Mitsubishi Denki Kabushiki Kaisha

Koji Shindo

Yoshio Fujii

Masaru Tsuchihashi

Masafumi Ototake

Mitsuo Fukuda

Masahiro Kajihara

Yuuji Shimote

In a photomagnetic eraser, information recorded on a magnetic-layer of a photomagnetic recording medium is erased or initialized by applying light over the photomagnetic recording medium from a light source in a reflector with heating and also by supplying a magnetic field to the photomagnetic recording medium along its axis of easy magnetization. In one form, a plurality of light sources may be disposed in the concave surface of a single reflector. Alternatively, the photomagnetic recording medium may be double-faced, and the light source and reflector may be disposed on each side of the double-face recording medium.

Photomagnetic eraser

In a magneto-optical eraser, information recorded on a magnetic layer of a magneto-optical recording medium is erased or initialized by applying light over the magneto-optical recording medium from a light source (13,43) in a reflector to heat the magneto-optical recording medium and also by supplying a magnetic field to the magneto-optical recording medium along its axis of easy magnetization. In one form, a plurality of light sources (13) may be disposed in the surface of a single reflector (12). Alternatively, the magneto-optical recording medium may be double-faced, and a light source and reflector may be disposed on each side of the double-face recording medium. A pre-heater (52) may increase the temperature within a glass housing (50,51) to a temperature less than the softening point of the medium substrate.

Magneto-optical eraser

An apparatus which inspects disc-shaped information recording media, such as optical disks and magnetic disks, in a single reproduction. The apparatus detects the type of defect and classifies the defects into defect clusters by the defect position in the radial and circumferential directions. Type of defect or defect cluster, position and size are memorized.

Defect inspecting apparatus for disc-shaped information recording media

The present invention relates to a master disk used as a matrix for manufacturing a stamper by transferring, which is used for reproducing an optical disk, the master disk according to the present invention is provided with an appointed number of calibration tracks formed at an appointed pitch symmetrically relative to the center of guide tracks in the area including a position corresponding to an edge portion of a center hole of the stamper, whereby the center hole of the stamper can be easily formed concentrically with the guide tracks of the master disk and the tolerance of diameter of the center hole or the eccentricity between the center of the center hole and the center of the guide track can be easily measured.

Master disk

The apparatus inspects defects on tracks of an object to be inspected such as an optical disc or stamper. The apparatus has a defect detector, a controller for controlling the movement of the object, and a microscope for observing the tracks of the object. Position information on defects is obtained by the detector and, according to this position information, the object is moved so that the defects can be in the visual field of the microscope.

Growing community of inventors

Amagasaki, Japan

Koji Shindo