Methods and apparatus for true high dynamic range imaging

Patent metadata

Field	Value
Publication number	US-10079984-B2
Application number	US-201715463590-A
Country	US
Kind code	B2
Filing date	Mar 20, 2017
Priority date	Jul 31, 2013
Publication date	Sep 18, 2018
Grant date	Sep 18, 2018

Abstract

When imaging bright objects, a conventional detector array can saturate, making it difficult to produce an image with a dynamic range that equals the scene's dynamic range. Conversely, a digital focal plane array (DFPA) with one or more m-bit counters can produce an image whose dynamic range is greater than the native dynamic range. In one example, the DFPA acquires a first image over a relatively brief integration period at a relatively low gain setting. The DFPA then acquires a second image over longer integration period and/or a higher gain setting. During this second integration period, counters may roll over, possibly several times, to capture a residue modulus 2 m of the number of counts (as opposed to the actual number of counts). A processor in or coupled to the DFPA generates a high-dynamic range image based on the first image and the residues modulus 2 m .

First claim

The invention claimed is:

1. A method of generating a motion-compensated representation of a scene with a detector element operably coupled to an m-bit counter, where m is a positive integer, the method comprising:
generating, in the m-bit counter, a first count representative of detections by the detector element during a first integration period;
generating, in the m-bit counter, a second count representative of detections by the detector element during a second integration period;
performing a comparison of the first count to the second count;
identifying motion in the scene based on the comparison of the first count to the second count; and
generating the motion-compensated representation of the scene based at least in part on the first count and the motion in the scene, the motion-compensated representation of the scene having a bit depth greater than m bits.

2. The method of claim 1 , wherein the first integration period is equal to the second integration period.

3. The method of claim 1 , wherein generating the motion-compensated representation of the scene comprises:
estimating a first flux incident on the detector element during the first integration period based at least in part on the first count; and
generating the motion-compensated representation of the scene based at least in part on the first flux.

4. The method of claim 1 , wherein generating the motion-compensated representation of the scene comprises generating the motion-compensated representation of the scene in real time.

5. The method of claim 1 , further comprising:
generating, in the m-bit counter, a third count representative of detections by the detector element during a third integration period longer than at least one of the first period or the second period.

6. The method of claim 5 , wherein generating the motion-compensated representation of the scene comprises shifting the third count based on the comparison of the first count to the second count.

7. The method of claim 5 , wherein generating the motion-compensated representation of the scene comprises scaling the third count based on the comparison of the first count to the second count.

8. The method of claim 5 , wherein generating the motion-compensated representation of the scene comprises concatenating a portion of the third count with a portion of the first count.

9. The method of claim 5 , further comprising:
estimating a noise level associated with the motion-compensated representation of the scene based on a comparison of a most significant bit of the first count to a corresponding bit in a residue modulo m of the third count.

10. A system for generating a motion-compensated representation of a scene, the system comprising:
a detector element to detect incident photons during a first integration period and during a second integration period;
an m-bit counter, operably coupled to the detector element, to generate a first count of representative of photons detected by the detector element during the first integration period and a second count representative of photons detected by the detector element during the second integration period, m being a positive integer; and
a processor, operably coupled to the m-bit counter, to perform a comparison of the first count to the second count, to identify motion in the scene based on the comparison of the first count to the second count, and to generate the motion-compensated representation of the scene based at least in part on the first count and the motion in the scene, the motion-compensated representation of the scene having a bit depth greater than m bits.

11. The system of claim 10 , wherein the first integration period is equal to the second integration period.

12. The system of claim 10 , wherein the processor is configured to:
estimate a first flux incident on the detector element during the first integration period based at least in part on the first count; and
generate the motion-compensated representation of the scene based at least in part on the first flux.

13. The system of claim 10 , wherein generating the motion-compensated representation of the scene comprises generating the motion-compensated representation of the scene in real time.

14. The system of claim 10 , wherein the detector element is configured to detect incident photons during a third integration period longer than the first integration period and the m-bit counter is configured to generate a third count representative of photons detected by the detector element during the third integration period.

15. The system of claim 14 , wherein the processor is configured to shift the third count based on the comparison of the first count to the second count.

16. The system of claim 14 , wherein the processor is configured to scale the third count based on the comparison of the first count to the second count.

17. The system of claim 14 , wherein the processor is configured to concatenate a portion of the third count with a portion of the first count.

18. The system of claim 14 , wherein the processor is configured to estimate a noise level associated with the motion-compensated representation of the scene based on a comparison of a most significant bit of the first count to a corresponding bit in a residue modulo m of the third count.

19. A method of generating a motion-compensated representation of a scene with a plurality of detector elements, each detector element in the plurality of detector elements operably coupled to a corresponding m-bit counter in a plurality of m-bit counters, where m is a positive integer, the method comprising:
generating, in a first m-bit counter in the plurality of m-bit counters, a first count representative of photons detected by a corresponding first detector element in the plurality of detector elements during a first integration period;
generating, in the first m-bit counter, a second count representative of photons detected by the corresponding first detector element during a second integration period longer than the first integration period;
generating, in the first m-bit counter, a third count, the first count representative of photons detected by the corresponding first detector element during a third integration period shorter than the second integration period;
performing a comparison of the first count to the third count to determine if motion was present in the scene during the second integration period; and
generating the motion-compensated representation of the scene based at least in part on the first count, the second count, the third count, and/or the comparison of the first count to the third count, the motion-compensated representation of the scene having a bit depth greater than m bits.

20. The method of claim 19 , wherein generating the motion-compensated representation of the scene comprises concatenating a portion of the second count with a portion of the first count.

Assignees

• Massachusetts Inst Technology

Inventors

• Kelly Michael W
• Blackwell Megan H
• Colonero Curtis B
• Wey James
• David Christopher
• Baker Justin
• Costa Joseph

Classifications

• H04N23/6811

  based on the image signal · CPC title

• H04N25/587

  acquired sequentially, e.g. using the combination of odd and even image fields · CPC title

• H04N23/741 Primary

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• H04N25/57

  Control of the dynamic range · CPC title

• H04N23/683

  performed by a processor, e.g. controlling the readout of an image memory · CPC title