Image sensor capable of eliminating rolling flicker and adjusting frame rate

1. An image sensor, configured to acquire image frames with a frame period, the image sensor comprising:

a pixel array configured to output a first image frame and a second image frame, wherein the pixel array is exposed using a rolling shutter; and

a processor configured to

calculate a first bright-dark distribution pattern of the first image frame,

calculate a second bright-dark distribution pattern of the second image frame,

calculate a normalized difference distribution between the first bright-dark distribution pattern and the second bright-dark distribution pattern, and

confirm existence of rolling flickers when the normalized difference distribution fluctuates between positive and negative values and has a fluctuation amplitude larger than an amplitude threshold.

2. The image sensor as claimed in claim 1 , wherein the first image frame and the second image frame are two adjacent image frames or two image frames separated by at least one another image frame.

3. The image sensor as claimed in claim 1 , wherein

the first bright-dark distribution pattern is a distribution of a summation or an average of gray values of every pixel row of the first image frame, and

the second bright-dark distribution pattern is a distribution of a summation or an average of gray values of every pixel row of the second image frame.

4. The image sensor as claimed in claim 1 , wherein the processor is further configured to confirm the existence of the rolling flickers when the normalized difference distribution and has a fluctuation time smaller than a predetermined number of times.

5. The image sensor as claimed in claim 1 , wherein the processor is configured to calculate a similarity or a correlation between the first bright-dark distribution pattern and the second bright-dark distribution pattern to calculate the normalized difference distribution.

6. The image sensor as claimed in claim 1 , wherein

the frame period comprises line times of multiple valid pixel rows, line times of multiple dummy pixel rows and line times of multiple dark pixel rows, and

the processor is further configured to adjust a number of the line times of multiple dummy pixel rows when a difference between the first bright-dark distribution pattern and the second bright-dark distribution pattern is larger than a difference threshold.

7. An image sensor, configured to acquire image frames with a frame period, the image sensor comprising:

a pixel array configured to output a first image frame and a second image frame, wherein the pixel array is exposed using a rolling shutter, and the frame period comprises line times of multiple valid pixel rows and line times of multiple dummy pixel rows; and

a processor configured to

calculate a first bright-dark distribution pattern of the first image frame,

calculate a second bright-dark distribution pattern of the second image frame, and

adjust a blank time according to a difference between the first bright-dark distribution pattern and the second bright-dark distribution pattern.

8. The image sensor as claimed in claim 7 , wherein the first image frame and the second image frame are two adjacent image frames or two image frames separated by at least one another image frame.

9. The image sensor as claimed in claim 7 , wherein

the first bright-dark distribution pattern is a distribution of a summation or an average of gray values of every pixel row of the first image frame, and

the second bright-dark distribution pattern is a distribution of a summation or an average of gray values of every pixel row of the second image frame.

10. The image sensor as claimed in claim 7 , wherein the processor is configured to calculate a similarity or a correlation between the first bright-dark distribution pattern and the second bright-dark distribution pattern to adjust the blank time.

11. The image sensor as claimed in claim 10 , wherein the processor is further configured to calculate similarities and correlations between the first bright-dark distribution pattern and the second bright-dark distribution pattern when the first and second image frames are separated by different numbers of image frames to obtain a separated number corresponding to a smallest similarity or a smallest correlation.

12. The image sensor as claimed in claim 7 , further comprising a clock generator configured to generate a clock signal to count each of the line times of multiple valid pixel rows and the line times of multiple dummy pixel rows, wherein the processor is configured to not adjust a clock frequency of the clock signal while adjusting the blank time.

13. The image sensor as claimed in claim 12 , wherein the processor is configured to adjust the blank time by adjusting at least one of

a number of the line times of multiple dummy pixel rows,

a number of times of counting the blank time by the clock signal, and

a period of a horizontal synchronization signal within the blank time.

14. An image sensor, configured to acquire image frames with a frame period, the image sensor comprising:

a pixel array configured to output successive image frames using a rolling shutter, wherein the frame period of the image frames comprises line times of multiple valid pixel rows and line times of multiple dummy pixel rows;

a clock generator configured to use a clock frequency to count each of the line times of multiple valid pixel rows and the line times of multiple dummy pixel rows; and

a processor configured to adjust a blank time to compensate a deviation of the frame period caused by a clock frequency shift when the clock frequency of the clock generator is changed by a temperature variation.

15. The image sensor as claimed in claim 14 , wherein the processor is configured to identify whether the clock frequency is changed according to bright-dark distribution patterns of different image frames.

16. The image sensor as claimed in claim 15 , wherein the processor is configured to calculate a similarity or a correlation of the bright-dark distribution patterns of the different image frames to identify whether the clock frequency is changed.

17. The image sensor as claimed in claim 15 , wherein the processor is configured to calculate a normalized difference distribution between the bright-dark distribution patterns of the different image frames to identify whether the clock frequency is changed.

18. The image sensor as claimed in claim 15 , wherein the processor is further configured to change a separated number of image frames between the different image frames while identifying whether the clock frequency is changed.

19. The image sensor as claimed in claim 14 , wherein

when the clock frequency is increased, the processor is configured to increase the blank time; and

when the clock frequency is decreased, the processor is configured to decrease the blank time.

20. An image sensor, configured to acquire image frames with a frame period, the image sensor comprising:

a pixel array configured to output a first image frame and a second image frame, wherein the pixel array is exposed using a rolling shutter; and

a processor configured to

calculate a first bright-dark distribution pattern of the first image frame,

calculate a second bright-dark distribution pattern of the second image frame, and

compare the first bright-dark distribution pattern and the second bright-dark distribution pattern to confirm existence of rolling flickers, wherein

the frame period comprises line times of multiple valid pixel rows, line times of multiple dummy pixel rows and line times of multiple dark pixel rows, and

the processor is further configured to adjust a number of the line times of multiple dummy pixel rows when a difference between the first bright-dark distribution pattern and the second bright-dark distribution pattern is larger than a difference threshold.