JPS5833384A - Automatic tracking device of magnetic recorder and reproducer - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture of high quality, by giving the synchronizing wave detection and the phase compensation to the envelope of the reproduced signal of a magnetic head and maintaining the position of head at the center of a track in an average. CONSTITUTION:A magnetic head 1 is supported by an electro-mechanical transducer 4, and the signal of the integer-fold value of the field frequency is applied to the transducer 4 with each scan of the azimuth recorded recording track and in the reproduction mode. Then the envelope of the reproduced signal of the head 1 undergoes the synchronizing wave detection through an envelope wave detecting circuit 5. The output of this wave detection is fed to an LPF7 to obtain a tracking error signal. This signal is added 9 with the output signal of an oscillator 3 after the phase compensation 8. Thus the position of the head 1 is controlled to be set at the center of the track in an average.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an auto-tracking technique in a magnetic recording/reproducing device.

Magnetic recording/reproducing devices are used in many technical fields because they can extremely easily record and reproduce information signals.It is well known that they are particularly widely used in consumer applications.

Incidentally, as the demand for high-density recording of information on magnetic recording media increases, the recording trace width (track width) has been narrowed. However, increasing the density in this direction is limited by mechanical accuracy in the drive system of the magnetic recording medium, the drive system of the magnetic head, and the like. This point is particularly problematic in consumer magnetic recording and reproducing apparatuses (hereinafter abbreviated as 1) which require low cost.

In order to achieve high-density recording and reproduction on magnetic recording media, in addition to narrowing the recording trace width, the magnetic head is controlled by a tracking servo system during reproduction so that the magnetic head always accurately scans over the recording trace. So-called auto-tracking technology is required.

Therefore, conventionally, the magnetic head is supported by an electromechanical transducer, and by driving this electromechanical transducer with a sine wave signal, the magnetic head is vibrated in the width direction of the recording track and traced. The obtained reproduced signal is processed to obtain a displacement detection signal corresponding to the amount of deviation of the magnetic head in the width direction of the recording track, and this displacement detection signal is used to displace the electromechanical transducer. A method has been proposed in which the magnetic head is automatically returned to the center position of the recording track.

However, when a magnetic head with an azimuth angle is used, such as in a high-density azimuth recording system, problems arise with the above-described method.

The situation is shown in FIGS. 1 and 2. Note that FIG. 1 is an explanatory diagram showing the tracing state of the video head when the auto-tracking device is in operation, and FIG. 2 is an explanatory diagram showing the time-axis fluctuation state of the reproduced signal that occurs in that case as well.

In FIG. 1, 1 is a magnetic head, 2 is a magnetic tape, T is a recording track, and R is a recording track on the magnetic tape 2 that the magnetic head 1 reproduces.

In this way, the magnetic head 1 is vibrated perpendicularly to the recording track T. For example, if the magnetic head 1 is displaced upward with respect to the recording track T as shown by the dotted line in FIG.
The reproduced signal is delayed by a time corresponding to the distance X due to the presence of the azimuth angle α. Therefore, when the magnetic head is vibrated and reproduced, the demodulated video Shingo is reproduced with its time axis fluctuating. Fluctuations in the time axis result in so-called jitter, which is the shaking of the playback screen, and so-called color banding, which is the fluctuation in hue.

The present invention also applies to a magnetic recording and reproducing apparatus that performs recording and reproducing after converting a color signal in a video signal to a low frequency and frequency modulating a luminance signal. An object of the present invention is to provide an auto-tracking device that obtains a reproduction signal that can substantially reduce deterioration of images and reproduce images of good quality.

In order to achieve the above-mentioned object, in the present invention, by driving an electric/mechanical transducer with a sine wave signal, a magnetic head is obtained from a reproduced signal obtained by tracing the magnetic head while vibrating in the width direction of the recording track. In an auto-tracking device that detects the amount of head misalignment and controls the relative position of the magnetic head to the video track according to the amount of misalignment, the sine wave signal is set to an integral multiple of the field frequency to visually improve the image quality. Measures were adopted to reduce deterioration.

Next, an embodiment of the present invention will be described using a helical scan 2-head VT.
I will explain in detail when applied to R.

The VTR mechanism has become a well-known technology and
Ru. Therefore, I will avoid explaining it again.

FIG. 6 I, n, and m show the wobbling magnetic head 1.
The relationship between the scanning locus R and the recording track T is shown. I in FIG. 3 indicates the case where the magnetic head 1 passes through the center of the recording track T. (■ in FIG. 3 indicates the case where the center of the magnetic head 1 is displaced in the direction indicated by the arrow). ing.

3 shows a case where the center of the magnetic head 1 is displaced in the direction indicated by the arrow. The magnetic head 1 actually reproduces only the shaded portion of the recording track 2. The shape of the envelope signal of the reproduced signal approximately corresponds to the shape of the shaded area in FIG. Therefore, a modulation signal corresponding to the relative position between the magnetic head 1 and the recording track T can be obtained.

The present invention detects a servo signal from this modulated signal and performs an auto-tracking operation. The principle of this system will become clear from the description of FIG.

