JPH0397104A - Magnetic tape device - Google Patents

Abstract

PURPOSE:To enable rerecording with a high S/N equivalent to that of a new blank tape by once executing full width erasing before erasing and recording operation and further executing a second erasing operation in the recording operation. CONSTITUTION:A magnetic tape 20 is rewound from the position of a program searching signal A25a to the position of a program searching signal B25b in a state that the tape is abutted on a full width eraser head 41 and a sound and control head 43. At this time, the full width erasing operation is executed by the full width erasing head 41 and the recorded signal on the magnetic tape 20 is erased. Next, the recording operation is started from the position of the program searching signal B25b and the erasing operation is executed at first by the full width erasing head 41 in a tape traveling direction. Afterwards, video signals, audio signals and control signals are written by respective heads. Thus, rerecording can be executed with the high S/N equivalent to S/N in the case of the recording to the new blank tape.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a magnetic tape device typified by a VTR,
More specifically, the present invention relates to a device for erasing signals recorded on magnetic tape.

[Prior Art] FIG. 4 is a perspective view showing a tape running system of a general helical scan type VTR, and FIGS. 5 and 6 are plan views thereof. FIG. 7 is a diagram showing an example of a magnetic tape pattern recorded by such a VTR.

First, a conventional helical scan type VTR will be briefly explained with reference to FIG. The magnetic tape (20) wound around the supply reel (11) of the cassette (10) is placed on the artificial side guide roller (31). (32) and the exit side guide roller (33) to pull it out from the cassette (10). After the magnetic tape (20) comes into contact with the full-width erasing head (4l) and the impedance roller (5l), it is wound around the rotating drum (60). moreover,
The magnetic tape (20) has an impedance roller (52), an audio erasing head (42), and an audio/control head (
43), then the cab stan shaft (hereinafter referred to as
cab stan) (72) and pinch roller (
71). In this way, magnetic tape (20
) is sandwiched and pressed by the cab stan (72) and the vinyl roller (71), and by rotating the cab stan (72), it becomes possible to travel for recording and playback. Take the reel (12
) is wound up.

The rotating drum (60) is composed of a pair of an upper rotating drum (6l) and a lower fixed drum (62),
As shown in FIG. 6, the video signal is transmitted by the video head (63) built into the upper rotating drum (6l).
Video tracks (21) for channels 1 and 2 of magnetic tape (20). (22) is recorded.

In addition, the audio signal is sent to the audio/control head (43)
audio tracks (23), (24) of channels 1 and 2 of the magnetic tape (20)
The control signal is also recorded on the control track (25) by the control signal recording section of the audio/control head (43).

The full-width erase head (41) erases all video signals, audio signals, control signals, etc. that have been recorded on the magnetic tape (20), and the audio erase head (42) is used for so-called post-recording. It is for.

In this way, by bringing the magnetic tape (20) pulled out from the cassette (lO) into constant and accurate contact with each head, each signal can be accurately recorded and reproduced on the magnetic tape (20) as shown in FIG. can do.

Here, the erasing operation during recording will be explained.

First, the full-width erasing head (41) operates to erase the recorded information already recorded on the magnetic tape (20) over the entire width. That is, after completely erasing the recorded information on the magnetic tape (20), the rotating video head (63) records the video signal, and then the audio/control head (4) records the video signal.
3) Record the control signal on the control track and the audio signal on the audio track.

Naturally, since the magnetic tape (20) runs in the direction of the arrow, the full-width erase head (4L
) is installed. That is, each signal is recorded after erasing the entire width. The erase rate of the video signal at this time is shown by the broken line characteristic curve in FIG. 3, and if the erase current is selected to be 230 mA, the erase rate will be about 50 dB for the S-VHS tape.

[Problems to be Solved by the Invention] Since the conventional VTR is configured as described above, new recording can be performed to the extent that there is no problem even if the recorded magnetic tape is rerecorded. However, with VTRs that strive for high image quality, residual recorded information still remains, which poses problems in terms of S/N, compared to when recording with a completely new black tape. That is, as shown in Fig. 3, only about 50 dBL can be erased with one degaussing operation, and recording a new signal under this erased state is performed by a recording operation superimposed on the residual recording signal. This is not desirable.

This invention was made to solve the above-mentioned problems, and it is possible to re-record even a used recording magnetic tape that has been previously recorded with the same high S/N as recording on a completely new blank tape. The purpose is to obtain a VTR.

[Means for Solving the Problems] A magnetic tape device according to the present invention performs full-width erasing with a full-width erasing head by rewinding a section to be re-recorded on a recorded magnetic tape or by running the tape in a fast-forward operation. It is characterized by having means for performing the action.

