Signal playback system transducer with optical resonance cavity

A pickup system for playing back signals stored on the surface of a carrier in a form providing an optically detectable property which varies as a function of the time pattern of the stored signals, the storage being constituted by undulations or variations in the reflectivity of the carrier surface and the pickup system employing a laser beam which is reflected in a manner controlled by the stored information. The system includes a laser radiation generating element forming part of an optical resonator which also includes the carrier surface so that the intensity of radiation oscillations in the resonator is influenced by the surface and varies as the carrier moves relative to the laser element. The system also includes an output member for converting such intensity variations into an electrical signal representative of the stored signals.