Local-Dimming Planar Backlight Layout for Uniform Contrast
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Solution Overview
Problem
In planar illumination devices supporting local dimming, the inclination of the liquid crystal panel to prevent sunlight ingress causes reduced contrast and luminance uniformity due to differences in optical distance between the field lens and the liquid crystal panel.
Innovation Solution
A planar illumination device with a condenser lens and a field lens configuration, where the field lens is disposed orthogonal to the substrate and close to the liquid crystal panel, maintaining a uniform optical distance and spreading light outward to improve contrast and luminance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the liquid crystal panel is disposed inclined to prevent sunlight ingress, then heat and stray light problems are reduced, but contrast and luminance uniformity are reduced due to difference in optical distance
Solution Approach 1:
The patent divides the illumination device into multiple independently controllable light source regions (local dimming zones). By segmenting the light sources into zones that can be individually controlled, the system can compensate for the optical distance differences caused by the inclined liquid crystal panel arrangement, thereby maintaining luminance uniformity while preserving the anti-sunlight ingress benefit of the inclined configuration.
Solution Approach 2:
The patent applies local quality control through local dimming, where different regions of the light source array can have different illumination characteristics. This allows the system to adjust the light output in specific zones to compensate for the varying optical paths introduced by the inclined liquid crystal panel, ensuring uniform luminance distribution across the display area while maintaining the protective inclined arrangement against sunlight.
2Object-affected harmful factors
If the liquid crystal panel is disposed inclined, then sunlight reflection is improved, but contrast ratio between different areas is reduced
Solution Approach 1:
By segmenting the light source into multiple independently controllable zones, the system can adjust the intensity of light in each zone to compensate for the contrast reduction caused by the inclined liquid crystal panel. This segmentation enables precise local control of light distribution, maintaining high contrast ratios while preserving the anti-stray light benefits of the inclined configuration.
Solution Approach 2:
The local dimming capability allows different regions to have different light emission characteristics, enabling the system to maintain uniform contrast across the display area despite the inclined panel arrangement. Each local zone can be independently optimized to compensate for optical path differences, preserving both the stray light rejection and the contrast ratio.
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 suppresses the generation of light going out of zone areas, enhancing contrast and luminance uniformity while maintaining light efficiency.
Implementation Method 1
a condenser lens disposed at an exit side of the light sources in parallel with the substrate and configured to condense light exiting from the light sources
Implementation Method 2
a field lens disposed at an exit side of the condenser lens, disposed inclined in at least one direction orthogonal to a plane parallel to the substrate, configured to spread light incident from the condenser lens outward
Data Source
AI summary
A planar illumination device according to an embodiment includes a plurality of light sources, a condenser lens, and a field lens. The plurality of light sources are disposed two-dimensionally on a substrate and light emission of the plurality of light sources is individually controlled. The condenser lens is disposed at an exit side of the light sources in parallel with the substrate and configured to condense light exiting from the light sources. The field lens is disposed at an exit side of the condenser lens, disposed inclined in at least one direction orthogonal to a plane parallel to the substrate, configured to spread light incident from the condenser lens outward, and disposed along a liquid crystal panel attached externally.