Microlens Resin Stack for Low-Reflection Imaging Elements
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Solution Overview
Problem
Conventional imaging elements experience light reflection issues due to the presence of multiple layers with different refractive indices between the microlens and the color filter, leading to deteriorated image quality.
Innovation Solution
An imaging element configuration featuring a microlens with a refractive index difference from a transparent resin layer, which includes a first and second transparent resin layer with differing refractive indices and an antireflection layer, and a sealing glass, reduces light reflection by optimizing the refractive index difference and using antireflection techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple layers with different refractive indices are arranged between the microlens and color filter, then light collection efficiency is improved, but light reflection at interfaces increases and image quality deteriorates
Solution Approach 1:
The patent introduces a resin layer with refractive index 1.40-1.60 between the microlens and color filter as an intermediary medium. This resin layer acts as a refractive index bridge, gradually transitioning light from the high refractive index microlens to the color filter, thereby reducing interface reflection while maintaining light collection efficiency.
Solution Approach 2:
The patent optimizes the refractive index parameter of the resin layer to be within 1.40-1.60, which is specifically selected to minimize reflection at the microlens-color filter interface. By carefully controlling this physical parameter, the patent achieves reduced light reflection while preserving optical performance.
2Reliability
If silicon nitride is used as microlens material to increase refractive index difference, then light collection rate decreases are reduced, but stress difference between layers increases requiring additional stress relaxation layers
Solution Approach 1:
The patent removes the stress relaxation layer from the multi-layer structure, simplifying the device configuration. By selecting a resin material with appropriate mechanical properties and refractive index (1.40-1.60), the patent achieves both optical performance and stress management without requiring additional stress relaxation layers.
Solution Approach 2:
The patent uses a composite structure combining silicon nitride microlens with an organic resin layer, leveraging the complementary properties of inorganic and organic materials. The resin layer provides both optical functionality (refractive index matching) and mechanical functionality (stress management), eliminating the need for separate stress relaxation layers.
3Reliability
If transparent resin with higher refractive index than air is used, then refractive index difference at microlens surface is secured, but light reflection at resin-microlens interface increases
Solution Approach 1:
The patent applies different material properties to different regions: the microlens uses high refractive index silicon nitride for light collection, while the adjacent resin layer uses moderate refractive index (1.40-1.60) for interface optimization. This local differentiation of material qualities minimizes reflection at the interface while preserving the refractive index advantage where needed.
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 configuration effectively reduces light reflection at the interfaces, enhancing image quality by minimizing flare and improving light collection efficiency without the need for additional stress-relaxing films.
Implementation Method 1
a microlens arranged adjacent to the pixel, and configured to collect incident light, irradiate the pixel with the incident light
Implementation Method 2
a transparent resin layer arranged adjacent to the microlens, and having a refractive index different from a refractive index of the microlens by a predetermined difference
Data Source
AI summary
To reduce reflection of incident light in an imaging element having a transparent resin arranged on a surface of a microlens. The imaging element includes a pixel, a microlens, a transparent resin layer, and a sealing glass. The pixel is formed on a semiconductor substrate and generates an image signal according to radiated light. The microlens is arranged adjacent to the pixel, collects incident light, irradiates the pixel with the incident light, and flattens a surface of the pixel. The transparent resin layer is arranged adjacent to the microlens and has a refractive index different from a refractive index of the microlens by a predetermined difference. The sealing glass is arranged adjacent to the transparent resin and seals the semiconductor substrate.