Lidar detector having a plurality of time to digital converters integrated onto a detector chip

• US 10,267,918 B2
• Filed: 06/25/2018
• Issued: 04/23/2019
• Est. Priority Date: 03/28/2017
• Status: Active Grant

• Current Assignee: Luminar Technologies, Inc.
• Original Assignee: Luminar Technologies, Inc.
• Inventors: LaChapelle, Joseph G., Eichenholz, Jason M., Gaalema, Stephen D., Russell, Austin K.
• Primary Examiner(s): Gaworecki, Mark R
• Application Number:
  US16/017,650
• Publication Number:
  US 20180306926A1
• Time in Patent Office: 302 Days
• CPC Class Codes: G01J 1/44 Electric circuits for command of an exposure part G03B7/02
• CPC Class Codes: G01J 2001/4466 Avalanche
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/4865 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 Class Codes: G01S 7/487 Extracting wanted echo signals , e.g. pulse detection
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating
• CPC Class Codes: H01L 31/03046 including ternary or quaternary compounds, e.g. GaAlAs, InGaAs, InGaAsP
• CPC Class Codes: H01L 31/09 Devices sensitive to infrared, visible or ultraviolet radiation H01L31/101 takes precedence
• CPC Class Codes: H01L 31/1085 the devices being of the Metal-Semiconductor-Metal [MSM] Schottky barrier type
• CPC Class Codes: H01L 31/167 the light sources and the devices sensitive to radiation all being semiconductor devices characterised by potential barriers

Abstract

A scanning system includes a light source configured to emit light as a series of one or more light pulses, a scanner configured to direct the one or more light pulses towards a remote target, and a receiver configured to detect light scattered by the remote target. The receiver includes a light detector element disposed on an ASIC that includes multiple comparators disposed in parallel with one another, and corresponding time-to-digital converters (TDCs) coupled to the comparator. Each of the comparators processes a received electrical signal from the light detector element to produce a digital edge signal when the amplitude of the received electrical signal reaches a particular threshold. A corresponding TDC outputs a time delay value associated with a time at which the received electrical signal reaches the particular threshold.

Claims

1. A scanning system, comprising:

a light source configured to emit light as a series of one or more light pulses;

a scanner configured to direct the one or more light pulses towards a remote target; and

a receiver configured to detect light scattered by the remote target, the receiver including a light detector element disposed on an application specific integrated circuit (ASIC), wherein the ASIC includes a plurality of comparators disposed in parallel with one another and a corresponding plurality of time-to-digital converters (TDCs) coupled to the comparators and wherein;

each of the plurality of comparators processes a received electrical signal from the light detector element to produce a digital edge signal when the amplitude of the received electrical signal reaches a particular threshold; and

a corresponding TDC of the plurality of TDCs outputs a time delay value associated with a time at which the received electrical signal reaches the particular threshold.

2. The scanning system of claim 1, wherein a first one of the plurality of comparators produces a digital edge signal when the amplitude of the received electrical signal reaches a particular threshold in the rising direction and a second one of the plurality of the comparators produces a digital edge signal when the amplitude of the received electrical signal reaches a particular threshold in the falling direction.

3. The scanning system of claim 1, wherein a first one of the plurality of comparators produces a digital edge signal when the amplitude of the received electrical signal reaches a particular threshold in the rising direction and a second one of the plurality of the comparators produces a digital edge signal when the amplitude of the received electrical signal reaches a different threshold in the rising direction.

4. The scanning system of claim 1, wherein a first multiplicity of the plurality of comparators produce a digital edge signal when the amplitude of the received electrical signal reaches one of a set of different thresholds in the rising direction and a second multiplicity of the plurality of the comparators produces a digital edge signal when the amplitude of the received electrical signal reaches one of the set of different thresholds in the falling direction.

5. The scanning system of claim 1, wherein a first one of the plurality of comparators produces a digital edge signal when the amplitude of the received electrical signal reaches a particular threshold and a second one of the plurality of the comparators produces a digital edge signal when the amplitude of the received electrical signal reaches a different threshold.

6. The scanning system of claim 1, wherein the receiver further comprises an envelope detector coupled to the plurality of TDCs that determines an amplitude envelope of a scattered light pulse based on the time delay values determined by the plurality of TDCs.

