Analysis of a Magneto-Optic Readout System

The signal and the signal-to-noise ratio in a typical magneto-optic readout scheme intended for use in a high-capacity high-speed memory were analyzed. It was found that such a system does not yield higher signal levels and signal-to-noise ratios than are available with conventional magnetic head readout in such a peripheral memory. Calculations show that for 10-3-inch diameter bits recorded on an iron film in a system using an Osram XBO 150 high-pressure Xenon lamp, the signal-to-noise ratio at a megacycle transfer rate is in the neighborhood of 1. The maximum signal has about 300 photoelectrons per bit at the photocathode. It was concluded that although a magneto-optic system is impractical for such application, it may still be used in some display devices or in a medium-speed, medium-density fast access memory.