Abstract: A method of exposure to a light pattern containing a first strip-shaped portion extending in a first direction and a second strip-shaped portion extending in a second direction comprises steps of placing, on a light-receiving face, a first mask having a strip-shaped slit corresponding to the first strip-shaped portion extending in a first direction of the pattern, projecting, to the first mask, a first linearly polarized light beam polarized in the second direction to irradiate the light-receiving face through the slit of the first mask, removing the first mask from the light-receiving face, and placing, on the light-receiving face, a second mask having a strip-shaped slit corresponding to the second strip-shaped portion extending in a second direction of the pattern and projecting, to the second mask, a second linearly polarized light beam polarized in the first direction to irradiate the light-receiving face through the slit of the second mask.

Abstract: A method for reproducing information from a magneto-optical medium which includes a memory layer composed of magnetic film and a displacement layer composed of a magnetic film laminated with the memory layer is provided. Information signals are recorded on magnetized areas arranged in a predetermined direction on the memory layer. Domain walls having arc shapes curved in the same direction are formed on borders of the magnetized areas.

Abstract: An optical information reproducing apparatus for reproducing information by irradiating a recording medium with a reproducing light beam includes a light source for generating the reproducing light beam, a reproducing circuit for reproducing a reproduction signal by using the light beam, and an adjusting circuit for adjusting the light beam power. The adjusting circuit adjusts the beam power to a value larger than the light beam power at which a value obtained by normalizing the reproduction signal with the beam power is maximized.

Abstract: An optical information recording medium from which information is reproduced by a light beam having a spot diameter a includes track guide grooves and lands formed into recesses/projections, and pre-pits indicating the addresses of the track guide grooves and the lands. The width of the pre-pits is 0.2 a (inclusive) to 0.5 a (exclusive), and a pitch T of the track guide grooves is given by0.7 a<T/2<0.8 a.

Abstract: An optical information recording/reproducing apparatus records information on an optical information recording medium and/or reproduces the recorded information by irradiating a plurality of light spots on the recording medium. The apparatus includes a first light source for emitting a light beam with a wavelength .lambda..sub.1, and a second light source for emitting a light beam with a wavelength .lambda..sub.2. A light spot forming unit focuses the light beam with the wavelength .lambda..sub.1 and the light beam with the wavelength .lambda..sub.2 through an objective lens, and forms first and second light spots on the information recording medium. The following relations are substantially established: 1.gtoreq.D.sub.1 /W.sub.1.perp. .gtoreq.0.6; 3.2-2.6.times.1n.alpha..gtoreq.D.sub.2 /W.sub.2 .perp..gtoreq.1.0-1.2.times.1n.alpha.; and .alpha.=(.lambda..sub.2 /.lambda..sub.1).times.(D.sub.1 /D.sub.2). D.sub.1 is the diameter of the light beam with the wavelength .lambda..sub.

Abstract: A method and apparatus for reproducing information on a magneto-optical recording medium can reproduce a signal having a period equal to or smaller than the diffraction limit of light at high speed, can obtain a reproduced signal with a high C/N ratio from a small recorded domain at an amplitude nearly equal to that of a large recorded domain, can greatly improve the recording density and transfer rate, and can also make the reproduction apparatus compact. The information reproduction method includes the steps of irradiating a laser beam onto a medium and forming a temperature distribution having at least two peaks by the laser beam. The apparatus has a laser light source and an optical system for irradiating a laser beam emitted by the light source onto the medium, wherein the laser beam forms the temperature distribution having at least two peaks.

Abstract: An optical information recording and/or reproducing apparatus has a detecting apparatus for detecting a tracking error signal.

Abstract: An optical head for an opto-magnetic information recording and reproducing apparatus having stable characteristics. The optical head has a forward path optical system including a polarization beam splitter for reflecting a linearly-polarized light beam in the form of a divergent light beam from a light source, and an objective of a finite imaging system for converging the reflected light beam on an opto-magnetic recording medium, and a backward path optical system in which the reflected light beam from the recording medium is converged by the finite-imaging objective, and in which the converged light beam passes through the polarization beam splitter and is further reflected by a total reflection surface for reflecting this light beam to be led to detection means. A phase difference created in the convergent light beam when the light beam passes through a polarized light separating surface of the polarization beam splitter is compensated for by the total reflection surface.

Abstract: A recording/reproducing/erasing optical head for generating a plurality of light beams detects a defocused state by a method in which a light beam is caused to be nearly parallel to form optical spots on an opto-magnetic disk, the light beam from the optical spots on the opto-magnetic disk is condensed on a sensor by an objective lens and a condenser lens, and the size of the light spot on the sensor spaced by a predetermined distance in front of or behind the focal point of the condenser lens, and the size of the light spot on the sensor indicate the defocus state, wherein if the focal length of the objective lens is denoted as f.sub.o, the numerical aperture of the objective lens as NA, the focal length of the condenser lens as f.sub.con, the predetermined distance is .DELTA.d[mm], and (f.sub.con /f.sub.o).sup.2 =.gamma., the following relation is satisfied:0.005.gamma..DELTA.d.+-.(0.010/NA-0.003).gamma..

