Octagon Pixel Array Layout With NIR Cut Filtering for Low-Light Color
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Solution Overview
Problem
CMOS image sensors face poor image quality in low light conditions due to inadequate capture of red, green, and blue color luminance, leading to image noise, poor contrast, and color saturation issues.
Innovation Solution
The implementation of a pixel array with octagon-shaped and square-shaped pixel sensors, including visible light, yellow, and near-infrared (NIR) sensors, along with an NIR cut filter layer and high absorption regions, to enhance light sensitivity and color accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional RGB pixel sensors are used, then color detection is achieved, but light sensitivity is insufficient in low light conditions
Solution Approach 1:
The pixel array is segmented into multiple specialized sensor types (RGB photodiodes, yellow photodiodes, and NIR photodiodes) rather than using uniform sensors. Each segment captures specific wavelength ranges, with RGB for color, yellow for luminance, and NIR for low-light enhancement, resolving the contradiction between color accuracy and light sensitivity
Solution Approach 2:
Different regions of the pixel array have different sensor characteristics optimized for specific functions. RGB photodiodes provide color information, yellow photodiodes enhance luminance perception, and NIR photodiodes capture near-infrared light for low-light conditions. This local specialization allows the system to maintain color accuracy while improving overall light sensitivity
2Reliability
If multiple pixel sensor types are integrated, then image quality improves, but device complexity increases
Solution Approach 1:
Multiple specialized sensor types (RGB, yellow, and NIR photodiodes) are merged into a single integrated pixel array structure. This combining approach maintains the benefits of each sensor type while managing complexity through unified fabrication processes and shared readout circuitry, improving image quality without proportionally increasing device complexity
Solution Approach 2:
The pixel array is designed with multi-functionality, where the same structural framework supports multiple sensor types. The pixel sensors can operate in different modes (color detection, luminance detection, low-light enhancement) depending on lighting conditions, reducing the need for separate dedicated systems and managing complexity through versatile design
3Illumination intensity
If NIR photodiodes are added to enhance low light performance, then light sensitivity improves, but NIR light absorption causes color accuracy issues
Solution Approach 1:
The harmful effect of NIR light absorption is extracted and isolated by dedicating specific NIR photodiodes solely for low-light luminance detection. These NIR-specific pixels are separated from the color-sensitive RGB photodiodes, allowing NIR light to be captured for brightness enhancement without interfering with color accuracy in RGB channels
Solution Approach 2:
Yellow photodiodes serve as an intermediary between RGB color sensors and NIR low-light sensors. They capture yellow wavelength light that bridges the gap between visible color and NIR ranges, providing luminance information that enhances low-light performance while maintaining color accuracy through coordinated processing with RGB and NIR channels
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 improves color saturation, contrast, and light sensitivity, resulting in more accurate and detailed images in low light conditions by optimizing the arrangement and types of pixel sensors and using an NIR cut filter layer to reduce NIR light absorption.
Implementation Method 1
Complementary metal oxide semiconductor (CMOS) image sensors utilize light-sensitive CMOS circuitry, referred to as pixel sensors, to convert light energy into electrical energy. A pixel sensor typically includes a photodiode formed in a silicon substrate. As the photodiode is exposed to light, an electrical charge is induced in the photodiode.
Implementation Method 2
The pixel array 200 may include an NIR cut filter layer 302 for visible light pixel sensors of the pixel array. The NIR cut filter layer 302 may be included to block incident NIR light from reaching the visible light pixel sensors.
Data Source
AI summary
In some implementations, a pixel array may include a near infrared (NIR) cut filter layer for visible light pixel sensors of the pixel array. The NIR cut filter layer is included in the pixel array to absorb or reflect NIR light for the visible light pixel sensors to reduce the amount of NIR light absorbed by the visible light pixel sensors. This increases the accuracy of the color information provided by the visible light pixel sensors, which can be used to produce more accurate images. In some implementations, the visible light pixel sensors and/or NIR pixel sensors may include high absorption regions to adjust the orientation of the angle of refraction for the visible light pixel sensors and/or the NIR pixel sensors, which may increase the quantum efficiency of the visible light pixel sensors and/or the NIR pixel sensors.