Dual-Light Image Reading Device for Accurate Document Edge Detection
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Solution Overview
Problem
Conventional image reading devices struggle to accurately distinguish between pixels with document data and those without, due to the similarity in reflectance and transmittance values of white paper and document data, leading to incorrect detection of document thickness and presence of holes.
Innovation Solution
The image reading device employs a dual-lighting mechanism with a first lamp for reflected light and a second lamp for transmitted light, using a light absorbing member and a determining unit to differentiate between document and non-document pixels based on density thresholds in first and second image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a white color plate is used as background member, then the background appears bright, but pixels with document data cannot be correctly distinguished from pixels without document data
Solution Approach 1:
The patent divides the reading process into two separate periods: first period for reflected light reading and second period for transmitted light reading. This segmentation allows the system to capture different types of information in each period, enabling accurate distinction between document pixels and background pixels by comparing results from both periods.
Solution Approach 2:
The patent employs periodic switching between two lighting modes: reflected light reading in the first period and transmitted light reading in the second period. This periodic action allows the system to collect complementary information from both reading modes, solving the problem of pixel distinction that cannot be achieved with a single static lighting configuration.
2Device complexity
If single lamp for reflected light reading is used, then device structure is simple, but document information such as holes and edges cannot be accurately detected
Solution Approach 1:
The patent makes the image reading device multi-functional by equipping it with both reflected light reading capability (first lamp) and transmitted light reading capability (second lamp). This allows a single device to perform multiple types of document analysis, including edge detection, hole detection, and background distinction, which cannot be achieved with a single lighting system.
Solution Approach 2:
The patent implements periodic switching between reflected light mode (first lamp on, second lamp off) and transmitted light mode (first lamp off, second lamp on). This periodic operation allows the system to collect complementary information from both reading modes, enabling accurate detection of document features such as edges and holes while maintaining a relatively simple device structure.
3Measurement precision
If transmitted light reading is added to distinguish pixels, then pixel distinction accuracy improves, but reading time increases due to multiple periods
Solution Approach 1:
The patent implements periodic switching between reflected light reading (first period) and transmitted light reading (second period) within a single reading cycle. By organizing the dual-mode reading into structured time periods, the system achieves accurate pixel distinction while maintaining efficient reading speed, as both types of information are collected in one coordinated operation rather than requiring separate reading passes.
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 enables accurate detection of document edges, inclination, and presence of holes, allowing for precise document size recognition and correction of image data, improving the overall reading accuracy.
Implementation Method 1
The first lamp emits light to the one side of the contact glass. The image sensor receives light emitted from the first lamp and reflected by the document.
Implementation Method 2
The image sensor receives light emitted from the first lamp and reflected by the document. The document is read based on the light reflected by the document.
Implementation Method 3
The second lamp is disposed on the one side of the contact glass. The second lamp is disposed at a position farther from the contact glass than the document feeding path so as to emit light to the image sensor.
Data Source
AI summary
An image reading device includes a contact glass, a first lamp, an image sensor, a first lamp, a light absorbing member, and a second lamp. When reading a document, in a first period, the first lamp is turned on while the second lamp is turned off. In a second period, the second lamp is turned on while the first lamp is turned off. On the basis of first image data obtained by reading in the first period and second image data obtained by reading in the second period, the control unit determines whether each pixel in the first image data is a pixel having read document data or not.