CMOS image sensor with wide dynamic range

• US 7,619,674 B2
• Filed: 01/24/2006
• Issued: 11/17/2009
• Est. Priority Date: 01/24/2005
• Status: Expired due to Fees

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc), Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Han, Sang-Wook, Yoon, Euisik
• Primary Examiner(s): Tran, Sinh
• Assistant Examiner(s): Le, Quang V
• Application Number:
  US11/337,530
• Publication Number:
  US 20060181625A1
• Time in Patent Office: 1,393 Days
• Field of Search: 348/302, 348/312, 348/294, 348/297, 348/281, 250/208.1
• US Class Current: 348/308
• 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 25/533 by using differing integration times for different sensor regions
• 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

Abstract

The present invention provides a CMOS image sensor for broadening a dynamic range by controlling an integration time for each pixel to thereby obtain a high quality image with a low noise. The CMOS image sensor according to the present invention includes plural pixels, each for storing an integration time of a present frame, and control means for controlling the integration time of a next frame based on the stored integration time.

Claims

1. An apparatus for converting a real image into an electric signal, comprising:

plural pixels, each for storing an integration time of a present frame that is estimated by the illumination of a prior frame; and

control means for controlling the integration time of the present frame based on the stored integration time,

wherein each pixel includes;

a photodiode for receiving a light of a real image to generate a photo charge corresponding to the light;

a transfer transistor for selectively transferring the photo charge;

a junction capacitor for receiving the photo charge when the transfer transistor is turned on and, before receiving the photo charge, storing the integration time of the present frame;

a reset transistor for receiving a first control signal having first and second predetermined voltage levels to reset the junction capacitor to the first predetermined voltage level or supply the second predetermined voltage level calculated based on the integration time to the junction capacitor in response to a reset signal;

a drive transistor for outputting the electric signal corresponding to a charge amount transferred from the junction capacitor; and

a select transistor for controlling a transmission of an electric signal outputted from the drive transistor.

2. The apparatus as recited in claim 1, wherein each pixel includes:

a control transistor for controlling the transfer transistor.

3. The apparatus as recited in claim 2, wherein the plural pixels are arranged into a predetermined number of columns and the control means controls the plural pixels in a basis of column by column.

4. The apparatus as recited in claim 3, wherein the control transistor controls the transfer transistor by using a second control signal in response to a transfer signal which is inputted to a gate.

5. The apparatus as recited in claim 4, wherein the first and second control signals are generated by a column controller.

6. The apparatus as recited in claim 1, wherein the first predetermined voltage is a power source voltage.

7. The apparatus as recited in claim 1, wherein the select transistor coupled between a power source voltage and the drive transistor is turned on by a select signal.

8. An image sensor for converting a real image into an electric signal, comprising:

a pixel array block including plural unit pixels, each for storing an integration time of a prior frame, wherein the plural unit pixels is arranged in a form of N by M matrix, N and M being positive integers; and

a control block having plural column controllers, each for controlling an integration time of a present frame based on the stored integration time in a basis of column by column,

wherein each pixel includes;

a photodiode for receiving a light of a real image to generate a photo charge corresponding to the light;

a transfer transistor for selectively transferring the photo charge;

a junction capacitor for receiving the photo charge when the transfer transistor is turned on and, before receiving the photo charge, storing the integration time of the present frame;

a reset transistor for receiving a first control signal having first and second predetermined voltage levels to reset the junction capacitor to the first predetermined voltage level or supply the second predetermined voltage level calculated based on the integration time to the junction capacitor in response to a reset signal;

a drive transistor for outputting the electric signal corresponding to a charge amount transferred from the junction capacitor; and

a select transistor for controlling a transmission of an electric signal outputted from the drive transistor.

9. The image sensor as recited in claim 8, wherein the control block includes:

a first block for checking the integration time of the present frame based on the stored integration time in a basis of column by column to store the checked value to each unit pixel;

a second block for receiving the checked value of the integration times which are respectively stored in other row lines of the present frame, in a basis of column by column, when an image corresponding to a first row line of the present frame is read out; and

a third block for resetting each unit pixel based on the integration time of each pixel.

10. The image sensor as recited in claim 8, wherein each unit pixel includes:

a control transistor for controlling the transfer transistor in response to a second control signal.

11. The image sensor as recited in claim 10, wherein the pixel array block includes a plurality of 2×

2 neighbor unit pixels sharing a transistor, the 2×

2 neighbor unit pixels respectively including a first to fourth unit pixels, each having the photodiode, the transfer transistor, the control transistor, the junction capacitor, the reset transistor, the drive transistor, and the select transistor.

12. The image sensor as recited in claim 10, wherein the first unit pixel and the second unit pixel share the control transistor, the junction capacitor, the reset transistor, the drive transistor, and the select transistor, the first and second unit pixels arranged in a same row line.

13. The image sensor as recited in claim 12, wherein the third unit pixel and the fourth unit pixel share the junction capacitor, the reset transistor, the drive transistor, and the select transistor, the third and fourth unit pixels arranged in a same row line.

14. The image sensor as recited in claim 13, wherein the first unit pixel and the third unit pixel share the control transistor, the first and third unit pixels arranged in a same column line.

15. The image sensor as recited in claim 14, wherein the second unit pixel and the fourth unit pixel share the control transistor, the second and fourth unit pixels arranged in a same column line.

16. A method for converting a real image into an electric signal, comprising:

storing integration times of a present frame, which is estimated by the illumination of a prior frame, to unit pixels respectively, wherein the unit pixels, each having a junction capacitor at a sensing node, are arranged in a form of N by M matrix, N and M being positive integers; and

controlling the integration time of the present frame based on the stored integration time in a basis of column by column by resetting the junction capacitor to a first predetermined voltage level or supplying a second predetermined voltage level calculated based on the integration time to the junction capacitor in response to a reset signal.

17. The method as recited in claim 16, wherein the controlling the integration time includes:

checking the integration time of the present frame based on the stored integration time in a basis of column by column to store the checked value to each unit pixel;

receiving the checked value of the integration times which are respectively stored in other row lines of the present frame, in a basis of column by column, when an image corresponding to a first row line of the present frame is read out; and

resetting each unit pixel based on the integration time of each pixel.

18. The method as recited in claim 17, wherein, during resetting each unit pixel, if the integration time stored in a predetermined unit pixel is over a predetermined time, a photodiode of the same unit pixel is reset;

otherwise, the photodiode of the same unit pixel is not reset.