makes it easier for the laser radar device 1 to receive the reflected wave from the target T even when a small object or a nearby vehicle suddenly cuts in on the sparse region R2 of the irradiation pattern, improving the accuracy of ranging and detection.

[0037] In the first embodiment, the irradiation pattern is such that the beam shape of the laser light is substantially circular in all frames during ROI, and the beam diameter of at least some of the ranging points P in the sparse region R2 is larger than that in the dense region R1. However, this is not limited to this. For example, the irradiation pattern may be such that the beam shape of at least some of the ranging points P in the sparse region R2 is elliptical, as in the second embodiment shown in FIG. 7. Furthermore, in the irradiation pattern of the second embodiment, for example, the beam diameter of the ranging points P in the sparse region R2 that is larger than that in the dense region R1 is substantially the same. "Substantially the same" includes not only cases where the beam diameters are completely the same, but also cases where the beam diameters are not completely the same due to some error factor, but are almost the same. The irradiation pattern of the second embodiment also achieves the effect of improving the accuracy of ranging and detection in the sparse region R2, as in the first embodiment.

[0038] The irradiation pattern of the second embodiment is a symmetrical scan pattern, similar to the irradiation pattern of the first embodiment, in which the ROI, i.e., the dense region R1, is a predetermined region in the center of the target region R0, and the remaining regions located on both sides of it are sparse regions R1. In Fig. 7, for ease of viewing, the sparse region R2 on the right side of the irradiation pattern is omitted. This also applies to Figs. 8 to 10.

[0039] Furthermore, the irradiation pattern may be such that the beam diameter of at least some of the ranging points P in the sparse region R2 is larger than that in the dense region R1 in some frames among the multiple frames during ROI, as in the third embodiment shown in Fig. 8. For example, in the irradiation pattern of the third embodiment, the beam diameter in the sparse region R2 is larger than that in the dense region R1 in the first frame, and the beam diameter in the target region is the same in the second frame.

[0040] For ease of explanation, a frame in which the beam diameter of at least some of the measurement points P in the sparse region R2 is made relatively larger than that in the dense region R1 will be referred to as an "adjustment frame," and a frame in which the beam diameter of all measurement points P is the same will be referred to as a "normal frame."

[0041] That is, the irradiation pattern of the third embodiment is a scan pattern in which, for example, adjustment frames and normal frames are alternately repeated during ROI. As a result, the irradiation pattern of the third embodiment has a higher intensity of the laser light emitted in the sparse region R2 than the above embodiments, and as a result, the intensity of the reflected light is improved, which has the effect of improving the accuracy of distance measurement and detection.

[0042] Furthermore, as shown in FIG. 9, the irradiation pattern may be such that some of the frames in the ROI are adjustment frames, and the plurality of adjustment frames have different patterns for increasing the beam diameter in the sparse region R2. For example, the irradiation pattern of the fourth embodiment has the first and third frames as adjustment frames, the second and fourth frames as normal frames, and the first to fourth frames are repeated in this order, resulting in a scan pattern. For example, the irradiation pattern of the fourth embodiment has different patterns of ranging points P for increasing the beam diameter in the adjustment frames in the first and third frames. In addition to the same effects as the third embodiment, the irradiation pattern of the fourth embodiment also has the effect of enabling the intensity of the laser light emitted within the sparse region R2, and therefore the intensity of the reflected light, to be appropriately adjusted according to the detection scene.

[0043] Furthermore, the irradiation pattern may be, for example, as shown in the fifth embodiment in FIG. 10, in which multiple frames during ROI are all adjustment frames, and the pattern of the portion of the adjustment frame where the beam diameter is increased may differ for each frame. For example, in the irradiation pattern of the fifth embodiment, frames 1 to 4 are repeated in this order during ROI, and the pattern of the portion where the beam diameter is increased is different for the first, third, second, and fourth frames. Furthermore, the second and fourth frames have multiple ranging points P in the sparse region R2 where the beam diameter is increased to a different degree than in the dense region R1. In this way, the irradiation pattern of the fifth embodiment achieves the same effect as the fourth embodiment, while the distribution of the laser light irradiation intensity in the sparse region R2 is more finely adjusted.

