JPS61187186A - Magnetic tape and magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve erasure effects by detecting the position of a margin from a signal generated in response to the rotation position of a rotary magnetic head and recording an index signal for the 1st or 2nd information to the margin. CONSTITUTION:The track 2 formed tiltedly in the lengthwise direction of a magnetic tape 1 is divided into the 1st part on which the 1st information is recorded and the 2nd part on which the 2nd information is recorded, and the 1st part is divided into a part (b) recorded with a clock signal, a margin (c) for after recording and a video overlap part (d) recorded continuously with the said field video signal, and the index signal for the 1st or 2nd information is recorded on the margin part (c). Thus, the recording/erasure of the index signal is attained without special provision of the fixed head to improve the erasure effect.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic tape for recording and reproducing information using a rotating magnetic head such as a video tape recorder, and a magnetic recording and reproducing apparatus thereof.

[Conventional technology]

2. Description of the Related Art In magnetic recording and reproducing devices such as video tape recorders, a tape counter is sometimes used to search for a predetermined recording or reproducing position. However, searching using a tape counter has the drawback of lacking accuracy. Therefore, a control signal (CTL signal) for tracking control consisting of 307 rectangular wave signals generally obtained from a pulse generator of a rotating drum may be used for the search. Since the CTL signal only uses the timing of one edge for tracking, a signal with a changed duty can be used as a cue signal (cue signal or index signal) for position search. .

However, such a search method using CTL signals requires a fixed head placed corresponding to the track where the CTL signal is recorded and an additional circuit around it. Like a tape recorder, each track has tracking pilot signals f□, f2, f3, f4 (each, for example, 6.5 f
l, 7.5f*, 10.5fi, 9.5fa
(fs is the frequency of the horizontal synchronization signal)) is recorded, and CT
Basically, it cannot be used in devices that do not require the L signal. If adopted, a fixed head or the like, which is basically unnecessary, would have to be specially provided just for searching. Furthermore, when recording a plurality of indexes corresponding to one inclined (video) track on one cue track, a special recording method such as time division is required, making the apparatus complicated and expensive. The frequency of the reproduction signal from the cue track is several tens of times higher during fast forwarding or rewinding than during normal recording and reproduction.

It is extremely difficult to extract an index signal for each track by processing significantly changing frequencies, periods, waveforms, amplitudes, etc. Furthermore, since the cue track is located near the edge of the magnetic tape, it is easily damaged by the tape guide.

The inclined track of the 8m video tape recorder is formed with a first part in which first information is recorded and a second part in which second information is recorded, and the first part is further connected to a clock signal. There is a recording section a, a section where data such as PCM audio signals are recorded, a margin section C for after-recording, and a video overlap section d where the video signal of the immediately previous field is continuously recorded. However, the present applicant previously proposed recording an index signal in this portion d (Japanese Patent Application No. 59-27).
7972 or Japanese Patent Application No. 6O-2464).

[Problem that the invention seeks to solve]

However, when recording an index signal in the video overlap section d, the recordable length is the maximum, considering the accumulation of errors in the recording position and playback head switching position allowed by the 8m video tape recorder standard. However, it has the disadvantage that it is 0.8H (H is the horizontal scanning period), which becomes about 0.5H when allowance for erasing is taken into consideration.

Therefore, in the worst case, the video signal recorded in the video overlap area d will be erased, and if the head switching signal exceeds the allowable range and fluctuates further toward the video overlap area d, the fluctuation will exceed the standard. However, since there is no margin at all, there is a drawback that a missing period occurs in the reproduced video signal.

[Means for solving problems]

FIG. 1 shows a block diagram when the magnetic recording/reproducing apparatus of the present invention is applied to an 8m video tape recorder.

In the figure, reference numeral 11 denotes a rotating drum, into which a rotating magnetic head (not shown) for recording or reproducing is mounted. 1
2 is a motor that rotates the rotating drum 11. Reference numerals 13 and 14 denote a frequency generator and a pulse generator, respectively, which output signals of a frequency and phase corresponding to the rotation of the rotary drum 11, and the outputs thereof are supplied to a servo circuit 15. The servo circuit 15 outputs a rotation control signal to the motor 12 and also outputs a head switching signal (H8WP signal) for switching a plurality of rotating magnetic heads. This head switching signal is supplied to a pulse generation circuit 17 via a variable delay circuit 16 provided as required. The pulse generating circuit 17 outputs pulses that control the on/off state of the switch 18.26. Reference numeral 19 denotes a control device comprising a microcomputer or the like, which controls the on/off states of the switches 2o and 21. 22 is a recording amplifier that amplifies a signal supplied to a rotating magnetic head for recording or reproducing information. 23 is an index circuit which outputs an index signal to the adder 24 via switches 26 and 20 and detects the index signal from the reproduction signal of the preamplifier 25. Reference numeral 27 denotes a position detection circuit which detects a predetermined position from the reproduction signal supplied from the one-rotation head.

