MTF Correction for Image Reading Apparatus Density Differences
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Solution Overview
Problem
Conventional image reading apparatuses face challenges in accurately matching Modulation Transfer Function (MTF) characteristics between the front and back surfaces of a double-sided original, leading to density and color differences, especially when using different optical systems or reading modes.
Innovation Solution
An image reading apparatus with separate reading units for each surface, equipped with an MTF correction unit that adjusts image data to approximate MTF characteristics between the front and back surfaces, using techniques such as smoothing filters or edge enhancement filters, and calculating filter coefficients to reduce differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MTF filtering is uniformly performed in the same plane of the original, then the processing is simple and fast, but it is impossible to obtain desired results when there is large variation in MTF characteristics between different areas of the original
Solution Approach 1:
The patent divides the original plane into multiple areas (e.g., first area and second area) and performs MTF filtering with different filter coefficients for each area. This allows the system to adapt to local variations in MTF characteristics across different regions of the original, improving matching precision without sacrificing overall processing efficiency.
2Manufacturing precision
If different MTF filters are used for front and back surfaces to account for MTF variations, then MTF matching precision improves, but device complexity increases
Solution Approach 1:
The patent changes the parameters (filter coefficients) of the MTF filter based on the reading surface (front or back) and area, rather than using completely different filter structures. This allows precise adaptation to different MTF characteristics while maintaining a unified filter framework, thus improving precision without excessive complexity.
3Manufacturing precision
If MTF filtering is performed to reduce differences between front and back surfaces, then image quality improves, but processing time increases
Solution Approach 1:
The patent performs MTF characteristic measurements and determines optimal filter coefficients in advance for different surfaces and areas. These pre-determined coefficients are then applied during actual image processing, reducing the computational burden in real-time processing while maintaining high image quality.
4Device complexity
If the optical systems for front and back surfaces are made identical, then device complexity is reduced, but MTF characteristic differences between surfaces persist due to component assembly variations and spectral characteristics
Solution Approach 1:
The patent incorporates MTF characteristic measurement and feedback mechanisms that evaluate the actual MTF performance of each optical system. Based on this feedback, the system automatically adjusts filter coefficients to compensate for differences caused by component assembly variations and spectral characteristics, achieving consistency without requiring identical hardware.
Data Source
AI summary
An image reading apparatus which approximates the MTF characteristics on the front and back surfaces of the original to each other, in reading a double-sided original, to thereby prevent a density difference and a color difference from being caused between the front and back surfaces of the original. A CCD line sensor and a CIS read front and back surfaces of the double-sided original to output image data. The filter coefficients of first and second MTF correction filters are set for use in a plurality of areas arranged by dividing respective reading ranges of the CCD line sensor and the CIS. The first and second MTF correction filters correct the MTF characteristics of the image data output from the CCD line sensor and the CIS, using the set filter coefficients for associated areas.