Method and apparatus for providing enhanced resolution in photodetectors

• US 7,385,171 B2
• Filed: 05/09/2005
• Issued: 06/10/2008
• Est. Priority Date: 05/09/2005
• Status: Active Grant

• Current Assignee: Sensors Unlimited Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Sensors Unlimited Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: O'Grady, Matthew T.
• Primary Examiner(s): Monbleau; Davienne
• Assistant Examiner(s): LeGasse, Jr.; Francis M
• Application Number:
  US11/125,305
• Publication Number:
  US 20060249658A1
• Time in Patent Office: 1,128 Days
• Field of Search: 250/214.R, 250/214.1, 345/613, 345/614, 345/616, 382/194, 382/268, 348/294, 348/297, 348/298, 348/307, 348/311, 348/313, 257/218, 257/290
• US Class Current: 250/214.00R
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/40 Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled

Abstract

A method and apparatus for providing enhanced resolution in photodetector arrays is provided. In a first pass, pixels of a photodetector array are set to low input impedance values, and measurements of each pixel value are taken. In a second pass, selected pixels are set to high input impedance levels and remaining pixels set to low input impedance level, and measurements are taken at The low input impedance pixels. In a third pass, input impedance levels are reversed, and measurements are taken at the low input impedance pixels. A sequence of mathematical calculations are then performed on the measurements taken in the first, second, and third passes to produce half-pixel values for each of the pixels of the array, thereby doubling the resolution of the array without requiring additional circuitry or modification thereto.

Claims

1. A method for increasing resolution in a photodetector array comprising:

setting all pixels in the photodetector array to a low input impedance level;

measuring a first set of signals from the pixels in a first pass;

setting selected pixels in the photodetector array to a high input impedance level and remaining pixels to a low input impedance level;

measuring a second set of signals from low input impedance pixels in a second pass; and

calculating partial pixel values for pixels in the array using the first set of signals and the second set of signals, the partial pixel values corresponding to light received by portions of pixels of the array.

2. The method of claim 1, wherein the partial pixel values comprise half-pixel values corresponding to light received by half of a pixel area.

3. The method of claim 1, further comprising:

setting a second set of pixels in the photodetector array to a low input impedance level and remaining pixels to a high input impedance level;

measuring a third set of signals from low input impedance pixels in a third pass; and

calculating partial pixel values for remaining pixels in the array using the first set of signals and the third set of signals, the partial pixel values corresponding to light received by portions of the remaining pixels of the array.

4. The method of claim 3, wherein the partial pixel values comprise half-pixel values corresponding to light received by half of a pixel area.

5. The method of claim 1, wherein the step of setting selected pixels to a low input impedance level comprises setting alternating pixels in the array to high and low input impedance levels.

6. The method of claim 1, wherein the step of setting selected pixels to a low input impedance level comprises setting every third pixel in the array to a low input impedance level.

7. An apparatus for increasing resolution of a photodetector comprising:

a photodetector;

means for individually controlling the input impedance levels of pixels in the photodetector;

means for scanning detector areas within the photodetector; and

means for calculating partial pixel values using first and second outputs from the means for scanning detector areas generated by first and second measurement passes of the photodetector.

8. The apparatus of claim 7, wherein the photodetector comprises a charge coupled device (CCD) photodetector.

9. The apparatus of claim 7, wherein the photodetector comprises a focal plane array (FPA).

10. The apparatus of claim 7, wherein the photodetector comprises an active pixel sensor (APS).

11. The apparatus of claim 7, wherein the photodetector comprises a CMOS imager.

12. The apparatus of claim 7, wherein the means for individually controlling input impedance levels comprises a plurality of transistors connected to pixels of the photodetector array.

13. The apparatus of claim 7, wherein the means for individually controlling input impedance levels comprises a plurality of control signals delivered to pixels in the photodetector array.

14. The apparatus of claim 7, wherein the means for individually controlling input impedance levels sets all pixels in the array to a low input impedance level in a first pass.

15. The apparatus of claim 14, wherein the means for scanning detector areas scans outputs of each pixel in the array to produce a first set of signals.

16. The apparatus of claim 15, wherein the means for individually controlling input impedance levels sets selected pixels in the array to a low input impedance level and remaining pixels to a high input impedance level in a second pass.

17. The apparatus of claim 16, wherein the means for scanning the detector areas scans outputs from the selected pixels to produce a second set of signals.

18. The apparatus of claim 17, wherein the means for calculating partial pixel values subtracts the first set of signals from the second set of signals to produce the partial pixel values.

19. The apparatus of claim 18, wherein the means for individually controlling input impedance levels sets alternate pixels in the array to a low input impedance level and remaining pixels to a high input impedance level in a third pass.

20. The apparatus of claim 19, wherein the means for scanning the detector areas scans outputs from the alternate pixels to produce a third set of signals.

21. The apparatus of claim 20, wherein the means for calculating partial pixel values subtracts the first set of signals from the third set of signals to produce partial pixel values for remaining pixels in the array.