Study On Reception Technology Of Laser Vibration Measurement

Laser heterodyne interferometer is a very useful technology for the vibration measurement. With the characteristics of non-contact measurement, high precision, wide measuring range, anti-electromagnetic interference, quick dynamic response, insensitive to transverse vibration,it has been one of the most valuable methods for vibration measurement. The Doppler frequency shift is proportioned to the frequency of the light wave.Because of the very high frequency of the light wave, the Doppler signal of the target vibration belongs to the broad-band FM signal.This leads to difficulty for demodulating the FM signal.The related theory about Laser heterodyne vibration measurement was discussed firstly in this paper. The Doppler effect and the basic principle of laser heterodyne vibration measurement were introduced. The way to demodulate laser Doppler echo signal is studied. Laser Doppler echo signal is analyzed and it is wideband signal. Besides, the demodulation device used in the experiment is analyzed and the process of modulation-demodulation is studied by the use of matlab simulation.In this paper, the optical heterodyne detection experiment of the vibration from a speaker with different frequencies was studied. Under certain conditions, vibration targets with single frequency is detected by the use of Laser heterodyne interferometer, so we can obtain the vibration spectrum with FFT ANALYZER. Then the vibration spectrum is compared with the audio spectrum which is obtained by recording equipment and FFT ANALYZER. With the same method, vibration of the speaker, which is actuated by nosie from radio, was detected as well as the speaker turned on without input. The results show that the system can detect target vibration and obtain vibration information effectively.