Rod Light Guide Illumination for Document Reading Uniformity
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Solution Overview
Problem
Conventional illuminating devices for document reading struggle to achieve a wide effective illumination area with high uniformity of irradiance distribution in the subscanning direction, despite achieving high uniformity in the main scanning direction, due to manufacturing tolerances in light intensity and overlapping light intensity peaks.
Innovation Solution
The use of two rod-shaped light guides with arc-shaped light emitting faces and two flat light reflection faces, each with minute prisms, arranged symmetrically to create distinct light intensity peaks on either side of the document reading axis, ensuring a wider effective illumination area with uniform irradiance distribution in the subscanning direction, even with manufacturing tolerances in light intensity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If two rod-shaped light guides are arranged with light emitting elements at end faces facing opposite directions, then high uniformity of irradiance distribution in the main scanning direction is achieved, but the effective illumination area width in the subscanning direction is insufficient
Solution Approach 1:
The patent divides each light guide into multiple light emitting portions along its length, with each portion having a flat light reflection face. This segmentation creates multiple light intensity peaks that spread the illumination across a wider area in the subscanning direction while maintaining uniformity in the main scanning direction through the symmetric arrangement of these segments.
Solution Approach 2:
The patent introduces flat light reflection faces at specific locations on the light guides, creating localized light emitting portions with distinct optical properties. These localized modifications enable precise control over the irradiance distribution pattern, achieving both required illumination width and uniformity through strategic placement of reflection faces rather than uniform modification across the entire light guide surface.
2Illumination intensity
If light emitting elements are arranged at end faces of two light guides facing opposite directions, then high uniformity of irradiance distribution is achieved in main scanning direction, but manufacturing tolerances cause overlapping light intensity peaks that reduce illumination uniformity in subscanning direction
Solution Approach 1:
By segmenting each light guide into multiple light emitting portions with flat reflection faces, the patent creates a more robust illumination system. The multiple segments distribute the light output across several peaks, reducing the impact of manufacturing variations in any single segment on the overall illumination uniformity.
Solution Approach 2:
The patent employs asymmetric positioning of flat light reflection faces on the light guides, creating light intensity peaks at different positions. This asymmetric arrangement, combined with the symmetric overall configuration, ensures that manufacturing tolerances do not cause detrimental overlapping of peaks, as the peaks are deliberately positioned to complement rather than directly overlap.
3Device complexity
If conventional light guides are used with end face light emitting elements, then device complexity is low, but the effective illumination area does not meet the required width of ±3 mm or more from center position
Solution Approach 1:
The patent modifies the conventional light guide by introducing multiple flat light reflection faces along its length, dividing it into multiple light emitting portions. This segmentation approach achieves the required ±3 mm illumination width without requiring multiple separate light guides or complex optical systems, maintaining relative structural simplicity while expanding the effective illumination area.
Solution Approach 2:
The patent extends the light emission from a single end face configuration into a distributed pattern along the length of the light guide by adding flat reflection faces at multiple positions. This transforms the illumination from a point-source-like emission to a line-source distribution, effectively increasing the illumination area width without proportionally increasing 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 configuration allows for a required illuminance width of ±3 mm or more from the document reading axis in the subscanning direction with high uniformity of irradiance distribution, compensating for intensity variations between light guides.
Implementation Method 1
light from each light emitting element is guided in the longitudinal direction by the light guide and reflected by each of the two flat light reflection faces such that the light is emitted from the light emitting face of each light guide
Implementation Method 2
light from each light emitting element is guided in the longitudinal direction by the light guide and reflected by each of the two flat light reflection faces such that the light is emitted from the light emitting face of each light guide
Implementation Method 3
A group of minute prisms is formed on each of the two flat light reflection faces along with the longitudinal direction
Data Source
AI summary
A illuminating device used for an document reading apparatus that has two rod shape light guides and light emitting elements where each of the light guides has a light emitting face and two flat light reflection faces, which may have a group of minute prisms that are formed along the longitudinal direction of the faces, and where light from each light emitting element is guided in the longitudinal direction by the light guide and reflected by that faces, such that the light is emitted from the light emitting face of each light guide and a virtual plane that is vertical to a longitudinal direction of each of the two light guides has two light intensity peaks.