Image Sensor Microlens Area Variation for Crosstalk Reduction
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Solution Overview
Problem
Existing image sensors suffer from crosstalk due to light refraction by microlenses, which is more pronounced at pixel edges and outermost pixels, degrading image quality.
Innovation Solution
The image sensor design includes a semiconductor substrate with central and peripheral pixel regions, where color filters and microlenses are arranged to match incident light angles, reducing crosstalk by ensuring light is directed accurately to corresponding photodiodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If microlenses have the same area as color filters and use a convex lens shape to condense incident light, then light condensation efficiency is improved, but crosstalk is generated between adjacent photodiodes
Solution Approach 1:
The patent applies local quality by differentiating microlens parameters across different spatial locations. Central region microlenses have a first area and first focal length, while peripheral region microlenses have a second area and second focal length. This local differentiation allows optimal light condensation in the center while reducing crosstalk at the periphery where incident light angles are more oblique.
Solution Approach 2:
The patent changes microlens parameters (area and focal length) based on spatial position. By adjusting these parameters from the central region to the peripheral region, the system optimizes light condensation efficiency while minimizing crosstalk generation at pixel edges where oblique incident light is more prevalent.
2Ease of manufacture
If microlenses are arranged with the same area as color filters, then manufacturing simplicity is improved, but light is refracted to adjacent photodiodes causing crosstalk
Solution Approach 1:
The patent divides the image sensor into central and peripheral regions with different microlens specifications. This local quality approach maintains manufacturing feasibility through standardized processes while introducing regional variations in microlens area and focal length to prevent crosstalk at pixel edges.
3Area of stationary object
If pixel edges and outermost pixels are used in the image sensor, then image coverage area is improved, but crosstalk is frequently generated due to greater light incident slope
Solution Approach 1:
The patent addresses peripheral pixel crosstalk by providing microlenses in the peripheral region with different parameters (area and focal length) compared to central region microlenses. This local adaptation compensates for the greater obliquity of incident light at pixel edges, maintaining image coverage while reducing crosstalk.
Solution Approach 2:
The patent changes microlens parameters specifically in the peripheral region where oblique incident light causes crosstalk. By adjusting area and focal length parameters for peripheral microlenses, the system maintains full image coverage while mitigating the crosstalk problem inherent to edge pixels.
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 effectively reduces or eliminates crosstalk, enhancing image quality by minimizing light interference at pixel edges and outermost pixels.
Implementation Method 1
light incident to the microlenses is refracted by the microlenses, passes through the color filters, and can be incident to adjacent photodiodes
Data Source
AI summary
Provided is an image sensor. The image sensor includes a semiconductor substrate, photodiode structures, color filters, and microlenses. The semiconductor substrate includes a first region having pixel regions and a second region around the first region. The pixel regions are arranged in a matrix configuration. Each of the photodiode structures has a photodiode in each of the pixel regions. The color filters are disposed on or over the photodiode structures, the color filters correspond to the pixel regions, respectively, and have different areas corresponding to incident angles of light.