System and method for simultaneously verifying optical data writing and

Abstract

The optical disk writing system disclosed is one in which data written on an optical data writing medium is verified essentially simultaneously with writing on the medium. The written data is verified by detecting a timing of the light irradiated on the medium and by measuring return light doses at rise and fall of the light irradiated on the medium and comparing the doses thereof with predetermined reference values. The medium uses a phase transition reversible between a crystal state and an amorphous state for writing/reading/erasing of data on a data writing film, and includes a first protective film, a phase transition type data writing film, a second protective film, and a reflection film, formed in this order, on a transparent substrate. The thickness of the first protective film is set such that, of three reflectivities of the data writing film respectively in crystal, amorphous and melted states, the reflectivity in the crystal state and the reflectivity in the melted state are made different from each other, and the reflectivity in the amorphous state and the reflectivity in the melted state are made different from each other. A high speed writing operation can be carried out and an overwrite operation can be completed in one disk rotation time.