Dual Light Guide Plate for Uniform Luminance
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Solution Overview
Problem
Existing planar light source devices for liquid crystal display devices face challenges in reducing the number of light sources while maintaining uniform luminance, as luminance unevenness increases with fewer light emitting elements.
Innovation Solution
The implementation of a lighting device with a first light guide plate and a second light guide plate, where the first light guide plate includes a light entering surface, a light exit surface, and a diffusion portion to refract light in a crossing direction, and the second light guide plate includes a light entering surface, a light exit surface, and a diffusion portion with inclined lenses to further diffuse light in the arrangement direction, effectively reducing luminance unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the number of light emitting elements is reduced, then device complexity and cost are reduced, but luminance unevenness increases
Solution Approach 1:
The light guide plate is divided into multiple sections (first light guide plate section, second light guide plate section, third light guide plate section) with different diffusion structures. Each section handles light diffusion differently: the first section uses a first diffusion portion to scatter light in the crossing direction, the second section uses a second diffusion portion with inclined lenses to diffuse light in the arrangement direction, and the third section provides additional diffusion. This segmentation allows effective luminance uniformization even with reduced light source count.
Solution Approach 2:
Different regions of the light guide plate are equipped with diffusion portions having different optical characteristics. The first diffusion portion has a specific inclination angle range (30°-60°) to control light scattering in the crossing direction, while the second diffusion portion has inclined lenses with inclination angles (35°-55°) for diffusion in the arrangement direction. These localized optical modifications address luminance unevenness at specific locations without requiring additional light sources.
2Ease of manufacture
If the number of light emitting elements is reduced, then manufacturing cost decreases, but luminance uniformity deteriorates
Solution Approach 1:
Multiple diffusion functions are merged into a single integrated light guide plate structure. The first diffusion portion, second diffusion portion with inclined lenses, and third diffusion portion are combined in one component, eliminating the need for separate diffusion sheets or additional light sources. This integration maintains luminance uniformity while simplifying the overall system and reducing manufacturing complexity.
Solution Approach 2:
The optical parameters of the light guide plate are optimized by controlling the inclination angles of the diffusion portions. The first diffusion portion uses inclination angles of 30°-60°, the second diffusion portion uses 35°-55°, and the third diffusion portion uses 20°-70°. By adjusting these angular parameters, the patent achieves effective light diffusion and luminance uniformity without increasing the number of light sources.
3Illumination intensity
If diffusion action is increased to suppress luminance unevenness, then luminance uniformity improves, but light use efficiency may decrease
Solution Approach 1:
The diffusion portions use inclined surfaces and lens structures with curved geometries to refract and scatter light. The inclined lenses in the second diffusion portion and the sloped surfaces in the first and third diffusion portions create controlled light redirection paths. These curved optical elements efficiently distribute light across the display area while minimizing total internal reflection losses, maintaining high light use efficiency.
Solution Approach 2:
The patent introduces diffusion in multiple spatial dimensions: the first diffusion portion scatters light primarily in the crossing direction (X-axis), the second diffusion portion with inclined lenses diffuses light in the arrangement direction (Y-axis), and the third diffusion portion provides additional scattering. This multi-dimensional light distribution achieves comprehensive luminance uniformity without excessive diffusion that would cause energy loss.
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 allows for reduced luminance unevenness even with fewer light sources by diffusing light uniformly across the display area, maintaining high light use efficiency and suppressing hot spots.
Implementation Method 1
a first light diffusion portion included in the first section and adding a diffusion action to light rays travelling from the light sources toward the first section to be refracted and travel in a crossing direction crossing the arrangement direction
Implementation Method 2
a second light diffusion portion included in the second section and adding a diffusion action to light rays travelling from the second light entering surface toward the second section along a normal direction of the second light exit surface to be refracted and travel in the arrangement direction seen from the normal direction of the second light exit surface
Data Source
AI summary
A lighting device includes light sources arranged in an arrangement direction, a first light guide plate, and a second light guide plate on the first light guide plate. The first light guide plate includes a first light entering surface, a first light exit surface, and a first light diffusion portion adding a diffusion action to light to be refracted and travel in a crossing direction crossing the arrangement direction. The second light guide plate includes a second light entering surface, a second light exit surface, and a second light diffusion portion adding a diffusion action to light to be refracted and travel in the arrangement direction seen from the normal direction of the second light exit surface. The second light diffusion portion includes first lenses that include ridgelines extending in the crossing direction and inclined portions inclined at an angle from 35° to 55° inclusive relative to the normal direction.