Light Guide Prism Asperities for LED Image Reading Efficiency
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Solution Overview
Problem
Image reading apparatuses using LED light sources face challenges in achieving high light use efficiency while maintaining good light distribution, as LED light sources are point sources and require improved light guiding technologies to achieve linear light distribution.
Innovation Solution
The design incorporates a light guide with a reflecting surface and a prism having asperities that are inclined, allowing for improved light reflection and distribution, along with a beam splitter to direct light into multiple light guides, optimizing light use efficiency and maintaining good light distribution without the need for denser prism pitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a light guide with conventional prism structure is used with LED point light source, then linear light distribution can be achieved, but light use efficiency is insufficient
Solution Approach 1:
The patent applies local quality by creating asymmetric asperities with different orientations in different regions of the light guide. Specifically, asperities in the first region have a first orientation while asperities in the second region have a second orientation different from the first. This regional differentiation optimizes light extraction efficiency at different positions along the light guide, resolving the contradiction between improving light use efficiency and maintaining good light distribution.
2Productivity
If denser prism pitch is used to improve light distribution, then light distribution quality improves, but device complexity increases
Solution Approach 1:
The patent segments the light guide into multiple regions (first region and second region) with different asperity orientations. This segmentation allows each region to be optimized independently for light extraction, achieving good overall light distribution without requiring uniformly dense prisms throughout the entire light guide, thereby reducing overall device complexity.
Solution Approach 2:
By assigning different orientations to asperities in different regions, the patent creates locally optimized structures that collectively achieve superior light distribution. This approach avoids the need for uniformly complex dense prism structures throughout the entire light guide, resolving the contradiction between light distribution quality and device 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
This solution enhances light use efficiency and allows for adjustable light emitting directions, simplifying the base structure and maintaining effective light distribution across the image reading area, even near the LED light sources.
Implementation Method 1
a prism configured to reflect light to the emitting surface
Implementation Method 2
a prism configured to reflect light to the emitting surface, the prism comprising a plurality of asperities formed on the reflecting surface
Implementation Method 3
a beam splitter having a splitting surface configured to total-reflect incident light so as to direct the light into the plurality of light guides
Data Source
AI summary
A light guide for use in an image reading apparatus. The light guide extends in a predetermined direction and includes: a reflecting surface being parallel to the predetermined direction; an emitting surface; and a prism configured to reflect light to the emitting surface. The prism includes a plurality of asperities formed on the reflecting surface. When viewed from a first direction orthogonal to the reflecting surface, at least one of the plurality of asperities includes a portion parallel to a predetermined curve or a predetermined straight line inclined from a second direction orthogonal to the predetermined direction.