Abstract: An improved polyurethane-urea elastic fiber is obtained by incorporating a specific urea compound prepared by reacting the following compounds together: (a) a nitrogen-containing compound having both at least one bifunctional amine group selected from a group consisting of a primary amine group and a secondary amine group and at least one nitrogen-containing group selected from a group consisting of a tertiary nitrogen group and a heterocyclic nitrogen group; (b) an organic diisocyanate; and (c) at least one compound selected from the group consisting of a mono- or di-alkylmonoamine, an alkylmonoalcohol and an organic monoisocyanate. With the incorporation of the specific urea compound, the polyurethane-urea elastic fiber which can be fast dyed exhibits enhanced thermosettability and increased elastic functions can be produced through a stabilized spinning process.

Abstract: An elastic polyurethane fiber excellent in chlorine resistance, which contains particles of a metal compound selected from oxides and hydroxides of a metal selected from zinc and magnesium, and composite oxides of zinc and magnesium, a treating agent selected from a fatty acid, a styrene/maleic anhydride copolymer or its esterified products and a phosphoric ester adhering to the surface of the particles. The elastic polyurethane fiber is appropriate for an elastic fiber material for swimwear used in a swimming pool. The elastic polyurethane fiber can be produced by spinning a polyurethane spinning dope containing the metal compound particles to which such a specific treating agent as mentioned above adheres. The spinning dope suppresses secondary agglomeration of the metal compound particles and enables stabilized spinning of a modified polyurethane fiber.

Abstract: A synthetic fiber which is excellent in moisture-absorbing/releasing property and exhibits high elongation and high stretch recovery, characterized in that it has moisture absorption ratios of 0.5 to 4.0% by weight in environments of 20° C.×65% RH and that of 4.5% by weight or more in environments of 30° C.×90% RH, respectively, and also has a difference between the absorption ratios in both the environments of 4.0% by weight or more. The representative examples of such fibers include polyurethane synthetic fiber and polyether synthetic fiber. The synthetic fiber maintains a high strength at break of an elastic fiber component thereof also in the state of having absorbed moisture, is excellent in color fastness to rubbing, and can be used for manufacturing a stretch fiber fabric product excellent in comfort through blending with another fiber material.

Abstract: An elastic polyurethane fiber comprising, based on the fiber weight, from 0.5 to 10% by weight of composite oxide particles containing aluminium and at least one combination of zinc and magnesium selected from the group consisting of combinations of zinc and magnesium in respective specific ratios. The elastic polyurethane fiber has excellent chlorine resistance, and is suitable for swimwear for use in swimming pools. The elastic fiber can be obtained by spinning a polyurethane spinning dope containing, based on the polyurethane, from 0.5 to 10% by weight of the composite oxide particles. Filter clogging and yarn breakage caused by secondary agglomeration of the composite oxide particles are extremely decreased, and stabilized spinning can be conducted over a long period of time.

Abstract: Disclosed is an optical disk apparatus in which light which returns from a recording medium is led to an photodetector composed of a plurality of light-receiving elements, and focusing is controlled on the basis of an focus error signal which corresponds to the relative distance between an objective and the recording medium. Whether the focusing pull has been conducted normally or not is determined by comparing a standard added signal level which is set by a focus search to the level of an added signal generated after the focusing pull has been conducted.

Abstract: In order to focus light beams which are projected onto an optical recording medium, the focusing optical system is moved in a vertical direction to the surface of the recording medium. A focus error signal produced by receiving the light returning from the recording medium is compared in turn with a predetermined plurality of reference levels. A focus servo-means is operated when this signal reaches the reference level within the focus pull-in region after passing through a predetermined order of reference levels.

Abstract: A focus servo control device has a focus driver for driving an optical system having an objective lens, and a servo control section for detecting that the optical system is within a focus servo control range. A focus servo control loop is formed in response to a detection signal representing that the optical system is in the focus servo control range, and the optical system is driven under servo control until the amount of light reflected by the optical disk is detected as a maximum.

Abstract: A semiconductor laser drive device is adopted in an optical disk read/write unit for writing/reading data in/from an optical disk. The device has driver for modulating the laser beam of the intensity corresponding to a drive current value in accordance with write data WDATA, photodiode for detecting the light-emitting intensity of semiconductor laser, and APC circuit for comparing the detected light-emitting intensity of photodiode with a desired light-emitting intensity and changing the drive current value for semiconductor laser until the detected light-emitting intensity coincides with the desired light-emitting intensity. APC circuit has battery backup memory. A drive current value obtained at the start of the device is stored in memory. Thereafter, APC circuit starts APC from the stored drive current value.

Abstract: An apparatus for controlling the tracking of an optical disk by moving an objective lens and a carriage supporting the objective lens. The apparatus comprises a lens tracking mechanism comprising an actuator and a lens tracking circuit, and an equivalent circuit having the same response characteristic as the lens tracking mechanism. The lens tracking mechanism moves the lens in real time in the radial direction of the disk in accordance with a tracking error signal representing the distance between a laser beam spot and a target track. The carriage is moved also in the radial direction of the disk in accordance with a sine-wave signal approximating the eccentricity of the disk. The eccentricity has been detected from the distance over which the lens is moved when the carriage is not moved. This distance is not detected by measuring, but obtained from the output signal which the equivalent circuit generates in response to the tracking error signal.

Abstract: In order to focus light beams which are projected onto an optical recording medium, the focusing optical system is moved in a vertical direction to the surface of the recording medium. A focus error signal produced by receiving the light returning from the recording medium is compared in turn with a predetermined plurality of reference levels. A focus servo-means is operated when this signal reaches the reference level within the focus pull-in region after passing through a predetermined order of reference levels.

Abstract: The optical recording and reproducing apparatus comprises a magnetic field applying section, a movable mechanism for moving the magnetic field applying section, a distance detecting section for detecting a distance between magnetic poles of the magnetic field applying section and the surface of a recording medium, and a distance control section for maintaining the above distance constant in response to an output of the distance detecting section. The distance between two magnetic pole ends of the magnetic field applying section can be minimized. Further, on the basis of the tracking control of either one of the recording and erasing light beams, it is possible to enable a high-precision tracking control to the other of the two light beams.

Abstract: In a method of photoelectrically judging a particle agglutination pattern formed on a conical bottom surface of a reaction vessel by particles descending upon the bottom surface, at least two judging steps utilizing a total particle amount, a thickness ratio, an inclination and so on are applied to the particle agglutination pattern to judge finally the pattern as one of an integral pattern (-), an intermediate pattern (?) and a uniform deposition pattern (+). In this manner, since all the inaccurate patterns are judged finally as the intermediate pattern (?) and are re-examined, it is possible to always perform an accurate judgment for the particle agglutination pattern.