7. The scanning system of claim 6, wherein the envelope detector determines an amplitude envelope of the scattered light pulse based on the time delay values determined by three or more of the plurality of TDCs.

8. The scanning system of claim 1, wherein the receiver further comprises a center detector coupled to the plurality of TDCs that determines a center of a received scattered light pulse based on the time delay values determined by the plurality of TDCs.

9. The scanning system of claim 1, wherein the receiver further comprises a center detector coupled to the plurality of TDCs that determines a center of a received scattered light pulse based on the time delay values determined by exactly two of the plurality of TDCs.

10. The scanning system of claim 1, wherein one or more of the comparators are rising edge comparators and one or more other ones of the comparators are falling edge comparators.

11. A method of imaging a remote target, comprising:

generating a light pulse;

emitting the generated light pulse towards a remote target;

receiving a light pulse scattered by the remote target;

producing an electrical signal indicative of the received scattered light pulse;

comparing the electrical signal to each of a plurality of different thresholds to produce a plurality of comparator signals;

time-to-digital converting each of the plurality of comparator signals to produce a digital edge signal indicative of a time when the electrical signal reaches one of the thresholds; and

using the digital edge signals to image the remote target.

12. The method of imaging a remote target of claim 11, wherein comparing the electrical signal to each of a plurality of different thresholds includes simultaneously comparing the electrical signal to each of the plurality of different thresholds.

13. The method of imaging a remote target of claim 11, wherein producing the electrical signal includes producing an electrical signal for each of a plurality of temporal positions along the received scattered light pulse, and wherein comparing the electrical signal further includes comparing the electrical signal to each of a plurality of different thresholds to produce a plurality of comparator signals and time-to-digital converting includes time-to-digital converting each of the plurality of comparator signals to produce the digital edge signals at each of the plurality of temporal positions along the received scattered light pulse.

14. The method of imaging a remote target of claim 13, wherein using the digital edge signals to image the remote target includes determining a time delay associated with the received scattered light pulse based on the digital edge signals and determining a range to the remote target based on the time delay associated with the received scattered light pulse.

15. The method of imaging a remote target of claim 11, wherein comparing the electrical signal to each of a plurality of different thresholds to produce a plurality of comparator signals includes comparing the electrical signal to a first threshold in the rising direction and comparing the electrical signal to the first threshold in the falling direction.

16. The method of imaging a remote target of claim 11, wherein comparing the electrical signal to each of a plurality of different thresholds to produce a plurality of comparator signals includes comparing the electrical signal to a first threshold in the rising direction and comparing the electrical signal to a second threshold in the falling direction.

17. The method of imaging a remote target of claim 11, wherein comparing the electrical signal to each of a plurality of different thresholds to produce a plurality of comparator signals includes comparing the electrical signal to a first multiplicity of thresholds in the rising direction and comparing the electrical signal to the first multiplicity of thresholds in the falling direction.

18. An imaging system, comprising:

a laser light source that emits light as a series of one or more light pulses;

a controller that controls the laser light source to emit one or more light pulses towards a remote target;

a light detector configured to detect a light pulse scattered by the remote target to produce an electronic signal indicative of the received scattered light pulse;

a plurality of comparators disposed in parallel with one another, wherein each of the plurality of comparators processes the electronic signal from the light detector to produce a digital edge signal when the amplitude of the received light signal reaches a threshold associated with the comparator;

a plurality of time-to-digital converters (TDCs) coupled to the comparators, wherein each of the plurality of TDCs receives a digital edge signal from a corresponding comparator and outputs a time delay value associated with a time at which the electronic signal reaches the threshold of the corresponding comparator; and

an imaging processor that processes the time delay values to image the remote target.

19. The imaging system of claim 18, wherein each of the TDCs is coupled to the controller to receive an indication of a time at which a light pulse was emitted towards the remote target and wherein the time delay values output by the TDCs indicate a time between when the light pulse was emitted and the electronic signal reached a threshold of an associated one of the comparators.

20. The imaging system of claim 18, wherein the imaging processor comprises a range detector that determines, based on the time delay values, a timing of the receipt of the received light pulse, and that determines, based on the timing of the receipt of the received light pulse, a distance to the remote target.