ADAPTIVE PHOTODETECTORS FOR VIBRATION MONITORING

摘要

We report on simple high-sensitivity interferometric technique of detecting vibrations and present characteristics of laser vibrometer using GaAs and SnS_2 adaptive photodetectors based on the effect of the non-steady-state photoelectromotive force. It enables efficient direct conversion of high-frequency phase modulation of speckle-like optical wave reflected from the vibrating object into an output electrical signal with concomitant setting of optimal operation point of the interferometer and suppression of amplitude laser noise. The results of measurements of small vibration amplitudes of the mirror and diffusely scattering objects are presented. Preliminary studies at 1.06μm showed that it is possible to detect ultrasonic vibrations with the amplitude of 0.2 A with a signal power of 20 mW and a bandwidth of 15.5 MHz. This optical phase-to-electrical signal converter is not sensitive to ambient vibrations, thermal drift, amplitude laser noise and is therefore appropriated for industrial applications.