Rod Light Guide with Region-Specific Scattering Patterns

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Solution Overview

Problem

Existing rod-like light guides in image readers suffer from uneven color illumination due to angular dependency in light scattering patterns, leading to reduced light intensity and color unevenness, especially near the incident end face.

Innovation Solution

The light guide features light scattering patterns that are angular-independent near the incident face, using fine hemispherical concaves, and angle-dependent further away, with triangular or half-cylindrical grooves aligned with the width direction, reducing manufacturing costs and preventing color emphasis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If triangular grooves are used as light scattering patterns, then light can be directed toward the light-emitting surface, but color unevenness occurs due to angular dependency

Engineering Contradiction:

Improvelight intensity distributionVSAvoidcolor uniformity

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The light scattering patterns are divided into two regions with different characteristics: near the incident end face, hemispherical concaves are used to scatter light in all directions (angular-independent); away from the incident end face, triangular grooves are used to direct light toward the light-emitting surface (angular-dependent). This local differentiation resolves the contradiction by applying different scattering mechanisms to different regions, ensuring both color uniformity near the source and effective light directionality farther away.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If white pigment is printed by silk screen printing, then light scattering patterns can be formed, but manufacturing cost increases and characteristics disperse

Engineering Contradiction:

Improvelight scattering pattern consistencyVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent replaces the mechanical silk screen printing process with an injection molding process. Concavo-convex patterns are formed directly in the mold cavity, and these patterns are then formed on the light guide surface through injection molding. This substitution eliminates the need for separate printing steps, reduces manufacturing complexity, and ensures consistent patterns across all light guides.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The mold cavity is pre-formed with the desired concavo-convex patterns before injection molding. This preliminary formation of the pattern structure in the mold ensures that identical, consistent light scattering patterns are replicated in each light guide without requiring post-processing or printing steps, thereby reducing manufacturing cost and improving precision.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If light scattering patterns have angular dependency, then light can be directed efficiently, but color unevenness is emphasized near the incident end face

Engineering Contradiction:

Improvelight emission efficiencyVSAvoidcolor uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

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 design ensures consistent light intensity across colors and reduces color unevenness, maintaining equal light distribution without extraordinary rises in intensity, thereby improving image quality in image readers.

Implementation Method 1

light propagating inside the rod-like light guide is scattered by light scattering patterns formed on a side of the rod-like light guide and scattered light is illuminated on the document surface

Methodology Applied

Scientific EffectLight scattering: Scattering

Implementation Method 2

the light scattering patterns have a shape with an angular dependency whereby light is reflected by the patterns in the direction toward the light-emitting surface

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS7812304B2Light guide having light scattering patterns with different light reflected directions

Publication Date: 2010.10.12 NIPPON SHEET GLASS CO LTD

AI summary

A rod-shaped light guide which does not cause unevenness in color at the portion near an incident face is produced by injection-molding transparent resin such as acryl and its surfaces include a light-emitting surface, a bottom face, left and right sides and end faces. One end face opposes a light emitting unit, and light scattering patterns for scattering light incident from the end face are formed on the bottom face. The light scattering patterns are different in shape between a portion near the end face as the incident face and a portion away from the end face. The light scattering patterns formed at the portion near the incident face are composed of a large number of fine hemispherical concaves, whereas the light scattering patterns at the portion away from the incident face are composed of triangular grooves or half cylindrical grooves, and the axial direction of these triangular grooves or half cylindrical grooves coincides with the width direction (sub-scanning direction) of the bottom face on which the patterns are formed.