[Function] The full-width erasing means of the present invention performs full-width erasing once before the erasing and recording operation, and then performs the second erasing operation after the recording operation, so the residual recorded signal component is significantly reduced and a new blank tape can be used. Signal recording can be performed with a high S/N ratio equivalent to that of

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure shows the recorded tape of this example, (25a)
, (25b) are cue signals A and B, for example, VH
In the S method, V I S S (VHS INDEXS
EARCH SYSTEM) signal, or V A S
S (VHSADDRESS SEARCH SYST
It is widely used and famous as a control signal track (25) as a control head (EM) signal.
43) can be written to any position.

Now, from the position of cue signal A (25a) to cue signal B
A case will be described in which another information is recorded between the positions up to (25b).

First, as shown in FIG. 4, the magnetic tape (20) is fully loaded, and the magnetic tape (20) is loaded with a full width erase head (41) and an audio/control head (43).
), perform a rewinding operation from the position of the cue signal A (25a) to the position of the cue signal B (25b), and at this time perform a full width erase operation with the full width erase head (41). The recorded signals on the magnetic tape (20) are erased.

At this time, cue signals A (25a), (25b
) is detected by the audio/control head (43).

Next, the recording operation is started from the position of cue signal B (25b). This recording operation is the same as the conventional recording operation, and as viewed in the tape running direction, first the full-width erasing head (4l) performs the erasing operation, and then the video signal, the digital signal, and the control signal are written by each head.

That is, before each signal is written, the recorded tape (
20), new information is recorded after the second full-width erase is performed.

Figure 2 shows a full-width erase head (41) and an audio erase head (41).
2) and an example of a drive circuit for the audio/control head (43). In the figure, (44) is an oscillation coil unit, and (45) is an oscillation transistor, which generally operates at 70KHZ.
The full-width erase head (4L) has a frequency of about 23
It is designed to pass an erase current of 0 mA.

In this way, when erasing is performed twice before writing a signal, an erasure rate of 70 dB or more can be obtained, as shown by the solid line in Figure 3, and the residual amount of the previously recorded signal is is first reduced to a non-problematic level. Even with an S-VHS tape using ultrafine magnetic particles for high image quality, an erasure rate of about 70 dB can be obtained, as shown in FIG. 3, which is exactly the same level as a new blank tape.

In the above embodiment, the first full-width erasing operation is performed in the rewind operation, but it may be performed in other modes such as a fast forward operation.

Although the first erasing section was specified using cue signals such as MATA, VISS, and VASS, it is also possible to erase everything from the position of the magnetic tape to the end position, or use the tape counter of the VTR as a reference. The first erasing may be performed by rewinding or fast forwarding the section.Furthermore, during the first erasing, the audio/control head (43) always sends a control signal (30 pulses per second). Since this is detected, the tape section corresponding to the time to be newly recorded may be erased based on this.

Further, in the above embodiment, the first erasing operation was performed in a fully loaded state, but the full width erasing head (41)
The first erasing operation may be performed with reference to the tape counter of the VTR under a herbal loading state in which the head is brought into contact only with the audio/control head (43) and cannot be brought into contact with the audio/control head (43).

In addition, in the above embodiment, a normal VHS recording method was explained, but a five-layer recording method such as the VHS-HI FI recording method (HI FI audio signal is deep recording, video signal is superficial recording) This is even more effective when performing a new recording operation on a magnetic tape that has previously been recorded.

[Effects of the Invention] As described above, according to the present invention, prior to the normal erasing/recording operation, full-width erasing is performed and the full-width erasing operation is performed twice, and then the recording operation is performed. This has the effect of providing a high S/N magnetic tape device that can almost completely erase already recorded magnetic tape (even one that has been deeply recorded) and can attenuate residual recorded components by 70 dB or more.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a recorded tape pattern of an example of the present invention, FIG. 2 is a full-width erase head drive circuit diagram of this embodiment, and FIG. 3 is a diagram showing the full-width erase rate of the conventional example and this embodiment. FIG. 4 is a perspective view showing the full loading state of the VHS system VTR, FIG. 5 is a plan view also showing the full loading state, and FIG. 6 is a plan view showing the unloading state. FIG. 7 is a diagram showing a magnetic tape pattern recorded on a conventional VTR. (20)...Magnetic tape, (25)...Control track, (25a), (25b)...
Cue signal, (41)...Full-width erase head, (43
)...Voice/control head. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) Prior to erasing and re-recording a recorded magnetic tape, a means is provided for performing full-width erasing on the section of the magnetic tape to be re-recorded while rewinding or fast-forwarding. Features of magnetic tape device.