Imaging device with improved signal to noise performance

• US 20080049129A1
• Filed: 08/28/2006
• Published: 02/28/2008
• Est. Priority Date: 08/28/2006
• Status: Abandoned Application

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Inventors: Meacham, James H.
• Application Number:
  US11/510,696
• Publication Number:
  US 20080049129A1
• Time in Patent Office: Days
• US Class Current: 348/297
• CPC Class Codes: H04N 25/533 by using differing integration times for different sensor regions

Abstract

A variable integration circuit processes an image based on variable pixel integration times. The variable integration circuit includes a threshold detect circuit that detects whether a threshold charge level has been reached at a pixel output. If the threshold charge has been reached at the pixel output, the threshold detect circuit generates a trigger indicating that the threshold charge has been reached. The trigger resets the pixel output. The variable integration circuit also includes a threshold detect time store circuit that receives the trigger and stores a time-to-threshold. The trigger resets the pixel output to an initial state.

Claims

1. An imaging device for generating an image based on variable pixel integration times, comprising:

a plurality of pixels, wherein each pixel of the plurality of pixels senses light and generates an amount of charge proportionate to sensed light; and

means for comparing coupled to each pixel of the plurality of pixels, wherein the means for comparing compares the generated amount of charge, proportionate to the sensed light associated with each pixel, to a threshold charge level, and if the means for comparing determines that the generated amount of charge is equal to or greater than the threshold charge level, then the means for comparing generates a trigger indicating that the threshold charge level has been reached at the associated pixel.

2. The imaging device of claim 1, further comprising:

an amplifier, wherein the amplifier is coupled between each pixel and the means for comparing.

3. The imaging device of claim 1, wherein the trigger generated by the means for comparing resets the associated pixel to an initial state.

4. The imaging device of claim 1, further comprising:

means for detecting, wherein the means for detecting receives the trigger for the associated pixel and determines a time-to-threshold for the associated pixel.

5. The imaging device of claim 4, further comprising:

a time reference stream provided to the means for detecting.

6. The imaging device of claim 4, wherein the means for detecting determines a location of the associated pixel, and outputs the location of the associated pixel and the time-to-threshold for the associated pixel.

7. The imaging device of claim 6, further comprising:

an image processor, wherein the image processor processes data including the location of the associated pixel and the time-to-threshold for the associated pixel to generate the image.

8. The imaging device of claim 7, wherein the image processor further comprises:

a scan converter, wherein the scan converter receives the location of the associated pixel and the time-to-threshold for at least a portion of the plurality of pixels, and generates an output stream representing the image at a standard scan rate.

9. The imaging device of claim 7, wherein the image processor further comprises:

a time reference generator, wherein the time reference generator generating the time reference stream.

11. The imaging device of claim 1, wherein the threshold detect circuit is coupled to each of the plurality of pixels.

12. The imaging device of claim 1, further comprising:

an amplifier, wherein the amplifier is coupled between each pixel and the threshold detect circuit.

13. The imaging device of claim 1, further comprising:

a threshold detect time store circuit receives the trigger and stores a time when the trigger was detected.

14. The imaging device of claim 1, wherein the trigger resets the pixel to regenerate charge based on sensed light.

10. An imaging device comprising:

a plurality of pixels, wherein each pixel of the plurality of pixels senses light and generates an amount of charge proportionate to sensed light;

a threshold detect circuit, wherein the threshold detect circuit detects whether a threshold charge level has been reached at each pixel of the plurality of pixels, and if the threshold charge has been reached at the corresponding pixel being detected, the threshold detect circuit generates a trigger indicating that the threshold charge has been reached.

15. A method or generating an image based on variable pixel integration times, the method comprising:

determining whether a first charge generated by a pixel based on sensed light is greater than or equal to a predetermined threshold;

if the first charge generated by the pixel is greater than or equal to the predetermined threshold, generating a first trigger; and

calculating a first time for the generation of the first trigger.

16. The method of claim 15, further comprising:

resetting the pixel to an initial state using the first trigger.

17. The method of claim 15, further comprising:

determining a location of the pixel; and

transmitting the first time and the determined location of the pixel to an image processor.

18. The method of claim 17, further comprising:

processing the first time and the determined location of the pixel to generate the image.

19. The method of 16, further comprising:

determining whether a second charge generated by the pixel, after reset, based on sensed light is greater than or equal to the predetermined threshold;

if the second charge generated by the pixel is greater than or equal to the predetermined threshold, generating a second trigger; and

calculating a second time for the generation of the second trigger.

20. The method of claim 19, further comprising:

resetting the pixel to an initial state using the second trigger.

21. The method of claim 19, further comprising:

determining a location of the pixel; and

transmitting the second time and the determined location of the pixel to an image processor.

22. A variable pixel integration circuit comprising:

a threshold detect circuit, wherein the threshold detect circuit detects whether a threshold charge level has been reached at a pixel output, and if the threshold charge has been reached at the pixel output, the threshold detect circuit generates a trigger indicating that the threshold charge has been reached and the trigger resets the pixel output.

23. The variable pixel integration circuit of claim 22, wherein the threshold detect circuit is coupled to each of a plurality of pixels.

24. The variable pixel integration circuit of claim 22, further comprising:

an amplifier, wherein the amplifier is coupled between a pixel and the threshold detect circuit.

25. The variable pixel integration circuit of claim 22, further comprising:

a threshold detect time store circuit that receives the trigger and stores a time-to-threshold.

26. The variable pixel integration circuit of claim 22, wherein the trigger resets the pixel output to an initial state.

27. A processor implemented method for generating an image, comprising:

collecting time-to-threshold values associated with each pixel of a plurality of pixels in an array;

processing the collected time-to-threshold values to generate pixel illumination levels associated with each pixel;

generating an output image based on the generated pixel illumination levels associated with each pixel.

28. A variable pixel integration circuit comprising:

a threshold detect circuit;

a trigger indicating that a threshold charge level at a pixel output has been reached, wherein the trigger resets the pixel output charge if the threshold charge level at the pixel output has been reached.

29. The variable pixel integration circuit of claim 28, further comprising:

a threshold detect time store circuit that receives the trigger and stores a time-to-threshold.

30. The variable pixel integration circuit of claim 28, wherein the trigger resets the pixel output to an initial state.