JPS60182038A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain a reproduced picture in which the effect of noise band is reduced even in a VTR of the pilot system with inexpensive and easily realized constitution by controlling the phase of a detected output of level information and a head switching signal so as to fix the noise band at variable speed reproduction into a prescribed position. CONSTITUTION:An error signal SE and a head switching signal SSW are frequency-divided and the phase control is executed by making both the frequencies identical. That is, the error signal SE outputted from a comparator 22 becomes a square wave by being waveform-shaped by a DC amplifier circuit and a Schmittt amplifier circuit 25. The rectangular wave output S1 is inputted to a frequency division circuit 26, which frequency-divides an input signal by ¦n-1¦ even if the mode is n-times speed redproduction or 1/n times speed reproduction. Thus, a frequency-division output S2 is obtained. The frequency division output is fed to a phase comparator 27 as one input and the phase is compared with taht of the head switching signals SSW fed to the phase comparator 27 as the other input. The head switching signal SSW is applied via a frequency division circuit 28 and a delay circuit 29.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is based on the reproduction output of a pilot signal recorded on a magnetic tape by a rotating magnetic head together with an information signal such as a video signal. The present invention relates to a magnetic recording/reproducing device that controls the tracking phase of a magnetic recording/reproducing device, and particularly relates to a configuration for processing a noise band during variable speed reproduction (so-called special reproduction).

[Technical background of the invention]

2. Description of the Related Art A video tape recorder (hereinafter referred to as a VTR) is a typical example of a magnetic recording and reproducing apparatus that uses a rotating magnetic head to record and reproduce information signals.

This VTR is generally capable of variable-speed playback (slow playback, high-speed playback, still playback, etc.) in which playback is performed at a speed different from the recording speed. When this variable-speed reproduction is performed, the rotary blow-up head crosses tracks with different force dots or recording azimuths between trunks, so that noise bands occur on the reproduction screen.

Conventionally, a technique has been developed in which a rotating magnetic head is mounted on a movable plate such as a bimorph, and the position of the head attachment is controlled during variable speed playback to prevent noise bands from appearing on the screen.

In this method, since the noise band disappears from the screen, the influence of the noise band is completely eliminated, but it has the problem that the configuration is extremely expensive and complicated.

To solve this problem, a method has been devised to always fix the noise band at a fixed position on the screen, although it cannot completely eliminate the noise band.This method controls the tracking phase of the rotating magnetic head. The noise band is fixed by controlling the phase of the head switching signal that guides the playback output of the control signal recorded on the control track of the magnetic tape and the playback output of the head scanning the magnetic tape to the playback processing circuit. This method has the advantage that it can be realized at a lower cost and with a simpler configuration than the previous method.

[Problems with background technology]

However, since the latter method presupposes the existence of a control signal, it cannot be applied to the so-called "guironote type" VTR, which has undergone significant research and development in recent years.゛This is the pilot method V'l”R
records the original signal on the video track, and fI
This is because the tracking phase of the rotating magnetic head is controlled based on the playback output of the 4-bit signal and the pilot signal, and the basic principle is that the control signal is not recorded on the magnetic tape.・[Objective of the invention] This invention was made in order to deal with the above-mentioned circumstances, and it is a configuration set that can be realized easily and inexpensively, and a pilot system V.
It is an object of the present invention to provide a magnetic recording and reproducing device that can obtain reproduced images with reduced influence of noise bands even in TR.

[Summary of the invention]

This invention detects the level of a pilot signal from an adjacent track (i-signal) detected in order to control the tracking phase of a rotating magnetic head and detects that it has a predetermined frequency relationship with a head switching signal during variable-speed playback. By controlling the phase of the detection output and the head switching signal,
The noise band is fixed at a predetermined position during variable speed playback.

[Embodiments of the invention]

Hereinafter, six embodiments of the invention will be described in detail with reference to Figure i.

In order to make this point easier to understand, we will explain the tracking control operation of the rotary air head in a hydro-type VTR based on FIG. In the following explanation, the explanation will be made on the basis of all representative four-frequency/e-channel systems that use four P-channel signals having different frequencies as pilot signals.

