A VERSATILE LASER-BEAM DEFLECTION SENSOR UTILIZING OPTICAL FIBERS

A compact, fast (tau almost-equal-to 10 ns) and sensitive (delta almos t-equal-to 0.1 murad) laser beam deflection sensor has been developed. The device consists of a passive fiber optic sensor head and a separa te detector and amplifier unit. Subsequent signal processing is perfor med using a fast digital storage oscilloscope. The sensor head can be adjusted according to the probe beam spot size to optimize the deflect ion measurement sensitivity. The passive sensor head having no electri cal components makes the system especially suitable for applications w here rf noise pickup may constitute a problem. A differential operatin g principle is utilized to reduce common-mode noise such as probe lase r intensity fluctuations. The possibilities of high-pass filtering and averaging of the deflection signal to enhance the measurement sensiti vity are discussed.