Optical Element Plasmon Coupling Reduces Etendue
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Solution Overview
Problem
Existing LED projectors face challenges in reducing light loss due to etendue limitations, where the product of the light source's surface area and radiation angle exceeds the acceptance angle of the light valve, leading to inefficient light utilization and increased etendue of the light source unit.
Innovation Solution
An optical element with a carrier-generating layer, a plasmon-excitation layer having a higher plasma frequency than the incident light, and an emission layer, sandwiched between dielectric layers, is used to reduce the etendue of emitted light by controlling the dielectric constants and optimizing plasmon coupling, allowing for improved light directivity and reduced light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are used to increase luminous flux, then projected luminance is improved, but etendue of the light source increases
Solution Approach 1:
The patent changes the optical parameters of the system by introducing an optical element that modifies the radiation angle and etendue of light from multiple LEDs. By controlling the etendue transformation through the optical element, the system achieves high luminance while maintaining compatible etendue with the light valve acceptance angle.
Solution Approach 2:
The optical element functions as a composite optical system that combines multiple LEDs with different radiation characteristics into a unified light source with controlled etendue. This composite approach allows synthesis of high luminous flux while managing the overall etendue to match the light valve requirements.
2Illumination intensity
If light source surface area is increased to provide sufficient luminous flux, then projected luminance is improved, but etendue increases beyond light valve acceptance
Solution Approach 1:
The optical element transforms the spatial and angular parameters of light from a larger light source area into a configuration that matches the light valve's acceptance angle. This parameter transformation allows a physically larger light source to effectively present a smaller etendue to the light valve.
3Illumination intensity
If radiation angle of light source is increased to provide sufficient luminous flux, then projected luminance is improved, but etendue increases beyond light valve acceptance
Solution Approach 1:
The optical element modifies the radiation angle parameter of the light source, transforming wide-angle light from multiple LEDs into a narrower beam that matches the light valve's acceptance angle. This parameter change resolves the contradiction between needing high luminous flux (requiring wide radiation) and matching etendue (requiring narrow radiation).
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 effectively reduces the etendue of emitted light without relying on the etendue of light-emitting elements, enhancing light utilization efficiency and luminance in LED projectors.
Implementation Method 1
a carrier-generating layer that is laminated on the incident surface and in which carriers are generated by light
Implementation Method 2
a plasmon-excitation layer that is laminated on the carrier-generating layer and that has higher plasma frequency than the frequency of light that is generated when the carrier-generating layer is excited by light
Data Source
AI summary
An optical element that can reduce the etendue of emitted light emitted from the optical element without having depend on the etendue of light-emitting elements is provided with a plasmon-excitation layer that is interposed between two layers having dielectric properties wherein, taking the plasmon-excitation layer as a border, the effective dielectric constant of the emission-side portion that is the emission layer side is higher than the effective dielectric constant of the incident-side portion that is the side of a carrier-generating layer, and the dielectric constant between the plasmon-excitation layer and the carrier-generating layer is higher than the dielectric constant between the carrier-generating layer and the light-incident surface.