During recording, pilot signal generation Y:, i 11 to terminal 1
In synchronization with the head switching signal (Ssw) applied to 2,
Four pilot signals (P) are output cyclically in a predetermined order. Each output pilot signal ψ) is led to a video signal recording processing circuit (not shown) via a terminal 13,
superimposed on the video signal. The Tani Byrono (No. 8) is superimposed on the video signal and is sequentially recorded on different video trunks by a rotating magnetic head.

The frequency of each pilot signal ψ) is set to be lower than the frequency band (600 to 7001 kHz) of color a, which is frequency-converted to a low frequency. That is, the frequency of each pilot signal (P) is (fx).

If expressed as (f2), (f3), and (f4), these are h”6.5fu + f2 above?, 5fu, respectively.
, f3:lO,5hr rfa"'L5fH. Here, fH is the horizontal scanning frequency (approximately 15.7
34 kHz). When the frequencies are set in this way, the following relationship holds true.

1flfzl=1f3f41=fu...(1)lf
z, f31=lf4j'+1=3fn...(2)
It should be noted that the above-mentioned flat signal P(fx) ~ P
For example, the sequence when recording (f4) is p(ft
)→P (f2)→P(fs)→P Cf 4)→P
(f t)→... is set.

On the other hand, during reproduction, the reproduction output from the rotating magnetic head is supplied to the low-pass filter 15 through the terminal 14, and the 11 raw output of the pilot signal P is extracted. The reproduction output of this pilot No. 16 P is amplified by an amplifier 16 and then supplied to a multiplier 17 .

As shown in Table 1, the reproduction output sequence of the pilot signal P is the same as the recording sequence. Note that in Table 1 and Table 2, which will be described later, the right and left are based on the tape pattern shown in FIG. 2, which will be described later.

Table 1 The multiplier 17 outputs the regenerated output of the pilot signal P and the reference signal H supplied from the seven-point signal generator 11.
Multiply by Gogo R. As this reference/4' pilot signal R, -! There are four signals with the same frequency as the valley pilot signal, as shown in <1. And the four bases 1
■The pilot signals R(ft) to R(f4) are in the same sequence as the reproduced pilot signals P(fl) to P(f4), and are out of phase with the raw and pilot signals P due to the head switching signal (Ssw). The signals are synchronized so that they match and are supplied to the multiplier 17.

As the reproduced output of the pilot signal P, in addition to the signal P from the main track (the track being scanned), there are two signals P given as crosstalk components from the left and right adjacent trunks.

Now, considering the case where the head (B) is scanning the video track (m+2) on which the pilot signal P (fz) is recorded, in this case, the reproduction output of the 10-node signal P is three nodes. 4 Irosotho conversion month p(fz), p(fx
), p(fs) are calculated. Therefore, multiplier 17
The following three frequency components can also be obtained as the multiplication output.

■ 1f2-fz1: Multiplication output based on the pilot signal P (fz) from the main trunk (m+2) ■ 1fz f3V: Multiplication output based on the pilot signal P (fs) from the left adjacent truck (4m+3) Calculation output ■ Ifz f1 Multiplication output based on the pilot signal P (fz) from the right adjacent track (4m+1) In this case, the component of ■ is zero, so the result is ■.

Only the component (■) can be obtained. As is clear from equations (1) and (2), these multiplication outputs represented by ■ and ■ each have a frequency of 3fn + fH. The same goes when other tracks are being scanned, and the pilot signal P is given as a crosstalk component from both left and right adjacent tracks.
Based on , two types of multiplication outputs with frequencies of (fu) and (3f+i) are always obtained.

Therefore, if, for example, the rotational phase of the capstan motor is controlled so that the levels of these two multiplication outputs match or have a predetermined difference, the left and right deviation of the tornoking phase of the head can be corrected, and the main trunk can be maintained in good condition. The phase can be set to allow scanning.

In Figure 1, , 18 and 19 are the frequencies (fn
), (:3fn), 20.21 is a level detection circuit that level detects the output signal of each filter 18.19, 22 is a level detection output of each level detection circuit 20.21. Comparison 11 A comparator that outputs the difference, 23 a capstan motor APC (
The loop filter 24 in the (automatic phase control) loop is a terminal. In this case, APC of the capstan motor is applied so that the difference output of the comparator 22 (hereinafter referred to as error signal (SE)) becomes zero or a constant value.

