FIELD OF THE DISCLOSURE
The present disclosure relates to systems and methods for providing a dynamic region of interest in a LIDAR system.
BACKGROUND
Certain lidar systems include a laser that can be discretely scanned over a series of points in a target region and a detector that can detect a reflected portion of the discretely scanned laser, such as to provide an image of the target region. An angular resolution of the lidar system can depend on the number of points that can be scanned by the laser within a field of view of the lidar system.
SUMMARY OF THE DISCLOSURE
In certain lidar systems with a large field of view and a very fine angular resolution, thermal management of the lidar system and receive-side analog-to-digital conversion circuitry can present design challenges. In an example, a large field of view can include a ±30° horizontal field of view and a ±0.6° vertical field of view, a very fine angular resolution can include a 0.1° horizontal angular resolution and a 0.2° vertical angular resolution, and the lidar system can include a 20 Hz frame update rate. In such an example, the lidar system can scan 540,000 points per second, and can correspond to an average laser power of 720 mW for a laser outputting 1 μJ per pulse. An average laser power of 720 mW can be high enough to cause considerable thermal design challenges. In an example where multiple laser pulses can be used for each point in a 2D field of view, the average laser power can be much higher. For example, if five pulses per point in the 2D field of view are used, the average laser power can be 3.6 W. The inventors have recognized, among other things, that it is possible to reduce a number of points scanned per lidar image, such as by providing varying spatial resolution in the lidar images, such as to overcome difficulties with thermal management and receive-side electronics. Further features of the disclosure are provided in the appended claims, which features may optionally be combined with each other in any permutation or combination, unless expressly indicated otherwise elsewhere in this document.
In an aspect, the disclosure can feature a method for providing a dynamic region of interest, such as in a lidar system. The method can include scanning a light beam over a field of view, such as to capture a first lidar image. The method can also include identifying a first object, such as within the captured first lidar image. The method can also include selecting a first region of interest, such as within a field of view that contains at least a portion of the identified first object. The method can also include capturing a second lidar image, where capturing the second lidar image can include scanning the light beam over the first region of interest, such as at a first spatial sampling resolution and scanning the light beam over the field of view outside of the first region of interest, such as at a second spatial sampling resolution, wherein the second sampling resolution can be different than the first spatial sampling resolution. In an example, the second sampling resolution can be less than the first spatial sampling resolution. The method can also include identifying a second object, such as can be outside of the first region of interest, selecting a second region of interest that can contain at least a portion of the identified second object, and capturing a third lidar image, where capturing the third lidar image can include scanning the light beam over the first region of interest and the second region of interest at the first spatial sampling resolution and scanning the light beam over the field of view outside of both the first region of interest and the second region of interest at a third spatial sampling resolution, where the third sampling resolution can be different than the second spatial sampling resolution. In an example, the third sampling resolution can be less than the second spatial sampling resolution. In an example, the second object can be identified outside of the first region of interest using the captured second lidar image. The method can also include detecting a movement of the identified first object, and adjusting a characteristic of the first region of interest, such as in response to the detected movement of the identified first object. The method can also include adjusting a size of the first region of interest, such as in response to the detected movement of the identified first object. The method can also include adjusting a size and position of the first region of interest in response to the detected movement of the identified first object. The method can also include detecting a change in the size of the identified first object and adjusting a size of the first region of interest, such as to accommodate the detected change in size of the identified first object. The method can also include reducing a second spatial sampling resolution, such as in response to an increase in the size of the first region of interest. The method can also include increasing a second spatial sampling resolution, such as in response to a decrease in the size of the first region of interest. The method can also include scanning the light beam over the field of view to capture successive lidar images, wherein the region of interest is capable of being adjusted after the capture of each successive lidar image. The method can also include identifying a second object outside of the first region of interest, selecting a second region of interest that can contain at least a portion of the identified second object, and capturing a third lidar image, where capturing the third lidar image can include scanning the light beam over the first region of interest at the first spatial sampling resolution, scanning the light beam over the second region of interest at a third spatial sampling resolution, and scanning the light beam over the field of view outside of the first region of interest and the second region of interest, at the second spatial sampling resolution, wherein the third sampling resolution can be different than the first spatial sampling resolution. In an example, the third sampling resolution can be less than the second spatial sampling resolution. In an example, the second object can be identified outside of the first region of interest by using the captured second lidar image. Identifying a first object within the captured first lidar image can include detecting at least one edge of the first object. Identifying a first object within the captured first lidar image can include detecting at least one lane marker.
