Abstract: In a device for controlling a focus to an optical disc having a land section and a groove section, the control is performed so as to avoid a focus step difference at a land-area/groove-area switching point. When performing write-in or readout of data to an optical disc on which a land area and a groove area are continuously formed, using an optical pickup, there are provided a land learning unit (1) for determining a focus position in the land area, a groove learning unit (2) for determining a focus position in the groove area, and a focus position calculation unit (3) for determining a focus position in an area where the land area and the groove area are switched, and the focus position of the optical pickup is moved so that it is located at the third focus position when the switching signal is inverted according to the switching between the land area and the groove area.

Abstract: In a device for controlling a focus to an optical disc having a land section and a groove section, the control is performed so as to avoid a focus step difference at a land-area/groove-area switching point. When performing write-in or readout of data to an optical disc on which a land area and a groove area are continuously formed, using an optical pickup, there are provided a land learning unit (1) for determining a focus position in the land area, a groove learning unit (2) for determining a focus position in the groove area, and a focus position calculation unit (3) for determining a focus position in an area where the land area and the groove area are switched, and the focus position of the optical pickup is moved so that it is located at the third focus position when the switching signal is inverted according to the switching between the land area and the groove area.

Abstract: An epoxy resin composition, which comprises, as an essential component, a phosphorus compound having an average of not less than 1.8 and less than 3 of phenolic hydroxy groups reactive with an epoxy resin and an average of not less than 0.8 of a phosphorus element in the molecule, an inorganic filler having an average particle diameter of not greater than 30 &mgr;m, a bifunctional epoxy resin having an average of not less than 1.8 and less than 2.6 of epoxy groups in the molecule and a hardener, wherein the bifunctional epoxy resin is contained at an amount of not less than 51% by mass relative to the whole epoxy resin, at least one of dicyandiamide and a polyfunctional phenol system compound having an average of not less than 3 of phenolic hydroxy groups in the molecule is used as the hardener and a ratio (a/c) of equivalent (a) of a phenolic hydroxy group of the phosphorus compound and equivalent (c) of an epoxy group of the bifunctional epoxy resin is not less than 0.3 and less than 0.

Abstract: An apparatus of the present invention is an optical disk apparatus for irradiating with a laser beam an optical disk on which address marks are recorded at intervals based on a pulse width modulation method and for reproducing data from a reproduced signal based on reflected light. The apparatus includes: a pulse signal reproduction section for producing a reproduced pulse signal from the reproduced signal based on a threshold value; a threshold value production section for producing the threshold value based on the reproduced pulse signal; and a gate signal production section for producing an address gate signal at a timing when the address mark is reproduced.

Abstract: An apparatus of the present invention is an optical disk apparatus for irradiating with a laser beam an optical disk on which address marks are recorded at intervals based on a pulse width modulation method and for reproducing data from a reproduced signal based on reflected light. The apparatus includes: a pulse signal reproduction section for producing a reproduced pulse signal from the reproduced signal based on a threshold value; a threshold value production section for producing the threshold value based on the reproduced pulse signal; and a gate signal production section for producing an address gate signal at a timing when the address mark is reproduced.