SPAD based indirect time of flight sensing from solid state transmitter scanning

Patent metadata

Field	Value
Publication number	US-11960033-B2
Application number	US-202318126165-A
Country	US
Kind code	B2
Filing date	Mar 24, 2023
Priority date	Apr 30, 2020
Publication date	Apr 16, 2024
Grant date	Apr 16, 2024

Abstract

Described herein is a time-of-flight ranging system and methods for its operation. The system includes an array of single photon avalanche diode (SPAD) pixels and control circuitry. The control circuitry simultaneously accumulates integrated SPAD event data from one cluster of SPAD pixels while integrating SPAD event data from another cluster during different target illuminations. The system also includes first and second VCSEL clusters, each responsible for a different target illumination. By processing and managing the data in this manner, the system can effectively reduce the time used to gather and analyze the event data, leading to faster and more accurate distance measurements.

First claim

The invention claimed is:

1. A time of flight ranging system, comprising:
an array of single photon avalanche diode (SPAD) pixels; and
control circuitry configured to, during different target illuminations, simultaneously accumulate integrated SPAD event data from a first cluster of SPAD pixels while integrating SPAD event data from a second cluster of SPAD pixels, and then simultaneously accumulate integrated SPAD event data from the second cluster of SPAD pixels while integrating SPAD event data from the first cluster of SPAD pixels.

2. The time of flight ranging system of claim 1 , wherein the control circuitry performs the simultaneous accumulation of integrated SPAD event data from the first cluster of SPAD pixels and integration of SPAD event data from the second cluster of SPAD pixels a given number of times.

3. The time of flight ranging system of claim 1 , wherein the control circuitry performs the simultaneous accumulation of integrated SPAD event data from the first cluster of SPAD pixels and integration of SPAD event data from the second cluster of SPAD pixels a first given number of times where the target illuminations are at a first frequency of light, and wherein the control circuitry performs the simultaneous accumulation of integrated SPAD event data from the second cluster of SPAD pixels and integration of SPAD event data from the first cluster of SPAD pixels a second given number of times where the target illuminations are at a second frequency of light.

4. The time of flight ranging system of claim 1 ,
wherein the control circuitry integrates the SPAD event data received from each SPAD pixel of the first cluster of SPAD pixels into counters;
wherein the control circuitry integrates the SPAD event data received from each SPAD pixel of the second cluster of SPAD pixels into the counters;
wherein the control circuitry accumulates the integrated SPAD event data that was received from each SPAD of the first cluster of SPAD pixels into a first memory; and
wherein the control circuitry accumulates the integrated SPAD event data that was received from each SPAD of the second cluster of SPAD pixels into a second memory.

5. The time of flight ranging system of claim 1 , wherein the control circuitry is further configured to determine a distance to the target by comparing a phase of the accumulated integrated SPAD event data to a phase of light that caused an associated illumination of the target.

6. The time of flight ranging system of claim 1 , further comprising first and second VCSEL clusters, wherein the first and second VCSEL clusters are distinct from one another; and wherein a first of the different target illuminations is performed by the first VCSEL cluster and a second of the different target illuminations is performed by the second VCSEL cluster.

7. The time of flight ranging system of claim 1 , wherein the first and second clusters of SPAD pixels are different subsets of an array of SPAD pixels.

8. A method for operating a time of flight ranging system, comprising:
a) integrating event data from a first single photon avalanche diode (SPAD) cluster during a first target illumination;
b) integrating event data from a second SPAD cluster during a second target illumination; and
at a start of b), accumulating event data that was integrated during a).

9. The method of claim 8 , wherein event data from both the first and second SPAD clusters is integrated into counters, and the integrated event data of the first SPAD cluster is accumulated into a memory at the start of b).

10. The method of claim 8 , further comprising:
c) integrating event data from the first SPAD cluster during a third target illumination; and
at a start of c), accumulating event data that was integrated during b).

11. The method of claim 10 , wherein event data from both the first and second SPAD clusters is integrated into counters, the integrated event data of the first SPAD cluster is accumulated into a first memory at the start of b), and wherein the integrated event data of the second SPAD cluster is accumulated into a second memory at the start of c).

12. The method of claim 8 , wherein the first target illumination is performed at a first frequency of light; and wherein the second target illumination is performed at a second frequency of light.

13. The method of claim 8 , further comprising determining a distance to the target by comparing a phase of the accumulated integrated SPAD event data to a phase of light that caused the first target illumination.

14. A method for time-of-flight sensing, comprising:
selectively driving each of VCSEL cluster of a plurality thereof at a predetermined frequency using a VCSEL driver generating a VCSEL drive pulse;
controlling activation of the VCSEL clusters and a corresponding plurality of SPAD clusters using a sequencer;
generating first, second, third, and fourth clock signals using a timing generator, wherein the first clock signal is in phase with the VCSEL drive pulse, wherein the third clock signal is an inverse of the first clock signal, wherein the second clock signal is delayed in phase compared to the first clock signal by one quarter of a period, and the fourth clock signal is an inverse of the second clock signal;
selectively routing output from an OR gate, which combines outputs from quench and readout circuitries associated with the SPAD clusters, to specific counters associated with the SPAD clusters using combination and gating circuitry based on windows of time created by the first, second, third, and fourth clock signals;
accumulating output of the counters for each SPAD cluster in a memory; and
causing repeated integrations and accumulations of SPAD events between pairs of associated SPAD clusters and VCSEL clusters at a desired number of frequencies using the sequencer.

15. The method of claim 14 , wherein a number of repetitions between pairs of associated SPAD clusters and VCSEL clusters is inversely proportional to a frame rate of the time-of-flight sensing to be performed.

16. The method of claim 14 , wherein rows in a given SPAD cluster are accumulated in parallel.

17. The method of claim 15 , further comprising performing the repetitions between pairs of associated SPAD clusters and VCSEL clusters at different VCSEL drive pulse frequencies, wherein the different VCSEL drive pulse frequencies are varied during operation.

Assignees

• St Microelectronics Grenoble 2

Inventors

• Mellot Pascal

Classifications

• H10F30/225

  the potential barrier working in avalanche mode, e.g. avalanche photodiodes · CPC title

• G01S7/4914 Primary

  of detector arrays, e.g. charge-transfer gates · 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

• G01S17/36

  with phase comparison between the received signal and the contemporaneously transmitted signal · CPC title

• H01L31/107

  Electricity · mapped topic