Optical recording medium with two superimposed layers, and corresponding recording device and method of reproduction

摘要

The optical recording medium comprises two recording layers, the second (N2) being superposed on top of the first (N1). Means for reading the two beams using the same optical beam, but using different principles are provided. Reading of the first layer is based on phase modulation of the signal, while reading of the second layer is based on intensity modulation of the optical beam. The two layers are illuminated by a laser beam (54) and means for reading the layers (56, 58, 60-1, 60-2) receive the light reflected by the two layers. The means for reading the signals comprises two or more photo-receivers, with a first channel (60-1) capable of calculating the difference of the photo-receivers (Sd) and a second channel (60-2) for calculating the sum (Ss) of the two signals.