A VERSATILE LASER-BEAM DEFLECTION SENSOR UTILIZING OPTICAL FIBERS

A compact, fast (tau almost-equal-to 10 ns) and sensitive (delta almost-equal-to 0.1 murad) laser beam deflection sensor has been developed. The device consists of a passive fiber optic sensor head and a separate detector and amplifier unit. Subsequent signal processing is performed using a fast digital storage oscilloscope. The sensor head can be adjusted according to the probe beam spot size to optimize the deflection measurement sensitivity. The passive sensor head having no electrical components makes the system especially suitable for applications where rf noise pickup may constitute a problem. A differential operating principle is utilized to reduce common-mode noise such as probe laser intensity fluctuations. The possibilities of high-pass filtering and averaging of the deflection signal to enhance the measurement sensitivity are discussed.