Compact economical lidar system

• US 7,830,442 B2
• Filed: 04/29/2003
• Issued: 11/09/2010
• Est. Priority Date: 04/30/2002
• Status: Active Grant

• Current Assignee: Arete Associates
• Original Assignee: Arete Associates
• Inventors: Redman, Brian, Fetzer, Gregory, Griffis, Andrew, Gelbart, Asher, Sitter, David
• Primary Examiner(s): SELBY, GEVELL V
• Application Number:
  US10/426,907
• Publication Number:
  US 20040119838A1
• Time in Patent Office: 2,751 Days
• Field of Search: 348/31, 348/231.99, 348/335, 348/340, 356/4.01, 356/5.01, 356/609
• US Class Current: 348/340
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/486 Receivers
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• 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

Abstract

A lidar pulse is time resolved in ways that avoid costly, fragile, bulky, high-voltage vacuum devices—and also costly, awkward optical remappers or pushbroom layouts—to provide preferably 3D volumetric imaging from a single pulse, or full-3D volumetric movies. Delay lines or programmed circuits generate time-resolution sweep signals, ideally digital. Preferably, discrete 2D photodiode and transimpedance-amplifier arrays replace a continuous 1D streak-tube cathode. For each pixel a memory-element array forms range bins. An intermediate optical buffer with low, well-controlled capacitance avoids corruption of input signal by these memories.

Claims

1. A lidar system comprising:

means for generating a measurement signal that is at least one-dimensional, corresponding to a received at-least-one-dimensional lidar-beam pulse;

means for time-resolving the measurement signal, said resolving means comprising;

multiple memory elements for receiving and holding successive portions of the measurement signal respectively,

digital means for forming a digital sweep signal defining multiple digital states corresponding to the respective memory elements, and

means for applying the digital sweep signal to control distribution of the successive measurement-signal portions into the respective memory elements;

wherein the forming means comprise a logic circuit generating a series of digital pointers addressing the memory elements respectively;

means for reading the measurement-signal portions from the memory elements; and

multiple buffer switches transferring the successive measurement-signal portions to the multiple memory elements respectively;

each buffer switch having a respective enable terminal actuated by a respective one of the digital pointers.

2. The system of claim 1, further comprising:

multiple electrooptical converters respectively receiving the successive measurement-signal portions from the buffer switches, respectively, and in response generating corresponding optical signals; and

multiple optoelectronic converters receiving the corresponding optical signals and in response generating new corresponding measurement-signal portions for application to the multiple memory elements.

3. The system of claim 2, wherein:

the electrooptical converters are selected from the group consisting of VCSELs, LEDs, and organic LEDs.

4. The system of claim 2, wherein:

the optoelectronic converters are selected from the group consisting of CMOS elements, organic phase-shift molecular devices, and a printed-circuit stack of thin-film devices.

5. A lidar system comprising:

means for generating a measurement signal that is at least one-dimensional, corresponding to a received at-least-one-dimensional lidar-beam pulse;

means for time-resolving the measurement signal, said resolving means comprising;

multiple memory elements for receiving and holding successive portions of the measurement signal respectively,

digital means for forming a digital sweep signal defining multiple digital states corresponding to the respective memory elements, and

means for applying the digital sweep signal to control distribution of the successive measurement-signal portions into the respective memory elements; and

means for reading the measurement-signal portions from the memory elements;

wherein;

the forming means comprise a tapped delay line having multiple taps addressing the multiple memory elements respectively.

6. The system of claim 5, wherein:

the memory elements comprise a dynamic RAM or other capacitive array receiving the measurement signal-portions substantially directly from the distribution controlled by the delay-line taps.

7. The system of claim 5, further comprising:

multiple buffer switches transferring the successive measurement-signal portions to the multiple memory elements respectively;

each buffer switch having a respective enable terminal actuated by a respective one of the delay-line taps.

8. The system of claim 7, further comprising:

multiple electrooptical converters respectively receiving the successive measurement-signal portions from the buffer switches, respectively, and in response generating corresponding optical signals; and

multiple optoelectronic converters receiving the corresponding optical signals and in response generating new corresponding measurement-signal portions for application to the multiple memory elements.

9. The system of claim 8, wherein:

the electrooptical converters are selected from the group consisting of VCSELs, LEDs, and organic LEDs.

10. The system of claim 8, wherein:

the optoelectronic converters are selected from the group consisting of CMOS elements, organic phase-shift molecular devices, and a printed-circuit stack of thin-film devices.

