Light detectors for nearby object detection in light detection and ranging (lidar) devices

Patent metadata

Field	Value
Publication number	US-12560716-B2
Application number	US-202217806629-A
Country	US
Kind code	B2
Filing date	Jun 13, 2022
Priority date	Jun 13, 2022
Publication date	Feb 24, 2026
Grant date	Feb 24, 2026

Abstract

Example embodiments relate to light detectors for nearby object detection in light detection and ranging (lidar) devices. An example embodiment includes a lidar device. The lidar device includes a light emitter configured to emit a light signal at a first time. The lidar device also includes a light detector configured to detect the emitted light signal. Additionally, the lidar device includes a biasing circuit configured to modify a detector bias using a bias signal. The bias signal ramps the detector bias from a first bias level at the first time to a second bias level at a second time. The second time is separated from the first time by a ramp duration. The ramp duration is sufficient to prevent any internal feedback within the lidar device caused by the emitted light signal from saturating the light detector or detection circuitry associated with the light detector.

First claim

What is claimed is:

1 . A light detection and ranging (lidar) device comprising:
a light emitter configured to emit a light signal at a first time; a light detector configured to detect the light signal emitted by the light emitter; a biasing circuit configured to modify a detector bias of the light detector using a bias signal, wherein the bias signal ramps the detector bias from a first bias level at the first time to a second bias level at a second time, wherein the second time occurs after the first time and is separated from the first time by a ramp duration, wherein the second bias level is greater than the first bias level, and wherein the ramp duration is sufficient to prevent any internal feedback within the lidar device caused by the emitted light signal from saturating the light detector or detection circuitry associated with the light detector; and a controller configured to:
cause the light emitter to emit a calibration signal;
receive a detected calibration signal from the light detector, wherein the detected calibration signal was detected by the light detector based on the emitted calibration signal while the biasing circuit was modifying the detector bias of the light detector using the bias signal;
cause the light emitter to emit an object-detection signal;
receive a detected object-detection signal from the light detector, wherein the detected object-detection signal was detected by the light detector based on the emitted object-detection signal while the biasing circuit was modifying the detector bias of the light detector using the bias signal; and
generate a modified object-detection signal by subtracting the detected calibration signal from the detected object-detection signal.

2 . The lidar device of claim 1 , wherein the light detector comprises one or more silicon photomultipliers (SiPMs).

3 . The lidar device of claim 2 , wherein the first bias level corresponds to a linear mode of the one or more SiPMs, and wherein the second bias level corresponds to a Geiger mode of the one or more SiPMs.

4 . The lidar device of claim 1 , further comprising a housing, wherein the ramp duration is:
at least as long as a transit time for the light signal to propagate from the light emitter to the housing and then from the housing back to the light detector; or at least as long as a transit time for the light signal to propagate from the light emitter to debris disposed on the housing and then from the debris disposed on the housing back to the light detector.

5 . The lidar device of claim 1 , wherein the bias signal ramps the detector bias from the first bias level at the first time to the second bias level at the second time in three stages, and wherein the three stages comprise:
a first non-linear stage that ramps from the first bias level to a first intermediate bias level; a linear stage that ramps from the first intermediate bias level to a second intermediate bias level; and a second non-linear stage that ramps from the second intermediate bias level to the second bias level.

6 . The lidar device of claim 1 , wherein the bias signal ramps the detector bias from the first bias level at the first time to the second bias level in one or more stages, and wherein the one or more stages comprises a stage that exponentially ramps the detector bias.

7 . The lidar device of claim 1 , wherein the bias signal ramps the detector bias from the first bias level at the first time to the second bias level in one or more stages, and wherein the one or more stages comprises a stage that logarithmically ramps the detector bias.

8 . The lidar device of claim 1 , wherein the controller is configured to cause the biasing circuit to adjust the bias signal, and wherein the controller is configured to cause the biasing circuit to adjust the ramp duration of the bias signal based on a desired minimum-detectable distance to a target in a surrounding environment.

9 . The lidar device of claim 1 , further comprising an external enclosure, wherein the second time corresponds to a detection time associated with a distance from the light emitter to the external enclosure to the light detector.

10 . The lidar device of claim 1 , wherein generating the modified object-detection signal comprises:
removing, from the detected object-detection signal, an influence of the bias signal on detection circuitry of the light detector; or removing, from the detected object-detection signal, an influence of the internal feedback within the lidar device caused by the emitted light signal.

11 . The lidar device of claim 1 , wherein the controller is configured to cause the biasing circuit to adjust the bias signal based on a temperature of the light detector.

12 . The lidar device of claim 11 , wherein the controller is configured to cause the biasing circuit to:
increase a slope along at least one portion of the bias signal in response to an increase in the temperature of the light detector; or decrease a slope along at least one portion of the bias signal in response to a decrease in the temperature of the light detector.

13 . The lidar device of claim 11 , wherein the controller is configured to cause the biasing circuit to:
increase the second bias level in response to an increase in the temperature of the light detector; or decrease the second bias level in response to a decrease in the temperature of the light detector.

14 . The lidar device of claim 11 , wherein the controller is configured to adjust the ramp duration based on the temperature of the light detector.

15 . The lidar device of claim 11 , further comprising a temperature sensor configured to measure the temperature of the light detector or near the light detector, wherein the controller is communicatively coupled to the temperature sensor, and wherein the controller is configured to determine the temperature of the light detector based on data received from the temperature sensor.

16 . The lidar device of claim 1 , wherein the biasing circuit comprises:
a capacitor configured to store charge in order to produce a voltage differential across terminals of the capacitor; a boost converter configured to charge the capacitor based on a voltage input; and one or more switching devices used with the capacitor to selectively produce a voltage differential across the light detector, resulting in the detector bias.

17 . The lidar device of claim 1 , wherein the second bias level is between about 30 V and about 70 V.

18 . A method comprising:
emitting, by a light emitter of a light detection and ranging (lidar) device, a light signal at a first time; detecting, by a light detector of the lidar device, the light signal emitted by the light emitter; modifying, by a biasing circuit of the lidar device, a detector bias of the light detector using a bias signal, wherein the bias signal ramps the detector bias from a first bias level at the first time to a second bias level at a second time, wherein the second time occurs after the first time and is separated from the first time by a ramp duration, wherein the second bias level is greater than the first bias level, and wherein the ramp duration is sufficient to prevent any internal feedback within the lidar device caused by the emitted light signal from saturating the light detector or detection circuitry associated with the light detector; causing, by a controller of the lidar device, the light emitter to emit a calibration signal; receiving, by the controller of the lidar device, a detected calibrati

Assignees

• Waymo Llc

Inventors

• Bogatko Alex
• Onal Caner
• Karplus Paul

Classifications

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title

• G01S7/4861

  Circuits for detection, sampling, integration or read-out · CPC title

• G01S7/4817

  relating to scanning · CPC title

• G01S17/894

  Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar · CPC title

• G01S17/931

  of land vehicles · CPC title