Color Filter Array Layout for Imaging and Spectral Measurement
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Solution Overview
Problem
Common image sensors perform only rough color reproduction and experience significant metamerism issues due to limited sampling points, making it challenging to calculate white balance coefficients and color conversion matrices.
Innovation Solution
An image sensor with a color filter array that includes both basic and extended color filter elements, where each type of color filter element has a different color combination, increasing sampling points for improved color reproduction precision and reducing metamerism, while allowing both imaging and spectral measurement through a single exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a common color filter array with three or four color filters per element is used, then the device complexity is low and manufacturing is easy, but the color reproduction precision is poor and metamerism problems occur
Solution Approach 1:
The color filter array is segmented into multiple types of color filter elements (first type with 3 basic color filters, second type with 4 basic color filters, third type with extended color filters). This segmentation increases the number of sampling points in the spectral domain without requiring a complete redesign of the entire array, thereby improving color reproduction precision while maintaining manageable device complexity.
Solution Approach 2:
Different regions of the color filter array are assigned different color filter element types with specific local characteristics. The first color filter elements provide standard RGB sampling, the second provide extended color sampling, and the third provide additional spectral information. This local differentiation allows the system to capture more spectral information locally, improving overall color reproduction precision without uniformly increasing complexity across the entire array.
2Measurement precision
If only three or four sampling points are used in the color filter array, then the device complexity is low, but the spectral measurement accuracy is insufficient and white balance calculation becomes challenging
Solution Approach 1:
The sampling points are segmented into multiple categories based on color filter type: first color filter elements provide three sampling points (RGB), second color filter elements provide four sampling points (RGBY or similar), and third color filter elements provide extended spectral sampling points. This segmentation increases the total number of sampling points and improves spectral measurement accuracy while keeping the structural complexity manageable through systematic arrangement.
Solution Approach 2:
The color filter array transitions from traditional spatial sampling (arranging color filters in a grid pattern) to spectral dimension sampling by introducing color filter elements with different spectral transmission characteristics. This adds a spectral dimension to the sampling process, enabling more accurate spectral measurement without proportionally increasing spatial complexity.
3Productivity
If separate imaging and spectral measurement systems are used, then the measurement precision for both functions is high, but the device complexity increases and time consumption increases
Solution Approach 1:
The imaging and spectral measurement functions are merged into a single color filter array system. The first color filter elements (RGB) support both standard imaging and spectral measurement, while the second and third color filter elements provide extended spectral information. This merging allows the system to perform both imaging and spectral measurement simultaneously through one exposure, improving productivity while maintaining measurement precision through the diverse color filter element types.
Solution Approach 2:
The color filter array is designed with multi-functionality, where the same array structure serves both imaging and spectral measurement purposes. The basic color filter elements (RGB) provide universal support for both functions, while the extended color filter elements enhance spectral measurement capability without compromising imaging performance. This universality eliminates the need for separate systems, reducing time consumption and 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
Enhances color reproduction precision, reduces metamerism, and simplifies the calculation of white balance coefficients and color conversion matrices, facilitating miniaturization and low-cost production suitable for mobile devices.
Implementation Method 1
a color filter array covering the pixel array, where the color filter array includes a plurality of color filter elements
Implementation Method 2
an optical signal passing through the extended color filter is for spectral measurement
Implementation Method 3
A first pixel is configured to perform optical-to-electrical conversion on the first optical signal to obtain a first electrical signal
Data Source
AI summary
An image sensor includes a pixel array and a color filter array covering the pixel array, where the color filter array includes a plurality of color filter elements, the plurality of color filter elements include at least one first color filter element and at least one second color filter element, each first color filter element includes a basic color filter and an extended color filter, and each second color filter element includes a plurality of basic color filters. A color of the extended color filter is different from a color of the basic color filter. An optical signal passing through the basic color filter is at least for imaging, and an optical signal passing through the extended color filter is for spectral measurement.