Methods and apparatus for phased array imaging

Patent metadata

Field	Value
Publication number	US-10073177-B2
Application number	US-201514939213-A
Country	US
Kind code	B2
Filing date	Nov 12, 2015
Priority date	Nov 14, 2014
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A method of imaging a scene includes generating a temporally varying optical intensity pattern from at least one continuous wave (CW) light beam. The method also includes illuminating at least one portion of the scene with the temporally varying optical intensity pattern so as to cause a photon to scatter or reflect off the at least one portion of the scene. The photon reflected or scatted from the at least one portion of the scene is detected using a single-photon detector. Based on the temporally varying optical intensity pattern and a time of flight of the photon detected, a distance between the single-photon detector and the at least one portion of the scene is estimated.

First claim

The invention claimed is:

1. A method of imaging a scene, the method comprising:
A) generating a temporally varying optical intensity pattern from at least one continuous wave (CW) light beam with an array of phased modulators;
B) illuminating at least one portion of the scene with the temporally varying optical intensity pattern generated in A) so as to cause a photon to scatter or reflect off the at least one portion of the scene;
C) detecting, using a single-photon detector, the photon reflected or scattered from the at least one portion of the scene in B); and
D) estimating a distance between the single-photon detector and the at least one portion of the scene based on the temporally varying optical intensity pattern generated in A) and a time of flight of the photon detected in C).

2. The method of claim 1 , wherein A) comprises generating a temporally varying interference pattern.

3. The method of claim 1 , wherein A) further comprises:
A 1 ) applying a first phase dither “δD” on a phased array and measuring a first intensity of a center portion of the temporally varying optical intensity pattern;
A 2 ) applying a second phase dither “−δD” and measuring a second intensity of the center portion of the temporally varying optical intensity pattern;
A 3 ) calculating a slope “S” of an intensity change based at least in part on the first intensity measured in A 1 ) and the second intensity measured in A 2 );
A 4 ) applying a second phase shift “Δφ 2 ” on the phased array, wherein Δφ 2 =Δφ 1 +S*δD, wherein “Δφ 1 ” is a first phase shift applied on the phased array before A 1 ); and
A 5 ) repeating A 1 ) through A 4 ) until the slope “S” is substantially equal to zero.

4. The method of claim 1 , wherein A) comprises modulating the array of phased modulators with respective radio-frequency signals to vary the temporally varying optical intensity pattern.

5. The method of claim 4 , wherein B) comprises:
B 1 ) applying a steering phase shift “(N−1)Δϕ” on a Nth phase modulator in the array of phased modulators; and
B 2 ) changing a variable phase shift “Δϕ” from 0 to 2π so as to sweep at least a portion of the temporally varying optical intensity pattern across the at least one portion of the scene.

6. The method of claim 5 , wherein B 2 ) further comprises:
aligning the phased array when the variable phase shift “Δϕ” is substantially close to zero so as to achieve simultaneous alignment of the array of phased modulators and beam steering.

7. The method of claim 5 , wherein B 2 ) comprises changing the variable phase shift from 0 to 2π within 50 ns.

8. The method of claim 5 , wherein B 2 ) comprises changing the variable phase shift from 0 to 2π at a repetition rate substantially equal to or greater than 20 MHz.

9. The method of claim 1 , wherein B) comprises:
B 1 ) during a first portion of a period, applying a phase dither on the array of phased modulators while measuring an intensity of a center portion of the temporally varying optical intensity pattern; and
B 2 ) during a second portion of the period, steering at least a portion of the temporally varying optical intensity pattern across the at least one portion of the scene.

10. The method of claim 9 , wherein the period is about 0.2 ms to about 2 ms.

11. The method of claim 9 , wherein the first portion is about 0.1% to about 1% of the period.

12. The method of claim 9 , wherein applying the phase dither in B) comprises applying a plurality of periodic dither cycles on the array of phased modulators, wherein B 1 ) comprises:
B 1 a ) in a first dither cycle in the plurality of periodic dither cycles, applying a first phase shift “Δφ 1 =Δφ 0 +δD” to the array of phased modulators while measuring a first intensity of the center portion of the temporally varying optical intensity pattern, wherein the first phase shift “Δφ 1 =Δφ 0 +δD” includes a first phase dither “δD” and a previous correction Δφ 0 based on a previous dither cycle; and
B 1 b ) in a second dither cycle in the plurality of periodic dither cycles, applying a second phase shift “Δφ 2 =Δφ 0 −δD” to the array of phased modulators while measuring a second intensity of the center portion of the temporally varying optical intensity pattern, wherein the second phase shift “Δφ 2 =Δφ 0 −δD” includes a second phase dither “−δD” and the previous correction Δφ 0 based on the previous dither cycle.

13. The method of claim 12 , further comprising:
B 1 c ) Calculating a new phase correction “Δφ n ”, wherein Δφ n =Δφ 0 +S*δD, “S” is a slope of an intensity change based at least in part on the first intensity measured in B 1 a ) and the second intensity measured in B 1 b ).

14. The method of claim 1 , wherein B) further comprises:
sweeping at least one bright portion of the temporally varying optical intensity pattern across the at least one portion of the scene within about 1 ns to about 10 ns.

15. The method of claim 1 , further comprising:
E) estimating a three-dimensional image of the at least one portion of the scene based at least in part on the distance estimated in D).

16. The method of claim 1 , wherein C) comprises detecting the photon using a Geiger-mode avalanche photodiode.

17. An apparatus for imaging a scene, the apparatus comprising:
a phased array to illuminate a portion of the scene with a time-varying optical intensity pattern generated from at least one continuous wave (CW) light beam so as to cause a photon to scatter or reflect from the portion of the scene;
at least one single-photon detector, in optical communication with the phased array, to detect the photon scattered or reflected by the portion of the scene; and
a processor, operably coupled to the at least one single-photon detector, to estimate a distance between the at least one single photon detector and the portion of the scene based on a time of flight of the photon.

18. The apparatus of claim 17 , wherein the time-varying optical intensity pattern comprises a time-varying interference pattern.

19. The apparatus of claim 17 , wherein the phased array is configured to sweep at least one bright portion of the time-varying optical intensity pattern a point in the portion of the scene within a dwell time substantially equal to or less than 5 ns.

20. The apparatus of claim 17 , wherein the phased array comprises a plurality of phase modulators to modulate respective portions of the at least one CW light beam so as to generate the time-varying optical intensity pattern.

21. The apparatus of claim 20 , wherein the plurality of phase modulators is configured to modulate the respective portions of the at least one CW light beam at a repetition rate substantially equal to or greater than 20 MHz.

22. The apparatus of claim 17 , further comprising:
a photodetector, in optical communication with the phased array, to measure an intensity of at least a portion of the time-varying optical intensity pattern; and
a controller, operably coupled to the first detector, to change a phase setting of the phased array based at least in part on the intensity measured by the first detector.

23. The apparatus of claim 17 , wherein the at least one single-photon detector comprises an array of Geiger-mode avalanche photodiodes.

24. An apparatus for imaging a scene, the apparatus comprising:
a transmitter to illuminate at least one portion of the scene with a spatiotemporally varying interference pattern, the transmitter comprising:
at least on

Assignees

• Massachusetts Inst Technology

Inventors

• Montoya Juan C
• Sanchez-Rubio Antonio
• Payson Harold C
• Hatch Robert E
• Heinrichs Richard
• Fried Dale G

Classifications

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title

• G01S7/499

  using polarisation effects · CPC title

• G01S7/4817

  relating to scanning · CPC title

• G01S7/4815

  using multiple transmitters · CPC title

• G01S17/32

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