Light Guide Protrusion for Image Reading Leakage Control
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Solution Overview
Problem
Conventional image reading apparatuses with light guides experience non-uniform light distribution due to light leakage from positioning bosses, requiring frequent reconfiguration and increased costs when LED arrangements change, and existing solutions either increase device size or fail to adequately reduce light leakage.
Innovation Solution
A light guide with a protrusion portion positioned downstream of the reflection portion, outside the main light flux path, to minimize light leakage and allow arbitrary positioning of bosses along the light guide, reducing the need for reconfiguration and device elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If positioning bosses are provided on the bottom surface of the light guide element, then alignment with the housing member is achieved, but light flux leaks from the positioning bosses causing non-uniform light distribution
Solution Approach 1:
The light guide element is designed with different properties in different regions: the bottom surface has positioning bosses for alignment, while the side surface has a light-shielding protrusion to prevent light leakage. This local differentiation allows the same component to simultaneously achieve alignment precision and eliminate harmful light leakage.
2Object-generated harmful factors
If positioning bosses are disposed between LED elements in the longitudinal direction, then light leakage is reduced, but the light guide element must be newly created when LED arrangement changes, increasing cost
Solution Approach 1:
The positioning function is segmented from the light guide element's optical path. The light-shielding protrusion is provided on the side surface of the light guide element, separate from the positioning bosses on the bottom surface. This segmentation allows the positioning bosses to remain in fixed positions while the light-shielding protrusion adapts to different LED arrangements by being positioned outside the effective light range.
Solution Approach 2:
The light-shielding protrusion acts as an intermediary element that mediates between the positioning bosses and the LED elements. It blocks light from reaching the positioning bosses and prevents leakage, while its position outside the effective light range allows it to not interfere with the optical path regardless of LED arrangement changes.
3Object-generated harmful factors
If positioning bosses are provided outside effective ranges of the light guide element, then light leakage is prevented, but the entire length of the light guide element is increased
Solution Approach 1:
Instead of extending the light guide element in the longitudinal direction to place positioning bosses outside effective ranges, the solution uses the lateral dimension by providing the light-shielding protrusion on the side surface of the light guide element. This dimensional change allows the positioning bosses to be positioned outside the effective light range without increasing the overall length of the light guide element.
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 significantly reduces light leakage to 2% or less, maintaining uniform illumination and eliminating the need for reconfiguring the light guide with changes in LED arrangements, while maintaining a compact device size.
Implementation Method 1
most of light flux incident from the LED element 10 to the light guide element 12 is propagated through a light guide portion 14
Implementation Method 2
is deflected by a reflection portion 15
Data Source
AI summary
A light guide includes an incidence surface configured to allow light from a light emitting unit to enter the light guide, a light guide portion configured to propagate the light entering via the incidence surface, a reflection portion configured to reflect the propagated light, an exit surface configured to allow light reflected on the reflection portion to exit, and a protrusion portion configured to position the light guide, wherein the protrusion portion is provided downstream of the reflection portion.