JPH04345902A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To reduce the disturbance caused by the residual component of a recording signal by setting the frequency of an erasion signal in a prescribed range and also setting a current at a level higher than the current serving as a MOL. CONSTITUTION:A rotary drum 24 is provided together with the recording heads 13-16 provided on the drum 24, the flying erasion heads 20-23, 8 means which winds a magnetic tape around the drum 24, a servo circuit 29 which controls the revolution of the drum 24 and the run of the tape 17, a means which supplies the recording signals to the heads 13-16, and a means which supplies the erasion signals to the heads 20-23. The frequency of the erasion signal is set in a range of 0.5f-1.5f with respect to the highest frequency f (= 1/2T, T: minimum magnetization inverting time width) of the recording signal. At the same time, the current of the erasion signal is set at a level, higher then the current that ensures the highest residual magnetization level.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flying erase method in a digital video tape recorder (hereinafter abbreviated as DVTR).

0002

[Prior Art] A D2 format DVTR (hereinafter referred to as D2VTR) that records a composite signal is used as a professional DVTR.
). For D2VTR, the Television Society technical report ITEJ Technical report
t vol. 12. No. 56. pp37-42 VR
As described in '88-61 (DEC. 1988), M2 modulation is adopted as a method for modulating the recording signal, and low-frequency components of the recording signal that tend to remain in magnetic recording are suppressed. For this reason, when overwriting a recording tape, the new signal is recorded directly over the previously recorded data, assuming that there will be no influence from the residual components of the previously recorded signal. It is not equipped with an erase head. In an analog VTR, a flying erase head is provided to completely erase previously recorded recording signals when overwriting is performed during editing. And the erase signal supplied to this is
By employing a frequency outside the recording band, it is possible to prevent interference caused by the erasing signal in recording after erasing.

0003

As described above, in a D2 VTR, when overwriting is performed by editing, a new signal is directly recorded over the previously recorded signal without erasing it. Therefore, when overwriting with a VTR with different recording characteristics, if the recording current level of the previously recorded VTR is higher than the current level of the newly recorded recording signal, or even if the recording current level is the same, Since the recording characteristics change due to the wear of the recording head, if the recording depth of the previous recording signal is deeper than the recording signal to be overwritten, there will be more residual components of the previous recording signal, which will have a negative effect on the error rate. affect Therefore, as a countermeasure to this problem, we decided to provide a flying erase head. but,
As with conventional analog VTRs, if the frequency of the erase signal supplied to the flying erase head is set to a frequency outside the recording band to prevent interference, the highest frequency of the recording signal in the D2VTR is as high as 32 MHz, and the recording band is extremely large. This wide area makes it difficult to transmit signals in the tape and head systems, making it impossible to obtain a sufficient erasing current level and making it impossible to sufficiently erase the previously recorded signal. For this reason,
In order to sufficiently erase the previously recorded signal, it is better to use a frequency within the recording band where a higher current level can be obtained. However, if the signal is within the recording band, there is a problem in that residual components of the erased signal cause interference during recording after erasing.

[0004] An object of the present invention is to sufficiently erase previously recorded signals when performing flying erase on a DVTR to reduce interference caused by residual components of the previously recorded signals; The purpose is to reduce interference caused by residual components of the erased signal.

[0005]

In magnetic recording, the higher the frequency of the recording signal and the shorter the recording wavelength, the lower the output level reproduced by the reproducing head due to losses such as space loss and recording demagnetization. Furthermore, when a signal of a single frequency is recorded by changing the recording current level, the residual magnetization level on the magnetic tape reaches its maximum at a certain recording current level.
The playback head output level becomes maximum (hereinafter referred to as MOL). Further increasing the recording current level lowers the read head output level. The present invention focuses on this characteristic, sets the frequency of the erase signal to a frequency in the range of 0.5f to 1.5f, and sets the current level to a level higher than the current level that becomes MOL.

