JPS5911526A - Magnetic reproducer - Google Patents

Abstract

PURPOSE:To eliminate effectively crosstalk sent from adjacent tracks, by performing tracking in the state that one end of a reproducing wide head is almost coincident with one end of a recordong track. CONSTITUTION:A pilot signal detected at a pilot detecting circuit 11 is detected for the beat component at beat detecting circuits 12, 13, amplified at amplifier circuits 14, 15, rectified at rectifier circuits 16, 17, given to a comparator circuit 18 and supplied to a level detecting circuit 22. An operation circuit 19 drives a reproducing head with a signal from level detecting circuits 21, 22. The tracking of the reproducing head 23 is controlled so that the crosstalk level P4 or P6 of the pilot signal is minimized and the one end of the reproducing head 23 is made coincident with the one end of the recording track T5 to be reproduced as shown in (d) or (e), thereby decreasing remarkably the crosstalk.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention performs azimuth recording using a recording head having an azimuth angle, and reproduces the recorded data using a helical scan video tape recorder having a reproducing head having a head width wider than the recording track width. The present invention relates to a magnetic reproducing device that effectively reduces crosstalk from adjacent tracks in some cases.

Conventional configuration and its problems Traditionally, home video tape recorders (hereinafter referred to as VTRs)
In j), an azimuth recording method is used to increase the recording density. As is well known, the azimuth recording method is
This is a method in which recording and reproduction are performed by tilting the gap angles of the two heads several degrees from the direction perpendicular to the direction of travel of the heads, and no loss occurs when reproduction is performed with reproduction heads having the same azimuth angle. Alternatively, when reproducing with a reproducing head having a different azimuth angle, azimuth loss occurs and the reproduction output decreases. However, the azimuth recording method effectively utilizes this output drop, and has the effect of suppressing crosstalk from adjacent tracks when the playback head plays back to adjacent tracks. It was introduced in

Here, azimuth loss and crosstalk from adjacent tracks will be briefly explained. FIG. 1 shows the inclination of the recording track and the head gap, assuming that recording was performed in gear and reproduction was performed at a gap with an azimuth angle θ of 1°.

In this case, the azimuth loss is expressed by the following formula.

In a VTR, since recording and reproduction are performed at an azimuth angle of ±θ with respect to a direction perpendicular to the direction of head travel, the above equation 0 is transformed as follows.

Shoe Punishment -〇λ Now, based on this equation 0, the ratio C/S between the crosstalk from the momentary contact track and the signal (desired signal) from the track having the same azimuth 1j is expressed by the following equation.

Here, in the long wavelength region, that is, in the range of λn2π△W-θ, the W- term in the above equation 0 becomes the cross W-△
In the short wavelength region λ × 2π△W−〇, the maximum value of the crosstalk is 2π△W s+n (□・−〇)=1 λ. It is well known that ``habo'' is expressed.

Now, in recent VTRs, the playback head width is often made wider than the recording track width.

The purpose of this ground is to increase the effective output when tracking is lost, and to make it possible to easily perform special playback without noise. The so-called wide head with this wide width will be considered below.

First, as shown in FIG. 2, the crosstalk in the case of t times when reproduction is performed using wide reproducing heads (a) and (b), which are wider than the recording track width, is determined. The calculation formula is as follows.

If the width of Matoko's playback head is W, then W-T=W1+W2 becomes.

Now, using this formula, the amount of crosstalk for wide playback (a) is calculated. In addition, wide playback (a)
5. The relative speed between (b) and the tape. Bm/sec.

Here, T-60μ, θ=6°, Wt = W2 =
15μ, W=90μ.

The frequency is plotted on the horizontal axis as shown in FIG.

Next, we will calculate the crosstalk of the wide playback head (b). Here, T=60μ, θ=6°, W1=O.

W2=80μ, W=90μ, and the frequency is plotted on the horizontal axis as shown in FIG.

