Laser Interferometer Applying To The Measurement For Vibration Of Low-frequency And Tininess

With the development of science and technology, the detection of weak signal is being paid more and more attention. The measurement technique of laser interference has characteristics of high accuracy, wide dynamic range and electric insulation in terms of the detection of weak signal. In the measurement using laser interference, signal demodulation is a key technique, while Phase Generated Carrier (PGC) is one method of signal demodulation technique with high sensitivity, which is suitable for digital demodulation. Recently, measurement technology through laser has been widely used, especially in the field of vibration measurement, acceleration measurement and measurement of underwater acoustic signal.The paper mainly introduces the the technology of demodulating weak signals, which contains two parts of hardware and software. In the first part, mainly realize the digital processing of weak modulated signal derived of laser interferometer, and transmit the data to the computer through USB interface. The algorithm of signal demodulation of PGC is accomplished in the second part, and a real time controlling interface is developed in the environment of VC++6.0, which can display and store the demodulation signal. The detail of this paper includes:1. Research the principle of PGC demodulation algorithm, analyze the setting of every parameter during the process of signal demodulation.2. Design the signal collection circuit based on the chip of ADS8323 and USB circuit with high transmission speed.3. Optimize the PGC algorithm employed multithread technique of VC++ under the development platform VC++6.0, and achieve the goal of real time display and storage of signal demodulation.