[0006]

[Function] By setting the frequency of the erase signal supplied to the flying erase head from 0.5f to 1.5f, a higher erase current level can be obtained in the tape and head system, and the amount of erased previously recorded signals can be increased. . and,
Compared to the case where the frequency is lower than 0.5f, the reproduction head output level of the erasing signal that interferes with recording after erasing becomes lower. In addition, by setting the erase current level to a level higher than the current level that becomes MOL, the amount of erase can be increased.
Furthermore, since the reproduction head output level of the erasing signal is also lowered, interference caused by the erasing signal can be reduced.

[0007]

[Embodiment] An embodiment of the present invention will be described below. FIG. 1 is a configuration diagram of a recording/reproducing system of a D2 VTR to which flying erase is applied. In FIG. 1, 1 is an input terminal for an audio signal, and 2 is an input terminal for a video signal. The input audio and video signals are quantized by three and four analog/digital converters, respectively. The quantized digital data is subjected to five or six outer correction code coders, and a correction code for outer error correction is added thereto. Then, the audio data shuffling circuit 7 and the video data shuffling circuit 8 rearrange the recorded data to disperse the influence of code errors. After shuffling, the audio data and video data are combined. Synchronization and ID codes are added to the combined recording data by a 9-bit sync and ID code generator, and a correction code for inner error correction is added by a 10-piece inner correction code coder to form a synchronous block. The synchronization code indicates a delimiter between synchronization blocks during playback, and the ID code indicates an address for identifying which synchronization block the recorded data is in. Inner error correction is then performed within the synchronization block. The output of the inner correction code coder 10 is an 11 channel coder.
M2 modulation is applied to suppress low frequency components of the recording signal that cannot be transmitted to the rotating drum. FIG. 2 is a diagram showing an example of a signal waveform when M2 modulation is performed. A is the original signal and the output of the inner correction coder 10, B is the channel coder 1
This corresponds to an output of 1. For example, when a signal like A is modulated by M2, it becomes a signal like B. The minimum magnetization reversal width of the signal after M2 modulation is T' as shown in the figure. If the time width at this time is T (minimum magnetization reversal time width), the highest frequency f of the recording signal supplied to the recording head is 1/2T.
For example, in a D2VTR, it is approximately 32 MHz. The modulated output signal of the channel coder 11 is amplified by 12 recording amplifiers and supplied to four recording heads 13, 14, 15, and 16. When a signal is supplied to the recording head, it is recorded on 17 magnetic tapes. Figure 3 shows the D2V
It is a helical track tape pattern diagram of TR. As shown in FIG. 2, the recording is azimuthal and guard bandless. Azimuth angle is ±1 for both recording and playback heads
It is 5°. Video sector 46 in the center of one track,
Audio sectors 47, 48, 49, and 50 each having two channels are recorded at the upper end and the lower end. Each sector is
It is made up of a collection of synchronous blocks. An erase signal oscillator 18 generates an erase signal for flying erase. The erase signal is amplified by a flying erase amplifier 19 and supplied to flying erase heads 20, 21, 22, and 23. Flying erase head 20
, 21, 22, and 23 are for erasing helical tracks already recorded by the recording head before overwriting. Regarding the number of heads, as shown in Figure 3, since a video signal and four channels of audio signals are recorded on one track, there are four recording heads and a flying erase head so that each of them can be rewritten during editing. There will be four. The azimuth angle of the flying erase head is set to 0°, whereas the recording and reproducing heads are ±15°, and the azimuth loss lowers the output level of the reproducing head of the erasing signal that interferes with recording after the flying erase. A rotating drum 24 is equipped with a recording head, a playback head, and a flying erase head, and as the drum rotates, the head scans. 25 and 26 are guide pins,
The magnetic tape 17 is wound around the rotating drum 24. 27 is a capstan, 28 is a pinch roller, and magnetic tape 17
run. A servo 29 controls the rotation of the rotary drum 24 and the capstan 27 that runs the magnetic tape 17. Reproduction heads 30, 31, 32, and 33 reproduce recorded signals on the magnetic tape 17. Playback head 30,3
The output signals 1, 32, and 33 are amplified by a reproduction amplifier 34, and an equalizer corrects the frequency characteristics in order to reproduce the recorded data without error. The M2 modulated signal is then demodulated into the original data by 35 channel decoders. The output signal of the channel decoder 35 is supplied to a synchronization detection circuit 36, which detects the synchronization code within the synchronization block and identifies the delimiter of the synchronization block. The output signal of the synchronization detection circuit 36 is supplied to an inner correction code decoder 37, performs inner error correction within the synchronization block, and is then divided into audio data and video data. These perform outer error correction on data that could not be corrected by inner correction using 38 and 39 outer correction code decoders, respectively. 40 is an audio error correction circuit, and 41 is a video error correction circuit, which corrects error data that cannot be corrected by outer correction by interpolation from adjacent correct data. Then, the reproduced signal is outputted through digital/analog converters 42 and 43. 44 is an audio signal output terminal;
5 is a video signal output terminal.

