JPS59104707A - Magnetic recorder - Google Patents

Abstract

PURPOSE:To detect a fact that the video signal is not normally recorded on the magnetic track of a tape due to the clogging of a recording magnetic head of a miniature VTR or other factors, by reproducing the reference signal by a reproducing magnetic head which is set at a position different from the recording magnetic head on a rotary drum. CONSTITUTION:A reference signal is produced as shown in a diagram (a) by a reference signal generator 36 from a V synchronizing signal and another V synchronizing signal applied to an input terminal 35. The output signal of a switch circuit 40 is amplified by a band amplifier 41 having the central frequency of the reference signal and turned into another signal as shown in a diagram (b). The output of a wave detecting circuit 42 is turned into a signal as shown in a diagram (c). A gate pulse generator 43 produces a gate pulse as shown in a diagram (d). A gate circuit 44 detects whether a wave detecting signal of the reference signal exists in an ON period of the gate pulse. If no wave detecting signal exists in said ON period, a signal is sent to the head of the next stage, i.e. a display circuit 45 to light up an alarm LED. Thus an operator of a VTR knows that the recording is not carried out in a normal way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a VTR (television recording device) used for recording color television video signals.

(Conventional structure and its problems) Conventionally, in rotating drum type helical scan type VTRs, there have been cases where the magnetic head has become clogged during recording, or when some kind of accident such as a wire breakage has caused normal recording to fail. obtain. It is necessary to continuously monitor the recording state even during recording, and to immediately issue an alarm to inform the operator if there is an abnormality. This function is especially required for portable VTRs for broadcasting and business use.

In conventional portable VTRs for broadcasting, a magnetic head for simultaneous playback is provided separately from the magnetic head for recording, and a method such as recording and playing back at the same time, demodulating the video signal, and detecting the presence or absence of a synchronization signal of the playback video signal. However, for example, in a small VTR using a 7° inch cassette, especially in the case of a system in which the luminance signal and color signal are separated and recorded using separate magnetic heads, the rotating drum itself is very small, so it is difficult to record. It was not practical because it was difficult to connect the head and the playback head, making it difficult to obtain a playback signal sufficient for detection, and because the head was required for multiple tracks, the number of heads was extremely large. .

(Purpose of the Invention) The present invention is directed to a compact VTR that uses a magnetic tape with a width of 1 inch or even narrower. The purpose is to detect when a signal is not being recorded. In particular, in a system where luminance signals and color signals are recorded using separate magnetic heads, the recording status of multiple tracks can be detected simultaneously using one magnetic head. It is characterized by:

(Structure of the Invention) The present invention records a television video signal on a magnetic tape using a magnetic head, and superimposes a reference signal having a single frequency on the video signal to be recorded that is supplied to the magnetic head. The reference signal is recorded by the recording magnetic head, and the reference signal is recorded by the reproducing magnetic head, which spans a magnetic track on the magnetic tape and is located at a different position on the rotating drum than the recording magnetic head. By reproducing the magnetic track, it is detected whether or not the magnetic track is normally recorded.

There is also a demand for smaller size and lighter weight in the field of VTRs that produce high-quality images for broadcasting or professional use, and for broadcasting and professional use using conventional home-use inch-wide cassette tapes. VTRs that can withstand these conditions have been put into practical use.

In order to obtain high-quality images, such VTRs employ a so-called Y/C separation method in which a television signal is separated into a luminance signal and a chrominance signal and recorded using separate magnetic heads.

Therefore, when the above-mentioned Y/C separation recording method is used in a VTR having a general configuration of the helical scan method, the magnetic head on the rotating drum becomes as shown in FIGS. 1 and 2.

In FIG. 1, ■ indicates a rotating drum, and arrow 2 indicates its rotation direction. 3 and 3' indicate magnetic heads for recording luminance signals (hereinafter referred to as Y heads), 4 and 4' indicate magnetic heads for recording color signals (hereinafter referred to as C heads),
5 and 5' indicate heads according to the present invention, that is, detection and reproducing heads. Figure 2 is a head arrangement diagram of the Y and C heads seen from the surface that contacts the magnetic tape, and shows the head arrangement of the 3 and 3' heads.
is a Y head, and 4 and 4' are C heads, which are arranged in a staggered manner as shown in the figure. (7 Therefore X to Y, horizontal distance of D and C heads, y, ldY head and C
Indicates the vertical distance of the head. TY and TC indicate the widths of the Y head and C head. This is the same as the track width on magnetic tape. T8 indicates the space. 1st
FIG. 3 shows a pattern on a magnetic tape recorded by the Y head and C head shown in FIGS. 6 indicates a magnetic tape, and 7 and 8 indicate magnetic tracks recorded by the Y and C heads shown in FIGS. 3 and 4. 9 and 1o are Y head 3' and C head 4' shown in FIG.
shows the magnetic track recorded in In this way, one field of the television video signal is recorded on one set of tracks, and one frame of image is formed on a 2 m long track recorded by two sets of heads. 11 is a reference signal recording portion according to the present invention, and 12 is a reproduction head.

