JPS5927978B2 - Magnetic tape recording and reproducing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape recording and reproducing method for recording and reproducing a signal (hereinafter referred to as a cue signal) for identifying a recording position on a magnetic tape.

Recently, high-density recording has progressed in magnetic tape devices such as VTRs, and it has become possible to record and play back four hours on a single cassette tape. As tape lengths became longer, the ability to locate the beginning of the tape became more necessary than before. In many conventional consumer magnetic tape devices, the number of rotations of the supply reel disk and take-up reel disk was counted to find the beginning of the beginning. It was impossible to cue. Various attempts have been made to simultaneously record a cue signal on a magnetic material surface that records video signals, audio signals, and control signals, but this is always difficult to achieve because it disrupts each signal or generates beads. It is. In particular, in video signal recording devices that include color signals, high frequency components converted to FM signals and low frequency components converted to low frequencies coexist, making it difficult to record a new cue signal on the same magnetic material surface, and The cost has always increased because the signals are subjected to various complex processing. Furthermore, since the tape running path and tape speed differ between the normal playback mode and recording mode and the fast-forward operation mode and rewind operation mode that require cueing, the magnetic surface on which each signal is recorded is different. It was not possible to record cue signals with high accuracy and separate them for playback. The present invention was made in view of the above-mentioned drawbacks, and provides a low-cost magnetic tape recording and reproducing method that easily realizes recording and reproducing of cue signals without disturbing the original video signals, audio signals, and control signals. This is what we provide.

This invention will be explained in detail below using the drawings.

Figure 1 shows the tape running system of a parallel (M type) loading VTR in recording mode and playback mode.
Reference characters a and Ib are video heads that slightly protrude from and are fixed to the periphery of the rotating drum 1 and rotate at high speed together with the rotating drum 1. The two heads 1a and 1b are precisely indexed at 1800 degrees relative to the center of the drum.

2a, 2b, 2c are loading tape guides on the supply side, and 2a/, 2b', 2c7 are loading tape guides on the take-up side, both of which function to stably load the magnetic tape 3 on the rotating drum 1. The four tape guides 2b, 2c, 2b', and 2c' move during the loading operation as shown by arrows.

4a is a guide roller on the supply side, and 4b is an impedance roller called a take-up side guide roller to reduce small vibrations of the tape and reduce jitter.

5 is a full width erasing head, 6 and 7 are tape guides, and 8 is a tape tension regulator.

Reference numeral 9 is an audio erasing head, and 10 is an audio and control signal head. Generally, 9 and 10 are integrated to provide mechanical precision.

11 is a tape guide, 12 is a pinch roller, and 13 is a cap stan. The magnetic tape 3 is sandwiched between the pinch roller 12 and the cap stan 13.
It is advanced at a constant speed by the rotation of .

14 is a force set in which the magnetic tape 3 is stored.

Reference numerals 15, 16, and 17 are tape guides that are present in the force set and are used to smoothly supply and wind up the stored tape.

18 is a supply reel in the force set, and 19 is a take-up reel in the force set.

The head 20 records a cue signal on the back side of the magnetic tape, and is a rising head that mechanically rises up after the magnetic tape completes the loading operation, and is hidden behind the bottom of the main deck during the loading operation.

Reference numeral 21 denotes a playback head that rewinds the cue signal recorded on the magnetic material on the back side of the magnetic tape and detects it during fast forward operation.

Here, the full-width erasing head 5, the video heads 1a and 1b, the audio erasing head 9, and the audio and control signal heads are in contact with the magnetic surface A of the magnetic tape 3, so that they perform the recording operation on the magnetic surface A in the recording mode, respectively, and in the playback mode. A reproducing operation is performed on the magnetic surface A, respectively. On the other hand, the cue signal recording head 20 contacts the magnetic surface B (back side), and when the cue signal is applied to the head 20, it is recorded on the magnetic surface B on the back side. FIG. 2 shows a tape running system in the rewind and fast forward modes of an M-type loading type VTR, and the same reference numerals as in FIG. 1 indicate the same or corresponding parts. The loading guides 2b, 2c on the supply side and the loading guides 2b', 2c' on the take-up side are housed in the force set 14 as shown by the solid line arrows, and the tape guide 7 is also housed in the force set 14 as shown by the dotted line arrow. Ru. Therefore, as shown in FIG. 2, the above-mentioned respective guides 2b', 2c! ,2b,2c
is housed in the force set 14, and the magnetic tape 3 is passed from the supply reel 18 to the tape guide 15 provided in the force set.
, 16, 17 to the take-up reel 19. Conversely, when the loading operation is started, the moving guides 2b, 2c, 2b', 22c', 7 move as shown by the arrows to the positions shown in FIG. 1, and the magnetic tape is loaded on the rotating drum. In the rewind and fast forward modes, the tape runs at a speed 20 to 30 times faster than in the playback and record modes, as shown in FIG. The supply reel rotates at high speed in the rewind mode, and the take-up reel rotates at high speed in the fast forward mode. In both of these modes, the cue signal reproducing head 21 always comes into contact with the back surface (magnetic surface B) of the magnetic tape 3, reproduces the cue signal recorded on the magnetic surface B, and uses this reproduction cue signal to reproduce the respective cue signals. The rotation of the reels 18 and 19 is stopped, and the beginning of the magnetic tape 3 can be found at a predetermined position. FIG. 3 is a detailed enlarged sectional view of the magnetic tape 3.

