JPS61102884A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To securely correct the distortion on the reproduced plane by providing a delay circuit to delay signals supplied to plural heads for certain length of times respectively for recording when recording and reproducing, to and from the plural tracks, the video signals of one field using plural swivel heads. CONSTITUTION:Reproduction is performed with the same head as the one used for recording i.e. the signals are reproduced from tracks 6a and 6b by the heads 1a and 1b respectively. When reproducing the field division part, at the time when the head 1a on the track 6a reproduces the pat of C, the head 1b is at the part D on the track 6b. This means that the signals reproduced by the head 1b, in comparison with those reproduced by the 1a, are the ones delayed by time T which is equivalent to the distance L on the track (in terms of angles of rotation of a drum 5; theta). This delay time T is set at a value larger than the maximum time base fluctuation expected of the change-over of heads, providing that no signal interruptions occur by the change-over of heads in the middle of the plane.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording and reproducing device that uses a plurality of rotary heads to record and reproduce one field of video signals by dividing them into a plurality of tracks. This invention relates to a recording and reproducing method for properly connecting video signals appearing on a television screen.

[Conventional technology]

Conventionally, helical scan type magnetic recording/reproducing device (hereinafter referred to as VT)
Particularly in consumer VTRs, a method is adopted in which one field of video signal is recorded on one track. When considering downsizing a VTR, assuming that the relative speed between the head and the magnetic tape remains unchanged, that is, the recording and playback characteristics do not change, for example, the number of rotations of the rotating drum on which the head is mounted may be doubled, and the rotation speed may be increased. The diameter of the drum is 1
A method of reducing the size to /2 can be considered. According to this method,
Since one field of video signals is divided into two tracks and recorded, there are two signal joints in one field. If one joint is placed in the vertical retrace period as in the conventional one-field/one-track case, the other joint will be at the center of the screen. Therefore, in order to realize this method, it is necessary to properly connect the video signals at the center of the screen, but this is not easy, and this will be explained below.

Now, assume that two heads record and reproduce the upper and lower halves of the screen, respectively. At this time, if there is a difference in tape tension between recording and reproduction, time discontinuity occurs at the head switching position, resulting in so-called skew. This will be explained using FIG. 4.

In Figure 4 (al), 2 is a magnetic tape, and 3a and 3b are tracks recorded by disks la and lb, respectively.During playback, when head 1a comes to head switching point A, head 1b is in position. If the position B is recorded at the same time as A, the signal connection at the center of the screen is well established. This situation is shown in FIG. 4 (bl). In the figure, P represents the screen seam. However, if position B shifts to 81 due to tape tension fluctuations, the signal between B and B1 will be lost, as shown in Figure 4fc).Furthermore, if position B shifts to B2, as shown in Figure 4fc), As shown in (d), the signal between B2 and B is repeatedly reproduced.

Note that in FIG. 4 (C1, (d), the amount of skew is exaggerated for the sake of explanation. In an actual VTR, the amount of skew is less than one horizontal period, and when received on a home television receiver, the amount of skew is exaggerated. is caused by the internally synchronized AFC circuit, and appears as a curvature in the screen as shown in the fourth Im[c].

In any case, if skew occurs, the seam at the center of the screen becomes noticeable, which is visually undesirable.

However, it is extremely difficult to prevent skew from occurring in a helical scan type VTR, and this has hindered the realization of a field division type VTR.

In recent years, as ICs have become more highly integrated and lower priced due to advances in semiconductor technology, VTRs have been equipped with digital time base correctors (this consists of a time base variation detection circuit and a time base variation correction circuit, as described below). It is becoming possible to correct skew and shifters by adding a DTBC (denoted as DTBC). For example, the DT shown in Japanese Unexamined Patent Publication No. 58-124385
In BC, the amount of time axis fluctuation of the input video signal (time axis error)
is detected by sampling the input video signal with a standard clock signal based on the predetermined phase relationship that exists between the television video signal of a predetermined format and the local standard clock signal, and detecting the deviation between the sampled phase and the predetermined phase. I try to do it based on. In addition, the correction is performed by dividing the time axis error of the input video signal into a large error component whose unit is a sampling clock period and a small error component whose unit is one sampling clock period or less. The latter precise correction can be made by changing the driving clock signal of the D/A converter from which the corrected output video signal is taken out or the input side A/D converter to the standard synchronization signal. This is done by generating a locked clock signal with a phase rotation corresponding to the time axis error.

