JPS641995B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is directed to the longitudinal direction (running direction) of a magnetic tape.
This invention relates to a so-called helical scan type video tape recorder that records video signals by scanning a magnetic head diagonally with respect to the video tape recorder.

In conventional helical scan video tape recorders, video signals are recorded and played back using a rotating head, and audio signals are recorded and played back along the length of a magnetic tape using a fixed head.

Recently, the demand for high-density recording has increased, and there is a tendency to reduce the running speed of magnetic tape. However, for example, if the speed of magnetic tape is 1 cm/sec.
If you slow down the audio signal to 10KHz, the recording wavelength will be
1 μm, making it extremely difficult to record with current bias recording using fixed heads, and even if it is recorded and played back, it will be impossible to understand the content.

For this reason, a method has been proposed in the past in which the audio signal and the video signal are frequency multiplexed and recorded and played back using a rotating head, but this method does not allow erasure of only the audio signal, so there are problems such as the inability to perform after-recording. There's a problem.

The present invention records audio signals by utilizing the so-called overscan portion, which is the period during which two rotating magnetic heads are in simultaneous contact with the magnetic tape, so that even if the running speed of the magnetic tape is slowed down, the audio signal remains unchanged. Recording or playback, or recording and playback, can be performed well, and since the audio signal track section and the video signal track section are separated on the magnetic tape, after-recording can be performed by erasing only the audio signal track section with a fixed erasing head. The present invention provides a video tape recorder that can perform the following operations.

Hereinafter, the present invention will be explained based on illustrated embodiments. In FIG. 1, a video signal applied to a video signal input terminal 1 is applied to a video signal processing circuit 3 and a synchronizing signal separation circuit 4. The output signal of the video signal processing circuit 3 passes through the first gate circuit 5 and the second gate circuit 6, and then is sent to the first adder 13 and the second gate circuit 6.
is added to the adder 14.

On the other hand, the vertical synchronization signal output from the synchronization signal separation circuit 4 is supplied to delay circuits 7 and 8. The Q output of the delay circuit 7, which together with the synchronization signal separation circuit 4 constitutes head switch pulse generation means, is supplied as a gate pulse to the first gate circuit 5 and a fourth gate circuit 12, which will be described later. It is supplied as a gate pulse to the second gate circuit 6 and a third gate circuit 11, which will be described later. The output signal of the delay circuit 8 is supplied to a time axis compression circuit 9.

Further, the audio signal applied to the audio signal input terminal 2 is supplied to the third gate circuit 11 and the fourth gate circuit 12 via the time base compression circuit 9 and the modulation circuit 10. The third gate circuit 11
The output signal of is supplied to the first adder 13,
The output signal of the fourth gate circuit 12 is supplied to the second adder 14. The output signal of the first adder 13 is applied to a rotary transformer 17 via a recording/reproduction changeover switch 15. Rotating transformer 1
The output signal of 7 is the rotating shaft 19, rotating head bar 20.
The signal is then applied to the rotating magnetic head 21 and recorded on the magnetic tape 23.

On the other hand, the output signal of the second adder 14 is also applied to the rotary transformer 18 via a recording/reproduction switching switch 16 which is linked to the switching switch 15. The output signal of the rotary transformer 18 passes through the rotary shaft 19 and the rotary head bar 20.
The signal is applied to another rotating magnetic head 22 and recorded on a magnetic tape 23.

The magnetic tape 23 is connected to the rotating magnetic heads 21 and 2.
2 is guided by guide posts 24 and 25 located on both sides of a tape guide drum (not shown) containing a tape guide drum (not shown), and is guided by a well-known magnetic tape running device (not shown) consisting of a capstan and a pinch roller in the direction of arrow 27. The vehicle is driven at a constant speed in the direction. In addition,
Since a well-known tape guide drum can be used as the tape guide drum, a detailed explanation of its structure will be omitted here.

Further, 40 in FIG. 1 is a fixed erasing head, which is disposed so as to be in contact with the tape surface near one side edge of the magnetic tape 23, and erases the audio signal.

During reproduction, the signal reproduced by the rotary magnetic head 21 passes through the rotary head bar 20, the rotary shaft 19, the rotary transformer 17, and the changeover switch 15.
The signal is supplied to a separation circuit 28.

On the other hand, the signal reproduced by the rotating magnetic head 22 is supplied to the separation circuit 29 via the rotating head bar 20, the rotating shaft 19, the rotating transformer 18, and the changeover switch 16. One output of the separation circuit 28 and one output of the separation circuit 29 are supplied to an adder 30. Further, the other output of the separation circuit 28 and the other output of the separation circuit 29 are supplied to the adder 31. The output signal of the adder 30 is supplied to a video signal output terminal 33 via a video signal processing circuit 32. On the other hand, the output signal of the adder 31 is sent to a time axis correction circuit 34, a demodulation circuit 35, and a time axis expansion circuit 36.
The audio signal is supplied to the audio signal output terminal 37 via the audio signal output terminal 37.

