Document Detection Offset for Accurate Image Capture
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Solution Overview
Problem
Existing image reading devices face issues with incomplete document scanning due to unstable document positioning, particularly when the document is inclined, leading to loss of the leading end in the reading result, as the document detection sensor's placement affects the transport accuracy and timing of image capture.
Innovation Solution
An image reading device with a first transport roller, a second transport roller, a reading unit, and a document detection unit positioned between the rollers, where the detection unit starts reading based on document detection and performs edge identification or specified size-based processing to ensure accurate capture of the document's leading end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the document detection sensor is disposed downstream of the feed roller with a short distance to the reading unit, then the reading can start promptly after document detection, but the leading end of the document may have already passed through the reading unit when reading starts, causing image loss
Solution Approach 1:
The patent positions the document detection sensor not only in the transport direction but also offsets it in the width direction by a first distance from the reading unit origin. This two-dimensional positioning allows the system to detect documents at multiple possible locations and compensate for transport variations, ensuring the leading end is captured even when documents are inclined or transport timing varies.
2Measurement precision
If the document detection sensor is disposed upstream of the feed roller, then the reading start timing can be determined in advance, but the distance from the detection sensor to the reading unit becomes long, causing transport accuracy to vary and the leading end position to be unstable
Solution Approach 1:
The patent divides the document detection function into multiple segments by positioning the detection sensor at an offset location in the width direction rather than directly in line with the reading unit. This segmentation allows the system to handle different document positions and transport variations more reliably, as the offset positioning creates a geometric relationship that compensates for transport inaccuracies.
Solution Approach 2:
The system uses the detection timing and position information from the offset detection sensor to calculate and adjust the reading start timing dynamically. This feedback mechanism allows the control unit to compensate for transport variations and ensure accurate capture of the document leading end, maintaining both timing precision and position stability.
3Device complexity
If the document detection sensor is positioned directly in line with the reading unit, then the positional relationship is simple, but when the document is inclined, the leading end may be lost in the reading result
Solution Approach 1:
The patent introduces a width direction offset (first distance) in addition to the transport direction positioning. This creates a two-dimensional detection geometry that can accommodate inclined documents. The offset positioning ensures that even when documents are angled, the detection trigger occurs at the appropriate moment to capture the leading end, without requiring complex mechanical adjustments.
Data Source
AI summary
When a size of a document is not specified, a control unit of an image reading device identifies, for image data generated as a reading result by a reading unit, a region of the document by detecting an edge of the document. When the size of the document is specified, the control unit searches the image data, at a position within a first range including a position away from an origin by a first distance, for a downstream end of the document from a downstream end of the image data toward upstream in a transport direction, and based on a position of the downstream end of the document identified by the searching, identifies as a region of the document a region corresponding to the size of the document specified.