FIG. 4 is a block diagram showing one embodiment of the present invention. Please refer to FIG. The configuration of the present invention includes an oscillator 3. Electrical/mechanical conversion element 4 that supports the magnetic head 1. Envelope detection circuit that extracts only the fluctuation component of the reproduced signal from the modulated signal5. Synchronous detection circuit that performs synchronous detection using a wobbling signal that is a fluctuating component 6. Low-frequency three-wave circuit that converts the synchronously detected signal into a stable tracking error signal7. Phase compensation circuit for compensating the phase of the loop 8. It consists of an adder 9 that adds the tracking error signal and the wobbling signal.

Next, the operation shown in FIG. 4 will be explained with reference to the timing chart shown in FIG. A wobbling signal of frequency f generated by an oscillator 3 causes the electro-mechanical conversion element 4 to wobble. The signal reproduced by the magnetic head 1 is shown in FIG. 5(a). The reproduced signal modulated by the wobbling signal has a waveform superimposed on the envelope. Here, 1 in (a) of FIG. Il,m correspond to the reproduced signal waveforms when the magnetic head 1 and the recording track T are in the positional relationship I, n, III in FIG.

The envelope detection circuit 5 extracts only the fluctuating components of the reproduced signal from the waveform shown in (a) of FIG. 5 and shows the waveform shown in (b) of FIG.
waveform. Next, in the synchronous detection circuit 6, synchronous detection is performed using the wobbling signal (e). The synchronously detected waveform (FIG. 5(d)) is passed through the low-frequency three-wave circuit 7 to obtain the tracking error signal shown in FIG. 5(e).

This tracking error signal is based on the relative position 1..1 between the magnetic head 1 and the recording track T. Il, I[Depending on I, the voltage becomes zero, positive, or negative. Next, the phase compensation circuit 8 compensates the phase of the servo loop. Then, the adder 9 superimposes the signal on the wobbling signal and controls the head position so that it is centered on the track on average.

Here, the wobbling signal of frequency f is selected to be an arbitrary positive integer multiple of the field frequency fl.

In other words, the relationship is f-N@fl (N is a positive integer). This relationship is actually obtained by the method shown below. In an NTSC two-head helical scan VTR, the field frequency (60H
The magnetic head is switched between the two channels A- by a 50 Hz switch change signal synchronized with the channel A-. Therefore, in order to satisfy the above relationship, the wobbling signal oscillator 5 is synchronized with the 30 Hz switch switching signal.

In this way, jitter and color banding caused by wobbling can be reduced on the playback screen. The reason for this will be explained using FIG. In the figure, TA and TB are tracks with azimuth angles α and -α.

When the head 1 on the track TA is vibrated perpendicularly to the recording track TA as shown by the arrow, the reproduced signal is transmitted over a distance of Xt.
will be delayed by a time corresponding to . By the way, when the head 1 is vibrated in the same direction on the adjacent recording track TB, since the azimuth angle is opposite to TA, it advances by a time corresponding to the distance x1, and therefore, the jitter caused by vibrating the magnetic head 1 The negative effects of color banding on image quality are reversed for each field, so they are canceled out by the integration effect, and as a single frame image, image quality deterioration due to jitter and color banding is substantially reduced, resulting in good reproduction. You can get the image.

As described above, according to the present invention, deterioration in image quality due to jitter and color banding caused by vibrating the magnetic head can be reduced, and the color signal in the video signal is converted to low frequency, and the azimuth recording and reproduction (1) It is possible to provide an auto-tracking device that can obtain good image quality even when

In particular, the effects of the present invention are remarkable in an azimuth recording/reproducing system in which the azimuth angle α is increased.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the tracing state of the video head when the auto-tracking device is in operation, Fig. 2 is an explanatory diagram showing the time-axis fluctuation state of the reproduced signal that occurs during the operation of the auto-tracking device, and Fig. 3 4 is an explanatory diagram showing the relationship between the scanning locus R of the magnetic head 1 and the recording track T.
The figure is a block diagram showing one embodiment of the present invention, and FIG.
The timing chart of each part signal in the figure, FIG. 6 is an explanatory diagram similar to FIG. 2 for explaining the present invention in detail. Symbol explanation 1... Magnetic head 2... Magnetic tape 3... Oscillator 4... Electrical/mechanical conversion element 5... Envelope detection circuit 6... Synchronous detection circuit 7... Low frequency 3 Wave circuit 8...
・Phase compensation circuit 9... Adder Fig. 1' - Sai 2 Fig. 3 Low Shaku Sai 4 Fig. Chisai 5 Fig.

Claims (1)

[Claims] Azimuth recording is performed via a magnetic head by superimposing a low-frequency conversion color signal obtained by low-frequency conversion of the color signal in the ridge image signal and a frequency modulation signal obtained by frequency modulating the luminance signal.
- In a magnetic recording/reproducing device of the re-reducing type, the magnetic head is supported by an electro-mechanical transducer, and a signal of an integral multiple of the field frequency is transmitted to the above-mentioned electric/mechanical transducer every time a recording locus recorded azimuthally is scanned during reproduction. At the same time, the magnetic head is applied to the mechanical transducer element, and the reproduced signal Empe o-7' of the reproduction head is synchronously detected with the signal, and the magnetic head is corrected to be positioned at the center of the recording trunk according to the detected output. An auto-tracking device for a magnetic recording and reproducing device, characterized in that it is configured to operate.