Pixel-by-Pixel Black Correction for Image Scanning
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Solution Overview
Problem
Conventional image scanning devices face inefficiencies in black level correction due to varying dark current changes from pixel to pixel, especially with temperature distribution and manufacturing variations, leading to inadequate correction and reduced productivity from frequent light source stabilization requirements.
Innovation Solution
An image scanning device that performs pixel-by-pixel black correction by calculating a ratio of dark-current black levels from pre-scanning and ongoing-scanning data to correct black levels, allowing for accurate subtraction from digital image data, even with non-uniform temperature distributions among pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pixel-by-pixel black-level correction data is updated evenly based on black level of OPB pixels, then correction process is simple, but black correction cannot be performed appropriately when amounts of change in dark current vary from pixel to pixel
Solution Approach 1:
The patent applies local quality by transitioning from uniform correction to pixel-specific correction. Each pixel's black-level correction data is individually updated based on its own dark current characteristics rather than applying a single uniform correction value to all pixels. This allows each pixel to receive customized correction tailored to its specific dark current behavior, improving correction accuracy while maintaining manageable complexity through systematic implementation.
2Measurement precision
If light source is switched off to obtain black levels, then black correction can be performed, but time to wait for light amount stabilization is required reducing productivity
Solution Approach 1:
The patent implements preliminary action by obtaining and storing black-level correction data in advance before actual scanning operations. The system performs initial black level measurements and creates correction data that can be reused for multiple subsequent scanning operations. This eliminates the need to repeatedly switch off the light source and wait for stabilization, as the correction data is prepared beforehand and applied during normal scanning, thereby maintaining measurement accuracy while significantly improving productivity.
3Ease of manufacture
If uniform black-level correction is applied to all pixels, then correction implementation is straightforward, but correction is inadequate when temperature distribution and manufacturing variations cause pixel-to-pixel dark current differences
Solution Approach 1:
The patent applies parameter changes by adjusting the correction approach from uniform to variable based on individual pixel characteristics. The system modifies the black-level correction parameter for each pixel according to its specific dark current behavior, which is influenced by temperature distribution and manufacturing variations. This allows the correction effectiveness to adapt to actual pixel-to-pixel differences while maintaining reasonable implementation complexity through systematic parameter management.
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 method enables effective black correction, reducing readout errors and maintaining productivity by accounting for individual pixel changes in dark current, even with temperature variations, thus improving image scanning accuracy and efficiency.
Implementation Method 1
a photoelectric conversion unit configured to convert light reflected from the original to an electric signal
Data Source
AI summary
According to an embodiment, an image scanning device includes: a light source unit that emits light onto an original to be scanned; a photoelectric conversion unit that converts light from the original to an electric signal; a converting unit that converts the electric signal from the photoelectric conversion unit into digital image data; and a black correcting unit that performs black correction by correcting pixel-by-pixel black levels of pixels contained in pre-scanning digital image data obtained before the original is scanned based on a ratio of a dark-current black level of a pixel contained in ongoing-scanning digital image data obtained during scanning of the original to a dark-current black level of the pixel contained in the pre-scanning digital image data, and subtracting the corrected pixel-by-pixel black levels from the ongoing-scanning digital image data.