OPTICAL INFORMATION RECORDING AND REPRODUCING METHOD

摘要

PURPOSE:To perform tracking of laser spot light and information recording and reproduction by providing a region having at least 3 kinds of optical constant values to a thin recording film layer. CONSTITUTION:Multi-layered films are formed on a flat substrate 1. The 1st layer 2 is a layer contg., for example, tellurium Te and the layer 3 is similarly the layer contg. tellurium. The compsn. of the additive material is so selected that the coefft. of light absorption is smaller in the layer 2 than in the layer 3. The multi-layered films are uniformly melted and mixed to form the tracks in the state of the recording layer 4 when such layers are heated up to the m.p. or above by continuously irradiating the laser spot light to said layers. The optical path length nd is longest when the tracks contain the tellurium entailing crystallization. Information dots which can be made amorphous are formed and the optical path length in this part is smallest if the tracks are subjected to light irradiation of the short pulse width. The tracking of the laser light spot is made possible by the difference in the optical path length from the part not irradiated with the laser light even with the tracks already recorded with the information dots. The erasure of the information entailing crystallization is executed.