MULTI-LAYER INFORMATION RECORDING MEDIUM HAVING PLANARITY EQUAL TO SINGLE LAYER, AND DATA RECORDING/REPRODUCING APPARATUS CAPABLE OF ENABLING RAPID REPRODUCTION IN SPITE OF USING OBJECT LENS WITH NUMERICAL APERTURE LARGER THAN 0.8

摘要

PURPOSE: A multi-layer information recording medium and a data record and regeneration apparatus are provided to record or reproduce data on or from a recording layer having two or more layers compatible with a single layer disc. CONSTITUTION: The multi-layer information recording medium, which can regenerate or record data, is compatible with a single one. The multi-layer information recording medium comprises the first recording layer and the second recording layer. The first and the second recording layer are formed sequentially from a beam incidence side. The cover layer has a predetermined refraction index(n) at a beam incidence side, and a predetermined thickness(t). The second recording layer is positioned at one optical distance(d) from the beam incidence side where d = n x t. The compatibility between the multi-layer information recording medium and the single-layer information recording medium is based on a disc diameter, an overall disc thickness and a track pitch.