Swept-Source Optical Coherence Vibrometer: Principle and Applications

Abstract

Optical coherence vibrometer (OCV) is an optical vibration measurement technology which presents the advantages of noncontact, high precision, and large dynamic measurement range. The OCV equipment and the related theories are proposed to avoid excessive demands in monochromaticity and stability of the laser source. The performance of laser Doppler vibrometer (LDV) is complemented by OCV with low cost. In order to obtain large dynamic measurement range (i.e., from nanometer scale to centimeter scale), the differential effect from multiwavelength components is used to break the phase limit of laser interference. However, due to the interference blurry effect, its high-velocity measurement performance is limited. To solve this problem, a novel optical vibrometer with a high-speed measuring capability called swept-source OCV (SSOCV) was proposed. In SSOCV, both a swept-laser source and single-point photodetector were employed to replace the conventional superluminescent diode and spectrometer. These two units help the SSOCV to divide the full bandwidth interference signal into single-wavelength signals, which are subsequently collected by the photodetector. Therefore, the exposure time of interferometric signal was reduced and the measuring speed was highly improved. Taking advantage of these features, our SSOCV can be applied in many different fields particularly in highly accurate measurements applications such as the displacement, mechanical vibration, as well as acoustic and ultrasonic vibration among others.