Wide Angle MWIR F-theta Lens Aberration Correction
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Solution Overview
Problem
Existing MWIR F-theta lenses suffer from low sensitivity and poor signal-to-noise ratio due to small fields of view, lack of cold shields, and non-cooled detectors, which limits their effectiveness in wide-angle surveillance and reconnaissance applications.
Innovation Solution
A wide angle MWIR F-theta lens design comprising multiple optical groups with specific refractive indices and dispersions, a cold shield as the aperture stop, and a focal plane array, which corrects for monochromatic and chromatic aberrations over the 5000 nm to 3300 nm spectrum, achieving F-theta distortion correction and high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional MWIR lens without cold shield and cooling is used, then the device complexity is reduced, but the sensitivity and signal-to-noise ratio deteriorate
Solution Approach 1:
A cold shield is introduced as an intermediary component between the optical elements and the detector. The cold shield acts as a thermal barrier that blocks stray infrared radiation from reaching the detector, thereby improving the signal-to-noise ratio and sensitivity without requiring complex active cooling systems for the detector itself.
2Area of stationary object
If a wide angle field of view is implemented, then the coverage area is improved, but the resolution and image quality deteriorate
Solution Approach 1:
The lens system is divided into multiple optical groups (first, second, third, and fourth optical groups) with specific refractive indices and dispersions. Each group is designed to contribute to correcting specific aberrations, allowing the system to achieve both wide field of view and high resolution by segmenting the optical correction function across multiple elements.
Solution Approach 2:
The lens design utilizes specific refractive indices and dispersions of optical materials to correct aberrations. By carefully selecting and optimizing these optical parameters across the multiple groups, the system achieves F-theta distortion correction and maintains high resolution over a wide field of view.
3Measurement precision
If chromatic aberration correction is implemented, then the image quality is improved, but the device complexity increases
Solution Approach 1:
The lens system employs composite optical design combining multiple optical groups with different refractive indices and dispersions. This composite approach enables effective chromatic aberration correction across the MWIR spectrum (3300-5000 nm) by leveraging the complementary optical properties of different materials in each group.
4Measurement precision
If F-theta distortion correction is achieved, then the target position detection accuracy is improved, but the lens design complexity increases
Solution Approach 1:
The F-theta distortion correction is achieved by segmenting the optical system into multiple groups, each contributing to specific aspects of distortion correction. This modular approach allows the complex distortion correction function to be distributed across simpler, more manageable optical elements.
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 lens provides high resolution and sensitivity over a wide field of view, with improved signal-to-noise ratio and chromatic aberration correction, making it suitable for airborne remote sensing applications.
Implementation Method 1
multiple optical groups with specific refractive indices and dispersions, which corrects for monochromatic and chromatic aberrations over the 5000 nm to 3300 nm spectrum
Implementation Method 2
cold shields are used in IR optical devices for military, scientific, and industrial applications to protect IR sensors from stray IR radiation
Implementation Method 3
the position of the focused spot is dependent on the product of the Effective Focal Length (EFL) and the tangent of the field of view (FOV) angle θ
Data Source
AI summary
A wide angle MWIR F-theta lens with an F# of 2. The lens is deployed on airborne platforms for remote sensing applications. The lens is corrected for monochromatic and chromatic aberrations over the wavelength range 5000 nm-3300 nm. The image of the remote target is formed on a focal plane which may constitute CCD or CMOS with micro lenses. The lens comprises four groups of optical elements with a cold shield/aperture stop located behind the last group. One embodiment of the lens includes five types of optical materials and while another embodiment of the lens includes only two types of optical materials.