MULTI-LAYER INFORMATION STORAGE SYSTEM

摘要

An information storage system is described comprising an optical multi-layer record carrier (1) and a device (10) for scanning the layers (3, 4, 5) with a scanning spot (15) formed by a radiation beam (12). The radiation beam is compensated for spherical aberration for a single height of the scanning spot within the stack (2) of layers. The height of the stack is determined by the maximum spherical aberration admissible for the system. The number of layers in the stack is determined by the minimum distance between layers, which depends on the crosstalk on servo errorsignals due to currently unscanned layers.