Multi-Wavelength Sheet Detection in Image Readers
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Solution Overview
Problem
Conventional image-reading devices face issues in accurately detecting the presence of a sheet at the read position due to interference from identification images on the pressing plate and incorrect determinations caused by deteriorated or soiled images.
Innovation Solution
An image reading device equipped with a light-emitting unit and a light-receiving unit that emit and receive multiple colored lights, allowing the controller to determine sheet presence by analyzing intensity relationships, distinguishing between reflections from a sheet and a non-sheet opposing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an identification image is depicted on the pressing plate to determine sheet presence, then the detection method is established, but the identification image adversely affects the image read by the image-reading unit and may cause incorrect determinations when deteriorated or soiled
Solution Approach 1:
The patent extracts and removes the identification image from the pressing plate, eliminating the source of interference. Instead of using an identification image, the system uses the natural reflection characteristics of the pressing plate surface to detect sheet presence, thereby removing the harmful effect while preserving the detection function
Solution Approach 2:
The patent changes the detection parameter from visual pattern recognition (identification image) to optical reflection intensity measurement. By measuring the intensity of reflected light at different wavelengths, the system can distinguish between sheet presence and absence based on reflection characteristics rather than visual patterns, eliminating interference from plate markings
2Measurement precision
If a single light source is used for reading, then the device complexity is reduced, but the ability to accurately determine sheet presence through intensity relationships is compromised
Solution Approach 1:
The patent makes the light-emitting unit multi-functional by incorporating multiple light sources with different spectral characteristics that serve both the primary reading function and the secondary sheet detection function. The same light-emitting unit that provides illumination for image reading also enables optical reflection measurement for sheet presence determination, eliminating the need for separate detection hardware
Solution Approach 2:
The patent changes the physical parameter of the light source from single-wavelength to multi-wavelength emission. By using light sources with different spectral characteristics, the system can measure reflection intensity relationships that are characteristic of sheet materials versus the pressing plate, enabling accurate sheet presence detection without additional hardware 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
Accurately determines sheet presence without reliance on identification images, reducing incorrect determinations and enhancing precision in leading and trailing edge detection.
Implementation Method 1
The first intensity relationships are defined by intensities of the plurality of lights that are emitted from the light-emitting unit, reflected by the opposing member, and received by the light-receiving unit
Data Source
AI summary
An image reading device includes a reading unit having a light-receiving unit and a light-emitting unit emitting a plurality of lights of different colors toward a reading position. An opposing member is disposed opposite the reading unit with the reading position interposed therebetween. The controller controls the light-emitting unit to emit the lights and the light-receiving unit to receive the lights thereby acquiring an intensity of each light. The controller determines that a sheet is not present when relationships among intensities of the plurality of lights are same as the first intensity relationships. The first intensity relationships are defined by intensities of the plurality of lights reflected by the opposing member and received by the light-receiving unit. The first intensity relationships are different from intensity relationships of the plurality of lights reflected by a sheet present at the reading position and received by the light-receiving unit.