Approach to readout aperture control for magnetic super-resolution readout

An approach of readout aperture control for magnetic super-resolution (MSR) readout is described. In order to detect the size of a readout aperture generated by a focused laser beam on an MSR disk, a new mark pattern consisting 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 aperture 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 readout 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 size was maintained by this method, BER was found to be substantially reduced. Consequently, this new technique can realize high density recording on the MSR disk. This is the first approach to readout aperture control based on controlling the laser power.