JPS61146080A - Method of magnetic recording, reproducing, erasing - Google Patents

Abstract

PURPOSE:To realize after recording of a high quality voice signal by enabling erasing with the erasing head of only the 2nd signal superimposed on a level lower than the 1st signal recorded level on the 1st signal track of the magnetic tape. CONSTITUTION:An image projection signal is supplied to a terminal 28, which is amplified by a recording amplifier 30 via the video signal processing circuit 29, thence recorded in a magnetic tape by rotating heads 8, 9, via a switch 31. On the one hand, the voice signal fed to a terminal 38 is amplified by a recording amplifier 40 through a voice signal processing circuit 39, and recorded in the magnetic tape by rotating heads 11, 12, via a switch 41. The recording of a voice signal by a recording level smaller than the recording level of the video signal is carried out on the same track as the track of the video signal. Consequently, in case of erasing only the voice signal by applying the output of an erasing oscillator 36 to the rotating heads for erasing 13, 14, through a switch 37, erasing can be easily performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a rotary head video tape recorder (hereinafter referred to as VT).
The present invention relates to a high-density magnetic recording, reproduction, and erasing method that records other signals such as code-modulated audio signals on tracks on which video signals have been completely recorded, and enables separate reproduction and erasure.

BACKGROUND OF THE INVENTION Conventional magnetic recording and reproducing devices, such as rotary head video tape recorders, are configured to record luminance signals and color signals forming a video signal on a video track, and record audio signals on a separate audio track. , two rotating heads with different azimuth angles for recording video signals,
Almost all of the magnetic tape used in so-called azimuth recording is made of gold.

Recently, in order to improve the performance of audio signal recording, a method of recording a frequency-modulated audio signal along with the video (a) signal on the video track of a VTR (e.g. Electronic Magnetic Recording Study Group material MR83-19, pages 9-14) has been developed. It has been put into practical use.The frequency allocation in the recording method is
FIG. 8 shows a diagram of the recording state in the depth direction of the magnetic tape.

In FIG. 7, 1 is a luminance signal including a frequency-modulated synchronization signal, and 2 is a low-band-converted carrier color signal. 3 is a frequency modulated (FM) signal of an audio signal, which is recorded in the band between the low frequency conversion carrier color signal 2 and the FM luminance signal 1 by the audio dedicated head at an azimuth angle different from that of the video signal head. .

As is clear from FIG. 7, the frequency-modulated audio signal is transferred to the magnetic layer 4 with a large recording current before the video signal.
The video signal is then recorded in the surface layer 4 of the magnetic layer 4. Note that 5 indicates the base film layer.

In the case of such a conventional example, the audio signal is recorded in FM, so the S/N ratio is high, the quality is good, and the sound quality does not deteriorate even if the tape running speed is slowed down, so it is suitable for long-term VTR recording. It can be said that this is one of the most effective recording methods. Moreover, it is noteworthy that it utilizes the deep layer of the magnetic tape magnetic layer, which was not previously used.

Problems to be Solved by the Invention However, the above-mentioned conventional example has a major problem. This is because the FM audio signal is recorded in its entire depth, making after-recording impossible. Traditionally, VTRs record video and audio on separate tracks, so
You can perform so-called after-recording, which allows you to record the audio while playing the entire video. However, as is clear from FIG. 8, since the audio signal is recorded deep, erasing or re-recording it would also erase the video signal, making after-recording impossible.

In view of the above problems, the present invention makes it possible to erase only the second signal (the first signal means a video signal, the second signal means, for example, an audio signal), which is a prerequisite for after-recording. The present invention provides a magnetic recording, reproducing, and erasing method that can easily realize after-recording of high-quality audio signals recorded and reproduced by frequency modulation (FM) and code modulation.

Means for Solving the Problems In order to solve the above problems, the present invention provides magnetic recording, reproducing, and
The erasing method is to erase a second signal recorded superimposed on the first signal track of the rotary head type "/TR" at a level lower than the recording level of the first signal using an erasing head. It is a structure that makes money by supplying a certain erasing current to erase the data.

