Abstract: Provided are a roll for roll forming and a roll forming method therefor, by which a strip of sheet material is continuously fed and passed between roll stands that are arranged continuously, and is sequentially formed so that the sectional shape of the sheet material becomes circular, and by welding both ends of the sheet material, a pipe is finally produced. In the method, pressure parts and non-pressure parts are selectively disposed on a convex roll or a concave roll and the frequency of pressuring by the convex roll and the concave roll is reduced or adjusted such that the work hardening of the roll formed material or produced pipe is lowered or made to be uniform. Accordingly, the material characteristic and reprocessing characteristic of the roll formed material or pipe are greatly improved.

Abstract: An optical pickup apparatus that is capable of recording and reproducing various types of optical discs having a recording format, such as a different substrate thickness, etc., without an additional aperture number control device. In the apparatus, at least two light sources generate a different wavelength of lights. A focusing optical system focuses a light from the light source onto the optical recording medium. A receiving optical system receives a light reflected from the recording medium. The focusing optical system is configured in such a manner to generate a predetermined range of aberration in a light spot formed on the optical medium by the lights from any one of the light sources. Since the apparatus can access recording media having a different recording format by using an optical system and an aberration optimized for a single optical recording medium without an additional aperture number control device, so that its configuration is simplified.

Abstract: An optical path difference compensation means of a birefringence material: Which transmits incident lights having different wavelength and compensates a phase of the incident light to decrease aberration of one of said incident lights without affecting the other incident light.

Abstract: An improved optical pick-up apparatus capable of reading data irrespective of disc type capable of reading various kinds of discs having different thicknesses and writing densities using only one pick-up apparatus, which includes a light source; a beam splitter for passing through or splitting a beam from the light source; an objective lens for condensing the beam onto corresponding disc among discs having different thicknesses and different densities; a numerical aperture control unit for controlling an effective numerical aperture of the objective lens so as to execute a focussing operation with respect to a certain disc; and a photo-detector for receiving the beam reflected by the disc and transmitted from the beam splitter.

Abstract: An improved optical pick-up apparatus capable of reading data irrespective of disc type capable of reading various kinds of discs having different thicknesses and writing densities using only one pick-up apparatus, which includes a light source; a beam splitter for passing through or splitting a beam from the light source; an objective lens for condensing the beam onto corresponding disc among discs having different thicknesses and different densities; a numerical aperture control unit for controlling an effective numerical aperture of the objective lens so as to execute a focussing operation with respect to a certain disc; and a photo-detector for receiving the beam reflected by the disc and transmitted from the beam splitter.

Abstract: An improved optical pick-up apparatus capable of reading data irrespective of disc type capable of reading various kinds of discs having different thicknesses and writing densities using only one pick-up apparatus, which includes a light source; a beam splitter for passing through or splitting a beam from the light source; an objective lens for condensing the beam onto corresponding disc among discs having different thicknesses and different densities; a numerical aperture control unit for controlling an effective numerical aperture of the objective lens so as to execute a focussing operation with respect to a certain disc; and a photodetector for receiving the beam reflected by the disc and transmitted from the beam splitter.

Abstract: An improved absolute position detection method is provided for a stroke sensing cylinder which includes a magnetic scale detecting step for obtaining a plurality of sine wave form voltages having different phases using a magnetic sensor unit in accordance with a driving operation of the cylinder. A wave form generation step is also provided for converting the sine wave form voltage obtained in the magnetic scale detection step into a square wave form and generating a triangle wave form having the same period as the thusly converted square wave form. A first absolute position value detection and stroke direction judging step is then provided for judging a first absolute position value and stroke direction of the cylinder using a pair of square and triangle wave forms generated in the wave form generation step.

Abstract: An optical pickup device which is mechanically simple and economical to shape waveforms of a laser beam, includes a light source for emitting the laser beam having a Gaussian light distribution, a beam splitter having an optical thin film coating surface which transmits the laser beam emitted from the light source at a constant light distribution, for shaping waveforms of the laser beam, a collimation lens for outputting a round shaped beam having a constant light distribution, from the transmitted laser beam of the beam splitter, and an object lens for focusing the round shaped beam from the collimation lens on an optical disk. The optical pickup device uniformly maintains light distribution of incident light which passed through the beam splitter using the optical thin film coating characteristic.

Abstract: Disclosed is an apparatus for measuring a dimension of a manufactured article to be worked on a cylindrical grinding machine. The apparatus includes non contact-type measuring sensors capable of measuring the outer diameter and cylindricity of the manufactured article while the manufactured article is mounted on the cylindrical grinding machine. The apparatus comprises a main body which is positioned above a cylindrical grinding machine. The main body includes a bed having a through opening formed through a center thereof and a plurality of support members for supporting the bed. A sensor attachment of the apparatus is positioned on the bed. A sensor attachment includes at least two pairs of non contact-type measuring sensors. The pairs of non contact-type measuring sensors are spaced opposite from each other in order to measure the outer diameter and cylindricity of the manufactured article.

Abstract: An electrochromic display device (ECD) for an optical pick-up apparatus which is capable of maximizing a transmissivity of a laser beam by forming a reflection prevention layer on the outer surfaces of transparent substrates, includes first and second transparent substrates formed at both sides of the ECD with a predetermined interval therebetween, first and second transparent electrodes coated on the inner surfaces of the transparent substrates, respectively, an electrochromic layer coated on the inner surface of the second transparent electrode so that colorizing or decolorizing may be carried out reversibly, a counter eletrode layer coated on the inner surface of the first transparent electrode, an electrolytic layer formed between the counter electrode layer and the electrochromic layer, and a reflection prevention layer coated to have more than one layer so as to prevent a beam from being reflected on the outer surfaces of the first and second transparent substrates.