Kabushiki Kaisha Toshiba

Takayuki Asano

Isao Hoshino

Takashi Yoshizawa

In an information recording/reproducing apparatus, a light beam emitted from a semiconductor laser is guided to a beam splitter. The light beam passing through an incident surface of the splitter is splitted into first and second light beam by a beam splitting layer. The first beam passing through the splitting layer is emerged from a first emerging surface and guided to an optical disk. The first light beam after being reflected from the optical disk is returned to the first emerging surface and passes through the first emerging surface. The returned first light beam passed through a second emerging surface and defected by a detector so that a retrieving signal is generated from a detector. The second light beam reflected from the beam splitting layer is directed to a concave mirror of the splitter and is converged on a mirror detector through a third emerging surface so that a mirror signal for controlling the semiconductor laser is detected.

Apparatus for optically recording and reproducing information from an

An optical head which can be rotated about the rotation center by a magnetic force. There is a photodetector which is divided into a plurality of detection regions and as the optical head rotates, different detection regions are examined to determine a tracking error. Rotating between the inner and outer peripheral portions of an optical disk, the optical head selects a track on the optical disk on which information is recorded, radiates a light beam focused on the selected track, receives the light beam reflected by the optical disk to a second photodetector having three divided parallel sensor segments, and reproduces the information recorded on the optical disk. In consideration of the fact that in an optical disk rotated at a constant angular velocity, the degree of modulation of a retrieving information signal recorded on a recording layer on the optical disk is increased toward the outer peripheral portion, the sensor segments of the photodetector are arranged such that the projection of a track on the inner peripheral portion in an information recording area, of track projections which move on the sensor segments, does not cross the three divided sensor segments upon rotation of the optical head.

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Yokohama, Japan

Takayuki Asano