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Deflection Angle Measurement System For Microbeams Based On Microscopic Optical Lever

Posted on:2015-11-23Degree:MasterType:Thesis
Country:ChinaCandidate:L LiuFull Text:PDF
GTID:2298330452958855Subject:Instrumentation engineering
Abstract/Summary:PDF Full Text Request
Microbeam as one of the most basic MEMS structure, is often used as a microsensing element. Not only can measurement the surface topography like in AFM, canalso be detection of the heat, biological and chemical force etc.. But with furtherreduce the size of the microbeam, a higher requirements was proposed by thedetection technology.This thesis presents a microscopic system for the fast deflectionangle measurement of microbeams. The system consists of an infinite conjugateimaging system and an integrated optical lever. The laser beam of the optical lever isfocused by the infinite objective to a spot size of10μm. A current-mode circuit isdesigned for signal processing of QPD output, and achieves15MHz in bandwidth.The measurement range and resolution of this system are±4°and1.2", respectively.As a test, this system is used to measure the deflection angles at the free end of amicrobeam under stepping load. The measurement results are consistent well withthe calculation by using Timoshenko beam theory. The major works in the thesis areas the following:1. Systematically analyzed various methods of angle measurements. A newmethod based on the combination of the microscopic optics and the optical lever wasproposed to measure the deflection angle of microstructures. And gived the systemschematic diagram, the system mainly includes the microscopic optical lever path,photodetector readout circuit, data acquisition, processing and motor drive, etc..2. Designed and built the microscopic optical lever. The optical path not onlycan be real-time observed the microstructure, but also can got a smaller spot, theoptical lever is able to measure the deflection angle of microstructures. The designadopt a cage structure, intergrated into the electric displacement, therefore theapplication will be convenient.3. The photodetector readout circuit was designed. This circuit is based oncurrent mode circuits, and has a large bandwidth, large measurement range, highresolution, and low noise. The software based on the LabVIEW was designed,having functions of data acquisition and processing, motor control, etc..4. Experiments with the system were conducted. The amplitude frequency response of several microcantilevers of atomic force microscopy were obtained, andthe results were compared with the results measured by a commercial AFM.Measured the deflection of the microcantilever NSG-10under stepping load, andcompared with the results obtained by theoretical calculations.5. Conclusions were drawn based on the above work, and discussed thedeficiencies in the system, expounds the further work demand.
Keywords/Search Tags:Microbeam, Microscopic optical lever, Deflection angle, Current-mode circuit, Atomic force microscope
PDF Full Text Request
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