High resolution 3-D imaging range finder

• US 6,535,275 B2
• Filed: 01/30/2001
• Issued: 03/18/2003
• Est. Priority Date: 08/09/2000
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Dialog Semiconductor GmbH (Renesas Electronics Corporation)
• Inventors: Levine, Peter Alan, Martinelli, Ramon Ubaldo, McCaffrey, Nathaniel Joseph, Andreas, Robert James
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/772,361
• Publication Number:
  US 20020036765A1
• Time in Patent Office: 777 Days
• Field of Search: 356/5-1-, 356/141.1
• US Class Current: 356/5.08
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• 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 7/4873 by deriving and controlling a threshold value

Abstract

A three-dimensional imaging range finder is disclosed using a transmitted pulse reflected from a target. The range finder includes a pixel sensor for receiving light from the target and the reflected pulse. A global counter is provided for determining a time-of-flight value of the transmitted pulse by providing accurate count data to pixel memories. A processing circuit, which is coupled to the pixel sensor and the global counter, extracts the reflected pulse received by the pixel sensor, and stores the time-of-flight value upon extracting the reflected pulse. The pixel sensor provides a luminance signal and the processing circuit includes a high pass filter to extract the reflected pulse from the luminance signal.

Claims

1. A range finder using a transmitted pulse reflected from a target comprising:

a pixel sensor for receiving light from the target, including the reflected pulse, the pixel sensor being implemented within a pixel;

a global counter implemented outside of the pixel for generating a time-of-flight value of the transmitted pulse; and

a processing circuit including a pixel memory implemented within the pixel and coupled to the pixel sensor and the global counter for (a) extracting the reflected pulse received by the pixel sensor and (b) storing the time-of-flight value provided by the global counter in the pixel memory, responsive to the extracted reflected pulse.

2. The range finder of claim 1, wherein the pixel sensor provides a luminance signal and the processing circuit includes a high pass filter to extract the reflected pulse from the luminance signal.

3. The range finder of claim 2, wherein the processing circuit includes a matched filter for providing a peak triangular return signal centered on the reflected pulse.

4. The range finder of claim 3, wherein the processing circuit includes a comparator for providing a write command, when the peak triangular return signal exceeds a predetermined threshold setting level;

and

a memory for storing the time-of-flight value, when the write command is provided to the memory.

5. The range finder of claim 1, wherein the pixel sensor is one of a plurality of pixel sensors arranged in a matrix array.

6. The range finder of claim 1, wherein the global counter includes a first counter for counting the time-of-flight of the transmitted pulse to reach a predetermined minimum range, and a second counter for counting the time-of-flight of the transmitted pulse from the predetermined minimum range to a predetermined maximum range;

and

the time-of-flight value is based on a range between the predetermined minimum range and the predetermined maximum range.

7. The range finder of claim 6, further including a lens system having a focus control wherein the predetermined minimum range is set by monitoring the focus control of the lens system.

8. The range finder of claim 4, wherein the predetermined threshold setting level is based on at least ambient light conditions of the target and power level of the transmitted pulse.

9. The range finder of claim 1, wherein the target is in a field-of-view of the pixel sensor, and the range finder further includes a large area diode coupled to a local counter, wherein the local counter counts time-of-flight of the transmitted pulse to an other target in the field-of-view, and the other target is closer in range to the large area diode than the range between the pixel sensor and the target, and

the range between the pixel sensor and the target is determined by adding the time-of-flight counted by the local counter and the time-of-flight counted by the global counter.

10. The range finder of claim 1, wherein the processing circuit provides the stored time-of-flight value to a processor for calculating a range between the pixel sensor and the target.

11. The range finder of claim 6, wherein the processing circuit includes a memory for storing the time-of-flight value, the memory having a bit-size based on the range between the predetermined minimum range and the predetermined maximum range.

12. The range finder of claim 11, wherein the second counter is an N-bit counter, and the memory included in the processing circuit is an N-bit memory.

13. The range finder of claim 6, wherein the processing circuit includes a memory for storing the time-of-flight value, the first counter having a first bit-size and the second counter having a second bit-size, the first bit-size being larger than the second bit-size, and the memory having a bit-size that is equal to the second bit-size.

14. A three-dimensional (3-D) imaging range finder using a transmitted pulse reflected from targets in a field-of-view comprising:

a plurality of pixel sensors in an imaging array, each pixel sensor being implemented within a respective pixel of the imaging array and receiving light, including the reflected pulse, from a respective target in the field-of-view,

a global counter separate from the pixel array for counting predetermined intervals of time starting at transmission time of the pulse to produce a count value; and

a plurality of processing circuits implemented within the respective plurality of pixels for extracting the reflected pulse from a respective pixel sensor and storing the count value provided by the global counter, after extracting the reflected pulse.

15. The 3-D imaging range finder of claim 14, wherein the global counter broadcasts the count of the predetermined intervals of time to each of the pixels in the imaging array.

16. The 3-D imaging range finder of claim 15, wherein a separate processing circuit is coupled between the global counter and each of the pixel sensors in the imaging array.

17. The 3-D imaging range finder of claim 14, wherein the processing circuit includes a memory for storing the value of the counted predetermined intervals of time, and output data lines for transmitting the value to a processor for calculating a range between the respective pixel sensor and the respective target.

18. The 3-D imaging range finder of claim 14, wherein the imaging array provides a two-dimensional image of the targets in the field-of-view and the processing circuit of each respective pixel sensor provides depth information of the respective target in the field-of-view.

19. In an imaging pixel array viewing objects in a field-of-view, a method of determining range to an object comprising the steps of:

(a) transmitting a pulse to the object;

(b) receiving ambient light from the object at a pixel of the pixel array;

(c) receiving a reflection of the pulse from the object at the pixel after transmitting the pulse in step (a);

(d) starting a time counter after transmitting the pulse in step (a);

(e) separating the pulse from the ambient light, in the pixel, after steps (b) and (c);

(f) receiving a count value from the started time counter of step (d); and

(g) storing the received count value in the pixel, on separating the pulse in step (e), as a measure of the range to the object.

20. The method of claim 19, wherein steps (c), (e) and (f) are performed by a respective pixel sensor of the imaging array viewing a respective object in the field of view.

21. The method of claim 20, wherein the respective pixel sensor determines the time interval of step (f) separately from any other respective pixel sensor in the imaging array.

22. The method of claim 19, further including the steps of:

(g) focusing the imaging array on an object in the field-of-view;

(h) determining a minimum time interval for the transmitted pulse to travel to and from the object; and

starting the time counter in step (d) after the minimum time interval determined in step (h).

23. The method of claim 19, wherein the receiving steps of (b) and (c) are performed by the same pixel sensor in the imaging array.