Operation According to the present invention, the second signal is recorded at a small level on the track where the first signal is recorded, so that it is recorded on the very surface of the magnetic layer of the magnetic tape, and the erasing head It is possible to erase the second signal without affecting the first signal by supplying a weak erase current to the first signal. By setting the second signal as an all-audio signal and the first signal as a video signal, it becomes possible to erase the audio signal and perform after-recording without compromising the image signal kf%.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings. FIG. 2 is a recording state diagram in the depth direction of the magnetic layer for explaining the present invention in detail.

When recording a single image signal on a magnetic tape using a rotating head as before, the depth of the recording layer is 042 times the recording wavelength.
5 to 0.3 times, and current consumer VTRs have a multiplication factor of 0.3 to 0.3 times.
This means that the information is recorded to a depth of 0.8 μm, and considering that the thickness of the magnetic layer 6 of a general magnetic tape is 2 to 4 μm, there is a non-recording layer 6C as shown in FIG. do. The conventional example explained in FIGS. 7 and 8 utilizes this non-recording layer.

The present invention focuses on the fact that recording and reproducing video signals does not require a full S/N ratio for recording and reproducing digital signals and FM recording and reproducing audio signals. All broadband digital signals and FM audio signals are recorded on the second signal recording layer 6a. Note that 7 in FIG. 2 indicates a base film. The case of PGM audio recording will be explained below. For reproducing digital signals, the S/N is 1.
If it is 6 dB, the bit error rate will be about 10-5, which is close to a practical value. It is sufficient if a S/N of 20 to 30 (iB) can be secured with a margin. Therefore, digital signals to be recorded in a shallow layer should be recorded at a depth to the extent that the S/N satisfies the above value.Recording layer The depth of the digital signal can be controlled by the recording current, and if Eizukago is recorded at the optimum recording current (the recording current value that maximizes the playback output), the recording current of the digital signal will be It is okay to see ~.Of course, since the digital signal is recorded in a shallow layer after the recorded video signal, the playback output of the video signal will decrease, but the degree of this will be small because the recording layer for the digital signal is extremely thin, and as mentioned above. For example, the recording current value is about 3 to edB.Moreover, the noise due to the surface nature of the tape is recorded in a shallow layer, making it difficult for it to be directly involved in the reproduction of the video signal, resulting in modulation noise. As a result, the actual S/N deterioration of the video signal remains at about 2 to 3 dB.In this way, the S/N deterioration of the previously recorded video signal can be kept small and a practical bit error rate can be achieved. Digital signals can be recorded thereon.

By the way, if the occupied bands of the video signal and the digital signal are far apart, it is possible to obtain the desired signal from the reproduced signal using a filter, but it is necessary to consider the case where the two signals are close to each other or overlap. For example, it is necessary to make the azimuth angle of the rotary head for recording and reproducing video signals different from the azimuth angle of the rotary head for recording and reproducing digital signals.

Generally, it is known that when the gap direction of the reproducing head deviates by one term θ from the gap direction of the recording head, the following loss occurs.

However, Wnidrack width λ: Recording wavelength Therefore, the reproduction output of the video signal rotary head does not pick up the signal recorded on the digital signal recording layer 6a and reproduces only the video signal, and the reproduction output of the digital signal rotary head is The azimuth angle can be set so that only the digital signal is reproduced without considering the signal of the video signal recording layer 6b. For example, the azimuth angle Th of video and digital heads
30' to 31, it is possible to share the band of both signals over the entire band of 1.6 to 2M [12 or more with a practical track width. As a result, as shown in FIG. 4, the frequency-modulated luminance signal 1 and the low frequency-converted carrier chrominance signal 2 are frequency-multiplexed and recorded on the video signal recording layer 6b. A digital signal 16 can be recorded on the digital signal recording layer 6a. In the case of the frequency allocation shown in Figure 3, the S/N deterioration of the video signal is only 2 to 3 dB, and about 4 MI
IZ digital signals can be recorded, which means that
For example, this means that audio signals can be digitally recorded using PCJ, making it possible to record and play back audio signals much better than the audio FM recording explained in the conventional example shown in Figures 7 and 8. It shows.

