Redundant imaging systems

• US 7,129,457 B2
• Filed: 06/15/2004
• Issued: 10/31/2006
• 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:
  US10/868,131
• Publication Number:
  US 20040222355A1
• Time in Patent Office: 868 Days
• Field of Search: 250/208.1, 250/214.A, 348/246, 348/247, 348/229.1, 348/230.1
• 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 typically include 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 faulty photodetectors, which produce 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 faulty ones. One exemplary embodiment includes photodetectors that are substantially smaller than conventional photodetectors and that are arranged into two or more groups, with the photodetectors in each group 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:

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

a summer coupled to each of the two or more photodetectors for outputting an aggregate image signal based on the two or more corresponding pixel image signals;

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

an automatic gain controller for adjusting the gain based on the aggregate image signal and a reference signal, wherein a difference between the aggregate image signal and the reference signal represents that the group pixel contains at least one faulty pixel.

2. The imaging system of claim 1 wherein the summer comprises an analog-to-digital converter.

3. The imaging system of claim 1, further comprising an address line and a signal line, with each photodetector coupled to the address line and the signal line.

4. The imaging system of claim 1, wherein each photodetector is adapted to detect one of red, green, and blue light.

5. The imaging system of claim 1, wherein the gain is based on a ratio of a total number of photodetectors in the group pixel to a total number of faulty photodetectors in the group pixel.

6. An imaging system comprising:

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

a summer coupled to each of the two or more photodetector circuits for outputting an aggregate image signal based on the two or more corresponding pixel image signals;

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

an automatic gain controller for adjusting the gain based on the aggregate image signal, with the gain determined by comparing the amplified aggregate image signal to a reference signal the comparison representing that the group pixel contains at least one faulty pixel.

7. The imaging system of claim 6 wherein the summer comprises an analog-to-digital converter.

8. The imaging system of claim 6, further comprising an address line and a signal line, with each photodetector of the group pixel coupled to the address line and the signal line.

9. The imaging system of claim 6, wherein each photodetector is adapted to detect one of red, green, and blue light.

10. An imaging system comprising:

a group pixel comprising two or more photodetector circuits for providing two or more corresponding pixel image signals, wherein each photodetector circuit has a surface area less than 50 square microns, is adapted to detect the same color of light, and comprises;

a source-follower transistor having 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 coupled to each of the two or more photodetector circuits for outputting an aggregate image signal based on the two or more corresponding pixel image signals;

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

an automatic gain controller for adjusting the gain based on the aggregate image signal, with the gain determined by comparing the amplified aggregate image signal to a reference signal the comparison representing that the group pixel contains at least one faulty pixel.

11. The imaging system of claim 10, wherein the gain is based on a ratio of a total number of photodetector circuits in the group pixel to a total number of faulty photodetector circuits in the group pixels.

12. The imaging system of claim 10 wherein the summer comprises an analog-to-digital converter.

13. The imaging system of claim 10, further comprising an address line and a signal line, with each photodetector circuit of the group pixel coupled to the address line and the signal line.