LCD Backlight Light Recycling with Reflective Polarizer
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Solution Overview
Problem
Traditional LCD backlight systems face inefficiencies due to high absorption of polarized light by polarizers and require high LED density and thick displays for uniformity, which are undesirable in practical applications.
Innovation Solution
The implementation of a reflective polarizer and fractional wave-plates to recycle unused polarized light, allowing for increased spacing between LEDs and reducing the thickness of the display while maintaining uniformity and efficiency through selective polarization rotation and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reflective polarizer is used to recycle unused polarization of light, then light recycling efficiency is improved, but device complexity increases
Solution Approach 1:
The reflective polarizer recovers unused polarized light that would otherwise be wasted, reflecting it back through the wave plate to convert it into usable light. This recovers energy that would have been discarded, directly improving light recycling efficiency
Solution Approach 2:
The wave plate acts as an intermediary component between the light source and the reflective polarizer, rotating the polarization of reflected light to enable its reuse. This mediator facilitates the energy recovery process while managing the added complexity
2Stability of the object's composition
If fractional wave plates are used for selective polarization rotation, then uniformity is improved, but device complexity increases
Solution Approach 1:
Fractional wave plates are placed selectively in spaces between light sources rather than uniformly across the entire system. This localized approach achieves the needed polarization control and uniformity improvement while minimizing the overall complexity increase
Solution Approach 2:
The wave plates are designed with specific fractional retardation values to rotate polarization by precise amounts. By changing the optical parameter (retardation) of the wave plates, the system achieves improved uniformity through controlled polarization rotation
3Quantity of substance
If LED spacing is increased, then manufacturing cost is reduced, but uniformity deteriorates
Solution Approach 1:
The reflective polarizer creates an optical feedback path that redirects unused light back through the wave plate and toward the display. This feedback mechanism compensates for the reduced light output from fewer, more spaced-out LEDs, maintaining uniformity while reducing LED quantity
Solution Approach 2:
The system creates a continuous optical path where light that would have been wasted is continuously recycled back into the system. This continuous action of light recycling maintains uniform illumination even with increased LED spacing
4Ease of manufacture
If display thickness is reduced, then ease of manufacture is improved, but uniformity deteriorates
Solution Approach 1:
The solution moves from addressing uniformity through spatial arrangement (LED density) to addressing it through optical path manipulation (polarization recycling). This dimensional shift in the problem-solving approach enables thin design while maintaining 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
This approach enhances light recycling, increasing the efficiency and uniformity of the LCD display backlight system by converting unused polarized light into usable light, thereby reducing the number of LEDs needed and minimizing display thickness.
Implementation Method 1
The reflective polarizer transmits light having a useable polarization and reflects back unused polarization of light onto the reflective surface
Implementation Method 2
A portion of the unused polarization of light reflected from the reflective polarizer passes through a fractional wave plate. The reflective surface reflects the portion of the unused polarization of light through the fractional wave plate such that the polarization of the unused polarization of light is changed to useable polarization
Implementation Method 3
The reflective surface reflects the portion of the unused polarization of light through the fractional wave plate such that the polarization of the unused polarization of light is changed to useable polarization
Data Source
AI summary
A LCD display backlight system with improved color mixing and efficiency comprises a reflective surface, a plurality of light sources mounted on the reflective surface, a plurality of fractional wave plates and a reflective polarizer. The plurality of fractional wave plates is mounted on spaces between the plurality of light sources on the reflective surface. The reflective polarizer transmits light having a useable polarization and reflects back unused polarization of light onto the reflective surface. A portion of the unused polarization of light reflected from the reflective polarizer passes through a fractional wave plate. The reflective surface reflects the portion of the unused polarization of light through the fractional wave plate such that the polarization of the unused polarization of light is changed to useable polarization, thereby recycling the unused polarization of light into useful light.