CMOS image sensor with wide dynamic range

• US 20060181625A1
• Filed: 01/24/2006
• Published: 08/17/2006
• Est. Priority Date: 01/24/2005
• Status: Active Grant

• 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
• Granted Patent: US 7,619,674 B2
• Time in Patent Office: Days
• US Class Current: 348/297
• 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 the prior frame; and

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

2. The apparatus as recited in claim 1, wherein the 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 transferring the photo charge;

a control transistor for controlling the transfer transistor;

a junction capacitor for receiving the photo charge transferred by the transfer transistor 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 resetting the junction capacitor or storing the integration time to the junction capacitor;

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.

3. The apparatus as recited in claim 2, wherein the plural pixels are arraigned 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 first 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 control signal is generated by a column controller.

6. The apparatus as recited in claim 5, wherein the reset transistor resets the junction capacitor to a first predetermined voltage level or stores the integration time to the junction capacitor based on a reset signal inputted through a gate and a second control signal, the integration time supplied by the second control signal.

7. The apparatus as recited in claim 6, wherein the second control signal, generated by the column controller, has the first predetermined voltage level for resetting the junction capacitor and a second predetermined voltage level corresponding to the integration time for storing the integration time to the junction capacitor.

8. The apparatus as recited in claim 7, wherein the first predetermined voltage is a power source voltage.

9. The apparatus as recited in claim 8, wherein the select transistor coupled between a power source voltage and the drive transistor is turned on by a select signal.

10. 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 the integration time of a present frame based on the stored integration time in a basis of column by column.

11. The image sensor as recited in claim 10, wherein the control block includes:

a first block for checking the integration time of each pixel in a basis of column by column to thereby store the checked value to each unit pixel, the integration time inputted at the prior frame;

a second block for receiving a record about M-1 number of the integration times which are respectively stored in M-1 number of N unit pixels, each corresponding to each different row line, in a basis of column by column; and

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

12. The image sensor as recited in claim 10, wherein the unit 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 transferring the photo charge;

a control transistor for controlling the transfer transistor;

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

a reset transistor for resetting the junction capacitor or storing the integration time to the junction capacitor;

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.

13. The image sensor as recited in claim 12, 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.

14. The image sensor as recited in claim 12, 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.

15. The image sensor as recited in claim 14, 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 arraigned in a same row line.

16. The image sensor as recited in claim 15, wherein the first unit pixel and the third unit pixel share the control transistor, the first and third unit pixels arraigned in a same column line.

17. The image sensor as recited in claim 16, wherein the second unit pixel and the fourth unit pixel share the control transistor, the second and fourth unit pixels arraigned in a same column line.

18. A method for converting a real image into an electric signal, comprising the steps of:

storing integration times of a prior frame to unit pixels respectively, wherein the unit pixels are arranged in a form of N by M matrix, N and M being positive integers; and

controlling the integration time of a present frame based on the stored integration time that is estimated by the amount of prior frame illumination for each pixel in a basis of column by column.

19. The method as recited in claim 18, wherein the controlling the integration time includes the steps of:

checking the integration time of each pixel in a basis of column by column to thereby store the checked value to each unit pixel, the integration time inputted at the prior frame;

receiving a record about M-1 number of the integration times which are respectively stored in M-1 number of N unit pixels, each corresponding to each different row line, in a basis of column by column; and

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

20. The method as recited in claim 19, 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.