JPS60131678A - Tracking device - Google Patents

Abstract

PURPOSE:To stabilize a tracking device in level by sampling an envelope signal produced from a reproduction signal with a sampling pulse produced from a horizontal synchronizing signal and producing an error signal to give tracking to a reproduction head. CONSTITUTION:The detection signal fed from a reproduction head 1 is amplified by a preamplifier 2, and one of both signals is supplied to a BPF3 with the other signal applied to a frequency demodulator 5 respectively. The reproduction output signal fed from the head 1 receives the variance in amplitude level, and the envelope signal fed from an envelope detecting circuit 4 is supplied to a control circuit 8. While the signal of the demodulator 5 is supplied to a horizontal synchronizing signal separating circuit 6. The pulses phi1 and phi2 are obtained by a sampling pulse producing circuit 7 and supplied to the circuit 8. The circuit 8 samples and holds the envelope signals of the positions of horizontal synchronizing signals b1 and b1' synchronously with pulses phi1 and phi2 and compares the amplitude values of these envelope signals. Then a control signal is supplied to a piezoelectric element drive circuit 9 so that the head 1 is moved in the direction where the level of the envelope signal is increased. Thus it is possible to obtain a tracking error signal at a stable level and high S/N.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a playback device that uses a playback head to play back an image signal or the like from a recording medium, in which a signal recorded on the recording medium is detected and reproduced. The present invention relates to a tracking device that causes a playback head to automatically track a recording track on a record carrier.

(Prior art) An envelope of a signal detected from a reproducing head for the purpose of efficiently detecting a signal when reproducing while sending a head carrier supporting the reproducing head at predetermined pitch intervals in a direction perpendicular to the recording track of a record carrier. A tracking device has already been proposed in which the reproducing head performs a tracking operation so as to be positioned in the direction where the amplitude is maximum, that is, directly above the recording track of the record carrier.

This tracking device uses a playback head to detect frequency-modulated image signals recorded on a record carrier, and applies them to a low-pass filter circuit until the amplitude of the envelope signal from the low-pass filter circuit is at its maximum. It was determined that the playback head was located directly above the recording track of the record carrier by detecting the position where the image signal fell. However, the image signal consists of high and low brightness parts depending on the subject. When such an image signal is frequency modulated, for example, high brightness portions are converted to high frequencies, and low brightness portions are converted to low frequencies. On the other hand, the frequency characteristics of the reproduction circuit device that reproduces the signal detected from the reproduction head do not necessarily correspond strictly to the frequency consistency of the signal detected from the reproduction head, and therefore The signal level fluctuates due to the influence of the frequency characteristics of the reproduction system. As mentioned above, in order to position the playback head directly above the recording track of the record carrier, the change in the amplitude of the envelope signal is used as a judgment criterion, and the position is controlled in the direction in which the amplitude increases, so the level of the envelope signal is If the frequency characteristics of the reproduction system fluctuate, the tracking operation cannot be performed smoothly.

(Purpose) The present invention solves the drawbacks of the prior art as described above, and is aimed at solving the problem of the above-mentioned drawbacks of the prior art. It is an object of the present invention to provide a tracking device that has a stable level even when the tracking error is detected and can obtain a plurality of tracking error detection signals within one vertical period.

(Example) (Figures 1 to 4) Hereinafter, the means taken by the present invention to achieve the above object will be illustrated and explained based on the drawings.

The tracking device of the present invention is applicable not only to those in which the record carrier has a disk-like or tape-like shape, but also to magnetic, capacitive, and magnetic types.
It can also be applied to optical record carriers.

In the following embodiments, an example in which the reproducing head is magnetic and the record carrier is disk-shaped will be described.

FIG. 1 shows an embodiment of the tracking device of the present invention,
Figure 2 shows the relationship between the gain characteristics of the band filter, the composite image signal, and the frequency of FM modulation, and Figure 3 shows the horizontal synchronization signal and the synchronization signal formed from this signal.
FIG. 4 shows another embodiment of the present invention.

In FIG. 1, 1 is a magnetic reproducing head, and 2 is a magnetic reproducing head.
is a preamplifier that detects a signal recorded on a disc-shaped record carrier (not shown) using a reproducing head l and amplifies the signal. 3 is a bandpass filter whose frequency vs. key characteristic is as shown in waveform a in Fig. 2, and the frequency f
Passes frequencies near t. To further explain FIG. 2, b is a modulation signal and indicates a composite image signal consisting of horizontal synchronization signal bl+J' and image signal, and fl corresponds to the horizontal synchronization signal S and b1' of the composite image signal. It is a carrier frequency, and f2 is a carrier frequency corresponding to white beak b2 of the image signal. The above-mentioned pantone filter 3 has a frequency f corresponding to the sync step.
! Outputs the band near .

4 is an envelope detection circuit, which is a pantone filter 3.
It outputs an envelope signal of the output signal from the control circuit svC and inputs it to the control circuit svC. Reference numeral 5 denotes a demodulator which receives the output signal from the preamplifier 2 that amplifies the reproduced signal detected from the reproducer rad l, demodulates the frequency modulated signal, and converts it into the original image signal.

