Method of calibrating sensitivity gain

• US 8,144,318 B2
• Filed: 04/22/2010
• Issued: 03/27/2012
• Est. Priority Date: 12/24/2009
• Status: Active Grant

• Current Assignee: Ability Enterprise Co., Ltd.
• Original Assignee: Ability Enterprise Co., Ltd.
• Inventors: Wang, Chung-Chi, LEE, Yi-Jian
• Primary Examiner(s): Nguyen, Sang
• Application Number:
  US12/765,823
• Publication Number:
  US 20110157583A1
• Time in Patent Office: 705 Days
• Field of Search: 356/243.1, 438/208.4, 438/208.12, 438/208.16, 438/222.1, 438/72, 438/79, 438/362, 438/231.3, 438/349, 369 52- 55
• US Class Current: 356/243.1
• CPC Class Codes: G01J 1/16 using electric radiation detectors G01J1/20 takes precedence
• CPC Class Codes: H04N 17/002 for television cameras
• CPC Class Codes: H04N 23/76 by influencing the image signals

Abstract

The present invention is directed to a method of calibrating sensitivity gain. In a preview mode, an imaging device is calibrated by a standard light source, therefore obtaining standard sensitivity gain of the preview mode. In a capture mode, the imaging device is calibrated by the standard light source, therefore obtaining standard sensitivity gain of the capture mode. A gain ratio of the standard sensitivity gain of the capture mode to the standard sensitivity gain of the preview mode is determined, and is then used to deduce the exposure parameters of the capture mode according to the exposure parameters of the preview mode.

Claims

1. A method of calibrating sensitivity gain, comprising:

using an automatic gain control (AGC) electric circuit to perform the steps of;

providing a standard light source;

calibrating an imaging device by the standard. light source in a preview mode, thereby obtaining a standard sensitivity gain of the preview mode;

calibrating the imaging device by the standard light source in a capture mode, thereby obtaining a standard sensitivity gain of the capture mode; and

determining a gain ratio of the standard sensitivity gain of the capture mode to the standard sensitivity gain of the preview mode;

wherein the gain ratio is used to deduce exposure parameters of the capture mode according to exposure parameters of the preview mode when operating the imaging device.

2. The method of claim 1, wherein the imaging device is a digital camera or a digital camcorder.

3. The method of claim 1, wherein the standard light source is a Commission internationale de l′

eclairage (CIE) standard light source.

4. The method of claim 1, wherein pixels sensed by the imaging device in the preview mode are a part of pixels sensed in the capture mode.

5. The method of claim 4, wherein the pixels sensed by the imaging device in the preview mode are one-sixth of the pixels sensed in the capture mode.

6. The method. of claim 1, after determining the gain ratio, further comprising a step of storing the gain ratio in the imaging device.

7. The method of claim 1, in the calibration steps of the preview mode and the capture mode, a calibration parameter of the imaging device is a predetermined speed value (Sv), and the standard light source has a predetermined luminance value (Bv), accordingly, the imaging device has a fixed exposure value (Ev), conforming to Ev=Bv+Sv.

8. The method of claim 7, wherein the exposure parameters of the preview mode and of the capture mode comprise aperture value (Av) and time value (Tv), which conform to Ev=Av+Tv.

9. The method of claim 1, wherein the standard sensitivity gain of the preview mode and the standard sensitivity gain of the capture mode obtained in the calibrating steps are generated by an automatic gain control (AGC) unit of the imaging device.

10. The method of claim 1, wherein a plurality of the standard sensitivity gains are obtained in the calibrating step of the preview mode.

11. The method of claim 10, further comprising constructing a preview mode lookup table (LUT) to store the plurality of standard sensitivity gains in the preview mode.

12. The method of claim 1, wherein a plurality of the standard sensitivity gains are obtained in the calibrating step of the capture mode.

13. The method of claim 12, further comprising constructing a capture mode lookup table (LUT) to store the plurality of standard sensitivity gains in the capture mode.

14. An imaging system, comprising:

an automatic gain control (AGC) electric circuit configured to generate a standard sensitivity gain of a preview mode, and a standard sensitivity gain of a capture mode, wherein the standard sensitivity gain of the preview mode is generated by subject to calibration by a standard light source in the preview mode, and the standard sensitivity gain of the capture mode is generated by subject to calibration by the standard light source in the capture mode;

wherein the AGC electric circuit determines a gain ratio of the standard. sensitivity gain of the capture mode to the standard sensitivity gain of the preview mode; and

wherein the gain ratio is used. to deduce exposure parameters of the capture mode according to exposure parameters of the preview mode.

15. The system of claim 14, wherein the standard light source is a Commission internationale de l′

eclairage (CIE) standard light source.

16. The system of claim 14, wherein the gain ratio is further stored.

17. The system of claim 14, wherein the AGC electric circuit in the calibration of the preview mode and the capture mode uses a calibration parameter, which is a predetermined speed value (Sv), and the standard light source has a predetermined luminance value (Bv), thereby obtaining a fixed exposure value (Ev) conforming to Ev=Bv+Sv.

19. The system of claim 14, wherein the AGC electric circuit generates a plurality of the standard sensitivity gains in the calibration of the preview mode, and constructs a preview mode lookup table (LUT) to store the plurality of standard sensitivity gains in the preview mode.

20. The system of claim 14, wherein the AGC electric circuit generates a plurality of the standard sensitivity gains in the calibration of the capture mode, and constructs a capture mode lookup table (LUT) to store the plurality of standard sensitivity gains in the capture mode.

18. The system of claim , wherein the exposure parameters of the preview mode and the capture mode comprise aperture value (Av) and time value (Tv), which conform to Ev=Av+Tv.