[Effect]

The operation thereof will be explained with reference to FIGS. 2 to 6. The recording amplifier 22 receives video signals, audio (PC
M) Signals to be recorded, such as signals and tracking pilot signals, are supplied from a video recording circuit, a PCM recording circuit, a tracking recording circuit, etc. (not shown), and these signals are recorded on the magnetic tape by a rotating magnetic head. be done. During this time, the servo circuit 15 compares the signals from the frequency generator 13 and the pulse generator 14 with a reference signal, and controls the rotation of the motor 12 in response to the error signal.

During reproduction, a reproduction signal from the rotating magnetic head is amplified by a preamplifier 25 and supplied to a video reproduction circuit, a PCM reproduction circuit, a tracking circuit, etc.

FIG. 3 shows how signals are recorded on the magnetic tape in this manner. That is, tracks 2 are formed on the magnetic tape 1, which are inclined with respect to its longitudinal direction. For convenience, the track 2 includes a first part corresponding to a winding angle of about 36 degrees of the magnetic tape 1 with respect to the rotating drum 11, and a first part corresponding to a winding angle of about 18 degrees.
a second part corresponding to the fifth, and the former has a PC
M audio signal and tracking pilot signal (T
PS signal), and the latter also has an FM video signal.

An FM audio signal and a tracking pilot signal can each be recorded. In one of the adjacent tracks 2 in the positive direction and in the other in the negative direction,
The azimuth angle of each corresponding rotating magnetic head is inclined by about 10 degrees, so that crosstalk from adjacent tracks is reduced. An audio track 4 having a width R is formed near one edge 3, and a normal analog audio signal can be recorded by a fixed head if necessary. There is a width C near the other edge 3.
A cue track is formed, and cue signals are recorded by a fixed head as necessary. 5 and 7 are guard tracks provided between the information recording track and the control signal recording track.

FIG. 4 shows one track 2 on an enlarged scale. That is, the first part further includes a part a where a clock signal is recorded, a part where data such as a PCM audio signal is recorded, and a margin part C for after-recording.
and a video overlap section d where the video signal of the immediately previous field is continuously recorded.

The end position of the portion d is the switching position of the rotary magnetic head, and the vertical synchronizing signal is located at a position separated by a distance e from there. The length of each of these parts is, for example, 525 lines or 6 lines as in the case of the NTSC system.
o field system.

For example, 625 lines as in the PAL system,
In a 50-field system, the settings are as shown in the table.

Fig. 5 shows a case where a plurality of parts corresponding to the first part are formed in part 2 (part d can be considered to be included in the second part, but for convenience, it is included in the first part. ), that is, the length of the first part is an integral multiple of approximately five times the length of the second part, and the second part has five parts corresponding to the first part. forming parts a to d
For example, a PCM audio signal is recorded in each of the six parts in total.

Next, the recording and reproducing operation of the index signal will be explained. In the present invention, the index signal is recorded in the margin section C of the first section of the track 2. Part C is NTS
It has a length of 3.0H in the case of the C system (3.6H in the case of the PAL system). The servo circuit 15 receives outputs from a frequency generator 13 and a pulse generator 14 corresponding to one rotation of the drum 11.

