Document Reading Device Black Reference Correction for Scratch Compensation
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Solution Overview
Problem
In document reading devices using a transparent reading sheet, small scratches formed during document passage lead to inconsistent image concentration, especially for high concentration documents, as irradiated light is reflected off the scratches, causing high concentration areas to be read as lighter images, and existing correction methods fail to maintain consistent image concentration over time.
Innovation Solution
A document reading device with a transparent reading sheet and a black reference member, where the image reading section uses corrected black data to perform shading correction on the document image, ensuring consistent image concentration by using a black reference member to account for scratches on the transparent reading sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a transparent reading sheet is used for both fixed document reading and conveyed document reading, then device downsizing and cost reduction are achieved, but image concentration becomes inconsistent between the two reading methods
Solution Approach 1:
The patent applies local quality by placing a black reference member specifically at the conveyed document reading position on the transparent reading sheet. This localized addition allows the system to maintain the overall simplicity of using a single transparent reading sheet while correcting the specific image concentration issue at the conveyed reading position through black reference correction.
2Device complexity
If a single contact glass is used for both fixed and conveyed document reading, then device complexity is reduced, but image concentration varies depending on the reading method
Solution Approach 1:
The black reference member is locally positioned at the conveyed document reading area of the single contact glass, enabling differential correction for the two reading methods while maintaining the simplicity of a unified contact glass structure.
3Productivity
If document passage is performed repeatedly through the transparent reading sheet, then productivity is improved, but small scratches form on the reading sheet surface causing image concentration degradation
Solution Approach 1:
The system performs preliminary black reference correction by reading the black reference member before actual document reading. This preliminary action captures the current state of the transparent reading sheet (including any scratches) and uses this information to correct subsequent document images, maintaining image concentration stability even as scratches accumulate from repeated document passage.
Solution Approach 2:
The black reference member provides continuous feedback about the transparent reading sheet's condition. By repeatedly reading the black reference member and updating the black reference data, the system adapts to changes in the reading sheet surface caused by document passage, thereby maintaining consistent image concentration over time.
4Manufacturing precision
If black reference correction is performed using initial concentrations, then initial image concentrations are matched, but continuous use causes image concentration change that cannot be corrected
Solution Approach 1:
The system performs preliminary reading of the black reference member before each document reading operation to obtain current black reference data. This preliminary action ensures that the black reference correction is based on the actual current state of the transparent reading sheet, not just initial conditions, enabling continuous operation consistency.
Solution Approach 2:
The system continuously monitors the black reference member and updates the black reference data based on current readings. This feedback mechanism allows the system to adapt to changes in the transparent reading sheet over time, maintaining reliable image concentration correction during continuous operation.
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
The solution effectively maintains image concentration even with small scratches on the transparent reading sheet, ensuring accurate reading of high concentration document areas by using corrected black data for shading correction.
Implementation Method 1
a small scratch increases as a result of repeated document passage. With this scratch, especially in a case where a document with high concentration (closer to black), irradiated light, which is originally absorbed to the document, is reflected on the scratch on the transparent reading sheet
Implementation Method 2
an image reading section moving in a predefined direction at below a fixed document reading region so as to read an image of the document
Data Source
AI summary
A document reading device (20) includes: a document conveyance section (6) and a document reading device (5). A conveyed document reading region (161b) has: a document discharge guide (51) arranged downstream of an image reading position (163a) in a document conveyance direction; and a transparent reading sheet (52) provided along a surface of the contact glass (161) and a surface of the document discharge guide (51), the document conveyance section (6) has a reading guide (62) forming a document conveyance path oppositely to the conveyed document reading region (161b), and the reading guide (62) has, on part of a surface opposing the conveyed document reading region (161b), a black reference member (620) optically read by an image reading section (163) for the purpose of correcting black reference data of an image of the document conveyed by the document conveyance section (6) and read by the document reading device (5).