Vibration frequency measurement using a local multithreshold technique

Belen Ferrer,D Mas,Ana B Roig,J Perez,Julian Espinosa

doi:10.1364/oe.21.026198

Abstract

In this paper, we demonstrate the use of a video camera for measuring the frequency of small-amplitude vibration movements. The method is based on image acquisition and multilevel thresholding and it only requires a video camera with high enough acquisition rate, not being necessary the use of targets or auxiliary laser beams. Our proposal is accurate and robust. We demonstrate the technique with a pocket camera recording low-resolution videos with AVI-JPEG compression and measuring different objects that vibrate in parallel or perpendicular direction to the optical sensor. Despite the low resolution and the noise, we are able to measure the main vibration modes of a tuning fork, a loudspeaker and a bridge. Results are successfully compared with design parameters and measurements with alternative devices.

Highlights

In this paper, we demonstrate the use of a video camera for measuring the frequency of small-amplitude vibration movements
The method is based on image acquisition and multilevel thresholding and it only requires a video camera with high enough acquisition rate, not being necessary the use of targets or auxiliary laser beams
Vibration measurement and analysis is an important topic in many scientific fields, like structural engineering, acoustics, biotechnology, entertainment devices, security and surveillance

Summary

Introduction

Vibration measurement and analysis is an important topic in many scientific fields, like structural engineering, acoustics, biotechnology, entertainment devices, security and surveillance. There exist different methods for measuring vibrations, accelerometers are usually preferred. These devices register the local acceleration of the specific point of the specimen where they are attached. The device collects the light scattered from it and, it is interfered with a reference beam. They provide very accurate result, their measuring distance may remain short due to attenuation. They result really expensive and no-cost effective for many applications [2]

Methods

Results

Conclusion