RGB LED Illumination System Using Polarization Conversion for LCD Panels
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Solution Overview
Problem
Current projection systems using short arc lamps for LCD and LCoS technologies are bulky, expensive, and inefficient, with issues like UV and IR light emission reducing component lifespan and requiring additional cooling, while LED-based systems face challenges in coupling light to fiber bundles and waveguides due to aberration and aperture limitations, leading to low light efficiency and contrast.
Innovation Solution
An RGB LED illumination system with a polarization conversion and recovery system, utilizing tapered waveguides and non-polarizing dichroic combiners to efficiently convert and homogenize light, providing linearly polarized illumination for LCD or LCoS panels, which reduces optical losses and enhances brightness and color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If short arc gaseous white lamps are used for illumination, then high etendue efficiency is achieved, but the system becomes bulky, expensive, and generates harmful UV and IR light requiring additional cooling and filtration components
Solution Approach 1:
The patent extracts only the useful visible spectrum from the LED source while eliminating harmful UV and IR components through selective optical filtering and waveguide design. The LED illumination system with dichroic mirrors and waveguides separates and transmits only the desired wavelength ranges to the spatial light modulator, removing the need for complex cooling and filtration systems required by short arc lamps.
Solution Approach 2:
The patent changes the spectral parameters of the illumination source by using LED arrays with specific wavelength emissions (red, green, blue LEDs) that naturally produce only visible light without UV or IR components. This parameter change in the light source eliminates the need for additional cooling devices and UV filtration while maintaining high etendue efficiency.
2Volume of moving object
If LED arrays are coupled to fiber bundles and waveguides, then compact design is achieved, but light transmission efficiency decreases due to coupling and transmission loss
Solution Approach 1:
The patent introduces waveguides as intermediary components that efficiently couple LED light sources to the spatial light modulator. The waveguides with optimized geometry and refractive index matching serve as mediators between the LED arrays and the illumination optics, minimizing coupling losses and maintaining high light transmission efficiency while enabling compact system design.
Solution Approach 2:
The patent optimizes the geometric parameters of the waveguides (dimensions, refractive index, taper ratios) to maximize light coupling efficiency from LED arrays. By changing these physical parameters, the system achieves efficient light transmission through the waveguides while maintaining a compact form factor, resolving the contradiction between size and transmission loss.
3Illumination intensity
If fly's-eye lens arrays are used for light distribution, then uniform illumination is achieved, but the system becomes bulky and expensive to manufacture
Solution Approach 1:
The patent extracts the light homogenization function from the complex fly's-eye lens array and implements it through simpler waveguide-based optical paths. The waveguides with carefully designed internal reflection surfaces and geometry provide uniform light distribution to the spatial light modulator without requiring the bulky and expensive lens arrays, maintaining illumination uniformity while reducing system complexity.
4Duration of action of stationary object
If LEDs are used instead of short arc lamps, then operational lifetime is increased and UV/IR light is eliminated, but coupling efficiency to optical components decreases
Solution Approach 1:
The patent uses waveguides as intermediary components to bridge the coupling gap between LED arrays and optical systems. These waveguides with optimized refractive indices and geometric configurations serve as mediators that efficiently transfer LED light to the illumination optics, minimizing coupling losses and enabling the system to achieve both long operational lifetime and high coupling efficiency.
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 achieves high efficiency in light transmission and polarization, increasing luminous efficiency and operational life by eliminating UV and IR light, and providing uniform illumination with a compact and cost-effective design.
Implementation Method 1
a light integrator to receive light beams from the red, green and blue LEDs and to provide a homogenized light output
Implementation Method 2
a polarization conversion and recovery system to convert the light beams into linearly polarized light
Implementation Method 3
The light emitted from the light source must be converted into polarized light for illuminating an LCD or LCoS spatial light modulator
Implementation Method 4
non-polarizing dichroic combiners to efficiently convert and homogenize light
Implementation Method 5
LCD and LCoS devices depend on either the polarization rotation effect or the birefringent effect of the liquid crystal to generate light
Implementation Method 6
LCD and LCoS devices depend on either the polarization rotation effect or the birefringent effect of the liquid crystal
Data Source
AI summary
A polarized light illumination system includes a light emitting diode (LED) (601, 602, 603) for providing a source of light that is directed to a non-polarizing dichroic combiner (607) for combining light from the LEDs into a single light source. A power beam splitter (PBS) (608) is then used for splitting the single light source into polarized light components and an output waveguide (611) operates to provide a source of uniformly illuminated light. A condenser lens (612) then projects the uniformly illuminated light to a microdisplay panel (613) for use with a television receiver or other type of display monitor.