Light Guide Diffusing Surface for Image Reading Contrast
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Solution Overview
Problem
Image reading apparatuses face a reduction in contrast between paper sheets and backgrounds due to re-illumination light, which is not effectively addressed without increasing the number of components or complicating the configuration.
Innovation Solution
The apparatus includes a transmission light source unit with a first light guide featuring a diffusing surface with concave or convex portions inclined relative to the light emission surface, which reduces re-illumination by diffusing light and preventing it from entering the image sensor unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a polarizing filter and light blocking sheet are arranged between the linear light source and the light guide to prevent re-illumination light, then the contrast between paper sheet and background is improved, but the number of components increases and the configuration becomes complicated
Solution Approach 1:
The patent combines the light diffusing function and the re-illumination prevention function into a single light guide structure. The light guide includes a light incident surface, a light emission surface, and a light diffusing surface with reflective portions, integrating multiple functions that would traditionally require separate components like polarizing filters and light blocking sheets.
Solution Approach 2:
The light guide serves multiple functions: it guides light from the linear light source, diffuses the light through the light diffusing surface, prevents re-illumination through the reflective portions, and maintains optical efficiency. This multi-functional design eliminates the need for additional specialized components.
2Adaptability or versatility
If the transmission light source unit and image sensor unit are arranged to face each other across the conveyance path, then transmission reading is enabled, but re-illumination light enters the image sensor unit reducing image contrast
Solution Approach 1:
The light diffusing surface has specific reflective portions with predetermined orientations that selectively control light directions. These localized reflective features redirect re-illumination light away from the image sensor while maintaining light transmission functionality, creating different optical properties in different regions of the light guide.
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 suppresses re-illumination light, enhancing the contrast between the paper sheet and background without adding components, thereby improving image quality and accuracy in reading high-brightness paper sheets.
Implementation Method 1
a first light diffusing surface that is provided on an opposite side of the first light emission surface and that diffuses the light emitted by the first light source
Implementation Method 2
the first light diffusing surface is provided with at least one of concave portions and convex portions including inclined surfaces inclined relative to a normal line of the first light emission surface
Data Source
AI summary
A transmission light source unit includes a first light source portion including: a first light source; and a first light guide that shapes light emitted by the first light source into a line and emits the light toward a conveyance path of a paper sheet. An image sensor unit includes: a second light source portion that emits light toward the conveyance path of the paper sheet; and an image sensor that detects the light emitted by the first light source portion and transmitted through the paper sheet and the light emitted by the second light source portion and reflected by the paper sheet. A first light diffusing surface of the first light guide is provided with at least one of concave portions and convex portions including inclined surfaces and inclined relative to a normal line of the first light emission surface.