Research On Vibration Frequency Spectrum Measurement Based On Optical Fiber Interferometer

Optical interferometry has been applied in a lot of areas along with a great deal of modern new interferometer, new measurement principles and methods emerging. Moreover it has become one of main means of high accuracy measurement.According to measurement principles of Mach-Zehnder fiber interferometer, linear CCD as a tool of picking up fringes replaces the traditional photoelectricity detector. Combining with the image grabber and computer, automatic measurement of interference fringes displacement caused by vibration is realized.According to characteristics of Mach-Zehnder interferometer, the hardware structure of this system is submitted. The technique parameters of lamp-house, optic fiber, linear CCD and image grabber that we choose are given. The principles of light phase modulating and interference fringes forming are demonstrated in details.About digital image technology is studied from two aspects of interference fringes capturing, dealing with and analyzing. Application software exploitation is carried out by VC++. The capturing of interference fringes continuously is realized. The design of low-pass filter and image smoothing are finished, according to the characteristics of interference fringes. Orientation error of interference fringe center is removed. Good effect is obtained. The application of derivative sign binary algorithm in interference fringe skeletonizing overcomes the difficulty of threshold picking in ordinary binary methods. Thus the accuracy of system is improved. By DFT, the spectrum of vibration measured is analyzed.Finally in the paper, the error of system is discussed and the resolution is alao proposed. For the purpose of distinguishing shift direction of fringes, the max shifting speed-allowed is submitted. In order to application we extend its application.The technology proposed by this paper has large application foreground in military affairs and secrecy monitoring, gathering many advantages of high accuracy, delicacy structure, bearing hazard environment, anti-eletromagnetism,...