JPS61131261A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce jitter components of a playback image of a 4-head type helical scan VTR by allowing the same head as a heat used for recording to track respective tracks. CONSTITUTION:When a PG signal is inputted to a terminal 1, pilot signals which are generated repeatedly in every period appear at terminals of a pilot signal selecting circuit 9 in the order of f1, f2, f3, and f4. Those pilot signals are recorded while superposed on video signals during recording, and used as reference pilot signals during reproduction. Further, input signals (a) and (f) to terminals S1 and S2 are used to confront an R head in a period wherein, for example, f1 is generated, an L head in a generation period of f2, an R' head in a period of f3, and an L' head in a period of f4. Consequently, respective tracks are tracked by the same head as a head used for the recording and a playback image having less jitter components is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording and reproducing apparatus (hereinafter referred to as a VTR) that uses a rotating head to sequentially record and reproduce signals on a magnetic tape as a diagonally inclined discontinuous recording trajectory. ), and particularly relates to a tracking method in a VTR that performs tracking control using a pilot signal.

Conventional technology A configuration of a four-head helical scan VTR with a smaller head drum diameter that provides a tape-compatible recording trajectory with a two-head helical scan VTR is shown, for example, in Japanese Patent Application Laid-open No. 89612/1983. There is.

An overview of the configuration of this four-head helical scan VTR will be explained.

In general, a two-head helical scan VTR is wound around a rotating rad drum at an angle slightly larger than 180°, and two magnetic heads are arranged on this drum at an interval of 180°. The four-head helical scan VTR, which achieves a recording trajectory compatible with the two-head helical scan VTR, wraps the videotape around a drum at an angle slightly larger than 270°, as shown in Figure 3, and has an R ,L,
R'.

Four video heads called L' are arranged at 90° intervals,
It is configured to operate by sequentially switching these heads for each field.

As mentioned above, R and R' are heads with an azimuth angle of +α, and L and L' are heads with an azimuth angle of -a.

In addition, this 4-head helical scan VTR has a drum diameter of 3 mm compared to a 2-head helical scan VTR.
(The drum rotation speed was reduced to 270O, which is 1.5 times
It is driven at rpm.

FIG. 4 shows the relationship between a pulse signal (PG double signal) synchronized with the rotational phase of this four-head type helical scan VTR and a video head switching signal.

The PG multiplied signal is configured to generate one pulse per rotation of the drum. That is, the drum rotation speed is 270 Orpm.
In this case, the PG double signal period is 45 tlz. This P
Based on the G multiplied signal, a signal for switching each head is created as shown in FIG.

The above is an overview of the configuration of a four-head helical scan VTR.

Next, an overview of a tracking method using four types of pilot signals, such as those used in 8 mm video, will be explained.

During recording, four types of pilot signals f1 to f4 are sequentially switched for each field and recorded while being superimposed on the video signal. The recording order of pilot signals is as shown in Figure 5.
The order is f1→f2→f3→f4→f1→..., and one type of pilot signal is continuously recorded within one field period.

The frequency of the pilot signal is set to a value shown in Table 1, for example.

Table 1 In Table 1, fH indicates the frequency of the horizontal synchronization signal, and 6.5fH indicates 6.6 of the frequency of the horizontal synchronization signal.
Indicates that the frequency is twice as high.

Next, the time of playback will be described.

Since the viroft signal is a relatively low frequency signal, the pyro throat signal recorded on the adjacent track is also reproduced as a crosstalk signal.

Now, when the head reproduces and scans the track on which the pilot signal f3 is recorded, f2° f3. f
A composite signal of 4 is reproduced. This composite signal and a reference pilot signal (a signal with the same frequency as the pilot signal recorded on the main scanning track) are balanced-modulated to extract a signal with a difference frequency.