For example, by counting a predetermined Glock pulse, a predetermined delay time is obtained as necessary, and a head switching signal is output (see FIG. 2(a)). This signal is transmitted to the variable delay circuit 1.
6 to the pulse generating circuit 17 (the variable delay circuit 16 is not necessarily required if the track configuration is as shown in FIGS. 3 and 4). When a predetermined time has elapsed since the generation of the head switching signal (for example, 256.7 (26
2,5-3,8-3,0+1.0) When H has passed)
, that is, at the timing when the recording section of the index signal of section C arrives (FIG. 2(b)), the predetermined width (
For example, a recording pulse of 1.5H) is output, and during this time the switch 26 is turned on (solid line in FIG. 2(c)). In addition, in order to eliminate omissions in erasing and to prevent PCM data from being erased, the starting end is, for example, 0.5H from the end of the section.
apart, so that its end coincides with the end of part C,
For example, extend the length before and after the recording pulse by 0.5H to 2.5H.
An erase pulse having a length of H is generated and outputted, and the switch 18 is turned on during this period (broken line in FIG. 2(c)). When the index recording operation is performed, the control device 19 switches switch 2
0.21 is turned on, the index signal (FIG. 2(d)) inputted from the index circuit 23 via the switch 26.20 is converted into a bias signal (for example, several M)fz by the adder 24 (second Figure (e)) is added to
The signal is supplied to the recording amplifier 22 via switches 18 and 21 (FIG. 2(f)). Such operations take place over the period of time to be recorded (for example, several seconds). Therefore, a predetermined number of tracks 2 on which index signals are recorded in partial sections are formed.

For example, when a PCM audio signal is recorded on all of one track 2 as shown in FIG.

Switch 18 in six sections of one track 2
and 26 are turned on. In this case as well, since the basic timing is the same as in the cases shown in FIGS. 3 and 4, there is no need to provide any special circuit other than the variable delay circuit 16.

When erasing the index signal, the switch 21 is turned on, and the switch 18 is also turned on by the erase pulse. Therefore, only the bias signal is supplied to the rotating magnetic head. In this case, the erasing effect can be enhanced by setting the bias signal at a higher level than during recording.

In the above operation, the signals for controlling the switches 18 and 26 are generated using the head switching signal as a timing reference, so there is no error in the recording position on the magnetic tape during recording and playback, or when the signal is recorded on the first part. It is inevitable that the timing will shift due to a time axis error between the information recorded in the second part and the information recorded in the second part. Therefore, if a PCM audio signal is recorded in at least the first part, the position detection circuit 27 detects a synchronization signal indicating the start of data from the demodulated signal of the PCM audio signal.
The start point of part C or the end point of part C is detected using the signal obtained by decoding the data block address, etc. as a timing reference (Fig. 2 (g)), and indexing is performed in synchronization with this detection signal. A signal indicating the recording position of the signal may be generated. Therefore, in this case, the pulse generation circuit 17 uses the output of the position detection circuit 27 when a PCM audio signal is recorded, and the output of the variable delay circuit 16 when a PCM audio signal is not recorded, as a timing reference. As a result, recording pulses and erasing pulses are respectively generated to control the on/off of the switches 18 and 26.

When an index signal is recorded and reproduced in the margin section C in this way, the relationship between the position detection signal, recording pulse (recording area), and erasing pulse (erasing area) with respect to the absolute position on the magnetic tape is as shown in FIG. become. Figure 6(a) shows the case where there is no time axis error during recording.
Figure (b) shows the case where there is no time axis error during playback, and Figure 6 (c) shows the worst case where the time axis error during recording is +1° and the time axis error during playback is -1.5H. Each case is represented. It can be seen that even in the worst case, the length of the video overlap portion d is approximately 0°8H.

On the other hand, as in the conventional case, for example, the video overlap part d
When recording the index signal at the beginning of
If a time axis error of -1.5H occurs during playback, see Figure 7 (
When a time axis error of -1H during recording and +1.5H during reproduction occurs in FIG. 7(c), respectively.

That is, as shown in FIG. 7(b), when recording +1°5H,
In the worst case where a time axis error of -1.5H occurs during playback,
The length of the video overlap part d is approximately 0.8H, but
If you record the index signal over a length of 0.8H, there is no margin at all, so if you record the index signal over a length of ±1.5H,
If a time axis error exceeding the standard (±1.8H in the case of PAL system) occurs, part of the video signal will be lost. Furthermore, if a margin is to be provided, the length of the index signal recording section I must be shortened to 0.8H or less.

On the other hand, during a search, the magnetic tape 1 on which the index signal is recorded is fast-forwarded or rewound while being wound around the rotating drum 11. At this time, the index circuit 23 is 1
The index signal is detected from the reproduction signal supplied from the rotating magnetic head via the preamplifier 25, and when detected, the detected signal is output to the control device 19. In order to detect the index signal, a signal for gate-extracting only the reproduced signal in the vicinity of the index signal recording area of part C is synchronized with the output of the position detection circuit 27 and sufficiently includes fluctuations during high-speed tape running. Pulses with such a wide width may be generated and used.

