Image Sensor Color Filter Layout for Small-Pixel Light Condensation
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Solution Overview
Problem
As the number of pixels increases in image sensors to enhance resolution, the effective pixel area decreases due to reduced light sensitivity caused by smaller pixel sizes, necessitating improved light concentration efficiency on photodiodes.
Innovation Solution
The image sensor incorporates color filters with high refractive indices, specifically a green filter with a refractive index greater than 1.7 for the green light wavelength range, along with a microlens and interference blocking structures, to enhance light condensation efficiency and reduce beam spot size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixels is increased to enhance resolution, then the resolution is improved, but the effective pixel area decreases due to smaller pixel sizes
Solution Approach 1:
The patent changes the refractive index parameter of the green color filter to greater than 1.7, which optimizes light refraction and concentration efficiency. This parameter change allows smaller pixels to effectively concentrate light onto photodiodes, maintaining sensitivity despite reduced pixel area, thereby resolving the contradiction between high resolution and effective pixel area.
2Quantity of substance
If the pixel size is reduced to increase pixel density, then the pixel density is improved, but the light sensitivity decreases
Solution Approach 1:
The patent optimizes the refractive index of the green color filter (>1.7) and controls the thickness of the green filter layer (500-2000 Å) to maximize light concentration efficiency. These parameter changes enable reduced pixel sizes to maintain adequate light sensitivity by improving the efficiency of light guidance to photodiodes.
Solution Approach 2:
The patent employs a composite color filter structure with multiple layers including green, blue, and red color filters, each with optimized refractive indices. This composite structure enhances overall light concentration efficiency across different wavelengths, compensating for the reduced light gathering area of smaller pixels.
3Illumination intensity
If the thickness of the color filter is reduced to improve light transmission, then the light transmission is improved, but the spectral filtering characteristics deteriorate
Solution Approach 1:
The patent precisely controls the thickness parameter of the green color filter layer to be between 500-2000 Å and optimizes the refractive index to >1.7. These parameter changes enable the thin filter to maintain adequate spectral filtering characteristics while improving light transmission and concentration efficiency to the photodiodes.
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 increases the effective pixel area and enhances sensitivity by improving light condensation efficiency and focusing incident light closer to the light sensing element, while maintaining desired spectral characteristics with a small filter thickness.
Implementation Method 1
a refractive index of the green filter is greater than 1.7 for a green light wavelength range of 500 nm to 570 nm
Implementation Method 2
a microlens disposed on the color filter array layer
Data Source
AI summary
Provided is an image sensor including a light sensing element, a planarization layer disposed on the light sensing element, a color filter array layer disposed on the planarization layer, the color filter array layer including color filters, and a microlens disposed on the color filter array layer, wherein the color filters include a green filter, a blue filter and a red filter, and wherein a refractive index of the green filter is greater than 1.7 for a green light wavelength range of 500 nm to 570 nm.