Abstract: An optical information recording and/or reproducing apparatus includes an optical system for letting first and second optical beams pass through substantially the same optical path to form first and second optical spots on the same information track on a surface of an information recording medium and for guiding reflected light from the surface of the information recording medium to photo sensors to detect recorded information in the information recording medium. The first optical spot is used for focusing error detection, tracking error detection, erasing of old information, and recording of new information. The second optical spot is used both for reproduction-while-recording of newly recorded information and for normal reproduction of recorded information. The first optical spot advances and the second optical spot follows on a moving information track.

Abstract: A double beam optical head is so arranged that at least two optical beams are guided into an objective lens to be focused thereby to form at least two optical spots on an optical information recording medium and that two optical spots among optical spots are used to record and/or reproduce information with respect to the optical information recording medium. An optical system includes the objective lens and a light source for producing the two optical beams. The optical system is so arranged that, in guiding the two optical beams into the objective lens, the centers of the intensity distributions of the two optical beams are approximately symmetrically located with each other with respect to the optical axis of the objective lens. A magneto-optical recording and/or reproducing apparatus may be constructed of the optical head and a magnetic head for applying a magnetic field to the magneto-optical recording medium.

Abstract: By using a two-beam optical head, simultaneous focusing of two light spots can be achieved and the execution of simultaneous erasure, recording and reproduction of information can be easily realized even in an inexpensive optical system which uses lenses having chromatic aberration. The two-beam optical head includes a monolithic semiconductor laser array having two light-emitting points which emit first and second light beams having different light intensities, and an optical system for forming first and second light spots on a magnetooptical disk. The two light beams pass along substantially the same optical path. The direction of the arrangement of the first and second light-emitting points of said light source unit is inclined with respect to a plane perpendicular to the optical axis of the optical system to focus the light spots on the same plane of the magnetooptical disk.

Abstract: A plural beam optical head is constituted by an optical system for imaging a plurality of light beams onto an optical information recording medium, a double-refractive crystal prism and a sensor. The plurality of light beams obtained from the optical information recording medium are separated into components the polarized direction of which are orthogonal one another by the double-refractive crystal prism. The direction of arrangement of the plurality of light beams incident on the double-refractive crystal prism is substantially perpendicular to the direction of separation of the light beams obtained from the double-refractive crystal prism. The light beams from the double-refractive crystal prism are received by the sensor.

Abstract: A system for a magneto-optical information recording/reproducing system has a polarizing beam splitter for splitting a light beam reflected by a magneto-optical disk, which utilizes the Kerr effect, into one light beam for detecting focussing errors and two light beams for detecting tracking errors. The polarizing beam splitter operates to split a polarizing light beam in such a manner that the two light beams for detecting tracking errors have a polarizing beam composition that is perpendicular to the polarizing beam composition of the light beam for detecting focussing errors. The optical system includes a light receiving element for receiving the light beam split by the beam splitter. The light receiving element has a light receiving portion for detecting focussing errors and a light receiving element for detecting tracking errors. The light receiving portion for detecting focussing errors has a plurality of light receiving areas for receiving the light beam for detecting focussing errors.

Abstract: A plural-beam optical head is constituted by a monolithic semiconductor laser array having a plurality of light emitting points, a collimator lens for collimating laser beams emitted from the plurality of light emitting points, an objective lens for imaging the laser beams on an optical information recording medium, and a device for expanding the diameters of the laser beams in the direction of arrangement of the plurality of light emitting points. In the plural optical head, the following condition is satisfied:(d.multidot.f.sub.0)/(f.sub.col .multidot.m)<20 [.mu.m],where d is the maximum spacing between adjacent ones of the plurality of light emitting points, f.sub.col is the focal length of the collimator lens, f.sub.0 is the focal length of the objective lens, and m is the expansion magnification of the device for expanding the diameters of the laser beams.

Abstract: An optical disk apparatus comprises an optical pickup having an optical pickup body carrying a laser and a photodetector responsive to light emitted from the laser and reflected by the optical disk for producing tracking error signals mounted on the optical pickup body for reciprocal movement in a tracking direction responsive to operation of an actuator, and supports an objective for focusing the beam on the disk. A position sensor produces position signals in response to displacement of the movable portion in the tracking direction. Finally a servo tracking circuit outputs driving signals to the actuator on the basis of tracking error signals produced either in response to tracking error signals produced from outputs of the photodetector and position signals produced from output signals of the position sensor, in response only to the latter.

Abstract: According to an optical system of an optical pickup of the present invention, beam is split into two portions by a light refracting member which is disposed between a condenser lens and a light receiving element, a portion of beam entering into the light refracting member is utilized for detecting tracking errors, and the remaining portion of beam which is not permitted to enter into the light refracting member is utilized for detecting focussing errors by a knife edge test. With the above-mentioned constitution of the optical system, a tracking error composition is prevented from interferring with the focussing error detection and, at the same time, both the tracking errors and focussing errors can be detected by one light receiving element. Thus, the number of component parts can be reduced and the optical system itself can be made compact.