In an aspect, the disclosure can feature a system for providing a dynamic region of interest in a lidar system. The system can include a laser configured to emit a light beam, such as towards a target region. The system can also include control circuitry configured to instruct an optical system to scan the light beam over the target region. The system can also include an optical system having a field of view and can configured to direct a portion of the light beam received from the target region. The system can also include a photodetector configured to receive the portion of the light beam directed from the optical system, such as to form a first lidar image. The system can also include detection circuitry that can be configured to identify a first object within the first lidar image. The control circuitry can be further configured to select a first region of interest within the field of view that can contain at least a portion of the identified first object, instruct the optical system to scan the light beam over the first region of interest at a first spatial sampling resolution, and instruct the optical system to scan the light beam over the field of view outside of the first region of interest at a second spatial sampling resolution that can be different than the first spatial sampling resolution. In an example, the first spatial sampling resolution can be less than the second spatial sampling resolution. The photodetector can be further configured to receive a corresponding portion of the light beam to form a second lidar image. The detection circuitry can be further configured to identify a second object outside of the first region of interest in the second lidar image. The control circuitry can be further configured to select a second region of interest that can contain a portion of the identified second object, instruct the optical system to scan the light beam over the first region of interest and the second region of interest at the first spatial sampling resolution, and instruct the optical system to scan the light beam over the field of view outside of both the first region of interest and the second region of interest at a third spatial sampling resolution that can be different than the first spatial sampling resolution. In an example, the third spatial sampling resolution can be less than the first spatial sampling resolution. The detection circuitry can be further configured to detect a movement of the identified first object and the control circuitry can be configured to adjust a characteristic of the first region of interest, such as in response to the detected movement of the identified first object. The control circuitry can be further configured to adjust a size of the first region of interest, such as in response to the detected movement of the identified first object. The control circuitry can be further configured to adjust a size and position of the first region of interest, such as in response to the detected movement of the identified first object. The detection circuitry can be further configured to detect a change in the size of the identified first object and the control circuitry can be further configured to adjust a size of the first region of interest, such as to accommodate the detected change in size of the identified first object. The control circuitry can be further configured to reduce the second spatial sampling resolution, such as in response to an increase in the size of the first region of interest. The control circuitry can be further configured to increase the second spatial sampling resolution, such as in response to a decrease in the size of the first region of interest.
In an aspect, the disclosure can feature a system for providing a dynamic region of interest in a lidar system. The system can include a means for scanning a light beam over a field of view, such as to capture a first lidar image. The means for scanning can include control circuitry and a scanning laser, such as control circuitry 104 and scanning laser 106 as shown in FIG. 1A. The system can also include a means for identifying a first object within the captured first lidar image. The means for identifying can include detection circuitry, such as detection circuitry 124 as shown in FIG. 1A. The system can also include a means for selecting a first region of interest within the field of view that contains at least a portion of the identified first object. The means for selecting can include control circuitry, such as control circuitry 104 as shown in FIG. 1A. The system can also include a means for capturing a second lidar image, where capturing the second lidar image can includes scanning the light beam over the first region of interest at a first spatial sampling resolution and scanning the light beam over the field of view outside of the first region of interest at a second spatial sampling resolution, wherein the second sampling resolution can be different than the first spatial sampling resolution. In an example, the second sampling resolution can be less than the first spatial sampling resolution. The means for capturing a second lidar image can include control circuitry and a scanning laser, such as control circuitry 104 and scanning laser 106 as shown in FIG. 1A.
BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1A illustrates a diagram of a lidar system.
FIGS. 1B-1D illustrate examples of a frame in a lidar system.
FIGS. 2A-2C illustrate an example of a sequence of frames in a lidar system.
FIGS. 3A-3B illustrate an example of a sequence of frames in a lidar system.
FIG. 4 illustrates a method of operation of a lidar system.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE
FIG. 1A shows an example of a lidar system 100. The lidar system 100 can include control circuitry 104, a scanning laser 108, an optical system 116, a photosensitive detector 120, and detection circuitry 124. The control circuitry 104 can be connected to the scanning laser 108 and the detection circuitry 124. The photosensitive detector 120 can be connected to the detection circuitry 124. During operation, the control circuitry 104 can provide instructions to the scanning laser 108, such as to cause the scanning laser to scan a light beam over a target region 112. In an example, the scanning laser 108 can include laser that can emit a light beam and an optical system, such as an electro-optic waveguide. The electro-optic waveguide can adjust an angle of the light beam based on the received instructions from the control circuitry 104. The target region 112 can correspond to a field of view of the optical system 116. The scanning laser 108 can scan a light beam over the target region 112 in a series of scanned points 114. The optical system 116 can receive at least a portion of the light beam from the target region 112 and can image the scanned points 114 onto the photosensitive detector 120 (e.g., a CCD). The detection circuitry 124 can receive and process the image of the scanned points from the photosensitive detector 120, such as to form a frame. In an example, the control circuitry 104 can select a region of interest that is a subset of the field of view of the optical system and instruct the scanning laser to scan over the region of interest. In an example, the detection circuitry 124 can include circuitry for digitizing the received image. In an example, the lidar system 100 can be installed in an automobile, such as to facilitate an autonomous self-driving automobile.
