Light Guide Plate Microstructures for Local Dimming
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Solution Overview
Problem
Conventional edge light backlight devices using LEDs for LCDs suffer from incomplete and uneven light distribution due to the point source characteristics of LEDs, leading to halation and blurred motion images, as light from bright sections leaks to dark sections without proper concentration.
Innovation Solution
A light guide plate with microstructures, such as lenticular or Fresnel lenses, is introduced, featuring a specific R/T ratio and height range, which concentrates light and prevents emission at large refractive angles, combined with a reflective plate and diffuser to enhance local dimming effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional light guide plate without microstructures is used, then manufacturing is simple, but light distribution is uneven and local dimming performance is poor
Solution Approach 1:
The light guide plate incorporates microstructures (lenticular or Fresnel lenses) at specific locations to concentrate light in particular directions. These localized optical elements create non-uniform light distribution patterns that prevent light leakage from bright to dark sections, thereby improving local dimming performance without making the entire structure complex
Solution Approach 2:
The patent employs curved surface microstructures (lenticular lenses with spherical curvature or Fresnel lenses with stepped curvature) on the light guide plate. These curved surfaces refract and concentrate light in specific directions, improving light distribution uniformity and local dimming effect while maintaining a relatively simple overall plate structure
2Use of energy by moving object
If LEDs are used as light source, then energy consumption is low and switching speed is rapid, but light is not directional and enters light guide plate unevenly
Solution Approach 1:
The microstructures on the light guide plate act as intermediary optical elements between the LED point sources and the display screen. These microstructures refract and concentrate the non-directional LED light into more directional beams, improving light entry uniformity while preserving the energy efficiency and rapid switching characteristics of LEDs
3Illumination intensity
If no microstructures are formed on light guide plate, then manufacturing precision requirements are low, but light concentration capability is insufficient and halation occurs
Solution Approach 1:
The patent uses standardized curved surface geometries (spherical lenticular lenses or stepped Fresnel lenses) that can be manufactured using conventional molding techniques. These regular curved patterns achieve effective light concentration and prevent halation while maintaining reasonable manufacturing precision requirements through established fabrication processes
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 achieves superior local dimming performance by concentrating light and reducing leakage between sections, resulting in improved contrast ratio and reduced halation, effectively addressing the issues of light distribution and image quality.
Implementation Method 1
Each of the microstructures includes a curved surface with a radius of curvature (R)... light from the LEDs 8 near the portion A is likely to leak to the dark portion B
Data Source
AI summary
An edge light backlight device includes a light guide plate having a base portion and microstructures, LEDs, and a reflective plate. The base portion has a light emitting side, a rear side, and a light incident side. The microstructures are formed on one of the light emitting side and the rear side and each of which extends from the light incident side in a longitudinal direction. Each of the microstructures includes a curved surface with a radius of curvature (R). The light guide plate has a thickness (T). R/T ratio ranges from 0.04 to 0.15 and each of the microstructures has a height ranging from 20 μm to 300 μm so that the light guide plate has a performance of local lighting ranging from 1% to 40%.