Abstract: In a projection display device having an illumination optical system which converts the light emitted from a point light source into a substantially parallel luminous flux, a light valve which modulates the light flux, and an optical projection system which projects images on the light valve onto a screen, the illumination optical system converts the light into a substantially parallel luminous flux having a cross section of substantially the same size and shape, e.g., rectangular shape, as the shape of the frame of the light valve.

Abstract: An optical head apparatus is provided with a holographic element composed of the first grid region which splits the light beam emitted from the light source into a plurality of light beams and the second grid region which diffracts the light beams reflected from the data-recording medium on the same plane, and prevents unnecessary signals from mixing themselves into the reproduction signal by varying at least the diffraction direction or the diffraction angle of the light beams in these grid regions.The first grid region has an elliptic aperture to make the .+-. primarily condensed spot beams onto the data-recording medium being extended elliptically to the data-recording direction.

Abstract: In case that the light beam emitted from a light source mounted on a base element is focused to a spot light on a data storage media to write the data, when the light beam reflected from the data storage media to return to the light source is reflected from the base element and focused again on the data storage media, it becomes difficult to precisely read/write the data on the storage media. In order to resolve the above problem, a light beam treating means is provided in the base element to prevent the re-incident light beams from being reflected toward the data storage media and focused thereon.

Abstract: An optical head device which consists of a semiconductor laser for emitting a light flux, a plano-parallel optical element operable to diffract the light flux into a zero-order diffracted light beam and a plurality of diffracted light beams, a condenser lens for converging the diffracted light beams on an information bearing surface of an optical disc to form respective light spots thereon, and a photo-electric detector assembly adapted to receive, and convert into electric signals, the light beams which have been reflected from the information bearing surface of the optical disc and then passed through the optical element via the condenser lens.

Abstract: In case that the light beam emitted from a light source mounted on a base element is focused to a spot light on a data storage media to write the data, when the light beam reflected from the data storage media to return to the light source is reflected from the base element and focused again on the data storage media, it becomes difficult to precisely read/write the data on the storage media. In order to resolve the above problem, a light beam treating means is provided in the base element to prevent the re-incident light beams from being reflected toward the data storage media and focused thereon.

Abstract: In an optical head apparatus for an optical information carrier comprising a semiconductor laser beam source, a condenser lens system and a beam splitter interposed therebetween in an optical system wherein the noise level may be beyond the allowable limit due to the excessive amount of the laser beam which is made incident on the laser beam source after being reflected by the information carrier, the reflected light attenuating means is provided between the optical information carrier and the semiconductor laser beam source, so that the noise level can be set to remain within the allowable limit.

Abstract: An optical head device comprises a semiconductor laser beam source, a diffraction grating for deflecting a laser beam emitted from the laser beam source at an angle of about 90.degree., a beam splitter placed between the laser beam source and the diffraction grating, and an objective for converging the laser beam deflected by the diffraction grating on an optical disc.A surface of the grating is formed at an angle of inclination in the range from 0.degree. to 45.degree. with respect to the central optical axis of the laser beam emitted from the laser beam source so that a reflecting diffraction beam caused by the diffraction grating is used as a deflected beam.

Abstract: In an optical type head device comprising a light source for emitting a light beam, a beam splitter, a condensor lens and a light detector for receiving said light beam for photoelectric conversion wherein a diffraction grating is provided to separate the light beam into a plurality of subbeams consisting of a zero-order subbeam and other subbeams so that a focussing error of the spot of the zero-order subbeam on an optical type data storing medium is detected by the fact that the light spot of the zero-order subbeam is deformed on the light detector, and a positional error of the spot of the zero-order subbeam with respect to a data track on the optical type data storing medium is detected depending on the position of the spots of the other subbeams.