FIG. 1B illustrates an example of a frame 130 corresponding to a 2D image, such as that captured with lidar system 100. The frame 130 can include a collection of scanned points 114. The scanned points 114 can be regularly spaced by a distance d, along a grid. The spacing d of the scanned points 114 can determine the angular resolution of a lidar system, such as the lidar system 100. For example, a larger spacing can correspond to a coarser angular resolution and a smaller spacing can correspond to a finer angular resolution. In an example, the frame 130 can include a region of interest 135 that corresponds to a field of view of the optical system 116 (e.g., all points within the field of view can be scanned).
FIG. 1C illustrates an example of a frame 130, such as that captured with lidar system 100. The frame 130 can include a collection of scanned points 114. The scanned points 114 can be regularly spaced along a grid. The spacing of the scanned points 114 can determine the angular resolution of a lidar system, such as the lidar system 100. For example, a larger spacing can correspond to a coarser angular resolution and a smaller spacing can correspond to a finer angular resolution. In an example, the frame 130 can include a region of interest 135 that corresponds to a subset of a field of view of the optical system 116. In an example, the scanning laser 108 scan a light beam over the region of interest 135, but not other points within the field of view of the lidar system 100 (e.g., only a fraction of points within the field of view can be scanned).
FIG. 1D illustrates an example of a frame 130, such as that captured with lidar system 100. The frame 130 can include a collection of scanned points 114. The scanned points 114 can be regularly spaced along a grid. The spacing of the scanned points 114 can determine the angular resolution of a lidar system, such as the lidar system 100. For example, a larger spacing can correspond to a coarser angular resolution and a smaller spacing can correspond to a finer angular resolution. In an example, the frame 130 can include a region of interest 135 that corresponds to a subset of a field of view of the optical system 116. In an example, the scanning laser 108 scan a light beam over the region of interest 135, but not other points within the field of view of the lidar system 100 (e.g., only a fraction of points within the field of view can be scanned).
FIGS. 2A-2C illustrate an example of a sequence of frames 230-232 where the scanned points can be irregularly spaced across a field of view of the optical system 116. The first frame 230 as illustrated in FIG. 2A can include a first region of interest 235. The first region of interest 235 can include a collection of regularly spaced scanned points. The scanned points in the first region of interest 235 can correspond to a first angular resolution. Outside of the first region of interest 235, the scanned points can be regularly spaced with a larger spacing than the first region of interest 235, corresponding to a coarser angular resolution than in the first region of interest 235. Outside of the first region of interest 235, every third column in every other row can be scanned as illustrated in FIG. 2A. However, other patterns of scanning can be utilized outside of the first region of interest 235. For example, a scanning pattern outside of the first region of interest can include every second column, in every third row. More generally, the scanning pattern outside of the first region of interest 235 can include every nth column in every mth row. The first region of interest 235 can be dynamically adjusted on a frame-to-frame basis, such as based on an analysis of the frame by the detection circuitry 124. In the example shown in FIG. 2A, the first frame can accommodate up to 144 scanned points, the first region of interest 235 can include 36 scanned points, and the portion of the frame outside of the region of interest can include 17 scanned points, for a total of 53 scanned points out of a total of 144 possible scanned points. The second frame 231 as illustrated in FIG. 2B can include a second region of interest 236. The second region of interest 236 can be determined based on an object detected in the first frame 230. The second region of interest 236 can be smaller than the first region of interest 235 and can include a collection of regularly spaced scanned points. The scanned points in the second region of interest 236 can correspond to a first angular resolution. Outside of the second region of interest 236, the scanned points can be regularly spaced with a larger spacing than the second region of interest 236, corresponding to a coarser angular resolution than in the second region of interest 236. The second region of interest 236 can be dynamically adjusted on a frame-to-frame basis, such as based on an analysis of the first frame 230 by the detection circuitry 124. In an example where the second region of interest 236 can be smaller than a first region of interest 235, a total number of scanned points in the frame 231 can be smaller than the total number of scanned points in the frame 230. In the example shown in FIG. 2B, the second frame can accommodate up to 144 scanned points, the second region of interest 236 can include 12 scanned points, and the portion of the frame outside of the region of interest can include 23 scanned points, for a total of 45 scanned points out of a total of 144 possible scanned points. The third frame 232 as illustrated in FIG. 2C can include a third region of interest 237 and a region of disinterest 240. The third region of interest 237 can be determined