Systems and method of high resolution three-dimensional imaging

• US 10,218,962 B2
• Filed: 04/13/2015
• Issued: 02/26/2019
• Est. Priority Date: 11/25/2008
• Status: Active Grant

• Current Assignee: Nlight Inc.
• Original Assignee: Tetravue Inc.
• Inventors: Banks, Paul S.
• Primary Examiner(s): Williams, Jeffery A
• Application Number:
  US14/685,326
• Publication Number:
  US 20150296201A1
• Time in Patent Office: 1,415 Days
• Field of Search: 348 38, 348 46, 382284
• 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 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/484 Transmitters
• CPC Class Codes: G01S 7/486 Receivers
• 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: H04N 13/204 using stereoscopic image cameras stereoscopic photography G03B35/00
• CPC Class Codes: H04N 13/207 using a single 2D image sensor
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 13/296 Synchronisation thereof; Control thereof

Abstract

Embodiments of the invention provide systems and methods for three-dimensional imaging with wide field of view and precision timing. In accordance with one aspect, a three-dimensional imaging system includes an illumination subsystem configured to emit a light pulse with a divergence sufficient to irradiate a scene having a wide field of view. A sensor subsystem is configured to receive over a wide field of view portions of the light pulse reflected or scattered by the scene and including: a modulator configured to modulate as a function of time an intensity of the received light pulse portion to form modulated received light pulse portions; and means for generating a first image corresponding to the received light pulse portions and a second image corresponding to the modulated received light pulse portions. A processor subsystem is configured to obtain a three-dimensional image based on the first and second images.

Claims

1. A three-dimensional imaging system, comprising:

an illumination subsystem having a light source configured to emit a light pulse that does not pass through any modulator in the illumination subsystem and has a divergence sufficient to irradiate a scene;

a sensor subsystem comprising;

a receiving lens having a predetermined image plane and a predetermined pupil plane, the receiving lens configured to receive a portion of the light pulse reflected or scattered by the scene, whereby outputting a received light pulse portion having a duration;

a modulator, located along an optical axis of the sensor subsystem behind the receiving lens, configured to modulate as a function of time an intensity of the received light pulse portion to form a modulated received light pulse portion, wherein the modulator is not located in the image plane or pupil plane of the receiving lens;

a first imaging sensor array, in optical communication with the modulator, configured to generate a first image based on the modulated received light pulse portion; and

a second imaging sensor array, in optical communication with the modulator, configured to generate a second image based on the modulated received light pulse portion; and

a processor subsystem configured to obtain a three-dimensional image based on the first and second images.

2. The system of claim 1, wherein the illumination subsystem comprises a diffusing element configure to cause the light pulse to have a substantially uniform spatial profile.

3. The system of claim 1, wherein the illumination subsystem comprises one or more beam shaping elements through which the light pulse passes.

4. The system of claim 1, wherein the illumination subsystem comprises one or more optical elements configured to reduce the spatial coherence or temporal coherence of the light pulse.

5. The system of claim 1, wherein the sensor subsystem further includes one or more polarizing optical elements receiving the light pulse portions and having an acceptance angle greater than 10°

.

6. The system of claim 1, wherein the receiving lens has an aperture of 5 cm or less.

7. The system of claim 1, wherein the illumination subsystem comprises one or more pulsed semiconductor lasers or diode lasers.

8. The system of claim 1, wherein the first imaging sensor array and second imaging sensor array are registered with one another.

9. The system of claim 1, wherein the modulator comprises a Pockels cell.

10. The system of claim 1, wherein the processor subsystem comprises a controller configured to send a control signal to the modulator, the modulator configured to modulate the received light pulse portions monotonically as a function of time responsive to the control signal.

11. The system of claim 1, wherein the processor subsystem comprises a controller configured to send a control signal to the modulator, the modulator configured to modulate the received light pulse portions non-monotonically as a function of time responsive to the control signal.

12. The system of claim 1, wherein the first and second imaging sensor arrays are arbitrarily positioned relative to one another, each of the first and second imaging sensor arrays having a plurality of pixels;

wherein the processor subsystem includes an image constructor for registering the pixels of the first imaging sensor arrays with the pixel elements of the second imaging sensor arrays.

13. The system of claim 12, further comprising means for correcting two-dimensional image intensities of images captured by the image sensor arrays, based on calibration measurements.

14. The system of claim 1, wherein the modulator comprises an etalon.

15. The system of claim 1, wherein at least one of the first and second images contains a region of maximum intensity, wherein the means for generating comprises a sensor array having a saturation limit, and wherein the system is configured to enhance a dynamic range of the three-dimensional image by increasing an energy of the light pulse above the saturation limit of the sensor array.

16. The system of claim 1, wherein the processor subsystem is configured to:

instruct the illumination subsystem to emit a plurality of light pulses;

adjust a timing of the modulator such that modulation begins at a different time for each light pulse of the plurality of light pulses;

obtain a plurality of three-dimensional images, each of the images corresponding to a light pulse of the plurality of light pulses; and

obtain an enhanced three-dimensional image based on the plurality of three-dimensional images, the enhanced three-dimensional image corresponding to a larger distance window than a distance window of any of the plurality of three-dimensional images.

20. The system of claim 1, wherein the modulator comprises a plurality of Pockels cells, wherein at least one of the Pockels cells is oriented such that its axis is positioned 90°

with respect to one or more of the other Pockels cells.

21. The system of claim 1, wherein the modulator is configured to encode time of flight (TOF) information for the received light pulse portion as an intensity modulation on an FPA.

22. The system of claim 1, wherein the light source is a pulsed light source that emits the light pulse with a duration of 2 nS or less.

17. A method of three-dimensional imaging, comprising:

emitting a light pulse that does not pass through any modulator in an illumination subsystem and has a divergence sufficient to irradiate a scene;

receiving, at a receiving lens having a predetermined image plane and a predetermined pupil plane, a portion of the light pulse reflected or scattered by the scene, the receiving lens outputting a received light pulse portion;

modulating with a modulator, located behind the receiving lens, the intensity of the received light pulse portion as a function of time to form a modulated received light pulse portion, wherein the modulator is not located in the image plane or pupil plane of the receiving lens;

generating a first image at a first image sensor array based on the modulated received light pulse portion;

generating a second image at a second image sensor array based on the modulated received light pulse portion; and

obtaining a three-dimensional image of the scene based on the first and second images.

18. The method of claim 17, wherein generating the first image comprises adding the second image to a third image.

19. The method of claim 17, wherein the modulator is selected from the group consisting of a Pockels cell and an etalon.