Dichroic Coating Porous Structure for Projector Light Transmission
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Solution Overview
Problem
Dichroic shift in color splitting-converging prisms of digital projectors leads to reduced light transmission efficiency and increased heating, as existing solutions like dichroic mirrors and multi-layer thin film filters do not adequately address the issue of light transmission at large angles of incidence.
Innovation Solution
The use of novel multi-layer dichroic coatings with alternating layers of high and low refractive index materials, such as TiO2 and SiO2, designed to reduce dichroic shift and enhance light transmission by optimizing the thickness and refractive index matching, resulting in improved light throughput and reduced heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional dichroic coatings are used in color splitting-converging prisms, then color separation is achieved, but light transmission efficiency decreases due to dichroic shift at large angles of incidence
Solution Approach 1:
The patent changes the physical parameters of the dichroic coating by introducing a porous structure with controlled porosity (30-70%) and specific pore size (50-500 nm). This structural parameter change allows the coating to maintain its wavelength-selective optical properties while reducing the dichroic shift effect at large angles of incidence, thereby improving light transmission efficiency
Solution Approach 2:
The patent creates a composite material by combining a porous dielectric layer with a metallic layer (such as aluminum or silver). This composite structure leverages the wavelength-selective properties of the porous dielectric and the reflective properties of the metal to achieve both color separation and reduced dichroic shift, resolving the contradiction between color separation and light transmission efficiency
2Productivity
If dichroic coatings are designed for large angles of incidence to match DMD requirements, then light throughput is maximized, but dichroic shift increases causing color accuracy degradation
Solution Approach 1:
The patent modifies the optical parameters of the dichroic coating by creating a porous structure that changes the effective refractive index and reduces the angle-dependent shift in reflectance wavelength. This allows the coating to maintain accurate color separation across a broader range of incidence angles while still supporting high light throughput required for DMD operation
3Illumination intensity
If conventional multi-layer thin film filters are used, then color separation is achieved, but heating of the prism increases due to light absorption
Solution Approach 1:
The patent uses a composite structure of porous dielectric layer and metallic layer to achieve color separation with reduced light absorption. The porous dielectric provides wavelength-selective reflection with minimal absorption, while the metallic layer enhances reflectance. This composite approach reduces the total light absorption in the prism compared to conventional multi-layer thin film filters, thereby reducing prism heating
Solution Approach 2:
The porous dielectric layer provides efficient wavelength-selective reflection through its porous structure with controlled porosity and pore size. This porous structure reduces material density and light absorption while maintaining optical functionality, thereby reducing heat generation in the prism compared to solid multi-layer thin film filters
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 novel coatings achieve a 25% improvement in light output by minimizing dichroic shift, increasing light transmission, and optimizing color separation, with enhanced reflectance in the blue and red spectra while reducing reflection in the green spectrum.
Implementation Method 1
The dichroic coatings separate the incident light into blue, green, and red spectra
Implementation Method 2
multi-layer dichroic coatings with alternating layers of high and low refractive index materials, such as TiO2 and SiO2
Implementation Method 3
multi-layer dichroic coatings with alternating layers of high and low refractive index materials
Data Source
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AI summary
A projector incorporating a prism and a plurality of light valves for modulating light that passes through the prism, wherein the color splitting-converging prism includes a dichroic coating having multiple layers of high and low index of refraction and 1/4 wavelenth thickness at each desired angle of incidence for reducing dichoric shift and thereby minimizing light loss.