Next, the recording heads 13, 14, 15, 16
We will now explain how to set the recording current level supplied to the In magnetic recording, the higher the frequency of the recording signal and the shorter the recording wavelength, the lower the read head output level due to losses such as recording demagnetization and space loss, making it difficult to obtain a sufficient S/N ratio. For D2VTR, the maximum frequency of the recording signal is 32MHz
The recording current level is set so that a high S/N ratio can be obtained in the 32 MHz reproduction signal. Figure 4 shows 8M
FIG. 4 is a diagram showing the characteristics of the read head output level when recording on a magnetic tape by inputting signals of Hz, 16 MHz, and 32 MHz to the recording head and changing the recording current level. In the characteristics of recording a 32 MHz signal, as the recording current level increases, the reproduction head output level also increases, and the reproduction head output level reaches a maximum at a certain recording current level. Further increasing the current level lowers the read head output level. Therefore, in FIG. 4, the recording current level is set to Ir at which the read head output level is maximum. As for other low frequency component signals, if they are set to the same Ir, they will be recorded deeply and will remain during overwriting. Conventionally, D2VTR directly overwrites the previously recorded signal, so the low frequency components of the recorded signal are
The current level is set to be lower than Ir so that the error rate does not deteriorate due to the influence of residual components.

The setting of the erase signal supplied to the flying erase head in the D2VTR configured as described above will be explained. The playback head output of the erased signal after erasing the previously recorded signal interferes with the recording after erasing, so it must be made as low as possible. Therefore,
As mentioned earlier, azimuth loss lowers the playback head output level to reduce interference. In order to further reduce interference and sufficiently erase the previously recorded signal, the frequency and current level of the erase signal are set as follows.

First, the setting of the erasing frequency of the erasing signal supplied to the flying erase head will be explained. Figure 5
is the cancellation frequency of 0.5f, f, 1.5f (f=32
FIG. 4 is a diagram showing the characteristics of the erase amount when a recording signal recorded by setting the recording current as described above is erased by changing the erase current level using an erase signal set to MHz). The amount of erasure is defined as the difference between the playback head output level when reproducing a previously recorded recording signal and the playback head output level of the erased signal after erasing the recorded signal with the flying erase head. In order to erase the previously recorded signal and eliminate interference caused by its residual components, it is necessary to increase the amount of erasing as much as possible. In Figure 5, for any frequency,
The amount of erasing can be increased by increasing the erasing current level. However, when the erasing frequency is 1.5f, it becomes difficult to transmit signals in the tape and head systems, and the erasing current level cannot be increased compared to when the erasing frequency is 0.5f, resulting in a smaller amount of erasing. Therefore, if the frequency is higher than 1.5f, the previously recorded signal cannot be erased sufficiently, making it unsuitable as an erasing frequency. Therefore, 0.
Compare 5f and f. FIG. 6 is a diagram showing the characteristics of the read head output level when an erase signal is supplied to the flying erase head and recording is performed on a magnetic tape while changing the erase current level. As mentioned above, since the reproduction head output of the erase signal causes interference, this output level must be kept as low as possible. In Figure 5
Looking at the current levels that result in the same amount of erasure at 0.5f and f,
At 0.5f, it is I1, and at f, it is I2. Therefore, in FIG. 6, when comparing the reproduction head output level when the erasure amount is the same at I1 and I2, the reproduction head output level is higher when the erasure amount is 0.5f, and there is more interference. Therefore, if the erasing frequency is lower than 0.5f, there will be more interference due to the erasing signal, so it is not suitable as an erasing frequency. In this embodiment, if the cancellation frequency is set to f, the interference caused by the cancellation signal can be reduced compared to 0.5f. Furthermore, the erase current level can be higher than that at 1.5f, and the amount of erase can also be increased.

