MO media noise studies by readout beam scanning

The spectral distribution of media noise in magnetooptic (MO) disks is discussed. The spatial impulse response of the readback system has been computed by scanning a spot across a straight-line MO feature transverse to an otherwise featureless track. An alternative calculation involved scanning the beam over 2-D sinusoidal and checkerboard MO patterns of variable wavelength. The impulse response was combined with the measured spectral content of wide, noisy, self-demagnetized written tracks on MO media to infer characteristics of the spatial frequency distribution of media noise. Particular emphasis was placed on determining the extent to which the media spatial frequency distribution is white, or equivalently, whether particular correlation lengths are dominant. It was found that media noise induced in thermomagnetic writing or periodic data patterns has a spectral shape that is independent of the frequency of the written pattern, but with a noise power that is proportional to the pattern frequency