The difference frequency signal is fH and 3 fH as shown in Figure 6.
This is the signal. When the head scans a track on which pilot signals fl and f3 are recorded, the difference signal from the signal reproduced from the right trunk is fH.
and the one on the left is 3fH. Also, f2. f4
When the head scans a track on which a pilot signal is recorded, the left-right relationship is opposite to that described above. If the reproduction levels of both the fH and 3fH signals obtained by this balanced modulation are compared, the compared signal contains information about the amount of track deviation and the direction of deviation. This signal is used as a tracking error signal to control the relative position between the recording track and the reproduction scanning locus of the reproduction magnetic head.

The above is an overview of the tracking method using four types of pilot signals.

Problems to be Solved by the Invention However, in the VTR configured as described above, two sets of heads with the same azimuth angle are provided, so the end of a track recorded by the R head is recorded by the R' head. The track recorded by head R' is played back by head R', and the track y recorded by head L is played back by head R'.
A case may occur where reproduction is performed using the tL/head (or the track recorded using the L' head minus the iL head).

Generally, uneven rotation occurs in the drum, and the trajectory of the R head scanning on the track is different, the trajectory of the R' head scanning on the track is different, and the trajectory of the L head scanning on the track is distorted. This does not coincide with the curve of the locus that the L' head scans over the trunk.

Therefore, if the head scans differently during recording and reproduction as described above, the reproduced image may have an extremely large amount of jitter components.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording/reproducing apparatus that can reproduce reproduced images with less jitter components by enabling reproduction with the same head used during recording.

Means for Solving the Problems The present invention is a four-head helical scan VTR that uses four types of pilot signals to control the relative position between the recording track and the reproduction scanning locus of the magnetic throat for reproduction. For example, when recording and reproducing, R
fl when the switch is switched to the throat/L head, f2 when the switch is switched to the L head, f3 when the switch is switched to the R' head, and f4 when the switch is switched to the L' throat.
This is a magnetic recording and reproducing device that has means for generating four types of pyro-node signals while always maintaining a corresponding relationship so that

Function The present invention uses a means for generating four types of pilot signals while always maintaining a corresponding relationship with the head that is switched during recording and playback, so that the head used for a certain recorded track and the head used for this track during playback can be switched at the time of playback. The capstan control system pulls in so that tracking control is performed with the head in an on-track position only when the head that is reproducing and scanning matches the head.

Embodiment An embodiment according to the present invention is shown in FIG. 1, and its specific configuration will be explained.

The PCi signal is input to a delay pulse generation circuit 2 and a head switching signal generation circuit 3 via a terminal 1. The output of the head switching signal generation circuit 3 is input to the differential pulse generation circuit 4.

The delay pulse generating circuit calculates the time t from the rise of the PG multiplied signal to the first rise of the head switching signal. The configuration is such that the output set for a slightly longer time t1 is obtained. The output of the delayed pulse generating circuit 2 is applied to an inverting circuit 5 and the other input of an AND circuit 6, one of which receives the output of the differential pulse generating circuit 4.

Further, the output of the inverting circuit 5 is applied to the other input of an AND circuit 7, one of which receives the output of the differential pulse generating circuit 4. The output of the AND circuit 6 is input to the set terminal (S side) of the R-3 flip-flop 8, and the output of the AND circuit 7 is input to the reset terminal (R10, terminal S1).
The input terminal S2 of the head switch 1. ) Ching signal is input. From the output of the pilot signal selection circuit 9, pilot signals f1 to f4 are generated by being sequentially switched for each field in accordance with the signals input to the terminals S1 and S2, and are guided to the terminal 1o.

The above is an explanation of the circuit configuration of the embodiment, and the operation will be explained using the operation waveform diagram shown in FIG. 30 by circuit 3
A head switching signal a with a cycle of 1 is obtained. This head switching signal a is created from the timing at which the PG multiplied signals 4 and P4 are generated.

7' (t by the first rise of the PG double signal and the head switching signal a.The reason for the delay is that the mechanical mounting of the detection element for detecting the PG double signal has to electrically correct the position. This is because they are doing so.

Furthermore, the PG multiplied signal is input to the delayed pulse generation circuit 2,
Said, toJ:! ll tl with a slightly longer time span
A pulse signal having a pulse l] is obtained.

