OPTICAL DISC AND OPTICAL DISC REPRODUCTION DEVICE

摘要

In the conventional super-resolution reproduction method, an optical spot size is changed by power of the laser beam applied to an optical disc and accordingly, it is necessary to decide an optimal laser power for super-resolution reproduction for each of the recording pattern sizes. The present invention provides an optical disc formed by a recording layer and a material layer having changing viscosity. When a laser beam is applied for reproducing information recorded in the recording layer, a part of a crystalline thin film of the material layer having changing viscosity is softened. The optical constant of the softened part is changed and a discontinuous plane of the optical constant is generated at the boundary of the softened part so as to form a ring-shaped peculiar region in the optical spot. By this ring-shaped peculiar region, it is possible to reproduce a recording pattern of size smaller than the resolution limit with a signal intensity equivalent to the recording pattern of a greater size.