Surface Light Source Device Brightness Uniformity
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Solution Overview
Problem
Edge-light type surface light source devices experience significant variation in in-plane distribution of brightness perceived by viewers, despite being designed for uniform front-direction luminance and angular distributions.
Innovation Solution
A surface light source device with a light guide plate and two light sources positioned on opposing sides, along with a light control sheet, where the angular distribution of luminance is optimized by adjusting peak angles and the ratio of unit optical element dimensions to ensure uniform brightness across the emitting surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an edge-light type surface light source device is designed with uniform front-direction luminance and angular distributions, then high front-direction luminance is achieved, but considerable variation is produced in the in-plane distribution of brightness perceived by a viewer
Solution Approach 1:
The patent applies local quality by making the light guide plate have different refractive indices at different locations. Specifically, the refractive index is higher near the light source and gradually decreases toward the opposite side. This spatial variation in optical properties compensates for the non-uniform light distribution, ensuring uniform perceived brightness across the light emitting surface while maintaining high front-direction luminance.
2Ease of operation
If a diffusing component is dispersed in the light guide plate to allow light to gradually exit, then light distribution is improved, but significant variation in in-plane brightness distribution still occurs
Solution Approach 1:
The patent changes the optical parameter (refractive index) of the light guide plate as a function of position. By continuously or stepwise varying the refractive index from the light source side to the opposite side, the patent achieves uniform light extraction and perceived brightness distribution, overcoming the limitations of uniform diffusing component dispersion.
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 effectively equalizes the in-plane distribution of perceived brightness, enhancing the uniformity of brightness across the display surface and improving the overall image quality by adjusting the light exit angles and distribution patterns.
Implementation Method 1
The light that has entered the light guide plate repeatedly reflects from a pair of the opposing main surfaces and travels in the light guide plate in a direction (light guide direction) almost perpendicular to the light entrance surface
Implementation Method 2
By changing the travel direction of light by the diffusing component, the light is allowed to gradually exit the light guide plate at varying positions along the light guide direction
Data Source
AI summary
A surface light source device has a light emitting surface and includes a light guide plate having a light exit surface and a pair of light entrance surfaces. When the angular distribution of luminance in a plane parallel to a first direction is measured on the light emitting surface at varying positions along the first direction, the peak angle θc in the angular distribution of luminance at a center position Pc in the first direction lies between the peak angle θa in the angular distribution of luminance at an end position on one side in the first direction and the peak angle θb in the angular distribution of luminance at an end position on the other side in the first direction.