Abstract: An optical type head device comprises a laser beam source for emitting a laser beam, a light focussing means for converging the laser beam on a data storing surface of an optical type data storing medium, a laser beam detecting means which receives the laser beam reflected by the optical type data storing medium and modulated by data held by the same, and converts the data into electric signals, a driving current supplying means for supplying a driving current to the laser beam source. The driving current supplying means comprises a high frequency current generator which supplys to the laser beam source a high frequency current having a waveform ranging from the lower part of the threshold value at which the laser beam source starts emission of the laser beam to the higher part of the thresheld value, and the frequency of the high frequency current is at least twice as high as the maximum frequency component of information which is contained in the data storing medium.

Abstract: In an optical head device, the distance between a light source, such as a semiconductor laser, and a condensing lens is altered along the optical axis thereof, so that the resulting spherical aberration may offset any component of spherical aberration that exists in an optical system as an inherent defect, whereby the wave-front aberration of the beam concentrated through the condensing lens is reduced. The device, therefore, includes an optical condensing system of improved aberration and condensation property.

Abstract: An optical head apparatus comprises a laser light source device emitting linearly polarized light, a converging lens for converging the light pencil emitted from the laser light source onto information recording tracks on a recording medium, and an optical system including a beam splitter for separating the light pencil reflected from the recording medium from the light pencil emitted from the laser light source. The converging lens is one formed by molding. The rotary position of the converging lens about the optical axis of the converging lens is so adjusted that the astigmatism of the optical system from the laser light source to the recording medium is minimum.

Abstract: An optical type head device comprises an optical beam separating means having a first surface which functions to reflect a principal light beam emitted from a light source and to separate it into a zero-order subbeam and positive and negative first-order subbeams.

Abstract: An optical head assembly for recording information on an optical disc or for taking out information already recorded, the optical head assembly including a semiconductor substrate and a dielectric light conducting layer formed on the substrate, the light conducting layer being internally formed with optical elements for converging laser beam from a laser beam source onto the optical disc and directing the reflected beam from the optical disc surface toward a photo detector. Output signal from the photo detector is used for reading information and also for allowing the optical head assembly to trace a track on the optical disc.

Abstract: A focusing error detecting device used in a head assembly for recording information to a recording surface of an optical disc or reading out information already recorded, the focusing error detecting device including a diffraction grating for focusing light which has been introduced from a light source into a thin-film waveguide layer, onto the recording surface, and two light receiving diffraction gratings for conducting the light reflected by the recording surface again into the waveguide layer. The two light receiving diffraction gratings have optical characteristics which differ from each other, depending the position of a focused spot of the light focused on the recording surface by the focusing diffraction grating. Therefore, by comparing the intensity of light from one light receiving diffraction grating with that from the other light receiving diffraction grating, there can be seen a positional relationship between the focused spot and the recording surface.

Abstract: An automatic focusing device for controlling the position of the objective lens relative to the information recording medium is provided with an astigmatic optical system which receives the reflected light beam reflected by the information recording medium. The light receiving surface of a light detector included in the astigmatic optical system consists of a central light receiving section formed approximatley symmetrically with respect to two axes intersecting each other perpendicularly and having a constricted central portion, and two side light receiving sections formed approximately symmetrically with respect to those two axes and opposite to each other. The light reception signal given by the central light receiving section and the light reception signals given by the side light receiving sections are fed to a focal position detecting circuit which gives a signal corresponding to the deviation of the objective lens from the focused position, on the basis of the light reception signals given thereto.

Abstract: An apparatus for draw forming glass filaments includes a melt furnace 1 having a bottom plate 12 with a plurality of flow holes therein, each terminating in a conical nozzle tip 2. Cooling fins 10 extend outwardly from a water pipe 11 and are disposed between the rows of tips, and additional cooling is provided at least during the initial start-up period by air blown across the nozzle tips from a manifold 13 disposed opposite the water pipe. With such an arrangement the flow hole diameters may be increased, which results in an exponential increase in the molten glass flow rate and filament production rate, while still achieving smooth initial and stable continuous filament forming conditions.