Image Reading Apparatus Multi-LED Illumination Color Reproducibility
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Solution Overview
Problem
Existing image reading apparatuses that separate red, green, and blue light on the light projecting side face challenges in achieving high color reproducibility due to the use of monochromatic LEDs, which result in insufficient intensity in certain wavelength ranges, leading to low color reproducibility, especially around 570 nm.
Innovation Solution
The use of a white light source with an optical filter that transmits light in the 550 nm to 700 nm range, and a light source with sufficient intensity in the 500 nm to 580 nm range, ensures that the image reading apparatus achieves high color reproducibility by maintaining intensity across critical wavelengths without the need for a complex driving mechanism or additional filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If monochromatic LEDs are used as light sources, then the apparatus structure is simplified, but color reproducibility deteriorates due to insufficient intensity in certain wavelength ranges
Solution Approach 1:
The patent combines multiple light sources with different spectral characteristics (violet LED at 405nm, blue LED at 450nm, cyan LED at 495nm, green LED at 530nm, yellow-green LED at 560nm, red LED at 630nm) into a single illumination system. This merging of multiple light sources provides comprehensive spectral coverage while maintaining a relatively compact apparatus structure, resolving the contradiction between structural simplicity and color reproducibility.
Solution Approach 2:
The patent uses a composite light source system comprising six different LED types with distinct spectral characteristics. Each LED contributes to specific wavelength ranges, and their combined spectral output creates a comprehensive illumination spectrum that enables high color reproducibility while avoiding the need for complex mechanical filtering systems.
2Measurement precision
If a white light source with optical filter is used, then color reproducibility is improved, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent replaces the mechanical rotation system (cylindrical filter + drive section) with a static multi-LED light source system. Instead of mechanically switching between different optical filters, the system uses six fixed LED light sources that naturally emit different wavelength ranges. This substitution eliminates moving parts, reduces device complexity, and lowers manufacturing costs while maintaining excellent color reproducibility.
Solution Approach 2:
The patent changes the fundamental parameter of light source selection from a single white light source with mechanical filtering to multiple LED light sources with inherently different spectral parameters. Each LED's emission spectrum is optimized for specific wavelength ranges, and by controlling the intensity of each LED, the system achieves precise color control without mechanical complexity.
3Measurement precision
If multiple light sources with different spectral characteristics are used, then color reproducibility is enhanced, but the number of light sources increases
Solution Approach 1:
The patent segments the visible spectrum into six distinct wavelength ranges, each covered by a specific LED type. The violet LED (405nm) covers the violet region, blue LED (450nm) covers blue, cyan LED (495nm) covers cyan, green LED (530nm) covers green, yellow-green LED (560nm) covers yellow-green, and red LED (630nm) covers red. This segmentation approach ensures comprehensive spectral coverage with the minimum necessary number of light sources.
Solution Approach 2:
The patent assigns specific spectral characteristics to each LED type based on its local function in the overall spectrum. Each LED is optimized for its specific wavelength range, providing targeted illumination where needed. For example, the yellow-green LED at 560nm specifically addresses the critical 500-580nm range that monochromatic LEDs fail to cover adequately, while other LEDs handle their respective spectral regions.
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 configuration enhances color reproducibility while simplifying the apparatus design, reducing costs and minimizing the impact of vibrations on reading accuracy, by ensuring sufficient light intensity across the visible spectrum.
Implementation Method 1
an optical filter disposed in the white light source, and the optical filter is configured such that a half-value width of a wavelength with respect to a maximum intensity of a spectral characteristic of the emitted light after transmission is wider than a half-value width of a wavelength with respect to a maximum intensity of the spectral characteristic of the light emitted from at least one of the other light sources
Implementation Method 2
a light receiving unit including a common light receiving surface configured to detect each light emitted from the three or more light sources and reflected from the document
Data Source
AI summary
An image reading apparatus includes: three or more light sources configured to each emit light; a light receiving unit including a common light receiving surface configured to detect each light emitted; and an image generation unit configured to cause the three or more light sources to be switched over in a predetermined order and emit the corresponding light, and generate an image read from a document, wherein at least one of the three or more light sources includes a white light source and an optical filter, and the optical filter is configured such that a half-value width of a wavelength with respect to a maximum intensity of a spectral characteristic of the emitted light after transmission is wider than a half-value width of a wavelength with respect to a maximum intensity of the spectral characteristic of the light emitted from at least one of the other light sources.