Victor Company of Japan, Limited

Yasushi Sano

Isami Kaneda

Susumu Sakakibara

Hiroyuki Sugiyama

Ryozo Abe

A tracking servo circuit corrects for closed loop gain variations due to wear of the disc, the width of the electrode of the reproducing stylus, etc. The disc contains an information track bounded by servo tracks used to derive a tracking error signal. This tracking error signal is supplied to an AGC circuit after being filtered and detected. The gain of the AGC circuit decreases as the voltage level of the tracking error signal increases. The tracking error is also supplied to an electric-mechanical conversion system after an oscillatory signal of constant frequency and amplitude is added to it. The oscillator signal is used to stabilize the gain of the servo loop. The electric-mechanical conversion system corrects the position of the stylus in response to these signals.

Tracking servo with closed loop gain correction

A reference signal detection circuit in a rotary recording medium reproducing apparatus has a reproducing transducer for reproducing an information signal recorded in a rotary recording medium and reference signals for tracking servo recorded for every predetermined period, from the rotary recording medium rotating at a predetermined rotational speed, and a tracking servo circuit for obtaining a tracking servo signal from the reference signals and performing a tracking servo operation according to the tracking servo signal thus obtained. The detection circuit further comprises a single rectifying and smoothing circuit for rectifying and smoothing the reproduced reference signals obtained for every predetermined period. The detection circuit has a lowpass filter characteristic wherein the cutoff frequency is within a frequency range between one third and twice the gain crossover frequency of the tracking servo loop.

Reference signal detection circuit in a rotary recording medium

A rotary recording medium reproducing apparatus reproduces a rotary recording medium in which one and the other of first and second reference signals are alternately recorded every track turn between each track turn of a main information signal track. The reproducing apparatus comprises a reproducing transducer having a reproducing element for reproducing the main information signal and the first and second reference signals at both sides of the main information signal track from said rotary recording medium, where the reproducing transducer has a tracking control mechanism for controlling tracking of the reproducing element, a separation circuit for respectively separating the first and second reference signals from a signal reproduced by the reproducing transducer, a wave detection circuit for respectively wave-detecting the separated reference signals, a time constant circuit for eliminating an unwanted component of an output signal of the wave detection circuit and holding a required signal, a tracking control signal applying circuit for obtaining a tracking control signal from an output signal of the time constant circuit and applying the tracking control signal to the tracking control mechanism of the reproducing transducer, and an interrupting circuit provided at a stage before the time constant circuit, for interrupting transmission of the reproduced reference signals during a mode in which a tracking control operation is not performed.

Rotary recording medium reproducing apparatus with a tracking control

A transfer control device for a reproducing transducer in a rotary recording medium reproducing apparatus having a reproducing transducer for reproducing recorded signals from a rotary recording medium and a driving motor for transferring said reproducing transducer on said rotary recording medium comprises a micro-computer having first and second output ports, where the first output port produces a signal of a pulse form which repeats high-level and low-level periods during a normal-speed transferring mode, and the second output port produces a continuous high-level or low-level signal according to the transferring mode so that a combination of a predetermined level is obtained between the output signal from the first output port, a square wave signal generating circuit applied with the output signal from the first output port of the micro-computer, where the square wave signal generating circuit is triggered to produce a predetermined square wave signal when applied with the signal of a pulse form and not triggered when applied with other signals of constant level, and a switching circuit applied with the output signal from the first and second output ports of the micro-computer, to switch over a plurality of input terminals according to the levels of the applied signals and pass the input terminal voltage through to an output side as an output voltage. The switching circuit supplies the output voltage thus obtained to the driving motor.

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Yamato, Japan

Yasushi Sano