Electro-optical probe for oscilloscope measuring signal waveform

Abstract

An electro-optical probe used for an oscilloscope (e.g., electro-optic sampling oscilloscope) is mainly constructed by a probe head and a probe unit. The probe head contains a metal pin and an electro-optical element having a reflector at its terminal surface. The probe unit contains a reduced number of optical parts, which are arranged such that an optical axis of incoming beams of the electro-optical element differs from a optical axis of outgoing beams of the electro-optical element. That is, laser beams output form a laser diode are subjected to convergence by a converging lens to produce converged beams, which are incident on the electro-optical element as its incoming beams. The incoming beams are subjected to reflection by the reflector to produce reflected beams, which are output from the electro-optical element as its outgoing beams. Then, the reflected beams are converted to parallel beams by a collimator lens, or they are converged by a converging lens. A polarization detector performs separation on input beams from the lens to produce separated components of beams, optical axes of which differ from each other. Those components of beams are respectively supplied to photodiodes, wherein they are converted to electric signals. Thus, it is possible to measure a waveform of a measured signal based on differences between the electric signals, which reflect changes of polarization states of the beams in the electro-optical element.