Study On Micro-Nano Displacement Measurement System Based On Optical Lever

Micro cantilever is one of the most basic structures in MEMS(Micro-electro-Mechanical System);it is often used as a key element in micro sensors.Micro cantilever has been widely used in many fields;it can not only be applied in atomic force microscopy(AFM)to measure surface morphology and detect micro force,but also have an important application in the detection of various biochemical quantities.Micro cantilever can realize precise sensing.In this paper,to meet the requirement of static measurement for micro cantilever deflection,self-designed optical lever light path system and Position Sensitive Detector(PSD)are used.The resolution of the measurement system can reach 0.06μm.Using this system to measure small deflection of homemade cantilever,through compared with the actual displacement of micro-positioning platform,the results are basically identical.It verified the reliability of the system.The major works in the thesis are as the following:(1)Introduction about the research background of the subject,including micro cantilever beam configuration,micro cantilever working mode,the application of micro cantilever sensor.The advantages and disadvantages of the cantilever sensor readout system are reviewed and analyzed.Through compared with various measurement methods,optical lever method is confirmed to use in this system.The main work of this paper is based on the principle of optical lever to measure the deflection of cantilever,and the main components of the system are given.(2)Building the whole measurement system.Firstly,the basic principle of measurement system is introduced,and the geometric relationship between the various parts of the system is derived.Then the whole optical measurement system of cage type is established,suitable element of the system is confirmed;finally the basic knowledge of PSD is introduced,and following up processing circuit and Labview software acquisition interface are built.(3)Calibrating the linearity of PSD so as to determine the measuring range.Then by fitting the measurement data,the sensitivity of the measurement system is calibrated.Finally,using the sensitivity to measure the deflection of cantilever.(4)Data error is analyzed according to the measurement results.Analysis the source of error so as to improve the system measurement accuracy(5)Conclusions were drawn based on the above work,and discussed the deficiencies in the system,expounds the further work demand.