Biometric imaging with hover detection

1. A method of imaging a fingerprint of a finger in an electronic device including a display, a touch sensor having a touch interface, and an optical fingerprint sensor having a sensing region, the method comprising:

placing the electronic device in a hover detect mode, the hover detect mode scanning for the finger hovering proximate to the touch interface;

detecting the finger while the finger is hovering;

initiating illumination in the sensing region;

capturing an image of the fingerprint of the finger in the sensing region; and

disabling the illumination in the sensing region.

2. The method of claim 1 , wherein the initiating illumination in the sensing region comprises initiating a high brightness mode (HBM) of display pixels proximate to the sensing region in response to detecting the finger.

3. The method of claim 2 , wherein a transition to the HBM is synchronized with a rate of approach of the finger.

4. The method of claim 2 , wherein the sensing region and the display pixels are in a region of the display determined from a location of the finger.

5. The method of claim 3 , wherein in the rate of approach of the finger is an assumed value.

6. The method of claim 3 , wherein the rate of approach of the finger is based on an amplitude of a signal received in connection with the detecting the finger while the finger is hovering.

7. The method of claim 1 , further comprising:

adjusting the display outside of the sensing region in response to detecting the finger while the finger is hovering.

8. The method of claim 7 , further comprising:

placing the display outside of the sensing region in a dark background mode (DBM).

9. The method of claim 8 , wherein the display outside of the sensing region fades to the DBM.

10. The method of claim 9 , wherein a rate of fade to the DBM is synchronized with a rate of approach of the finger.

11. The method of claim 7 , further comprising iteratively adjusting display pixel values outside of the sensing region to compensate for an increase in current to the display.

12. The method of claim 1 , further comprising

displaying a guide for placement of the fingerprint after detecting the finger while the finger is hovering.

13. The method of claim 12 , wherein the displaying the guide occurs before a HBM is fully realized.

14. The method of claim 1 , wherein the detecting the finger, comprises:

first detecting the finger hovering proximate to the touch interface; and

second detecting the finger hovering proximate to the sensing region.

15. The method of claim 1 , further comprising:

detecting contact between the finger and the touch interface before the capturing the image of the fingerprint.

16. The method of claim 15 , wherein pressure is sensed to facilitate the detecting contact between the finger and the touch interface.

17. The method of claim 1 , wherein the capturing the image of the fingerprint is in response to detecting a valid touch.

18. An electronic device, comprising:

a memory; and

one or more processors in communication with the memory, wherein the one or more processors are configured to:

operate the electronic device in a hover detect mode, the hover detect mode scanning for a finger hovering proximate to a touch interface;

receive a signal when the finger hovering proximate to the touch interface is detected;

initiate illumination in a sensing region of an optical sensor;

receive image data corresponding to an image of a fingerprint of the finger from the sensing region; and

disable the illumination in the sensing region.

19. The electronic device of claim 18 , wherein the one or more processors include a host processor of the electronic device.

20. The electronic device of claim 19 , wherein the one or more processors include a touch controller.

21. The electronic device of claim 18 , wherein the one or more processors are further configured to initiate the illumination in the sensing region using a high brightness mode (HBM).

22. The electronic device of claim 21 , wherein a transition to the HBM is synchronized with a rate of approach of the finger.

23. The electronic device of claim 18 , wherein the one or more processors are further configured to:

adjust a display outside of the sensing region after detecting the finger hovering.

24. The electronic device of claim 23 , wherein the one or more processors are further configured to:

place the display outside of the sensing region in a dark background mode (DBM).

25. The electronic device of claim 24 , wherein the display outside of the sensing region fades to the DBM.

26. The electronic device of claim 25 , wherein a rate of fade to the DBM is synchronized with a rate of approach of the finger.

27. The electronic device of claim 23 , wherein the one or more processors are further configured to:

iteratively adjust pixel values outside of the sensing region to compensate for an increase in current to the display.

28. The electronic device of claim 18 , wherein the one or more processors are further configured to:

display a guide for placement of the fingerprint after detecting the hovering finger.

29. An electronic device, comprising:

a memory; and

a touch controller in communication with the memory, configured to:

operate in a hover detect mode, the hover detect mode scanning for a finger hovering proximate to a touch interface;

detect the finger while the finger is hovering proximate to the touch interface;

first signal that the finger has been detected to initiate illumination in a sensing region of an optical sensor;

second signal to disable the illumination in the sensing region after capturing an image of a fingerprint of the finger.

30. The electronic device of claim 29 , wherein the touch controller is further configured to initiate the illumination in the sensing region using a high brightness mode (HBM).

31. The electronic device of claim 30 , wherein a transition to the HBM is synchronized with a rate of approach of the finger.

32. The electronic device of claim 29 , wherein the touch controller is further configured to:

adjust a display outside of the sensing region after detecting the finger while the finger is hovering.

33. The electronic device of claim 32 , wherein the touch controller is further configured to:

place the display outside of the sensing region in a dark background mode (DBM).