The reference signal 11 is located at an appropriate position within the vertical blanking of the video signal, and is set at a frequency as far as possible outside the frequency band of the FM-modulated recording video signal (generally several hundred on the low frequency side). In order to superimpose the signal (approximately a frequency of about kHz) on the recording video signal, the magnetic track is located at the position shown in FIG. 3, 11 on the magnetic track.

The playback head is installed at the positions shown in Fig. 1, 5 and 5', but the head height is adjusted so that it can be played on both the Y track and the C track on the tape pattern, as shown in Fig. 3, 12. The length and width are determined. Even if the head width spans both the Y and C tracks, the J
However, since the Y trunk usually requires better power - it is wider, the detection signal has a higher output level from the Y track, and when considering the signal processing from the C track. Although it is the same amount as the width of the C track, it has the advantage that subsequent signal processing can be simplified.

In Fig. 1, the playback gears 71+5 and 5' are installed at a position 90' away from the positions of the Y head and C head, but this 90° value itself has no great meaning; They just need to be separated by an easy angle. By separating the mounting position of the playback head from the recording head in this way, a time lag occurs between the superimposition period of the reference signal during recording and the detection period of the reference signal by the playback head. Even if there is crosstalk, only the reproduced signal can be detected because they are located at different positions in time.

゛Also, as shown in Figures 1 and 2, since the Y head and C head are mounted in a staggered position, recording will be made as far apart as possible (actually, the tape will not run relative to the head rotation). Strictly speaking, it is slightly different from the value of X), and if the superimposition period tR of the reference signal is 1R(-; If the setting is made so that the reference signal of both tracks is read simultaneously by the reproducing head, the reference signal detected by the reproducing head can be located at a position slightly separated in time.

If either the Y head or the C head is clogged and normal recording cannot be performed, the reference signal will naturally not be detected either, so it is very convenient to detect the Y and C signals separately.

FIG. 4 shows a waveform diagram of a reference signal and a detection signal according to the present invention.

Figure 4(a) is a reference signal superimposed on Y and C, and 20 is, for example, a frequency of 500 kHz and a width of 300μ.
If the current is approximately S, the amount of superimposition of approximately one tenth of the video recording current flowing through the Y and C heads may be sufficient. (b) is the reproduction reference signal obtained by the reproduction head, 21, - is the crosstalk component directly injected by the recording signal,
In the example of the present invention, 22 is the reproduction signal of the C track, and 23 is the Y
This is the track playback signal. The amplitude of each signal of 21°, 22, and 23 changes depending on various conditions. (c) is a waveform obtained by detecting the reproduced reference signal, in which 24 is a crosstalk component, 25 is a C signal, and 26 is a Y signal.

(d) is an example of a gate pulse for extracting Y and C of the detection signal respectively, 27 is for C, and 28 is for extracting the Y detection signal. −
Crosstalk components can be completely removed by Therefore, if the detection signal exists within the 27th and 28th gate period, it has been recorded correctly, and if even one is missing, the missing magnetic track is not being recorded correctly. . Note that the positions where the reference reproduction signals 22 and 23 in (b) appear are determined by the mechanical mounting position of the head, so 27.2 in (d)
The position of gate/gurus in number 8 is also determined by this.

With the above configuration, it is possible to continuously detect whether recording of Y and C is being performed normally even during recording.

Note that the period during which the reference signal is superimposed is defined as the vertical blanking period of the video signal, but this is intended to eliminate as much interference as possible to the recorded video signal, and is designed completely outside the band in terms of frequency. d. Of course, if it can be determined, there is no need to specifically set it within the above period.

(Description of Embodiment) An embodiment of the apparatus of the present invention is shown in a block diagram in FIG. 5 and will be described.

31 and 32 are Y and C signal input terminals for recording, 32 and 34 are respective recording amplifiers, and their outputs are sent to Y and C recording magnetic heads 3, 3' and 4, 4', respectively. Supplied. On the other hand, V synchronization signal, input terminal 35
In addition to the synchronization signal added to , the reference signal generator 36 generates the reference signal shown in FIG.
These are detected in the Y and C recording amplifiers, respectively, and are superimposed on the head recording current.

