Shading Roller Arc and Flat Surfaces for Skew Correction
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Solution Overview
Problem
Conventional image reading apparatuses face challenges in obtaining accurate shading data due to skewing of the shading roller, which affects the distance between the image sensor and the shading roller's surface, leading to uneven light reception and inappropriate shading correction.
Innovation Solution
The apparatus includes a shading roller with both an arc-shaped and a flat white reference surface, allowing the processor to calculate and correct pixel values from these surfaces to reduce the influence of skewing, enabling accurate shading data acquisition and correction of document read data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a white reference arc surface is used on the shading roller, then shading data can be obtained, but the distance from the image sensor to the reference surface varies depending on position due to skewing, causing uneven light reception and inaccurate shading correction
Solution Approach 1:
The reference surface is divided into two distinct surfaces: a white reference arc surface and a white reference flat surface. This segmentation allows the system to use the arc surface for obtaining shading data while using the flat surface as a reference for correction, thereby compensating for the distance variations caused by skewing.
Solution Approach 2:
The white reference flat surface acts as an intermediary element that provides a stable reference point for distance measurement. By comparing the distance to the arc surface with the distance to the flat surface, the system can calculate and correct for the skewing effect, thus maintaining shading data accuracy despite attachment precision issues.
2Reliability
If the longitudinal direction of the shading roller is not parallel to the arrangement direction of the image sensor array due to attachment accuracy issues, then the distance from the image sensor to the outer peripheral surface varies, but using both arc and flat reference surfaces allows correction of this variation
Solution Approach 1:
The system implements a feedback mechanism where the distance to the flat reference surface is measured and used to calculate the distance to the arc reference surface. This feedback loop allows the system to dynamically adjust for skewing effects, ensuring reliable shading correction even when attachment accuracy is compromised.
Solution Approach 2:
The system changes the parameter used for distance measurement from a single-point measurement to a two-point measurement (arc surface and flat surface). By measuring distances to both surfaces and calculating the difference, the system can determine the skewing angle and compensate for it, thereby maintaining reliability despite variations in attachment accuracy.
3Measurement precision
If only a white reference arc surface is provided, then shading data can be obtained, but foreign matter interference cannot be effectively handled
Solution Approach 1:
The white reference flat surface serves as an intermediary reference that is less susceptible to foreign matter interference. By using this flat surface as a stable reference point, the system can distinguish between actual shading variations and artifacts caused by foreign matter on the arc surface, thereby maintaining measurement precision even in the presence of contamination.
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 approach allows for effective reduction of skewing's influence on shading data, improving shading correction and image data quality even when the shading roller is skewed, and effectively handles foreign matter interference.
Implementation Method 1
an image sensor array that is provided to oppose the shading roller across a transport path of a document, and includes a plurality of image sensors arranged in a main scanning direction and receiving reflected light of light emitted from a light source toward the document or the shading roller
Data Source
AI summary
An image reading apparatus includes: a shading roller that has a columnar shape extending in a longitudinal direction and is rotatable about a rotation axis extending in the longitudinal direction, the shading roller including, on an outer peripheral surface, a white reference arc surface which is white, has an arc-shaped cross section in a lateral direction, and extends in the longitudinal direction, and a white reference flat surface which is white, is a flat surface, and extends in the longitudinal direction; an image sensor array that is provided to oppose the shading roller across a transport path of a document, and includes a plurality of image sensors arranged in a main scanning direction and receiving reflected light of light emitted from a light source toward the document or the shading roller; and a processor, wherein the processor calculates difference data indicating a difference between arc surface read data, which indicates pixel values output from the image sensors, respectively, and obtained as the image sensor array receives the reflected light from the white reference arc surface, and flat surface read data, which indicates pixel values output from the image sensors, respectively, and obtained as the image sensor array receives the reflected light from the white reference flat surface, based on the arc surface read data and the flat surface read data, acquires corrected arc surface read data based on the arc surface read data and the difference data, corrects document read data, obtained as the image sensor array receives the reflected light from the document, based on the corrected arc surface read data to acquire corrected document read data, and forms image data corresponding to the document based on the corrected document read data.