Image pickup device, its control method, and camera

• US 8,883,526 B2
• Filed: 12/06/2010
• Issued: 11/11/2014
• Est. Priority Date: 01/14/2005
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Okita, Akira, Koizumi, Toru, Ueno, Isamu, Sakurai, Katsuhito
• Primary Examiner(s): Gurley, Lynne
• Assistant Examiner(s): Webb, Vernon P
• Application Number:
  US12/960,701
• Publication Number:
  US 20110074993A1
• Time in Patent Office: 1,436 Days
• Field of Search: 257/291, 257/E27.131, 257/E31.097, 257/E27.13, 438/24, 348/294
• US Class Current: 438/24
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• 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 25/575 with a response composed of multiple slopes
• CPC Class Codes: H04N 25/583 with different integration times
• CPC Class Codes: H04N 25/587 acquired sequentially, e.g. using the combination of odd and even image fields
• CPC Class Codes: H04N 25/59 by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance
• CPC Class Codes: H04N 25/621 for the control of blooming
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

An image pickup device, wherein a part of the carriers overflowing from the photoelectric conversion unit for a period of photoelectrically generating and accumulating the carriers may be flowed into the floating diffusion region, and a pixel signal generating unit generating a pixel signal according to the carriers stored in the photoelectric conversion unit and the carriers having overflowed into the floating diffusion region, is provided. The expansion of a dynamic range and the improvement of an image quality can be provided by controlling a ratio of the carriers flowing into the floating diffusion region to the carriers overflowing from such a photoelectric conversion unit at high accuracy.

Claims

1. A method of driving an image pickup device that includes a photoelectric conversion unit for generating carriers by photoelectric conversion and accumulating the carriers, a floating diffusion region, a transfer transistor for transferring the carriers from the photoelectric conversion unit to the floating diffusion region, a reset transistor for resetting the floating diffusion region, and a signal holding unit, the method comprising:

supplying a third gate voltage to a gate of the transfer transistor, the third gate voltage being between a first gate voltage that turns on the transfer transistor and a second gate voltage that turns off the transfer transistor;

holding a signal based on the carriers transferred during the supplying at the signal holding unit; and

resetting the floating diffusion region having the carriers transferred during the supplying,

wherein the holding is performed between the supplying and the resetting.

2. The method according to claim 1, wherein the third gate voltage is a voltage based on an amplification degree of the pixel signal.

3. The method according to claim 1, wherein the third gate voltage is a voltage based on a temperature.

4. The method according to claim 1, wherein the third gate voltage is a voltage that causes a height of a potential barrier under the transfer gate between the photoelectric conversion unit and the floating diffusion region to be a lowest height among heights of potential barriers surrounding the photoelectric conversion unit.

5. The method according to claim 1, wherein the image pickup device further includes a first element adjacent to the photoelectric conversion unit and connected to a power source, and wherein the third gate voltage is a voltage that causes a height of a potential barrier under the transfer gate to be the same as a height of a potential barrier between the photoelectric conversion unit and the first element.

6. The method according to claim 1, wherein the image pickup device further includes a first element adjacent to the photoelectric conversion unit and connected to a power source, and wherein the method further comprises controlling a ratio of carriers flowing to the floating diffusion region to carriers flowing to the first element by supplying the third gate voltage.

7. The method according to claim 2, wherein the amplification degree of the pixel signal is an ISO speed.

15. The method according to claim 1, wherein the image pickup device further includes a reset transistor, and wherein the method further comprises keeping the reset transistor turned off during supply of the third gate voltage to the gate of the transfer transistor.

16. The method according to claim 15, wherein the holding is performed after the keeping.

17. The method according to claim 1, wherein the resetting is not performed between the supplying and the holding.

8. A method of driving an image pickup device that includes a photoelectric conversion unit for generating carriers, a floating diffusion region, a transfer transistor for transferring the carriers from the photoelectric conversion unit to the floating diffusion region, a signal holding unit, and a reset transistor for resetting the floating diffusion region, the method comprising:

supplying a third gate voltage to a gate of the transfer transistor, the third gate voltage being between a first gate voltage that turns on the transfer transistor and a second gate voltage that turns off the transfer transistor;

keeping the reset transistor turned off during supply of the third gate voltage to the gate of the transfer transistor;

holding a signal based on the carriers transferred during the supplying at the signal holding unit; and

resetting the floating diffusion region having the carriers transferred during the supplying by the reset transistor,

wherein the holding is performed between the supplying and the resetting.

9. The method according to claim 8, wherein the third gate voltage is a voltage based on an amplification degree of the pixel signal.

10. The method according to claim 9, wherein the amplification degree of the pixel signal is an ISO speed.

11. The method according to claim 8, wherein the third gate voltage is a voltage based on a temperature.

12. The method according to claim 8, wherein the third gate voltage causes a height of a potential barrier under the transfer gate between the photoelectric conversion unit and the floating diffusion region to be a lowest height among heights of potential barriers surrounding the photoelectric conversion unit.

13. The method according to claim 8, wherein the image pickup device further includes a first element adjacent to the photoelectric conversion unit and connected to a power source, and wherein the third gate voltage is a voltage that causes a height of a potential barrier under the transfer gate to be same as a height of a potential barrier between the photoelectric conversion unit and the first element.

14. The method according to claim 13, wherein a ratio of carriers flowing to the floating diffusion region to carriers flowing to the first element is determined by the third gate voltage.

18. The method according to claim 8, wherein the resetting is not performed between the supplying and the holding.