JPH026492Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION ``Industrial Application Field'' This invention relates to a rotary head type recording device equipped with a rotary head for erasing.

BACKGROUND ART AND PROBLEMS THEREOF A rotary two-head recording device is known that records video and/or audio signals on a magnetic tape using a rotary head. Since the conventional rotary two-head recording device was composed of two heads,
Recording monitoring could not be performed, and if the gap in the head became clogged (referred to as head clog) during recording, it could not be detected. Head globs occur when magnetic powder peeled off from the magnetic tape gets stuck in the gap.

``Purpose of the invention'' The object of this invention is to provide a rotating head type recording device that is capable of detecting head grogs during recording.

``Summary of the invention'' This invention is a recording head that records information signals such as color video signals and audio PCM signals by interposing a no-signal section in a part of the track. , the rotary head is switched to a reproduction state within this no-signal interval, and a high-frequency signal for erasing is detected from this no-signal interval.

"Embodiment" An embodiment of this invention will be described below with reference to the drawings. In FIG. 1, 1 indicates a rotating drum, and this rotating drum 1 rotates clockwise at a field frequency. Rotating drum 1
On the other hand, rotary heads 2A and 2B for recording and one rotary head 2E for erasing are attached. The rotary heads 2A and 2B are arranged at an angular interval of 180°, and the rotary head 2E is arranged at an angular interval of 180°.
It is provided at a position that precedes A by an angular interval of 90°. Further, the rotating heads 2A and 2B are arranged at the same height. Furthermore, for recording the tilted azimuth, the extending directions of the respective gaps of the rotary heads 2A and 2B are different (for example, ±10°).
It is said that The reason for using one rotating head instead of two for erasing is to save on the number of heads.

Fixed tape guide drums (not shown) of the same diameter are provided above and below the rotating drum 1, and the magnetic tape 3 is wound obliquely around the cylindrical surface formed by these drums, and in this state, the magnetic tape 3 is wound in the direction of the arrow. The vehicle is run at a predetermined speed. The winding angle θ of the magnetic tape 3 is set to 180° or more, for example, 221°. Therefore, the rotating heads 2A and 2B are in sliding contact with the magnetic tape 3 within the range of the tape winding angle of 31 degrees.
In this overlap section, one field's worth of PCM audio signals compressed in the time axis are recorded. In this case, between the recording interval of the color video signal and the recording interval of the audio PCM signal,
In order to avoid the effects of signal switching transients, a no-signal interval of a period corresponding to an angular range of 3° is interposed.

Further, since only one rotary head 2E is provided, the erase track width of the rotary head 2E is set so that when scanning the magnetic tape 3 once, the area scanned by the rotary heads 2A and 2B can be erased in advance. It is larger than the track width of the rotating heads 2A and 2B. For example, the track width _H1 of the rotating heads 2A and 2B is 16 μm, and the track width _H2 of the rotating head 2E is 16 μm.
is said to be 40 μm.

Furthermore, in this embodiment, the magnetic tape 3 can run at two different speeds during recording. A first running speed and a second running speed which is 1/2 of the first running speed are possible, and this switching is performed by changing the speed of the capstan that runs the magnetic tape 3. The track pitch P ₁ at the first running speed is 20 μm, and the track pitch P ₂ at the second running speed is 10 μm. Figure 2 shows
This is to explain the recording operation in the case of the first running speed, and when the rotary head 2A starts to come into sliding contact with the magnetic tape 3 at the timing indicated by _t1 , the audio PCM signal is output in an area corresponding to an angular range of 28 degrees. is recorded,
Next, recording of the video signal is started at the timing indicated by _t2 after the no-signal section 4A of the section corresponding to the angular range of 3 degrees (indicated by diagonal lines). This no-signal section 4A
At this point, the rotary head 2A is brought into play.

When recording a color video signal, the luminance signal
Along with FM modulation, the color signal is converted to a low carrier frequency (for example, 688KHz). In the luminance signal, crosstalk from adjacent tracks is suppressed by using azimuth loss. For color signals, for example, the phase of the carrier signal recorded on one of the adjacent tracks is inverted every 1H (one horizontal interval) so that crosstalk from adjacent tracks can be removed by a comb filter installed in the reproduction circuit. and recorded. This recorded color video signal is recorded from the timing indicated by t ₂ to the timing t ₅ corresponding to an angular range of 180°, and after the timing of t ₅ , the rotary head 2A comes into contact with the magnetic tape 3 again. Until timing t ₇ , there is a blank running section.
The positional relationship of the rotary heads 2A, 2B, and 2E shown in FIG. 1 is at timing _t2 .

From timing _t4 , which is a time corresponding to the angular range of 31 degrees before the rotary head 2A reaches timing _t5 , the rotary head 2B begins to come into sliding contact with the magnetic tape 3, and audio is output in this overlap section.
A PCM signal is recorded by rotating head 2B.
In the subsequent no-signal period (indicated by diagonal lines) 4B, the rotary head 2B performs a reproducing operation. After time _t5 , a color video signal is recorded by rotary head 2B. In the overlap period ( _t7 to _t8 ), the audio PCM signal is recorded by the rotary head 2A.

Since the erasing rotary head 2E is provided at a position 90° ahead of the recording head 2A, the erasing current is supplied to the rotary head 2E at a timing earlier than the time corresponding to the angular range of 90°. Second
In FIG. C, a high frequency erase current of, for example, 3.5 MHz is supplied to the rotary head 2E during a period from t ₀ to t ₃ in which the rotary head 2E is in sliding contact with the magnetic tape 3, and an erase operation is performed. Due to this operation, the magnetic tape 3 has a track pitch as shown in FIG.
Even at P ₁ (=20 μm), tracks T _A and T _B are alternately formed by the rotating heads 2A and 2B. In FIG. 3, the locus indicated by the broken line is due to the rotary head 2E. Also, in Fig. 3, the timing t ₂
(See FIG. 2) shows the respective scanning positions of the rotary heads 2A, 2B, and 2E at a slightly earlier point in time.

