Dynamic Interference Imaging for MEMS Vibration Measurement
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Solution Overview
Problem
Conventional surface topography interferometric microscopes lack dynamic measurement capabilities, especially for wide-band driving sources like micro cantilevers in water, and existing laser Doppler velocimetry methods are time-consuming and prone to environmental interference, failing to provide full-field measurements for MEMS devices.
Innovation Solution
A method and apparatus using frequency sweeping and two-dimensional image scanning to acquire dynamic interference images, processing them to obtain fringe density indices, which identify dynamic characteristics of vibratory objects, employing a center control, synchronization control, light-emitting unit, and imaging unit to generate and capture interferograms, and adjust the position of the object.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser Doppler velocimetry is used for vibration measurement, then measurement precision is improved, but measurement time increases and environmental interference worsens
Solution Approach 1:
The patent replaces the laser-based Doppler velocimetry system with a white light interferometry system. This substitution eliminates the need for expensive laser sources and complex optical paths while achieving full-field dynamic measurement without point-by-point scanning, thereby reducing measurement time and environmental sensitivity.
Solution Approach 2:
The patent transitions from single-point measurement in the time domain to full-field spatial measurement using interferometric fringes. By capturing the entire vibration mode field simultaneously through white light interferometry, the system achieves both high precision and real-time measurement capability.
2Difficulty of detecting and measuring
If laser beam scanning is used for surface inspection, then resonance frequency detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the complex laser Doppler module and strobed light displacement measuring module with a simplified white light interferometric system. The white light source with broadband spectrum enables direct observation of interference fringes without requiring complex optical path configuration or synchronization mechanisms.
Solution Approach 2:
The patent uses white light interference fringes as a visual copy or representation of the surface topography and vibration mode. By capturing the interference pattern directly with a camera, the system obtains resonance frequency information without requiring physical scanning or complex signal processing.
3Measurement precision
If point-by-point scanning is used for vibration measurement, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent transitions from one-dimensional point-by-point scanning to two-dimensional full-field measurement. By capturing the entire vibration mode field simultaneously through white light interferometry, the system achieves both high precision and real-time measurement capability, eliminating the time-consuming sequential scanning process.
Solution Approach 2:
The patent merges multiple measurement points into a single full-field capture. Instead of measuring each point separately and then combining results, the interferometric system captures the entire vibration mode pattern in one shot, significantly improving measurement efficiency while maintaining precision.
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
Enables efficient and real-time detection of dynamic characteristics, reducing the risk of damage to micro devices and simplifying the optical setup, allowing for full-field measurements of MEMS devices without the need for expensive laser sources.
Implementation Method 1
acquire a series of dynamic interference images of the vibratory object
Implementation Method 2
the light-emitting unit is controlled by the synchronization control to generate the strobed light
Data Source
AI summary
A method and apparatus for identifying dynamic characteristics of a vibratory object is provided in the present invention, in which a series of dynamic interference images of the vibratory object is acquired through a frequency sweeping procedure and a two-dimensional image scanning procedure. Thereafter, the acquired images are processed for obtaining the corresponding differential fringe density index by signal processing technique of band-pass filtering method so as to further identify the dynamic characteristics of the vibratory object.