Skewed Sheet Width Detection Using Bidirectional Edge Scanning
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Solution Overview
Problem
Existing image processing apparatuses inaccurately determine the sheet width of skewed sheets during image reading, especially when starting to read from the leading end area, leading to incorrect sheet size calculations.
Innovation Solution
An image reading apparatus equipped with a line sensor and a controller that scans the sheet in both directions, uses a line sensor with multiple sensor components to read images, and determines edge positions within specific ranges to accurately calculate the sheet width by identifying leading and lateral end positions, even when the sheet is skewed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the image processing apparatus determines the sheet edge position by scanning from the central position in the main-scanning direction, then the reading process is simplified and faster, but the measurement precision of sheet width deteriorates when the sheet is skewed or when reading starts from a midst position
Solution Approach 1:
The patent divides the sheet edge detection into multiple segments: first detecting the leading end position by scanning from the central position, then detecting the lateral end positions by scanning in both upstream and downstream directions. This segmentation allows the system to maintain fast reading speed while achieving accurate sheet width measurement through multi-stage detection.
Solution Approach 2:
The system uses feedback by continuously monitoring edge detection results during scanning. When an edge is detected at a position different from the expected central position, the system adjusts subsequent scanning parameters and calculations to compensate, ensuring accurate sheet width determination even when starting from a midst position.
2Device complexity
If the apparatus scans only from the central position in one direction, then the device complexity is reduced, but the reliability of edge detection deteriorates when the sheet is skewed
Solution Approach 1:
The detection process is segmented into multiple scanning phases: initial detection from central position, followed by bidirectional scanning to confirm edge positions. This segmentation maintains relatively simple device structure while improving reliability through systematic multi-phase verification of edge positions.
Solution Approach 2:
The system performs preliminary scanning from the central position to identify the leading end position before conducting the main bidirectional scanning for lateral end detection. This preliminary action prepares the system by establishing reference points, thereby improving the reliability of subsequent edge detection without significantly increasing device complexity.
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
Enables precise determination of sheet width and size in the main-scanning direction, ensuring accurate image correction and trimming, even when the sheet is skewed and read from the leading end area.
Implementation Method 1
Each sensor component is configured to read an image element corresponding to a pixel on the sheet
Data Source
AI summary
An image reading apparatus, having a conveyer, a sheet tray, an obtaining device, a memory, a determining device, and a controller, is provided. The controller determines whether information concerning pixels in the memory indicates edge positions or edge absence in in read-image data concerning a sheet, detects an upstream leading-end position and a downstream leading-end position, detects upstream continuing pixels and downstream continuing pixels, detects an upstream lateral-end position and a downstream lateral-end position, calculates a line representing an upper end of the sheet based on the upstream leading-end position and the downstream leading-end position, calculates an upstream corner position and a downstream corner position based on the upstream and downstream lateral-end positions and the line representing the upper end of the sheet, and calculates a width of the sheet based on the upstream corner position and the downstream corner position.