Color Filter Array Pixel Density for Accurate Image Capture
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Solution Overview
Problem
Existing colorimetric image capture systems face challenges in achieving accurate color reproduction due to the complex spectral sensitivities of R, G, and B, which are derived from the overlapping spectral sensitivities of L and M cones, leading to noise amplification and poor color accuracy.
Innovation Solution
An image sensor with a color filter array that assigns higher pixel density to colors with low color separation and lower pixel density to colors with high color separation, combined with a digital image signal processor that demosaicks, applies a chroma denoiser, and converts the image data to a specified color space to enhance color accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If R, G, B spectral sensitivities are obtained by differencing L, M, S spectral sensitivities, then color reproduction is achieved, but noise amplification occurs and color accuracy deteriorates
Solution Approach 1:
The patent segments the color filter array into different color regions (R, G, B) with different pixel densities. By dividing the sensor array and assigning different sampling densities to different color channels, the system avoids the noise amplification problem of uniform differencing while maintaining color reproduction capability.
Solution Approach 2:
The patent applies local quality by assigning different pixel densities to different color regions based on their specific needs. The R and B regions use lower pixel density since they have better inherent signal quality, while the G region uses higher pixel density to compensate for its noisier characteristics after differencing.
2Ease of manufacture
If uniform pixel density is used across all colors in the photosite array, then manufacturing is simplified, but color accuracy deteriorates due to inadequate sampling of colors with low color separation
Solution Approach 1:
The patent implements local quality by varying the pixel density across different color regions of the photosite array. Each color region (R, G, B) is assigned a pixel density appropriate to its specific requirements, with green regions having higher density due to greater noise, thereby improving overall color accuracy.
Solution Approach 2:
The patent changes the parameter of pixel density from a uniform value to a spatially varying value that depends on the color region. This parameter change allows the system to optimize sampling density for each color channel, improving color accuracy while the overall structure remains manufacturable.
3Device complexity
If compromise R, G, B filters are used to avoid negative sensitivity, then device complexity is reduced, but color accuracy deteriorates
Solution Approach 1:
The patent segments the color filter array into distinct R, G, and B regions, each with its own optimized filter characteristics. This segmentation allows each region to use filters tailored to its specific requirements rather than forcing a compromise design across the entire array.
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 system improves color accuracy by reducing noise amplification and enhancing color reproduction, resulting in higher signal-to-noise ratio and better image quality.
Implementation Method 1
an image sensor with an array of light sensitive photosites of a plurality of colors
Data Source
AI summary
A system for capturing color images comprising an image sensor with an array of light sensitive photosites of a plurality of colors. Each color has its own spectral sensitivity. Colors with a substantially low color separation are assigned a substantially high density of pixels in the photosite array and colors with a substantially high color separation are assigned a substantially low density of pixels in the photosite array. A digital image signal processor is adapted to receive a raw mosaicked image from said image sensor when the image sensor is impacted with light, and to reconstruct a full color image from the raw image data. Optionally, the raw image data is demosaicked, a chroma denoiser is applied to the image data and the image data is converted to a specified color space, wherein application of the chroma denoiser and conversion to a specified color space are performed in any order.