Mid-Infrared Refractive Lens Assembly with Aplanatic Front Element
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Solution Overview
Problem
Existing objective lens assemblies do not provide sufficient performance in the mid-infrared (MIR) light spectrum, particularly in terms of image quality and resolution, due to issues with achromatic aberrations and optical throughput.
Innovation Solution
The design incorporates a refractive objective lens assembly with multiple lens elements made of materials like germanium, zinc sulfide, and zinc selenide, optimized for the MIR spectrum, featuring aplanatic front lens elements, anomalous dispersion in the rear lens group, and adjustable separation distances to minimize RMS wavefront error and maximize numerical aperture and field of view.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing objective lens assemblies are used for MIR spectrum, then the device can operate in MIR range, but image quality and resolution are insufficient due to achromatic aberrations
Solution Approach 1:
The objective lens assembly is divided into multiple lens elements (at least three) with different optical powers and materials. Each lens element contributes to correcting specific aberrations, with the first lens element having negative optical power and the second having positive optical power, working together to reduce achromatic aberrations while maintaining MIR performance
Solution Approach 2:
The patent employs lens elements made from different materials optimized for MIR spectrum, including germanium, zinc selenide, and silicon. These composite material approaches allow each element to contribute different refractive properties, enabling chromatic aberration correction across the MIR wavelength range while maintaining high image quality
2Measurement precision
If existing objective lens assemblies are used for MIR spectrum, then the device can operate in MIR range, but resolution is insufficient
Solution Approach 1:
The patent optimizes specific parameters including the optical power ratio between lens elements, separation distances, and curvature radii. The first lens element has negative optical power while the second has positive optical power, with their ratio carefully controlled to maximize resolution. The separation distance between elements is optimized to balance aberration correction with maintaining high numerical aperture for improved resolution
3Measurement precision
If multiple lens elements are used to correct aberrations, then image quality improves, but device complexity increases
Solution Approach 1:
The lens assembly is segmented into at least three distinct elements with specific functional assignments. The first element (negative power) and second element (positive power) form the core aberration correction group, while additional elements can be added for further optimization. This segmented approach achieves high image quality through controlled complexity rather than excessive element count
Solution Approach 2:
Each lens element is designed with specific local properties: the first element has negative optical power with specific curvature characteristics, the second has positive optical power with complementary properties. Each element's material, shape, and position are locally optimized for its specific function in the overall aberration correction scheme, achieving high image quality without unnecessary complexity
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 achieves high-resolution, diffraction-limited performance over a wide field of view with reduced achromatic and chromatic aberrations, enhancing image quality and spectral fidelity in the MIR range.
Implementation Method 1
a refractive objective lens assembly having a plurality of spaced apart, refractive lens elements that operate in a mid-infrared spectral range
Implementation Method 2
the rear lens elements are designed to achieve anomalous dispersion such that the effective focal length of the rear lens group decreases with increasing wavelength
Data Source
Figure 1A~1B
Figure 1C
Figure 1D
AI summary
A mid-infrared objective lens assembly (10) includes a plurality of spaced apart, refractive lens elements (20) that operate in the mid-infrared spectral range, the plurality of lens elements (20) including an aplanatic first lens element (26) that is closest to an object (14) to be observed. The first lens element (26) has a forward surface (36) that faces the object (14) and a rearward surface (38) that faces away from the object (14). The forward surface (36) can have a radius of curvature that is negative.