Next, setting of the erase current level will be explained. Figure 7 shows the playback head output level of the erase signal (residual amount of erase signal) when the erase frequency is set to f and the erase current level is changed to erase the recorded signal set as described above. FIG. 3 is a diagram showing characteristics. The residual amount is the difference between the read head output level at the erase frequency component when the previously recorded signal is reproduced and the read head output level at the erase frequency after erasing with the flying erase head. Since the residual amount becomes a hindrance in recording after erasing, it is necessary to reduce it as much as possible. In FIG. 7, the characteristics are similar to those in FIG. 6, and the residual amount of the erase signal becomes maximum at a certain erase current level Ip. If this value is exceeded, the residual amount becomes low. Therefore, if the erase current level Ie is set to a higher current level than the current level Ip that becomes MOL, then
The amount remaining after erasing will be smaller. Therefore, by setting the erase current level to a current level as high as possible than Ip, the amount of erase of the previously recorded signal will increase as shown in Figure 5, so that the interference caused by the residual components of the previously recorded signal can be reduced, and furthermore, Interference caused by residual components of the erased signal can also be reduced.

[0012] When such an erase current level is set, even if the flying erase head is worn out and the gap depth becomes shallow, post-erase disturbances can be further reduced. FIG. 8 is a configuration diagram of the magnetic head. 51
is a coil, 52 is a core, and 53 is a gap. When a signal current flows through the coil, magnetic flux is generated and passes through the core. Then, magnetic flux leaks at the gap, and the magnetic tape 1
7 is recorded. The magnetic flux increases as the signal current level increases. The gap depth is d in the figure, but d decreases as the head wears. When the gap depth becomes shallow, even if the signal current flowing through the coil is constant, leakage magnetic flux at the gap portion increases. Therefore, the signal current level becomes high when there is no wear on the head. FIG. 9 is a diagram showing the characteristics of the read head output level with respect to the erase current level when the flying erase head is worn out and the gap depth becomes shallow from d to d'. As shown in FIG. 9, if the current level that becomes MOL is Ip when the gap depth is d, then as the gap depth becomes shallower (d'), the leakage magnetic flux increases.
MOL occurs at Ip' lower than Ip. therefore,
Assuming that the erase current level is constant and is Ie, when the gap depth becomes shallow, the read head output level will be lower than before it wears out, and the interference will change in the direction of decrease, so the negative effect of flying erase will be Does not occur. In this embodiment, the recording head and the reproducing head are separate heads, but the recording head and the reproducing head may be the same.

[0013]

[Effects of the Invention] As explained above, according to the present invention, in the erase signal supplied to the flying erase head,
Set the erasing frequency to a frequency in the range of 0.5f to 1.5f, and set the erasing current level to a level as high as possible than the current level at which the residual magnetization level is maximum after erasing and the reproduction head output level is maximum. As a result, the amount of erasing of the previously recorded signal increases, and interference caused by its residual components can be reduced. Since the read head output level at the erase frequency after the flying erase is also lowered, interference caused by residual components of the erase signal can be reduced in recording after the erase. In addition, if the erase current level is set as above, when the flying erase head wears out and the gap depth becomes shallow, the output level of the playback head after flying erase will become even lower, and the interference will change in the direction of decreasing. Therefore, performing the flying erase does not cause any adverse effects.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a recording and reproducing system of a D2 VTR to which flying erase is applied.

