Image Reading Device Document Size Determination
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Solution Overview
Problem
Image reading devices face challenges in accurately determining the size of card-type documents, especially when they have dark-colored surfaces, as the contrast between the document and the pressing plate is insufficient, making it difficult to recognize the document edges and determine its size accurately.
Innovation Solution
An image reading device with a document pressing portion that can be opened and closed, equipped with an image reader, image data generation circuit, and controller, which calculates the size of the document by analyzing image data from both sides in a double-side special mode, determining the larger sub scanning size to accurately measure the document's dimensions regardless of the pressing plate's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dark-colored card-type document is placed on the contact glass for reading, then the document can be read in the dedicated mode, but the contrast between the document and the pressing plate is insufficient, making it difficult to recognize the document edges and determine its size accurately
Solution Approach 1:
The system performs preliminary reading of the document before the pressing plate is fully closed. The controller reads the document when the pressing plate is in an open or partially closed state, before the document and pressing plate come into full contact. This preliminary action captures the document edges before the contrast degradation occurs, enabling accurate size determination even for dark-colored documents.
Solution Approach 2:
The controller uses feedback from the image sensor to determine the pressing plate's closed state. Based on this feedback, the controller adjusts the timing of the reading operation - performing the read before full closure when a dark-colored document is detected. This feedback mechanism allows the system to adapt to the document's color characteristics and avoid the contrast problem.
2Stability of the object's composition
If the pressing plate is closed to press the document for stable reading, then the document position is stabilized, but the contrast between the dark-colored document and the pressing plate becomes insufficient, hampering edge recognition
Solution Approach 1:
The system performs the reading action before the pressing plate is fully closed. By timing the read operation to occur when the pressing plate is still open or partially closed, the system captures the document edges when contrast is still sufficient. This preliminary action resolves the contradiction by obtaining stable document positioning without sacrificing edge recognition accuracy.
3Productivity
If the document size is determined based on pixel values from a single reading, then the reading process is simple and fast, but the size determination is inaccurate for dark-colored documents due to insufficient contrast
Solution Approach 1:
The system performs a preliminary read before the pressing plate is fully closed, when contrast is still sufficient. This preliminary reading captures the document edges accurately, and the controller uses this information to determine the document size. This approach maintains reading speed while improving accuracy for dark-colored documents.
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 accurate size determination of card-type documents even when one side is dark-colored, ensuring precise measurement and extraction of document content without losing or clipping unnecessary parts.
Implementation Method 1
The image reading device shines light toward the document. The image reading device reads the document based on reflected light.
Data Source
AI summary
On the basis of first read image data obtained by reading a first face, a controller calculates a first sub scanning size, which is a size of the first face in a sub scanning direction. On the basis of second read image data obtained by reading a second face, the controller calculates a second sub scanning size, which is a size of the second face in the sub scanning direction. The controller determines the larger of the first sub-scanning size and the second sub-scanning direction size to a definitive sub scanning size, which is the size of the document in the sub scanning direction set on the document stage.