Interferometer with Self-Apodization Compensation
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Solution Overview
Problem
Conventional Fourier transform interferometers face challenges in characterizing spectral distributions of radiation due to self-apodization effects, which are exacerbated by angular apertures, leading to convolution profiles with secondary maxima and reduced precision, particularly in applications requiring robust, compact, and precise spectral analysis like satellite-based Earth radiation analysis.
Innovation Solution
A Fourier transform interferometer with self-apodization compensation is designed, featuring a Mertz interferometer structure with a movable system of levers and prisms that adjust optical path lengths and thicknesses simultaneously, ensuring automatic synchronization and maintaining precise adjustments, thereby compensating for self-apodization and enhancing spectral resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Fourier transform interferometer is used, then the spectral distribution can be obtained through Fourier transformation, but self-apodization effects occur due to angular aperture that produce convolution profiles with secondary maxima and reduce measurement precision
Solution Approach 1:
The patent applies preliminary anti-action by introducing a compensation assembly with variable optical thickness into the optical path before the self-apodization effects fully degrade the measurement. This compensation assembly pre-adjusts the optical path difference to counterbalance the expected convolution profile distortions, thereby eliminating secondary maxima and improving spectral resolution before the harmful effects manifest in the final measurement
2Measurement precision
If the optical path length difference is varied to obtain spectral distribution, then spectral analysis is achieved, but the device complexity increases due to the need for precise control mechanisms
Solution Approach 1:
The patent merges the compensation assembly with the existing interferometer optical path, combining multiple functions into a unified structure. The compensation assembly is integrated such that it shares optical components and control mechanisms with the main interferometer, reducing the number of separate control systems while maintaining the ability to independently adjust optical path differences and compensate for self-apodization effects
3Reliability
If a robust interferometer design is implemented for satellite applications, then reliability is improved, but weight and dimensions increase
Solution Approach 1:
The patent applies dynamics by implementing a variable-thickness compensation assembly that can dynamically adjust its optical thickness during operation. This dynamic capability allows the interferometer to adapt to different measurement conditions and compensate for self-apodization effects in real-time, improving reliability without requiring a completely rigid and heavy structure. The variable thickness mechanism enables the system to maintain precision while using lighter materials and more flexible support structures
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 solution provides a robust, precise, and simple mechanism for self-apodization compensation, resulting in finer spectral resolution and more reproducible interferograms, suitable for applications like satellite-based radiation analysis, where weight and size constraints are critical.
Implementation Method 1
a beam splitter, which is adapted to split an initial beam of radiation into two secondary beams
Implementation Method 2
two optical channels, which are provided with reflecting surfaces for the secondary beams... the reflective surfaces being oriented to superimpose from the beam splitter the two secondary beams
Implementation Method 3
The interferometer produces a state of interference between two secondary beams which come from the same initial beam of radiation, and which follow distinct intermediate optical paths
Implementation Method 4
A difference in length between the optical paths is varied, which in turn causes a variation in the intensity of an output beam formed by overlapping the two secondary beams
Implementation Method 5
an output optical path, which comprises a detector disposed to receive the output beam, and produce a signal representative of the intensity of this output beam
Data Source
AI summary
A Fourier transform interferometer with self-apodization compensation comprises at least one pair of movable prisms (21, 31, 22, 32) forming a plate whose thickness varies as the optical path length difference is itself varied. The prisms are moved by means of a movable system with a single degree of freedom, comprising two support arms (10, 11) and at least two pivoted levers (12, 13) articulated for rotation. The interferometer is adapted for installation on board a satellite to spectrally analyze radiation originating from the Earth's surface.