Dynamic range extension for CMOS image sensors

• US 20020057845A1
• Filed: 10/18/2001
• Published: 05/16/2002
• Est. Priority Date: 10/20/2000
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Photobit Corporation (Micron Technology, Inc.)
• Inventors: Wang, Yibing, Sandor, Barna L., Fossum, Eric R.
• Granted Patent: US 6,734,905 B2
• Time in Patent Office: Days
• US Class Current: 382/270
• CPC Class Codes: H04N 23/70 Circuitry for compensating brightness variation in the scene
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors
• CPC Class Codes: H04N 23/84 for processing colour signals
• CPC Class Codes: H04N 25/57 Control of the dynamic range
• CPC Class Codes: H04N 25/70 SSIS architectures; Circuits associated therewith
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters

Abstract

An image sensor for capturing and producing an image includes a photoreceptor array that receives light and produces a signal for each pixel of the image. The image sensor further includes amplification circuitry that amplifies the signals. The amplification circuitry provides two distinct gains for each of the signals to produce two output signal levels. The image sensor also includes a fusion module, which combines the two output signal levels into one signal level. Accordingly, overall dynamic range of the image sensor is increased.

Claims

1. An image sensor comprising:

amplification circuitry receiving pixel based image signals, and amplifying some of the image signals with two distinct gains, to produce two output signal levels; and

a fusion module, operating to combine the two output signal levels in a way that increases an effective dynamic range of the image signals.

2. The image sensor of claim 1 further comprising a photoreceptor receiving light and producing a signal indicative thereof.

3. The image sensor of claim 1 wherein the amplification circuitry includes two parallel gain amplifiers that provide the two distinct gains at the same time.

4. The image sensor of claim 1 wherein the amplification circuitry includes a single gain amplifier that provides the two distinct gains at different times.

5. The image sensor of claim 4 wherein the amplification controlled by a reset signal and a switch timing signal for the gain amplifier to provide the two distinct gains at different times, the switch timing signal leading the reset signal by some part of an overall cycle.

6. The image sensor of claim 1 wherein the fusion module is analog.

7. The image sensor of claim 1 wherein the fusion module is digital.

8. The image sensor of claim 7 further comprising a time-multiplexed analog-to-digital converter that precedes the fusion module producing a digital signal for said fusion module.

9. The image sensor of claim 7 further comprising two parallel analog-to-digital converters that precede the fusion module producing a digital signal for said fusion module.

10. The image sensor of claim 1 further comprising selecting the two gains based on a pre-determined degree of improvement in a dynamic range of the image sensor with respect to the output signal levels.

11. The image sensor of claim 1 wherein the amplification circuitry and the fusion module are located on a single chip.

13. The method of claim 12 wherein the amplifying provides the two distinct gains at the same time.

14. The method of claim 12 wherein the amplifying provides the two distinct gains at different times.

15. The method of claim 12 wherein the amplifying further includes controlling the gain amplifier with a reset signal and a switch timing signal to provide the two distinct gains at different times, the switch timing signal leading the reset signal by a part of an overall cycle.

16. The method of claim 12 wherein the combining is performed in analog.

17. The method of claim 12 wherein the combining is performed digitally.

18. The method of claim 17 further comprising digitizing the two pixel signal levels by a time-multiplexed analog-to-digital converter before the combining.

19. The method of claim 17 further comprising digitizing the two pixel signal levels by two analog-to-digital converters before the combining.

20. The method of claim 12 further comprising choosing the two gains based on a pre-determined degree of improvement in a dynamic range of the image sensor and the output signal levels of the amplification circuitry.

21. The method of claim 12 wherein the combining of the two output signal levels includes adding the two output signal levels.

22. The method of claim 12 wherein the combining of the two output signal levels includes merging the two output signal levels.

24. The image sensing system of claim 23 further comprising:

a color filter array preceding the photoreceptor array to separate color information in the image; and

a color processing unit following the fusion module to restore the color information.

25. The image sensing system of claim 23 wherein the photoreceptor array, the readout circuitry, the analog-to-digital converter, and the fusion module are located on the same chip.

26. The image sensor system of claim 23 wherein the readout circuitry includes two parallel gain amplifiers to provide the two distinct gains at the same time.

27. The image sensor system of claim 23 wherein the readout circuitry includes a single gain amplifiers to provide the two distinct gains at different times.

12. A method comprising:

amplifying pixel signal levels of an image using two distinct gains to produce two output signal levels; and

combining the two output signal levels in a way that increases an effective dynamic range.

23. An image sensing system comprising:

a photoreceptor array receiving light and producing a signal indicative thereof;

readout circuitry amplifying said signal with two separate gains to produce two output signal levels;

an analog-to-digital converter for digitizing the two output signal levels; and

a fusion module for combining the two output signal levels.