Waveform design for a LiDAR system with closely-spaced pulses

Patent metadata

Field	Value
Publication number	US-10955552-B2
Application number	US-201715844665-A
Country	US
Kind code	B2
Filing date	Dec 18, 2017
Priority date	Sep 27, 2017
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

Depth-sensing apparatus includes a laser, which is configured to emit pulses of optical radiation toward a scene. One or more detectors are configured to receive the optical radiation that is reflected from points in the scene and to output signals indicative of respective times of arrival of the received radiation. Control and processing circuitry is coupled to drive the laser to emit a succession of output sequences of the pulses with different, respective temporal spacings between the pulses within the output sequences in the succession, and to match the times of arrival of input sequences of the signals to the temporal spacings of the output sequences in order to find respective times of flight for the points in the scene.

First claim

The invention claimed is:

1. Depth-sensing apparatus, comprising:
a laser, which is configured to emit pulses of optical radiation toward a scene;
one or more detectors, which are configured to receive the optical radiation that is reflected from points in the scene and to output signals indicative of respective times of arrival of the received radiation; and
control and processing circuitry, which is coupled to drive the laser to emit a succession of output sequences of the pulses such that successive output sequences within the succession have different, respective temporal spacings between the pulses within each of the successive output sequences, and to match the times of arrival of input sequences of the signals to the temporal spacings of the output sequences in order to find respective times of flight for the points in the scene.

2. The depth-sensing apparatus according to claim 1 , wherein the output sequences comprise temporally-separated tuples of the pulses.

3. The depth-sensing apparatus according to claim 1 , wherein the output sequences are mutually overlapping.

4. The depth-sensing apparatus according to claim 3 , wherein each output sequence comprises a number N of pulses, such that N>1, and wherein consecutive output sequences have N−1 pulses in common, such that a second pulse of any given output sequence is a first pulse of a succeeding output sequence.

5. The depth-sensing apparatus according to claim 1 , wherein the control and processing circuitry is configured to identify a signal output by the one or more detectors due to a stray-light pulse, to identify an emitted pulse in an input sequence that temporally coincides with the stray-light pulse, and to remove the identified pulse from the input sequence while adding to the input sequence a further pulse from a neighboring sequence in matching the times of arrival.

6. The depth-sensing apparatus according to claim 1 , wherein the control and processing circuitry is configured to construct a depth map of the scene based on the times of flight.

7. The depth-sensing apparatus according to claim 1 , wherein the control and processing circuitry is configured to match the times of arrival of the pulses in each input sequence to the temporal spacings of the output sequences by calculating a respective fit between the times of arrival of the input sequence and each output sequence within a selected time period, calculating a residual of each respective fit, and identifying the output sequence yielding a minimum value of the residual among all residuals as the output sequence associated with the input sequence.

8. The depth-sensing apparatus according to claim 7 , wherein the control and processing circuitry is configured, in calculating the respective fit, to apply a linear transformation to each output sequence to account for a tilt of a planar region of the scene relative to a line of sight of the apparatus, and to calculate the respective fit between the times of arrival of each input sequence and each output sequence following the linear transformation.

9. A method for depth sensing, comprising:
emitting a succession of output sequences of pulses of optical radiation toward a scene, such that successive output sequences within the succession have different, respective temporal spacings between the pulses within each of the successive output sequences;
receiving the optical radiation that is reflected from points in the scene at one or more detectors, which output signals indicative of respective times of arrival of the received radiation; and
matching the times of arrival of input sequences of the signals to the temporal spacings of the output sequences in order to find respective times of flight for the points in the scene.

10. The method according to claim 9 , wherein the output sequences comprise temporally-separated tuples of the pulses.

11. The method according to claim 9 , wherein the output sequences are mutually overlapping.

12. The method according to claim 11 , wherein each output sequence comprises a number N of pulses, such that N>1, and wherein consecutive output sequences have N−1 pulses in common, such that a second pulse of any given output sequence is a first pulse of a succeeding output sequence.

13. The method according to claim 9 , wherein matching the times of arrival comprises identifying a signal output by the one or more detectors due to a stray-light pulse, identifying an emitted pulse in an input sequence that temporally coincides with the stray-light pulse, and removing the identified pulse from the input sequence while adding to the input sequence a further pulse from a neighboring sequence in matching the times of arrival.

14. The method according to claim 9 , and comprising constructing a depth map of the scene based on the times of flight.

15. The method according to claim 9 , wherein matching the times of arrival comprises calculating a respective fit between the times of arrival of the input sequence and each output sequence within a selected time period, calculating a residual of each respective fit, and identifying the output sequence yielding a minimum value of the residual among all residuals as the output sequence associated with the input sequence.

16. The method according to claim 15 , wherein calculating the respective fit comprises applying a linear transformation to each output sequence to account for a tilt of a planar region of the scene relative to a line of sight of the apparatus, and calculating the respective fit between the times of arrival of each input sequence and each output sequence following the linear transformation.

Assignees

• Apple Inc

Inventors

• Fine Nadav
• Barak Oz
• Kaitz Tal

Classifications

• G01S17/32 Primary

  using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated · CPC title

• G01S17/10 Primary

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