The head switching signal a is input to a differential pulse generation circuit 4 to obtain a pulse signal cf that is generated only at the rising edge of the head switching signal a.

Output signal of delayed pulse generation circuit 2 and differential pulse circuit 4
By inputting the output signal cf to the AND circuit 6, a pulse signal di can be obtained from the output of the AND circuit 6. This pulse signal d is input to the set terminal of the R-S flip-flop.

! In addition, the output signal of the delayed pulse generation circuit 2 is input to the inversion circuit and inverted, and the output signal cf of the differential pulse generation circuit 4 is inputted to the AND circuit 7. From the output of the pulse signal e
f can be obtained.

This pulse signal e is input to the reset terminal of the R-S free tube flow 1p8.

Therefore, the output Q of flip-frog 7,! : An output signal fi is obtained which rises at the rising edge of the pulse signal d and falls at the rising edge of the pulse signal e.

This output signal f is output from 81 of the pyro, ) signal selection circuit 9.
8 of the pilot signal selection circuit 9.
The head switching signal a is input to the second terminal.

Furthermore, this pyrolide signal selection circuit 9 is shown in Table 2.
If the configuration is configured so that the pilot signals f1 to f4 can be selected at the timing shown in Table 2, it is possible to obtain the pilot signal q that is generated repeatedly for each field in the order of f1 → f2 → f3 → f4 from the terminal 10 in Table 2. can. During recording, the pilot signal obtained from this terminal 10 is recorded superimposed on the video signal 13, and during reproduction, it is used as the aforementioned reference pilot signal.

Furthermore, by using the Sl and 82 terminal input signals a and f, as shown in Table 1, for example, the period in which f is generated is made to correspond to the R head, the period in which f2 is generated is made to correspond to the L head, and f3'fr is made to correspond to the period in which f2 is generated. The period in which f4 occurs corresponds to the R' head, and the period in which f4 occurs corresponds to the L' head.

With the above configuration, when tracking control is performed with the head in the on-track position, that is, when the capstan control system is retracted, the track being scanned is reliably on-track. In this case, the head used during recording can be matched with the head used during reproduction.

As described in detail, according to the present invention, since recording and reproduction can be always performed using the same head, it is possible to obtain a reproduced image with less jitter components in a 4-h) type helical scan VTR.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a pilot signal generation circuit according to an embodiment of the present invention, Fig. 2 is an operation waveform diagram of the same embodiment, and Fig. 3 is a rotating drum and tape winding of a helical scan VTR. Figure 4, which shows the relationship between
A diagram showing the switching timing of the video head shown in the figure,
FIG. 6 is a diagram showing a recording tape pattern in a tracking control method using four types of pilot signals. 2... Delay pulse generation circuit, 3... Head switching signal generation circuit, 4... Differential pulse generation circuit, 6... Inversion circuit, 6.7 ...
. . . AND circuit, 8 . . . R-S flip-flop, 9 . . . Pilot signal selection circuit. Name of agent: Patent attorney Toshio Nakao and one other person
Castle Figure 3 Figure 4 Figure 5 Figure 1 Tee 7 Coconut

Claims (1)

[Claims] This is a 4-head helical scan VTR that can obtain a recording trajectory that is tape compatible with a 2-head helical scan VTR, and has a smaller head drum diameter. The crosstalk signal is sequentially recorded on a magnetic recording medium by being superimposed on the recording track to be reproduced, and during reproduction, a tracking error signal is used in accordance with the level difference between crosstalk signals reproduced from recording tracks adjacent to the recording track before and after the recording track to be reproduced. It is configured to control the relative position between the recording track and the reproducing scanning locus of the reproducing magnetic head, and during recording and reproducing, four types of pilot signals for the four heads are respectively corresponded to the same head and the pilot signal. What is claimed is: 1. A magnetic recording and reproducing apparatus characterized in that it has means for generating a pilot signal so as to track each track with the same head used for recording.