Abstract: An optical phase-change disc comprises a substrate having thereon a spiral groove or concentric grooves for guiding a focused light beam, and a layer structure including a recording layer and protective layers sandwiching therebetween the recording layer. The groove has wobble for recording ATIP (absolute time information) or ADIP (address information). The following relationship between the groove width GW, beam diameter R.sub.0 and wobble amplitude a.sub.w :0.25.ltoreq.GW/R.sub.0 .ltoreq.0.45or0.65.ltoreq.GW/R.sub.0 ;and0.03.ltoreq.a.sub.w /GW.ltoreq.0.08hold for preventing distortion of the groove caused by repeated overwriting operation to improve reliability of the optical disc.

Abstract: An optical recording process for recording data on a recording medium of phase-change type employs laser power modulation scheme for mark-length modulation recording. The process selects one of pulse division schemes for modulating the laser power in accordance with a linear velocity on the disc. The recording laser includes m pulses for nT mark having a power level Pw and a duration of .alpha..sub.i T, with m intervals .beta..sub.i T sandwiched therebetween, wherein on condition that m=n-k and .SIGMA..alpha..sub.i +.SIGMA..beta..sub.i =n-j, .alpha..sub.i or bias power Pb.sub.i is changed in accordance with the linear velocity, Pb.sub.i being a bias power level for modulation, k and j being an integer and a real number, respectively, both selected between 0 and 2. A large range of the linear velocity margin can be obtained for the disc without changing either the composition of the phase-change material or multi layer structure on the disc.

Abstract: An optical recording process for recording data on a recording medium of phase-change type employs laser power modulation scheme for mark-length modulation recording. The process selects one of pulse division schemes for modulating the laser power in accordance with a linear velocity on the disc. The recording laser includes m pulses for nT mark having a power level Pw and a duration of .alpha..sub.i T, with m intervals .beta..sub.i T sandwiched therebetween, wherein on condition that m=n-k and .SIGMA..alpha..sub.i +.SIGMA..beta..sub.i =n-j, .alpha..sub.i or bias power Pb.sub.i is changed in accordance with the linear velocity, Pb.sub.i being a bias power level for modulation, k and j being an integer and a real number, respectively, both selected between 0 and 2. A large range of the linear velocity margin can be obtained for the disc without changing either the composition of the phase-change material or multilayer structure on the disc.

Abstract: One page is segmented into a plurality of bands (segments), and dot image data is generated on a per band basis from given information (graphic object). High-speed printing with a small-sized memory is achieved by allowing one band to be converted into dot image data and dot image data for another band to be transmitted to a printer, concurrently in parallel. When the conversion of a band to dot image data needs more time than is available for printing one band, or when the data quantity of object per page exceeds an allocated memory area, an object corresponding to a degraded image data is generated, and then the degraded image data is generated on a per band basis based on the resulting object.

Abstract: The disclosure describes an optical recording medium for recording, erasing and reading-out information by irradiation a laser beam, comprising:a lower dielectric protective layer, a phase-change-type recording layer, an upper dielectric protective layer and a metal reflective layer successively deposited on a transparent substrate formed with grooves, in whichboth of grooves and lands are used as a recorded region,a groove depth (d) satisfies the following relation (1):.lambda./7n<d<.lambda./5n (1)wherein .lambda. represents a wavelength of an irradiation light and n represents a refractive index of the substrate, anda groove width (GW) and a land width (LW) satisfy the following relation (2):0.1 .mu.

Abstract: There are disclosed a process for producing an oligomer by oligomerizing a raw material comprising an unsaturated bicyclo heptane derivative and/or an unsaturated bicyclo octane derivative, which comprises the step of restricting the contents of dienes contained in the raw material to at most 1% by weight; and a process wherein the raw material is subjected to solid acid treatment simultaneously with or prior to distillation and then to oligomerization. The above process can efficiently produce the oligomer well suited for use in a traction drive fluid having a low viscosity and exhibiting excellent performance over a wide temperature range.

Abstract: Two thickness detectors (5) each for outputting an electric signal representing the thickness of a paper sheet (B) passing thereby are arranged side by side in the width direction of a paper sheet conveyance path (3). Parameters such as paper sheet thickness, length, the existence of skew and, if skew exists, the skew angle (.theta.), are calculated based on the output signals from the thickness detectors. This facilitates detection of two or more overlapping bank notes among a wide variety of bank notes having different thicknesses or in case of a bank note having a significantly non-uniform thickness. The correct thickness of a paper sheet is also obtained at all times by using the skew angle and the reference length (W) of the paper sheet. This not only facilitates detection of two overlapping bank notes among a wide variety of bank notes having different thicknesses or in case of a bank note having a significantly non-uniform thickness, but also enables detection to be made very accurately.

Abstract: In order to make hard and soft contact lenses having a pore diameter and a pore density optimum for use as oxygen permeable contact lenses, the contact lens after molding is subjected to irradiation of a polyvalent heavy ion beam having a mass number of 2 to 100 (preferably 10 to 80) and an ion energy of 10M eV (preferably 50M eV) or higher, at an ion radiation density of 10 to 10.sup.9 ions/cm.sup.2 (preferably 10.sub.2 to 10.sub.5 ions/cm.sup.2) and thereafter ultrasonically etched (preferably at 10 to 50 MHz) at a temperature of 4 to 50.degree. C. (preferably 10.degree. to 30.degree. C.) in the presence of chloroacetic acid (preferably tricholoracetic acid).

Abstract: An apparatus for exposing of an image of an original film on photosensitive material, the film and the photosensitive material being held together by vacuum contact between a transparent plate and a flexible sheet. The apparatus includes a squeegee unit which moves while pressing the flexible sheet. The squeegee unit forcibly moves the air, thereby speeding up the setting of the vacuum contact. The apparatus also includes a speed changing unit for changing the speed of the squeegee unit depending on the resistance of the air to movement. If the air moves easily, the squeegee unit moves rapidly. If the air does not move easily, the squeegee unit moves slowly, or the squeegee unit stops for a prescribed period and then, after the air is removed, is restarted. Thus, complete removal of air is carried out rapidly.

Abstract: A vacuum contact printing apparatus includes: a transparent plate on which an original film and a photosensitive material are placed, an overlay sheet which covers the transparent plate, a friction reducing sheet provided between the transparent plate and the overlay sheet, and an evacuating device for removing air from between the overlay sheet and the transparent plate. The transparent plate is covered with the friction reducing sheet prior to or simultaneously with the covering of the original film and photosensitive material placed on the transparent plate wiht the overlay sheet. Frictional force caused by the change of the form of the overlay sheet can be prevented from being applied to the photosensitive material because the overlay sheet smoothly slides on the friction reducing sheet.

Abstract: An apparatus for driving a semiconductor laser device wherein the optical output of the laser device is maintained at a predetermined level by a feedback control. The apparatus includes at least two D/A converters. One of the D/A converters is used for conducting a coarse adjustment of the optical output level, and another of the D/A converters is used for conducting a fine adjustment of the optical output level.

Abstract: A light-emitting element and a light-responsive element are optically connected with each other through a U-shaped optical guide. An output level of the light-responsive element indicates whether the U-shaped guide is above or below the liquid-level.