WO2021163732A1

WO2021163732A1 - Lidar sensor assembly with blockage detection

Info

Publication number: WO2021163732A1
Application number: PCT/US2021/070153
Authority: WO
Inventors: Nehemia Terefe; Guido FUCHS
Original assignee: Continental Automotive Systems, Inc.
Priority date: 2020-02-12
Filing date: 2021-02-12
Publication date: 2021-08-19

Abstract

A lidar sensor assembly (100) includes a light source (102) for generating light and transmission optics (104) for delivering the light to a field of illumination (106). Receiving optics (108) receive light reflected off an object (110) in a field of view generally corresponding to the field of illumination. A generally transparent cover (112) is disposed between the receiving optics and the field of view and an array of photodetectors (114) is positioned to receiving the light from the receiving optics. At least one photodiode (118) is positioned separate from the array of photodetectors to receive light potentially scattered by a blockage on the cover and is configured to generate a signal in response to the received light.

Description

LIDAR SENSOR ASSEMBLY WITH BLOCKAGE DETECTION

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of provisional patent applications Nos. 62/975,730 and 62/975,735, each filed February 12, 2020, and each of which is hereby incorporated by reference.

TECHNICAL FIELD

[0002] The technical field relates generally to lidar sensors and more specifically to systems and methods for detecting blockages on a cover of a lidar sensor.

BACKGROUND

[0003] Scene and object detection is utilized with semi- and fully-autonomous vehicles. Such scene detection is achieved, particularly at night, with the use of lidar detector assemblies, including high-resolution flash lidar detector assemblies. These assemblies generate light which may reflect off an object in a field of view and be detected by one or more photodetectors. Such assemblies typically include a cover to protect the various components while still allowing light to pass therethrough. However, water, dirt, and/or other substances may accumulate on the cover and cause a partial blockage of the cover, thus reducing overall effectiveness of the lidar detection assembly.

[0004] As such, it is desirable to present a system and/or method for detecting blockages a lidar detection assembly. In addition, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

BRIEF SUMMARY

[0005] In one exemplary embodiment, a lidar sensor assembly includes a light source for generating light. The assembly also includes transmission optics for delivering the light generated by the light source to a field of illumination. The assembly further includes receiving optics for receiving light reflected off an object in a field of view generally corresponding to the field of illumination. A generally transparent cover is disposed between the receiving optics and the field of view. The assembly also includes an array of photodetectors for receiving the light from the receiving optics. The assembly further includes at least one photodiode positioned separate from the array of photodetectors to receive light potentially scattered by a blockage on the cover and configured to generate a signal in response to the received light.

[0006] In one exemplary embodiment, a method of detecting a blockage in a lidar sensor assembly is set forth. The assembly includes a light source for generating light, transmission optics for delivering the light generated by the light source to a field of illumination, receiving optics for receiving light reflected off an object in a field of view generally corresponding to the field of illumination, a generally transparent cover disposed between the receiving optics and the field of view, an array of photodetectors for receiving the light from the receiving optics, and a processor in communication with the at least one photodiode. The method includes disposing at least one photodiode separate from the array of photodetectors for receiving light scattered by a blockage on the cover. The method further includes sensing, with the processor, an electrical signal generated by the at least one photodiode indicative of light scattered by a blockage on the cover.

BRIEF DESCRIPTION OF THE DRAWINGS [0007] Other advantages of the disclosed subject matter will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0008] Figure 1 is a block diagram of a lidar sensor assembly according to one exemplary embodiment;

[0009] Figure 2 is a front view of an array of photodetectors and separate photodiodes of the lidar sensor assembly according to one exemplary embodiment;

[0010] Figure 3 is a side view of a cover, a receiving optic, the array of photodetectors, and the separate photodiodes with no blockage on the cover according to one exemplary embodiment; and [0011] Figure 4 is a side view of the cover, the receiving optic, the array of photodetectors, and the separate photodiodes with a blockage on the cover according to one exemplary embodiment.