In addition, when the head (including head) is scanning and when the head (B) is scanning, as shown in Table 1, the frequency of the multiplication output based on the zero point information P from the right 11A contact track is The frequency of the multiplication output based on the signal P from the left adjacent track is inverted. Therefore, in reality, a switch is provided before the comparator 22, and no matter which head is scanning, the comparator, the comparator 22
For example, the child terminal of 2 contains multiplication information from the right adjacent trunk,
The input states of the two detection outputs to the comparator 22 are switched so that the multiplication information from the right adjacent track is supplied to one terminal.

However, if the sequence of the reference pilot signal R is set as shown in Table 2, the frequency of the multiplication output based on the pilot signal P from the adjacent left or right track will be the same as that of the heads (A) and (B). The same is true when either is being played, so there is no need to provide a switch as described above.

Here, the configuration and operation of 411 for reducing the influence of noise bands during variable speed reproduction, which is a feature of the present invention, will be explained.

When the shift angle is changed in a pilot type VTR as described above, the entertainment difference signal (SE) obtained from the comparator 22 is
7?1" The level changes with the wave number. Figure 2 shows this situation. However, in this figure 2, 5
The case where double-speed high-speed playback is performed is shown as a representative example. Figure 2 (
A) shows the scanning state of the two heads (A) and (+3). In the figure, for convenience of drawing, the magnetic tape is divided into small blocks (Kl) to (K5) and shown side by side. In this case, Puo.

Blocks (Kl) and (K2) are the same block, and blocks (K3) and (K4) are also the same block. 1. Blocks (Kl), (K3), and (K5) show scanning with head σ), and blocks (K2), (K
4) shows a state in which the head (B) is scanning.

Also, the symbols (Pl) and (P2).

(P3) is shown to indicate the same point on the magnetic tape. (Xl) is still in the tape running direction (
(corresponding to the right direction in Tables 1 and 2) is shown (-1 (X2)
indicates the scanning direction of the head. As shown in the figure, in the case of 5x speed reproduction, the head (A), (13) scans the magnetic tape so as to span five tracks.

FIG. 2(b) shows the head switching signal (Ssw).

Figure 2(c) shows the luminance signal (frequency modulated) (Y
), and in the same figure (dJ indicates the reproduction output of the pilot signal P. In the case of azimuth recording, the level of the superimposed output of the head decreases when reproducing tracks recorded with heads with different azimuth angles. Therefore, the corridor signal (Y)
and the 111 raw output of the pilot signal P are shown in Fig. 2(c), (
As shown in d), it has a triangular wave envelope. Note that in FIG. 2(c), (NB) corresponds to the noise band.

FIG. 2(e) shows the sequence of the reference signal R and the original signal R. However, FIG. 2(e) shows what is based on Table 2.

Figure 2 (f) and (g) are frequencies (fu), respectively.
, (3fn). The error No. 46 (SE), which is the difference component between these two multiplication outputs, becomes a repeat No. 42 of a waveform close to a triangular wave, as shown in Figure 2 (h).
The frequency is 2 times the number of cycles Ju of the head switching signal (Ssw).
It will be doubled.

1 By the way, the frequency of the error signal (SP) at n times speed or 1 times speed (where n is an integer) is (tn>,
(t'->stitching, and assuming that the frequency of head switching No. 48 (Ssw) is (fnsw), the following equations (3) and (4
) holds true.

l 1-n l = -fHsw 11 n-11 = n-11 = fns n From equations (:3) and (4), frequency (fn), (f'
-) are the frequency kalpa (f) of the head switching signal (Ssw), respectively.
It can be seen that there is a predetermined relationship with JIsW). Therefore, in a VTR using a conventional control signal, during variable speed playback, a control signal having a predetermined frequency relationship with the head switching signal (Ssw) is used to suppress noise.
In this way, it is possible to reduce the influence of noise bands using the error signal (Sk:).

This is an error signal (Sr,) and a head switching signal (S S
This is achieved by controlling the phase with W), and the circuit configuration of one embodiment is shown in FIG.

In the example shown in FIG. 3, the error signal (Sg) and head switching signal (Ssw) are frequency-divided to make both frequencies the same and phase control is performed.

That is, the error signal (SE) output from the comparator 22 in FIG.
The waveform is shaped into a rectangular wave.

This rectangular wave output (Sl) is input to the frequency dividing circuit 26.