However, in such a device, simply recording.

If reproduction is performed, signal loss or duplication will occur due to skew, as explained with reference to FIG. In particular, in the case of omission, it cannot be corrected even by DTBC. A known method for solving this problem will be described below.

FIG. 5 is a diagram explaining the principle of a conventionally known system. As shown in the same figure (al), during recording, the video signals of the upper and lower halves of the screen are compressed in time and recorded on their respective tracks, and during playback, they are expanded in time and restored to their original state. .The same figure (b) shows the track pattern on the magnetic tape 2, and the time-axis compressed video signal is recorded on the shaded part of the tracks 4a and 4b. Therefore, to prevent C and D from intersecting with the shaded area E due to the skew,
By appropriately setting the compression rate during recording, signal loss and duplication can be avoided.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional system has disadvantages in that it requires a memory with a large capacity of about 1/2 field, and also requires two systems with different clock frequencies, resulting in a large circuit scale.

This invention was made to eliminate the drawbacks of the conventional ones as described above, and uses N heads (N is an integer of 2 or more) to divide one field of signals into N tracks. An object of the present invention is to provide a recording VTR that can reliably correct distortion on a playback screen without using a large-scale circuit.

[Means for solving problems]

The VTR according to the present invention uses a plurality of rotating heads to
When recording and reproducing a field video signal by dividing it into a plurality of tracks, a delay device is provided to delay each signal supplied to the plurality of heads by a predetermined time during recording.

[Effect]

In this invention, a signal is supplied to a plurality of heads with a predetermined time delay and recorded, and a reproduced signal without any omission at the joint inside the screen is inputted to the DTBC during reproduction,
To reliably correct distortion on a playback screen.

〔Example〕

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

FIG. 1 shows a recording system of a VTR according to an embodiment of the present invention.

A schematic configuration of the signal processing of the reproduction system is shown, and in this embodiment, the number of heads is two. In the figure, 7a is an FM modulator that performs FM modulation on the input video signal r, 15a is a delay device that delays the output of the FM modulator 7a for a predetermined time T, 3a, 3b
are recording amplifiers provided corresponding to heads la and lb, and outputs s and t of these recording amplifiers 8a and 8b are supplied to heads la and lb, respectively. Also, 9a, 9
b is a reproduction amplifier that amplifies the reproduction signals u and v of the heads la and lb, respectively; 10 is a switching circuit that switches and outputs the output of the reproduction amplifiers 9a and 9b in synchronization with 50 revolutions of the rotating drum; 1) is this switching circuit; F for FM demodulating the output of the circuit 10
It is an M demodulator. Reference numeral 14 includes a time axis variation detection circuit 12 that detects a variation in the time axis of each reproduced signal, and a time axis variation correction circuit 13 that corrects the time axis variation according to the detection result, and outputs a corrected video signal W. This is a time axis corrector, which is disclosed in, for example, the above-mentioned Japanese Patent Application Laid-Open No. 58-124385.
This method is publicly known as shown in No. 1, etc.

FIG. 2 ta) is a diagram showing the navel arrangement of the VTR according to this embodiment, in which heads la and lb are mounted on the rotating drum 5 at 180 mm.
Mounted at an angle of °. Also, this rotating drum 5
rotates once in one field period.

FIG. 2(b) is a diagram illustrating a tape pattern recorded by the VTR of this embodiment, and in the figure, 6a and 6b are tracks recorded by hefts la and lb, respectively. Tracks 6a and 6b record video signals for the upper and lower halves of the screen, respectively. Also, C, D
, E respectively correspond to the positions with the same symbols in FIG.

Here, the same information as that recorded at the C position of the track 6a is recorded at the E position.

That is, the angle θ shown in +a) in the same figure and the distance shown in ('b) in the same figure correspond to the delay time T of the delay device 15a in FIG. 1 (&).

Next, the operation will be explained.

The input video signal r is FM modulated by the FM converter 7a, and the F
The M-modulated signal is supplied to the head 1a via a recording amplifier 8a, and after being delayed by a time T by a delay device 15a, is supplied to the head 1b via a recording amplifier 8b. And these.

