JPS5847031B2 - Rotation detection method for disk-shaped recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotation detection device for a disk-shaped recording medium, in which pulses of two types of pulse signals corresponding to the rotation of the recording medium are extracted alternately every other pulse, and the extracted signals are To provide a rotation detection device capable of detecting rotation with high accuracy with a simple configuration by supplying the rotation error signal to one speed error signal detection means and one phase error signal detection means respectively to obtain a rotation error signal. With the goal.

Recording still image broadcasting using the so-called television multiplexing method, in which different IH portions of still image video signals are sequentially inserted into a portion of each vertical retrace period of the current broadcast wave, and broadcast.
As a method for controlling the rotation of a disk-shaped magnetic recording medium in a reproducing device, two control heads are provided in the diametrical direction relative to the rotation axis of the recording medium, thereby controlling the control recorded on each of the two control tracks of the recording medium. A possible method is to detect the signal to obtain a control signal, and use this control signal to control the rotation of the recording medium.

Here, the recording medium for still image video signals generally includes:
The motor rotates with rotational fluctuations that are a combination of rotational fluctuations in the rotational direction caused by torque fluctuations in the motor itself and rotational fluctuations in the direction of axis deviation caused by play or eccentricity of the rotating shaft of the motor.

Therefore, ideally, the rotation should be controlled for both the rotational unevenness in the rotational direction and the rotational unevenness in the off-axis direction, but the video head is not near the control head (the video head is 30° relative to the control head). If the motor is located at a distance of more than 100°, or if a ball bearing or the like is used for the motor bearing, it is not possible to expect much improvement in the rotational unevenness in the direction of misalignment, and only the rotational unevenness in the rotational direction can be improved.

Therefore, for the sole purpose of improving rotational unevenness in the rotational direction, two
The method of obtaining four error signals by supplying two types of pulse signals from a control head to a speed detection circuit and a phase detection circuit, respectively, requires two speed detection circuits and two phase detection circuits, and requires a circuit. It cannot be constructed easily and inexpensively.

In view of the above facts, the present invention alternately extracts every other pulse of two types of pulse signals from two control heads, and supplies these signals to one speed detection circuit and one phase detection circuit, respectively. By having a configuration that obtains two error signals, it is possible to provide a highly accurate rotation detection device with a simple configuration.

FIG. 1 shows the relationship between a magnetic recording medium, a control head, and a video head used in an embodiment of a rotation detection device for a disk-shaped recording medium according to the present invention.

In the figure, reference numeral 1 denotes a magnetic recording medium for still images, on the surface of which control signals 3a and 3b are recorded.

2a and 2b are control heads, and 4a and 4b are video heads, which are installed diametrically above the rotating shaft 6.

5a and 5b are video heads 4a. This is a still image video signal recorded by 4b.

Here, if the recording medium 1 rotates in the direction of the arrow while causing rotational unevenness in the rotational direction and rotational unevenness in the axis deviation direction, and the rotational shaft 6 is displaced to the position 6' at a certain moment, the control head 2
Consider the control signals detected by a, 2b.

When the phase of the control signal 3a detected by the control head 2a is shifted to the position of the φA1 rotation axis 6' when rotating at the position of the rotation axis 6, the phase error of the signal 3a detected by the head 2a is changed to ΔφA1 rotation axis. 6
When the phase of the control signal 3b detected by the control head 2b is shifted to the position of the rotating wheel 6', the phase error of the signal 3b detected by the head 2b is △φB. 2
a.

The phases of the signals detected by 2b are respectively φA+Δ
φA, φB+ΔφB.

The signals detected by the heads 2a and 2b are sent to respective amplifiers as shown in FIG. After being amplified into pulse signals a and b as shown in FIGS. 3A and 3B at a and 7b, they are supplied to pulse shaping circuits 8a and 8b.

Signals a and b are alternately extracted every other pulse by pulse shaping circuits 8a and 8b, resulting in signals c and d as shown in FIG. 9 and a trapezoidal wave generator 18, the signal is supplied to a sample hold circuit and a phase comparator circuit (hereinafter simply referred to as a sample hold circuit) 17, which together with the trapezoidal wave generator 18 constitute a phase detection circuit 10.

Note that the pulse shaping circuits 8a and 8b
The period of alternate extraction is set to be sufficiently smaller than the period of displacement of the position of the rotating shaft 6 due to rotational unevenness in the direction of axis deviation.

The signals c and d are mixed in the speed detection circuit 9 and the sample hold circuit 17, respectively, to form a pulse signal e as shown in FIG. 3E.

This signal e is smoothed in the speed detection circuit 9 to become a signal f (speed error signal) as shown in FIG. 3F, and is supplied to the error signal amplifier 16.

This speed error signal f has a voltage corresponding to the pulse interval of the signal e, and is proportional to the rotational speed of the recording medium 1.

On the other hand, the current broadcasting video signal input from the input terminal 11 has its horizontal synchronizing signal separated by the horizontal synchronizing signal separation circuit 12 and is supplied to the phase comparator circuit 13, where the output oscillation frequency of the voltage controlled oscillator 14 is 63 KHz. is compared with the phase of the signal frequency-divided by the divider 15, and a phase comparison error voltage whose level changes according to the phase difference is extracted, and the oscillation frequency of the voltage controlled oscillator 14 is controlled.