This frequency dividing circuit 26 divides the frequency of the input signal by 1n-i1 in either case of n-time speed reproduction or single-speed reproduction. Therefore, the frequency of the divided output (S2) is given by the following formula (F+)
, we get what is shown in (6).

fn/l n I I = fusw/2 (at n times speed)・<5) f6/l n 11 = fnsw/2n
(at 4x speed) = - (6) This frequency divided output is output from the phase comparator 27
The head switching signal (Ssw) is supplied as one input to the phase comparator 27, and its phase is compared with the head switching signal (Ssw) supplied as the other input to the phase comparator 27.

This head switching signal (Ssw) is supplied via a frequency dividing circuit 28 and a delay circuit 29. At n-times speed, the frequency dividing circuit 28 divides the head switching signal (Ssw) by two to obtain a frequency-divided output (S,) having the same frequency as the frequency (f usw/2 ) shown by equation (5). . At 1x speed, the head switching signal (SSW) is divided by 2n, and the divided output (S3) having the same frequency as the frequency (fH8W/2n) shown in equation (6)
). Note that this frequency dividing circuit 28 may be omitted, and in this case, it is advantageous in terms of response speed. This frequency divided output (S
3) is delayed by the delay circuit 29, and this delayed output (S4
) is compared in phase with the 6iJ divided frequency output (s2). Then, the phase comparator 27 obtains an error signal (S5) having a level corresponding to the phase difference between the two, and the error signal (s
In step 5), for example, the noise band can be fixed by applying APC to the cazostan motor. In this case, by appropriately setting the delay capture ('rn) of the delay circuit 29, it is possible to bring the noise band to a desired position on the reproduction screen. In particular, at -i (so-called reverse playback) and 2.3x speed, the noise band can be brought into the vertical blanking period and erased from the playback screen.

Note that 30 is a terminal.

Note that the phase comparator 27 may also be used as a phase comparator that compares the phase of a signal indicating the rotation frequency of the cab stan with a reference signal in order to keep the rotation speed of the cab stan constant during recording. .

In addition, in the above explanation, the case where the phase control of the error signal (SE) and the head switching signal (Ssw) is performed was explained, but the outputs of the band pass filters 18 and 19 and the level detectors 2o and 21 are also During playback, the head switching signal (S
Since there is a predetermined frequency relationship with the head switching signal (Ssw), the phase of any one of these outputs and the head switching signal (Ssw) may be controlled.

Furthermore, in the above explanation, the error coefficient (S) and the head switching signal (S s w ) are frequency-converted, their frequencies are matched, and then the phases are compared. As is clear from the statement that the two frequencies may be omitted, it is not necessary to match the two frequencies; for example, the phases may be directly compared without performing frequency conversion.

1. In the above explanation, we have explained the case where it is applied to a system that controls the tracking phase of a rotating magnetic head based on level information of pilot signals from both adjacent tracks. It goes without saying that by comparing the levels of the level i+'+ information published in the publication with the standard (issue i4), it can also be applied to a system for controlling the tracking phase.

〔Effect of the invention〕

As described above, according to the present invention, similar to the conventional method of reducing the influence of noise bands using control signals,
It is possible to provide a magnetic recording and reproducing device that can reduce the influence of noise bands with an inexpensive and simple configuration.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the tracking phase control operation of the rotating magnetic head in a four-frequency pilot type VTR, and Fig. 2 is a signal waveform diagram for explaining the 5x speed playback operation of the VTR in Fig. 1. FIG. 3 is a circuit diagram showing a main part of an embodiment of the present invention. 25...DC amplifier circuit and Seamino 1 circuit, 26°2
8... Frequency divider circuit, 29... Delay circuit, 27... Phase comparison circuit.

Claims (1)

[Claims] A plurality of pilot signals having different frequencies are cyclically recorded together with information signals on each information track of a magnetic tape by a rotating magnetic head, and during playback, Pyroft No. 48 is given as a crosstalk component from adjacent tracks. In a magnetic recording and reproducing apparatus that detects level information of the magnetic tape and controls the tracking phase of the rotary magnetic head according to the detected output, the detected output of the level information and the reproduced output of the rotary magnetic head while scanning the magnetic tape are output as 71J. By controlling the phase with the head switching signal to lead to the processing circuit,
A magnetic recording and reproducing device characterized in that it is configured to fix a noise band at a predetermined position during variable speed reproduction.