Complementary Color Filter Array for Image Sensor Crosstalk Reduction
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Solution Overview
Problem
CMOS image sensors face reduced sensitivity and signal-to-noise ratio (SNR) due to decreased pixel size, leading to increased crosstalk and low transmissivity in conventional RGB Bayer patterns.
Innovation Solution
An image sensor utilizing a complementary color filter array with green, yellow, and cyan filters, along with white filters, arranged diagonally to enhance light transmissivity and cancel crosstalk, thereby improving sensitivity and SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the pixel size is decreased to increase the number of pixels, then the compact size and resolution are improved, but the photodiode area decreases leading to reduced sensitivity and increased crosstalk
Solution Approach 1:
The patent uses complementary color filters (cyan, yellow, green) instead of conventional RGB filters. These filters have higher light transmissivity in their respective passbands, allowing more light to reach the photodiode even when the pixel size is reduced. The cyan filter transmits blue and green light, the yellow filter transmits red and green light, and the green filter transmits green light, collectively capturing a broader spectrum with higher efficiency than traditional RGB filters.
Solution Approach 2:
The patent employs a composite filter structure combining multiple complementary color filters (cyan, yellow, green) with white light transmission capabilities. This composite approach allows the system to simultaneously achieve high transmissivity across different wavelength ranges, improving overall light capture efficiency and maintaining sensitivity despite smaller pixel dimensions.
2Area of stationary object
If the distance between adjacent pixels is decreased to increase pixel density, then the resolution is improved, but the crosstalk between adjacent pixels increases leading to decreased SNR
Solution Approach 1:
The complementary color filters are specifically designed to transmit certain wavelength ranges while blocking others. The cyan filter blocks red light, the yellow filter blocks blue light, and the green filter blocks both red and blue light. This selective transmission reduces spectral overlap between adjacent pixels detecting different colors, thereby minimizing crosstalk and improving signal-to-noise ratio even at high pixel densities.
3Ease of operation
If conventional RGB Bayer pattern filters are used, then the color filtering function is achieved, but the transmissivity is low due to light absorption by each color filter
Solution Approach 1:
The patent replaces the conventional RGB Bayer pattern with a complementary color filter arrangement using cyan, yellow, and green filters. These filters are positioned to transmit their respective complementary wavelengths more efficiently. The cyan filter transmits blue and green light, the yellow filter transmits red and green light, and the green filter transmits green light, achieving superior transmissivity compared to traditional red, green, and blue filters that absorb more light.
Solution Approach 2:
The complementary color filter system serves multiple functions simultaneously: it provides color filtering, achieves high transmissivity across the visible spectrum, and enables effective crosstalk reduction. The white light transmission capability further enhances the system's versatility by allowing broadband light detection when color separation is not required.
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 solution effectively increases light transmissivity and improves sensitivity by canceling crosstalk, resulting in a higher average sensitivity and SNR compared to conventional Bayer patterns.
Implementation Method 1
a green filter used to transmit a green component of an incident light
Implementation Method 2
a yellow filter used to transmit a yellow component of the incident light
Implementation Method 3
a cyan filter used to transmit a cyan component of the incident light
Implementation Method 4
a first white filter used to transmit the incident light and a second white filter used to transmit the incident light
Implementation Method 5
a first light detection unit converting light passing through the green filter to a first electric signal, a second light detection unit converting light passing through the yellow filter to a second electric signal, and a third light detection unit converting light passing through the cyan filter to a third electric signal
Data Source
AI summary
An image sensor capable of canceling crosstalk without reduction of a signal to noise ratio (SNR) to improve a sensitivity includes a plurality of light detection units and a filter array including a plurality of filters, with each of the plurality of filters being deposited on a corresponding one of the light detection units. The filter array includes a green filter used to transmit a green component of an incident light, a yellow filter used to transmit a yellow component of the incident light, and a cyan filter used to transmit a cyan component of the incident light.