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AssigneeCommissariat a l'Energie Atomique
InventorsFabien Laulagnet, Marie-Françoise Armand, Alain Fargeix, Bérangère Hyot
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The invention relates to the field of the optical recording of information on a medium, such as an optical disc. To read an optical disc in super-resolution mode, a procedure for optimizing the power of the read laser beam is implemented. This optimization is based on the observation that a correlation exists between the power allowing the disc to be read without risk in super-resolution mode and the amplitude of the read signal which results from the reading of marks having the smallest possible dimension (marks 2 T). The amplitude of the optical disc is measured for several powers of decreasing values of the read laser, the reduction in amplitude is observed. A read power is selected as a function of the power for which a decrease (for example 5%) is noted in the amplitude measured at the start.
An optical disc reader operating in super-resolution mode and comprising a read laser, suitable for reading optical discs having a structure comprising a substrate provided with physical marks, the geometrical configuration of which defines the recorded information, a superposition of three layers above the marks of the substrate, and a transparent protective layer above this superposition, the superposition comprising an indium antimonide or gallium antimonide layer inserted between two dielectric layers of a zinc sulphide-silicon oxide (ZnS—SiO2) compound,
A method of reading an optical disc by means of a read laser operating in super-resolution mode, suitable for reading optical discs having a structure comprising a substrate provided with physical marks, the geometrical configuration of which defines the recorded information, a superposition of three layers above the marks of the substrate, and a transparent protective layer above this superposition, the superposition comprising an indium antimonide or gallium antimonide layer inserted between two dielectric layers of a zinc sulphide-silicon oxide compound wherein the amplitude of the signals resulting from reading a series of marks having the smallest possible size is measured for several different power levels on the basis of a predetermined maximum power level, a curve of amplitude variation and a read power Pa for which the amplitude drops below a value k1.A0 are determined, where A0 is the amplitude of the first measured power level or the average amplitude of the first measured power levels and k1 is a coefficient which is less than 1 and is preferably between 0.85 and 0.95, the measurements are stopped for this power Pa and then, to read the information on the optical disc, a read power PL equal to k.Pa, k being a coefficient greater than or equal to 1, is applied to the laser.
Dependencies are inferred from the claim text.