CMOS Image Sensor Color Correction via Bilinear Interpolation

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Solution Overview

Problem

CMOS image sensors face defective color tones due to variance in output voltages from shared components, leading to noise generation when the difference between Gr and Gb color components is not zero, especially as pixel size decreases.

Innovation Solution

The implementation of bilinear interpolation for color correction in CMOS image sensors, where color correction parameters are calculated and applied to adjust color components, ensuring Gr and Gb are equal, thereby compensating for defective color tones.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If multiple pixels share transistors and photodiodes to reduce pixel size, then the resolution and integration density are improved, but the output voltage variance increases causing defective color tones

Engineering Contradiction:

Improvepixel sizeVSAvoidcolor tone uniformity

Core Design Contradiction:

Area of moving objectVSManufacturing precision

Solution Approach 1:

The patent applies local quality by dividing the pixel array into multiple regions (first region with Gr pixels and second region with Gb pixels) and calculating separate color correction parameters for each region. This allows tailored correction for local variations in color tone caused by shared component arrangements, thereby maintaining uniformity despite the reduced pixel size and component sharing.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements feedback by measuring the actual color components (Gr and Gb) in the pixel array, calculating the difference between them, and using this information to generate color correction parameters. These parameters are then applied to correct the color tone, creating a closed-loop system that compensates for the voltage variance introduced by shared components.

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If color correction parameters are calculated for all pixels, then the color accuracy is improved, but the processing time and computational complexity increase

Engineering Contradiction:

Improvecolor accuracyVSAvoidprocessing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent segments the pixel array into distinct regions (first region for Gr pixels, second region for Gb pixels) and calculates color correction parameters separately for each region. This segmentation reduces the computational complexity by focusing calculations on specific pixel groups rather than processing all pixels uniformly, while still achieving high color accuracy through region-specific correction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by calculating color correction parameters only for pixels where the difference between Gr and Gb exceeds a predetermined threshold. This selective approach avoids unnecessary computational operations for pixels that are already within acceptable color tolerance, thereby reducing processing time while maintaining color accuracy where needed.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS7990437B2Color correction in CMOS image sensor

Publication Date: 2011.08.02 SAMSUNG ELECTRONICS CO LTD

AI summary

For color correction in an image sensor, an image sensor processing block generates a plurality of color correction parameters corresponding to a plurality of selected pixels of the image sensor for defining a plurality of areas of a sample image. In addition, a color correction value calculation block generates a respective color correction value corresponding to a given pixel from bilinear interpolation of a respective subset of the color correction parameters corresponding to a respective one of the areas including a respective location of the given pixel.