Patent Application
20200174156
This invention relates to advanced driver assist systems or autonomous driving vehicles using LIDAR (Light Detection and Ranging), camera and, in particular, to a system using a High Resolution Flash LIDAR (HFL) sensor that detects when the field of view is blocked by foreign material causing performance degradation.
LIDAR sensors like camera, radar and other ADAS sensors suffer from significant performance degradation when the field of view of the sensor is blocked by any foreign material, i.e., when dirt or other foreign materials deposit on the window of the sensor through which it views the environment. In the particular case of an HFL sensor, the impact of blockage will be significant as the sensor is mounted outside of the car where it is directly affected by the environment making it susceptible to blockage. These blockage materials and structures on the window include, but are not limited to, water drops, snow, salt, ice, condensation, splash, spray, dirt, mud, dust, fouling, stickers, shatter, scratch etc.
In the case of blockage, the performance of the HFL sensor degrades due to the following main reasons. First, the power of the laser light source is partially or fully blocked reducing the maximum detectable distance. Secondly, the blocking materials degrade the quality of the image or point cloud by decreasing the resolution, contrast, sharpness and range accuracy. In addition, the blocking materials hinder the view of part of or all of the field of view. Finally, most blocking materials create a halo around objects creating false returns around objects.
As shown in
Normally this light leakage introduces a negligible signal on the receiving portion R if the window 18 is very clean. However, in cases where there are some particles or materials 20 the surface of the window 18, the amount of leakage signal significantly increases blinding the sensor 10 for close distances. The foreign materials on the glass window 18 increase the guided light through the window 18 by increasing the reflection or scattering of laser light L between the glass and blockage interface.
To address the above issues, another conventional HFL sensor 10′, shown in
However, neither sensors 10 nor 10′ can detect the blockage or foreign materials on the window 18 reliably without impairing the normal functionality (object sensing) of the sensor.
Thus, there is a need to detect the blockage or foreign materials on a window of a LIDAR sensor at all times to help take appropriate measures in event of such blockage.
An objective of the invention is to fulfill the need referred to above. In accordance with the principles of an embodiment, this objective is achieved by a LIDAR sensor having an illumination portion including a light source. A receiving portion is adjacent to the illumination portion. The receiving portion has receiver optics and at least one photodetector for receiving light, sent from the light source that is reflected from an object in a field of view of the receiver optics. A first partition separates the illumination portion from the receiving portion so that light from the light source cannot enter the receiving portion due to the first partition. A blockage detection portion of the sensor is adjacent to the illumination portion. A second partition separates the illumination portion from the blockage detection portion. A first window portion extends from the receiving portion to the illumination portion, and a second window portion extends from the illumination portion to the blockage detection portion. The first partition separates the first window portion from the second window portion to prevent light from the light source from entering the receiving portion via the window portions, with the reflected light being able to pass through the window to the photodetector or array of photodetectors. The second partition permits light, from the illumination portion that is scattered when foreign material is on a surface of the window, to pass into the blockage detection portion. The blockage detection portion includes a photodiode and structure defining that is constructed and arranged to allow the scattered light to pass through the aperture and collect on the on a photodiode.
In accordance with another aspect of an embodiment, a method for detecting foreign material on a window of a LIDAR sensor and of detecting a bad weather condition in an environment is provided. The LIDAR sensor has an illumination portion including a light source; a receiving portion adjacent to the illumination portion having a photodetector for receiving light, sent from the light source, that is reflected from an object in a field of view of the photodetector; a blockage detection portion adjacent to the illumination portion; and a window portion extending from the illumination portion to the blockage detection portion. The method prevents light, from the light source that is scattered when foreign material is on a surface of the window or when a bad weather condition is present, to pass into the receiving portion. Light, from the light source that is scattered when foreign material is on a surface of the window or when the bad weather condition is present, is permitted to pass into the blockage detection portion. The scattered light is collected on at least one photodiode disposed in the blockage detection portion.
Other objectives, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:
With reference to
The HFL sensor 10″ has an activation illumination portion (I) including a laser 11 and a flash detector 13, and a receiving portion (R) including receiver optics such as a lens 12 and a photodetector such as a PIN photodiode or a detector array 14 for receiving reflected light RL. In the embodiment of
In accordance with the embodiment, a blockage detection portion B is provided adjacent to the illumination portion I. The window portion 18′ extends from the illumination portion I to the blockage detection portion. As shown in
Within the blockage detection portion B, there structure such as a lens or a member defining a pinhole aperture 26, that is constructed and arranged to allow leaked or scattered laser light SL to collect on one or more photodiodes 28. The photodiode 28 is mounted on a printed circuit board 30 of the sensor 10″ and converts the collected scattered laser light SL to electrical current.
The photodiode 28 is connected with an integrated circuit (IC) 32 that is mounted on the circuit board 30. With reference to
Thus, as shown in
The main blockage detection criteria is the reception of a signal on blockage photodiode 28 whose distance is very close (<50 cm). Reception of a signal on the photodiode 28 alone does not guarantee a detection of blockage as light from a far object could be sensed by the blockage photodiode 28. However, the sensing capability of the blockage photodiode 28 is significantly reduced for far objects with the use of the pinhole 26 instead of a lens. This is why a pinhole is used as a preferred embodiment to reduce the ambiguity of the blockage detection. In addition, existence and non-existence of object in the main receiving channel of the LIDAR sensor can also be used as an input for blockage detection. Absence of an object in the main receiving channel and existence of a very close range signal on the blockage detection channel leads to high reliability of blockage detection. Moreover, amplitude of the signal on the blockage photodiode 28 and kinematics of the vehicle will be further used to qualify existence of blockage.
It can be appreciated that the functions of the control unit 24 can be integrated into the sensor 10″ by providing the processor circuit 38 and memory circuit 40 on the circuit board 30.
With reference to
In the embodiment of
When a blockage of light is detected by the sensor 10″ such to exceed a predetermined threshold, the control unit 24 or processor circuit 38 thereof can generate a signal to activate a cleaner 42 (
The system 22 can be used to detect bad weather. With reference to
Advantages of the system 22 of the embodiment include:
The operations and algorithms described herein can be implemented as executable code within a the IC 32 or control unit 24 having processor circuit 38 as described, or stored on a standalone computer or machine readable non-transitory tangible storage medium that are completed based on execution of the code by a processor circuit implemented using one or more integrated circuits. Example implementations of the disclosed circuits include hardware logic that is implemented in a logic array such as a programmable logic array (PLA), a field programmable gate array (FPGA), or by mask programming of integrated circuits such as an application-specific integrated circuit (ASIC). Any of these circuits also can be implemented using a software-based executable resource that is executed by a corresponding internal processor circuit such as a micro-processor circuit (not shown) and implemented using one or more integrated circuits, where execution of executable code stored in an internal memory circuit causes the integrated circuit(s) implementing the processor circuit to store application state variables in processor memory, creating an executable application resource (e.g., an application instance) that performs the operations of the circuit as described herein. Hence, use of the term “circuit” in this specification refers to both a hardware-based circuit implemented using one or more integrated circuits and that includes logic for performing the described operations, or a software-based circuit that includes a processor circuit (implemented using one or more integrated circuits), the processor circuit including a reserved portion of processor memory for storage of application state data and application variables that are modified by execution of the executable code by a processor circuit. The memory circuit 40 can be implemented, for example, using a non-volatile memory such as a programmable read only memory (PROM) or an EPROM, and/or a volatile memory such as a DRAM, etc.
The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.