Looking at this, it can be seen that both wide playback heads (a) and (b) have a C/S permeation of -25 dB near 4 MHz, which almost agrees with the calculation result using the above equation 0.

Next, we will calculate the crosstalk when the track width is narrowed to increase the density of the VTR. Wide playback head (
For a), T=10μ, θ-6°, W1=W2=8
．． 5μ, W=17μ, wide head (b), T=10p, 0=6a, Wl=O, W2=7μ,
Assuming W = 17μ, the results of both calculations are shown in FIG.

Looking at this, 4. Near MHz4J, wide playback head (
In a) c7S=-t, sdB, m wide playback head (b)
'C is C/5=-40dB, and there is a large difference in the amount of crosstalk.This difference appears in l1lI11@ as the track width becomes narrower.In other words, in a narrow track VTR, the conventional optimum In a state like wide playback head (b), there is less crosstalk from adjacent tracks than in a state like wide playback head (a), which is considered to be a tracking state.In other words, when wide playback head (b) The position is the optimal tracking position.

In an actual VTR, the tracking state varies to some extent, and the crosstalk kite moves 6 degrees accordingly. Therefore, the amount of crosstalk when the tracking changes next time is determined. Condition of wide playback head (a) (Wl:W2=5:
5) to Wl:W! =4:6, the amount of crosstalk is calculated to be -7.8 dB. This (a
').

Also, the condition of the wide playback head (b) (Wl:Wz=O:1
0) to W, :W2=1:9,
The amount of crosstalk is calculated to be -18 dB. this(
b'). However, the frequency is assumed to be 4 MHz.

In other words, when the state changes from state (a) to state (a') in Figure 2, the 4MHz crosstort weight is -7,8.
If it takes a value between dB and -7,8 dB and changes from the state in Figure 2 (b) to the state in (b'), -40 dB.
It will take a value of B~-18 dB. The calculation results are shown in Figure 6.

By the way, the method of displacing the recompression head in the direction of the rotation axis of the cylinder according to the tracking error information is, for example,
A number of methods have been considered, such as a method in which the adhesive head is made into a bimorph shape, attached to a piezoelectric element, and the head is driven by changing the applied voltage.

The tracking error detection method can be roughly divided into two methods: ■ A method using an auxiliary head, and ■ A method that detects playback when the head is forcibly vibrated in the width direction of the track. Wobbling method that detects the phase difference between the level improvement of No. 15 and the forced vibration signal written in @"lJ, ■
It is classified as a pilot signal type that records a pilot signal different from the main information signal.

Here, the automatic tracking method using pilot signals will be briefly explained. In this method, the difference in frequencies between adjacent tracks is set to 1 during recording. /,, /2.../
A plurality of n pilot signals are recorded on each track on a magnetic tape by a magnetic head, and a cross between the pilot signal reproduced during reproduction and the pilot signal from an adjacent track generated by tracking. This tracking deviation is attempted to be prevented by detecting the talk component. For example, Ha,
The pilot signal /2.../n is a four-plate signal fl* /2 + /3-14, and the relationship between the frequencies of these signals is 11 fz = /! /4'<I
The pilot set to 3/2 = /, -8 is selected for the other phase, f1 = 110KHz, 12 = 90K [(
When z, /3 = 100KHz and 8 = 120KHz, /, -/2 =/, -/.

=20KHz4/3-/2=/4/1=10KH2, and these pilot signals f1 to f4 are recorded on each track on the magnetic tape, and during playback, they are combined with the pilot signal played back via the playback head. , the frequency difference between the pilot signal from the adjacent track that is simultaneously reproduced due to tracking deviation is compared, and the comparison signal obtained is, for example, the difference between the reproduced pilot signal and the adjacent track that is reproduced at the same time due to tracking deviation. The first thing to note is the sideband component l of the two-side band limb components of the pilot No. 41 obtained by balanced modulation of the pilot No. Gd.
In this case, it is possible to determine whether the tracking is off or not. However, fl-/2 =/3-/4 "20KHz!y/3-
12 = 74 - f1 = 10 KHz, and the frequency difference differs depending on the tracking direction 1 of the reproducing head. In the past, the tracking direction of the playback head and the track on the magnetic tape was detected using a comparison signal, and the relative position of the playback head and the magnetic tape was controlled, thereby automatically tracking the playback head. That's what I'm trying to do. Note that such a low-frequency pilot signal is set in a band that does not affect the information signal (desired signal) and causes almost no azimuth loss.

