Hitachi, Ltd.

Tokinori Furuichi

Kazuhiro Oda

Junichi Ikoma

Seiji Inaba

Keizo Shimizu

Hiroyuki Hayashi

Naomi Nomura

Yuji Hirai

Masao Oguri

Gohshi Jin

Yoshio Miura

Harushige Nakagaki

Hideo Suenaga

Ryuichi Koike

Katunobu Takeda

The present invention provides a single information recording and reproducing apparatus that is used to record data to multiple disks that are to be recorded on using different wavelengths. More specifically, the present invention provides an apparatus that accurately discriminates disk types while preventing disk damage and accidental recording of data during the disk type discrimination operation. The disk type is determined using the intensity of light reflected from the disk. Information is encoded using an encoder corresponding to the disk type. The resulting signal is used to drive a laser corresponding to the disk type, and information is recorded.

Information recording and reproducing apparatus and disk discrimination method thereof

An method to prevent excessive heat generation of the pickup actuator from occurring when a disk has a large eccentricity or planar vibration in a high-speed disk reproducing apparatus using an optical pickup. The disk reproducing apparatus has a status determining arrangement for monitoring a present actuator drive state, an analyzing arrangement for analyzing an output signal of the status determining arrangement, and disk rotational speed switching control arrangement for selecting disk reproducing speeds according to a control signal of the identification means, thereby lowering the reproducing speed when the eccentricity or planar vibration is large. Such invention prevents heat generation of the pickup actuator from occurring because high-speed reproduction can be performed when the eccentricity or planar vibration is small, and reproduction speed can be automatically reduced when the eccentricity or planar vibration is large.

Disk reproducing speed control method and a disk reproducing apparatus

There is provided a chopping, current-control type driver circuit for brushless motor including a circuit for effecting chopping on the basis of a speed/phase error signal, a changeover circuit for changing over the current direction of Hall devices depending upon whether said error signal is positive or negative, switch circuit for supplying power to stator coils on the basis of the Hall device output, a current detection device, and an amplifier serving as an inverting amplifier or a noninverting amplifier depending upon whether the error signal is positive or negative, wherein a negative feedback signal is applied to the error signal in the form of the current value detected by the current detection device in order to control the current flowing through the motor stator.

Current control type circuit for brushless motor

A skip/arm servo system for a video disc player comprises a device adapted to skip a signal sensing element, such as a stylus for detection of information recorded on a disc, in a direction crossing a recording track, a stylus position detector adapted to detect the relative position of the stylus to a cartridge movably mounting the stylus, a comparator comparing the detected relative position with a reference relative position to produce an error output, a cartridge driver responsive to the error output to move the cartridge so as to maintain the stylus in the reference relative position. A setting device is adapted to variably set the reference relative position in accordance with a reproduction mode selected by the operator, whereby a special mode reproduction can readily be accomplished or the stylus can be readily released from a locked groove in the disc.

Skip/arm servo system for a video disc player

A stylus position detecting apparatus in use for a video disc player using a disc of the groove type, detecting plates for detecting leakage components of a high frequency signal supplied from a high frequency signal source and flowing through a flylead, and for reading out a recorded signal in a disc are provided on both sides of the flylead. The leakage signal components detected by the detecting plates are detected to positive and negative directions with respect to a reference voltage. These voltages obtained by the detections are added by an adder, to find a stylus position.

Stylus position detecting apparatus

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Yokohama, Japan

Tokinori Furuichi