Magnetic field modulation recording with multipulse laser irradiation on magnetooptical disk drive

Abstract

A magnetooptical disk driver which adopts the magnetic field modulation recording scheme has been developed for filing data. to apply the magnetic field modulation magnetooptical file system, such as a minidisk, to personal computers, essential technology must be developed. A noncontact magnetic head type and active spacing system were adopted to achieve high reliability and accessibility. To avoid system disturbance due to the weight increase in the head, linear motors were used to achieve independent motion of the optical head and magnetic head. A sputter-etching treated magnetooptical disk was developed as the magnetic field modulation medium for low-field recording. to cope with low-field noise during magnetic field modulation recording, multipulse laser irradiation was used. In this method, the magnetized segment had a sharp edge even when the magnetic field was weak, resulting in a reduction of jitter in the playback of the signal. Using the foregoing technologies, a test driver for recording and playback using the compact disk (CD) format was evaluated. In the test, the jitter value was less than 20 ns and the block error rate was on the order of 10−4.