Next, the operation of this embodiment will be explained. A video signal applied to the video input terminal 1 is converted into an FM signal by the video signal processing circuit 3. Note that when a carrier color signal is included, the carrier color signal is converted to a low frequency of approximately 1.2 MHz or less. Furthermore, as a technique for removing adjacent color signals, it is perfectly acceptable to rotate or invert the phase of the conveyed color signal by 90 degrees every 1H (horizontal scanning period), for example. This is a technique for removing crosstalk between tracks using line correlation of carrier color signals.

The video signal processed as described above is supplied to the first and second gate circuits 5 and 6.

On the other hand, by applying the video signal to the synchronization signal separation circuit 4, a vertical synchronization signal is obtained at its output terminal. This vertical synchronization direction is determined by the delay circuit 7.
and 8. The delay circuit 7 has a divide-by-2 function and a delay function, and outputs pulse signals Q and 1 for head switching as shown in FIG. 2b and c from its Q output terminal and output terminal. 2 and 6, respectively. In order to clarify the phase relationship between these pulse signals Q and the input video signal, an example of the waveform of the input video signal is shown in FIG. 2a. As shown in FIGS. 3a and 3b, processed video signals are output to the output terminals of the first and second gate circuits 5 and 6 while the pulse signals Q and 6 are at H level. A modulated compressed audio signal, which will be described later, is added to these signals by first and second adders 13 and 14, and the resulting signals are supplied to changeover switches 15 and 16.

The time axis compression circuit 9 receives an audio signal supplied to the audio signal input terminal 2 as shown in FIG. 4a and a vertical synchronization signal as shown in FIG. A trigger signal T is applied.

At the output end of the time axis compression circuit 9, a compressed audio signal whose compression start time is controlled by the trigger signal T as shown in FIG. 4c is obtained. Such compressed audio signals can be modulated (particularly pulse code modulation (PCM)) suitable for tape head systems, or
A modulation circuit 10 receives FM, PM, AM, M, etc., or in some cases unmodulated AC bias recording. In particular, PCM is advantageous in that a high signal-to-noise ratio can be expected, and well-known code error correction means can be used to correct dropouts and the like. Note that the broken line between a and c in FIG. 4 shows the state of time axis compression. Such a modulated compressed audio signal is applied to third and fourth gate circuits 11 and 12, respectively, to which the Pils signal and Q are supplied. These gate circuits 11
and 12 outputs the compressed audio signal to the first and second adders 13 and 14 while the pulse signal and Q are at H level.

FIGS. 5a and 5b show waveform diagrams of the output signals of the first and second adders 13 and 14, that is, the used axis multiplexed signals of the processed video signal and the processed audio signal. By supplying these signals to the rotating magnetic heads 21 and 22 via the aforementioned path, a tape magnetization pattern as shown in FIG. 6 is obtained.

In FIG. 6, magnetic tracks 101 and 102 of the video signal track section 110 are video signal tracks, and each corresponds to a field. Magnetic tracks 103 and 104 with diagonal lines in the audio signal track section 111 are audio signal magnetic tracks. When performing after-recording, a certain frequency (for example, 100 KHz) is applied to only the audio signal track section 111 using the fixed erasing head 40.
Erasing is carried out by passing an erasing current of 1, and a new audio signal is recorded by the rotating magnetic heads 21 and 22.

The winding angle of the magnetic tape 23 with respect to the outer circumference of the tape guide drum is set to be slightly larger than 180°, for example, 200°, and the audio tracks 103 and 104 are wound at an angle of 20° corresponding to the overscan portion.
All you have to do is hit it. In some cases, audio tracks 105, 106, 107 and 108 may be provided before and after the video track 101 or 102, as illustrated in FIG.

During reproduction, the movable contacts of the changeover switches 15 and 16 are switched to the fixed contact P side. In this way, the two channels of reproduction signals reproduced by the rotary magnetic heads 21 and 22 are transmitted to the rotary head bar 2, respectively.
0, rotating shaft 19, rotating transformer 17 or 1
8. The signal is supplied to the separation circuit 28 or 29 via the changeover switch 15 or 16. Separation circuit 2
At 8 and 29, the input signal is separated into a video signal and an audio signal on the time axis. This separated video signal is converted by an adder 30 into a temporally continuous one-channel video signal, and is supplied to a video signal processing circuit 32. Video signal processing circuit 32
Then, the input signal is restored to the original video signal and output to the video signal output terminal 33.

On the other hand, the separated audio signal is also converted into a one-channel signal by the adder 31, and the time axis correction circuit 34
is supplied to For example, the time axis correction circuit 34
CCD (Charge Capsule Device) and BBD
(bucket brigade device) and other semiconductor memories, where tape head system time axis fluctuations (so-called jitter and skew distortion)
is removed. The output signal of the time axis correction circuit 34 is converted into the original compressed audio signal by the demodulation circuit 35, and then the original audio signal is restored by the time axis expansion circuit 36, which is composed of a semiconductor memory such as a CCD or BBD, and is output as an audio signal. It is output to terminal 39.

