Reading Background Layer Structure for Visible and Invisible Light
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Solution Overview
Problem
Existing image reading devices face challenges in maintaining sufficient whiteness and luminance of the background member due to the absorption of visible light by the transparent invisible light absorption layer, leading to issues like peeling of the white resin layer when increasing its thickness.
Innovation Solution
The background member is designed with a two-layer white resin structure, where a second white resin layer with higher visible light resistance is positioned upstream, followed by a transparent invisible light absorption layer, to maintain whiteness and luminance while reducing visible light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the white resin layer is increased to improve whiteness and luminance, then the visible light reflectance increases, but the coating film peels due to adhesion failure
Solution Approach 1:
The white resin layer is divided into two separate layers: a first white resin layer (26b) with thickness of 15-20 μm that ensures adhesion to the metal plate, and a second white resin layer (26c) with thickness of 15-20 μm that provides high whiteness and luminance. This segmentation allows each layer to perform its specific function without compromising the other, resolving the contradiction between adhesion and visual performance.
2Measurement precision
If a transparent invisible light absorption layer is added to detect document edges, then invisible light reflectance decreases improving edge detection, but visible light is absorbed reducing background member luminance
Solution Approach 1:
The background member is designed with spatially varying optical properties: the invisible light absorption layer (26d) is positioned upstream to selectively absorb invisible light for edge detection, while the two white resin layers (26b, 26c) are positioned downstream to reflect visible light and maintain high luminance. This local quality differentiation allows the same structure to perform both edge detection and luminance maintenance functions simultaneously.
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 prevents aging of the first white resin layer and maintains high whiteness and luminance, even when reflecting invisible light with lower reflectance than visible light, thereby enhancing image reading accuracy and longevity.
Implementation Method 1
an invisible light absorption layer to absorb the invisible light
Implementation Method 2
a first white resin layer and a second white resin layer on the first white resin layer, and an invisible light absorption layer on the second white resin layer. The background member includes... to reflect at least the visible light
Data Source
AI summary
A reading device includes a light source to irradiate a subject with visible light and invisible light in a light incident direction, an imager to receive the visible light and the invisible light reflected from the subject and image a visible image and an invisible image, and a background member disposed at an imaging region of the imager to reflect at least the visible light. The background member includes a first white resin layer and a second white resin layer on the first white resin layer, and an invisible light absorption layer on the second white resin layer. The second white resin layer has a visible light resistance higher than the first resin layer. The invisible light absorption layer absorbable the invisible light. The invisible light absorption layer, the second white resin layer, and the first white resin layer are disposed in this order in the light incident direction.