Image Sensor Grid Width Variation for Edge Shading Reduction
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Solution Overview
Problem
Conventional image sensors experience quality loss and shading phenomena near the edges of captured images due to uneven light reception, particularly in backside illumination (BSI) image sensors, where light reception efficiency and sensitivity are compromised.
Innovation Solution
The image sensor design incorporates a light-receiving region with varying pixel and color filter light-receiving areas, where the light-receiving areas of pixels and color filters decrease with distance from the center, and grid patterns with increasing widths towards the edges, to ensure consistent light distribution and reduce shading effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform grid pattern width is used across the entire light-receiving region, then the manufacturing process is simple, but shading phenomena occur at the edges of captured images
Solution Approach 1:
The patent applies local quality by varying the grid pattern width according to position: the grid width increases from the center toward the edges of the light-receiving region. Specifically, the grid pattern in the second region (edge area) has a greater width than the grid pattern in the first region (center area). This local variation compensates for the reduced light intensity at edges, thereby reducing shading phenomena while maintaining manufacturing feasibility.
2Manufacturing precision
If the light-receiving area of color filters is kept uniform across all regions, then the color representation is consistent in theory, but brightness loss occurs near the edges due to geometric shading
Solution Approach 1:
The patent implements local quality by making the light-receiving area of color filters position-dependent. The color filters in the second region (edge area) have a larger light-receiving area compared to those in the first region (center area). This compensates for the geometric shading effect at edges, ensuring more uniform brightness across the entire image while maintaining color accuracy through the Bayer pattern arrangement.
3Object-affected harmful factors
If the grid pattern width is increased at the edges to reduce shading, then image quality at edges improves, but the overall device complexity increases
Solution Approach 1:
The patent applies parameter changes by systematically varying the grid pattern width as a function of position from the center to the edges of the light-receiving region. The grid width parameter increases progressively in the second region compared to the first region. This controlled parameter variation effectively reduces shading phenomena while maintaining a regular, manufacturable pattern structure that does not excessively increase device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances image quality by minimizing shading phenomena and maintaining consistent color ratios across the image, thereby improving the overall brightness and color representation near the edges.
Implementation Method 1
a plurality of photoelectric conversion layers disposed in the substrate and corresponding to the plurality of unit pixels
Data Source
AI summary
An image sensor in which a shading phenomenon is decreased and the quality is increased includes a substrate comprising a first face on which light is incident, and a second face opposite to the first face and a plurality of unit pixels. Each of the plurality of unit pixels includes a photoelectric conversion layer in the substrate. The image sensor further includes a pixel separation pattern which separates unit pixels from the plurality of the unit pixels from each other, a plurality of color filters disposed on the first face of the substrate and arranged in a Bayer pattern, and a grid pattern disposed on the first face of the substrate and interposed within the plurality of color filters. A light-receiving area of the red color filter and a light-receiving area of the blue color filter are smaller than a light-receiving area of the green color filter.