Bidirectional Light Guide with Convex Exit Portions
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Solution Overview
Problem
Conventional light guides for image reading devices face challenges in manufacturing complexity, stray light issues due to intersecting light diverting surfaces, and uneven illuminance across the document surface, leading to reduced efficiency and compatibility with high-brightness light sources.
Innovation Solution
A bidirectional light guide with a first and second exit portion having convex curved surfaces, connected through a concave shape, and a reflecting portion that intersects the optical axes of both exit portions, allowing for efficient light emission in two directions with controlled orientation angles and reduced stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If light diverting surfaces are arranged to intersect in conventional light guides, then light can be emitted in multiple directions, but manufacturing complexity increases and stray light occurs at boundary areas
Solution Approach 1:
The light guide is divided into multiple independent light guide units, each with a single light diverting surface. These segmented units are arranged in parallel to collectively achieve multi-directional light emission, avoiding the complexity of intersecting surfaces in a single unit while maintaining the desired optical functionality.
Solution Approach 2:
Multiple light guide units are combined in parallel configuration to achieve the functional equivalent of a complex intersecting light guide. By merging simpler individual units, the system achieves multi-directional light emission without the manufacturing complexity and stray light problems associated with intersecting surfaces.
2Ease of operation
If light diverting surfaces are arranged to intersect, then multiple light directions are achieved, but stray light exits from boundary areas between exit portions
Solution Approach 1:
By segmenting the light guide into separate units with non-intersecting light diverting surfaces, each unit independently controls light emission in its designated direction. This segmentation prevents stray light from occurring at boundary areas between exit portions, as there are no intersecting surfaces creating unwanted light paths.
3Volume of moving object
If the cross section of the light guide is reduced, then device size is minimized, but the entry surface area decreases causing poor matching with high brightness light sources
Solution Approach 1:
Multiple light guide units are combined in parallel, where each unit has a smaller individual cross-section suitable for compact device size. Collectively, these units provide sufficient total entry surface area to match high brightness light sources, resolving the contradiction between miniaturization and light source compatibility.
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
The solution results in a compact, easy-to-assemble light guide with high illumination efficiency, effectively addressing the issues of manufacturing complexity and uneven illuminance, while enhancing compatibility with high-brightness light sources.
Implementation Method 1
a reflecting portion for reflecting light entering the light guide to each of the first exit portion and the second exit portion
Data Source
AI summary
A light guide includes a first exit portion emitting first exiting light, a second exit portion emitting second exiting light in a different direction than the first exiting light, and a reflecting portion reflecting light entering the light guide to each of the first and second exit portions. The first and second exit portions respectively have first and second curved surfaces each having a convex cross section perpendicular to the long axis direction. The second exit portion is connected to the first exit portion in the direction perpendicular to the long axis direction. The reflecting portion is provided, in a plane facing the first exit portion and the second exit portion, at a position shifted in the direction perpendicular to the long axis direction from a position where a normal to the plane passes through a connection portion between the first and second exit portions.