Of course, digital signals can be used for other purposes than PCM audio signals. It is also possible to frequency modulate an audio signal instead of a digital signal, record it shallowly on the surface of the magnetic layer, and reproduce it.

As described above, after recording a video signal in the magnetic layer, it is possible to record an audio signal at a low level in the shallow portion of the magnetic layer. In the conventional example explained in FIG. 8, since the audio signal is recorded deep, it is not possible to erase only the audio signal. In other words, when an erasing magnetic field is applied from the surface of the magnetic layer, the video signal recorded on the surface layer is essentially erased.

In contrast, in this embodiment, the audio signal is recorded on the surface of the magnetic layer, so if the strength of the erasing magnetic field is set appropriately, the audio signal in the shallow layer can be completely erased without erasing the video signal in the deep layer. I can do it. Therefore, it is possible to erase the audio signal or perform after-recording by supplying an erasing current that erases only the audio signal in the shallow layer to the dedicated erasing section.

FIG. 4 is a diagram showing an example of the configuration of a rotary head group for realizing the magnetic recording/reproducing/erasing method of the present invention.

The magnetic tape 1o runs in the direction of the arrow, and the rotating cylinder 1
5 is a so-called rotating two-head helical type VTR which rotates in the direction of arrow B at 1 c s o Hz. In this case, the video signal head 8 contacts the tape before the digital signal head 11, and the video signal head 9 contacts the tape before the digital signal head 12. is set to ±6°, and the azimuth angle of digital heads 11 and 12 is set to ±6°.
The angle shall be 30°. With this configuration, a video signal is first recorded on the track on the magnetic tape, and then a digital signal is recorded on the shallow layer by a separate azimuth head. The recording current of each head is set to the optimal recording current for the video signal head 8°9, and a fraction of the above optimal current to the digital signal head, so that the digital signal is recorded only in the shallow layer. Set to .

Now, the rotary head 13.14 is an erasing head, and in this case is arranged so as to come into contact with the tape after the video heads 8, 9 and before the digital signal head 11.12. The erasing heads 13 and 14 erase signals recorded on the magnetic layer by supplying a high frequency current having a sufficiently large gap length so that no signal remains in the magnetic layer. Generally, as the erase current increases, the magnetic field generated by the erase head becomes stronger and the erase magnetic field penetrates deeper into the opposing tape magnetic layer. It is possible to erase only the recorded signal. That is, the erasing heads 13 and 14 can erase only the digital signals recorded in the shallow portion of the tape.

FIG. 5 is a schematic diagram showing the erasing and after-recording patterns in the entire tape thickness direction. Figure a shows the initial recording state, where the deepest part of the magnetic layer 1 on the base film is a non-recording layer 6G, on top of which there is an image signal recording layer 6b, and the shallower layer 6G. A digital signal recording layer 6& exists in a part of the portion. The figure shows the state in which this tape has been erased with the erasing heads 13° and 14.
The digital signal is erased and an erase layer 17 is formed. Since the erasing current is set so that the erasing layer 17 is slightly deeper than the digital signal layer 61, the digital signal can be recorded on the erasing layer 17 again at the same level as before. The situation is shown in C of the same figure, and the re-recorded digital signal k62
It is indicated by L'. By setting the erasing depth a little deeper than the recording layer for the second signal in this way, the second signal can be repeatedly recorded, making so-called after-recording possible.

Although the above-described embodiments have been described using AC erasing in which a high frequency current is supplied to the erasing head, the erasing magnetic field may be a direct current, in which case a direct current may be passed through the erasing heads 13 and 14. In general, DC erasing tends to cause secondary distortion in the next recorded signal, but when a digital signal is recorded after erasing as in the example, there is no direct deterioration of the main signal quality. Therefore, it is quite practical. Using direct current erasure has the advantage of simplifying the equipment, and is especially effective during after-recording because the high frequency waves used for erasure do not cause interference such as jumping into the image head during playback.

FIG. 1 is a block diagram of main parts of an embodiment of the present invention.

