Abstract: There is provided a disk drive unit which is capable of making control corresponding to contaminant and defect by discriminating the contaminant (dust, scratch) on the disk surface from the defect on the recording plane. In a pull-in signal PI corresponding to reflected light from a disk, a defect detecting signal corresponding to a signal whose level change is relatively quick corresponding to the defect of the recording plane and a contaminant detecting signal which corresponds to a signal whose level change is relatively slow corresponding to the contaminant on the disk surface are generated. When the defect detecting signal is at low level for example, a system controller retries a recording operation or increases laser light when the contaminant detecting signal is at low level. A quantity of output light of a laser diode is controlled so that a product of output light of a laser diode and reflected light from the disk amounts to a predetermined level.

Abstract: A polypropylene resin composition is herein disclosed which is obtainable by blending (A) 100 parts by weight of a polypropylene resin comprising (a) 100 to 20% by weight of a homopolymer of propylene and/or a propylene copolymer containing 4% by weight or less of another olefin unit in which in a pentad fraction by .sup.13 C-NMR, [rrrr/(1-mmmm)].times.100 is in the range of 20 to 60%, a Tm measured by a DSC is 150.degree. C. or more, and a melt enthalpy is 100 J/g or less, and (b) 0 to 80% by weight of a propylene copolymer containing 10 to 80% by weight of an olefin unit other than propylene, with (B.) 0.01 to 5 parts by weight of an octyltin salt of a fatty acid, an alkylenebisfatty acid amide, a fatty acid ester of a polyvalent alcohol, or a metal salt of an aliphatic monocarboxylic acid.

Abstract: The present invention relates to an information recording/reproducing apparatus that radiates a laser beam to an information recording medium for recording and/or reproducing information, comprising: a laser beam generating means for generating a laser beam that records information to or reproduces information from the information recording medium; a timing control means for controlling information recording timing so that a recording area on a track of the information recording medium is followed by another recording area in a partially overlapping manner; and a laser beam intensity control means for controlling an intensity of the laser beam generated by the laser beam generating means so that a first area with information recorded, a second area with information erased, and a third area with information neither recorded nor erased are formed in the recording area in which information is at least recorded in an overlapping manner.

Abstract: A polypropylene resin composition is herein disclosed which is obtainable by blending (A) 100 parts by weight of a polypropylene resin comprising (a) 100 to 20% by weight of a homopolymer of propylene and/or a propylene copolymer containing 4% by weight or less of another olefin unit in which in a pentad fraction by .sup.13 C-NMR, ?rrrr/(1-mmmm)!.times.100 is in the range of 20 to 60%, a Tm measured by a DSC is 150.degree. C. or more, and a melt enthalpy is 100 J/g or less, and (b) 0 to 80% by weight of a propylene copolymer containing 10 to 80% by weight of an olefin unit other than propylene, with (B) 0.01 to 5 parts by weight of an octyltin salt of a fatty acid, an alkylenebisfatty acid amide, a fatty acid ester of a polyvalent alcohol, or a metal salt of an aliphatic monocarboxylic acid.

Abstract: A magnetic head applies a magnetic field to a desired area when recording an information signal on the desired recording area of a magneto-optical disk. This magnetic head comprises a printed circuit board and a coil formed on at least one of the surfaces of the printed circuit board by a conductor pattern. This magnetic head can be made smaller, lighter and thinner than conventional magnetic heads.

Abstract: In an optical disk apparatus for recording and/or reproducing a predetermined data on/from a disk recording medium rotated by constant linear velocity (CLV) system, at seek operation for moving the optical pickup to the target position of the disk recording medium, the rotational speed of the rotational driving means is controlled based on the first rotational speed signal of rotational driving means first, and when it is detected by the output of position detecting means that the optical pickup moves to the target position, the rotational speed of rotational driving means is controlled based on the second rotational speed signal obtained from the disk recording medium, so that the disk recording medium can be rotated, based on the second rotational speed signal, immediately after the termination of seek operation. Therefore, the optical disk apparatus which can shorten the time necessary for seek can be realized.

Abstract: An optical disc system uses a recordable MD (mini disc) which can be applied to a multi-media system mass storage, such as a CD-ROM. In an optical disc system in which data of n sectors and added data of m sectors are error-corrected in a CIRC (Cross Interleave Reed-Solomon code) fashion and error-corrected data is recorded on an MD 16 in units of L+n+m sectors (L is the number of link sectors), when data is recorded and/or reproduced, a rotational speed of the MD 16 is selected to be (L+m+n) times at least. When n is 32 sectors, m is 1 sector, and L is 3 sectors then the rotational speed is 9/8 times and a maximum data transfer rate is selected to be 150 kB/s. In this way, data in a CD-ROM 10 can be recorded on the MD 16 at substantially the same transfer rate as the maximum data transfer rate (150 kB/s) of the CD-ROM 10.

Abstract: A detector for detecting the acceleration, the velocity or the displacement of a point is described. The detector includes a light source, at least two photoelectric elements spaced apart from each other over a predetermined distance and a focusing optical system disposed between the light source and the photoelectric elements; the combination being particularly suited for use as an optical seismic detector for detecting and mapping an underground stratum structure.