Shading Reference Data Correction for Image Reading Devices
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Solution Overview
Problem
Image reading devices with SELFOC lens arrays suffer from time-dependent deterioration, leading to distorted sine waves and reduced image quality due to foreign bodies on the shading reference plate, causing streaks in document images during shading correction.
Innovation Solution
An image reading device with a processor that detects the start and end positions of distorted waveform ranges in shading reference data and replaces the affected data with a substitute part, ensuring continuity and minimizing shade value differences to prevent streaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rotating mechanism and cleaning mechanism are added to rotate and clean the reference member, then foreign bodies on the reference member can be removed, but device complexity increases and space requirements conflict with miniaturization trends
Solution Approach 1:
The patent replaces the mechanical rotating and cleaning mechanisms with an image processing approach. The controller detects foreign bodies in the shading reference data and performs digital correction by replacing affected data portions with interpolated values, eliminating the need for physical cleaning mechanisms and reducing device complexity while maintaining reference member effectiveness
Solution Approach 2:
The patent creates a digital copy or model of the shading reference data and processes this copy to remove foreign body effects. By working with digital data representations rather than physically manipulating the reference member, the system achieves cleaning functionality through software algorithms, reducing mechanical complexity
2Reliability
If a part of data in distorted waveform range is removed and replaced with substitute data, then foreign body effects are eliminated, but discontinuity at boundaries between original and substitute data causes streaks in document images
Solution Approach 1:
The patent performs preliminary detection of foreign bodies in the shading reference data before final shading correction is applied. By identifying and marking contaminated data portions in advance, the system can prepare appropriate substitute values through interpolation, ensuring smooth transitions and preventing boundary discontinuities that would cause streaks
Solution Approach 2:
The patent changes the parameters of the substitute data to match the surrounding original data. By interpolating values that conform to the local waveform characteristics and gradually transitioning from substitute to original data, the system maintains parameter continuity at boundaries, eliminating the stark differences that cause streak artifacts
3Productivity
If shading correction is performed using shading reference data containing foreign bodies, then processing speed is maintained, but streaks appear in document images due to dark pixels from foreign bodies
Solution Approach 1:
The patent extracts and removes the harmful portions of the shading reference data that contain foreign body effects. By identifying and excluding only the contaminated data segments while retaining the rest of the high-speed processing capability, the system eliminates streak-causing dark pixels without sacrificing overall processing efficiency
Data Source
AI summary
An image reading device includes: a scanner having characteristics of causing a distorted sine wave being formed by its obtained image data and being represented as an array of shade values arranged in a main scanning direction; a reference member to be scanned; a hardware processor that: obtains a shade value at each main scanning coordinate from shading reference data obtained from the reference member; detects the start and end position of a distorted waveform range in the shading reference data; defines the start and end position of a target range as the main scanning coordinates of two peaks, the two peaks being in a distorted sine wave formed by the shading reference data, the two peaks being within a predetermined reference distance to the right and left of the start and end position; and replaces a part of data in the target range with a substitute part of data.