Image Sensor Electro-Optical Film Light Focusing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CMOS image sensors face challenges in quantum efficiency (QE) due to improper dimensions or misalignment of microlenses, leading to reduced QE and crosstalk between pixels.
Innovation Solution
The use of an electro-optical (EO) film with adjustable refractive index based on an applied electrical field allows for tuning of light propagation direction into the photodiode, improving QE and reducing crosstalk by adjusting focal point locations for different wavelengths of light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If microlenses are used to focus light onto photodiodes, then light focusing capability is improved, but manufacturing precision deteriorates due to improper dimensions or misalignment
Solution Approach 1:
The patent changes the optical parameter (refractive index) of the medium between the microlens and photodiode by introducing an EO film. By applying electrical voltage, the refractive index can be dynamically adjusted to compensate for manufacturing imperfections in microlens dimensions and alignment, thereby maintaining precise light focusing without requiring extremely tight manufacturing tolerances
Solution Approach 2:
The EO film acts as an intermediary optical element between the microlens and photodiode. This intermediate layer with adjustable refractive index compensates for misalignment and dimensional errors, enabling the system to achieve proper light focusing even when the microlens parameters are not perfectly precise
2Device complexity
If traditional fixed refractive index materials are used, then device complexity is reduced, but quantum efficiency deteriorates due to inability to adjust focal point locations
Solution Approach 1:
The patent introduces dynamic controllability to the optical system by using an EO film whose refractive index can be changed in real-time through electrical voltage application. This allows the focal point location to be dynamically adjusted to match the photodiode position, significantly improving quantum efficiency while adding only moderate complexity through the EO film and voltage control circuitry
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 enhances quantum efficiency to greater than 40% and reduces crosstalk, compared to traditional methods without the EO film, by accurately focusing light onto the photodiode.
Implementation Method 1
The use of an electro-optical (EO) film with adjustable refractive index based on an applied electrical field allows for tuning of light propagation direction into the photodiode
Implementation Method 2
A CMOS image sensor utilizes light-sensitive CMOS circuitry to convert photons into electrons. The light-sensitive CMOS circuitry typically comprises a photodiode formed in a substrate. As the photodiode is exposed to light, electrical charges are induced in the photodiode
Data Source
AI summary
An image sensor includes a plurality of pixels. Each of the plurality of pixels includes a photodiode. Each pixel further includes a color filter over the photodiode. Each pixel further includes a first transparent conductive layer over the color filter. Each pixel further includes an electro-optical (EO) film over the first transparent conductive layer. Each pixel further includes a second transparent conductive layer over the EO film. Each pixel further includes a pillar of transparent conductive material electrically connecting the first transparent conductive layer and the second transparent conductive layer.