Abstract: An optical disk drive having an optical disk that permits transmission of a laser beam, an optical disk holding mechanism configured to rotatably support the optical disk, a first laser beam irradiation mechanism disposed on one side of the optical disk, causing the first laser beam to be vertically incident on one surface of the optical disk, and a first evanescent optical system disposed on the other side of the optical disk. The first evanescent optical system is configured to receive the first laser beam which emanates from the laser beam irradiation mechanism and passes through the optical disk, and radiate the first evanescent wave to the other surface of the optical disk having at least one recording surface.

Abstract: An upper recording layer is arranged on a portion having distance h from the disc surface, a lower recording layer is arranged on a portion having distance h+&Dgr;h from the disc surface, a space layer having thickness &Dgr;h is arranged between the upper and lower recording layers, and a cover layer having thickness h is arranged between the upper recording layer and disc surface. Thickness &Dgr;h of the space layer is specified, so that a coherence length (Lc) which is determined by central wavelength &lgr;0 and its half-width &Dgr;&lgr; of the exit light power spectrum of a laser beam is smaller than the optical path difference (&Dgr;L) between light u0 which is directly reflected by the surface of the cover layer, and light u2 which is transmitted through the cover layer and space layer, is reflected by the lower recording layer, and leaves the cover layer.

Abstract: An optical recording/reproduction apparatus records and reproduces information onto and from an associated recording medium by use of light from a light source. The apparatus includes a lens capable of generating an evanescent wave which is disposed in a light path from the light source to the recording medium, and a partial beam light intercepter for intercepting at least part of the light passing through the lens without contributing to generation of the evanescent wave. The light intercepter blocks the center part of a laser beam incident to the evanescent wave generating lens, thus reshaping it into a beam of hollow annular cross-section. This improves the optical resolution of the record/reproduction apparatus.

Abstract: An optical disc apparatus is provided by putting together two substrates with a combined thickness "h", as a recording medium. The two substrates each have a signal mark or a reflective layer which is capable of being the signal mark at least on the backside of the substrates. A laser beam is radiated onto the optical disc through an objective lens, and a reflected light from the reflective layer is detected by means of an optical detection device. One output of the optical detection device is supplied to a signal reader; the other of output thereof is supplied to a focusing apparatus for detecting a focus error of the objective lens and for controlling the positions of the objective lens with respect to the optical disc. Further, in the optical disc apparatus, if a principal wavelength of laser beam source is set as .lambda..sub.0 ; a half-width of laser beam source is set as .DELTA..lambda.; a numerical aperture of the objective lens is set as NA; and a refractive index of substrate material is set as n.

Abstract: A multibeam scanning apparatus includes a polygon mirror provided between laser beam generation sources and a photosensitive drum of a target, for deflecting laser beams emitted from the laser beam generation sources to scan the photosensitive drum, galvanomirrors provided between the polygon mirror and each of the laser beam generation sources, for allowing a radiating position of each of the laser beams to move on the photosensitive drum, a sensor located in a downstream position of the polygon mirror and optically in conjugation with the photosensitive drum, for sensing the radiating positions of the laser beams on the photosensitive drum, and controller for controlling the galvanomirrors in order to set the radiating positions of the laser beams on the photosensitive drum in response to a signal output from the sensor.

Abstract: An exposure apparatus for a semiconductor wafer, a liquid crystal display panel and so on. The exposure apparatus comprises a light source, a holding means for a mask and a target, a moving means for moving the holding means and optical alignment systems. The optical alignment system has a moving base on which a detecting means is installed. The moving bases are arranged in the same plane and have narrow portions in their front.

Abstract: A method and an apparatus for measuring a displacement between two objects. Corresponding pairs of regions of the two objects each have at least one diffraction grating which generate two-dimensionally distributed diffracted light beams. These light beams are diffracted and caused to interfere with each other in the paired regions, whereby two-dimensionally distributed diffracted interference light beams are emitted. A light beam of a specific order is detected from each of these diffracted interference light beams, and is converted into a beat signal. The displacement is obtained in accordance with the phase difference between these beat signals.

Abstract: A first diffraction grating is formed on a mask, and a second diffraction grating is formed on a wafer. Two light beams having slightly different frequencies interfere with each other and are diffracted as they travel through the first diffraction grating, are reflected by the second diffraction grating, and again pass through the first diffraction grating. As a result, they change into thrice diffracted light beams. The diffracted light beams are combined into a detection light beam which has a phase shift .phi..sub.A representing the displacement between the wafer and the mask, or a phase shift .phi..sub.G representing the gap between the wafer and the mask. The detection light beam is converted into a detection signal. The phase difference between the detection signal and a reference signal having no phase shifts are calculated, thus determining phase shift .phi..sub.A or .phi..sub.G. The displacement or the gap is determined from the phase shift.

Abstract: A first diffraction grating is formed on a mask, and a second diffraction grating is formed on a wafer. Two light beams having slightly different frequencies interfere with each other and are diffracted as they travel through the first diffraction grating, are reflected by the second diffraction grating, and again pass through the first diffraction grating. As a result, they change into thrice diffracted light beams. The diffracted light beams are combined into a detection light beam which has a phase shift .phi..sub.A representing the displacement between the wafer and the mask, or a phase shift .phi..sub.G representing the gap between the wafer and the mask. The detection light beam is converted into a detection signal. The phase difference between the detection signal and a reference signal having no phase shifts are calculated, thus determining phase shift .phi..sub.A or .phi..sub.G. The displacement or the gap is determined from the phase shift.

Abstract: According to this invention, a method and apparatus for aligning a mask and a wafer arranged to oppose each other, in a direction along their opposing surfaces, relative to each other, are arranged as follows. A first diffraction grating as a one-dimensional diffraction grating, bars of which extend in a direction perpendicular to an alignment direction, is formed on the mask. A second diffraction grating which has a checkerboard-like pattern, is formed on the wafer. The first diffraction grating is irradiated with laser beam emitted from a light source. Light beams diffracted and transmitted through the first diffraction grating is transferred to the second diffraction grating. Light beams diffracted and reflected by said second diffraction grating are transferred to said first diffraction grating. The light beams are diffracted by and transmitted through said first diffraction grating, again. Is detected, one of the diffracted light beams, which do not propagate along a predetermined plane.

Abstract: According to this invention, a method and apparatus for setting a gap to a predetermined distance between a mask and a wafer facing each other, are arranged as follows. First and second diffraction grating are formed on a mask and a wafer. The first diffraction grating is one-dimensional type and has parallel bars extending in a predetermined direction. The second diffraction grating is one-dimensional type and has parallel bars extending in a direction perpendicular to the predetermined direction. The second diffraction grating may be two-dimensional type having cross-bars. Laser beam is radiated from a light source onto the first diffraction grating. The light beams diffracted and transmitted through the first diffraction grating are transferred to the second diffraction grating. The light beams diffracted and reflected by the second diffraction grating are transferred to the first diffraction grating. The light beams are diffracted and transmitted through the first diffraction grating.