Image Sensor Microlens Refractive Index Optimization
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Solution Overview
Problem
Current image sensors face challenges in optimizing optical properties, particularly in achieving improved autofocus performance and increased sensitivity, due to variations in microlens refractive indices and heights, which affect light condensation and signal processing across different pixel domains.
Innovation Solution
The image sensor design incorporates a substrate with adjacent first and second pixel domains, featuring first and second microlenses with distinct refractive indices and geometries, where the second microlens has a greater refractive index and a specific curved top surface and flat part configuration, ensuring minimal height difference with the first microlens, to enhance light condensation and reduce crosstalk between pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If microlenses with different refractive indices are used in different pixel domains, then optical properties and autofocus performance are improved, but sensitivity differences between pixels increase
Solution Approach 1:
The patent applies local quality by using microlenses with different refractive indices in different pixel domains. Specifically, the first pixel domain uses microlenses with a first refractive index while the second pixel domain uses microlenses with a second refractive index, allowing optimization of optical properties for different functional requirements (e.g., autofocus vs. regular imaging) while maintaining overall system performance
Solution Approach 2:
The patent changes the refractive index parameter of the microlenses based on pixel domain functionality. By selecting microlenses with different refractive indices for different pixel domains, the patent optimizes optical properties such as light condensation and focal length for specific applications like autofocus, while the level difference control maintains sensitivity uniformity
2Use of energy by moving object
If microlens height variations are increased, then light condensation capability is improved, but crosstalk between adjacent pixels increases
Solution Approach 1:
The patent applies local quality by allowing different microlens heights in different pixel domains. The first pixel domain can have microlenses with heights optimized for light condensation, while the second pixel domain has microlenses with heights optimized to prevent crosstalk, enabling each domain to perform its specific function optimally
Solution Approach 2:
The patent segments the pixel array into different domains with different microlens specifications. By dividing the sensor into first and second pixel domains with distinct microlens characteristics, the patent allows independent optimization of light condensation and crosstalk prevention in different regions
3Reliability
If complex microlens geometries are implemented, then optical properties are improved, but manufacturing complexity and costs increase
Solution Approach 1:
The patent applies local quality by implementing different microlens geometries in different pixel domains. The first pixel domain can use microlenses with curved top surfaces for optimized light condensation, while the second pixel domain uses microlenses with flat top surfaces for simplified manufacturing, allowing each domain to have the appropriate complexity for its function
Solution Approach 2:
The patent segments the microlens array into different types based on pixel domain functionality. By creating distinct microlens configurations for different domains, the patent reduces overall manufacturing complexity while maintaining high optical performance 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 design improves optical properties by reducing sensitivity differences between pixels, enhancing autofocus performance, and increasing the image sensor's sensitivity, while minimizing crosstalk and manufacturing costs.
Implementation Method 1
a second refractive index of the second microlens is greater than a first refractive index of the first microlens
Implementation Method 2
enhance light condensation and reduce crosstalk between pixels
Implementation Method 3
The photodiode serves to convert incident light into electrical signals
Data Source
AI summary
Provided is an image sensor including: a substrate including a first pixel domain and a second pixel domain that are adjacent to each other in a first direction, the first pixel domain including first pixels and the second pixel domain including second pixels; a first color filter provided on a first surface of the substrate and vertically overlapping the first pixels; a first microlens provided on the first color filter and each of the first pixels; and a second microlens provided on the first surface of the substrate and vertically overlapping at least a portion of each of the second pixels, wherein a second refractive index of the second microlens is greater than a first refractive index of the first microlens, and wherein a level difference between an uppermost part of the first microlens and an uppermost part of the second microlens is within about 2% of a maximum height of the first microlens.