Image Sensor Medium Layer Refractive Index Engineering
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Solution Overview
Problem
Conventional CMOS image sensors exhibit sensitivity differences between the central and edge portions of the pixel array due to varying incident light angles, leading to reduced image quality at the edge portions.
Innovation Solution
The implementation of a medium layer with varying refractive indices, either stacked or replacing the microlens, to refract light and enhance sensitivity at the edge portions, simplifying the manufacturing process by eliminating the need for complex microlens formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a microlens is formed on the color filter to increase sensitivity, then the sensitivity of the image sensor increases, but the manufacturing process becomes more complex
Solution Approach 1:
The patent extracts the light condensing function from the microlens structure and relocates it to a medium layer with varying refractive indices positioned between the color filter and over-coating layer. This separation allows the microlens to be removed while preserving the sensitivity enhancement function through refractive index manipulation alone.
Solution Approach 2:
The patent changes the optical parameter (refractive index) of the medium layer to achieve light condensing effects. By varying the refractive index across the medium layer, the patent creates natural light focusing without requiring physical microlens structures, thus simplifying manufacturing while maintaining sensitivity.
2Ease of manufacture
If the same layer structure is used for both central and edge portions of the pixel array, then manufacturing is simplified, but sensitivity uniformity deteriorates due to different incident light angles
Solution Approach 1:
The patent applies local quality by creating a medium layer with spatially varying refractive indices tailored to specific regions. The refractive index is adjusted differently for central and edge portions of the pixel array, allowing each region to compensate for its specific incident light angle characteristics and achieve uniform sensitivity across the entire array.
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 approach improves sensitivity at the edge portions of the pixel array, enhancing image quality and simplifying the manufacturing process by leveraging the principle of light refraction based on Snell's law.
Implementation Method 1
a medium layer formed on the over-coating layer, wherein the medium layer comprises at least two medium layers having different refractive indices from each other
Data Source
AI summary
An image sensor includes a color filter, an over-coating layer formed on the color filter, and a medium layer formed on the over-coating layer, wherein the medium layer is configured with at least two medium layers of which refractive indices are different from each other.