In this way, if the winding angle of the magnetic tape around the tape guide drum is made slightly larger than 180° and the resulting overscan area is recorded with a time-base compressed audio signal using a rotating magnetic head, the The recording band is determined by the relative speed between the rotating magnetic head and the magnetic tape, and has little to do with the running speed of the magnetic tape. This enables high-density recording, that is, long-term recording and playback of video signals. Even if the running speed of the magnetic tape is slowed down, it is possible to faithfully record and reproduce audio signals. Moreover, since the audio signal track section 111 and the video signal track section 110 are separated, when audio after-recording is required, erasure is performed by applying an erasing magnetic field to the audio signal track section with the fixed erasing head 40, and then This allows new audio signals to be recorded using the magnetic heads 21 and 22, and has great effects.

[Brief explanation of drawings]

Fig. 1 is a main part configuration diagram of an embodiment of the present invention, Fig. 2
Figures a, b, c, Figure 3 a, b, Figure 4 a, b, c
5a and 5b are signal waveform diagrams of various parts in FIG. 1, and FIGS. 6 and 7 are diagrams showing examples of magnetization patterns of the magnetic tape in the present invention. 3... Video signal processing circuit, 4... Synchronization signal separation circuit, 5, 6, 11, 12... Gate circuit, 7,
8...Delay circuit, 9...Time axis compression circuit, 10...
...Modulation circuit, 13, 14, 30, 31... Adder, 15, 16... Changeover switch, 21, 22...
...Rotating magnetic head, 23...Magnetic tape, 28,
29... Separation circuit, 34... Time axis correction circuit, 3
5... Demodulation circuit, 38... Time axis expansion circuit, 40
...Fixed erase head, 103, 104, 105,
106, 107, 108...Audio track, 11
1...Audio signal track section.

Claims (1)

[Scope of Claims] 1. A magnetic tape is wound around the outer periphery of a tape guide drum having two rotating magnetic heads so that there is a period during which the two rotating magnetic heads are in simultaneous contact with each other, and the magnetic tape is wound at a constant speed. Let it run,
A helical scan type video tape recorder using two rotating magnetic heads, which record video signals in units of one field by scanning each of the rotating magnetic heads in a direction diagonal to the direction of travel. The magnetic tape is configured such that the period during which the two rotating magnetic heads are in simultaneous contact with the magnetic tape is at least a period corresponding to the time length of the audio signal which is time-base compressed in units of one field period of the video signal. A tape is wound around the outer periphery of the tape guide drum in an angular range exceeding 180°, and a portion of the magnetic tape corresponding to 180° in the angular range is used as a video magnetic track, and the two rotating magnetic heads are used as video magnetic tracks. The magnetic tape is sequentially switched so as to be in contact with the track, and a continuous video signal is recorded in units of one field of the video signal.
The portion exceeding 180° is used as an audio magnetic track, and the rotating magnetic head that does not record the video signal of the two rotating magnetic heads is used to record a period corresponding to one field period of the video signal. The audio signal is sequentially compressed on the time axis to sequentially record the audio signal with continuous information, and during playback, the two rotating magnetic heads are switched so as to sequentially come into contact with the video magnetic track to record one field of the video signal. In addition to reproducing continuous video signals as units,
The audio signal is reproduced by sequentially switching the rotary magnetic head that is not reproducing the video signal and is in contact with the audio signal track, and the information recorded on the audio signal track section can be erased. 1. A video tape recorder comprising: a fixed erasing head having a fixed erase head disposed before said magnetic tape and said rotary head come into contact with each other. 2. A video signal processing circuit that frequency modulates the input video signal to be recorded, and a head switch pulse generating means that separates the vertical synchronization signal included in the input video signal to generate first and second pulse signals for head switching. and first and second gate circuits that gate the output of the video signal processing circuit with the first and second pulse signals to obtain video signals to be supplied to each rotating magnetic head, and audio to be recorded. a time-base compression circuit that compresses the time-base of a signal; a modulation circuit that pulse-code modulates the output of the time-base compression circuit; and a third gate that gates and extracts the output of the modulation circuit with the second pulse signal. a fourth gate circuit that gates and extracts the output of the modulation circuit with the first pulse signal; and a fourth gate circuit that adds the output of the first gate circuit and the output of the third gate circuit; a first adder for obtaining a signal to be supplied to the other rotating magnetic head; and a first adder for adding the output of the second gate circuit and the output of the fourth gate circuit to obtain a signal to be supplied to the other rotating magnetic head. 2. The video tape recorder according to claim 1, wherein the video tape recorder includes two adders. 3. The carrier color signal included in the video signal to be recorded is converted to a low frequency signal and is recorded with its phase rotated by a predetermined amount every predetermined horizontal scanning period. The video tape recorder according to item 1 or 2.