[0044] In the irradiation patterns of the above-described embodiments, for example, the horizontal spacing between the ranging points P in the dense region R1 and the sparse region R2 is constant. However, this is not limited to this, and the spacing between the ranging points P can be changed as appropriate. Furthermore, in the irradiation patterns of the above-described embodiments, the ROI is set in a predetermined region in the center of the target region R0. However, this is not limited to this, and the position and range of the ROI can be changed as appropriate as long as the beam diameter of at least a portion of the sparse region R2 is relatively large. Furthermore, in the irradiation patterns of the above-described embodiments, the size of the beam diameter in the sparse region R2 may be changed as appropriate for each ranging point P. Furthermore, in the third and fourth embodiments, examples have been shown in which the ratio of adjustment frames to normal frames in the irradiation pattern is 1:1. However, this ratio can also be changed as appropriate.

[0045] According to this embodiment, the laser radar device 1 includes a laser beam irradiation unit 3 that irradiates a target region R0 with laser beam and a pattern control unit 6 that controls the irradiation pattern of the laser beam, and the beam diameter in at least a part of the sparse region R2 of the irradiation pattern is larger than that in the dense region R1. Therefore, in the laser radar device 1, gap regions where the laser beam is not irradiated are reduced in the sparse region R2, and the detection accuracy of objects in the sparse region R2 of the target region R0 is improved.

[0046] (Other embodiments) Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one, or less than one, are also within the scope and spirit of the present disclosure.

[0047] The pattern control unit 6 and methods described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the pattern control unit 6 and methods described herein may be implemented by a special-purpose computer configured with a processor configured with one or more dedicated hardware logic circuits. Alternatively, the pattern control unit 6 and methods described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium.

[0048] It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when numerical values ​​such as the number, values, amounts, and ranges of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]

[0049] 3 Laser light irradiation unit 6 Pattern control section P AF point R0 target area R1 Dense region (in the laser beam irradiation pattern) R2 (laser light irradiation pattern) sparse region

Claims

1. A laser radar device that irradiates a target area (R0) with laser light and detects an object present in the target area, a laser light irradiation unit (3) that irradiates the laser light onto the target area; a pattern control unit (6) that controls the irradiation pattern of the laser light irradiated onto the target area, Each irradiation site of the laser light in the irradiation pattern is defined as a distance measurement point (P), a region in the irradiation pattern where the density of the distance measurement points is higher than other regions is defined as a dense region (R1), and other regions are defined as sparse regions (R2), and the diameter of the laser light is defined as a beam diameter, The pattern control unit sets the beam diameter in at least the sparse region to a size different from the beam diameter in the dense region.

2. The laser radar device according to claim 1 , wherein the pattern control unit is capable of changing an interval between adjacent distance measurement points in the irradiation pattern.

3. The laser radar device according to claim 1 , wherein the pattern control unit sets the beam diameter at some of the distance measurement points in the irradiation pattern to a size different from the beam diameter at other of the distance measurement points.

4. The laser radar device according to claim 3 , wherein the pattern control unit sets the size of the beam diameter for each of the distance measurement points within one frame of the irradiation pattern.

5. The laser radar device according to claim 3 , wherein the pattern control unit sets the size of the beam diameter for each of a plurality of frames that form the irradiation pattern.

6. 6. The laser radar device according to claim 1, wherein the pattern control unit acquires information about the host vehicle and a driver of the host vehicle from an on-board device of the host vehicle on which the laser radar device is mounted, and sets the irradiation pattern based on the information.

7. The laser radar device according to claim 6 , wherein the laser light emitting unit has an optical phased array.

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