Dual conversion gain high dynamic range sensor

Patent metadata

Field	Value
Publication number	US-9402039-B2
Application number	US-201414554787-A
Country	US
Kind code	B2
Filing date	Nov 26, 2014
Priority date	Jan 10, 2014
Publication date	Jul 26, 2016
Grant date	Jul 26, 2016

Abstract

A method of reading out a pixel includes resetting a photodetector of the pixel. Light incident on the photodetector is then integrated for a single exposure of a single image capture. A floating diffusion node of the pixel is then reset. The floating diffusion is set to low conversion gain and a low conversion gain reset signal is sampled from the floating diffusion node. The floating diffusion is set to high conversion gain and a high conversion gain reset signal is sampled from the floating diffusion node. Charge carriers are transferred from the photodetector to the floating diffusion node and a high conversion image signal is then sampled from the floating diffusion node. The floating diffusion is set to low conversion gain. Charge carriers are transferred again from the photodetector to the floating diffusion node and a low conversion image signal is sampled from the floating diffusion node.

First claim

What is claimed is:

1. A method of acquiring image data from a pixel from a single exposure of a single image capture in a high dynamic range (HDR) image sensor, comprising:
resetting a photodetector of the pixel;
integrating light incident on the photodetector for the single exposure of the single image capture;
performing a first reset of a floating diffusion of the pixel;
setting the floating diffusion to low conversion gain;
sampling a low conversion gain reset signal from the floating diffusion;
performing a second reset of the floating diffusion of the pixel after the sampling of the reset signal from the floating diffusion at the low conversion gain, and prior to a sampling of the reset signal from the floating diffusion at a high conversion gain;
setting the floating diffusion to the high conversion gain;
sampling a high conversion gain reset signal from the floating diffusion;
transferring charge carriers photogenerated during the single exposure from the photodetector to the floating diffusion;
sampling a high conversion gain image signal from the floating diffusion;
setting the floating diffusion to the low conversion gain;
transferring additional charge carriers photogenerated during the single exposure from the photodetector to the floating diffusion; and
sampling a low conversion gain image signal from the floating diffusion.

2. The method of claim 1 further comprising determining a low conversion gain correlated double sampling image signal output value of the single exposure of the single image capture by finding a difference between the sampled low conversion gain image signal and the sampled low conversion gain reset signal.

3. The method of claim 1 further comprising determining a high conversion gain correlated double sampling image signal output value of the single exposure of the single image capture by finding a difference between the sampled high conversion gain image signal and the sampled high conversion gain reset signal.

4. The method of claim 1 wherein resetting the photodetector of the pixel comprises coupling the photodetector to a reset voltage.

5. The method of claim 4 further comprising setting the reset voltage of the pixel while integrating the light incident on the photodetector for the single exposure of the single image capture to provide an anti-blooming path from the photodetector to the floating diffusion node.

6. The method of claim 1 wherein resetting the floating diffusion of the pixel comprises coupling the floating diffusion to a boosting voltage.

7. The method of claim 1 wherein setting the floating diffusion to low conversion gain comprises coupling an in-pixel capacitor to the floating diffusion.

8. The method of claim 7 wherein setting the floating diffusion to high conversion gain comprises decoupling the in-pixel capacitor from the floating diffusion.

9. The method of claim 1 wherein transferring the charge carriers photogenerated during the single exposure from the photodetector to the floating diffusion comprises coupling the photodetector to the floating diffusion through a transfer transistor after setting the floating diffusion to the high conversion gain.

10. The method of claim 9 wherein transferring the additional charge carriers photogenerated during the single exposure from the photodetector to the floating diffusion comprises coupling the photodetector to the floating diffusion through the transfer transistor after setting the floating diffusion to the low conversion gain.

11. A pixel cell for use in a high dynamic range (HDR) image sensor, comprising:
a photodetector adapted to photogenerate charge carriers in response to incident light during a single exposure of a single image capture of the HDR image sensor;
a floating diffusion coupled to receive the charge carriers photogenerated in the photodetector;
an in-pixel capacitor selectively coupled to the floating diffusion through a first transistor, wherein the floating diffusion is set to low conversion gain in response to the in-pixel capacitor being coupled to the floating diffusion, wherein the floating diffusion is set to high conversion gain in response to the in-pixel capacitor being decoupled to the floating diffusion; and
a transfer transistor coupled between the photodetector and the floating diffusion, wherein the transfer transistor is adapted to be switched on a first time during the single exposure of the single image capture of the HDR image sensor to transfer the charge carriers photogenerated in the photodetector to the floating diffusion set to the high conversion gain, wherein the transfer transistor is adapted to be switched on a second time during the single exposure of the single image capture of the HDR image sensor to transfer the charge carriers photogenerated in the photodetector to the floating diffusion set to the low conversion gain.

12. The pixel cell of claim 11 further comprising an amplifier transistor having a gate terminal coupled to the floating diffusion to generate an output signal of the pixel cell to an output bitline of the pixel cell.

13. The pixel cell of claim 12 further comprising a row select transistor coupled to the amplifier transistor to selectively generate the output signal of the pixel cell to the output bitline of the pixel cell.

14. A high dynamic range (HDR) imaging system, comprising:
a pixel array of pixel cells, wherein each one of the pixel cells includes:
a photodetector adapted to photogenerate charge carriers in response to incident light during a single exposure of a single image capture of the HDR imaging system;
a floating diffusion coupled to receive the charge carriers photogenerated in the photodetector;
an in-pixel capacitor selectively coupled to the floating diffusion through a first transistor, wherein the floating diffusion is set to low conversion gain in response to the in-pixel capacitor being coupled to the floating diffusion, wherein the floating diffusion is set to high conversion gain in response to the in-pixel capacitor being decoupled to the floating diffusion; and
a transfer transistor coupled between the photodetector and the floating diffusion, wherein the transfer transistor is adapted to be switched on a first time during the single exposure of the single image capture of the HDR imaging system to transfer the charge carriers photogenerated in the photodetector to the floating diffusion set to the high conversion gain, and wherein the transfer transistor is adapted to be switched on a second time during the single exposure of the single image capture of the HDR imaging system to transfer the charge carriers photogenerated in the photodetector to the floating diffusion set to the low conversion gain;

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

15. The HDR imaging system of claim 14 further comprising a function logic coupled to the readout circuitry to store the image data from each one of the plurality of pixel cells.

16. The HDR imaging system of claim 14 wherein each one of the plurality of pixel cells further comprises an amplifier transistor having a gate terminal coupled to the floating diffusion to generate the image data output from the pixel cell to an output bitline of the pixel cell.

17. The HDR imaging system of claim 16 wherein each one of the plurality of pixel cells further comprises a row select transistor coupled to the amplifier transistor to selectively generate the image data o

Assignees

• Omnivision Tech Inc

Inventors

• Solhusvik Johannes
• Johansson Robert

Classifications

• H04N25/623

  by evacuation via the output or reset lines · CPC title

• H04N25/771

  comprising storage means other than floating diffusion · CPC title

• H04N25/59 Primary

  by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance · CPC title

• H04N5/37452

  Electricity · mapped topic

• H04N5/3594

  Electricity · mapped topic