JPH03127301A - Video tape recorder - Google Patents

Abstract

PURPOSE:To record and reproduce a video signal having high image quality without necessitating the tracking technology of high accuracy and to obtain high density in recording by making an angle which is made by the gap direction and the scanning direction of two rotary magnetic heads within specified extents respectively and using a perpendicular magnetic recording medium as a magnetic tape. CONSTITUTION:The video tape recorder is a helical scanning type video tape recorder having a following constitution; the magnetic tape 6 is wound around the outer circumference of a tape guide drum provided with the two rotary magnetic heads 1 and 2, and the two rotary magnetic heads 1 and 2 are made to scan in the direction oblique to the traveling direction 7 of the tape. And the angle theta which is made by the gap 10 direction of the two rotary magnetic heads 1 and 2 and the scanning direction 12 of the heads is set to be within the respective extents; +40 deg.<=theta<=+45 deg., -40 deg.<=theta<=-45 deg., and the perpendicular magnetic recording medium is used as the magnetic tape 6. Thus, the influence of the crosstalk of an adjacent track at the time of reproducing can be drastically reduced regardless of the width of a track and a recording frequency, and the special reproducing in a digital video tape recorder is performed without necessitating the tracking technology of high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a helical scan type video tape recorder that records video signals by scanning a magnetic head diagonally with respect to the running direction of a magnetic tape.

Conventional home video tape recorders use guard panless recording to reduce tape consumption and enable long-term recording. That is, this is a recording method that does not provide unrecorded portions (guard bands) between tracks recorded on the tape. In this recording method, crosstalk from signals of adjacent tracks becomes a problem if head tracking deviates during reproduction. Therefore, in home video tape recorders, the relative gap angle (azimuth) between two heads that record and play back adjacent tracks is adjusted by ±θ.
A recording method (tilted azimuth recording) is used that uses azimuth loss to reduce crosstalk. Here, the azimuth loss Laz is expressed by the following equation.

(πW/λ) jan2θ Laz−20log sin [(πW/λ) tan2θ] Here, W is the recording track width, λ is the recording wavelength, and θ is the azimuth.

[dB] The azimuth of the current system is θ=66 for the VH3 system, θ=7° for the β system, and θ-10'' for the 8IlII11 system.

As is clear from the above equation, the region where the recording wavelength λ is long,
That is, in a region where the recording frequency is low, the azimuth loss Laz is small, so azimuth recording alone is insufficient. In a home video tape recorder, this area serves as a color signal, so the line correlation is further utilized to remove crosstalk.

Problems to be Solved by the Invention When attempting to use the above-mentioned guard panless recording method adopted in current home video tape recorders in a digital recording method video tape recorder, crosstalk from adjacent tracks occurs during special playback. There was a problem in that the reproduced image was greatly disturbed by the interference caused by the interference. The reason for this is that when the pulse modulation method, which is suitable for digital recording, is compared to the analog modulation method, the signal-to-noise ratio of the output drops rapidly when the signal-to-noise ratio of the transmission path deteriorates to a certain extent. . This phenomenon is a fatal flaw in digital video tape recorders, which have significantly improved image quality. Guard band recording can be used to eliminate this crosstalk from adjacent tracks, but this recording method is not suitable for home video tape recorders where it is necessary to reduce tape consumption. therefore,
In the case of digital recording systems, high-precision tracking technology for magnetic heads is required to avoid crosstalk from adjacent tracks.

Means for Solving the Problems In the present invention, a magnetic tape is wound around the outer periphery of a tape guide drum having two rotating magnetic heads, and the two rotating magnetic heads are caused to scan in a direction diagonal to the running direction of the tape. A helical scan type video tape recorder, wherein the angle θ between the gap direction of the two rotating magnetic heads and the scanning direction thereof is +40°≦θ≦+45, respectively.
The above problem is solved by using a perpendicular magnetic recording medium as the magnetic tape.

Effect of the Invention With the above-described configuration, the present invention can record and reproduce high-quality video signals without providing a guard band even in a digital recording system and without requiring high-precision tracking technology, and further enables high recording density. This has the effect of being able to provide equipment.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1(a) is an explanatory diagram showing the concept of the present invention, which is composed of rotating magnetic heads 1, 2, guide posts 3.4, rotating magnetic head support 5, and magnetic tape 6. FIG. Furthermore, FIG. 1(b) and FIG. 1(C) are enlarged views of the vicinity of the gap of the rotating magnetic head 1°2.
, the rotating magnetic head 2 is tilted at an angle of one θ.

