CMOS image sensors with per-pixel micro-lens arrays

1. An image sensor, comprising:

an array of CMOS pixels;

a plurality of micro-lens arrays disposed on a planar surface above the array of CMOS pixels, wherein:

each micro-lens array of the plurality of micro-lens arrays comprises a plurality of horizontally adjacent micro-lenses, and

each micro-lens array of the plurality of micro-lens arrays is situated above a respective CMOS pixel in an interior region of the array of CMOS pixels; and

a plurality of per-pixel micro-lenses disposed on the planar surface and situated above respective CMOS pixels in an edge region of the array of CMOS pixels such that there is only one per-pixel micro-lens situated above each CMOS pixel in the edge region.

2. The image sensor of claim 1 , wherein:

the CMOS pixels in the array of CMOS pixels have a first pitch;

the micro-lens arrays in the plurality of micro-lens arrays have the first pitch; and

the plurality of horizontally adjacent micro-lenses within each micro-lens array of the plurality of micro-lens arrays have a second pitch that is smaller than the first pitch.

3. The image sensor of claim 1 further comprising a plurality of color-filter arrays, wherein each color-filter array of the plurality of color-filter arrays (i) is situated above a respective CMOS pixel in the interior region of the array of CMOS pixels and below a respective micro-lens array of the plurality of micro-lens arrays and (ii) comprises a respective plurality of horizontally adjacent color filters.

4. The image sensor of claim 3 , wherein:

the respective plurality of color filters for each color-filter array is of the same color, and

the plurality of color-filter arrays comprises color-filter arrays of different colors, in accordance with a color scheme.

5. The image sensor of claim 4 , wherein the color scheme is the Bayer color scheme, the different colors being red, green, and blue.

6. The image sensor of claim 3 , further comprising passivation and anti-reflective coating situated above the array of CMOS pixels and below the plurality of color-filter arrays.

7. The image sensor of claim 3 , further comprising a metal grid to divide each color-filter array of the plurality of color-filter arrays into the plurality of horizontally adjacent color filters, the metal grid being situated above the array of CMOS pixels and below the plurality of micro-lens arrays.

8. The image sensor of claim 1 , wherein respective micro-lens arrays of the plurality of micro-lens arrays comprise four-by-four arrays of micro-lenses.

9. The image sensor of claim 1 , wherein a respective micro-lens array of the plurality of micro-lens arrays comprises:

multiple horizontally adjacent micro-lenses of a first size along edges of the micro-lens array; and

one or more micro-lenses of a second size in the interior of the micro-lens array, wherein the second size is larger than the first size and the one or more micro-lenses of the second size are horizontally adjacent to the multiple horizontally adjacent micro-lenses of the first size.

10. The image sensor of claim 1 , wherein a respective micro-lens array of the plurality of micro-lens arrays comprises:

asymmetrical horizontally adjacent micro-lenses along edges of the micro-lens array; and

symmetrical horizontally adjacent micro-lenses in the interior of the micro-lens array,

wherein the asymmetrical horizontally adjacent micro-lenses are horizontally adjacent to the symmetrical horizontally adjacent micro-lenses.

11. The image sensor of claim 1 , wherein respective CMOS pixels in the array of CMOS pixels each comprise:

a photo-carrier collection region; and

deep-trench isolation on sides of the CMOS pixel to reflect light into the photo-carrier collection region.

12. The image sensor of claim 11 , wherein, in a micro-lens array situated above a respective CMOS pixel that includes the photo-carrier collection region and the deep-trench isolation, the plurality of horizontally adjacent micro-lenses are symmetrical.

13. The image sensor of claim 1 , wherein the edge region of the array of CMOS pixels encloses the interior region of the array of CMOS pixels.

14. The image sensor of claim 1 , wherein a first micro-lens array of the plurality of micro-lens arrays is situated above a first pixel in the array of CMOS pixels and is offset horizontally from the first pixel.

15. The image sensor of claim 1 , wherein respective micro-lens arrays of the plurality of micro-lens arrays have respective, varying degrees of horizontal offset from respective pixels in the array of CMOS pixels.

16. The image sensor of claim 1 , wherein the interior region includes pixels that are more than a predetermined number of pixels from an outside edge of the array of CMOS pixels, and the edge region includes pixels that are less than the predetermined number of pixels from the outside edge of the array of CMOS pixels.