Light Guide Projected Portion for Planar Light Source Uniformity
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Solution Overview
Problem
Thinner planar light sources for direct-lit liquid crystal displays often suffer from luminance non-uniformity due to reduced distance between the light source and the emission face, leading to insufficient light diffusion.
Innovation Solution
A light emitting module design featuring a light guide with a projected portion and a recessed area containing a light source and a light transmitting part with a lower refractive index than the guide, along with oblique faces and reflecting members to diffuse light and reduce luminance concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the planar light source is made thinner to reduce distance between light source and emission face, then the thickness is reduced, but light diffusion becomes insufficient causing luminance non-uniformity
Solution Approach 1:
The light guide is designed with a projected portion having a planar face and oblique faces, creating local structural variations. The light transmitting part is positioned specifically on the projected portion, concentrating light diffusion efforts where needed most to address luminance non-uniformity in the thinned structure.
Solution Approach 2:
The oblique faces on the projected portion of the light guide create angled surfaces that redirect light paths. This geometric modification helps diffuse light more effectively across the emission face, compensating for the reduced diffusion distance caused by thinning the overall structure.
2Illumination intensity
If a light transmitting part with lower refractive index is introduced to enhance light diffusion, then luminance uniformity improves, but device complexity increases
Solution Approach 1:
The light transmitting part is integrated directly onto the projected portion of the light guide, merging the light diffusion function with the existing light guide structure. This integration approach enhances light diffusion while minimizing additional structural complexity.
Solution Approach 2:
The light transmitting part acts as an intermediary element between the light source and the emission face. By positioning it on the projected portion, it mediates light transmission and diffusion, improving luminance uniformity without requiring fundamental redesign of the entire light guide structure.
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 design effectively reduces luminance non-uniformity by diffusing light outwardly, moderating concentration in the central emission area and enhancing overall luminance uniformity.
Implementation Method 1
The light transmitting part is formed on the projected portion in an area surrounded by the wall portion, and has a lower refractive index than a reflective index of the light guide
Data Source
AI summary
An upper face of a light guide includes a projected portion that has a planar face, and a wall portion that surrounds the projected portion, wherein a top part of the wall portion is positioned higher than the planar face. A lower face of the light guide has a recessed portion. A light transmitting part that has a lower refractive index than a reflective index of the light guide is disposed on the projected portion in an area surrounded by the wall portion. A light source is disposed in the recessed portion. The projected portion has an oblique face which is oblique to the planar face and disposed between the planar face and the wall portion. In a plan view of the planar face of the projected portion, the oblique face of the projected portion is positioned outward of a lateral face of the recessed portion at least in part.