CMOS Image Sensor EO Film for Microlens Misalignment Compensation
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Solution Overview
Problem
CMOS image sensors face issues with reduced quantum efficiency (QE) due to improper dimensions or misalignment of microlenses, leading to crosstalk and decreased image accuracy, as they fail to effectively focus incident light onto the photodiodes.
Innovation Solution
Incorporation of an electro-optical (EO) film with adjustable refractive index, which adjusts the light propagation path to compensate for manufacturing errors and misalignment, combined with a layered structure of color filters and transparent conductive materials to optimize light focusing for different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If microlenses are used to focus incident light onto photodiodes, then light focusing capability is improved, but manufacturing precision deteriorates due to improper dimensions or misalignment
Solution Approach 1:
The patent introduces an electro-optical film with adjustable refractive index that can dynamically change its optical properties in response to applied electrical fields. This allows the light focusing characteristics to be adjusted after manufacturing, compensating for microlens misalignment or dimensional errors without requiring perfect manufacturing precision.
Solution Approach 2:
The patent changes the refractive index parameter of the electro-optical film through applied electrical fields to adjust light propagation paths. By varying this physical parameter, the system compensates for manufacturing errors in microlens dimensions and alignment, maintaining effective light focusing capability.
2Reliability
If electro-optical film with adjustable refractive index is incorporated, then quantum efficiency is improved, but device complexity increases
Solution Approach 1:
The electro-optical film serves multiple functions: it acts as both a light propagation medium and an active compensation element for manufacturing errors. Additionally, the transparent conductive layers serve dual purposes of electrical connection and optical transparency, reducing the need for separate components and mitigating the complexity increase.
3Measurement precision
If EO film adjusts light propagation path to compensate for manufacturing errors, then image accuracy is improved, but device complexity increases
Solution Approach 1:
The electro-optical film acts as an intermediary element between the microlens array and the photodiodes. It mediates the light propagation path and provides compensation for manufacturing errors without requiring direct adjustment of the microlenses or photodiodes, thereby improving image accuracy while maintaining relatively simple device architecture.
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 EO film enhances QE to greater than 40% and reduces crosstalk by allowing precise adjustment of focal points for each pixel, improving image accuracy and precision.
Implementation Method 1
an electro-optical (EO) film between the color filter and the microlens, wherein a material of the EO film is configured to change refractive index in response to application of an electrical field
Implementation Method 2
A CMOS image sensor utilizes light-sensitive CMOS circuitry to convert photons into electrons
Data Source
AI summary
An image sensor includes a first photodiode and a second photodiode. The image sensor further includes a first color filter over the first photodiode; and a second color filter over the second photodiode. The image sensor further includes a first microlens over the first color filter and a second microlens over the second color filter. The image sensor further includes a first electro-optical (EO) film between the first color filter and the first microlens, wherein a material of the first EO film is configured to change refractive index in response to application of an electrical field. The image sensor further includes a second EO film between the second color filter and the second microlens, wherein a material of the second EO film is configured to change refractive index in response to application of an electrical field.