An approach of readout aperture control for magnetic super-resolution (MSR)
readout is described. In order to detect the size of a readout aperture ge
nerated by a focused laser beam on an MSR disk, a new mark pattern consisti
ng of short and long marks was recorded. An amplitude ratio of the readout
signals between the short and the long marks is proportional to the apertur
e size. By maintaining the ratio constant by adjusting the laser power, the
aperture size can be fixed. This technique makes it possible to reproduce
data with a low bit error rate (BER). The sensitivity of the ratio to the r
eadout power deviation and the distribution of the ratio were evaluated in
order to estimate the accuracy of the readout power control. This technique
is also applicable to readout when the disk is tilted. When the aperture s
ize was maintained by this method, BER was found to be substantially reduce
d. Consequently, this new technique can realize high density recording on t
he MSR disk, This is the first approach to readout aperture control based o
n controlling the laser power.