5 and 5' are heads, that is, detection playback heads, and 3
7 and 38 are head amplifiers for amplifying the head output to a sufficient level, 39 is a head switching pulse input terminal for supplying the necessary signal of the two heads to the next stage, and 40 is a switching circuit. The output signal of this switching circuit 40 has a reference signal frequency, for example, 500
The signal is amplified by removing unnecessary components by a band amplifier 41 having a center frequency of kHz, resulting in a signal shown in FIG. 4(b).

42 is a detection circuit, the output of which is the signal shown in FIG. 4(C). Reference numeral 43 denotes a gate pulse generator that generates gate pulses such as those shown in FIG. This detects whether a reference signal detection signal exists. If there is no detection signal during the gate or pulse ON period, a signal is sent to the next stage head, that is, the display circuit 45, and this causes an alarm LED to light up, etc. 9 The VTR operator This will notify you that recording is not being performed properly.

In addition, in Fig. 4, the case for detecting the reference signal is
Although the top pulse has been explained as shown in (d), it goes without saying that the pulse width, polarity, etc. are optimally set depending on the specifications of the gate circuit and display circuit to be used.

In the explanation of the present invention, Y and C are separated into two signals.
Concerning the two-head case of C and C, if three or more signals and heads are used, the detection signals are reproduced by the number of recording magnetic heads in FIG.
This can be easily handled by using a corresponding gate circuit and gate pulse. Furthermore, in the present invention, the reproduced reference signals are detected temporally by arranging the Y and C heads in a staggered manner. However, if multiple heads overlap, x =
Of course, in the case of Q, this can be handled by temporally shifting the reference signals superimposed on the Y and C signals during recording, and by making the detection circuits have the same configuration.

(Effect of the invention) The present invention provides the following remarkable effects.

(1) Since the influence of crosstalk between the recording head and the reproducing head can be completely ignored when continuously checking the recording state on the tape, the structure of the rotating cylinder can be made very simple. become. 1(2) Especially Y/C
Even in the case of a VTR with multiple heads, such as a separate VTR, the number of reproducing heads can be reduced to one, which simplifies the structure of the device and improves reliability.

(3) Since the structure of the signal detection circuit is simple, such as an amplitude detection circuit and a comparison circuit, it requires less space.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of a rotating cylinder according to the present invention, Fig. 2 is a diagram showing the arrangement of a recording head, Fig. 3 is a diagram showing a magnetic track on a tape, and Fig. 4 is a diagram showing recording and reproduction waveforms of a reference signal. The figure shown in FIG. 5 is a block diagram of the embodiment. ■...Rotating drum, 3, 3', 4, 4'...Magnetic head for recording, 5...Head for reproduction, 7, 9-Y
) Rack, 8, 1o... C) 7th rack, 12... Playback head, 11... Reference signal recording part, 2o...
・Reference signal, 22.23... Reproduction signal. JP-A-59-104707 (6) Figure 1 Figure 2

Claims (3)

[Claims] (1) A television video signal is recorded on a magnetic tape using a magnetic head, and a reference signal having a single frequency is superimposed and recorded on the video signal to be recorded that is supplied to the magnetic head, The magnetic recording head records the information on the magnetic track on the S-air tape.
and detecting whether or not the magnetic track is normally recorded by reproducing the reference signal with a reproducing magnetic head located at a different position from the recording magnetic head on the rotating drum. Magnetic recording device. (2) Separate the television video signal into at least two parts, a luminance signal and a color signal, and position recording magnetic heads corresponding to each separately in a staggered manner on a rotating drum to generate a reference signal with a single frequency. is superimposed on the at least two recording video signals at exactly the same timing, and the at least two recording video signals recorded by the recording magnetic head are superimposed on the magnetic tape.
Claim 1 is characterized in that at least two of the reference signals reproduced at temporally shifted positions are independently detected by a reproducing magnetic head spanning two magnetic tracks. ) The magnetic recording device described in item 2. (3) The television video signal to be recorded is separated into two signals, a luminance signal and a chrominance signal9, and the width of the magnetic track for the luminance signal is made wider than the width of the magnetic track for the chrominance signal. The width of the reproducing magnetic head and the height of the head mounting are set so that the width of the reproducing magnetic head that spans the tracks for the luminance signal track is the same as the width of the chrominance signal magnetic track. Characteristic Claim No. (
The magnetic recording device according to item 1) or item (2).