based on an object detected in the second frame 231. The third region of interest 237 can be the same size as the second region of interest 236 and can include a collection of regularly spaced scanned points. The scanned points in the third region of interest 237 can correspond to a first angular resolution. Outside of the third region of interest 237, the scanned points can be regularly spaced with a larger spacing than the third region of interest 237, corresponding to a coarser angular resolution than in the third region of interest 237. The third region of interest 237 can be dynamically adjusted on a frame-to-frame basis, such as based on an analysis of the second frame 231 by the detection circuitry 124. In the region of disinterest 240, the scanned points can be regularly spaced with a larger spacing than outside of the third region of interest 237. In an example, no points are scanned in the region of disinterest 240. In an example, the region of disinterest can correspond to an area in the frame that includes a quasi-stationary object. The size and location of the region of disinterest 240 can be determined based on the identification of one or more objects within the second frame 231. Similar to the regions of interest 235-237, the region of disinterest 240 can be dynamically adjusted on a frame-to-frame basis. In an example where the third region of interest 236 can be the same size as the second region of interest 235, a total number of scanned points in the third frame 232 can be smaller than the number of scanned points in the second frame 231. In the example shown in FIG. 2C, the third frame can accommodate up to 144 scanned points, the third region of interest 237 can include 12 scanned points, the region of disinterest 240 can exclude up to 20 scanned points, and the portion of the frame outside of the region of interest can include 18 scanned points, for a total of 30 scanned points out of a total of 144 possible scanned points.
FIGS. 3A-3B illustrate a sequence of frames 330-331, such as can be collected by a lidar system in an automobile where the scanned points can be irregularly spaced across a field of view that can include a road and associated landscape. The first frame 330 as illustrated in FIG. 3A can include a first region of interest 335, a second region of interest 345, and a region of disinterest 340. The first region of interest 335 can include a collection of regularly spaced scanned points. The scanned points in the first region of interest 335 can correspond to a first angular resolution. The first region of interest 335 can correspond to a portion of a road having at least one lane, where each lane can be approximately 4 meters wide. A width of the first region of interest 335 can be selected, such as to accommodate the width of three lanes (e.g., a lane that an automobile is driving in and additionally, one lane on either side of the lane that the automobile is driving in). The width of the first region of interest 335 can be sized to accommodate a radius of curvature of the road. For example, at a relatively high speed of 150 km/hr, a radius of curvature of the road can be approximately 1 km, corresponding to a road that can be 4° off of a longitudinal axis at a distance of 150 m. At a medium speed of 80 km/hr, a radius of curvature of the road can be approximately 200 m, corresponding to a road that can be 10° off of a longitudinal axis at a distance of 60 m. To account for the radius of curvature of the road, the first region of interest 335 can extend 20° in a horizontal direction, and to account for a vertical extent of other automobiles (e.g. an automobile can extend 4 m and the region of interest can be sized to accommodate twice the vehicle height at a distance of 60 m), the first region of interest can extend 4° in a vertical direction. The second region of interest 345 can be smaller than the first region of interest 335 and can include a collection of regularly spaced scanned points. The scanned points in the second region of interest 345 can correspond to the first angular resolution. The second region of interest 345 can correspond to a portion of a lane marker on a road. Outside of the first region of interest 335 and the second region of interest 345, the scanned points can be regularly spaced with a larger spacing than the first region of interest 335 and the second region of interest 345, corresponding to a coarser angular resolution than in the first region of interest 335 or the second region of interest 345. Outside of the first region of interest 335 and the second region of interest 345, every mth column in every nth row can be scanned with the exception of the region of disinterest 340. The region of disinterest 340 can designate an area within the frame 330 where the scanned points can be regularly spaced with a larger spacing than in the first region of interest 335, the second region of interest 345, or the region outside of the first region of interest 335 and the second region of interest 345. In an example, no points are scanned within the region of disinterest 340. The region of disinterest 340 can include fixed road infrastructure, such as guard rails and the road shoulder. The region of disinterest can include a road surface near an automobile. The region of disinterest 340 can correspond to objects such as trees, rocks, or mountains within a field of view of a lidar system, such as lidar system 100. The first region of interest 335, the second region of interest 345, and the region of disinterest 340 can be adjusted dynamically, such as based on the motion of objects within the field of view of the lidar