Delay time calibration of optical distance measurement devices, and associated systems and methods

Patent metadata

Field	Value
Publication number	US-10641875-B2
Application number	US-201815944561-A
Country	US
Kind code	B2
Filing date	Apr 3, 2018
Priority date	Aug 31, 2017
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

Representative embodiments of the present technology include a device for measuring distance to an object. The device comprises a light emitter configured to emit an outbound light pulse and a light sensor configured to receive a returning light pulse and output a pulse signal representing the returning light pulse. The device further comprises a field-programmable gate array (FPGA) coupled to the light sensor and including a time-to-digital converter (TDC) having a series of sequentially coupled delay units. Individual sequentially coupled delay units are associated with corresponding individual delay times. At least some of the sequentially coupled delay units have different individual delay times. The TDC is configured to measure timing information of the pulse signal based at least in part on the individual delay times of the sequentially coupled delay units. The device further includes a controller configured to calculate the distance to the object based on the timing information.

First claim

We claim:

1. A device for measuring a distance to an object, the device comprising:
a light emitter configured to emit an outbound light pulse;
a light sensor configured to receive a returning light pulse reflected from the object and output a pulse signal representing the returning light pulse;
a field-programmable gate array (FPGA) coupled to the light sensor and including a time-to-digital converter (TDC) having a series of sequentially coupled delay units, individual sequentially coupled delay units associated with corresponding individual delay units, wherein at least some of the sequentially coupled delay units have different individual delay times, and wherein the TDC is configured to measure timing information of the pulse signal by:
propagating an input signal through the series of sequentially coupled delay units, the input signal corresponding to one or more portions of the pulse signal,
generating a data sequence having a first segment of only digital “1” data values, a second segment of only digital “0” data values, and a bubble segment between the first and second segments, the bubble segment including at least one digital “1” data value between neighboring digital “0” values and/or at least one digital “0” value between neighboring digital “1” data values, and
determining a time value corresponding to a modification of the data sequence in which the at least one digital “1” data value of the bubble segment is moved toward the first segment and the at least one digital “0” data value of the bubble segment is moved toward the second segment; and
a controller configured to calculate the distance to the object based on the timing information.

2. The device of claim 1 wherein the light emitter, light sensor, FPGA, and controller are carried by an unmanned aerial vehicle, an autonomous vehicle, or a robot.

3. The device of claim 1 wherein the TDC includes a latch unit coupled to the series of sequentially coupled delay units.

4. The device of claim 3 wherein the latch unit includes a plurality of latches, and wherein individual latches are coupled to a corresponding delay unit of the sequentially coupled delay units and configured to latch an output of the corresponding delay unit.

5. The device of claim 4 wherein the data sequence includes the outputs latched by the plurality of latches.

6. The device of claim 4 wherein individual latches are associated with a corresponding latching time for latching the output of the corresponding delay unit.

7. The device of claim 6 wherein at least one of the latches has a latching time greater than the individual delay time of the corresponding delay unit.

8. The device of claim 7 wherein at least one digital data value of the bubble segment corresponds to the output latched by the at least one latch.

9. The device of claim 1 wherein the TDC is further configured to determine an adjusted time value that compensates for a delay time associated with the modification of the data sequence.

10. The device of claim 1 wherein:
the TDC includes a latch unit coupled to the series of sequentially coupled delay units, the latch unit including a plurality of latches, wherein individual latches are coupled to a corresponding delay unit of the sequentially coupled delay units and configured to latch an output of the corresponding delay unit, and wherein the data sequence includes the outputs latched by the plurality of latches; and
the TDC is configured to:
determine the time value by identifying a delay unit corresponding to the modification of the data sequence, and
determine an adjusted time value that compensates for a delay time associated with the modification of the data sequence.

11. The device of claim 1 wherein the TDC is configured to determine the time value by identifying a delay unit corresponding to the modification of the data sequence.

12. The device of claim 8 wherein the first segment is positioned before the second segment, and wherein the identified delay unit corresponds to a digital “1” data value of the first segment adjacent to the second segment in the modification of the data sequence.

13. The device of claim 8 wherein the second segment is positioned before the first segment, and wherein the identified delay unit corresponds to a digital “0” data value of the second segment adjacent to the first segment in the modification of the signal.

14. A method for measuring distance to an object, the method comprising:
emitting, by a light emitter, an outbound light pulse;
receiving, at a light sensor, a returning light pulse reflected from the object;
outputting, by the light sensor, a pulse signal representing the returning light pulse;
measuring, using a field-programmable gate array (FPGA), timing information of the pulse signal, wherein the FPGA includes a time-to-digital converter (TDC) having a series of sequentially coupled delay units, and wherein the TDC is configured to measure the timing information of the pulse signal by:
propagating an input signal through the series of sequentially coupled delay units, the input signal corresponding to one or more portions of the pulse signal,
generating a data sequence having a first segment of only digital “1” data values, a second segment of only digital “0” data values, and a bubble segment between the first and second segments, the bubble segment including at least one digital “1” data value between neighboring digital “0” values and/or at least one digital “0” value between neighboring digital “1” data values, and
determining a time value corresponding to a modification of the data sequence in which the at least one digital “1” data value of the bubble segment is moved toward the first segment and the at least one digital “0” data value of the bubble segment is moved toward the second segment; and

calculating, using a controller, the distance to the object based at least in part on the timing information.

15. The method of claim 14 wherein the light emitter, light sensor, FPGA, and controller are carried by an unmanned vehicle, autonomous vehicle, or robot, and wherein the method further comprises controlling operation of the unmanned aerial vehicle, autonomous vehicle, or robot based at least in part on the calculated distance to the object.

16. The method of claim 14 wherein generating the data sequence comprises latching outputs of the series of sequentially coupled delay units using a plurality of latches as the input signal propagates through the series of sequentially coupled delay units.

17. The method of claim 16 wherein generating the data sequence comprises latching an output of a delay unit using a latch having a latching time greater than the individual delay time of the delay unit, the latched output corresponding to at least one digital data value of the bubble segment.

18. The method of claim 16 wherein generating the data sequence comprises latching an output of a delay unit using a latch having a latching time shorter than the individual delay time of the delay unit, the latched output corresponding to at least one digital data value of the first or second segment.

19. The method of claim 14 wherein determining the time value comprises identifying a delay unit corresponding to the modification of the data sequence.

Assignees

• Sz Dji Technology Co Ltd

Inventors

• Liu Xiang
• Gao Mingming
• Hong Xiaoping
• Wu Di

Classifications

• H03K2005/00078

  Fixed delay · CPC title

• H03K5/01

  Shaping pulses (discrimination against noise or interference H03K5/125) · CPC title

• G01S7/4861

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

• G01S17/10

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G04F10/005

  Time-to-digital converters [TDC] (analog-to-digital converters with intermediate conversion to time or phase H03M1/50, H03M1/60) · CPC title