laser intensity modulation direct overwrite (MO) (LIMDOW)
Limdow drives are a further development of the well-known MO drives, which speed up the writing of Limdow MO discs considerably compared to normal MO drives.
The normal MO disc needs two passes for writing: The first pass erases the data, and the second pass rewrites the MO disc. Limdow drives, on the other hand, require only one pass, which speeds up writing.
Limdow drives operate without magnetic heads, but with special media. The opposing magnetic fields are generated by an external magnetic field in the drive and by the magnetic field of the initialization layer. These interact with the magnetic fields of the different layers, which are activated to different degrees by the intensity of the laser beam, the different materials and the magnetic field influence. The individual layers of the Limdow disk all have elementary magnets and differ only in the temperature at which the magnets can be reversed. At the lowest layer, the initialization layer, the so-called Curie point is highest and must not be reached, so that the orientation of the elementary magnets does not change.
To be able to read and write normal MO discs, Limdow drives have magnetic heads. Data transfer rates range from 3.5 MB/s to 6 MB/s for reading and from 1.7 MB/s to 3.6 MB/s for writing, and have an average positioning time of about 20 ms. The Limdow disks have storage capacities of 640 megabytes (MB) to 2.6 gigabytes( GB).