Multipart Diffractive Lenses for Image Sensors
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Solution Overview
Problem
Conventional image sensors with curved microlenses suffer from optical cross-talk due to peripheral light passing through without being focused, leading to suboptimal image quality.
Innovation Solution
The use of diffractive lenses with varying refractive indices and thicknesses to redirect incident light, focusing or defocusing it effectively onto photodiodes, thereby mitigating optical cross-talk and enhancing image sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional curved microlenses are used to focus light, then light focusing capability is improved, but optical cross-talk increases due to peripheral light passing through without being focused
Solution Approach 1:
The microlens is divided into multiple segments: a central region and a peripheral region. Each region has different optical properties - the central region focuses light while the peripheral region is designed to block or redirect peripheral light, thereby reducing optical cross-talk between adjacent pixels
Solution Approach 2:
Different regions of the microlens are assigned different functional properties. The central region maintains high refractive index for effective light focusing, while the peripheral region uses low refractive index material or air gaps to prevent peripheral light from causing cross-talk, optimizing each region's contribution to overall performance
2Ease of manufacture
If microlenses with uniform refractive index are used, then manufacturing simplicity is maintained, but light focusing efficiency decreases for peripheral light
Solution Approach 1:
The refractive index parameter is varied across different regions of the microlens. The central region uses high refractive index material for efficient light focusing, while the peripheral region transitions to low refractive index material or air, creating a gradient that improves overall light control without significantly complicating the manufacturing process
Solution Approach 2:
The microlens is constructed using composite structures combining different materials with different refractive indices. This includes using silicon nitride for the central region and silicon oxide or air for the peripheral region, creating a composite lens that achieves superior optical performance
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
The implementation of diffractive lenses with multiple refractive indices and customizable thicknesses improves light focusing, reducing optical cross-talk and enhancing image quality by ensuring that light is directed more precisely onto photodiodes, leading to better image capture and processing.
Implementation Method 1
The use of diffractive lenses with varying refractive indices and thicknesses to redirect incident light, focusing or defocusing it effectively onto photodiodes
Data Source
AI summary
An image sensor may include an array of imaging pixels. Each imaging pixel may have a photosensitive area that is covered by a respective multipart diffractive lens to focus light onto the photosensitive area. The multipart diffractive lenses may have multiple portions with different indices of refraction. The portions of the diffractive lenses closer to the center of the diffractive lenses may have higher indices of refraction to focus light. Alternatively, the portions of the diffractive lenses closer to the center of the diffractive lenses may have lower indices of refraction to defocus light. The multipart diffractive lenses may have stacked layers with the same refractive indices but different widths.