Optical readout system for magnetic recording - uses linearly polarised beam directed through recording medium with polarisation plane changed by magnetisation

摘要

The optical read-out system is used for information recorded magnetically on a tape or disc. It employs a linearly polarised light beam, directed through the recording tape etc. so that the polarisation plane is rotated in dependence on the magnetisation. The read-out system has a light source (1, 2) providing the linearly polarised beam and an electro-optical modulator (3) supplied with a signal of given frequency. The tape is moved relative to the beam such that its magnetisation vector has a component along the optical axis of the beam. An analyser prism (7) receives the modulated beam and is followed by a photodetector (8) supplying a signal to a phase detector (12) also receiving the signal supplied to the electro-optical modulator (3).