Now, when a wide head is used for the above-mentioned automatic tracking, tracking has conventionally been carried out so that the beat forces of 10 KHz and 20 KHz due to the crosstalk of the 1-town pilot Id column are at the same level. That is, tracking as shown in FIG. 2(a) was considered optimal.

Next, FIG. 7 shows a block diagram of an automatic tracking circuit during reproduction in a conventional magnetic reproducing apparatus. (1) is a pilot detection circuit, (2J (3) is a beat detection circuit, (4
1 (5) is an amplifier circuit, (6) (7) is a rectifier circuit, (8)
is a comparison circuit, (9) is an arithmetic circuit, and C1O is a head drive circuit. The pilot signal included in the reproduced signal is detected by the pilot detection circuit (1), and the heat component of the pilot signal is detected by beat detection 1m m ( 2) After detection in (3) and amplification in amplifier circuits (4) and (5), rectification circuit (5)
) (7), and the comparator circuit (8) compares the levels.
After the arithmetic circuit (9) detects the direction in which the playback head and the track slide, the playback head is driven via the head drive circuit 00.

In this way, in most conventional magnetic reproducing devices, the recording track width and the reproducing head width are the same;
No idea has been made for using a wide head.
A tracking position such as is considered to be optimal and was controlled in this manner.

Due to changes in trade secrets, recording track widths are becoming narrower, and conventional magnetic reproducing devices are unable to effectively eliminate crosstalk due to azimuth loss, as mentioned above. A problem has arisen.

Purpose of the Invention The present invention eliminates the above-mentioned conventional drawbacks, and effectively eliminates crosstalk due to azimuth loss when reproducing a narrow recording track with a wider reproducing magnetic head. The object of the present invention is to provide a magnetic reproducing device that can be used in various areas.

Structure of the Invention In order to achieve the above object, the magnetic N) main device of the present invention comprises:
In a video tape recorder equipped with a recording head having an azimuth angle and a reproducing head having a head width larger than the recording track width and an azimuth angle equal to the azimuth angle, a zero mark is written at one end of the recording track to be reproduced. This configuration is provided with tracking means including automatic tracking means for tracking so that one end of the reproducing head substantially coincides with the other.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Figure 8 is a circuit block diagram of the automatic tracking circuit, where 0υ is a pilot detection circuit, @αken is a beat extraction circuit, σ is an amplifier circuit, OQO power is a rectifier circuit, (T)
is a comparison circuit, (11 is an arithmetic circuit, and 翺 is a head drive lI!
I omitted, Si V (J level detection circuit. The pilot detection circuit αυ twists the pilot signal included in the reproduction G1, and this pilot signal is sent to the beat detection circuit OJ.
The beat component is detected by a3, and after being amplified by the amplification circuit *a and 0, the beat component is sent to the rectifier circuit αtsa71'''
The signal from the rectifier circuit aQOη is sent to the comparator circuit (g) and is also supplied to the level output circuit e. The level finding circuit Qv sends a signal to the arithmetic circuit 4 when the input signal level falls below a predetermined level. ,
Calculation concave tNIFs is usually a trust phase with few beat components,
The reproducing head is driven so that the number of digits decreases by one, and the reproducing head is driven so that its operation is reversed using a signal from the level distribution circuit υ.