Even if the running speed of the magnetic tape 3 is 1/2 of the above-mentioned speed, the audio
PCM signal and color video signal are magnetic tape 3
recorded in In this case, the track pitch is
P ₂ (=10 μm), a guard band is interposed between the tracks T _A and T _B , and an area with a width of 6 μm is recorded overlappingly. Furthermore, the pitch of the scanning locus of the rotary head 2E is also reduced to 1/2.

FIG. 4 shows the circuit configuration of an embodiment of the invention, in which a recording color video signal is supplied to an input terminal indicated by 5 and applied to one input terminal of each of switch circuits S ₁ and S ₂ . Further, an audio PCM signal is supplied to an input terminal indicated by 6, and applied to the other input terminal of each of the switch circuits S ₁ and S ₂ . These switch circuits S ₁ and S ₂ are connected to terminals 7 and 8.
It is controlled by switching pulses from. In other words, the switch circuits S ₁ and S ₂ switch the audio PCM signal during the recording period of the audio PCM signal.
Control is performed such that the other input terminal to which the signal is supplied is connected to the output terminal, and in other sections, the one input terminal to which the recorded color video signal is supplied is connected to the output terminal.

The outputs of these switch circuits S ₁ and S ₂ are sent to the recording amplifier 9.
The signal is supplied to the recording side terminals R of the switch circuits S ₃ and S ₄ via A and 9B. This switch circuit S ₃ ,
_S4 each has a reproduction side terminal P, and is controlled by a switching pulse supplied from terminals 10 and 11, respectively. During the period when the switch circuits S ₃ and S ₄ are connected to the recording side terminal R, recording signals are supplied to the rotary heads 2A and 2B via rotary transformers (not shown), respectively. Also, no signal section 4
At A, the switch circuit _S3 is connected to the playback side terminal P, and in the no-signal section 4B, the switch circuit S3 is connected to the reproduction side terminal P.
_S3 is connected to the reproduction side terminal P.

In FIG. 4, reference numeral 12 indicates an oscillation circuit that generates an erase signal, and e.g.
The 3.5MHz erase signal is sent to amplifier 13 and switch circuit.
S ₅ is supplied to the rotating head 2E via a rotating transformer (not shown). This switch circuit _S5 is controlled by a switching pulse from the terminal 14, and is turned on only during the period when the rotating head 2E is in sliding contact with the magnetic tape 3. This is to reduce power consumption.

The rotating heads 2A, 2B are in the no-signal section 4A, 4.
At B, the erasing signal is reproduced. 3.5MHz
The erase signal is a signal that remains sufficiently even when recording demagnetization (the gap length of the rotary head 2E is 2 to 3 .mu.m) is taken into consideration, and is a signal that can be sufficiently reproduced even if there is an azimuth loss. Further, the angular range of 3° is approximately 300 μsec in terms of time, and it is possible to switch between recording operation and reproducing operation. The reproduction signal taken out to the reproduction side terminals P of the switch circuits S ₃ and S ₄ is supplied to the tuning amplifier 15 . This tuning amplifier 15 has a high Q and is tuned to 3.5MHz.

The output of this tuned amplifier 15 is supplied to a detection circuit 16. The detection circuit 16 includes a rectifier circuit that rectifies the output signal of the tuned amplifier 15, and a comparison circuit that compares the output of the rectifier circuit with a reference level. This comparison circuit compares the output signal of the tuned amplifier 15 to see if it is higher than the reference level, and outputs the comparison result to the output terminal 17 as a detection signal. This detection signal is supplied to an alarm generating circuit such as a lamp or a buzzer, or a system control circuit that controls the operation of the VTR. It is determined that this has occurred, and an alarm is generated and the recording operation is canceled. Abnormalities that cannot be erased by the rotating head 2E can be detected. Generally 1
If a head clog has occurred in one rotary head 2E, it is determined that there is a high possibility that a head clog will occur in the other rotary heads 2A and 2B, or that a head clog has already occurred.

"Application Example" This invention can be applied to the case where only either a color video signal or an audio PCM signal is recorded, and in that case as well, a no-signal period may be provided.

This invention can also be applied to the case where one rotary head is used for recording. Furthermore,
Of the two rotary heads, only one of the rotary heads may reproduce the erase signal.

"Effect of the invention" According to this invention, it is possible to detect a head clock during recording. Furthermore, since this invention reproduces the erased signal in the no-signal period, it does not require a special pilot signal and can be implemented with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the arrangement of a rotary head in an embodiment of this invention, and FIGS. 2 and 3 are schematic diagrams of an imchart and a recording pattern used to explain the recording operation of an embodiment of this invention. , FIG. 4 is a block diagram of an embodiment of this invention. 1... Rotating head, 2A, 2B... Rotating head for recording, 2E... Rotating head for erasing, 3...
Magnetic tape, 12... erasure oscillation circuit, 15... tuning amplifier.

Claims (1)

[Scope of utility model registration request] At least one recording rotary head for recording an information signal with a no-signal section interposed in a part of the track; , an erasing rotary head for erasing an area of the recording medium in which a track is formed by the recording rotary head; a switching circuit for setting the recording rotary head to a reproduction state within the no-signal period; A rotary head type recording device comprising a detection circuit for detecting a high frequency signal for erasing from a reproduced signal passed through a switching circuit.