Birefringent Servo for a Magneto-Optic Head
Original Publication Date: 1988-Feb-01
Included in the Prior Art Database: 2005-Feb-14
A pockels cell is used to increase the signal-to-noise ratio of a magneto-optic read signal. The pockels cell operates to cancel out the birefringent signal that may be present, such as may be caused by the protective plastic cover of a magneto-optic disk. Because magneto-optic memory devices operate on changes in the polarization of light, birefringence of the memory media (such as can be caused by the protective cover of a magneto optic disk) adds rotation and ellipticity to the polarization states of the reflected laser read beam. This birefringent signal is a low frequency signal, and is represented in Fig. 1 by curve 10. Fig. 1 shows the high frequency data signal 11 superimposed on the low frequency birefringent signal, and shows that the low frequency signal is typically of a larger magnitude than is the data signal.