Document Detection Accuracy in Image Scanners
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Solution Overview
Problem
Existing image reading apparatuses face challenges in accurately determining document size due to variations in the open/closed position and speed of the pressing plate, leading to potential false detection and reduced accuracy, especially when using recording media with high transmittance like tracing paper.
Innovation Solution
The image reading apparatus employs a line sensor and a control unit that uses coefficient data to determine the presence or absence of a document by comparing data acquired at intermediate and closed positions of the pressing plate, calculating threshold data based on reference data and coefficient values, which are adjusted for varying distances from the rotation axis, thereby improving detection accuracy regardless of pressing plate speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If data is acquired using a line sensor at different open/closed positions when a pressing plate is closed, then the size of a document can be determined by comparing the acquired data and a predetermined threshold, but variations in the open/closed position and speed of the pressing plate lead to false detection and reduced accuracy
Solution Approach 1:
The patent applies preliminary action by acquiring reference data at an intermediate position of the pressing plate before reaching the closed position. This reference data is used to calculate threshold values that account for mechanical variations. By performing this measurement in advance, the system establishes a baseline that compensates for position and speed variations during the closing operation, thereby improving both measurement precision and reliability
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting threshold values based on the relationship between reference data and actual measurement data. The threshold is not fixed but is calculated by multiplying reference data by a coefficient, allowing the detection parameters to adapt to variations in pressing plate position and speed, thus maintaining high detection accuracy under varying conditions
2Device complexity
If a predetermined threshold is used for document detection, then the detection process is simple, but it leads to false detection when using recording media with high transmittance like tracing paper
Solution Approach 1:
The patent changes the detection parameter from a fixed predetermined threshold to a dynamically calculated threshold. The threshold is computed by multiplying reference data (acquired at intermediate position) by a coefficient, allowing it to adapt to different document types including high-transmittance media like tracing paper. This parameter change maintains relatively simple processing while significantly improving detection accuracy
Solution Approach 2:
The system employs feedback by using reference data from the intermediate position to inform and adjust the threshold calculation for the closed position detection. This feedback mechanism allows the system to compensate for variations in pressing plate mechanics and document properties, improving detection accuracy without substantially increasing system 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
This approach enhances the accuracy of document size detection by accounting for mechanical errors and varying opening/closing speeds, reducing false detection and ensuring precise size determination across different types of recording media.
Implementation Method 1
a line sensor including an image sensor arranged in a main scanning direction intersecting the rotation axis and configured to output data by reading the document placed on the document table
Data Source
AI summary
An image reading apparatus includes a document table, a pressing plate that rotates about a rotation axis between an open position and a closed position, a line sensor that includes an image sensor arranged in a main scanning direction intersecting the rotation axis and outputs data by reading a document on the document table, and a control unit that determines presence or absence of the document based on first data acquired by the line sensor when the pressing plate is in an intermediate position before reaching the closed position and second data acquired by the line sensor when the pressing plate is in the closed position, wherein when the control unit determines the presence or absence of the document based on the first data and the second data, the control unit uses coefficient data that is smaller as a distance from the rotation axis is longer.