Abstract: In an optical device, a number of structures having higher portions or lower portions are arranged at a fine pitch equal to or shorter than a wavelength of visible light on a surface of a base. Each of the structures is arranged to form a plurality of arc track rows on the surface of the base, and to form a quasi-hexagonal lattice pattern, and the structure has an elliptical cone or truncated elliptical cone shape having a major axis in a circumferential direction of the arc tracks.

Abstract: In an optical device, a number of structures having higher portions or lower portions are arranged at a fine pitch equal to or shorter than a wavelength of visible light on a surface of a base. Each of the structures is arranged to form a plurality of arc track rows on the surface of the base, and to form a quasi-hexagonal lattice pattern, and the structure has an elliptical cone or truncated elliptical cone shape having a major axis in a circumferential direction of the arc tracks.

Abstract: In an optical device, a number of structures having higher portions or lower portions are arranged at a fine pitch equal to or shorter than a wavelength of visible light on a surface of a base. Each of the structures is arranged to form a plurality of arc track rows on the surface of the base, and to form a quasi-hexagonal lattice pattern, and the structure has an elliptical cone or truncated elliptical cone shape having a major axis in a circumferential direction of the arc tracks.

Abstract: In an optical device, a number of structures having higher portions or lower portions are arranged at a fine pitch equal to or shorter than a wavelength of visible light on a surface of a base. Each of the structures is arranged to form a plurality of arc track rows on the surface of the base, and to form a quasi-hexagonal lattice pattern, and the structure has an elliptical cone or truncated elliptical cone shape having a major axis in a circumferential direction of the arc tracks.

Abstract: The stable reproduction of wobble signal without generating beats despite of an improvement in recording density by narrowing a track pitch is realized. Data by magnetooptical recording is recorded on wobbling grooves and lands between adjacent wobbling grooves. The wobbling grooves are provided to wobble both sides of the grooves in different amplitudes. Further, both the sides wobbled in different amplitudes are wobbled in phase in the track direction. These different amplitudes of both sides are preferably set to 3.3 to 40%.

Abstract: In an optical disk, address information, including an address information start mark, is recorded in a header region primarily based on variable-length codes such that, between each pair of nearest bits having a first logic value, at least two and at most seven bits having a second logic value are disposed. The address information start mark is detected based on a first criterion that a combination of pulse widths each defined in association with a nearest pair of bits having the first logic value is present in a pulse sequence, and also based on a second criterion that, when the logic level of the pulse sequence alternates between a first logic level and a second logic level in association with occurrence of bits having the first logic value intermittently disposed among bits having the second logic value, the logic levels of pulses in the pulse sequence coincide with their respective counterparts in the combination of pulse widths.

Abstract: The stable reproduction of wobble signal without generating beats despite of an improvement in recording density by narrowing a track pitch is realized. Data by magnetooptical recording is recorded on wobbling grooves (71) and lands (72) between adjacent wobbling grooves (71). The wobbling grooves (71) are provided to wobble both sides of the grooves in different amplitudes. Further, both the sides wobbled in different amplitudes are wobbled in phase in the track direction. These different amplitudes of both sides are preferably set to 3.3 to 40%.

Abstract: In an optical disk, address information, including an address information start mark, is recorded in a header region primarily based on variable-length codes such that, between each pair of nearest bits having a first logic value, at least two and at most seven bits having a second logic value are disposed. The address information start mark is detected based on a first criterion that a combination of pulse widths each defined in association with a nearest pair of bits having the first logic value is present in a pulse sequence, and also based on a second criterion that, when the logic level of the pulse sequence alternates between a first logic level and a second logic level in association with occurrence of bits having the first logic value intermittently disposed among bits having the second logic value, the logic levels of pulses in the pulse sequence coincide with their respective counterparts in the combination of pulse widths.