<title>Optical Disc Memory System</title>

Abstract

The video and the audio disc systems have been realized and the progress of optical disc memory systems allows the new products such as the video file system and the document file system. The optical disc memory system has a number of advantages compared with the current magnetic disc memory. These are the large recording capacity, the high recording density (10 to 100 times more than ordinary magnetic disc) and the contact free record and retrieval of the information, which eliminates the "Head Crush" problems and realizes the reliable information storage system. However, high recording density and small track pitches (usually 1.6--2.5 micron meters) increases the probability of error rate of recording infomation. Bit error rate (BER) of the recorded optical disc sometimes presents 10-4-10-5 Which is much higher than the magnetic disc. This high BER strongly depends on the production process. Optical disc is preformatted with the address information and with the tracks for infor-mation recording. The pregrooved disc used to be produced by the optical mastering process and the U-V replication process, which needs the very high-grade clean room and the expensive facilities. Process control of the laser cutting on the resist coated glass master is quite sensitive and must be treated with extreme care. When the large quantity of mass produced optical memory discs is supplied, a new mastering process would be needed. One of the solutions of this problem is the dry mastering process with a mechanical cutting system.