REAL-TIME VIBRATION MEASUREMENT USING A FEEDBACK TYPE OF LASER-DIODE INTERFEROMETER WITH AN OPTICAL-FIBER

A laser diode interferometer that uses an optical fiber is proposed. T he laser diode simultaneously functions as a light source, a phase mod ulator, and a phase compensator. Detection of the vibration and reduct ion of external disturbance are carried out using a feedback control f or the injection current of the laser diode. Thus it can measure vibra tion accurately in real time with a simple signal processing circuit. The optical fiber not only functions as a flexible probe, enabling us to measure the vibration of an object that cannot be moved onto the op tical bench, it also acts as a reference mirror, thereby simplifying t he unit construction. The principle of the feedback control in laser d iode interferometer is also described in detail. (C) 1997 society of P hoto-Optical Instrumentation Engineers.