Planar Light Source Device Uniform Illumination
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Solution Overview
Problem
Existing surface light source devices using multiple light-emitting elements suffer from significant luminance unevenness between high and low luminance regions, which previous methods have been unable to adequately address.
Innovation Solution
A surface light source device is designed with a light-emitting device and a light flux controlling system comprising a first, second, and third light flux controlling member, along with a diffusion member, where the light flux controlling members are configured to control light distribution and include specific optical surfaces and shapes to ensure uniform illumination, and an air layer is interposed between the diffusion member and the light-emitting device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple light-emitting elements are used in a surface light source device, then the luminous output is increased, but luminance unevenness occurs between high and low luminance regions
Solution Approach 1:
The light flux controlling member is divided into multiple independent light flux controlling portions, each corresponding to a specific light-emitting element. This segmentation allows independent optimization of light distribution for each element, enabling the system to maintain high luminous output while achieving uniform luminance across the emission surface by controlling each segment's light contribution.
Solution Approach 2:
Each light flux controlling portion has locally optimized optical properties including varying refractive indices and curvature radii. The first and second light flux controlling portions have different optical characteristics tailored to their respective positions, allowing precise control of light distribution to eliminate luminance unevenness while maintaining overall high luminous output.
2Illumination intensity
If irregular parts are formed on boundary lines between lenses, then luminance unevenness is reduced, but manufacturing complexity increases
Solution Approach 1:
Multiple light flux controlling portions are merged into a single integrated light flux controlling member formed as one piece. This eliminates the need for separate irregular part formation processes on boundary lines, reducing manufacturing complexity while maintaining the light distribution control functionality needed for luminance uniformity.
Solution Approach 2:
The continuous light flux controlling member performs multiple functions: it controls light flux from multiple light-emitting elements, provides gradual refractive index transitions, and eliminates boundary effects simultaneously. This multi-functionality achieves luminance uniformity without requiring separate manufacturing steps for irregular boundary features.
3Illumination intensity
If complex light flux controlling structures are used, then luminance uniformity is improved, but device complexity increases
Solution Approach 1:
The light flux controlling portions provide sufficient light distribution control through their optical properties without requiring overly complex structures. The gradual refractive index change and appropriate curvature radii are optimized to achieve the needed luminance uniformity with minimal structural complexity, avoiding excessive design.
Solution Approach 2:
The optical parameters of the light flux controlling portions, including refractive index distribution and curvature radius, are optimized to achieve luminance uniformity. By carefully selecting and adjusting these parameters, the patent achieves uniform light distribution without requiring complex structural arrangements, thus reducing overall 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
The solution effectively reduces luminance unevenness, providing a more uniform illumination across the display region, even when using multiple light-emitting elements, thereby enhancing the performance of head-up displays and similar applications.
Implementation Method 1
a diffusion member disposed with an air layer interposed between the diffusion member and the light-emitting device, the diffusion member being configured to be irradiated with light emitted from the light-emitting device
Implementation Method 2
The first light flux controlling member includes a first incidence surface having a concave shape, the first incidence surface being disposed opposite the plurality of light-emitting elements so as to intersect a first central axis of the first light flux controlling member
Data Source
AI summary
When the focal distance of the first luminous flux control member is f, and the distance between a first central axis and an optical axis in the light emitting element separated farthest from the first central axis is d, the planar light source device satisfies −0.6<d/f<0. Also, when the width in the cross section including the central axis of the lens surface is w, the radius of curvature of the lens surface is R, and the distance between the diffusion member and the intersection point of the center line of the lens surface and the surface at the diffusion member side in the third luminous flux control member is t, the planar light source device satisfies 0<w2/t<0.85 and 0.4<w/R<1.4.