Backlight Uniform Illumination Using Partial Reflector and Polarizer
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Solution Overview
Problem
Conventional backlight systems for LCDs face challenges in achieving uniform, efficient, and spatially consistent illumination, often requiring additional optics and thickness to meet brightness and uniformity specifications.
Innovation Solution
A backlight system comprising an array of discrete light sources emitting unpolarized blue light, a multilayer polymeric partial reflector with high reflectance for blue wavelengths, and a reflective polarizer, along with additional optical elements like diffusers and prism films, to enhance light spreading and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional backlight systems use additional optics to achieve uniform illumination, then illumination uniformity is improved, but device thickness and complexity increase
Solution Approach 1:
The patent combines multiple optical functions into a single integrated optical element. The optical element integrates light spreading, uniformization, and polarization control in one component, eliminating the need for separate conventional optical elements and reducing overall backlight thickness while maintaining uniform illumination.
Solution Approach 2:
The patent employs composite optical structures with multiple layers having different optical properties. The optical element consists of multiple layers including polarization-selective layers and light-spreading layers with specific refractive indices and thicknesses, creating a composite structure that achieves uniform illumination in a compact form factor.
2Illumination intensity
If conventional backlight systems use additional optics to achieve uniform illumination, then illumination uniformity is improved, but the number of components increases
Solution Approach 1:
The patent merges multiple optical functions into a single integrated optical element that performs light spreading, uniformization, and polarization control simultaneously, reducing the number of discrete components while achieving the same uniform illumination effect.
Solution Approach 2:
The optical element is designed to perform multiple functions: it acts as a light spreader, a uniformization element, and a polarization controller all in one component, making it a universal optical solution that replaces multiple conventional separate components.
3Productivity
If discrete light sources are used to enable dynamic brightness control, then productivity and control flexibility are improved, but achieving uniform illumination becomes more difficult
Solution Approach 1:
The patent segments the backlight into discrete controllable light source regions while using an integrated optical element to uniformly distribute light from all segments. This allows independent control of brightness in different regions while maintaining overall spatial uniformity through the optical element's light-spreading properties.
Solution Approach 2:
The integrated optical element acts as an intermediary between the discrete light sources and the display panel. It receives light from multiple discrete sources with different intensities and redistributes it uniformly across the display area, enabling dynamic brightness control while maintaining spatial uniformity.
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 provides improved spatial and angular uniformity of light distribution, allowing for dynamic brightness control and reduced thickness of backlight components, enhancing user visual experience and optical efficiency.
Implementation Method 1
a multilayer polymeric partial reflector with high reflectance for blue wavelengths
Implementation Method 2
a reflective polarizer... reflects at least 60% of the light having the first polarization state and transmits at least 60% of the light having the second polarization state
Data Source
AI summary
A backlight for providing uniform illumination to a display panel includes a plurality of discrete light sources. A multilayer polymeric partial reflector is disposed on the plurality of discrete light sources. For substantially normally incident light the partial reflector includes a reflection band includes a blue wavelength, a reflectance greater than about 80% at the blue wavelength, a left band edge between about 370 nm to about 420 nm, a right band edge between about 500 nm and 600 nm, and an average transmission between about 20% to about 80% for visible wavelengths greater than the right band edge. A reflective polarizer is disposed on the partial reflector. For substantially normally incident light having the blue wavelength, the reflective polarizer reflects at least 60% of the light having the first polarization state and transmits at least 60% of the light having the second polarization state.