Structured Reflector Light Recycling Backlight
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Solution Overview
Problem
Current light recycling systems for liquid crystal displays face challenges in achieving uniform illumination and efficient light recycling due to limitations in the design of reflective polarizers and structured reflectors, which affect the emission and redirection of light angles.
Innovation Solution
A recycling backlight system comprising a reflective polarizer, a structured reflector, and a lightguide, where the structured reflector is configured to retroreflect and redirect light within specific angles relative to the polarizer's normal axis, optimizing light emission and redirection to enhance luminance and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional reflective polarizer and structured reflector are used in a recycling backlight system, then the basic light recycling function is achieved, but the off-axis luminance and light recycling efficiency are insufficient
Solution Approach 1:
The structured reflector is divided into multiple zones with different geometries (e.g., first structured region with one orientation, second structured region with another orientation) to handle different light angles separately. This segmentation allows each zone to optimize for specific angular ranges, improving overall light recycling efficiency while maintaining uniform off-axis luminance distribution.
Solution Approach 2:
Different regions of the structured reflector are given different local optical properties through varying prism geometries, orientations, or depths. This local quality variation enables the reflector to redirect light from different incident angles to appropriate exit angles, simultaneously improving light recycling efficiency for axial light and maintaining off-axis luminance uniformity.
2Illumination intensity
If the structured reflector redirects light to within 30 degrees of the normal axis, then axial luminance is improved, but the complexity of the reflector design increases
Solution Approach 1:
The structured reflector design incorporates dynamic angular redirection capabilities where the prism geometries are specifically engineered to redirect incident light from various angles into a concentrated output range within 30 degrees of the normal axis. This dynamic angular control enhances axial luminance without requiring additional optical components, thereby managing design complexity through integrated geometric optimization.
3Adaptability or versatility
If the lightguide extracts light over a wide range of emission angles, then the viewing angle is improved, but the uniformity of illumination decreases
Solution Approach 1:
The structured reflector employs asymmetric prism geometries and orientations in different zones to compensate for the wide emission angle range. By creating asymmetric redirection patterns, the system maintains illumination uniformity across the display while still supporting broad viewing angles through the lightguide's inherent wide-angle extraction capability.
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 system significantly improves off-axis luminance and axial luminance, increasing light recycling efficiency and uniformity by redirecting light within 30 degrees of the normal axis, thereby enhancing the display's illumination performance.
Implementation Method 1
The structured reflector is configured to retroreflect light at a second range of angles φ measured with respect to a normal axis of the reflective polarizer
Implementation Method 2
The structured reflector is also configured to redirect light from a third range of angles ψ, measured with respect to the normal axis of the reflective polarizer, to within 30 degrees of the normal axis of the reflective polarizer
Implementation Method 3
Displays such as liquid crystal displays that rely on polarization manipulation to form images may use efficient light recycling cavities in order to convert light of an unusable polarization (e.g. light that would be otherwise absorbed by the liquid crystal module) into light of a usable polarization
Implementation Method 4
The lightguide has a first range of emission angles θ for light coupled into the input surface and extracted from the lightguide, the range of emission angles θ measured with respect to a normal axis of the reflective polarizer
Data Source
AI summary
Recycling backlights are described. More specifically, recycling backlights including structured reflectors are described. The structured reflector redirects light at least for angles emitted from a lightguide and retroreflects other light, the retroreflected light having incidence angles not emitted by the lightguide.