Reference numeral 6 denotes a horizontal synchronization signal separation circuit, which extracts only the horizontal synchronization signal from the composite image signal from the demodulator 5. Reference numeral 7 denotes a sampling signal forming circuit, which forms sampling pulses φ1 and φ2 shown in FIG. 3(b) and (c) from the horizontal synchronizing signal shown in FIG. Enter as russ. Since the control circuit H receives an envelope signal existing near the frequency f1 of the horizontal synchronizing signal S...b1', the horizontal synchronizing signal Grus φ! from the sampling and pulse forming circuit 7 is inputted. and φ2 are input, the envelope signal in which the horizontal synchronizing signal bl+b% is located is sampled and held from the composite image signal, the difference between the two sample and hold values is detected, and the envelope signal from the envelope detection circuit 4 is detected. Envelope (g
The tracking operation is performed by displacing the rad l toward reproduction in the direction in which the amplitude of the signal increases. 9 is a piezoelectric element drive circuit, and 10 is a piezoelectric element provided on a head carrier (not shown) on which the reproducing head l is mounted. The piezoelectric element driving circuit 9 receives a control signal from the control circuit 8, and sends the head carrier carrying the reproducing head 1 at a predetermined pitch in a direction perpendicular to the recording track of the record carrier, and also applies a voltage to the piezoelectric element 10. In addition, a mechanical strain is generated, this mechanical strain is transmitted to a support (not shown) that supports the reproducing head 1, and the reproducing head 1 is biased to be positioned directly above the recording track of the record carrier.

The operation of the tracking device having such a configuration will be explained.

A detection signal from a reproducing head 1 is amplified by a preamplifier 2, and one of its outputs is applied to a bandpass filter 3, and the other output is applied to a frequency demodulator 5.

The band filter 3 has a frequency e and a number f l shown in FIG.
Extract the carrier frequency near . The reproduction output signal from the reproduction head 1 is vibrated in the left-right direction with respect to the recording track direction, and therefore is subject to fluctuations in amplitude level, and the envelope detection circuit 4 outputs an envelope signal. This envelope signal is input to the control circuit 8. On the other hand, the signal converted into the original image signal by the frequency demodulator is input to the horizontal synchronization signal separation circuit 6, and the third
Only the horizontal synchronizing signal shown in FIG. 3(a) is separated and sent to the sampling signal forming circuit 7 to obtain sampling signals φ1 and φ2 shown in FIG. 3(b) and (c), which are then applied to the control circuit. Enter 8. The control circuit 8 generates a sampling pulse φ
Out of the envelope signals from the envelope detection circuit 4 in synchronization with l and φ2, the envelope signals where the horizontal synchronizing signals b1 and b1' shown in FIG. circuit 4
Move the playback head in the direction where the envelope signal from
A suppressing signal is applied to the piezoelectric element drive circuit 9 to move the piezoelectric element drive circuit 9.

In the above embodiment, the pantone filter 3 that extracts a frequency band near frequency 11 is explained, but the same effect can be obtained by using a low bass filter that extracts signals below frequency f+. .

In addition, although the case where sampling is performed using two synchronizing signals φ1 and φ2 in the horizontal synchronizing signal train is explained, the sampling is not limited to two, and the response speed of the tracking system is taken into account, and the range that can perform optimal control is It is also possible to obtain a number of sampling pulses within one vertical period and sample them simultaneously.

FIG. 4 shows another embodiment of the present invention, which differs from the one shown in FIG. 1 in that the band filter 3 is omitted; It can achieve the same purpose and effect. Even without the band filter 3, the sampling pulses φ1 and φ2 from the horizontal synchronizing signal train shown in FIG. Since the envelope signal where the horizontal synchronization signal is located is sampled from the envelope signal from the envelope detection circuit 4 in synchronization with A level tracking error signal can be detected. Particularly, the effect of this embodiment, which brings the synchronization signal to the low frequency side, is significant.

In the embodiments shown in FIGS. 1 and 4, the magnetic head is used for reproduction. However, when a device that performs recording or reproduction using a single magnetic head is used in the reproduction mode, Of course, the tracking device of the present invention can also be applied to.

(Effects) As explained above, according to the present invention, the envelope signal of the playback signal of the playback head is synchronized with the sampling pulse obtained from the horizontal synchronization signal and is sampled, so the influence of information signals other than the horizontal synchronization signal It is possible to detect multiple signals of only the horizontal synchronization signal part in a composite image signal, etc., which is reproduced without being affected, within one vertical period, and it is also possible to obtain a tracking error signal with a stable level and a good S/N ratio. can.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the tracking device of the present invention, FIG. 2 is a waveform diagram showing the form of frequency modulation of this embodiment and the gain characteristics of the pantone filter used in this embodiment, and FIG. The figure is a waveform diagram showing the sampling signal obtained by the horizontal synchronizing signal separation circuit and sampling signal forming circuit used in this embodiment.
4 shows a horizontal synchronizing signal train, FIG. 4(b) and (c) show waveform diagrams of a sun-silling-gurus train, and FIG. 4 shows a circuit A' lock diagram of another embodiment of the present invention. In the figure, 1 is the playback head, 2 is the preamplifier, and 3 is the band i.
4 is an envelope' detection circuit, 5 is a frequency demodulator, 6 is a horizontal synchronizing signal separation circuit, 7 is a sampling pulse forming circuit, 8 is a control circuit, 9 is a piezoelectric element drive circuit, and 10 is a piezoelectric element. .

Claims (3)

[Claims] (1) A playback head, an envelope forming means for forming an envelope signal from the playback signal of the playback head, and a sampling device for obtaining sampling and pulse from the horizontal synchronization signal.
1. A tracking device comprising: an envelope forming means; and a control means for sampling an output signal from the envelope forming means using the sampling signal to form a tracking error signal and causing a reproducing head to perform a tracking operation. (2) Claim (1) further comprising a low-pass filter that passes a frequency component lower than the frequency of the horizontal synchronizing signal of the composite image signal, which is provided before the envelope forming means.
Tracking device as described in section. (3) The tracking device according to claim (1), further comprising a bandpass filter that passes frequency band components of the composite image signal and is provided upstream of the envelope forming means.