Transient Digital Moire Phase-Shifting Interferometry for Optical Surface Shape
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Solution Overview
Problem
The two-step carrier splicing method for digital moire phase-shifting interferometry sacrifices instantaneous vibration resistance for expanded measurement range, limiting its application in high-precision surface shape measurement of optical elements.
Innovation Solution
A transient digital moire phase-shifting interferometric measuring device utilizing polarization gratings to simultaneously load two spatial carriers, allowing for instantaneous anti-vibration characteristics while expanding the measurement range by generating two interference patterns with different frequencies, eliminating the need for sequential interferogram acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the two-step carrier splicing method is used to expand measurement range, then the residual wavefront bandwidth is improved, but the instantaneous anti-vibration characteristics are lost
Solution Approach 1:
The patent merges two spatial carriers (first spatial carrier and second spatial carrier) into a single composite spatial carrier that contains both carriers simultaneously. This allows two interferograms to be acquired at the same time in one exposure, rather than requiring separate acquisitions. The composite spatial carrier is formed by superimposing the first spatial carrier and the second spatial carrier, enabling simultaneous measurement of different carrier frequencies while maintaining instantaneous anti-vibration characteristics.
Solution Approach 2:
The patent introduces a new dimension to the spatial carrier by creating a composite carrier that operates in a higher-dimensional space containing multiple carrier frequencies. Instead of sequentially applying carriers in time (one-dimensional approach), the invention applies multiple carriers simultaneously in frequency space (multi-dimensional approach), allowing parallel acquisition of interferograms with different carriers while maintaining temporal coherence for vibration resistance.
2Reliability
If traditional digital moire phase-shifting interferometry is used, then instantaneous anti-vibration characteristics are maintained, but the residual wavefront bandwidth is limited
Solution Approach 1:
The patent combines multiple spatial carriers into a single composite spatial carrier that enables simultaneous acquisition of multiple interferograms. By merging the first spatial carrier and second spatial carrier into one composite carrier, the system achieves expanded measurement range equivalent to traditional phase-shifting interferometry while maintaining the instantaneous anti-vibration capability of digital moire methods.
Solution Approach 2:
The composite spatial carrier serves multiple functions simultaneously: it provides both the first spatial carrier and second spatial carrier information in a single structure, enabling the system to achieve both the instantaneous anti-vibration characteristics and the expanded measurement range. This multi-functional carrier resolves the contradiction by making a single element perform what previously required multiple separate operations.
3Manufacturing precision
If sequential interferogram acquisition is used, then measurement range is expanded, but measurement time increases and vibration resistance is compromised
Solution Approach 1:
The patent merges the acquisition of multiple interferograms into a single simultaneous measurement by using a composite spatial carrier. Instead of acquiring interferograms sequentially (first interferogram, then second interferogram), the system acquires both interferograms at the same time in one exposure, dramatically reducing measurement time and eliminating the vulnerability to vibrations between sequential measurements.
Solution Approach 2:
The patent ensures continuous acquisition of all necessary interferogram data in a single uninterrupted measurement cycle. By using the composite spatial carrier to encode multiple carriers simultaneously, the system maintains continuous measurement action without interruption or sequential steps, thereby eliminating time loss and maintaining vibration resistance throughout the measurement process.
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 approach enhances measurement accuracy and retains instantaneous anti-vibration characteristics, effectively expanding the measurement range of digital moire phase-shifting methods to match traditional phase-shifting interferometry, reducing error sources and improving precision.
Implementation Method 1
Polarization grating is a diffractive optical element which realizes selective light splitting based on the polarization state of incident light. The diffraction angle depends on the spatial period of the grating.
Implementation Method 2
Polarization grating is a diffractive optical element which realizes selective light splitting based on the polarization state of incident light. When the incident light of the polarization grating is linearly polarized light, its outgoing light is +1st order diffracted light and -1st order diffracted light
Implementation Method 3
Transient digital moire phase-shifting interferometric measuring device and method for the surface shape of an optical element. Digital moire phase-shifting interferometry is an aspheric surface detection method
Data Source
AI summary
A transient digital moire phase-shifting interferometric measuring device and method for a surface shape of an optical element solves a defect that an instantaneous vibration resistance needs to be sacrificed for a measurement range when using a two-step carrier splicing method, and expands the measurement range of a digital moire phase-shifting method while retaining instantaneous anti vibration characteristics of the digital moire phase-shifting method. The transient digital moire phase-shifting interferometric measuring device includes a light source, a beam splitter, a reference lens, a first polarization grating, a measured lens, a second polarization grating, a first imaging objective lens, a first camera, a second imaging objective lens and a second camera. Different carriers are loaded through a spectral performance of a polarization grating, and the polarization grating is used to separate two beams of an interference light, and two actual interference patterns are obtained at a same time.