Matsushita Electric Industrial Co., Ltd.

Masayuki Shibano

Mitsuro Moriya

Shinichi Yamada

Hiroyuki Yamaguchi

Katsuya Watanabe

Yasuaki Edahiro

Yasuhito Soma

An optical disk apparatus for recording and reproducing data to and from an optical disk has a pit area where data are recorded along a track by pits and a groove area where grooves are formed along a track to record data. The optical disk apparatus includes an optical head for projecting a light beam on the optical disk and a photodetector array for receiving the reflected light. A preamplifier is connected to the photodetector array for producing a tracking error signal and an RF signal representing the pits. The tracking error signal is used as a clock signal in flip-flops and the RF signal is used as an initial setting signal, so that the flip-flop produces a signal indicating that the optical head is in the pit area.

Optical disk apparatus with a groove/pit area discrimination circuit

In an information recording and reproducing apparatus, a focusing control system performs a focusing control operation wherein a beam for reproducing signals from a recording surface of a recording medium is focused on the recording surface of the recording medium. The focusing control system includes a differential amplifier for outputting a signal indicating an amount of deviation between the position of a point (a focus of the beam) on which the beam is focused and that of the recording surface of the recording medium, an amplifier for amplifying an output signal from the differential amplifier, and an A/D converter for converting an output signal from the amplifier to a digital signal. The system further includes a focusing control driver for moving the focus of the beam in a direction perpendicular to the recording surface of the recording medium, and a computer or processor for controlling the focusing control driver in response to an output signal from the A/D converter so that the focus of the beam may be positioned appropriately on the recording surface of the recording medium. An amplification factor of the amplifier is reduced during a given period after the focusing control operation is triggered or when the level of the signal from the differential amplifier deviates from a predetermined range.

Focusing control system for use in an information recording and

In a tracking control apparatus, a tracking error signal having a level of a positional shift of a beam of light projected through an optical head onto a recording medium is detected based on a reflected light from the recording medium, and the optical head is controlled so that a beam of light scans on the track to be recorded or reproduced based on the tracking error signal. Offset values of the tracking error signal on adjustment tracks which are predetermined among a plurality of tracks of the recording medium are detected, and then coefficients of a predetermined approximate equation approximately representing an offset value characteristic on the track based on the detected offset values are calculated. Further, an offset value corresponding to the track to be recorded or reproduced is calculated based on the first approximate equation with the calculated coefficients, and an offset value of the tracking error signal is corrected based on the calculated offset value.

Tracking control apparatus for correcting tracking error signal

The temperature around the tracking actuator is detected with a temperature sensor, and the characteristics of an equivalent digital filter are changed to match the characteristics of the tracking actuator at the detected temperature. When the temperature is low, a current is applied to the focus control coil to raise the temperature of the tracking actuator, thereby essentially matching the transfer functions of the tracking actuator and the equivalent filter.

Tracking control apparatus for an optical disk device

A tracking control target position adjusting track is provided on a recording carrier, where the track contains a preliminarily recorded first position-adjusting signal adjoining one side of track and a second position-adjusting signal adjoining the other side of track. While the reproduction position set on the target-position adjusting track, the tracking control apparatus adjusts the tracking-control target position based on reproduced first and second position-adjusting signals. As a result, the tracking control apparatus can precisely adjust the tracking control target position, thus providing quite satisfactory interchangeability with the corresponding apparatuses.

Tracking-control target-position adjustment method

A velocity detection method and an apparatus therefor, in which the relative velocity between a light beam and tracks is detected on the basis of a period for which the light beam crosses the tracks, and under the condition that the light beam has passed by a predetermined position on the way to the target track, the detected relative velocity is compared with a predetermined velocity value so that when the detected relative velocity is larger than the predetermined velocity value the detected relative velocity is invalidated on the assumption that erroneous detection is generated by noise.

Velocity detection method and apparatus therefor

A method of and an apparatus for setting into operation a focusing control for bringing a focal point of a beam onto a recording surface of an optical disk such that the beam reproduces signals from the recording surface, in which a relative velocity between the focal point and the recording surface is detected on the basis of an output of a focusing error detection device for detecting a gap between the focal point and the recording surface and velocity of a displacement device for driving the focal point in a direction perpendicular to the recording surface is controlled on the basis of the detected relative velocity such that focusing control can be stably set into operation by starting focusing control after controlling the relative velocity.

Method of and apparatus for setting focusing control into operation

In an apparatus which focuses a light beam on a rotating recording medium in order to record and/or reproduce information, the light beam on the recording medium is focus controlled so that a prescribed focusing condition is accomplished. By storing a relation between a target position of focus control and the amplitude of a reproduced signal and by obtaining an optimum target position of focus control is accordance with such stored information, the target position of the focus control can be precisely and quickly adjusted, thereby properly controlling the light beam to be focused on the recording medium.

Method and apparatus for adjusting target position of focusing of light

In an apparatus for searching a desired track of a recording carrier by transferring and controlling the reproduction position of the pickup for reproducing the signal recorded on a recording carrier on the basis of reference transfer information, the traveling load is measured, and the value of the reference transfer information is corrected according to this measured value, so that the desired track may be searched stably. The transfer motor is driven so that the reproduction position may move at a constant velocity, and the traveling load is measured. The transfer motor is driven so that the moving speed of the reproduction position or the time for moving a specified distance may be predetermined specific value, and by this driving signal, the value corresponding to the traveling load is determined.

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Izumisano, Japan

Masayuki Shibano