In this paper, we propose a real-time solution based on multi-point diffraction-based interferometer that is capable of 2-dimensional full-field, in-plane strain measurement and analysis with micrometric sensitivity and accuracy. We discuss the various techniques used to provide real-time dynamic analysis of strain over space and time so as to highlight trends of potential in-situ stress build-up over a device.
Multipoint Diffraction Strain Sensor (MDSS) is a non-contact whole field strain sensing system. DOE-based lens arrays
are designed and used to replace the typical micro-lens array in our MDSS system. These DOE patterns are displayed on
the liquid crystal spatial light modulator. So with different focal length, tunable strain sensitivity is achieved. Calibrations
are performed to test the measurement accuracy and precision of the system.
Multipoint Diffraction Strain Sensor (MDSS) is a novel and promising strain sensing system to acquire whole field
strain information with high accuracy without the need for numerical differentiation. Compared to traditional optical
diffraction strain sensors, the main advantage of MDSS is the use of micro-lens array to get whole field information.
Both tilt and in-plane strain can be acquired separately by using two symmetric incident laser beams. However, it is
costly and troublesome to fabricate, adjust or replace lens arrays for different applications. A practical way to solve this
problem is to use a liquid crystal lens as spatial light modulator which displays Diffractive Optical Element (DOE) based
lens array. This liquid crystal lens is software controlled capable to display any user designed DOE pattern. The
sensitivity and field of interrogation is thus tuneable by changing focal length of lens arrays. Moreover arbitrary size or
shape of lens arrays can be designed to measure certain part of the specimen in most interest. Experimental results with
different lens arrays are demonstrated for uniform rotations.
The Laser Doppler Vibrometer (LDV) is one of the most efficient devices used in non-contact vibration measurement.
It is wildly used in industry such as MEMs, hard-disk fabrication. Various precision and different range are required in
different circumstances. So calibration for a LDV is crucial to its versatility. In this paper a simple but effective
calibration method for the LDV is introduced. This will provide industries with a suitable calibration method to reduce
the cost and simplify the procedure of calibration and offer a reference for LDV applications.