3D imaging underwater laser radar

• US 5,446,529 A
• Filed: 02/09/1993
• Issued: 08/29/1995
• Est. Priority Date: 03/23/1992
• Status: Expired due to Term

• Current Assignee: Continental Autonomous Mobility US LLC (Continental AG)
• Original Assignee: Advanced Scientific Concepts, Inc.
• Inventors: Bailey, Howard W., Stettner, Roger
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US08/015,627
• Time in Patent Office: 931 Days
• Field of Search: 356/4, 356/5, 250/332, 250/330, 250/339
• US Class Current: 356/4.01
• 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 7/4863 Detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01T 1/28 with secondary-emission detectors

Abstract

A three dimensional imaging device and method is presented which uses a pulsed light source for detecting objects enveloped by a light-transmitting and light-reflecting and scattering medium such as water or biological tissues. By means of high-speed switching between many storage capacitors the third dimension is recorded by the device with a single pulse from the light-source. The device consists of the pulsed light source, optics for collecting the reflected and scattered light, one or more sensors for detecting the light, drive and output electronics for timing and signal conditioning of data generated by the sensors and processing electronics and software for converting the sensor data to a three dimensional image. The sensors use known technologies for light amplification but collect and process the light-amplified data in a unique manner, using an analog-processing readout chip. The readout chip is a two dimensional array of collectors or detectors combined in very close proximity with associated storage and switching electronics. The two dimensional array defines two dimensions of the image. The third dimension is associated with the time of return of the light pulse.

Claims

1. A device for imaging sections of a three dimensional object immersed in a light conducting medium comprising

a pulsed light source,

means for transmitting light from said pulsed light source into said medium,

optics for collecting light from said medium during a sequence of time intervals between the transmission of successive pulses from said light source,

sensor means for detecting said collected light, said sensor means comprising

means for amplification of said collected light and for providing an electrical signal corresponding to said amplified light,

an analog-processing readout chip comprising

a plurality of unit cell means each comprising a plurality of storage means for receiving electrical signals from said amplification means during said time intervals, and

readout electronics adapted to provide signals to output electronics from said storage means,

drive electronics for providing voltages and for providing timing for said readout electronics, and

output electronics for converting the signals stored on said storage means from analogue to digital signals.

2. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein each of said storage means is a capacitor.

3. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said means for amplification comprises a microchannel plate.

4. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said means for amplification comprises a digicon.

5. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said sensor means comprises PIN diodes.

6. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 5, wherein said PIN diodes are each electrically connected to said readout electronics on said analog-processing readout chip by metal bumps.

7. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said sensor means comprises anodes.

8. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said readout electronics comprises a shift register adapted to sequence between a plurality of said storage means.

9. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said readout electronics is adapted for direct readout with a source follower for each unit cell.

10. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said analog-processing readout chip comprises a current driver adapted to drive the data signals off the chip.

11. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said analog-processing readout chip is adapted to complete a processing cycle during an integration time interval less than about 20 ns.

12. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said analog-processing readout chip is adapted to reset in a time interval less than 10 ns.

13. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said analog processing readout chip comprises a delta reset circuit for enhanced signal to noise ratio.

14. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said analog-processing readout chip comprises bulk silicon CMOS components.

15. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said analog-processing readout chip comprises silicon on sapphire CMOS components.

33. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said sensor means is a plurality of sensors optically connected by optic fibers to the focal plane of said optics.

35. The device for imaging sections of a three dimensional object immersed in a light conducting medium of claim 1 wherein said sensor means is a plurality of sensors have differing optical paths, wherein depth resolution is increased.

16. A sensor for detecting the presence of light comprising

a means for amplification of light,

an analog-processing readout chip comprising

a two dimensional array of unit cells, each unit cell comprising a plurality of means for collecting or detecting signal data from said amplification means and

readout electronics comprising

a plurality of storage means, each associated with a distinct reflected light return time interval, and

means for sequentially switching said collecting or detecting means to said storage means.

17. The sensor for detecting the presence of light of claim 16 wherein each of said storage means is a capacitor.

18. The sensor for detecting the presence of light of claim 16 wherein drive and output electronics is adapted to read out said signal data in digitized form in real time between pulses from said light source.

19. The sensor for detecting the presence of light of claim 16 wherein said amplification means comprises a microchannel plate.

20. The sensor for detecting the presence of light of claim 16 wherein said amplification means operates by electron impact on the collection and detection means.

21. The sensor for detecting the presence of light of claim 16 wherein said amplification means comprises a Digicon.

22. The sensor for detecting the presence of light of claim 16 wherein said collecting or detecting means comprises anodes.

23. The sensor for detecting the presence of light of claim 16 wherein said collecting or detecting means comprises PIN diodes.

24. The sensor for detecting the presence of light of claim 16 wherein said analog processing readout chip comprises a delta reset circuit for enhanced signal to noise ratio.

25. The sensor for detecting the presence of light of claim 16 wherein said collecting or detecting means comprises an array of PIN diodes which are electrically and individually connected to said readout electronics on said analog-processing readout chip by metal bumps, to form a hybrid.

26. The sensor for detecting the presence of light of claim 16 wherein said readout electronics incorporates a shift register to sequence between said storage capacitors.

27. The sensor for detecting the presence of light of claim 16 wherein said readout electronics uses the direct readout approach with a source follower for each unit cell.

28. The sensor for detecting the presence of light of claim 16 wherein said analog-processing readout chip uses a current driver to drive the data signals off the chip.

29. The sensor for detecting the presence of light of claim 16 wherein said analog-processing readout chip uses an integration time interval less than 20 ns.

30. The sensor for detecting the presence of light of claim 16 wherein said analog-processing readout chip uses a reset time less than about 10 ns.

31. The sensor for detecting the presence of light of claim 16 wherein said analog-processing readout chip uses bulk silicon CMOS processing.

32. The sensor for detecting the presence of light of claim 16 wherein said analog-processing readout chip uses silicon on sapphire CMOS processing.

34. The sensor of claim 16 wherein said sensor is comprised of a plurality of sensors optically connected by optic fibers to an optical focal plane.

36. The sensor for detecting the presence of light of claim 16 wherein said sensor is a plurality of sensors of differing optical paths wherein depth resolution is increased.

37. A method for for imaging sections of a three dimensional object immersed in a light conducting medium comprising the steps of

generating a series of pulses of light,

transmitting said pulses of light into said medium,

collecting light from said medium during a sequence of time intervals between the transmission of successive pulses from said light source,

detecting said collected light,

providing an electrical signal corresponding to said amplified light,

sequentially storing said electrical signal on a separate plurality of unit cells during each of said time intervals,

providing signals from said storage means,

converting the signals stored on said storage means from analogue to digital signals.

38. The method for imaging sections of an object of claim 37 further comprising the steps of increasing depth resolution by physically changing the optical path length between the light-source transmitter, transmission medium or object, and receiver in the time between light source pulses.

39. The method for imaging sections of an object of claim 37 wherein depth resolution is increased by electronically changing the relative timing between initiation of a laser pulse and said time interval or storage capacitor reset time or switching time, between laser pulses.

40. The method for imaging sections of an object of claim 37 wherein depth resolution is increased by multiple sensors positioned so the difference in their optical path length corresponds to the depth resolution, for integration times and laser pulse lengths which normally correspond to poorer depth resolution.