Image Sensor Offset Correction for Bayer Pattern Noise
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Solution Overview
Problem
Image sensors face challenges in reducing crosstalk noise and achieving high image reproduction quality due to the Bayer pattern arrangement, where green pixels transfer different amounts of light based on adjacent pixel colors, leading to step-like noise and limitations in increasing fill factor due to the presence of material layers and logic circuits.
Innovation Solution
An image sensor with a storage unit, homogeneous pixel determination unit, and offset correction processing unit that identifies dead pixels and calculates a difference value to correct center pixel values, effectively addressing the Gb-Gr offset issue by excluding dead pixels from the calculation and using only normal pixel values for offset correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Bayer pattern arrangement is used for pixel array configuration, then color image capture capability is improved, but Gb-Gr offset noise and step-like noise occur due to different light transfer amounts
Solution Approach 1:
The patent applies preliminary action by performing dead pixel determination and offset correction processing before final image output. The system pre-calculates the Gb-Gr offset values using homogeneous pixel comparison, and pre-corrects the pixel data to eliminate step-like noise before the image is displayed or further processed.
Solution Approach 2:
The patent changes the parameter of pixel offset correction by dynamically calculating Gb-Gr offset values based on homogeneous pixel comparisons. Instead of using fixed offset values, the system adjusts the offset parameters according to the actual pixel characteristics and dead pixel locations, thereby reducing noise while maintaining color accuracy.
2Adaptability or versatility
If material layers and logic circuits are present on the photodiode region, then image sensor functionality is improved, but light incident amount on photodiode is reduced due to blockage
Solution Approach 1:
The patent replaces physical/optical solutions with electronic processing. Instead of trying to increase physical light transmission through the material layers, the system uses electronic offset correction to compensate for the reduced light incident amount. The electronic processing compensates for the optical losses caused by the necessary material layers and circuit structures.
3Measurement precision
If fill factor is increased to improve photosensitivity, then light sensing capability is improved, but the area is limited by the presence of logic circuit parts
Solution Approach 1:
The patent uses copying by comparing each pixel with homogeneous pixels (pixels of the same color type in surrounding areas). By creating a reference model from homogeneous pixels and comparing the center pixel against this copy, the system can identify dead pixels and correct offset errors without needing additional physical sensing area.
4Ease of operation
If dead pixels are included in offset correction calculation, then processing simplicity is maintained, but correction accuracy is reduced due to erroneous offset values
Solution Approach 1:
The patent extracts and removes dead pixels from the offset correction calculation process. The homogeneous pixel determination unit identifies dead pixels by comparing pixel values, and the extraction process separates these defective pixels from the homogeneous pixel group used for offset calculation. This ensures that only normal, functioning pixels contribute to the offset correction, maintaining both accuracy and processing efficiency.
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 solution effectively eliminates the Gb-Gr offset, improving image reproduction quality by accurately processing Bayer pattern data and reducing noise, even in the presence of dead pixels, thereby enhancing the image sensor's ability to handle varying light transmission across pixel arrays.
Implementation Method 1
an image sensor includes a pixel array, which receives external incident light and converts photoelectric charges into electric signals
Data Source
AI summary
An image sensor includes a storage unit configured to store at least a portion of image data, a homogeneous pixel determination unit configured to determine whether dead pixels exist in homogeneous pixels having the same color characteristic as a center pixel in a window of the image data, and an offset correction processing unit configured to calculate a difference value between the center pixel and homogeneous pixels determined as normal pixels by the homogeneous pixel determination unit, and correct a center pixel value by using the calculated difference value.