Complementary two-dimensional laser Doppler velocimeter with an optical fiber probe

Abstract

Optical probing and interferometric sensing techniques have great advantages of non-loading, high resolution and wide dynamic range for motion measurement of a solid object. For this purpose, laser Doppler velocimeter (LDV) is widely utilized. However, optical measurement of two dimensional (2D) motion is a hard problem for a conventional LDV, because the instrument has a big frame size and heavy wight, and requires stable measurement environment such as an optical bench or a rigid base. In this paper, we discuss a newly proposed 2D LDV with a compact remote sensing probe. Laser light is bidirectionally transmitted via two optical fibers from a base unit to the probe head. The system is designed to measure a specific solid object that moves in 2D plane such as an optical pickup head equipped in an optical data storage system. As testing of the system, 1D displacement, velocity and acceleration of a moving membrane of a loudspeaker and 2D motion of a moving optical pickup actuator were successfully measured.