Multiplexed multichannel photodetector

Patent metadata

Field	Value
Publication number	US-10234546-B2
Application number	US-201815947515-A
Country	US
Kind code	B2
Filing date	Apr 6, 2018
Priority date	Mar 26, 2015
Publication date	Mar 19, 2019
Grant date	Mar 19, 2019

Abstract

A light detection and ranging (LIDAR) system can emit light toward an environment and detect responsively reflected light to determine a distance to one or more points in the environment. The reflected light can be detected by a plurality of plurality of photodiodes that are reverse-biased using a high voltage. Signals from the plurality of reverse-biased photodiodes can be amplified by respective transistors and applied to an analog-to-digital converter (ADC). The signal from a particular photodiode can be applied to the ADC by biasing a respective transistor corresponding to the particular photodiode while not biasing transistors corresponding to other photodiodes. The gain of each photodiode/transistor pair can be controlled by adjusting the bias voltage applied to each photodiode using a digital-to-analog converter. The gain of each photodiode/transistor pair can be controlled based on the detected temperature of each photodiode.

First claim

What is claimed is:

1. A system comprising:
a first light source;
a second light source;
a plurality of photodetector channels, wherein each photodetector channel of the plurality of photodetector channels comprises:
a photodiode, wherein the photodiode is configured to provide a photodiode signal indicative of light incident on the photodiode; and
a transistor, wherein the transistor has an input coupled to the photodiode and an output, and wherein the transistor is configured to provide the photodiode signal at the output when the transistor is operationally biased; and

a controller, operatively coupled to the first light source, the second light source, and the plurality of photodetector channels, and comprising one or more processors configured to execute computer-readable program instructions stored in a computer-readable data storage, wherein execution of the program instructions causes performance of functions, the functions comprising:
emitting light from the first light source at a first emission time;
selecting, during a first period of time, a first photodetector channel of the plurality of photodetector channels, wherein the first photodetector channel is configured to detect a reflected portion of light emitted from the first light source, and wherein selecting the first photodetector channel comprises operating a channel selector to operationally bias the respective transistor of the first photodetector channel;
emitting light from the second light source at a second emission time; and
selecting, during a second period of time, a second photodetector channel of the plurality of photodetector channels, wherein the second photodetector channel is configured to detect a reflected portion of light emitted from the second light source, and wherein selecting the second photodetector channel comprises operating the channel selector to operationally bias the respective transistor of the second photodetector channel.

2. The system of claim 1 , wherein the functions further comprise:
detecting, during the first period of time, the reflected portion of light emitted from the first light source light received by the respective photodiode of the first photodetector channel by detecting the output of the respective transistor of the first photodetector channel; and
detecting, during the second period of time, the reflected portion of light emitted from the second light source received by the respective photodiode of the second photodetector channel by detecting the output of the respective transistor of the second photodetector channel.

3. The system of claim 1 , further comprising a third light source, wherein the controller is operatively coupled to the third light source, wherein the functions further comprise:
emitting light from the third light source at a third emission time;
selecting, during a third period of time, a third photodetector channel of the plurality of photodetector channels, wherein the third photodetector channel is configured to detect a reflected portion of light emitted from the third light source, and wherein selecting the third photodetector channel comprises operating the channel selector to operationally bias the respective transistor of the third photodetector channel; and
detecting, during the third period of time, the reflected portion of light emitted from the third light source received by the respective photodiode of the third photodetector channel by detecting the output of the respective transistor of the third photodetector channel.

4. The system of claim 1 , wherein the first period of time is different from the second period of time.

5. The system of claim 1 , wherein the first emission time and the second emission time are substantially the same.

6. The system of claim 1 , further comprising:
a multiplexor; and
an analog-to-digital converter;
wherein the controller is operatively coupled to the multiplexor and the analog-to-digital converter, and wherein the functions further comprise:
multiplexing a respective photodiode signal from the first photodetector channel and a second photodiode signal from the second photodetector channel using the multiplexor;
applying the multiplexed respective photodiode signals to a single analog-to-digital converter; and
detecting the reflected portion of light emitted from the first light source and the reflected portion of light emitted from the second light source using the analog-to-digital converter.

7. The system of claim 1 , wherein the functions further comprise:
determining a first reception time for the reflected portion of light emitted from the first light source relative to the first emission time based on the output of the respective transistor of the first photodetector channel; and
determining a second reception time for the reflected portion of light emitted from the second light source relative to the second emission time based on the output of the respective transistor of the first photodetector channel.

8. The system of claim 7 , wherein the functions further comprise:
determining a distance from the first light source to an aspect of an environment illuminated by the light emitted by the first light source based on the determined first reception time; and
determining a distance from the second light source to another aspect of the environment illuminated by the light emitted by the second light source based on the determined second reception time.

9. The system of claim 1 , wherein each respective photodetector channel of the plurality of photodetector channels further comprises a respective capacitor, wherein operating the channel selector to operationally bias the respective transistor of the first photodetector channel comprises providing a biasing voltage between the respective capacitor and the respective transistor in the first photodetector channel, and wherein operating the channel selector to operationally bias the respective transistor of the second photodetector channel comprises providing a biasing voltage between the respective capacitor and the respective transistor in the second photodetector channel.

10. A method comprising:
emitting light from a first light source at a first emission time;
selecting, during a first period of time, a first photodetector channel of a plurality of photodetector channels, wherein each photodetector channel of the plurality of photodetector channels comprises:
a photodiode, wherein the photodiode is configured to provide a photodiode signal indicative of light incident on the photodiode; and
a transistor, wherein the transistor has an input coupled to the photodiode and an output, and wherein the transistor is configured to provide the photodiode signal at the output when the transistor is operationally biased;

wherein the first photodetector channel is configured to detect a reflected portion of light emitted from the first light source, and wherein selecting the first photodetector channel comprises operating a channel selector to operationally bias the respective transistor of the first photodetector channel;
emitting light from a second light source at a second emission time; and
selecting, during a second period of time, a second photodetector channel of the plurality of photodetector channels, wherein the second photodetector channel is configured to detect a reflected portion of light emitted from the second light source, and wherein selecting the second photodetector channel comprises operating the channel selector to operationally bias the respective transistor of the second photodetector channel.

11. The method of claim 10 , further comprising:
detecting, during the first period of time, the reflected porti

Assignees

• Waymo Llc

Inventors

• Droz Pierre-Yves
• Lenius Samuel William

Classifications

• H04N25/77

  Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components · CPC title

• G01S7/4865

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title

• H04N5/341

  Electricity · mapped topic

• H04N5/3745

  Electricity · mapped topic

• G01S7/484

  Transmitters · CPC title