11. A lidar system comprising:

means for generating a measurement signal that is at least one-dimensional, corresponding to a received at-least-one-dimensional lidar-beam pulse;

means for time-resolving the measurement signal, said resolving means comprising;

multiple memory elements for receiving and holding successive portions of the measurement signal respectively,

digital means for forming a digital sweep signal defining multiple digital states corresponding to the respective memory elements, and

means for applying the digital sweep signal to control distribution of the successive measurement-signal portions into the respective memory elements; and

means for reading the measurement-signal portions from the memory elements;

wherein;

the forming means comprise a delay line that comprises the memory elements;

the delay line itself has clock signals serving as the digital sweep signal; and

the delay line responds to the clock signals by successively advancing the received successive measurement-signal portions into the delay line.

12. The system of claim 11, wherein:

the memory elements comprise a dynamic RAM or other capacitive array receiving the measurement signal-portions substantially directly from the distribution controlled by the clock signals.

13. The system of claim 11, wherein:

the delay line is a shift register;

the memory elements are successive positions in the shift register itself; and

the reading means comprise parallel circuits for reading plural measurement-signal portions substantially simultaneously from the shift register.

14. The system of claim 11, further comprising:

an analog-to-digital converter, digitizing the successive measurement-signal portions for application to the delay line.

15. A lidar system comprising:

means for generating a measurement signal corresponding to a received lidar-beam pulse;

means for time-resolving the measurement signal;

multiple electrooptical converters respectively receiving time-resolved measurement-signal portions from the resolving means, and in response forming new corresponding optical signals; and

means for reading the measurement-signal portions as the new corresponding optical signals from the electrooptical converters.

16. The system of claim 15, wherein:

the electrooptical converters are LEDs.

17. The system of claim 15, wherein:

the electrooptical converters are organic LEDs.

18. The system of claim 15, wherein:

the electrooptical converters are VCSELs.

19. The system of claim 18, further comprising:

multiple optoelectronic converters receiving the corresponding new optical signals from the VCSELs and in response forming new corresponding measurement-signal portions for readout by the reading means.

20. The system of claim 19, wherein:

the optoelectronic converters are CMOS elements.

21. The system of claim 19, wherein:

the optoelectronic converters are optical phase-shift molecules.

22. The system of claim 19, wherein:

the optoelectronic converters are printed-circuit stacks of thin-film devices.

23. The system of claim 15, further comprising:

multiple optoelectronic converters receiving the new corresponding optical signals and in response forming new corresponding measurement-signal portions for readout by the reading means.

24. The system of claim 23, wherein:

the optoelectronic converters are CMOS elements.

25. The system of claim 15, wherein:

the resolving means comprise multiple buffer switches directing the time-resolved measurement-signal portions to the multiple electrooptical converters, respectively;

the multiple buffer switches comprise respective enable terminals actuated by a synchronous enable signal.

26. The system of claim 25, wherein:

the synchronous enable signal is substantially in controlled-delay synchronism with the lidar-beam pulse.

27. The system of claim 25, wherein:

before said synchronous enable signal, each enable terminal is connected to receive a bias input that holds the respective electrooptical converter just within a quiescent state.

28. The system of claim 27, wherein:

readout from the respective electrooptical converter is terminated by another synchronous signal after a time interval allowing for collection of the time-resolved measurement-signal portion from that respective electrooptical converter.

29. The system of claim 15, for detecting and ranging objects;

said system further comprising;

means for projecting an at-least-one-dimensional light pulse toward such objects; and

means for receiving an at-least-one-dimensional reflected light pulse from such objects;

wherein the generating means comprise means for generating said measurement signal in response to the received light pulse.

30. A lidar system comprising:

means for generating an at-least-one-dimensional measurement signal corresponding to an at-least-one-dimensional received lidar-beam pulse;

means for time-resolving the measurement signal;

multiple memory elements, comprising a dynamic RAM or other capacitive array, respectively receiving and holding time-resolved measurement-signal portions substantially directly from the resolving means; and

means for reading the held measurement-signal portions from the memory elements; and

multiple buffer switches transferring the time-resolved measurement-signal portions from the resolving means substantially directly to the multiple memory elements respectively;

each buffer switch having a respective enable terminal actuated by the resolving means.

31. The system of claim 30, for detecting and ranging objects;

said system further comprising;

means for projecting an at-least-one-dimensional light pulse toward such objects; and

means for receiving an at-least-one-dimensional reflected light pulse from such objects;

wherein the generating means comprise means for generating said measurement signal in response to the received light pulse.