Imaging system having redundant pixel groupings

• US 6,756,576 B1
• Filed: 08/30/2000
• Issued: 06/29/2004
• Est. Priority Date: 08/30/2000
• Status: Expired due to Term

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: McElroy, David J., Cloud, Eugene H.
• Primary Examiner(s): Luu, Thanh X.
• Application Number:
  US09/650,551
• Time in Patent Office: 1,399 Days
• Field of Search: 250/208.1, 250/208.2, 250/214.A, 250/214.AG, 250/226, 348/246
• US Class Current: 250/208.1
• 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 25/68 applied to defects

Abstract

Imaging arrays are electronic devices that sense light and output electrical signals representative of the sensed light. An imaging array comprises thousands or millions of photodetectors that convert sensed light into corresponding electric signals, which are ultimately converted into digital image signals for recording or viewing. One problem with conventional imaging arrays concerns defective or malfunctioning photodetectors. Defective photodetectors typically result in erroneous image signals that ultimately degrade the quality of resulting images. Accordingly, the present inventors devised new imaging arrays including redundant photodetectors to compensate for defective photodetectors. One exemplary embodiment includes one or more photodetectors that are substantially smaller than conventional photodetectors, for example about 10 or 25 square microns. The smaller-than-conventional photodetectors are arranged into two or more groups, with each group having two or more photodetectors coupled to produce a single group image signal. If the group image signal for a group falls below some threshold level indicative of a defective or malfunctioning photodetector, the group image signal is amplified to compensate for the loss.

Claims

1. An imaging system comprising:

two or more group pixels comprising two or more photodetector circuits for providing two or more corresponding pixel image signals, with each photodetector circuit having a surface area less than 50 square microns and comprising;

a source-follower transistor have a gate, source, and drain;

a ground node; and

a photodiode coupled between the gate of the source-follower transistor and the ground node;

a summer responsive to two or more of the corresponding pixel image signals for outputting an aggregate image signal;

a variable-gain amplifier responsive to the aggregate image signal for outputting an amplified aggregate image signal based on an adjustable amplifier gain;

an automatic gain controller for adjusting the adjustable amplifier gain based on the aggregate image signal;

an address line; and

a signal line, with each photodetector circuit of one of the group pixels coupled to the address line and the signal line.

2. The imaging system of claim 1 wherein the summer comprises a digital summer.

3. The imaging system of claim 1 wherein the variable-gain amplifier is a digital amplifier.

4. The imaging system of claim 1, wherein each photodetector in the first group pixel is tuned to detect substantially the same color light.

5. The imaging system of claim 1, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a number of faulty photodetectors in the one of the group pixels.

6. The imaging system of claim 1, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a ratio of a total number of photodetectors in one of the group pixels to a total number of faulty photodetectors in the one of the group pixels.

7. An imaging system comprising:

a first group pixel comprising two or more photodetectors for providing two or more corresponding pixel image signals;

a second group pixel comprising two or more photodetectors for providing two or more corresponding pixel image signals;

a summer responsive to two or more of the corresponding pixel image signals for outputting an aggregate image signal;

a variable-gain amplifier responsive to the aggregate image signal for outputting an amplified aggregate image signal based on an adjustable amplifier gain;

an automatic gain controller for adjusting the adjustable amplifier gain based on the aggregate image signal;

an address line; and

a signal line, with each photodetector of the first group pixel coupled to the address line and the signal line, wherein each photodetector in the first group pixel is tuned to detect substantially the same color light.

8. The imaging system of claim 7 wherein the summer is digital.

9. The imaging system of claim 7 wherein the variable-gain amplifier is a digital amplifier.

10. The imaging system of claim 7, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a number of photodetectors in one of the group pixels and a number of faulty photodetectors in the one of the group pixels.

11. The imaging system of claim 7, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a ratio of a total number of photodetectors in one of the group pixels to a total number of faulty photodetectors in the one of the group pixels.

12. An imagine system comprising:

two or more group pixels each comprising photodetection means for providing two or more corresponding pixel image signals;

a summer responsive to two or more of the corresponding pixel image signals for outputting an aggregate image signal;

a variable-gain amplifier responsive to the aggregate image signal for outputting an amplified aggregate image signal based on an adjustable amplifier gain;

an automatic gain controller for adjusting the adjustable amplifier gain based on the amplified aggregate image signal;

an address line; and

a signal line, with each photodetection means of at least one of the group pixels coupled to the address line and the signal line and tuned to detect substantially the same color light.

13. The imaging system of claim 12 wherein the summer comprises a digital summer.

14. The imaging system of claim 12 wherein the variable-gain amplifier is a digital amplifier.

15. The imaging system of claim 12, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a number of photodetectors in one of the group pixels and a number of faulty photodetectors in the one of the group pixels.

16. The imaging system of claim 12, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a ratio of a total number of photodetectors in one of the group pixels to a total number of faulty photodetectors in the one of the group pixels.

17. An imaging system comprising:

a first group pixel comprising two or more photodetectors for providing two or more corresponding pixel image signals;

a second group pixel comprising two or more photodetectors for providing two or more corresponding pixel image signals;

a summer responsive to two or more of the corresponding pixel image signals for outputting an aggregate image signal;

a variable-gain amplifier responsive to the aggregate image signal for outputting an amplified aggregate image signal based on an adjustable amplifier pain;

an automatic gain controller for adjusting the adjustable amplifier gain based on the aggregate image signal;

an address line; and

a signal line, with each photodetector of the first group pixel coupled to the address line and the signal line,

wherein the summer is responsive to two or more of the corresponding pixel images signals from the first group pixel, and wherein the system further comprises;

another summer responsive to two or more of the corresponding pixel image signals from the second group pixel for outputting a second aggregate image signal;

another variable-gain amplifier responsive to the second aggregate image signal from the other summer for outputting another amplified aggregate image signal based on another adjustable amplifier gain; and

another automatic gain controller for adjusting the other adjustable amplifier gain based on the second amplified aggregate image signal.

18. The imaging system of claim 17 wherein the summer comprises a digital summer.

19. The imaging system of claim 17 wherein the variable-gain amplifier is a digital amplifier.

20. The imaging system of claim 17, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a number of photodetectors in one of the group pixels and a number of faulty photodetectors in the one of the group pixels.

21. The imaging system of claim 17, wherein the automatic gain controller adjusts the adjustable amplifier gain based on a ratio of a total number of photodetectors in one of the group pixels to a total number of faulty photodetectors in the one of the group pixels.