Wide dynamic range pinned photodiode active pixel sensor (APS)

• US 7,489,352 B2
• Filed: 11/15/2002
• Issued: 02/10/2009
• Est. Priority Date: 11/15/2002
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Nakamura, Junichi
• Primary Examiner(s): Ye; Lin
• Assistant Examiner(s): Yoder, III; Chriss S
• Application Number:
  US10/294,686
• Publication Number:
  US 20040096124A1
• Time in Patent Office: 2,279 Days
• Field of Search: 348/254, 348/296, 348/308, 348/216.1, 348/222.1, 348/239, 348/241, 348/275, 348/315, 257/291, 257/292
• US Class Current: 348/296
• CPC Class Codes: H04N 25/583 with different integration times
• CPC Class Codes: H04N 25/585 with pixels having different sensitivities within the sensor, e.g. fast or slow pixels or pixels having different sizes
• CPC Class Codes: H04N 25/778 comprising amplifiers shared between a plurality of pixels, i.e. at least one part of the amplifier must be on the sensor array itself
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters

Abstract

An image apparatus and method is disclosed for extending the dynamic range of an image sensor. A first linear pixel circuit produces a first pixel output signal based on charge integration by a first photo-conversion device over a first integration period. A second linear pixel circuit produces a second pixel output signal based on charge integration by a second photo-conversion device over a second integration period, where the second integration period is shorter than the first integration period. A sample-and-hold circuit captures signals representing the first and second pixel output signals.

Claims

1. An image apparatus, comprising:

a first linear pixel circuit for producing a first pixel output signal of a first pixel cell based on charge integration by a first photo-conversion device over a first integration period, and

a second linear pixel circuit for producing a second pixel output signal of said first pixel cell based on charge integration by a second photo-conversion device over a second integration period, wherein the second integration period is shorter than the first integration period, and said first pixel cell is structurally configured such that said second photo-conversion device receives less light than said first photo-conversion device; and

a sample-and-hold circuit for capturing signals representing said first and second pixel output signals.

2. An apparatus as in claim 1, further comprising a column line commonly connected to receive said signal representing said first and second pixel output signals.

3. An apparatus as in claim 2, wherein said sample-and-hold circuit is coupled to said common column line and sequentially captures said signals representing said first and second pixel output signals.

4. An image apparatus as in claim 1, wherein said first photo-conversion device is configured to integrate light received by a first light-receiving region over said first integration period, said second photo-conversion device is configured to integrate light received by a second light-receiving region over said second integration period, and said second light receiving region is smaller than said first light-receiving region.

5. An image apparatus as in claim 4, further comprising:

a microlens array comprising said first and second light-receiving regions.

6. An image apparatus as in claim 4, wherein said second photo-conversion device comprises said second light receiving-region and said first photo-conversion device comprises said first light-receiving region.

7. An image apparatus as in claim 1, wherein said first and second photo-conversion devices are adjacent photo-conversion devices of a photo-conversion device array.

8. An image apparatus as in claim 1, wherein said first and second integration periods are fixed in duration.

9. The image apparatus as in claim 1, wherein said first pixel output signal and said second pixel output signal are each output to the same column line output.

10. An imaging apparatus, comprising:

a first pixel circuit of a first pixel cell, said first pixel circuit configured to generate a first pixel output signal and comprising a first transfer pulse line coupled to a gate of a first transfer transistor, wherein the first transfer transistor transfers charge from a first photodiode to a floating diffusion node, and wherein said floating diffusion node is further coupled to a reset transistor and a gate of a source-follower transistor;

a second pixel circuit of said first pixel cell, said second pixel circuit configured to generate a second pixel output signal and comprising a second transfer pulse line, coupled to a gate of a second transfer transistor, wherein the second transfer transistor transfers integrated charge from a second photodiode and to the floating diffusion node, said second photodiode structurally configured to receive less light than said first photodiode;

a reset pulse line, connected to the gate of the reset transistor, wherein the reset transistor is coupled to reset the floating diffusion node to a predetermined voltage state; and

a row-select transistor, respectively coupled to the source-follower transistors for respectively coupling said first and second pixel circuits to a column signal line, said first transfer pulse line receiving a signal which operates said first photodiode to integrate charge for a first time period and said second transfer pulse line receiving a signal which operates said second photodiode to integrate charge for a second time period different from said first time period.

11. The apparatus according to claim 10, wherein the first and second photodiodes are pinned photodiodes.

12. The apparatus according to claim 11, wherein the pinned photodiodes are coupled to ground.

13. The apparatus according to claim 10, further comprising a capacitor coupled to the floating diffusion node.

14. The apparatus according to claim 13, wherein the capacitor is further coupled to ground.

15. An imaging apparatus as in claim 10, wherein said first photodiode is configured to integrate light received by a first light-receiving region over said first time period, said second photodiode is configured to integrate light received by a second light-receiving region over said second time period, and said second light-receiving region is smaller than said first light-receiving region.

16. An imaging apparatus as in claim 15, further comprising:

a microlens array comprising said first and second light-receiving regions.

17. An imaging apparatus as in claim 15, wherein said second photodiode comprises said second light-receiving region and said first photodiode comprises said first light-receiving region.

18. An imaging apparatus as in claim 10, wherein said first and second photodiodes are adjacent photodiodes of a photodiode array.

19. An imaging apparatus as in claim 10, wherein said first and second integration periods are fixed in duration.