Wavefront Analysis via Multilateral Interferometry
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Solution Overview
Problem
Current wave surface analysis methods, such as Shack-Hartmann analyzers and phase-shift interferometers, are limited in their ability to analyze fragmented wave surfaces with unevenness greater than the analysis wavelength, leading to indeterminate height measurements, which is prohibitive for applications in segmented optics and diffractive elements.
Innovation Solution
A two-dimensional diffraction grating is used to generate interferograms from sub-beams with lateral offsets, allowing for the analysis of fragmented wave surfaces by decomposing the interferogram into elementary interferograms and processing their shifts and tilts to determine the rates of increase, enabling unambiguous measurement of wave surface unevenness over a larger dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Shack-Hartmann analyzers or phase-shift interferometers are used for wave surface analysis, then measurement capability is provided, but the dynamic range is limited to the analysis wavelength, causing indeterminate height measurements for fragmented wave surfaces with unevenness greater than the wavelength
Solution Approach 1:
The wave surface is analyzed by segmenting it into multiple planar regions separated by discontinuities. Each region is independently analyzed to determine its orientation and height, allowing the system to handle fragmented wave surfaces with unevenness exceeding the wavelength while maintaining measurement precision across the entire surface.
Solution Approach 2:
The patent extends measurement from a single wavelength dimension to multiple wavelengths. By capturing interferograms at different wavelengths and analyzing the phase differences across these dimensions, the system achieves unambiguous height measurements for fragmented surfaces with large discontinuities, effectively adding a wavelength dimension to expand the dynamic range.
2Measurement precision
If a diffraction grating is used to generate sub-beams with lateral offsets, then interferograms can be obtained for analysis, but the system becomes more complex compared to conventional analyzers
Solution Approach 1:
The diffraction grating serves multiple functions simultaneously: it generates the sub-beams with lateral offsets needed for interferometry, it acts as a reference element, and it enables wavelength multiplexing. This multi-functionality reduces the need for separate components that would otherwise be required in conventional systems, offsetting the added complexity with functional consolidation.
Solution Approach 2:
The system varies the wavelength parameter to encode height information for different regions of the fragmented wave surface. By capturing interferograms at multiple wavelengths and analyzing the phase differences, the system extracts unambiguous height measurements without requiring additional physical components, managing complexity through parameter variation rather than structural multiplication.
3Measurement precision
If conventional interferometric methods are used, then wave surface analysis is possible, but fragmented surfaces with discontinuities greater than the wavelength produce indeterminate height measurements
Solution Approach 1:
The patent employs periodic variation of the wavelength parameter to probe the fragmented wave surface. By capturing interferograms at multiple discrete wavelengths and analyzing the phase differences across this periodic parameter variation, the system resolves the ambiguity in height measurements for discontinuities larger than a single wavelength, ensuring deterministic results.
Solution Approach 2:
The patent introduces an intermediary computational process that analyzes phase differences across multiple wavelengths. This intermediary analysis step acts as a mediator between the raw interferogram data and the final height measurements, resolving ambiguities and ensuring deterministic height values for fragmented surfaces with large discontinuities.
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 method allows for the precise analysis of wave surface unevenness and reconstruction of the original wave surface, overcoming the limitations of existing technologies by providing a dynamic range greater than the analysis wavelength, enabling accurate measurement of wave surface features with varying amplitudes.
Implementation Method 1
A two-dimensional diffraction grating is used to generate interferograms from sub-beams with lateral offsets
Implementation Method 2
allowing for the analysis of fragmented wave surfaces by decomposing the interferogram into elementary interferograms
Data Source
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AI summary
The invention relates to a wavefront analysis method involving multilateral interferometry with frequency difference. According to the invention, a diffraction grating (GR) with two-dimensional meshing is placed on the path of the beam to be analysed and at least two interferograms with at least two different colours are processed, each interferogram being obtained in a plane (Ps)from two sub-beams (R1, R2) with different diffraction orders. The invention can be used to analyse and correct sheared wavefronts (S).