Method and system of self-calibration for phase detection autofocus

1. A computer-implemented method of autofocus self-calibration comprising:

receiving, at an imaging device, initial phase detection autofocus (PDAF) calibration data with the same values to be provided to multiple imaging devices;

capturing, by the imaging device, a plurality of images;

generating, by the imaging device, device-specific PDAF calibration data comprising refining PDAF calibration data by using the plurality of images; and

providing the device-specific PDAF calibration data to be used to obtain, by the imaging device, image data of multiple subsequent images.

2. The method of claim 1 wherein the initial and device-specific PDAF calibration data comprises or is based on at least one conversion factor used to convert phase shifts to lens offsets.

3. The method of claim 2 wherein the imaging device has a sensor having a plurality of sensor pixels providing image data divided into regions of interest, and the method comprising generating a conversion factor for each region of interest.

4. The method of claim 1 wherein generating device-specific PDAF calibration data comprises using a phase shift of individual regions of interest (ROIs), wherein each ROI having a plurality of sensor pixels comprising at least one PDAF sensor pixel pair forming a phase difference contributing to generating the phase shift of the ROI.

5. The method of claim 4 comprising using a reliability value of individual ROIs to determine whether or not an ROI is to be used to generate the device-specific PDAF calibration data.

6. The method of claim 5 wherein the reliability value is based on analysis of a curve formed of candidate phase shift values and accumulated phase differences of the PDAF sensor pixel pairs of the individual ROIs.

7. The method of claim 1 wherein generating device-specific PDAF calibration data comprises determining whether or not to use an ROI to generate the device-specific PDAF calibration data comprising determining if the image data of an ROI of a current image is sufficiently unchanged from the image data of the same ROI on a last image used to generate PDAF calibration data.

8. The method of claim 1 wherein generating device-specific PDAF calibration data comprising:

performing multiple autofocus iterations comprising moving a lens of the image capture device to an iteration lens position for individual iterations;

determining a focus lens position on one of the iterations of the multiple autofocus iterations;

determining an iteration focus lens offset for the individual iterations and that indicates the lens offset from the iteration lens position to the focus lens position; and

using an iteration phase shift established as a result of the iteration lens position and the iteration focus lens offset to generate a phase shift to lens offset conversion factor and of each of the individual iterations prior to the iteration establishing the focus lens offset.

9. The method of claim 8 comprising replacing or adjusting the initial PDAF calibration data with the conversion factor or PDAF sample-specific calibration data based on the conversion factor when the conversion factor is sufficiently similar or the same on multiple ones of the individual iterations, and the conversion factor is obtained at each of a predetermined number of rounds each round having an iteration establishing the focus lens position and having a plurality of the individual iterations.

10. The method of claim 9 comprising providing a conversion factor of each region of interest (ROI) of a sensor of the imaging device, wherein the sensor is formed of groups of sensor pixels each forming one of the ROIs.

11. The method of claim 8 wherein contrast autofocus is performed during at least some of the individual iterations to obtain the focus lens position.

12. The method of claim 8 wherein the PDAF sample-specific calibration data is a look-up table of phase shifts and corresponding lens offsets based on the conversion factor.

13. The method of claim 1 wherein the generating of the sample-specific PDAF calibration adjustment data is performed at at least one of:

only once starting at the beginning of a first use of the imaging device by an end-user, and

each time the imaging device is turned on.

14. The method of claim 1 wherein the PDAF calibration data comprises a set of left and right shading values formed, at least in part, from pairs of PDAF sensor pixels of a sensor of the imaging device.

15. A system for self-calibration for phase detection autofocus, comprising:

at least one memory to store image data from pairs of phase detection autofocus (PDAF) sensor pixels of a sensor on an imaging device and other PDAF calibration data;

at least one processing unit coupled to the memory; and

a phase detection autofocus unit to operate by:

receiving, at an imaging device, initial phase detection autofocus (PDAF) calibration data with the same values to be provided to multiple imaging devices;

capturing, by the imaging device, a plurality of images;

generating, by the imaging device, device-specific PDAF calibration data comprising iteratively refining PDAF calibration data by using the plurality of images; and

providing the device-specific PDAF calibration data to be used to obtain, by the imaging device, image data of multiple subsequent images.

16. The system of claim 15 , wherein the imaging device comprises at least one sensor comprising a plurality of pairs of PDAF sensor pixels or pixel sides of divided single sensor pixels, and wherein the PDAF calibration data comprises shading statistics formed of a set of first PDAF shading values and a set of second PDAF shading values, each set being from a different one of the two of individual pairs of the PDAF sensor pixels or pixel sides.

17. The system of claim 16 , wherein the shading values are sufficiently calibrated when a predetermined sufficient number of shading values contribute to generate a final combined shading value over iterations wherein each iteration being associated with one of the plurality of the images and one of the shading values.

18. The system of claim 17 , wherein the at least one sensor comprises a plurality of sensor pixels grouped into regions of interest (ROIs) with at least one pair of PDAF sensor pixels or pixel sides being disposed in individual regions of interest, and

wherein the phase detection autofocus unit operates by generating a final combined shading value for individual ROIs.

19. The system of claim 18 , wherein generating device-specific PDAF calibration data is complete when each ROI of the sensor has a final combined shading value.

20. The system of claim 18 , wherein individual final combined shading values are each associated with an average shading value of the shading values in individual ROI and shading values of one of the first and second sets of the PDAF shading values.

21. The system of claim 20 , wherein the final combined shading value of one of the ROIs is an average of an average ROI shading value of a current iteration and average ROI shading value of prior iterations of the same ROI.

22. The system of claim 18 wherein the final combined shading value is an average of the shading values associated with an ROI and of one of the first or second sets of PDAF shading values divided by the average shading value of sensor pixels in the same ROI including non-PDAF sensor pixels if present.

23. The system of claim 18 wherein only those ROIs that are deemed valid are included in the computation to determine a final combined shading value of an ROI, and comprising at least one of:

a test to determine if an ROI is sufficiently bright,

a test to determine if an ROI has sufficiently flat color, and

both.

24. At least one non-transitory machine readable medium comprising a plurality of instructions that in response to being executed on an imaging device, cause the imaging device to be operated by: receiving, at an imaging device, initial phase detection autofocus (PDAF) calibration data with the same values to be provided to multiple imaging devices; capturing, by the imaging device, a plurality of images; generating, by the imaging device, device-specific PDAF calibration data comprising iteratively refining PDAF calibration data by using the plurality of images; and providing the device-specific PDAF calibration data to be used to obtain, by the imaging device, image data of multiple subsequent images.

25. The machine readable medium of claim 24 , wherein the imaging device comprises at least one sensor comprising a plurality of PDAF sensor pixels arranged into regions of interest (ROIs), and

wherein the initial and device-specific PDAF calibration data comprises shading statistics for each ROI and formed of a set of first PDAF shading values and a set of second PDAF shading values, each set being from a different one of pairs of the PDAF sensor pixels or sides of divided single sensor pixels, wherein the shading statistics comprises a shading value formed by dividing the average of one of the sets of shading values in an ROI by the average shading value of all sensor pixels in the ROI including the non-PDAF sensor pixels and of the same color; and

wherein the initial and device-specific PDAF calibration data comprises at least one conversion factor used to convert phase shifts to lens offsets, and for each ROI.