Birefringent Microlens Light Guide for LCD Backlighting
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Solution Overview
Problem
Conventional backlighting systems for LCD displays are costly, inefficient, and consume excessive power due to the use of CCFLs and multiple layers of DBEF and BEF, which also fail to effectively control viewing angles and color mixing.
Innovation Solution
An integrated light guide with micro-groove structures filled with birefringent material on its front wall, utilizing total internal reflection and birefringent microlens structures to provide polarized light output with controlled angular distribution, eliminating the need for DBEF and BEF, and reducing the number of LEDs required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional CCFLs and multiple layers of DBEF and BEF are used for backlighting, then brightness enhancement and polarization recycling are achieved, but system cost increases and power consumption increases
Solution Approach 1:
The patent merges the functions of CCFLs, DBEF, and BEF into a single integrated LED-based light guide structure. The light guide plate incorporates micro-groove structures with birefringent materials that simultaneously perform light distribution, polarization, and brightness enhancement functions that were previously required separate components, thereby reducing power consumption while maintaining brightness.
Solution Approach 2:
The invention changes the light source from CCFL to LED and modifies the optical path through birefringent materials with specific refractive indices. By controlling the ordinary and extraordinary ray paths through parameter optimization of the birefringent material properties and groove geometries, the system achieves efficient light extraction with controlled angular distribution, reducing overall power requirements.
2Illumination intensity
If DBEF and BEF layers are added to enhance brightness and control angular distribution, then viewing angle control and brightness enhancement are improved, but device complexity increases
Solution Approach 1:
The patent combines multiple optical functions into the light guide plate itself. The micro-groove structures filled with birefringent materials integrate polarization recycling, angular light distribution control, and brightness enhancement into a single component, eliminating the need for separate DBEF and BEF layers and reducing overall device complexity.
Solution Approach 2:
The light guide plate with birefringent micro-groove structures performs multiple functions simultaneously: it acts as a light distribution element, polarization controller, and angular beam shaper. This multi-functional design replaces several specialized components with a single universal element that handles all optical manipulation tasks.
3Ease of manufacture
If aluminum sub-wavelength grating is used on the front wall for polarization recycling, then polarization function is achieved, but manufacturing difficulty increases due to nano-scale features
Solution Approach 1:
Instead of using sub-wavelength aluminum gratings requiring nano-scale precision, the invention uses micro-scale groove structures filled with birefringent materials. By changing from metallic sub-wavelength structures to dielectric micro-structures with controlled refractive indices, the manufacturing precision requirement is relaxed from nanometer to micrometer scale while maintaining polarization functionality.
Solution Approach 2:
The birefringent material acts as an intermediary between the light guide plate and the external environment. Rather than relying on direct interaction with nano-scale metallic gratings, the birefringent material mediates the optical interaction through its anisotropic refractive properties, achieving polarization control through more manufacturable micro-scale groove structures.
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 solution enhances brightness, reduces power consumption, and simplifies the backlight structure by controlling viewing angles and improving color mixing efficiency, while eliminating the need for costly components like CCFLs and additional BEF layers.
Implementation Method 1
The light extraction is based upon total internal reflection (TIR)
Implementation Method 2
micro-groove structures filled with birefringent (double refraction) material are provided on the front wall of the light guide for polarized light output
Data Source
AI summary
A backlighting apparatus for a flat panel LCD display includes an elongate light guide having a front wall through which travels polarized light in a direction toward the LCD display. An RGB LED set is positioned adjacent a first end wall of the light guide so that light enters the light guide from the first end wall. A retardation and reflection film covers respective external surfaces of the bottom wall and a second end wall. Microlenses are formed in the front wall along its extent and each microlens is filled with a birefringent material. Light emitted by the LED set travels through a collimated light coupling module and exits the light guide through the birefringent microlenses in polarized form toward the LCD display. The viewing angles and angular light distributions of the LCD display in vertical and horizontal directions are optimized for enhancing the brightness without involving DBEF and BEF.