Interferometric Apparatus Vibration Compensation
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Solution Overview
Problem
Conventional optical interferometric surface profilometers are severely affected by environmental vibrations, leading to inaccurate measurements during the observation and measurement of vibratory behavior in micro-electro-mechanical systems (MEMS) and micro-opto-electro-mechanical systems (MOEMS), as existing methods fail to effectively mitigate the impact of vibrations on interferometric results.
Innovation Solution
A method and apparatus that generate both high-coherent and low-coherent inspection beams, which are projected onto a tested surface to produce interferograms, allowing for the calculation of vibration displacement and frequency by analyzing light intensity, thereby compensating for vibrations and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical interferometric surface profilometer is used for static measurement, then measurement precision is improved, but the system becomes severely affected by environmental vibrations
Solution Approach 1:
The patent converts the harmful vibration effect into a useful measurement signal. By using a high-coherent light source to generate interference fringes that respond to vibrations, the system transforms vibration-induced phase changes from measurement errors into detectable signals that reveal vibratory behavior characteristics, thereby benefiting from what was previously harmful
Solution Approach 2:
The patent introduces an intermediary measurement approach by using light intensity analysis of interference fringes as a mediator between the vibration source and the measurement system. This intermediary method allows indirect detection of vibration characteristics without requiring direct mechanical contact or complex anti-vibration mechanisms
2Stability of the object's composition
If anti-vibration facilities are used to protect measurement, then measurement stability is improved, but the system cannot measure voluntary vibration or passive induced vibration of the object
Solution Approach 1:
The patent transitions from a static measurement approach to a dynamic measurement approach. By capturing interference fringes at multiple phases of the vibration cycle and analyzing light intensity variations, the system adapts to dynamic vibratory conditions, enabling measurement of both voluntary and passive induced vibrations while maintaining stability through computational methods
3Productivity
If fast data acquisition rate is used to reduce sensitivity to vibration, then measurement speed is improved, but the system complexity increases
Solution Approach 1:
The patent replaces complex mechanical anti-vibration systems with an optical-based interference fringe analysis method. By using light intensity measurements and computational phase analysis, the system achieves vibration compensation without requiring complex mechanical isolation components, fast scanners, or multiple cameras
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 method effectively determines vibration displacement and frequency, enabling accurate surface profiling even under vibrating conditions by integrating band-pass filtering and instant displacement measurement, reducing errors in 3D profile reconstruction and enhancing the robustness of interferometric scanning.
Implementation Method 1
modulating at least a light source for generating simultaneously at least a high-coherent inspection beam and at least a low-coherent inspection beam... obtaining a high-coherent interferogram of the tested surface
Data Source
AI summary
A exemplary method for determining vibration displacement in interferometric scanning, in which two optical signals having a phase difference with each other of a high-coherence interferogram corresponding to a tested surface is detected for determining a shifting displacement between the reference plane of interferometric apparatus and the tested surface. In one embodiment, a series of the shifting displacements with respect to a time interval are measured for determining the vibrating frequency of the tested surface by spectrum analysis. Meanwhile, an exemplary interferometric apparatus is also disclosed for calculating the relative position between the tested surface and the reference plane of interferometric apparatus whereby the interferometric apparatus is capable of compensating influences of vibration caused by the environment or the tested surface itself so as to obtain the surface profile and vibration frequency of the tested surface.