Image sensor having multiple sensing layers

1. An image sensor, comprising:

a first sensor layer having a first array of pixels; and

a second sensor layer having a second array of pixels,

wherein each of the pixels having an optical center,

wherein the first sensor layer is stacked over the second sensor layer such that the optical centers of the first array of pixels are offset from the optical centers of the second array to form a predetermined pattern,

wherein the first array of pixels has a first spatial pitch in a first direction and a second spatial pitch in a second direction, and

wherein the first spatial pitch is larger than the second spatial pitch.

2. The image sensor of claim 1 , wherein

the second array of pixels has a first spatial pitch in the first direction and a second spatial pitch in the second direction, wherein the second spatial pitch is larger than the first spatial pitch.

3. The image sensor of claim 1 , wherein each pixel includes a photodetector for collecting charge in response to incident light, a charge-to-voltage conversion mechanism, and a transfer gate for selectively transferring charge from the photodetector to the charge-to-voltage mechanism.

4. The image sensor of claim 1 , further comprising an alignment structure for measuring the offset and rotational misalignment between the first sensor layer and second sensor layer.

5. The image sensor of claim 1 , wherein each pixel includes a photodetector for collecting charge in response to incident light, and wherein a plurality of photodetectors are connected to a common charge-to-voltage mechanism.

6. The image sensor of claim 1 , further comprising a color filter array situated over the first sensor layer.

7. The image sensor of claim 1 , wherein the image sensor is a back illuminated sensor.

8. The image sensor of claim 1 , further comprising a third sensor layer having a third array of pixels, wherein the optical centers of the third array of pixels are offset from the optical centers of the first and second arrays.

9. The image sensor of claim 8 , further comprising a third sensor layer having a third array of pixels, the third array having a third spatial pitch in a third direction.

10. The image sensor of claim 1 , wherein the first and second sensor layers each have first and second effective thicknesses, respectively, to collect light with first and second preselected ranges of wavelengths, respectively.

11. The image sensor of claim 1 , wherein the first and second arrays of pixels are arranged such that the predetermined pattern is a square lattice.

12. The image sensor of claim 1 , wherein the first and second arrays of pixels are arranged such that the predetermined pattern is a close-packed lattice.

13. A image sensing method, comprising:

providing a first sensor layer having a first array of pixels;

providing a second sensor layer having a second array of pixels;

wherein each of the pixels has an optical center, and wherein the first sensor layer is stacked over the second sensor layer such that the optical centers of the first array of pixels are offset from the optical centers of the second array to form a predetermined pattern;

capturing first and second images by the first and second sensor layers, respectively; and

combining the first and second images into a final image,

wherein the first array of pixels has a first spatial pitch in a first direction and a second spatial pitch in a second direction, and

wherein the first spatial pitch is larger than the second spatial pitch.

14. The method of claim 13 , wherein

the second array has a first spatial pitch in the first direction and a second spatial pitch in the second direction, wherein the second spatial pitch is larger than the first spatial pitch.

15. The method of claim 13 , further comprising providing an alignment structure for measuring the offset and rotational misalignment between the first sensor layer and second sensor layer.

16. The method of claim 13 , further comprising providing a third sensor layer having a third array of pixels.

17. A method of producing an image sensor, comprising:

forming a first array of pixels on a first sensor layer;

forming a second array of pixels on a second sensor layer; and

stacking the first sensor layer over the second sensor layer such that optical centers of the first array of pixels are offset from optical centers of the second array to form a predetermined pattern,

wherein the first array of pixels has a first spatial pitch in a first direction and a second spatial pitch in a second direction, and

wherein the first spatial pitch is larger than the second spatial pitch.

18. The method of claim 17 , further comprising forming a color filter array over the first sensor layer.

19. The method of claim 17 , further comprising:

forming a third sensor layer having a third array of pixels; and

stacking the first, second and third sensor layers such that optical centers of the third array of pixels are offset from the optical centers of the first and second arrays.

20. The method of claim 17 , wherein

the second array of pixels has a first spatial pitch in the first direction and a second spatial pitch in the second direction, wherein the second spatial pitch is larger than the first spatial pitch.

21. The method of claim 17 , further comprising:

forming an opening in the first sensor layer;

capturing an image by the second sensor layer created by light coming through the opening in the first sensor layer; and

using the captured image to measure misalignment between the first sensor layer and the second sensor layer.

22. The method of claim 17 , wherein the first and second arrays of pixels are arranged such that the predetermined pattern is a square lattice.

23. The method of claim 17 , wherein the first and second arrays of pixels are arranged such that the predetermined pattern is a close-packed lattice.