Light sensitivity calibration method and an imaging device

1. A light sensitivity calibration method, comprising:

performing an exposure step according to a predetermined time, thereby obtaining a light sensitivity;

performing a time adjustment step according to the light sensitivity, thereby adjusting the predetermined time and obtaining an adjusted time; and

replacing the predetermined time with the adjusted time, and repeatedly performing the exposure step and the time adjustment step until the adjusted time converges within a predetermined range;

wherein the predetermined time is a predetermined lag time for shutting down a mechanical shutter.

2. The method of claim 1 , wherein the exposure step comprises:

performing an image capture step of a capture mode according to a predetermined light sensitivity and the predetermined time, thereby obtaining a capture-mode image having a capture-mode light sensitivity gain value; and

adjusting the capture-mode light sensitivity gain value and repeating the image capture step of the capture mode until the capture-mode image reaches a capture-mode brightness target value.

3. The method of claim 2 , further comprising:

when the capture-mode image reaches the capture-mode brightness target value, recording the capture-mode light sensitivity gain value in a light sensitivity gain table.

4. The method of claim 2 , wherein in the image capture step of the capture mode, the mechanical shutter is used to control an exposure time in the exposure step.

5. The method of claim 1 , wherein the exposure step comprises:

performing an image capture step of a preview mode according to a predetermined light sensitivity and the predetermined time, thereby obtaining a preview-mode image having a preview-mode light sensitivity gain value; and

adjusting the preview-mode light sensitivity gain value and repeating the image capture step of the preview mode until the preview-mode image reaches a preview-mode brightness target value.

6. The method of claim 5 , further comprising:

when the preview-mode image reaches the preview-mode brightness target value, recording the preview-mode light sensitivity gain value in a light sensitivity gain table.

7. The method of claim 5 , wherein in the image capture step of the preview mode, an electronic shutter is used to control an exposures time in the exposure step.

8. The method of claim 1 , wherein the time adjustment step comprises:

obtaining a capture-mode image and a preview-mode image according to the light sensitivity; and

adjusting the predetermined time and repeatedly obtaining the capture-mode image and the preview-mode image, until the absolute brightness difference between the capture-mode image and the preview-mode image is less than a threshold.

9. The method of claim 1 , wherein the adjusted time converges when an absolute difference between the current adjusted time and the predetermined time is less than a predetermined value.

10. An imaging device, comprising:

an image sensing element that converts a light signal to a corresponding electric signal;

a shutter that controls exposure of the image sensing element in a preview mode or a capture mode; and

an operating center that performs an exposure step according to a predetermined time, thereby obtaining a light sensitivity, and that performs a time adjustment step according to the light sensitivity, thereby adjusting the predetermined time and obtaining an adjusted time; and that replaces the predetermined time with the adjusted time, and that repeatedly performs the exposure step and the time adjustment step until the adjusted time converges within a predetermined range;

wherein the predetermined time comprises a predetermined lag time for shutting down a mechanical shutter.

11. The device of claim 10 , further comprising a storage unit that stores the predetermined time, the light sensitivity, and the adjusted time.

12. The device of claim 10 , wherein the light sensitivity corresponds to a capture-mode light sensitivity gain value or a preview-mode light sensitivity gain value.

13. The device of claim 12 , wherein the exposure step comprises:

performing an image capture step of the capture mode according to a predetermined light sensitivity and the predetermined time, thereby obtaining a capture-mode image and the capture-mode light sensitivity gain value;

adjusting the capture-mode light sensitivity gain value and repeating the image capture step of the capture mode until the capture-mode image reaches a capture-mode brightness target value;

performing an image capture step of the preview mode according to the predetermined light sensitivity and the predetermined time, thereby obtaining a preview-mode image and the preview-mode light sensitivity gain value; and

adjusting the preview-mode light sensitivity gain value and repeating the image capture step of the preview mode until the preview-mode image reaches a preview-mode brightness target value.

14. The device of claim 13 , wherein the operating center constructs a light sensitivity gain table according to the capture-mode light sensitivity gain value and the preview-mode light sensitivity gain value.

15. The device of claim 10 , wherein the time adjustment step comprises:

obtaining a capture-mode image and a preview-mode image according to the light sensitivity; and

adjusting the predetermined time and repeatedly obtaining the capture-mode image and the preview-mode image, until the absolute brightness difference between the capture-mode image and the preview-mode image is less than a threshold.

16. The device of claim 10 , wherein the adjusted time is determined by the operating center to be convergent when an absolute difference between the current adjusted time and the predetermined time is less than a predetermined value.

17. The device of claim 10 , wherein the shutter comprises an electronic shutter or the mechanical shutter, the electronic shutter controlling the exposure of the image sensing element in the preview mode, and the mechanical shutter controlling the exposure of the image sensing element in the capture mode.

18. The device of claim 10 , wherein the imaging device comprises a digital system.