DETAILED DESCRIPTION

[0012] Referring to the Figures, wherein like numerals indicate like parts throughout the several views, a lidar sensor assembly 100 is shown and described herein.

[0013] Referring to Figure 1, the lidar sensor assembly 100 includes a light source 102 for generating light. The light source 102 may be a laser, laser diode, and/or other suitable device for generating light. In the exemplary embodiment, the light source 102 is a laser (not separately numbered) generating infrared light. Of course, multiple light sources 102 may be utilized.

[0014] The lidar sensor assembly 100 also includes transmission optics 104 for delivering the light generated by the light source 102 to a field of illumination 106. In the exemplary embodiment, the transmission optics 104 disperse the focused light from the laser light source 102 over the field of illumination 106.

[0015] It should be appreciated that while the exemplary embodiment may describe a solid-state or “flash” lidar sensor, other types of lidar sensors (e.g., scanning lidar sensors) may utilize the blockage detection concepts described herein.

[0016] The lidar sensor assembly 100 of the exemplary embodiment further include receiving optics 108 for receiving light reflected off an object 110 in a field of view 111 corresponding generally to the field of illumination 106. While a single object 110 is shown in Figure 1, it should be appreciated that numerous objects 110, or no objects 110 at all, may be present in the field of view 111 at any moment.

[0017] The lidar sensor assembly 100 also includes a cover 112 disposed between the receiving optics 108 and the field of view 111. The cover 112 is generally transparent to allow the light to pass therethrough while protecting the receiving optics 108 from potential damage from dirt, moisture, etc. as is appreciated by those of ordinary skill in the art. The cover 112 may be formed from glass, plastic, and/or any other suitable material.

[0018] The lidar sensor assembly 100 of the exemplary embodiment also includes an array 114 of photodetectors 200 for receiving the light from the receiving optics 108. In the exemplary embodiment, as shown in Figure 2, the photodetectors 200 are arranged rectangularly as a two-dimensional array 114. The field of view 111 of the receiving optics 108 is focused onto the array 114 of photodetectors 200, as shown in Figures 3 and 4. Each photodetector 200 generates an electrical signal generally corresponding to the light received at the photodetector 200. In this exemplary embodiment, each photodetector 200 corresponds to a pixel of an image generated by the array 114.

[0019] The lidar sensor assembly 100 further includes an integrated circuit 116, as shown in Figure 1. In an exemplary embodiment, the integrated circuit 116 includes a plurality of unit cells (not shown). Each unit cell is electrically connected to one of the photodetectors of the array 114. The integrated circuit 116, commonly referred to as a read out integrated circuit or ROIC, processes and/or conditions the electrical signals received from the photodetectors of the array 114.

[0020] The lidar sensor assembly 100 further includes a photodiode 118 separate from the array 114 of photodetectors. As perhaps better appreciated from viewing Figures 2-4, the photodiode 118 is positioned for receiving light scattered by a blockage 400 on the cover 112. For example, the blockage 400 could be generated by water (e.g., raindrops) and/or other substances disposed on the cover 112. In the exemplary embodiment, the assembly 100 includes two photodiodes 118 - one disposed above the array 114 at about a center line (not shown), and one disposed below the array 114 at the center line. The photodiode 118 generates an electrical signal corresponding to light being received by the photodiode 118. Of course, the photodiodes 118 may be disposed at other positions separate from the array 114.

[0021] Each photodiode 118 is disposed within the field of view 111 of the receiving optics 108 but outside the area (not numbered) of the array 114 that is generally associated with the field of illumination 106. As such, under conditions where blockages are not present on the cover 112, light will not typically be directed at the photodiodes 118.

[0022] The lidar sensor assembly 100 also includes a processor 120. The processor 120 is a device capable of performing calculations and/or performing a series of instructions (i.e., running a program). For example, the processor 120 may be implemented with one or more of a microprocessor, microcontroller, application specific integrated circuit (“ASIC”), field-programmable gate array (“FPGA”), and/or other suitable device. [0023] The processor 120 is in communication with the photodiode 118 and is configured to receive the signal from the photodiode 118. Of course, as is appreciated by those of ordinary skill in the art, an analog-to-digital converter (“ADC”) or other such device may be utilized to condition the signal generated by the photodiode 118 so that it may be utilized by the processor 120.

