Cross-band Apochromatic Correction in Multi-element Infrared Optical Systems
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Solution Overview
Problem
Designing multi-band optical systems that operate across disparate infrared bands is challenging due to the limited number of materials available for refractive optical elements, which leads to difficulties in determining the best combinations of materials to minimize chromatic aberrations and achieve apochromatic correction.
Innovation Solution
A method and system for cross-band apochromatic correction in multi-element optical systems, which involves selecting design wavelengths, determining suitable optical materials, generating solutions based on mean squared difference values, and ranking them using a merit function to minimize optical power variations across multiple infrared bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refractive optical elements are used in multi-band optical systems, then chromatic aberrations occur due to lens dispersion, but using reflecting components alone limits the available field of view and magnification options
Solution Approach 1:
The patent uses a dichroic beamsplitter as an intermediary component to separate different wavelength bands (SWIR and LWIR) and direct them to different optical paths. This allows the system to use refractive optics for each band without the different wavelengths mixing and creating chromatic aberrations, while still achieving multi-band functionality.
Solution Approach 2:
The optical system is segmented into separate optical paths for different wavelength bands. Each band (SWIR, MWIR, LWIR) has its own dedicated refractive optical elements optimized for that specific band, eliminating cross-band chromatic aberrations while maintaining optimal performance for each wavelength range.
2Reliability
If multiple materials are combined to correct chromatic aberrations across disparate infrared bands, then apochromatic correction can be achieved, but the difficulty in determining the best material combinations increases
Solution Approach 1:
The patent systematically varies and optimizes key parameters including the selection of specific infrared-transmissive materials (Ge, Si, ZnSe, ZnS, diamond), the curvature radii of lens surfaces, and the spacing between optical elements. By changing these parameters and evaluating their impact on chromatic aberration correction across multiple bands, the design process identifies optimal material combinations without requiring exhaustive manual testing.
Solution Approach 2:
The patent replaces manual trial-and-error material selection with a computational design approach. Software algorithms calculate and evaluate multiple material and geometric configurations, automatically identifying the optimal combination that achieves apochromatic correction across SWIR, MWIR, and LWIR bands, thereby reducing design complexity.
3Adaptability or versatility
If a single optical system is designed to cover multiple infrared bands with different fields of view, then versatility is improved, but the number of available transmissive materials is limited
Solution Approach 1:
The patent designs optical elements that serve multiple functions: the same optical system provides both wide-angle search capability in LWIR and narrow-angle high-magnification analysis in SWIR. The dichroic beamsplitter universally handles multiple wavelength bands, directing each to appropriate detectors, thereby achieving multi-band versatility with a single integrated system rather than requiring separate systems for each band.
Solution Approach 2:
The system employs composite material architecture where different infrared-transmissive materials (germanium, silicon, zinc selenide, zinc sulfide, diamond) are used in different optical elements optimized for specific wavelength ranges. This composite approach maximizes the use of available materials, with each material selected for its optimal performance in specific IR bands, thereby achieving multi-band functionality despite material limitations.
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 approach enables the design of optical systems that effectively reduce chromatic aberrations across multiple infrared bands, providing a systematic method to select optimal material combinations for improved image focus and reduced spatial aberrations.
Implementation Method 1
When refractive optical elements are used within imaging systems, these components often take the form of lenses with one or two curvature radii crafted within a homogeneous material
Implementation Method 2
Chromatic aberration is caused by lens dispersion, where different colors of light travel at different speeds while passing through a lens
Data Source
AI summary
A method for cross-band apochromatic correction in a multi-element optical system. In one example, the method includes selecting a set of design wavelengths, determining a set of optical materials that are transmissive at each design wavelength, identifying a system of linear equations that describe the multi-element optical system in terms of a normalized optical power over the set of design wavelengths, generating multiple solutions for the system of linear equations, each solution defining a set of design optical materials selected from the set of optical materials and based at least in part on calculating mean squared difference values for wavelength pair combinations of design wavelengths in the set of design wavelengths, determining a merit value for each solution using a merit function, the merit value based on minimizing the mean squared difference values, ranking the merit values of the multiple solutions, and using at least one solution of the multiple solutions to design the multi-element optical system. In some examples, at least one design wavelength is a SWIR wavelength and at least one design wavelength is a LWIR wavelength.