Yamaha Corporation

Mamoru Horino

Norio Tomisawa

Kazuhiko Honda

Optical disk recording device includes a beam projection section for projecting a light beam onto a write-once optical disk, and a photodetector having two light receiving surfaces divided in a radial direction of the optical disk for detecting reflected light from the optical disk, and wobble-signal reproduction circuitry for reproducing a wobble signal on the basis of reflected light detection signals output from the two light receiving surfaces of the photodetector. The wobble-signal reproduction circuitry includes peak-holding circuits for, when the optical disk device is in a reproduction mode, detecting and holding respective upper envelopes of the two light detection signals from the photodetector. The wobble-signal reproduction circuitry also includes holding circuits for, when the optical disk device is in a recording mode, detecting respective lower envelopes of the two light detection signals from the photodetector. The reproduction circuitry further includes circuits for switching, between the reproduction mode and the recording mode, the light detection signals to be held by the holding circuits, and a subtraction circuit for performing a subtraction between values held by the holding circuits. Thus, the wobble-signal reproduction circuitry is allowed to produce, with a simple structure, a high-quality wobble signal free of high-frequency signal components.

Optical disk recording device

An error signal detection circuit in a servo control device comprises a reference signal generation circuit for selectively generating reference signals of different periods, each having a slope which changes from a reference value at a substantially constant gradient, an error detection timing generation circuit for generating timing of detection of an error signal of an object of control, an error signal detection circuit for generating an error signal by detecting the value of a reference signal generated by the reference signal generation circuit at a timing provided by the error detection timing generation circuit, and a slope varying circuit for varying the slope of the reference signal in accordance with the period of the reference signal. By changing the gradient of the slope of the reference signal in accordance with the reference period, the ratio of change of the error signal output to the error can be maintained substantially constant so that the gain of the servo loop can be maintained substantially constant and optimalization of the servo system can thereby be realized.

Error signal detection circuit in a servo control device

A magnetic recording and reproducing device such as an R-DAT performs fast search for detecting a desired reproducing position during fast feeding or rewinding of recorded tape. The magnetic recording and reproducing device comprises a rotary head incorporating a rotary drum for recording and reproducing an input signal by tracing a magnetic tape, a rotary drum drive circuit for driving the rotary drum for rotation, a tape reel drive circuit for driving a tape reel for running a magnetic tape and a relative speed detection circuit for detecting relative speed between the magnetic tape and the rotary head. The rotary drum is driven in such a manner that, upon receiving a fast search order, the relative speed substantially becomes a predetermined speed without increasing the tape speed. After reaching of the relative speed substantially to the predetermined speed, the rotation speed of the rotary drum or the tape reel is changed gradually to a speed used during fast searching and the rotation speed of the tape reel or the rotary drum is changed against the change in the rotary drum or the tape reel after reaching of the relative speed to the predetermined speed while maintaining the relative speed substantially at the predetermined speed. The device can read information for fast search such as start ID, music number and time data recorded on the tape is a stable manner from the start of the search.

Fast search device in a magnetic recording and reproducing device

A rotation control device for a rotary head in a rotary head type magnetic recording and reproducing device such as an R-DAT cmprises a rotary head including an FG (frequency generator) for producing a signal at a period determined by equally dividing one rotation of a drum and a PG (phase generator) for detecting a rotation reference position of the drum, a circuit for generating a PG reference signal as a reference signal for a PG detection signal provided by the PG, a circuit for generating an FG reference signal as a reference signal for an FG detection signal provided by the FG, and a control circuit for controlling rotation phase of the drum to a predetermined state by controlling rotation of the drum in accordance with a phase error between the PG detection signal and the PG reference signal and a phase error between the FG detection signal and the FG reference signal. Rotation of the drum is controlled in accordance with the two phase errors in such a manner that the PG detection signal is locked with the PG reference signal at a predetermined phase difference and the FG detection signal is locked with the FG reference signal at a predetermined phase difference whereby the phase of rotation of the drum is controlled to a predetermined state.

Rotation control device for a rotary head in a magnetic recording and

A PWM circuit for generating a PWM wave which is pulse-width modulated in response to binary information and is used for a signal such as a motor driving signal in an R-DAT (rotary head type digital audio tape recorder) comprises a circuit for dividing binary information such as a motor speed error signal provided for generating a PWM wave into plural bit groups and generates PWM waves corresponding to numerical values of these plural bit groups, and a circuit for weighting the generated PWM waves in an analog manner at a ratio corresponding to orders of the respective bit groups and adding the weighted PWM waves. Since binary information is divided into plural bit groups, the bit number of each bit group is small so that the period of PWM wave can be shortened without reducing the quantization bit number of the binary information or shortening reference clock period whereby accuracy of an error signal can be improved when the invention is applied to, e.g., a motor drive device.

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Hamamatsu, Japan

Mamoru Horino