Image Sensor Color Filter Array for Blue Light Sensitivity
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Solution Overview
Problem
Conventional CMOS and CCD image sensors have poor sensitivity to blue light due to photon absorption close to the surface, leading to reduced sensitivity and noise, especially in low light conditions, as they typically use Bayer patterns with fewer blue pixels, resulting in images with poor blue wavelength sensitivity and noise characteristics.
Innovation Solution
The proposed solution involves rearranging the color filters in a 2-by-2 matrix to allocate a greater area for blue light, a lesser area for green light, and a lesser area for red light, using patterns like CYM or modifying the Bayer pattern to include two blue filters, one red, and one green, or using cyan, yellow, and magenta filters to enhance blue light exposure and sensitivity across the spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional Bayer pattern (RGGB) is used with one blue filter, then device complexity is reduced and manufacturing is simplified, but blue light sensitivity deteriorates and noise characteristics worsen
Solution Approach 1:
The patent applies local quality by making different parts of the filter array have different properties - specifically, increasing the proportion of blue-sensitive pixels (using cyan and magenta filters that transmit blue light) in regions where blue light sensitivity is needed, while maintaining other filter types in different regions. This creates a non-uniform filter distribution that optimizes blue light capture without requiring complete redesign of the entire array structure
Solution Approach 2:
The patent changes the parameter of filter wavelength selection by introducing cyan and magenta filters instead of relying solely on traditional RGB filters. These filters have different spectral transmission characteristics - cyan transmits blue and green while blocking red, and magenta transmits blue and red while blocking green - thereby enhancing blue light sensitivity through parameter modification of the filter properties
2Reliability
If more blue filters are allocated in the filter array, then blue light sensitivity is improved, but device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
Rather than uniformly increasing blue filters across the entire array (which would increase complexity), the patent applies local quality by strategically placing cyan and magenta filters in specific positions within the array. This localized approach enhances blue light sensitivity in critical regions while maintaining a manageable overall device complexity
Solution Approach 2:
The cyan and magenta filters serve multiple functions: they transmit blue light (improving blue sensitivity) while also contributing to green and red channel formation through their spectral characteristics. This multi-functionality allows the system to achieve enhanced blue sensitivity without proportionally increasing the total number of filters or device complexity
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 improves blue light exposure and reduces noise, allowing for more faithful image capture in low light situations by increasing the area dedicated to blue light capture, thereby enhancing the overall sensitivity and reducing noise in image sensors.
Implementation Method 1
filters formed over a portion of an array of photosensitive elements... The pattern can be such that the exposure of a unit matrix (such as a 2-by-2 square of four pixels) to light (such as blue light) is improved
Data Source
AI summary
An image sensor includes filters formed over a portion of an array of photosensitive elements in a predetermined pattern. The pattern can be such that the exposure of a matrix (such as a 2-by-2 square of pixels) to light (such as blue light) is improved, while maintaining acceptable capability to capture light across the entire spectrum. The pattern can be such that two blue filters, one red, and one green filter is used by a 2-by-2 square matrix of pixels. The pattern can also include cyan, yellow, and magenta (CYM) filters.