Integrated Filtered Thermal Emitter for Directional Light Extraction
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Solution Overview
Problem
Existing thermal emitters face challenges in efficiently collecting and transmitting broadband visible and infrared radiation at high temperatures due to limitations in materials that can withstand high temperatures, low emissivity, and angular dependence of optical filters, leading to losses and inefficiencies in light collection and transmission.
Innovation Solution
A thermal emitter device with an integrated filter and a transmissive optical element, such as a planoconvex lens, placed close to the emitting surface to enhance light transmission by reflecting and reabsorbing light, and using a mirror to control light directionality, while maintaining compactness and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a refractory material is used for the thermal emitter, then the emitter can withstand high temperatures, but the emissivity is low
Solution Approach 1:
The patent uses a composite structure combining a refractory material emitter with a transmissive optical element. The refractory material provides high temperature resistance while the optical element (with refractive index between 1.4 and 1.7) enhances light transmission, effectively compensating for the low emissivity of the refractory material.
Solution Approach 2:
The transmissive optical element acts as an intermediary between the refractory emitter and the external environment. It receives the broadband radiation from the refractory material and selectively transmits it, improving the overall light output without requiring the emitter itself to have high emissivity.
2Productivity
If a parabolic reflector is used to collect light, then light collection is enhanced, but shadowing occurs and the device size increases
Solution Approach 1:
The patent extracts the light collection function from a large parabolic reflector and concentrates it into a compact transmissive optical element. This element captures light at high angles (greater than 60° or lower than −60°) without requiring the large volume of a parabolic reflector, eliminating shadowing issues.
Solution Approach 2:
The transmissive optical element handles light from all angles (including high angles greater than 60° or lower than −60°) that would traditionally be lost, effectively adding a dimensional capability to light collection without increasing the device footprint.
3Measurement precision
If an optical filter is added to control wavelength, then spectral selectivity is improved, but angular dependence causes losses
Solution Approach 1:
The patent positions the optical filter at a specific distance from the emitter (between 0.1 times and 1.0 times the emitter diameter) and orients it perpendicular to the emitter surface. This geometric configuration ensures that light reaches the filter at near-normal incidence, minimizing angular dependence losses while maintaining spectral selectivity.
4Loss of energy
If the emitter is placed in an evacuated space, then thermal losses are minimized, but the housing complexity increases
Solution Approach 1:
The patent protects the refractory emitter from atmospheric reactions by placing it in an evacuated space or filling the housing with an inert gas atmosphere. This creates a protective environment that prevents oxidation and chemical degradation while allowing thermal radiation to pass through the transparent housing walls.
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 significantly improves light transmission and efficiency, allowing for higher lifetime and directional emission, reducing the need for external collimating optics and enabling smaller detector sizes.
Implementation Method 1
Thermal emitters rely on the emission of electromagnetic radiation from hot bodies
Implementation Method 2
A thermal emitter device with an integrated filter and a transmissive optical element, such as a planoconvex lens, placed close to the emitting surface to enhance light transmission by reflecting and reabsorbing light
Implementation Method 3
an optical filter on the curved surface
Data Source
AI summary
A light emitter module includes a refractory membrane arranged to be heated to a thermal emission temperature such that an emitting surface of the membrane emits radiation in the IR and/or visible spectrum. The radiation is collimated by transmissive optical element adjacent to the emitting surface with a curved exit surface on which an optical filter is deposited. The transmissive optical element may be a planoconvex lens. The disclosure relates also to compound sources with several thermal sources facing an array of micro-lenses with a common plane entry surface on the backside and a plurality of convex surfaces on the forward side, each covered by an optical filter.