JPH0357548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention mainly relates to an improvement in a speed control device for a reproducing machine whose recording medium is a rotating disk on which digital signals are recorded concentrically or spirally at a constant linear velocity.

FIG. 1 shows an example of this type of device.

In the figure, 1 is the bit period T ₀ longest inversion interval
A disk on which a digital signal Tmax (Tmax=11×T ₀ ) is recorded spirally at a constant linear velocity V, 2
3 is a pick-up (hereinafter referred to as PU) that reads a recorded digital signal from disk 1 and converts it into a playback signal that is an electric signal; 3 is a position detector that outputs a position signal indicating the radial position (radius IR) of PU 2;
4 is a pulse generator that outputs N pulses per rotation of disk 1, and 5 is a frequency F ₁ based on the above position signal.
A computing unit that outputs a reference servo signal given by the following formula.

F ₁ =V×N/2π×r (1) 6 is a phase comparator that compares the phase difference between the reference servo signal and the pulse, 7 is an amplifier, and 8 is a motor.

The output pulses of the pulse generator 4 form a phase synchronized system consisting of the pulse generator 4, phase comparator 6, amplifier 7, and motor 8, with reference to a reference servo signal of frequency F ₁ given by one set. . That is, the pulse frequency F ₂ is the same as F ₁ .

In FIG. 1, the relative linear velocity V' of the disk 1 with respect to the PU 2 is given by the following equation.

_{V ' = 2πr} can be played.

However, even if the digital signal during recording is the same, when the recording linear velocity V becomes V+ΔV, the bit period T ₀ ' of the reproduced signal becomes T ₀ '=T ₀ ×V/V+ΔV≠T ₀ ( The method shown in FIG. 1 has the disadvantage that it cannot be reproduced correctly because ΔV≠0).

In order to eliminate the drawbacks of the conventional system, the present invention attempts to control the rotational speed of the disk 1 as directly as possible from the reproduction signal so that the bit periods T ₀ ' and T ₀ of the reproduction signal can be adjusted.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the present invention, in which 10 and 11 are first and second zero-cross detectors that output reset signals at the rise and fall of the reproduced signal, respectively, and 12 and 13 are first and second zero-cross detectors, respectively. 14 is a comparator that outputs the larger of the two inputs; first and second ramp generators that are reset by reset signals from the zero-cross detectors 10 and 11 of 2 and whose output voltage increases over time; , 15 is a peak hold circuit that holds the peak value of the output of the comparator 14 and outputs a speed signal that drops with a time constant τ ₀ ; 16
1 is a differential amplifier that outputs the error between the speed signal and the reference voltage, and 17 is a reference voltage source.

Also, during digital signals, Tmax is
Assume that the is inserted twice consecutively.

The operation of FIG. 2 will be explained below with reference to the drawings.

FIG. 3 shows voltage waveforms at various parts in FIG. 2 during stable rotation, where A is a reproduction signal, BC is a reset signal from the first and second zero cross detectors 10 and 11, respectively, and DE is a reset signal from the first and second zero cross detectors 10 and 11, respectively. 2 lamp generators 12,
13, F is the output of the comparator 14, and G is the speed signal.

FIG. 3 shows a state in which the signal is being reproduced at an approximately normal speed, but at the start of rotation of the motor 8, that is, the disk 1, the reproduction signal A shown in FIG.
The reset signal BC has a waveform extending in the time axis direction. The rate of voltage rise of the ramp generators 12, 13 is constant. Therefore, the peak values of each waveform of DEF in FIG. 3 are increased compared to this diagram, and the voltage of the speed signal G is also increased. Along with this, the outputs of the differential amplifier 16 and the amplifier 7 also increase. Therefore, the speed of the motor 8 also increases.

Conversely, when the position of PU2 suddenly moves from the inner circumference to the outer circumference (when the value of radius r increases rapidly), the playback speed of the recorded signal becomes higher than in the normal case shown in Figure 3. There is. Therefore, contrary to the above case, the reproduction signal A and the reset signal BC are
Compared to the case shown in the figure, the time axis is condensed. Therefore, the peak value of each waveform in FIG. 3 DEF decreases, and the voltage of the speed signal G also decreases. Accordingly, the voltage applied to the motor 8 decreases, and the rotation also decreases.

As described above, according to the embodiment shown in FIGS. 2 and 3, even when the linear velocity V during recording can be selected within a certain range, the linear velocity is almost normal regardless of the linear velocity V. You can play the signal with In addition, compared to the method shown in FIG. 1, this method has the advantage that it does not require the position detector 3, which requires relatively high mechanical precision.

Note that if each waveform in FIG. 3 DEFG is considered to be a digital value, the ramp generators 10 and 11 can also be configured by counters.

Further, although the above description has been made regarding a disk-shaped one, the tape can also be applied to a capstan motor or the like.

As explained above, according to the present invention, the rotational speed of the rotating body can be directly controlled by the reproduction signal.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a conventional speed control circuit.
FIG. 2 is a block diagram showing one embodiment of this invention.
FIG. 3 is a diagram showing waveforms of various parts of the embodiment shown in FIG. 2. 1... Disc, 2... PU, 3... Position detector,
4... Pulse generator, 5... Arithmetic unit, 6... Phase comparator, 7... Amplifier, 8... Motor, 10, 1
1...first and second zero cross detectors, 12,
13...first and second lamp generators, 14...
Comparator, 15... Peak hold circuit, 16...
Differential amplifier, 17...Reference voltage source.

Claims (1)

[Claims] 1. The longest inversion interval (Tmax) is the bit period (T ₀ )
A reproduction signal reproduced from a recording medium on which a digital signal regulated according to the relationship Tmax=n×T ₀ (n is a natural number) is input, and at the first and second polarity change points of the reproduction signal. first and second zero cross detectors that output first and second reset signals; and first and second ramp signals that are reset by the first and second reset signals and whose values increase over time. a comparator that selects the larger of the first and second ramp signals; a peak hold circuit that holds the peak value of the output waveform of the comparator; and a means for comparing the peak value with a reference signal to create a control signal for a drive system that drives the recording medium, so that even when the recording density of the digital signal recorded on the recording medium changes, the bits of the reproduced signal can be adjusted. A speed control device characterized in that it is configured to control the speed of a recording medium so that the transmission speed is constant.