Full-field light detection and ranging imaging system

• US 7,746,450 B2
• Filed: 08/28/2007
• Issued: 06/29/2010
• Est. Priority Date: 08/28/2007
• Status: Active Grant

• Current Assignee: Science Applications International Corporation
• Original Assignee: Science Applications International Corporation
• Inventors: Willner, Christopher Allen, McDowell, James
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Ratcliffe; Luke D
• Application Number:
  US11/845,858
• Publication Number:
  US 20090059201A1
• Time in Patent Office: 1,036 Days
• Field of Search: 356 301- 285, 35613901-1391
• US Class Current: 356/28
• CPC Class Codes: G01S 17/32 using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• 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 7/491 Details of non-pulse systems
• CPC Class Codes: G01S 7/4917 superposing optical signals in a photodetector, e.g. optical heterodyne detection

Abstract

Apparatuses and methods determine positional information from a reflected optical signal for an object on a per pixel basis. A spread spectrum imaging system includes a transmitting module transmitting a transmitted optical signal that illuminates a target space and contains a transmitted pulse that is modulated with a first pseudo-noise (PN) code. The imaging system includes a receiving module that receives a reflected optical signal from an object. The reflected signal is processed by an optical array that detects a detected signal from the reflected optical signal, where the detected signal contains a plurality of pixels spanning a target space. When the determined PN code corresponds to the selected PN code, image information and the positional information is presented for the object. When different positional information is obtained for different pixels in the image, the imaging system may determine that different objects appear in the received image.

Claims

1. An imaging system, comprising:

a transmitting module configured to transmit a transmitted optical signal containing a transmitted pulse, the transmitted pulse being modulated with a selected pseudo-noise (PN) code, the transmitted optical signal arranged to illuminate a target space containing a first object, wherein the transmitting module is configured to include identification information in addition to the selected PN code, the identification information is contained in the transmitted optical signal, the identification information comprises a plurality of bits that represent a source identification of the selected PN code, and the source identification comprises a vehicle identification;

a receiving module configured to receive a reflected optical signal reflected from the first object and to derive a first received pulse from the reflected optical signal;

an optical array configured to detect a detected signal from the reflected optical signal across a plurality of pixels of the optical array, the detected signal spanning the target space, a first pixel being contained in the plurality of pixels; and

a processing module configured to process data for the plurality of pixels by;

determining first pulse characteristics of the first received pulse;

obtaining first positional information for the first object from the first pulse characteristics;

when the selected PN code is detected from the first pixel, providing first image information and the first positional information for the first object; and

discarding second pixel data for a second pixel when a PN code associated with the second pixel is different from the selected PN code, wherein the PN code associated with the second pixel is generated by a source that is different from the transmitting module that is associated with the selected PN code.

2. The imaging system of claim 1, the processing module further configured to obtain the first positional information by determining a first velocity estimate of the first object only from the first pulse characteristics.

3. The imaging system of claim 1, the processing module further configured to process the second pixel data for the second pixel by:

determining second pulse characteristics of a second received pulse for the second pixel, the second received pulse being derived from the reflected optical signal;

obtaining second positional information for a second object from the second pulse characteristics, the second positional information being sufficiently different from the first positional information, the target space containing the second object; and

when the selected PN code is detected from the second pixel, providing second image information and the second positional information for the second object.

4. The imaging system of claim 3, the processing module further configured to provide an indication that distinguishes the first object from the second object.

5. The imaging system of claim 3, the processing module further configured to obtain the second positional information by determining a second range estimate and a second velocity estimate of the second object from the second pulse characteristics.

6. The imaging system of claim 1, the processing module further configured to process the second pixel data for the second pixel by:

determining second pulse characteristics of a second received pulse, the second received pulse being derived from the reflected optical signal;

obtaining second positional information for the first object from the second pulse characteristics, the second positional information being essentially equal to the first positional information; and

when the selected PN code is detected from the second pixel, providing second image information for the first object.

7. The imaging system of claim 6, the processing module further configured to process the data by:

determining combined positional information from the first positional information and the second positional information; and

providing the second image information with the combined positional information.

8. The imaging system of claim 7, wherein the processing module is configured to average the first and second positional information to obtain the combined positional information.

9. The imaging system of claim 1, the processing module further configured to process the data for the plurality of pixels by:

correlating the first pulse characteristics of the first received pulse and the transmitted pulse to obtain a time delay and a pulse width of the received pulse; and

processing the reflected optical signal in accordance with the time delay and the pulse width.

10. The imaging system of claim 1, the optical array comprising a charge-coupled device (CCD) array.

11. The imaging system of claim 1, the optical array comprising a complementary metal-oxide semiconductor (CMOS) array.

12. The imaging system of claim 1, the transmitting module comprising a frequency hopping spread spectrum modulator.

13. The imaging system of claim 1, the transmitting module comprising a direct sequence spread spectrum (DSSS) modulator.

14. The imaging system of claim 1, the transmitting module comprising a time hopping spread spectrum modulator.

15. The imaging system of claim 1, the optical array configured to heterodyne an optical reference signal with the reflected optical signal.