FIG. 2 is an explanatory diagram of a signal waveform subjected to M2 modulation.

[Fig. 3] A diagram of a helical track tape pattern recorded on a D2VTR.

FIG. 4 shows the characteristics of the output level of the reproducing head when a single frequency signal is input to the recording head and the recording current level is changed.

FIG. 5 is a characteristic diagram of the erase amount of the previously recorded signal when the erase current level is changed.

FIG. 6 is a characteristic diagram of the read head output level when the erase current level is changed using the erase frequency of the erase signal supplied to the flying erase head as a parameter.

FIG. 7 is a characteristic diagram of the residual amount of the erase signal after flying erase when the erase current level is changed.

FIG. 8 is a configuration diagram of a magnetic head.

FIG. 9 is a characteristic diagram of the erase current level and the read head output level when the flying erase head is worn out.

[Explanation of symbols]

3, 4...Analog/digital converter 5, 6...Outer correction code coder, 7...Audio data shuffling circuit, 8...Video data shuffling circuit, 9...Synchronization, ID code generator 10...Inner correction code coder , 11... Channel coder, 12... Recording amplifier, 13, 14, 15, 16... Recording head, 17...
magnetic tape, 18... erase signal oscillator, 19... flying erase amplifier, 20, 21, 2
2, 23... Flying erase head, 24... Rotating drum, 30, 31, 32, 33... Playback head, 34... Playback amplifier, 35... Channel decoder, 36... Synchronization detection circuit, 37. ... Inner code decoder, 38, 39... Outer code decoder.

Claims (3)

[Claims] Claim 1: A rotating drum (24);
) on the recording heads (13, 14, 15, 16), flying erase heads (20, 21, 22, 23), means for winding the magnetic tape (17) around the rotating drum (24), and the rotating drum (24). ) and magnetic tape (17
), a means for supplying recording signals to the recording heads (13, 14, 15, 16), and a flying erase head (20, 21, 22, 2).
3) in a device comprising means for supplying an erasure signal to,
Flying erase head (30, 31, 32, 33)
The frequency of the erase signal supplied to the recording head (13, 1
4, 15, 16) of the highest frequency f(
f=1/2T (T is the minimum magnetization reversal time width),
A magnetic recording/reproducing device characterized in that the frequency is set in a range of 0.5f to 1.5f. Claim 2: A rotating drum (24);
) on the recording heads (13, 14, 15, 16), flying erase heads (20, 21, 22, 23), means for winding the magnetic tape (17) around the rotating drum (24), and the rotating drum (24). ) and magnetic tape (17
), a means for supplying recording signals to the recording heads (13, 14, 15, 16), and a flying erase head (20, 21, 22, 2).
3) in a device comprising means for supplying an erasure signal to,
Flying erase head (30, 31, 32, 33)
A magnetic recording/reproducing device characterized in that a current level of an erase signal supplied to the magnetic recording/reproducing device is set higher than a current level that provides a maximum residual magnetization level. Claim 3: A rotating drum (24);
) on the recording heads (13, 14, 15, 16), flying erase heads (20, 21, 22, 23), means for winding the magnetic tape (17) around the rotating drum (24), and the rotating drum (24). ) and magnetic tape (17
), a means for supplying recording signals to the recording heads (13, 14, 15, 16), and a flying erase head (20, 21, 22, 2).
3) in a device comprising means for supplying an erasure signal to,
Flying erase head (30, 31, 32, 33)
A magnetic recording/reproducing device characterized in that the frequency of an erasing signal supplied to the device is set to a frequency in the range of 0.5f to 1.5f, and the current level is set higher than a current level that provides a maximum residual magnetization level.