[0024] The processor 120 is configured to determine if a blockage exists on the cover 112 based at least in part on the signal from the photodiode 118. More particularly, in one embodiment, the processor 120 is configured to utilize an amplitude of the signal from the photodiode 118 in determining if a blockage exists on the cover 112. The amplitude of the signal generated by the photodiode 118 is proportional to the intensity of the light scattered by the blockage on the cover 112. As such, the amplitude of the signal generated by the photodiode 118 may be utilized to quantify the degree of blockage on the cover 112. [0025] In one embodiment, the processor 120 is also in communication with the light source 102 in addition to being in communication with the photodiode 118. More particularly, the processor 120 may receive a signal and/or data indicating the illumination of the light source 102 and/or the time of illumination of the light source 102. As such, the processor 120 is configured to received and/or calculate a time of flight of the light generated by the light source 102 and received at the at least one photodiode 118.

[0026] By calculating the time of flight, the processor 120 may then determine whether a signal produced by the photodiode 118 is associated with light generated by the light source 102, reflecting off an object, and interacting with a blockage on the cover 112. This allows the processor 120 to discriminate against other spurious signals that may result from other sources of light and are not indicative of a blockage on the cover 112.

[0027] In one embodiment, the processor 120 is also in communication with the array 114 of photodetectors 200 in addition to being in communication with the photodiode 118. In the exemplary embodiment shown in Figure 1, the processor 120 is in communication with the integrated circuit 116 which, in turn, is electrically connected to the array 114. The information received from the integrated circuit 116 may include electrical signals corresponding to the light received at the array 114 of photodetectors.

[0028] In this embodiment, the processor 120 is configured to detect a potential dispersion of light caused by a blockage on the cover based on signals generated by said array of photodetectors. Such a blockage can cause a “halo” around an object in the field of view when viewed on an image generated by the photodetectors, as shown in Figure 5. That is, the light reflecting off the object may be dispersed in a generally circular or oval pattern onto the array 114 of photodetectors 120. This result in what appears to be a halo around the object when a resulting image is viewed.

[0029] The processor 120 may utilize the signals generated by the potential dispersion of light on the array 114 along with the signal generated by the photodiode to determine whether there is a blockage on the cover 112.

[0030] In another embodiment, the processor 120 may utilize (1) the signals generated by the potential dispersion of light on the array 114, (2) the signal generated by the photodiode, and (3) the time of flight of the light generated by the light source 102 to determine whether there is a blockage on the cover 112. It should also be appreciated that the processor may utilize any combination of these signals and/or data to determine whether there is a blockage on the cover 112

[0031] The processor 120 may generate an output signal, alert, and/or other data (hereafter the “output signal”) in response to determining that there is a blockage on the cover 112. The output signal may be used by devices, processors, etc. For instance, in one embodiment, the output signal may trigger a cleaning mechanism (not shown) to clean the cover 112 of the lidar sensor assembly 100.

[0032] In another embodiment, the output signal may be utilized by an autonomous vehicle controller (not shown) in the control of a vehicle (not shown). In one example, the controller may stop using data from the lidar sensor assembly 100. In another example, the controller may change a confidence value of the data provided by the lidar sensor assembly 100. In yet another example, the controller may remove certain image data provided by the lidar sensor assembly 100, e.g., the halo. In yet a further example, the controller may request that a driver assume manual control of the vehicle.

[0033] In yet another embodiment, the output signal may be utilized to provide an alert to an occupant of the vehicle that the lidar sensor assembly 100 may provide unreliable data. Of course, other uses the output signal may be contemplated.