system 100. FIG. 3B illustrates a second frame 331 where the regions of interest and disinterest have been dynamically updated, such as based on a change in the relative position of the road and lane markers within the field of view of the lidar system 100. The second frame 331 as illustrated in FIG. 3b can include a first region of interest 336, a second region of interest 346, and a region of disinterest 341. The first region of interest 336 can include a collection of regularly spaced scanned points. The scanned points in the first region of interest 335 can correspond to a first angular resolution. The first region of interest 335 can correspond to a portion of a road having at least one lane, where each lane can be approximately 4 meters wide. A width of the first region of interest 335 can be selected, such as to accommodate the width of three lanes (e.g., a lane that an automobile is driving in and additionally, one lane on either side of the lane that the automobile is driving in). The width of the first region of interest 335 can be sized to accommodate a radius of curvature of the road. For example, at a relatively high speed of 150 km/hr, a radius of curvature of the road can be approximately 1 km, corresponding to a road that can be 40 off of a longitudinal axis at a distance of 150 m. At a medium speed of 80 km/hr, a radius of curvature of the road can be approximately 200 m, corresponding to a road that can be 10° off of a longitudinal axis at a distance of 60 m. To account for the radius of curvature of the road, the first region of interest 335 can extend 20° in a horizontal direction, and to account for a vertical extent of other automobiles (e.g. an automobile can extend 4 m and the region of interest can be sized to accommodate twice the vehicle height at a distance of 60 m), the first region of interest can extend 4° in a vertical direction. The second region of interest 346 can be smaller than the first region of interest 336 and can include a collection of regularly spaced scanned points. The scanned points in the second region of interest 346 can correspond to the first angular resolution. The second region of interest 346 can correspond to a portion of a lane marker on a road. Outside of the first region of interest 336 and the second region of interest 346, the scanned points can be regularly spaced with a larger spacing than the first region of interest 336 and the second region of interest 346, corresponding to a coarser angular resolution than in the first region of interest 336 or the second region of interest 346. Outside of the first region of interest 336 and the second region of interest 346, every mth column in every nth row can be scanned with the exception of the region of disinterest 341. The region of disinterest 341 can designate an area within the frame 331 where the scanned points can be regularly spaced with a larger spacing than in the first region of interest 336, the second region of interest 346, or the region outside of the first region of interest 336 and the second region of interest 346. In an example, no points are scanned within the region of disinterest 341. The region of disinterest 341 can correspond to objects such as trees, rocks, or mountains within a field of view of a lidar system, such as lidar system 100.
FIG. 4 illustrates a method of adjusting a field of view in a lidar system, such as lidar system 100. A light beam, such as can be emitted by the scanning laser 108 can be scanned over a target region within a field of view of an optical system, such as optical system 116 and a first image can be captured by a photosensitive detector, such as the photosensitive detector 120 (step 410). A first object can be identified within the first image by detection circuitry, such as the detection circuitry 124 (step 420). Control circuitry, such as control circuitry 104 can select a first region of interest that includes at least a portion of the identified first object (step 430). A second lidar image can then be captured (step 440). The capturing of the second lidar image can include steps 450 and 460 described below. A light beam, such as can be emitted by the scanning laser 108 can be scanned over the first region of interest at a first spatial sampling resolution (step 450). A light beam, such as can be emitted by the scanning laser 108 can be scanned over the field of view outside of the first region of interest at a second spatial sampling resolution, wherein the second sampling resolution can be less than the first spatial sampling resolution (step 460). In an example, detection circuitry, such as the detection circuitry 124 can identify a second object outside of the first region of interest in the captured second lidar image. Control circuitry, such as control circuitry 104 can select a second region of interest that can contain at least a portion of the identified second object. A third lidar image can then be captured, where capturing the third lidar image can include scanning a light beam, such as that emitted by the scanning laser 108, over both the first and second regions of interest at the first spatial sampling resolution and over a field of view outside of both the first and second regions of interest at a third spatial sampling resolution that can be less than the second spatial sampling resolution. In an example, the control circuitry 104 can receive external data, such as from an inertial sensor, GPS, radar, camera, or wheel speed sensor data, and in response to the received external data, the control circuitry 104 can adjust a size or position of the first region of interest.
Patent Application
20180306905
