Compact Anamorphic Refractive Lens Assembly for Mobile Thermal Imaging
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Solution Overview
Problem
Existing anamorphic lenses for cinema projection are too large and heavy to be incorporated within mobile imaging systems like aerial surveillance systems, and they do not support high resolution imaging in the thermal infrared spectrum.
Innovation Solution
A compact anamorphic refractive objective lens assembly with a passively athermal lens group, using materials like silicon and zinc sulfide, that maintains focus over a wide temperature range and reduces size and weight, allowing integration into mobile imaging systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional anamorphic lenses are used for high resolution thermal infrared imaging, then imaging quality is improved, but size and weight increase making them unsuitable for mobile platforms
Solution Approach 1:
The lens assembly is divided into multiple discrete lens elements (first lens element, second lens element, third lens element, fourth lens element) with specific materials and focal lengths. This segmentation allows optimization of each element's contribution to the overall imaging performance while reducing total mass compared to a monolithic lens design.
Solution Approach 2:
The patent employs composite material construction with different lens elements made from materials having distinct refractive indices and thermal properties. This composite approach enables high resolution thermal infrared imaging while managing weight and thermal expansion characteristics across the lens assembly.
2Measurement precision
If conventional anamorphic lenses are used, then imaging quality is improved, but the lens assembly becomes too large for mobile imaging systems
Solution Approach 1:
By segmenting the optical system into multiple lens elements with specific focal lengths and spacing, the patent achieves the required anamorphic ratio and imaging resolution in a more compact configuration than conventional single-element or simple multi-element designs.
Solution Approach 2:
The patent utilizes the anamorphic configuration to achieve differential magnification in orthogonal dimensions (first dimension versus second dimension). This dimensional approach allows compact lens spacing while maintaining high resolution imaging capability through asymmetric optical power distribution across the lens elements.
3Ease of manufacture
If standard lens materials are used, then manufacturing is simplified, but focus stability over wide temperature ranges deteriorates
Solution Approach 1:
The patent selects lens materials and designs each element with specific refractive indices and thermal expansion parameters to compensate for temperature-induced focus shifts. The combination of materials with different thermal characteristics creates an athermalized system that maintains focus stability across wide temperature ranges while remaining manufacturable.
Solution Approach 2:
By using composite material construction with lenses made from materials having different thermal properties, the patent achieves passive athermalization. The differential thermal expansion and refractive index changes of the composite materials compensate for each other, maintaining focus stability without complex active control mechanisms.
4Length of stationary object
If compact lens design is implemented, then suitability for mobile platforms is improved, but manufacturing precision requirements increase
Solution Approach 1:
The segmented lens design allows each element to be manufactured and tested independently with standardized precision requirements. This modular approach distributes the manufacturing precision burden across multiple components rather than requiring extreme precision in a single compact element, facilitating achievable manufacturing tolerances.
Solution Approach 2:
Each lens element is designed with specific local optical properties (focal length, refractive index, curvature) optimized for its position in the assembly. This local quality approach allows standard manufacturing processes to produce each element within reasonable tolerances, as the cumulative effect of multiple elements achieves the overall compact high-precision imaging goal.
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 compact lens assembly provides high resolution imaging in the thermal infrared spectrum with reduced size and weight, suitable for mobile platforms like aerial surveillance systems, maintaining focus despite temperature fluctuations.
Implementation Method 1
The anamorphic lens enlarges the image along a first axis to a different extent than along a second perpendicular axis. That is, the recorded image may be asymmetrically stretched by the anamorphic lens
Implementation Method 2
a first cylindrical lens having a surface optically powered in a first dimension... configured to expand the thermal infrared radiation in a plane of the first dimension
Implementation Method 3
a first group of lenses each having a rotationally symmetric surface optically powered in both the first dimension and a second dimension orthogonal to the first dimension
Implementation Method 4
a fold mirror interposed between the focus cell and the relay lens group and positioned to direct the thermal infrared radiation from the focus cell to the relay lens group
Implementation Method 5
a dewar assembly positioned along the optical path, the dewar assembly including a cold stop and an optical detector
Data Source
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AI summary
Aspects and embodiments are generally directed to compact anamorphic refractive objective lens assemblies. In one example, a refractive objective lens assembly includes a passively athermal anamorphic lens group including at least a first cylindrical lens having a surface optically powered in a first dimension, the first anamorphic lens group positioned to receive thermal infrared radiation, a focus cell positioned to receive the radiation from the anamorphic lens group, the focus cell including a first group of lenses each having a rotationally symmetric surface optically powered in the first dimension and a second dimension orthogonal to the first dimension, a relay lens group positioned receive the radiation from the focus cell, the relay lens group including a second group of lenses each having a rotationally symmetric surface optically powered in both the first and second dimensions, and a dewar assembly including a cold stop and an optical detector.