Document Skew Detection via Boundary Point Approximation
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Solution Overview
Problem
Conventional methods for detecting the skew of a document sheet are inaccurate and time-consuming, especially when dealing with documents of varying thickness or uneven edges, and rely on complex image processing techniques like Hough transform.
Innovation Solution
A device that uses a light source to scan the document, detects boundary points between the document and background, sets a boundary point group of interest, and determines the skew by approximating an oblique line through these points, reducing error and improving detection speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional image processing methods (Hough transform, least squares) are used to detect skew, then detection accuracy can be achieved, but detection time becomes excessively long
Solution Approach 1:
The patent segments the document edge detection task by identifying only boundary points between the document and background, rather than processing the entire image. This selective approach to detecting only relevant edge points significantly reduces computational complexity while maintaining skew detection accuracy
Solution Approach 2:
The patent extracts only the essential information needed for skew detection by focusing on boundary points between the document and background. This extraction of critical data points eliminates unnecessary computational overhead associated with processing the complete image, achieving both speed and accuracy
2Productivity
If shadow-based methods are used to detect skew, then detection can be performed, but accuracy deteriorates when documents have varying thickness or uneven edges
Solution Approach 1:
The patent introduces a background plate as an intermediary element that creates a consistent reference background. This mediator enables reliable boundary detection between the document and background regardless of document thickness or edge conditions, as the background plate provides a uniform reference that is always detectable
Solution Approach 2:
The patent uses the background plate to create a consistent background copy or reference that remains unchanged regardless of document variations. This reference background serves as a stable basis for detecting document boundaries and calculating skew, eliminating the problems associated with shadow-based methods
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 enables accurate and rapid detection of document skew independent of the document's state, improving detection speed and precision compared to traditional methods.
Implementation Method 1
a light source (24) that applies light to the document (8), and a scan portion (27) that scans, by the light source (24), reflected light from the document (8) to obtain an input image
Data Source
AI summary
A device for detecting an amount of skew in a document placed on a plate is provided. The device includes: a scanner for scanning an area including an edge of the document; a detector for detecting a boundary point between the document and the plate; a portion for setting a boundary point group of interest including boundary points; a portion for setting a midpoint of an oblique line for approximating the edge of the document; a portion for setting, as the oblique line, a line which passes through the midpoint and slants to the main scanning direction; a portion for modifying an amount of skew of the oblique line; and a portion for determining that an amount of skew in the document is an amount of skew of the oblique line having the error equal to a threshold or smaller.