Compact Multispectral Refractive Optical System
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Solution Overview
Problem
Existing multispectral systems for detecting short wave infrared (SWIR) and long wave infrared (LWIR) wavebands require separate optical trains, making them bulky and unsuitable for compact applications like helmet-mounted goggle systems due to the need for large fields of view and fast f-numbers.
Innovation Solution
A compact multispectral wide angle refractive optical system using a shared optical train with three elements, where the first and third elements are aspherical and the second element is made of diamond, allowing both SWIR and LWIR wavebands to be focused onto a common focal plane, utilizing specific material pairings like GaAs/IR Chalcogenide glass or ZnSe/GaAs to achieve chromatic correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate optical trains are used for SWIR and LWIR detection, then chromatic correction for each waveband can be achieved, but the system mass and size increase making it unsuitable for helmet-mounted applications
Solution Approach 1:
The patent merges SWIR and LWIR optical paths into a single shared optical train, eliminating the need for separate optical systems. The optical train includes lenses and optical elements that handle both wavebands simultaneously, reducing overall system mass and size while maintaining chromatic correction through carefully selected material pairings with complementary dispersion characteristics.
Solution Approach 2:
The patent employs composite material pairings (such as GaAs with IR Chalcogenide glass, or ZnSe with GaAs) where each material has specific dispersion characteristics. By combining materials with complementary dispersion properties, the system achieves achromatic correction across both SWIR and LWIR wavebands within a single optical train, resolving the contradiction between compact size and chromatic correction precision.
2Measurement precision
If a purely reflective design is used to achieve achromatic correction, then chromatic correction is achieved, but the system cannot satisfy large field of view and fast f-number requirements for compact applications
Solution Approach 1:
The patent changes the fundamental optical parameters by transitioning from a purely reflective design to a refractive design using material pairings with complementary dispersion. This allows the system to achieve achromatic correction while simultaneously satisfying the requirements for large field of view (typically around 40° or greater) and fast f-numbers (typically around f/1.2 or less), which are critical for helmet-mounted goggle systems.
3Volume of moving object
If a shared optical train is used for both wavebands, then system compactness is improved, but achieving chromatic correction across non-contiguous wavebands becomes more difficult
Solution Approach 1:
The patent uses composite material pairings where each material in the pair has specific dispersion characteristics that complement the other. Examples include GaAs paired with IR Chalcogenide glass, or ZnSe paired with GaAs. These material combinations enable chromatic correction across the non-contiguous SWIR and LWIR wavebands within a compact shared optical train, as the complementary dispersion properties of the material pairs allow simultaneous focusing of both wavebands onto a common focal plane.
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 design enables a compact, well-corrected, fast, and wide-angle system that reduces the f-number while maintaining a small form factor, enhancing detection range and reducing Noise Equivalent Temperature Difference (NETD) while being suitable for harsh environments.
Implementation Method 1
A first element formed of a first material receives incident radiation. A second element formed of diamond material receives radiation from the egress end of the first element. A third element formed of a third material receives radiation from the egress end of the second element.
Implementation Method 2
The first element ingress surface is aspherical; the first element egress surface is aspherical; the third element ingress surface is aspherical; and the third element egress surface is aspherical.
Data Source
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AI summary
A multispectral wide angle refractive optical device for focusing light from a first waveband and a non-overlapping second waveband is presented. A first element formed of a first material receives incident radiation. A second element formed of diamond material receives radiation from the egress end of the first element. A third element formed of a third material receives radiation from the egress end of the second element. An optical train through the three elements onto a common focal plane is shared by the first waveband and a second waveband.