[0034] Another embodiment of the lidar sensor assembly 100 is shown in Figures 5 and 6. In this particular embodiment, a blockage 400 may be detected without light reflecting off an object 110 in the field of illumination 106. Referring particularly to Figure 6, the laser 102 projects a beam of light at a mirror 600 which directs the beam through optics 602. A scanner 604, e.g., a movable mirror, then reflects the beam of light into a field of illumination. Should a blockage 400 occur on the cover 112 of the assembly 100, some light may be reflected back, through the optics 602, to the photodiode 118. The processor 120 may then utilize the signal generated by the photodiode 118 to determine the presence of a blockage. A wavelength filter 606 may be utilized to remove wavelengths of light that does not match that of the laser 102, thus preventing or reducing false positive signals.

[0035] The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims.

Claims

CLAIMS What is claimed is:

1. A lidar sensor assembly comprising: a light source for generating light; transmission optics for delivering the light generated by said light source to a field of illumination; receiving optics for receiving light reflected off an object in a field of view generally corresponding to the field of illumination; a generally transparent cover disposed between the receiving optics and the field of view; an array of photodetectors for receiving the light from the receiving optics; and at least one photodiode positioned separate from said array of photodetectors to receive light potentially scattered by a blockage on said cover and is configured to generate a signal in response to the received light.

2. The lidar sensor assembly as set forth in claim 1 further comprising a processor in communication with said at least one photodiode and configured to receive the signal from the at least one photodiode and determine if a blockage exists on said cover based at least partially on the signal.

3. The lidar sensor assembly as set forth in claim 2, wherein said processor is configured to utilize an amplitude of the signal from the at least one photodiode in determining if a blockage exists on said cover.

4. The lidar sensor assembly as set forth in claim 2 wherein said processor is also in communication with said light source and is configured to calculate a time of flight of the light generated by said light source and received at said at least one photodiode.

5. The lidar sensor assembly as set forth in claim 4 wherein said processor is configured to utilize the calculated time of flight in determining if a blockage exists on said cover.

6. The lidar sensor assembly as set forth in claim 2 wherein said processor is also in communication with said array of photodetectors and is configured to identify any objects in the field of view.

7. The lidar sensor assembly as set forth in claim 6 wherein said processor is further configured to detect a potential dispersion of light caused by a blockage on said cover based on signals generated by said array of photodetectors.

8. The lidar sensor assembly as set forth 7 wherein said processor determines if a blockage exists on said cover based on both the signal from the at least one photodiode and the signals from said array of photodetectors indicating a potential dispersion of light.

9. The lidar sensor assembly as set forth in claim 1 further comprising an integrated circuit coupled said array of photodetectors wherein said integrated circuit includes a plurality of unit cells and each unit cell is coupled to one photodetector of said array of photodetectors.

10. The lidar sensor assembly as set forth in claim 1 wherein said at least one photodiode comprises a first photodiode positioned separate from said array of photodetectors and a second photodiode positioned separate from said array of photodetectors and separate from said first photodiode.

11. The lidar sensor assembly as set forth in claim 1 wherein said array of photodetectors includes a first side and a second side opposite said first side and wherein said first photodiode is disposed adjacent said first side and said second photodiode is disposed adjacent said second side.

12. A method of detecting a blockage in a lidar sensor assembly, wherein the assembly includes a light source for generating light, transmission optics for delivering the light generated by the light source to a field of illumination, receiving optics for receiving light reflected off an object in a field of view generally corresponding to the field of illumination, a generally transparent cover disposed between the receiving optics and the field of view, an array of photodetectors for receiving the light from the receiving optics, and a processor in communication with the array of photodetectors, said method comprising: disposing at least one photodiode separate from the array of photodetectors for receiving light scattered by a blockage on the cover, the photodiode in communication with the processor; and sensing, with the processor, an electrical signal generated by the at least one photodiode indicative of light scattered by a blockage on the cover.

13. The method as set forth in claim 12 wherein the processor is in communication with the light source and further comprising calculating, with the processor, a time of flight of the light generated by said light source and received at the at least one photodiode.

14. The method as set forth in claim 13 further comprising utilizing the calculated time of flight and the electrical signal generated by the at least one photodiode in determining if a blockage exists on the cover.

15. The method as set forth in claim 12 wherein the at least one photodiode is disposed outside of the field of view of the array of photodetectors.