OPTICAL DISK

PURPOSE:To simplify the control mechanism of an optical head and to increase the range of application with an optical disk, by using an additional record band having no erasing function and a rewritable record band to form a recording medium and using in common a record/reproduction/erasion means. CONSTITUTION:Two recording media 2 and 3 are provided on a substrate 4, and the pulse laser light is irradiated on an additional recording medium 2 having no erasing function. Then signals are written with variations of reflection factor as well as the heating/rapid cooling. The laser light is irradiated to a rewritable record band 3, and signals are recorded and reproduced with the reversible variations of the reflection factor due to the heating/rapid cooling and heating/slow cooling. The record band 2 excels in the weather resistance and can preserve signals for a long period of time. This facilitates easy recording by separating the undesired information in a short time. Furthermore a control mechanism is simplified together with increase of this application range since a light source and an optical head can be used in common for record, reproduction and erasion.