Seamless readout mode transitions in image sensors

1. A method of operating an image sensor comprising an array of photosites, the method comprising:

applying a readout signal to a first group of photosites defined by a readout pointer;

applying a reset signal, in phase with the readout signal, to a second group of photosites defined by a reset pointer;

incrementing the readout pointer at a first scan rate; and

incrementing the reset pointer at a second scan rate;

wherein the first scan rate is different from the second scan rate.

2. The method of claim 1 , wherein:

the readout pointer is associated with a first frame; and

the reset pointer is associated with a second frame.

3. The method of claim 2 , wherein the first frame and the second frame are sequential.

4. The method of claim 2 , wherein:

the readout pointer is a first readout pointer; and

the method comprises incrementing a second readout pointer associated with the second frame at the second scan rate.

5. The method of claim 1 , wherein the first scan rate is faster than the second scan rate.

6. The method of claim 5 , wherein incrementing the reset pointer comprises skipping an increment of the reset pointer.

7. The method of claim 1 , wherein the second scan rate is faster than the first scan rate.

8. The method of claim 7 , wherein:

the first group of photosites comprises one row of photosites of the array of photosites; and

the second group of photosites comprise more than one row of photosites of the array of photosites.

9. The method of claim 1 , wherein:

the first scan rate is associated with a first readout mode of the image sensor; and

the second scan rate is associated with a second readout mode of the image sensor.

10. The method of claim 9 , wherein:

the first readout mode is associated with a first line time; and

the second readout mode is associated with a second line time different from the first line time.

11. An image sensor comprising:

a photosite array; and

a controller configured to:

apply a readout signal associated with a readout pointer to a first group of photosites of the photosite array;

apply a reset signal associated with a reset pointer, in phase with the readout signal, to a second group of photosites of the photosite array;

increment the readout pointer at a first scan rate; and

increment the reset pointer at a second scan rate different from the first scan rate.

12. The image sensor of claim 11 , wherein the first scan rate is faster than the second scan rate.

13. The image sensor of claim 11 , wherein:

the second scan rate is faster than the first scan rate; and

the controller is configured to delay incrementing of the reset pointer to prevent the reset pointer from overtaking the readout pointer.

14. The image sensor of claim 11 , wherein:

the first group of photosites comprises a first row of photosites of the photosite array; and

the second group of photosites comprises a second row of photosites of the photosite array.

15. The image sensor of claim 11 , wherein:

the readout signal is associated with a first frame;

the reset signal is associated with a second frame; and

the first frame and the second frame are sequential.

16. The image sensor of claim 11 , wherein:

the first group of photosites is one row of photosites of the array of photosites; and

the second group of photosites comprises more than one row of photosites of the array of photosites.

17. A method of transitioning between readout modes of an image sensor comprising an array of photosites, the method comprising:

defining a readout pointer and a first scan rate associated with a first readout mode;

defining a reset pointer and a second scan rate associated with a second readout mode;

applying, based on the readout pointer, a readout signal to a first group of photosites of the array of photosites;

applying, based on the reset pointer, a reset signal to a second group of photosites of the array of photosites;

incrementing the readout pointer at the first scan rate; and

incrementing the reset pointer at the second scan rate; wherein

the first scan rate is different from the second scan rate; and

the reset signal is applied in phase with the readout signal.

18. The method of claim 17 , wherein:

the first group of photosites comprises one row of photosites of the array of photosites; and

the second group of photosites comprises two or more rows of photosites of the array of photosites.

19. The method of claim 17 , wherein:

the first readout mode is a binning readout mode; and

the second readout mode is a full-resolution readout mode.

20. The method of claim 17 , wherein:

the readout pointer is associated with a first frame;

the reset pointer is associated with a second frame; and

the first frame and the second frame are sequential.