Reference numeral 22 denotes a tape base material, which is generally about ten microns thick, and has a magnetic film 2 bonded to both sides with a binder (binding agent).
3a and 23b are present, and these are composed of chromium oxide or cobalt-based iron oxide.

The magnetic films 23a and 23b have a thickness of several μ and have a holding force of 5
00 oersted or higher is usually selected.

Here, 31 in FIG. 3 represents the video heads 1a, 1b, audio signal, and control signal heads 10, which contact the magnetic surface A and record a magnetic tape pattern as shown in FIG. 4A. I'll play it again.

On the other hand, a position identification signal recording head 20 and a position identification signal reproducing head 21, as represented by 24, come into contact with the magnetic surface B, and record a magnetic tape pattern as shown in FIG. 4B. Reproduce. In Figure 4A, 32,
33 is an audio track, 34a and 34b are video tracks, 35 is a control track, and 35a is a control signal. FIG. 4B is the reverse side of the magnetic tape pattern of FIG. 4A, and the magnetic tape pattern shown in FIG. 4A is shown in broken lines. A wide magnetic surface B exists approximately in the center of this back surface, and a cue signal 36 is recorded and reproduced on this portion. As is clear from the above-described structure, during the loading state shown in FIG. 1, the position identification signal recording head 20 records a position identification signal as shown in FIG. 4B on the magnetic surface B.

Of course, there are other heads 1a, 1b, 10 on the magnetic surface A.
As a result, a signal as shown in FIG. 4A is recorded. Further, in the unloading state shown in FIG. 2 (fast forward operation mode, rewind operation mode), the position identification signal reproducing head 21 shown in FIG. 2 reproduces the identification signal shown in FIG. 4B.
The other heads 1a, 1b, and 10 do not operate because the tape is not running on them. Now, considering the magnetic tape 3, in the video width area where the video signal is recorded, the video signal is recorded on the front side and the position identification signal is recorded on the back side. By setting the relationship between the head gap G of the recording head 20 and the reproduction head 21 and the head gap G2 of the video heads 1a and 1b as g1>G2, crosstalk between signals on the magnetic surfaces A and B can be eliminated. I can do it.

The reason for this is (a) First, there is a tape base material of tens of microns for a magnetic material surface of several microns, so magnetically 80% to
Separation of 90% or more is possible. (b) Since the magnetic path becomes long for recorded signals on the opposite sides, it is impossible to record or reproduce signals in a high frequency region, so crosstalk of high frequency components is completely eliminated. (c) As is well known, there is a relationship between the head gap g, the tape head relative speed ( ), and the possible recording frequency (f): g < 7 - (where λ is the possible recording wavelength). 4th selected in the relationship g1>G2
When a low frequency position identification signal as shown in FIG.

Generally, the gap of the video symbol head is 0.3 to 0.4.
Since it is very narrow in μm, it is easy to maintain the relationship g1>G2. (d) Since the video signal and the position identification signal have the angle of the recording and reproducing head, that is, the angle θ as shown in Figure 4B, the influence of the position identification signal on the video signal due to the azimuth loss effect is small. few. Generally, the azimuth loss is expressed as 2010g.

where λ: recording wavelength of the tape (λ-) j As is clear from the above equation, the azimuth loss is small for low-frequency signals with long recording wavelengths, but now the angle (θ) between the video signal in the video track direction and the position identification signal is Since it is large, it is easy to take a large azimuth loss.

For the reasons (a), (b), (c), and (d) above, the video signal and the position identification signal can be easily separated and recorded and reproduced.

Although the above description has been made regarding a parallel loading type VTR, it can be similarly applied to a magnetic tape device employing an α type or a U type loading system and a fixed head type acoustic tape device. Identification signal (cue signal)
Although FIG. 4B is given as an example, it is of course possible to use a coded pulse signal or an FM signal. As explained above, according to the present invention, it is possible to record a position recording identification signal without disturbing the conventional magnetic tape pattern. Furthermore, as explained with reference to FIG. 4, since the identification signal track width T can be sufficiently secured, the magnetic tape 3 runs at a considerably high speed during fast forwarding and rewinding operations, and the distance between the tape 3 and the reproducing head 21 is reduced. Even if mechanical running accuracy deteriorates, the recording position identification signal can be accurately detected.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the recording and playback operation modes of a parallel loading type VTR equipped with cue signal recording and playback functions of the present invention, FIG. 2 is a diagram showing rewind and fast forward operation modes, and FIG. 3 4A and 4B are diagrams showing the relationship between the magnetic tape and each head, and FIGS. 4A and 4B are diagrams showing the magnetic tape pattern on the magnetic surface.

Claims (1)

[Claims] 1. A first magnetic surface of the magnetic tape on which both or one of the video and audio signals are recorded, and a recording position identification mark on the surface opposite to the first magnetic surface of the magnetic tape. A second magnetic surface on which a signal is recorded is provided, and the gap of the recording head for the position identification signal that contacts the second magnetic surface is replaced by a gap of the recording head that contacts the recording strip of the first magnetic surface. A magnetic tape recording and reproducing method characterized by making the gap larger. 2. A magnetic tape recording and reproducing method according to claim 1, characterized in that a magnetic tape recording position identification signal is recorded or reproduced during rewinding or fast forwarding operations of the magnetic tape device. 3. A head for reproducing a recording position identification signal of a magnetic tape is installed in a position in a magnetic tape device where a tape cassette is to be inserted and fixed, and is brought into contact with a second magnetic surface. The magnetic tape recording and reproducing method according to scope 2.