Dynamic receiver gain control for LiDAR system
Embodiments of the disclosure provide an optical sensing system, a method for controlling a receiver gain in the optical sensing system, and a receiver in the optical sensing system. The exemplary optical sensing system includes a transmitter configured to emit light beams at a plurality of vertical detection angles to scan an object. The optical sensing system further includes a receiver having a detector configured to detect the light beams returned by the object. The optical sensing system also includes a controller configured to dynamically vary a gain of the detector for detecting the light beams of the respective vertical detection angles.
1. An optical sensing system comprising:
a transmitter configured to emit light beams at a plurality of vertical detection angles to scan an object;
a receiver comprising a detector configured to detect the light beams returned by the object; and
a controller configured to dynamically vary a gain of the detector for detecting the light beams of the respective vertical detection angles based on a predetermined look-up table mapping the respective vertical detection angles to target detector gains, wherein the controller is further configured to determine a first reflectivity of the object based on the light beams received by the receiver and adjust the gain of the detector by a ratio of the first reflectivity and a second reflectivity of a ground.
2. The optical sensing system of claim 1 , wherein to dynamically vary the gain of the detector, the controller is further configured to:
reduce the gain when the vertical detection angle surpasses a threshold angle, wherein the threshold angle is determined based on an elevation of the optical sensing system positioned above a ground and a threshold detection distance of the optical sensing system.
3. The optical sensing system of claim 1 , wherein the target detector gains are proportional to a square of the respective detection distances determined based on an elevation of the optical sensing system positioned above a ground and the respective vertical detection angles.
4. The optical sensing system of claim 1 , further comprising a saturation detection circuit configured to detect a saturation condition of the detector, wherein the controller is further configured to fine tune the gain of the detector until the saturation condition disappears.
5. The optical sensing system of claim 1 , further comprising a saturation detection circuit coupled to the detector,
wherein the controller is configured to reduce the gain of the detector when the saturation detection circuit detects a saturation condition of the detector when receiving the light beam of a vertical detection angle.
6. The receiver optical sensing system of claim 5 , wherein the detector comprises a photodetector, a signal amplifier, and a signal conditioning circuit,
wherein the controller is configured to reduce a gain of the photodetector, the signal amplifier, or the signal conditioning circuit from which the saturation detection circuit detects the saturation condition.
7. The optical sensing system of claim 1 , wherein the detector comprises a photodetector configured to generate electrical signals in response to receiving the light beams of the respective vertical detection angles,
wherein to dynamically vary the gain of the detector, the controller is further configured to vary a bias voltage of the photodetector.
8. The optical sensing system of claim 1 , wherein the detector comprises a signal amplifier configured to amplify electrical signals generated in response to receiving the light beams of the respective vertical detection angles,
wherein to dynamically vary the gain of the detector, the controller is further configured to vary a gain of the signal amplifier.
9. The optical sensing system of claim 1 , wherein the detector comprises a signal conditioning circuit configured to condition electrical signals generated in response to receiving the light beams of the respective vertical detection angles,
wherein to dynamically vary the gain of the detector, the controller is further configured to vary a gain of the signal conditioning circuit.
10. The optical sensing system of claim 1 , wherein the optical sensing system is a Light Detection and Ranging (LiDAR) system.
11. A method for controlling a receiver gain in an optical sensing system, comprising:
emitting, by a transmitter, light beams at a plurality of vertical detection angles to scan an object;
detecting, by a detector in a receiver, the light beams returned by the object;
dynamically varying, by a controller, a gain of the detector for detecting the light beams of the respective vertical detection angles;
determining, by the controller, a first reflectivity of the object based on the light beams received by the receiver; and
adjusting, by the controller, the gain of the detector by the ratio of the first reflectivity and a second reflectivity of a ground.
12. The method of claim 11 , further comprising reducing the gain of the detector when the vertical detection angle surpasses a threshold angle, wherein the threshold angle is determined based on an elevation of the optical sensing system positioned above a ground and a threshold detection distance of the optical sensing system.
13. The method of claim 11 , wherein the gain of the detector is dynamically varied based on a predetermined look-up table mapping the respective vertical detection angles to target detector gains.
14. The method of claim 13 , wherein the target detector gains are proportional to a square of the respective detection distances determined based on an elevation of the optical sensing system positioned above a ground and the respective vertical detection angles.
15. The method of claim 13 , wherein dynamically varying the gain of the detector further comprises:
detecting, by a saturation detection circuit, a saturation condition of the detector; and
fine tuning, by the controller, the gain of the detector unit until the saturation condition disappears.
16. The method of claim 11 , wherein dynamically varying the gain of the detector further comprises:
reducing the gain of the detector when a saturation detection circuit detects a saturation condition of the detector when receiving the light beam of a vertical detection angle.
17. The method of claim 11 , wherein the detector comprises a photodetector configured to generate electrical signals in response to receiving the light beams of the respective vertical detection angles,
wherein dynamically varying the gain of the detector further comprises varying a bias voltage of the photodetector.
18. A receiver in an optical sensing system, comprising:
a detector configured to detect light beams returned from an object scanned by the light beams emitted at a plurality of vertical detection angles; and
a controller configured to dynamically vary a gain of the detector based on a predetermined look-up table mapping the respective vertical detection angles to target detector gains, wherein the target detector gains are proportional to a square of detection distances determined based on an elevation of the optical sensing system positioned above a ground and the respective vertical detection angles, and wherein the controller is further configured to determine a first reflectivity of the object based on the light beams received by the receiver and adjust the gain of the detector by the ratio of the first reflectivity and a second reflectivity of a ground.