Abstract: An optical head comprising a semiconductor laser array which is used as a light source, and an optical system which guides laser beams from the array to a predetermined recording medium. The beam from one lasing point of the array is modulated by predetermined information and is used as a recording beam, while the beam from another lasing point is continuously oscillated and is used as a playback beam.

Abstract: In a laser beam recording apparatus comprising a laser source, an optical modulator for modulating the intensity of the laser beam from the laser source in response to an electrical signal, an optical scanner for deflecting the modulated laser beam, a recording medium on which the deflected laser beam is recorded, and a optical system for guiding the emitted laser beam from the laser source to recording medium, an automatic focusing device is provided for vibrating a lens or mirror in the optical system in synchronism with the scanning provided by the optical scanner, thereby converging the deflected laser beam into a small spot at any position on the recording medium.

Abstract: An optical information recording and reproducing apparatus is disclosed in which a predetermined signal is recorded on a track of a rotating recording medium by a recording light beam and the recorded information is reproduced by a reproducing light beam. The information recorded on the last record track is reproduced by the recording beam and the reproducing beam and radiating position of the recording beam on the recording medium is displaced by a predetermined distance from the last record track.

Abstract: A hologram apparatus comprises a rotary plane with a plurality of holograms concentrically or spirally arranged thereon, a light emitting source, and at least one photodetector for reading out reconstructed images of the holograms. During rotation of the rotary plane, the optical path of a light beam from the light emitting source is controlled, whereby the reconstructed images from the respective holograms are focused on the photodetector in succession. Some or all of the holograms are substantially oblong, and the long side and the short side of each oblong extend radially about the axis of the rotary plane and substantially orthogonally to the radial direction respectively.