Image Reading Device Shading Correction Using Black Reference Data
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Solution Overview
Problem
The existing methods for image reading devices, such as those described in JP-A-2001-028666, face insufficient precision in calculating black reference data, which affects the quality of shading correction in output images.
Innovation Solution
An image reading device and method that acquire black reference data before and after scanning, using linear interpolation to calculate intermediate values, and apply these values for shading correction to improve precision and minimize the impact of signal level changes on output images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If black reference data is acquired only before or only after scanning, then the acquisition process is simple, but the calculation precision of black reference data is insufficient
Solution Approach 1:
The patent applies preliminary action by acquiring black reference data before the scanning operation begins. This pre-acquired data serves as a baseline for subsequent shading correction, allowing the system to compensate for drift effects that occur during scanning. The before-scanning reference data is stored and used in combination with post-scanning data to calculate corrected black reference values.
Solution Approach 2:
The patent implements feedback by acquiring black reference data both before and after scanning, then using the post-scanning data to correct the pre-scanning reference data. The system calculates the difference or drift between the two measurements and applies this correction to improve the accuracy of the black reference data used for shading correction throughout the scanning process.
2Measurement precision
If reference data acquisition takes time, then measurement precision can be maintained, but scanning time increases and productivity decreases
Solution Approach 1:
By acquiring black reference data before scanning in advance, the system prepares correction data that can be applied during or after the scanning process without interrupting the main scanning operation. This preliminary acquisition allows the scanning to proceed continuously while the reference data is ready for correction applications.
Solution Approach 2:
The patent maintains continuity by performing the scanning operation without interruption and acquiring reference data at the beginning and end of the scanning process. The scanning action continues uninterrupted while reference measurements are taken at the boundaries, ensuring that the useful scanning action is not broken while still obtaining the necessary correction data.
3Reliability
If black reference data is not updated during scanning, then the process is efficient, but signal level changes due to drift affect image quality
Solution Approach 1:
The system performs preliminary acquisition of black reference data before scanning begins, establishing a baseline for correction. This pre-prepared reference data is then used throughout the scanning process to maintain image quality without requiring continuous updates during the scan itself.
Solution Approach 2:
The patent applies beforehand cushioning by acquiring black reference data both before and after scanning, creating a buffer against drift effects. The post-scanning reference data acts as a cushion that compensates for any signal level changes that occurred during scanning, ensuring image quality is maintained despite temporal variations.
Data Source
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AI summary
A controller 70 of an image reading device 1 acquires first black reference data at a first time point with a light source 31 off, and stores the first black reference data in a reference data storage 41, and at a second time point after the first time point, acquires with the light source 31 off and stores second black reference data in the reference data storage 41. The controller 70 stores in a scanning data storage 42, without applying shading correction, scanning data read from a document between the first time point and second time point with the light source 31 on. A shading corrector 51 applies shading correction using the first black reference data and second black reference data to the scanning data stored in the scanning data storage 42.