The magnetic tape 6 uses a perpendicular magnetic recording medium, and is guided by guide posts 3 and 4 located on both sides of a tape guide drum (not shown) containing a rotating magnetic head 1.2, and is guided by a capstan. The tape is run at a constant speed in the direction of arrow 7 by a well-known magnetic tape running device (not shown) comprising pinch rollers. It should be noted that since the tape guide drum used is a well-known one, a detailed explanation of its structure will be omitted here. During recording, the rotating magnetic head 1,
2 is rotated at a constant rotation speed in the direction of an arrow 8 by a rotating magnetic head support 5, and the recording signal is synchronized with the rotation speed and the signal is alternately supplied to each rotating magnetic head (not shown). ), signals are recorded alternately while scanning the magnetic tape 6 in a diagonal direction with respect to the tape length direction.

FIG. 2 shows a state in which the rotating magnetic head l deviates from its original position by ΔW and straddles the adjacent track 14. The arrows in the figure indicate the direction of recorded magnetization. At this time, the reproduction output from the track 13 decreases by 20 log (Δw/w) [dB] due to tracking deviation, but when the azimuth θ is set to 45°, no crosstalk from the adjacent track 14 occurs. because,
This is because the azimuth loss Laz becomes infinite from the above equation. In this case, the dependence on the recorded green wavelength λ or the trunk width W can be ignored because the azimuth effect is dominant. Therefore, since noise due to crosstalk does not occur, the signal-to-noise ratio of the reproduced signal is determined only by the reproduction output ratio, in other words, the tracking deviation ratio ΔW/W, and if there is a certain degree of tracking accuracy, the signal-to-noise ratio Significant decline can be prevented. Experimental results have confirmed that the accuracy used in conventional home video tape recorders is sufficient.

Here, we have explained the case where θ=45', but θ≧
If the azimuth loss Laz is 40 degrees or more, the contribution from the azimuth is dominant, and its absolute value is also large enough, so crosstalk from adjacent tracks during playback can be almost ignored, and the same effect as explained above can be obtained. can get.

Needless to say, this effect can be similarly obtained even when the rotating magnetic head 2 shifts to the adjacent track 13.

In addition, in this recording method, since the azimuth θ is considerably larger than in the conventional method, the effective relative velocity V between the rotating magnetic head and the magnetic tape is expressed as vo cOS θ, where vo is the relative velocity without azimuth. The larger the azimuth θ, the lower the effective relative velocity (2) and the shorter the recording wavelength λ.

As a result, the reproduction output decreases. Therefore, in order to overcome this problem, when recording is performed with a large azimuth θ, it is effective to use a perpendicular magnetic recording medium that has excellent short wavelength recording characteristics and high recording density characteristics. Therefore, the magnetic tape used is a perpendicular magnetic recording medium such as barium ferrite or CoCr, or a perpendicularly aligned magnetic tape using metal magnetic powder.

Effects of the Invention As described above, according to the present invention, the influence of crosstalk between adjacent tracks during playback can be significantly reduced, regardless of trunk width or recording frequency. This has the effect of allowing special playback of the tape recorder.

[Brief explanation of the drawing]

In FIG. 1, (a), (b), and (c) are explanatory diagrams showing the concept of the present invention, and FIG. 2 is an explanatory diagram showing tracking deviation during reproduction. 1.2...Rotating magnetic hend, 3.4...
・Guide post, 5...Rotating magnetic head support, 6...Magnetic tape, 7...Magnetic tape running direction, 8...Rotating magnetic head rotation direction,
9...rotation axis, 10...gap, 1
1... Magnetic head core, 12... Rotating magnetic head scanning direction, 13... Recording track by rotating magnetic head 1, 14...... Recording track by rotating magnetic head 2 record track.

Claims (1)

[Claims] A helical scan type video tape recorder in which a magnetic tape is wound around the outer periphery of a tape guide drum having two rotating magnetic heads, and the two rotating magnetic heads scan in a direction diagonal to the running direction of the tape guide drum, The angle θ between the gap direction of the two rotating magnetic heads and the scanning direction thereof is in the range of +40°≦θ+45° and −40°≧θ≧−45°, respectively, and a perpendicular magnetic recording medium is used as the magnetic tape. A videotape recorder characterized by: