Information recording medium having a wobbling groove structure
View Patent ↗An information recording medium having at least a read only area and a recording and reproducing area is composed of at least: a substrate; a recording layer formed on the substrate so as to record and reproduce information; and a light transmission layer having transparency formed on the recording layer. The information recording medium is further characterized in that a wobbling groove corresponding to the read only area and another wobbling groove corresponding to the recording and reproducing area is formed on the substrate without overlapping with each other, the recording and light transmitting layers are continuously adhered over at least two areas of the read only area and the recording and reproducing area, reflectivity of the recording layer is more than 5%, and a push-pull signal output T 3 reproduced from the read only area and another push-pull signal output T 4 reproduced from the recording and reproducing area before recording satisfies relations of T 3 ≧0.1, T 4 ≧0.1 and 1.5≧T 3 /T 4 ≧0.5.
1. An information recording medium comprising at least:
a substrate;
a first recording layer formed on the substrate so as to reproduce information;
a first light transmitting layer having transparency formed on the first recording layer;
a second recording layer formed on the first light transmitting layer so as to reproduce information; and
a second light transmitting layer having transparency formed on the second recording layer,
the information recording medium further comprising:
a wobbling track of which a track pitch is P 3 corresponding to a first reproducing area and being disposed in an inner circumference side of the information recording medium; and
another wobbling track of which a track pitch is P 4 corresponding to a second reproducing area and being disposed in an outer circumference side of the information recording medium,
wherein the wobbling track and the other wobbling track are formed on the substrate without overlapping each other, and
wherein the first and second recording layers and the first and second light transmitting layers are continuously adhered over at least two areas of the first reproducing area and the second reproducing area respectively, and
wherein a push-pull signal output T 3 reproduced from the first reproducing area and another push-pull signal output T 4 reproduced from the second reproducing area satisfies relations of T 3 ≧0.1, T 4 ≧0.1 and 1.5≧T 3 /T 4 ≧0.5, and
wherein a wavelength of a reproducing light beam is λ and a numerical aperture of an objective lens for reproducing is NA, and
further wherein P 3 , P 4 , λ and NA satisfy relations of P 3 ≦λ/NA, P 4 ≧λ/NA and P 3 >P 4 .
2. A reproducing method of an information recording medium,
the information recording medium comprising at least:
a substrate; a first recording layer formed on the substrate so as to reproduce information;
a first light transmitting layer having transparency formed on the first recording layer;
a second recording layer formed on the first light transmitting layer so as to reproduce information;
a second light transmitting layer having transparency formed on the second recording layer;
a wobbling track of which a track pitch is P 3 corresponding to a first reproducing area and being disposed in an inner circumference side of the information recording medium; and
another wobbling track of which a track pitch is P 4 corresponding to a second reproducing area and being disposed in an outer circumference side of the information recording medium,
wherein the wobbling track and the other wobbling track are formed on the substrate without overlapping each other, and
wherein the first and second recording layers and the first and second light transmitting layers are continuously adhered over at least two areas of the first reproducing area and the second reproducing area respectively, and
wherein a push-pull signal output T 3 reproduced from the first reproducing area and another push-pull signal output T 4 reproduced from the second reproducing area satisfies relations of T 3 ≧0.1, T 4 ≧0.1 and 1.5≧T 3 /T 4 ≧0.5, and
wherein a wavelength of a reproducing light beam is λ and a numerical aperture of an objective lens for reproducing is NA, and
further wherein P 3 , P 4 , λ and NA satisfy relations of P 3 ≦λ/NA, P 4 ≦λ/NA and P 3 >P 4 ,
the reproducing method comprising the steps of:
reading the first reproducing area to reproduce the push-pull signal output T 3 ; and
reading the second reproducing area to reproduce the other push-pull signal output T 4 ,
wherein the step of reading the second reproducing area follows the step of reading the first reproducing area in succession.