Optical Element Reducing Light Etendue via Plasmon Conversion
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Solution Overview
Problem
Existing LED projector technologies face challenges in reducing light etendue without dependence on the etendue of the light-emitting element, leading to inefficiencies in light output and increased luminance requirements.
Innovation Solution
An optical element comprising a light guide body, a carrier generation layer, a plasmon excitation layer with a higher plasma frequency than the emitted light, and an exit layer that converts surface plasmons into light with a predetermined exit angle, sandwiched between dielectric layers to control the effective dielectric constant and enhance directionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are arranged on a plane to increase luminous flux, then the projected luminance is improved, but the light-emitting area increases causing etendue to increase
Solution Approach 1:
The patent introduces an optical element as an intermediary between the LED light source and the projection optical system. This optical element converts the wide-angle light from multiple LEDs into narrow-angle beam, effectively decoupling the relationship between light-emitting area and output etendue. The optical element acts as a mediator that transforms the light characteristics without requiring the LEDs themselves to be compact.
Solution Approach 2:
The patent changes the emission angle parameter of the light by using an optical element with specific refractive index and geometry. By controlling the refraction parameters, the optical element transforms the wide-angle emission from multiple LEDs into a narrow-angle beam, thereby reducing the output etendue while maintaining the total luminous flux from multiple LEDs.
2Loss of energy
If the etendue of light from the optical element is reduced to prevent light loss, then light efficiency is improved, but the light directionality and emission angle control become more difficult
Solution Approach 1:
The patent uses an optical element with specifically designed refractive index and geometry to control the emission angle. By adjusting these parameters, the optical element achieves both narrow emission angle (for low etendue) and proper light directionality (for efficient coupling to projection lens), resolving the contradiction between energy efficiency and operational control.
Solution Approach 2:
Instead of using complex mechanical structures (such as precise positioning of multiple LEDs or mechanical angle control mechanisms), the patent substitutes an optical solution based on refraction and total internal reflection. This optical approach achieves angle control and etendue reduction more simply and reliably.
3Illumination intensity
If optical axis matching members are used to synthesize light from multiple LEDs, then light synthesis is improved, but the etendue of the system remains dependent on the LED etendue
Solution Approach 1:
The patent introduces a second optical element as an intermediary that receives light from the LED array and projection optical system. This optical element converts the wide-angle light into narrow-angle beam, effectively decoupling the system etendue from the LED etendue. The optical element acts as a mediator that transforms the light characteristics regardless of the original LED emission properties.
Solution Approach 2:
The patent adds an optical transformation dimension by introducing an optical element that operates in the angular space dimension. This optical element maps the wide-angle emission spectrum to a narrow-angle output spectrum, creating a new dimensional transformation that overrides the original LED etendue constraints.
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 configuration reduces light etendue independently of the light-emitting element, improving light directionality and reducing losses, thereby enhancing the efficiency and luminance of the projected image.
Implementation Method 1
a carrier generation layer formed in the light guide body, in which carriers are generated by the light from the light guide body
Implementation Method 2
a plasmon excitation layer stacked above the carrier generation layer, which has a plasma frequency higher than the frequency of light generated when the carrier generation layer is excited by the light from the light-emitting element
Implementation Method 3
an exit layer stacked above the plasmon excitation layer, which converts light incident from the plasmon excitation layer into light having a predetermined exit angle to output the light
Implementation Method 4
The effective dielectric constant of the incident side portion of the plasmon excitation layer including the entire structure stacked above the light guide body side is higher than that of the exit side portion of the plasmon excitation layer including the entire structure stacked above the exit layer side and a medium in contact with the exit layer
Data Source
AI summary
Disclosed is an optical element that includes: carrier generation layer (16) in which carriers are generated by light from light guide body (12) into which light from a light-emitting element enters; plasmon excitation layer (17) that has a plasma frequency higher than the frequency of light generated when carrier generation layer (16) is excited by light from the light-emitting element; and wave vector conversion layer (18) that converts surface plasmon generated by plasmon excitation layer (17) light having a predetermined exit angle to output the light. Plasmon excitation layer (17) is sandwiched between two layers having dielectric properties. The effective dielectric constant of the incident side portion of plasmon excitation layer (17) including an entire structure stacked above light guide body (12) side is higher than that of the exit side portion of plasmon excitation layer (17) including the entire structure stacked above wave vector conversion layer (18) side and the medium in contact with wave vector conversion layer (18).