In the figure, an image signal is applied to a terminal 28, is amplified by a recording amplifier 30 via a recording/image signal processing circuit 29, is passed through a switch 31f! Recorded. Recording side video processing circuit 29
frequency modulates the luminance signal, low-pass converts the carrier color signal,
The luminance signal 1 is converted into the frequency band of the carrier color signal 2 shown in FIG.

Next, the audio signal applied to the terminal 38 passes through the recording side audio signal processing circuit 39, is amplified by the recording amplifier 40, passes through the switch 41, passes through the rotary head 11.12'i, and is recorded on the magnetic tape. The recording side audio signal processing circuit 39 performs code modulation (PGM) on the audio signal, converts the code into a format that is easy to record, and converts it into the frequency of the audio signal 16 shown in FIG.

Next, the time of reproduction will be explained. By changing the azimuth angle of the video signal recorded on magnetic tape and the digitized audio signal,
Playback using each dedicated head.

The video signal is reproduced by the rotary heads 8 and 9, passed through a switch 32ft, and amplified by an amplifier 33, then inputted to a reproduction side video signal processing circuit 34, demodulated to the original video signal, and outputted to a terminal 35. The audio signal is sent to the rotating heads 11 and 1.
2, the signal is amplified by an amplifier 43 via a switch 42, and then inputted to a reproduction side audio signal processing circuit 44, decoded into the original audio signal, and outputted to a terminal 45.

During erasing, the output of the erasing oscillator 36 is applied to the erasing rotating head 13, 14 via the switch 37, thereby erasing the audio signal recorded on the magnetic tape.

Now, let me explain about the after recording mode. In general, after-recording involves re-recording the audio signal while viewing the recorded video signal, erasing the audio signal while playing back the video signal, and recording another audio signal. Switches 31.37, 41.3 in the diagram
The states 2 and 42 are set to the after-recording mode, and the outputs of the video heads 8 and 9 are reproduced and a video signal is output to the terminal 35. Erasing head 13,1
4 is supplied with an erase current from an erase oscillator 36 to erase only the audio signal in the shallow layer of the magnetic tape. Immediately after erasure, the rotating heads 11, 12 come into contact with the tape and serve to record all new audio signals applied to terminals 3. As described above, in this embodiment, it is possible to record and reproduce images and audio signals, erase audio signals, and even realize an after-recording mode.

Note that the erase head 13.14 and the audio signal head 11.12
The scanning trajectories on the magnetic tape must be made to coincide with each other, but this can be easily accomplished by setting the relative positions of each head in the rotation angle direction and relative height.

FIG. 6 is a block diagram showing another embodiment of the present invention. In the explanation in Part 1, the signal recorded in the shallow layer is erased using a rotating head, but in this embodiment, the signal recorded in the shallow layer is erased using a fixed head, making after-recording possible. It is something.

In the same figure, the tape 10 exits the supply reel 18 and passes through the tension post) 20. Rotating cylinder 1 via entry post 21
6, a drive system consisting of an exit post 22, a capstan 23, and a pinch row 224 leads to a take-up reel 19. Here, the rotating cylinder 15 has video signal heads 8 and 9.
and audio signal heads 11 and 12 are mounted on the tower, but the erasing rotary head is not mounted on the tower. In this tape running system, control 1. ．． No. 3 and conventional direct recording audio signals are recorded and reproduced by the fixed head 27.

As is conventional, the full-width erasing head 26 is used to erase all the signals recorded by the fixed head 27 and the image signals recorded by the rotary heads 8 and 9. In this embodiment, in addition to these fixed heads, an erasing head 26 is arranged in front of the rotating cylinder in the tape running direction.

