Big-small pixel scheme for image sensors

Patent metadata

Field	Value
Publication number	US-9305949-B2
Application number	US-201314070286-A
Country	US
Kind code	B2
Filing date	Nov 1, 2013
Priority date	Nov 1, 2013
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

An image sensor pixel for use in a high dynamic range image sensor includes a first photodiode, a plurality of photodiodes, a shared floating diffusion region, a first transfer gate, and a second transfer gate. The first photodiode is disposed in a semiconductor material. The first photodiode has a first light exposure area and a first doping concentration. The plurality of photodiodes is also disposed in the semiconductor material. Each photodiode in the plurality of photodiodes has the first light exposure area and the first doping concentration. The first transfer gate is coupled to transfer first image charge from the first photodiode to the shared floating diffusion region. The second transfer gate is coupled to transfer distributed image charge from each photodiode in the plurality of photodiodes to the shared floating diffusion region.

First claim

What is claimed is:

1. An image sensor pixel for use in a high dynamic range image sensor, the image sensor pixel comprising:
a first photodiode disposed in a semiconductor material, wherein the first photodiode has a first light exposure area and a first doping concentration;
a plurality of photodiodes disposed in the semiconductor material, wherein each photodiode in the plurality of photodiodes has the first light exposure area and the first doping concentration;
a shared floating diffusion region;
a first transfer gate coupled to transfer first image charge from the first photodiode to the shared floating diffusion region in response to a first transfer signal; and
a second transfer gate coupled to simultaneously transfer distributed image charge from each photodiode in the plurality of photodiodes to the shared floating diffusion region in response to a common transfer signal that is distinct from the first transfer signal.

2. The image sensor pixel of claim 1 , wherein the second transfer gate includes sub-gates coupled between the shared floating diffusion region and each photodiode in the plurality of photodiodes, wherein each of the sub-gates is electrically connected to receive the common transfer signal.

3. The image sensor pixel of claim 1 , wherein the plurality of photodiodes and the first photodiode are evenly spaced in a symmetrical pattern.

4. The image sensor pixel of claim 3 , wherein the plurality of photodiodes consists of three photodiodes.

5. The image sensor pixel of claim 3 , wherein the plurality of photodiodes consists of fifteen photodiodes.

6. The image sensor pixel of claim 1 further comprising a reset transistor disposed in the semiconductor material and coupled to the shared floating diffusion region.

7. The image sensor pixel of claim 1 further comprising an amplifier transistor disposed in the semiconductor material, a gate of the amplifier transistor coupled to the shared floating diffusion region.

8. The image sensor pixel of claim 7 further comprising a select transistor disposed in the semiconductor material between the amplifier transistor and a readout column line.

9. The image sensor pixel of claim 1 , wherein each photodiode in the plurality of photodiodes has a first charge capacity that is substantially equal to a second charge capacity of the first photodiode.

10. The image sensor pixel of claim 1 , wherein the floating diffusion region includes a plurality of local floating diffusions electrically coupled together.

11. A high dynamic range imaging system comprising:
a pixel array having a plurality of image sensor pixels, wherein each one of the plurality of image sensor pixels includes:
a first photodiode disposed in a semiconductor material, wherein the first photodiode has a first light exposure area and a first doping concentration;
a plurality of photodiodes disposed in the semiconductor material, wherein each photodiode in the plurality of photodiodes has the first light exposure area and the first doping concentration;

a shared floating diffusion region;
a first transfer gate coupled to transfer first image charge from the first photodiode to the shared floating diffusion region in response to a first transfer signal; and
a second transfer gate coupled to simultaneously transfer distributed image charge from each photodiode in the plurality of photodiodes to the shared floating diffusion region in response to a common transfer signal that is distinct from the first transfer signal;

control circuitry coupled to the pixel array to control operation of the pixel array; and
readout circuitry coupled to the pixel array to readout image data from the plurality of image sensor pixels.

12. The imaging system of claim 11 , wherein image sensor pixels in the plurality of image sensor pixels are included in a pixel group, wherein each respective image sensor pixel in the pixel group is disposed under a first filter that filters out a first target wavelength of image light propagating toward the respective image sensor pixels disposed under the first filter, the first filter being different than a second filter disposed over an adjacent image sensor pixel in the pixel group, wherein the second filter filters out a second target wavelength of image light different than the first target wavelength.

13. The imaging system of claim 12 , wherein the first filter is a red filter, the second filter is a green filter, and the pixel group includes a blue filter disposed adjacent to the green filter.

14. The imaging system of claim 11 , wherein the second transfer gate includes sub-gates coupled between the shared floating diffusion region and each photodiode in the plurality of photodiodes, wherein each of the sub-gates is electrically connected to receive the common transfer signal.

15. The imaging system of claim 11 , wherein the plurality of photodiodes and the first photodiode are evenly spaced in a symmetrical pattern.

16. The imaging system of claim 11 , wherein the plurality of photodiodes consists of three photodiodes.

17. The imaging system of claim 11 , wherein the plurality of photodiodes consists of fifteen photodiodes.

18. The imaging system of claim 11 , wherein each photodiode in the plurality of photodiodes has a first charge capacity that is substantially equal to a second charge capacity of the first photodiode.

19. The imaging system of claim 11 , wherein the floating diffusion region includes a plurality of local floating diffusions electrically coupled together.

20. A high dynamic range imaging system comprising:
a pixel array having a plurality of image sensor pixels, wherein each one of the plurality of image sensor pixels includes:
a first photodiode disposed in a semiconductor material, wherein the first photodiode has a first light exposure area and a first doping concentration;
a plurality of photodiodes disposed in the semiconductor material, wherein each photodiode in the plurality of photodiodes has the first light exposure area and the first doping concentration;

a shared floating diffusion region;
a first transfer gate coupled to transfer first image charge from the first photodiode to the shared floating diffusion region; and
a second transfer gate coupled to transfer distributed image charge from each photodiode in the plurality of photodiodes to the shared floating diffusion region;

control circuitry coupled to the pixel array to control operation of the pixel array; and
readout circuitry coupled to the pixel array to readout image data from the plurality of image sensor pixels, wherein image sensor pixels in the plurality of image sensor pixels are included in a pixel group, wherein each respective image sensor pixel in the pixel group is disposed under a first filter that filters out a first target wavelength of image light propagating toward the respective image sensor pixels disposed under the first filter, the first filter being different than a second filter disposed over an adjacent image sensor pixel in the pixel group, wherein the second filter filters out a second target wavelength of image light different than the first target wavelength.

21. The imaging system of claim 20 , wherein the first filter is a red filter, the second filter is a green filter, and the pixel group includes a blue filter disposed adjacent to the green filter.

Assignees

• Omnivision Tech Inc

Inventors

• Chen Gang
• Mao Duli
• Yang Dajiang
• Xiong Zhibin
• Tai Dyson H

Classifications

• H10F39/8053

  Colour filters · CPC title

• H10F39/813

  Electronic components shared by multiple pixels, e.g. one amplifier shared by two pixels · CPC title

• H10F39/182

  Colour image sensors · CPC title

• H10F39/80373 Primary

  characterised by the gate of the transistor · CPC title

• H01L27/14645

  Electricity · mapped topic