The video signals supplied to heads la and lb are recorded on tracks 6a and 6b, respectively.

Next, the operation during playback will be explained. Reproduction is performed using the same head used for recording, that is, head la
, lb to reproduce signals from tracks 6a and 6b, respectively. The case of reproducing the field division point portion will be explained using FIG. 2 (bl).

When the head 1a reproduces the section C on the track 6a, the head 1b is at the section D on the track 6b.

That is, the signal reproduced by the head 1b is reproduced by the head 1a.
The signal is delayed by a time T corresponding to the distance L on the track (θ in terms of the rotation angle of the drum 5) compared to the signal reproduced by. If this delay time T is set to be larger than the maximum amount of time axis variation expected when switching heads, no signal will be lost when switching heads at the center of the screen.

Therefore, the signal u reproduced by each head la, lb,
v reproducing amplifiers 9a, 9b, switching circuits IO1 and F
The signal of the upper half of the screen inputted to the time axis corrector 14 through the M demodulator 1) and reproduced by the head 1a passes through a delay circuit of a predetermined time, and the signal of the lower half of the screen reproduced by the head 1b is By detecting the amount of time axis variation at the time of head switching at the center of the screen and passing a delay line whose delay time changes according to the detection result, the time axis variation can be corrected.

In this embodiment, since the signal to the head that records the lower half of the screen is delayed during recording, it is possible to eliminate the loss of the reproduced signal at the joint in the center of the screen during reproduction. Therefore, the DTB that inputs the reproduced signal
In case C, it is possible to reliably correct the time axis fluctuation, and it is possible to prevent the occurrence of skew at the seam. Also,
This embodiment eliminates the need for a large-capacity memory as in the prior art, making the device inexpensive.

In the above embodiment, the output of the FM modulator is delayed, but as shown in FIG.
It is also possible to provide two circuits b and delay the input signal to one of them by the delay device 15b, and the same effect as in the above embodiment can be obtained.

In addition, the number of heads is not limited to two, and in general, even in the case where one field of video signal is divided into N tracks and recorded using N heads (N is an integer of 2 or more), the number of heads is n. (n=2...

If the signal to be supplied to the N)th head is delayed by a predetermined time from the signal to be supplied to the (n-1)th head, it is possible to prevent signal loss inside the screen in the same way as above. Therefore, it is possible to prevent skinny from occurring at the seam.

Furthermore, by making the azimuths of adjacent heads different, high-density recording without guard bands is also possible.

〔Effect of the invention〕

As described above, according to the present invention, the signal supplied to each head during recording is delayed by a predetermined time for each head, thereby preventing signal loss when switching heads at the joint inside the screen during playback. This has the effect that distortion on the playback screen can be reliably corrected with a simple and inexpensive device.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a recording system and a reproducing system of a VTR according to an embodiment of the present invention, and FIG. 2 is a diagram of a VT according to an embodiment of the present invention.
3 is a schematic configuration diagram of a recording system of a VTR according to another embodiment of the present invention, and FIG. 4 is a diagram illustrating the influence of time axis fluctuations on a VTR. 5 are diagrams for explaining a method for correcting time axis fluctuations in a conventional VTR. 1 a, 1 b...head, 2...tape, 3
a, 3b. 4a, 4b, 6a, 6b--video signal track, 5...
・Rotating drum, 12... Time axis fluctuation detection circuit, 13.
...Time base fluctuation correction circuit, 15a, 15b...Delay device. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) N heads installed on a rotating drum at intervals of 360°/N (N is an integer of 2 or more) that record one field of video signal by dividing it into N tracks; A time axis variation detection circuit receives the reproduction signal of the head and detects the variation in the time axis of each reproduction signal at the seam of the screen, and a time axis variation correction circuit corrects the above-mentioned time axis variation according to the detection result. In a helical scan magnetic recording/reproducing device equipped with the above, the signal to be supplied to the nth head (n=2, . . . , N) is delayed by a predetermined time from the signal to be supplied to the (n-1)th head. A magnetic recording and reproducing device characterized by being equipped with a delay device. (2) The magnetic recording/reproducing apparatus according to claim 1, wherein the number N of heads is two.