The index signal is less affected by head azimuth,
It is desirable to use a signal with a frequency as low as possible so that it can be easily detected even when fast forwarding or rewinding.However, in part C, a high level pilot signal f with a frequency of 230 kHz or less should be recorded. has been punched to the standard.

This pilot signal f is used to control the height of a plurality of rotating magnetic heads during recording when a piezoelectric element or the like is used in the holding portion of the rotating magnetic head for tracking control. Therefore, the index signal is 230
It is possible to obtain a signal having a frequency higher than kHz, which can be sufficiently frequency separated from the pilot signal f, and furthermore, can be frequency separated from the low-frequency conversion color signal of about 740 kHz±500 kHz.

For example, if the frequency of the index signal is approximately 1.2 MHz, it is sufficiently separated from the frequency of the FM audio carrier of 1.5 MHz, and can be easily separated and detected. Of course, a plurality of frequencies can be determined as index signals, and the type of search, weighting, etc. can be determined.

In addition to recording or erasing an index signal when recording a video signal or an audio signal using a rotating magnetic head, it is also possible to record an index signal when reproducing a video signal or an audio signal using a rotating magnetic head. can. In this case, since the leakage of the index signal affects the output of the weak reproduced signal, it is preferable to appropriately mute the video signal and the FM audio signal when supplying the index signal.

〔effect〕

As described above, in the present invention, tracks are formed obliquely with respect to the longitudinal direction of the magnetic tape.

It is divided into a first part where the first information is recorded and a second part where the second information is recorded, and the first part is further divided into a part a where a clock signal is recorded and a part a where data such as a PCM audio signal is recorded. The recorded area is divided into a margin area C for after-recording and a video overlap area d where the video signal of the immediately previous field is continuously recorded. Since the index signal of the second information is recorded, it is possible to record and erase the index signal without installing a special fixed head, and it is possible to fast forward or rewind the magnetic tape while it is wound around the rotating drum. You can search by. Furthermore, even if a time axis error occurs, there is little risk that data or video signals will be lost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the magnetic recording/reproducing apparatus of the present invention, and FIG.
Figure 6 and Figure 6 are the timing charts, Figure 3 is 8m
4 and 5 are enlarged plan views of its tracks, and FIG. 7 is a timing chart of a conventional device. 1... Magnetic tape 2... Track 3... Edge 4... Audio track 5.7... Guard track 6... Cue track 11... Rotating drum 12... Motor 13...・
Frequency generator 14... Pulse generator 15... Servo circuit 16.
...Variable delay circuit 17...Pulse generation circuit 18.26...Switch 19...Control device 22...Recording amplifier 23...
・Index circuit 24...Adder 25...Preamplifier 27...Position detection circuit or higher

Claims (3)

[Claims] (1) A magnetic tape on which information is recorded on tracks inclined with respect to its longitudinal direction by a rotating magnetic head,
The track has a first part in which first information is recorded and a second part in which second information is recorded, and at least a clock signal is further recorded in at least the first part. It is divided into a part a, a part b where data such as a PCM audio signal is recorded, a margin part c for after-recording, and a video overlap part d where the video signal of the immediately previous field is continuously recorded. , a magnetic tape characterized in that an index signal of the first information or the second information is recorded in the margin part. (2) forming a first portion in which first information is recorded on a track inclined with respect to the longitudinal direction of the magnetic tape by a rotating magnetic head and a second portion in which second information is recorded; At least the first part further includes a part a where a clock signal is recorded, a part b where data such as a PCM audio signal is recorded, a margin part c for after-recording, and a video signal of the immediately previous field. When recording the first or second information, the position of the margin section is determined from a signal generated corresponding to the rotational position of the rotating magnetic head. A magnetic recording/reproducing device characterized in that the index signal of the first information or the second information is recorded in the margin portion. (3) forming a first portion in which first information is recorded on a track inclined with respect to the longitudinal direction of the magnetic tape by a rotating magnetic head and a second portion in which second information is recorded; At least the first part further includes a part a where a clock signal is recorded, a part b where data such as a PCM audio signal is recorded, a margin part c for after-recording, and a video signal of the immediately previous field. When reproducing the first or second information, detecting the position of the margin section from the reproduction signal of the first or second information; A magnetic recording/reproducing device characterized in that an index signal of the first information or the second information is recorded in the margin portion, and a search operation is performed using the recorded index signal.