Image Reading Shading Correction Noise Removal
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Solution Overview
Problem
Existing image reading apparatuses face challenges in generating accurate shading correction data due to noise from light receiving element sensitivity variations, stains, and light source directivity, which are exacerbated by the need to convert shading correction data from reference plates read at different positions, leading to errors in light intensity distribution correction coefficients.
Innovation Solution
An image reading apparatus and method that acquire primary and secondary reference data from reference members at different optical distances, generate correction data, and use these to produce shading correction data, allowing for noise removal while preserving the unevenness caused by directivity, thereby enabling accurate shading correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shading correction data is acquired using a reference plate read at a position different from the original reading position, then the shading correction can be performed, but the light intensity distribution correction coefficients contain noise and errors due to position differences and directivity effects
Solution Approach 1:
The patent segments the correction process into two distinct parts: (1) acquiring light intensity distribution correction coefficients by reading a reference sheet at the original reading position, and (2) acquiring shading correction data by reading a reference plate at a different position. This segmentation allows each correction type to be optimized independently, preventing noise from mixing with essential correction information.
Solution Approach 2:
The patent introduces light intensity distribution correction coefficients as an intermediary element that mediates between the reference sheet read at the original position and the reference plate read at a different position. By using this intermediary, the system can convert shading correction data from one position to another while preserving accuracy.
2Reliability
If strong filtering is performed to remove noise from correction coefficients, then noise from stains and sensitivity variations can be removed, but the peak indicative of uneven directivity required for accurate shading correction is lost
Solution Approach 1:
The patent separates noise removal from directivity preservation by acquiring light intensity distribution correction coefficients and shading correction data through different reading processes. This segmentation allows selective filtering of noise from correction coefficients without affecting the directivity information contained in the shading correction data.
Solution Approach 2:
The patent converts the position difference between reference plate and original reading position from a harmful factor into a beneficial one. By reading the reference plate at a different position and using position conversion with light intensity distribution correction coefficients, the system can perform shading correction more effectively while removing noise.
3Device complexity
If reference sheet and reference plate are read at the same position, then position conversion is not needed, but noise from stains and sensitivity variations cannot be effectively removed
Solution Approach 1:
The patent segments the correction objects into two separate components: light intensity distribution correction coefficients (acquired from reference sheet at original position) and shading correction data (acquired from reference plate at different position). This segmentation enables independent optimization of each correction type.
Solution Approach 2:
The patent uses light intensity distribution correction coefficients as an intermediary to bridge the position difference between reference sheet and reference plate readings, enabling effective noise removal while maintaining correction accuracy.
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 removes noise from stains and light source directivity effects, allowing for precise shading correction data generation, ensuring accurate image reading without losing essential correction information.
Implementation Method 1
a light source for illuminating an original and an image sensor adapted to read images of the original
Implementation Method 2
the variation in sensitivity of light receiving elements of the line image sensor
Data Source
AI summary
An image reading apparatus capable of generating accurate shading correction data while removing noise. A shading reference plate is arranged at a location having different optical distance between the location and an image sensor in an image reading unit from optical distance between original reading position and said image sensor. The shading reference plate is read by the image reading unit whereby secondary reference data is acquired, and a reference sheet is read which is put on a position substantially identical to the original reading position whereby primary reference data is acquired. Primary and secondary correction data is generated based on the primary and secondary reference data, and correction coefficient data is generated based on the primary and secondary correction data. Shading correction data is generated based on read data of the shading reference plate and the correction coefficient data. The shading correction of the images of original read by the image reading unit is performed based on the shading correction data.