OPTICAL RECORD CARRIER

摘要

The recording surface of an optical record carrier (1) is divided into first (A) and second annular zones (B) which are situated concentrically around a centre of rotation (4). The annular zones (A) are provided with groups of radially aligned first control structures (13), whilst the annular zones (B) are provided with groups of radially aligned second control structures (14). An optical scanning device for optically scanning the structure of the information carrier (1) at the location of the scanning spot (54) projected on the record carrier by the scanning device comprises a detection circuit (70) which in the case of a radial movement of the scanning spot (54) detects first and second control structures (13; 14) and derives a measurement signal Vm which indicates the passage of the boundaries between the zones A and B during a radial movement of the scanning spot 54. The measurement signal Vm is very suitable for the control of a system for rapidly addressing the scanning spot 54 to one of the annular zones (A; B).