The erasing head 26 completely erases only the signals recorded in the shallow layer of the magnetic layer of the magnetic tape, and supplies alternating current or direct current to an appropriate value. The erasing head 26 is brought into contact with a portion of the magnetic tape where the image signal and the second signal are recorded, and erases only the second signal. Control signals and audio signals are recorded in saturation and bias on separate tracks in the tape width direction, but both are recorded in the second track.
The signal recording level is recorded at an overwhelmingly high level, reaching the deepest part of the tape magnetic layer. Therefore, even if the erasing head 26 is in contact with a control track other than the part where the second signal is recorded,
Since the erase magnetic field is small, it hardly affects anything other than the second signal. From this, it is also possible to easily erase only the second signal by setting the erase current of the full-width erase head 25 to a small value. The method described above uses a fixed head to completely erase the second signal recorded in the shallow layer, but the erasing head is placed in front of the rotating cylinder,
It goes without saying that the entire after-recording mode can be realized by switching 1.12 to the recording state and the rotary heads 8 and 9 to the reproducing state.

Effects of the Invention As described above, according to this embodiment, the second signal superimposed and recorded on the first signal (video signal) track of the rotary head type VTR at a level lower than the recording level of the first signal is recorded. By configuring the erasing head to supply an erasing current that causes the second signal to disappear, the second signal can be easily erased and rewritten to a new signal. Therefore, by using an audio signal as the second signal, it is possible to realize a so-called after-recording function in which the audio signal is re-recorded while monitoring the video signal. Of course, in addition to the conventional signal, recording and recording of a second signal is also possible.
Since it can be read and erased, it is also one way to achieve higher density magnetic recording.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a magnetic recording/reproducing/erasing method in one embodiment of the present invention, Fig. 2 is a recording state diagram in the depth direction of the magnetic tape for explaining the present invention in detail, and Fig. 3 is a frequency A diagram showing an example of allocation, FIG. 4 is a configuration example of a magnetic head group used in the present invention, FIG. 5 is a model diagram in the depth direction of the magnetic tape showing an erased state, and FIG. 6 is another embodiment of the present invention. FIGS. 7 and 8 are a diagram illustrating a conventional example, showing a frequency allocation diagram and a recording state diagram in the depth direction of the magnetic tape, respectively. 8.9...Video head, 11.12...Dan...
2nd signal head, 13.14...Rotating erase head, 36...Erasing oscillator, 6...Magnetic layer, 6a...2nd signal recording Layer, 6b...
...Video signal recording layer, 17...Erasing layer, 25...
...Full-width erase head, 26...Erase head. Name of agent: Patent attorney Toshio Nakao, 1st person, 2nd person
Figure 3 PI Namichichi (to MW) Figure 4 (Kyu) (b) Figure 6 Figure 7, 9 Yokyakukyo (M#zl Figure 8

Claims (8)

[Claims] (1) The second signal is superimposed and recorded on the first signal (video signal) track of the rotary head type VTR at a level lower than the recording level of the first signal, and the second signal is erased by the erasing head. A magnetic recording/reproducing/erasing method characterized by erasing by supplying an erasing current. (2) The magnetic recording/reproducing/erasing method according to claim 1, wherein the erasing rotating head is configured to be supplied with a high frequency current. (3) The magnetic recording, reproducing, and erasing method according to claim 1, wherein the magnetic recording, reproducing, and erasing method is configured to supply a direct current to the erasing rotary head. (4) A patent characterized in that the erasing head is a fixed head and is configured to be brought into contact with a portion in the width direction of the magnetic tape where the video signal and the second signal are recorded so as to erase the second signal. Magnetic recording/reproducing/reproducing according to claim 1
Erase method. (5) The magnetic recording, reproducing, and erasing method according to claim 4, characterized in that the current supplied to the full-width erasing head is reduced to erase only the second signal. (6) The magnetic recording system according to claim 4, characterized in that the fixed head for erasing is arranged in front of a group of rotating heads from which video signals are reproduced in the running direction of the magnetic tape. How to play/delete. (7) The erasing current is set so that the erasing depth by the erasing head is deeper than the recording depth of the second signal, and after erasing the second signal, another signal is re-recorded. A magnetic recording/reproducing/erasing method according to claim 1. (8) A first rotary head for recording and reproducing a first signal (video signal), a second rotary head for recording and reproducing a second signal, and a third head for erasing the second signal. have,
The magnetic recording device according to claim 1, further comprising an after-recording mode in which the first rotary head is in a reproducing state, the second rotary head is in a recording state, and the third head is in an erasing state.・How to play/delete.