Optical biometric sensor with automatic gain and exposure control

1. An optical imaging device for imaging a biometric input object, comprising:

an optical sensor array including an array of sensing elements; and

a control circuit,

wherein the control circuit is configured to:

first read a first subset of sensing elements in the array of sensing elements, wherein the first subset of sensing elements comprises masked sensing elements;

analyze the first read of the first subset of sensing elements to determine an ambient light condition;

first alter an operating point of the optical imaging device based on the ambient light condition; and

image the input object.

2. The optical imaging device of claim 1 , wherein the control circuit is configured to alter the operating point by adjusting at least one of a gain or an exposure time.

3. The optical imaging device of claim 2 , wherein the control circuit is configured to adjust the at least one of the gain or the exposure time to values corresponding to imaging the biometric input object in bright light.

4. The optical imaging device of claim 2 , wherein the control circuit is further configured to:

second read the first subset of sensing elements following the first alter of the operating point and prior to the image the input object.

5. The optical imaging device of claim 1 , wherein the first subset of sensing elements comprises a plurality of spaced apart rows of the optical sensor array.

6. The optical imaging device of claim 5 , wherein the spaced apart rows include sensing elements disposed proximate to edges and a center of the optical sensor array.

7. The optical imaging device of claim 1 , further comprising a collimator disposed above the optical sensor array.

8. An optical imaging device for imaging a biometric input object, comprising:

an optical sensor array, the optical sensor array comprising:

a plurality of unmasked sensing elements, the plurality of unmasked sensing elements being configured to image an input object;

a plurality of masked sensing elements including:

a first sensing element disposed below a first spatial light blocking mask, the first spatial light blocking mask configured to allow a first amount of light to reach a sensing area of the first sensing element; and

a second sensing element disposed below a second spatial light blocking mask, the second spatial light blocking mask configured to allow a second amount of light to reach a sensing area of the second sensing element,

wherein the first amount of light is different from the second amount of light.

9. The optical imaging device of claim 8 , further comprising a light filter layer above the optical sensor array, wherein the light filter layer comprises a collimator having a plurality of apertures, a first aperture being disposed above the first sensing element and a second aperture being disposed above the second sensing element.

10. The optical imaging device of claim 9 , wherein the first spatial light blocking mask is disposed within the first aperture and the second light blocking mask is disposed within the second aperture.

11. The optical imaging device of claim 9 , wherein the first spatial light blocking mask and the second spatial light blocking mask are disposed above the optical sensor array and below the light filter layer.

12. The optical imaging device of claim 8 , wherein the first spatial light blocking mask comprises blocking material forming a first gap and the second spatial light blocking mask comprises blocking material forming a second gap, the first and second gaps permitting transmission of light therethrough and the second gap being narrower than the first gap.

13. The optical imaging device of claim 8 , wherein the first spatial light blocking mask and the second spatial light blocking masks comprise filter material that permits transmission of light of certain wavelengths and blocks transmission of light of other wavelengths.

14. The optical imaging device of claim 8 , wherein the first sensing element and the second sensing element are disposed proximate to edges of the optical sensor array.

15. The optical imaging device of claim 8 , wherein the second sensing element is disposed proximate to a center of the optical sensor array.

16. A method of imaging a biometric input object using an optical sensor array having a plurality of optical sensing elements, comprising:

first reading a subset of sensing elements in the optical sensor array, wherein the subset of sensing elements comprises masked sensing elements;

analyzing the first reading of the subset of sensing elements to determine an ambient light condition;

altering an operating point based on the ambient light condition; and

imaging the biometric input object using the optical sensor array.

17. The method of claim 16 , wherein the altering the operating point comprises adjusting at least one of gain or exposure of the optical sensor array.

18. The method of claim 16 , wherein the subset of sensing elements further comprises unmasked sensing elements.

19. The method of claim 16 , wherein the masked sensing elements include:

a first sensing element disposed below a first spatial light blocking mask, the first spatial light blocking mask configured to allow a first amount of light to reach a sensing area of the first sensing element; and

a second sensing element disposed below a second spatial light blocking mask, the second spatial light blocking mask configured to allow a second amount of light to reach a sensing area of the second sensing element,

wherein the first amount of light is different from the second amount of light.

20. The method of claim 16 , wherein the subset of sensing elements are configured to receive light through a collimator.

21. The method of claim 16 , further comprising:

second reading the subset of sensing elements in the optical sensor array after altering the operating point and before imaging the biometric input object.

22. The method of claim 16 , wherein at least some of the subset of sensing elements are disposed proximate to edges of the optical sensor array.

23. The method of claim 16 , wherein at least some of the subset of sensing elements are disposed proximate to a center of the optical sensor array.