Modulated magnetooptic readout system

Claim 1

Apparatus for improving the signal-to-noise ratio and thus the readout of a magneto-optic readout system which utilizes a removable magnetic recording medium for storing information in the form of selected states of magnetization, a beam of light adapted to impinge and scan said medium, and light receiving means disposed to receive the beam of light after same impinges the magnetic recording medium, the combination comprising: a composite region having magnetically coupled integrally disposed storage and readout portions of relatively high and low coercive force all-magnetic materials respectively, disposed to define in part said removable magnetic recording medium; said region having erasably recorded therein information In the form of selected alterable states of magnetization, wherein the selected alterable states of magnetization of said readout portion are determined only by the magnetically coupled storage portion; means operatively coupled to said medium for applying a temporary alternating interrogating external signal of a selected frequency superimposed upon a selected direct current signal to said medium to temporarily alter all the selected alterable states of magnetization in the readout potion of said region, said application of the interrogating external signal productive of temporarily modulating a component of the beam of impinging light to provide a distinctive component condition therein for each of the selected alterable states; said light receiving means including light detection means responsive to the beam of light from the medium to sense the distinctive component conditions of the beam of light and thus the temporarily altered states of magnetization of the medium.