The reference signal from the voltage controlled oscillator 14 is sent to the phase detection circuit 10.
is supplied to the trapezoidal wave generator 18, resulting in a trapezoidal wave signal g as shown in FIG. 3G.

The signal g is supplied to the sample and hold circuit 17 and compared in phase with the signal e shown in FIG. 3E, resulting in a signal h (phase error signal) as shown in FIG.

This phase error signal has a voltage corresponding to the phase error between the phase of the signal e and the phase of the reference signal g, and is proportional to the rotational phase of the recording medium 1.

Now, considering the phase of the signal in the phase detection circuit 10, in the sample hold circuit 17, the phase of the signal C2d of the pulse shaping circuits 8a, 8b and the phase φ0 of the reference signal from the trapezoidal wave generator 18 are different from each other. The signals are compared and a signal with a phase error of 2φ is obtained.

That is, since the phases φA and φB of the signals detected by the heads 2a and 2b, respectively, are the phase φ0 of the reference signal plus the phase error φ due to rotational unevenness in the rotational direction (φI - φB - φ0+φ), the amplifier 7a , the phases of the signals from 7b are (φA+ΔφA)−φ0−φ+ΔφA t
(φB + △φB) - φ0 = φ + △φB, and in this case, generally, the heads 2a provided oppositely 1800
The phase errors due to rotational unevenness in the direction of off-axis of the signals taken out from the heads 2b and 2b are equal in magnitude and have opposite polarities. , the output phase error of the phase detection circuit 10 is substantially the same as that of the amplifier 7a.
, 7b can be regarded as the sum of the phases 2φ.

Therefore, the output signal of the phase detection circuit 10 includes only the phase difference due to rotational unevenness in the rotational direction.

On the other hand, considering the signal in the speed detection circuit 9, the signal e shown in FIG. 3E is a 63 KHz carrier wave whose phase is modulated by the axis shift.

In this case, the 63 KHz carrier wave is the control signal 3a recorded on the control track.

3b and the number of revolutions.

The signal e is obtained by phase modulating the carrier wave due to rotational unevenness in the direction of axis deviation due to axis deviation, as well as phase modulation and frequency modulation due to rotational unevenness in the rotational direction, and the speed detection circuit 9 is a frequency detector. Since only the frequency modulation valve is extracted from the speed detection circuit 9, only the rotational unevenness in the rotational direction is extracted from the speed detection circuit 9.

Therefore, the output of the speed detection circuit 9 includes errors only due to rotational unevenness in the rotational direction.

Note that the speed detection circuit 9 is constituted by a general pulse number discriminator that smoothes the signal e to obtain the signal f.

The phase error signal and speed error signal f thus obtained are smoothed in the amplifier 16 and amplified with their respective gains, and then sent to the motor drive circuit 1 as rotation error signals.
9 to the motor 20, and if the rotation of the motor 20 fluctuates, the level values of the error signals f and h will fluctuate, so that the motor 20 can record the video signal without any rotation error.
control the rotation.

The amplifier 16 is used in a normal servo system, and controls the motor by adding a speed error signal and a phase error signal.

As described above, the rotation detecting device for a disk-shaped recording medium according to the present invention includes a first sensor which is provided diametrically with respect to the rotation axis of the disk-shaped recording medium and outputs a pulse signal proportional to the rotation of the recording medium. and a second pulse signal detection means, means for alternately extracting every other pulse of the pulse signal from the first and second pulse signal detection means, and combining the extracted pulse signals. Means for smoothing this and extracting a voltage speed error signal according to the pulse interval of the synthesized signal, and comparing the phase of the signal synthesized from the extracted pulse signals with the phase of the reference signal to obtain a phase error signal. The speed detection means and the phase detection means each consist of a means for extracting an error signal, and a means for amplifying and mixing the speed error signal and the phase error signal with their respective gains to obtain a rotation error signal. Since only one pulse is needed, it can be constructed easily and inexpensively. Also, since every other two pulses are extracted, rotational unevenness in the rotational direction is not affected by phase errors due to rotational unevenness in the direction of axis misalignment. It has the advantage of being able to perform stable control by controlling only the

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between a recording medium, a control head, and a video head used in an embodiment of a rotation detection device for a disc-shaped recording medium according to the present invention, and FIG. A block system diagram of one embodiment of the rotation detection device, FIGS. 3A to 3H, are diagrams for explaining the operation of the rotation detection method shown in FIG. 2. 1... Recording medium, 2a, 2b... Control head, 3a, 3b... Control signal, 6°6'... Rotating shaft, 8a, 8b ...
... Pulse shaping circuit, 9... Speed detection circuit,
10... Phase detection circuit, 16... Error signal amplifier, 17... Sample hold circuit and phase comparison circuit, 18... Trapezoidal wave generator.

Claims (1)

[Claims] 1. First and second pulse signal detection means provided diametrically with respect to the rotation axis of the disc-shaped recording medium and extracting pulse signals corresponding to the rotation of the recording medium;
means for alternately extracting every other pulse of the pulse signal from the pulse signal detecting means, and a voltage corresponding to the pulse interval of the synthesized signal by synthesizing and smoothing the extracted pulse signals. means for extracting a speed error signal of the speed error signal; means for extracting a phase error signal by comparing the phase of a signal obtained by combining the extracted pulse signals with the phase of a reference signal; and the speed error signal and the phase error. 1. An apparatus for detecting rotation of a disc-shaped recording medium, comprising means for amplifying and mixing signals with respective gains to obtain a rotation error signal.