Solid-state image sensor with micro-lenses for anti-shading

Abstract

A solid-state image sensor prevents shading while maintaining the wider dynamic range of an image signal without reducing its optical resolution. The image sensor has plural pairs of higher- and lower-sensitivity photodiodes and micro-lenses each of which is provided over particular one of the higher- and lower-sensitivity photodiodes for collecting the light incident on corresponding one of the higher- and lower-sensitivity photodiodes. The micro-lenses provided over the lower-sensitivity photodiodes have the curvature thereof smaller than that of the other micro-lenses, thereby providing for the lower-sensitivity photodiode a significant amount of light even for a change of the exit pupil position or incident angle or the like that causes the position of an image circle to shift.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic cross-sectional view of part of an array of photodiodes taken along a straight line I shown in FIG. 2;

FIG. 2 is a top plan view schematically showing part of the array of photodiodes of an embodiment of a solid-state image sensor according to the present invention;

FIG. 3 is a top plan view, like FIG. 2, schematically showing part of the array of photodiodes of an alternative embodiment of a solid-state image sensor according to the present invention;

FIG. 4 is schematic cross-sectional view of part of an array of photodiodes of a conventional solid-state image sensor to be compared with the solid-state image sensor according to the present invention;

FIG. 5 schematically illustrates an example of an image circle formed in a lower-sensitivity photodiode in the array of photodiodes of a conventional solid-state image sensor shown in FIG. 4;

FIG. 6 schematically illustrates, like FIG. 5, an example of an image circle formed in a lower-sensitivity photodiode in the array of photodiodes of a solid-state image sensor shown in FIG. 1;

FIGS. 7A and 7B schematically illustrate an exemplified way of fabricating in-layer lenses in the illustrative embodiment; and

FIG. 8 is another schematic cross-sectional view of, like FIG. 1, part of the array of photodiodes taken along a straight line I shown in FIG. 2.

Claims

1. A solid-state image sensor comprising: a plurality of first photodiodes and a plurality of second photodiodes of sensitivity lower than said first photodiodes which are disposed in a virtual plane for receiving light incident from a field of view to be captured;a plurality of first micro-lenses each being provided over particular one of said first photodiodes for collecting the light incident on said particular first photodiode; anda plurality of second micro-lenses each being provided over particular one of said second photodiodes for collecting the light incident on said particular second photodiode, at least one of said second micro-lenses having a curvature smaller than that of said first micro-lenses.

2. The solid-state image sensor in accordance with claim 1, wherein at least one of said second micro-lenses has substantially zero curvature.

3. The solid-state image sensor in accordance with claim 1, further comprising a covering element provided over said first and second micro-lenses for preventing a foreign material from being caught in a space between adjacent ones of said first and second micro-lenses.

4. The solid-state image sensor in accordance with claim 3, wherein said covering element has a refractive index lower than said first and second micro-lenses, and is optically substantially transparent and planar.

5. The solid-state image sensor in accordance with claim 3, wherein said covering element is a film for planarizing the convex or concave of said first and second micro-lenses.

6. The solid-state image sensor in accordance with claim 1, further comprising: a plurality of first in-layer lenses each being provided between corresponding one of said first photodiodes and corresponding one of said first micro-lenses for further collecting the light collected by said first micro-lens on said first photodiode; anda plurality of second in-layer lenses each being provided between corresponding one of said second photodiodes and corresponding one of said second micro-lenses for further collecting the light collected by said second micro-lens on said second photodiode, at least one of said second in-layer lenses having a curvature smaller than that of said first in-layer lens.

7. The solid-state image sensor in accordance with claim 7, wherein said at least one second in-layer lens has substantially zero curvature.