Image Reading Device Shading Correction for Density Consistency
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Solution Overview
Problem
Conventional image reading devices experience density differences in image data when using the fixed-document and sheet-through methods due to varying document-to-glass distances, leading to inconsistent image densities.
Innovation Solution
An image reading device with a contact glass, document conveying device, and reading module that performs shading correction using distinct adjustment values for each method, acquired through reference image processing, to maintain consistent image density across different reading positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the fixed-document method is used with a document presser to make close contact with the contact glass, then the document-to-glass distance is reduced, but the image density becomes lighter compared to the sheet-through method
Solution Approach 1:
The patent applies parameter changes by introducing distinct shading correction adjustment values for different reading methods. Specifically, a first adjustment value is used for the fixed-document method and a second adjustment value is used for the sheet-through method. This allows the system to compensate for the inherent differences in document-to-glass distance and lighting conditions between the two methods, thereby maintaining consistent image density across both methods.
2Productivity
If the sheet-through method is used to convey documents without close contact with the contact glass, then the reading speed is improved, but the image density becomes darker compared to the fixed-document method
Solution Approach 1:
The patent uses parameter changes to address the image density difference in the sheet-through method. By applying a second shading correction adjustment value specifically optimized for the sheet-through method, the system compensates for the darker image density caused by the larger document-to-glass distance, thereby maintaining consistent image quality while preserving the high reading speed advantage.
3Device complexity
If a single shading correction adjustment value is used for both reading methods, then the device complexity is reduced, but the image density consistency between methods deteriorates
Solution Approach 1:
The patent applies segmentation by dividing the shading correction adjustment values into separate first and second values corresponding to the fixed-document and sheet-through methods respectively. This segmentation allows each adjustment value to be optimized for its specific reading method, ensuring image density consistency while maintaining relatively simple system architecture through the use of distinct but method-specific correction parameters.
Data Source
AI summary
An image reading device can perform fixed-reading processing where image data is read by a fixed-document method and conveyed-reading processing where image data is read by a sheet-through method while a reading module is kept staying at any of a plurality of image reading positions including a reference reading position. A control portion, when a reference second adjustment value for the reference reading position used for shading correction in the conveyed-reading processing is acquired, calculates a second adjustment values for a plurality of image reading positions based on the reference second adjustment value, and when the reference second adjustment value is not acquired and a first adjustment value used for shading correction in the fixed-reading processing is acquired, calculates the second adjustment values for the plurality of image reading positions based on the first adjustment value.