Abstract: An information recording medium includes a substrate, and one or a plurality of layers formed on the substrate, wherein at least one of the layers is formed by mixing a base material and a hard material which has a predetermined thickness and determines a predetermined thickness of the layer.

Abstract: An optical information recording and reproducing apparatus is provided that is capable of preventing recorded data from being deleted by mistake under a recording operation mode, and, under a reproduction operation mode, is capable of highly accurately reproducing and reading information data in which crosstalk has been removed. Under the reproduction operation mode, a single laser beam is divided into a plurality of divided laser beams, and they are individually irradiated onto a recording medium. On the other hand, under the recording operation mode, the quantity of light of each divided laser beam other than one beam of all the divided beams is reduced lower than that of the one beam, and they are all irradiated onto the recording medium.

Abstract: A pickup device and an information recording/reproducing apparatus for reproducing information in which crosstalks have been suppressed without causing an erasure or the like of the information which has already been recorded on an information recording medium. The apparatus has a light source 1 for emitting first and second lights whose polarizing directions cross perpendicularly. The first and second lights are transmitted through a grating for merely transmitting the first light and diffracting the second light at a predetermined diffraction efficiency and those lights are converged by an objective lens, thereby forming a laser beam and irradiating it onto an optical disc. At the time of the recording of information, the second light is set to a light-off mode or a low power state and the recording of information is performed by the laser beam caused by the first light.

Abstract: An asymmetry detection apparatus includes: a clock signal generator for generating a clock signal based on a reproduced signal; an A/D converter for sampling the reproduced signal in synchronization with the clock signal; a determiner for determining whether a level of each of a plurality of sampled data obtained by the sampling operation is equal to or greater than a predetermined level; and a detector for detecting asymmetry in the reproduced signal by using predetermined ones of the sampled data based on an output from the determiner.

Abstract: There is provided a phase-change type optical recording medium, including: a substrate; a recording layer formed on the substrate, phase condition of the recording layer being changed when a laser beam is radiated thereonto, to thereby record, erase or reproduce data into or from the recording layer; and a reflection layer formed on the recording layer for reflecting a laser beam having been radiated onto the recording layer. The recording layer is formed so that the following equation is established: Rc>Rm>Ra wherein Rc indicates a reflectivity to be obtained when the recording layer is in crystal condition, Ra indicates a reflectivity to be obtained when the recording layer is in amorphous condition, and Rm indicates a reflectivity to be obtained when the recording layer is in mixed condition of molten condition and crystal or amorphous condition.

Abstract: An optical disc has a plurality of tracks for recording information represented as marks and spaces between the marks. The marks are formed by an optical beam modulated by a plurality of drive pulses (202) where a number of the drive pulses is determined according to a length of a mark part in the original signal to be recorded to the track. The optical disc has a control information recording area (2504) for storing a first pulse position Tu value indicative of rising edge of the first drive pulse for determining a start position of a mark to be recorded, and a last pulse position Td value indicative of falling edge of the last drive pulse for determining an end position of a mark to be recorded.

Abstract: A writable optical disc has an information writing track, and a guiding track for introducing a laser beam to the information writing track. The guiding track has prepit information recorded thereon, the prepit information including at least address information of the optical disc. The prepit information is recorded on the guiding track at a position where interference of adjacent guiding tracks with the prepit information is prevented. The information writing track is a groove track, and the guiding track is a land track.