Document Skew Correction in Image Reading Devices
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Solution Overview
Problem
Existing image reading devices face challenges in accurately detecting and correcting document skew, leading to potential jamming and damage during the printing process, especially with large or indexed documents, as existing methods either stop the document too close to the reading position or fail to measure skew accurately due to document size and layout.
Innovation Solution
The implementation of a document transport system with a skew correcting member, detecting members, and a controller that measures skew amount based on time periods and document size, allowing for precise skew correction and stopping the document transport if the skew exceeds a predetermined value, thereby reducing damage and improving reading accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the document transport is stopped close to the reading position for accurate reading, then reading accuracy is improved, but the risk of jamming and damage increases
Solution Approach 1:
The skew correcting member performs skew correction in advance before the document reaches the reading position. The transport stopping unit stops the document upstream of the reading position after skew correction is completed, preventing jamming while ensuring the document is properly aligned for accurate reading.
2Measurement precision
If skew correction is performed for all documents, then reading accuracy is improved, but processing time increases
Solution Approach 1:
The detecting members detect the presence and position of the document, providing feedback to the control unit. The control unit determines whether skew correction is necessary based on detection results and adjusts the skew correcting member accordingly, avoiding unnecessary correction operations and improving processing efficiency.
3Object-affected harmful factors
If the skew correcting member is positioned upstream for safer stopping, then damage risk is reduced, but skew measurement accuracy deteriorates
Solution Approach 1:
The detecting members act as intermediaries between the skew correcting member and the reading position. They detect document position and provide information to the control unit, which coordinates the skew correction and stopping operations to achieve both accurate measurement and safe stopping position.
Data Source
AI summary
An image reading device includes a document container; a document transport path; a reading member that reads an image of a document passing a predetermined read position; a skew correcting member that corrects a skew of the document; a first detecting member that detects the document; a second detecting member that detects the document; a correction switcher that performs switching in accordance with whether or not skew correction is to be executed at the skew correcting member; a skew-amount measurer that measures a skew amount of the document based on a first time period if the skew of the document is to be corrected, and that measures the skew amount based on a second time period if the skew of the document is not to be corrected; and a transport stopping unit that stops transporting of the document if the skew amount exceeds a predetermined skew amount.