Section 9 is an explanatory diagram of the operation of the automatic tracking 1g circuit, in which (T4) to (TII) are recording tracks, (a) is the trajectory of the playback head 4, (b) and (c) are @contact tracks (T4X
Beat component of the pilot signal from Tg), (2) is the output of the level detection circuit (C), (E) is the head m movement circuit)
This is the output of It should be noted that only one of the outputs of the level detection circuit υ(2) is made small and has a slight hysteresis.

In this way, as shown in (dJ or (e) of the JO factor, one end of the reproducing head (2) can automatically track the entire position where it almost coincides with one end of the recording track (T5). In FIG. 10, ( 28a) is the center of the playback head, (S) is the playback output column, (P4) is the track (
The crosstalk level of the pilot signal from T4),
(Pg) is the crosstalk level of the pilot signal from the track (T6). In this way, track the playback head so that the crosstalk level (P4) or (P, t) of the pilot signal is minimized, and then set one end of the playback head as shown in (d) or (e). By aligning almost the end of the recording track (T5) to be reproduced, the reproduction head threat (C) can be prevented as in the conventional method.
As mentioned in the explanation of FIG. 2, the crosstalk can be significantly reduced compared to the case where J only is controlled as much as possible.

In addition, in the above embodiment, C uses a pilot signal.
We explained an automatic tracking method that extracts tracking error information and drives the head using a piezoelectric element, etc.
Other automatic tracking methods may also be used.

In addition, in the above embodiment, an example was explained in which the tracking state with respect to the recording track was changed by directly moving the playback head using tracking error information, or error information may be sent to the capstan servo system. A similar effect can be achieved by manually adjusting the tracking volume.

As described above, the Flea Collector J'L of the present invention is designed to track in a state where one end of the reproduction head or one end of the recording track coincides with the other end of the recording track. The crosstalk of M can be effectively reduced, and with a narrow track width Ii, l wide head, l use f, :V 'r
For R, the effect is huge.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of azimuth loss, Explanation 1 of the relationship between the second tracking state and crosstalk immunity, @ Figures 8 to 6
Figure 7 is an explanatory diagram of the crosstalk foot, Figure 7 is a circuit block diagram of an automatic tracking circuit in a conventional system, Figures 81 to 10 illustrate an embodiment of the present invention, and Figure 8 is a diagram of an automatic tracking circuit. The circuit block diagram, Fig. 9 is an explanatory diagram of the operation of the automatic tracking circuit, and Fig. 10 is an explanatory diagram of crosstalk 臘.
Beat imitation circuit, α~αG...amplifier, Ql (+7
1... rectifier, 0... comparator, oll... arithmetic circuit, ni)... head drive circuit, riυ■・° level detection circuit, wire... reproducing head. Agent Zenihiro Morimoto Figure f Figure 3 Figure 4 E Exit θ ~ 5 [MHI! ] Fig. 5 (, RO55TALK CURVE I-1Z) Fig. 1 Fig. 7 Fig. 1 Fig. 9 Fig. 1θ Fig. 3a cct

Claims (1)

[Claims] 1. A recording head having an azimuth angle, and a reproducing head having a head width larger than the recording track width and the same azimuth angle as the azimuth angle, one end of the recording track to be reproduced. A magnetic reproducing apparatus characterized by comprising a tracking means for tracking substantially coincident with one end of the reproducing head. 2. Pilot signals having different frequency or phase differences in adjacent tracks are sequentially recorded on each track for a period of P9T by a recording head, and during reproduction, the level of the pilot signal reproduced from the recording track to be reproduced is set as a reference voltage. The tracking means is configured to detect tracking error information by comparing or by finding a frequency difference between the pilot signal and a pilot signal reproduced from an adjacent track.
2. The magnetic reproducing apparatus according to claim 1, wherein the magnetic reproducing apparatus is configured to use self-recorded tracking error information to maintain a tracking deviation to one adjacent track at a minimum value that can be detected by the tracking error information.