16. The imaging system of claim 15, the transmitting module comprising an optical extractor extracting a portion of the transmitted optical signal to provide the optical reference signal.

17. The imaging system of claim 1, wherein the processing module is configured to discard third pixel data for a third pixel when received identification information in the third pixel data is different from the identification information.

18. The imaging system of claim 17, wherein a third pixel PN code associated with the third pixel equals the selected PN code.

19. The imaging system of claim 1, the processing module further configured to obtain the first positional information by determining a first range estimate of the first object from the first pulse characteristics.

20. A method for forming an image of a target space, comprising:

transmitting an optical signal that illuminates the target space and contains a transmitted pulse modulated with a selected pseudo-noise (PN) code, the target space containing a first object;

receiving a reflected optical signal reflected from the first object and deriving a first received pulse from the reflected optical;

detecting a detected signal from the reflected optical signal across a plurality of pixels of an input optical array, the detected signal spanning the target space, a first pixel being contained in the plurality of pixels; and

processing data for the plurality of pixels by;

determining first pulse characteristics of the first received pulse;

obtaining first positional information for the first object from the first pulse characteristics; and

when the selected PN code is detected from the first pixel, providing first image information and the first positional information for the first object;

discarding second pixel data for a second pixel when a PN code associated with the second pixel is different from the selected PN code, wherein the PN code associated with the second pixel is generated by a source that is different from a transmitting module that is associated with the selected PN code; and

discarding third pixel data for a third pixel when received identification information is different from the identification information and a third pixel PN code associated with the third pixel matches the selected PN code, wherein the identification information is contained in the transmitted optical signal and comprises a plurality of bits that represent a source identification of the selected PN code.

21. The method of claim 20, wherein the obtaining the first positional information comprises:

determining a first range estimate and a velocity estimate of the first object only from the first pulse characteristics.

22. The method of claim 20, further comprising:

processing the second pixel data for the second pixel by;

determining second pulse characteristics of a second received pulse, the second received pulse being derived from the reflected optical signal;

obtaining second positional information for a second object from the second pulse characteristics, the second positional information being sufficiently different from the first positional information, the target space containing the second object; and

when the selected PN code is detected from the second pixel, providing second image information and the second positional information for the second object.

23. The method of claim 22, further comprising:

providing an indication that distinguishes the first object from the second object.

24. The method of claim 22, wherein the obtaining the second positional information comprises further comprising:

determining a second range estimate and a second velocity estimate of the second object from the second pulse characteristics.

25. The method of claim 20, further comprising:

processing the second pixel data for the second pixel by;

determining second pulse characteristics of a second received pulse, the second received pulse being derived from the reflected optical signal;

obtaining second positional information for the first object from the second pulse characteristics, the second positional information being essentially equal to the first positional information; and

when the selected PN code is detected from the second pixel, providing second image information for the first object.

26. The method of claim 25, further comprising:

determining combined positional information from the first positional information and the second positional information; and

providing the second image information with the combined positional information.

27. The method of claim 20, wherein the processing further comprises:

correlating the first pulse characteristics of the first received pulse and the transmitted pulse to obtain a time delay and a pulse width of the received pulse; and

processing the reflected optical signal in accordance with the time delay and the pulse width.

28. The method of claim 20, further comprising:

repeating the transmitting, the receiving, the detecting, and the processing for another pixel from the plurality of pixels.

29. The method of claim 28, further comprising:

presenting an image with the plurality of pixels, each pixel being associated with corresponding positional information.

30. The method of claim 20, further comprising:

bypassing the processing and routing the detected signal to an optical display when activating night vision operation.

31. An imaging system, comprising:

a transmitting module configured to transmit a transmitted optical signal containing a transmitted pulse modulated with a selected pseudo-noise (PN) code using a direct sequence spread spectrum (DSSS) technique, the transmitted optical signal illuminating a target space containing an object;

a receiving module configured to receive a reflected optical signal reflected from the object and deriving a received pulse from the reflected optical signal;

an optical array configured to detect a detected signal from the reflected optical signal across a plurality of pixels of the optical array, the detected signal spanning the target space, a processed pixel being contained in the plurality of pixels; and

a processing module configured to process data for the processed pixel by;

determining pulse characteristics of the received pulse;

correlating the pulse characteristics of the received pulse and the transmitted pulse to obtain a time delay and a pulse width of the received pulse;

processing the reflected optical signal in accordance with the time delay and the pulse width to obtain a range estimate and a velocity estimate for the object;

when the selected PN code is detected from the processed pixel, providing image

information and the range estimate and the velocity estimate for the object;

when an associated PN code from the processed pixel is different from the selected PN code, discarding the image information, wherein the associated PN code is generated by a source that is different from the transmitting module that is associated with the selected PN code; and

discarding third pixel data for a third pixel when received identification information is different from the identification information and a third pixel PN code associated with the third pixel matches the selected PN code, wherein the identification information is contained in the transmitted optical signal and comprises a plurality of bits that represent a source identification of the selected PN code.