Mid Infrared Continuous Zoom System with Diffractive Correction
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Solution Overview
Problem
Traditional mid infrared spectral band systems lack a continuous zoom range greater than 25X, relying on discrete fields of view or discontinuous zoom ranges for thermally imaging distant objects in the 3-5 µm range.
Innovation Solution
A mid infrared spectral band continuous zoom system comprising a positive element, a negative focal length moving group, a positive focal length moving group, a relay group, and a cooled infrared camera, where the negative and positive focal length moving groups are moved relative to each other to provide a continuous zoom range with a focal length change greater than 25X, allowing for a variable field of view from 1.25° to over 38°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional mid infrared spectral band systems use discrete fields of view or discontinuous zoom ranges, then the system structure is simpler, but the zoom range is limited and cannot provide continuous zoom greater than 25X
Solution Approach 1:
The patent employs multiple moving groups (first moving group with negative focal length, second moving group with positive focal length) that can move relative to each other along the optical axis to continuously adjust the focal length and provide a continuous zoom range greater than 25X, transforming a static optical system into a dynamic one
Solution Approach 2:
The patent introduces a fixed intermediate image plane between the object and the infrared camera detector, which serves as an intermediary to facilitate the continuous zoom function. This intermediate plane allows the moving groups to adjust the focal length without directly affecting the detector position, enabling continuous zoom while maintaining image quality
2Adaptability or versatility
If the system uses a continuous zoom range greater than 25X, then the adaptability for different fields of view is improved, but the chromatic aberration increases
Solution Approach 1:
The patent uses diffractive optical surfaces with specific diffraction orders to change the optical path and reduce chromatic aberration. The diffractive surfaces introduce wavelength-dependent phase delays that compensate for the chromatic dispersion in the optical materials, allowing continuous zoom while maintaining image quality across different wavelengths
Solution Approach 2:
The patent employs composite optical designs combining refractive elements (lenses with positive and negative focal lengths) and diffractive elements (surfaces with diffraction patterns). This composite approach allows the system to achieve continuous zoom functionality while the diffractive components correct the chromatic aberrations introduced by the refractive elements
3Adaptability or versatility
If multiple moving groups are used to achieve continuous zoom, then the zoom functionality is improved, but the device complexity and number of moving parts increase
Solution Approach 1:
The patent divides the optical system into multiple functional groups: a fixed front group, a first moving group with negative focal length, a second moving group with positive focal length, and a fixed rear group. Each group has a specific function, and the moving groups can move independently relative to each other to achieve continuous zoom while maintaining a manageable level of complexity through functional segmentation
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
Enables continuous thermal imaging with a large zoom range, maintaining a fixed intermediate image plane and reducing chromatic aberrations through the use of specific optical materials and diffractive surfaces, effectively addressing the limitations of traditional systems.
Implementation Method 1
a positive element (102) that focuses incoming light (250) from the object
Implementation Method 2
a negative focal length moving group (104) that intercepts the light (250) being focused by the positive element (102) and creates a virtual image
Implementation Method 3
a positive focal length moving group (106) that relays the virtual image created by the negative focal length moving group (104) to an intermediate image
Implementation Method 4
a relay group (110) that relays the intermediate image to a final image plane (158)
Implementation Method 5
a cooled infrared camera (114) that thermally images the object at the final image plane
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A mid infrared spectral band continuous zoom system is described herein that can provide a continuous zoom range with a focal length change greater than 25X when thermally imaging a distant object. In addition, a method is described herein for using the mid infrared spectral band continuous zoom system to thermally image the distant object.