Light Guide with Arc-Like Cross-Section for Uniform Illuminance
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Solution Overview
Problem
Image reading apparatuses face challenges in achieving high illuminance uniformity in both the reading depth direction and the sub-scanning direction due to the limitations of existing light guide configurations, which result in uneven illumination and reduced illuminance in certain areas, especially when dealing with non-flat reading surfaces like books or banknotes.
Innovation Solution
A light guide with an arc-like outer shape in its transversal cross-section, featuring a light scattering portion and a light emitting surface portion composed of continuous first and second surfaces, where the first surface has a longer circumference and increasing curvature away from the second surface, ensures uniform illuminance distribution by directing light effectively across the reading area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional light guide configuration is used, then the structure is simple, but the illuminance uniformity in the reading depth direction and sub-scanning direction deteriorates
Solution Approach 1:
The light guide employs an arc-like outer shape in the transversal cross-section instead of a conventional straight or simple geometric shape. This curvature design modifies the light propagation path and emission characteristics, achieving uniform illuminance distribution in both the reading depth direction and sub-scanning direction while maintaining a relatively simple overall structure.
Solution Approach 2:
The light guide incorporates a light scattering portion at specific locations to locally modify light emission properties. This localized scattering mechanism ensures uniform illuminance distribution without requiring complex overall structural changes, resolving the contradiction between simplicity and uniformity.
2Illumination intensity
If light is emitted from a conventional light guide, then the light source is simple, but the luminous flux density and illuminance uniformity deteriorate
Solution Approach 1:
The arc-like outer shape of the light guide in the transversal cross-section optimizes light emission by creating favorable light propagation paths. This curvature design increases luminous flux density while maintaining uniform illuminance distribution, achieving high illumination quality without complex internal structures.
Solution Approach 2:
The invention changes the geometric parameters of the light guide, specifically implementing an arc-like shape with controlled radius of curvature. This parameter modification optimizes light emission characteristics, achieving high luminous flux density and uniform illuminance without adding complex components.
3Illumination intensity
If existing light guide configurations are used, then the manufacturing is simple, but the illuminance uniformity across the reading area deteriorates
Solution Approach 1:
The arc-like outer shape can be manufactured using conventional molding techniques by simply adjusting the mold geometry. This approach achieves uniform illuminance across the reading area without requiring complex multi-step manufacturing processes or additional assembly steps.
Solution Approach 2:
The invention modifies the geometric parameters of the light guide (arc radius, curvature profile) which can be directly implemented in the manufacturing mold. This parameter-based design approach maintains manufacturing simplicity while achieving superior illuminance uniformity across the reading area.
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 achieves high luminous flux density and maintains uniform illuminance across the reading area, reducing variations in illuminance both in the depthwise and transversal directions, thereby enhancing the overall image quality.
Implementation Method 1
a light scattering portion (2a) that is formed on a side surface of the light guide along the longitudinal direction and reflects light guided inside the light guide
Implementation Method 2
a light emitting surface portion that includes at least a part of the outer shape portion and is formed on a side surface along the longitudinal direction located opposite to the light scattering portion (2a), and emits light reflected by the light scattering portion (2a) to the outside of the light guide
Data Source
AI summary
A light guide including a light scattering portion that reflects light guided inside the light guide, and a light emitting surface portion emitting light reflected by the light scattering portion to outside the light guide. A light emitting surface portion includes first and second light emitting surface portions, the first light emitting surface portion has a longer circumferential length than that of the second light emitting surface portion in the transversal cross section, and circumference curvature of the first light emitting surface portion in the transversal cross section increases away from the second light emitting surface portion. A normal line to the light scattering portion, passing through the center of the light scattering portion in the transversal cross section, intersects with the first light emitting surface portion, at a point at a near side to the second light emitting surface portion in the transversal cross section.