JPS59146404A - Rotary head system of vtr - Google Patents

Abstract

PURPOSE:To secure the interchangeability with a video tape of another system and to reduce the size of a VTR by distributing at least four rotary heads equidistantly along the slit of a cylinder and winding a video tape around the cylinder by (n-1)/n turn. CONSTITUTION:For instance, (n) units of rotary heads H1-H4 (n: an even number of >=4) are distributed within a cylinder 1, and four units are arranged in this example and a video tape 5 is wound around the cylinder 1 by (n-1)/n turn, e.g. a little more than 3/4 turn. The radius r' of the cylinder 1 is set at n/2(n-1) compared with the radius (r) of double rotary head system, i.e. at 2r/3 in this example. The driving signals are switched by a driving signal switch circuit (not shown in the figure) and therefore applied to the heads H1-H4 which are positioned at the winding end position P3 of the tape 5 when each of the heads H1-H4 is turned up to the winding start position P2 of the tape 5. As a result, 30n/(n-1)rpm is secured in this example compared with 30rpm of the double rotary head system. Then 45rpm is possible with four rotary heads.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a rotating head for recording one field of video signals on a video tape in a video tape recorder (VTR) as a track in a direction diagonal to the running direction of the video tape. This invention relates to a rotating head method for helical scanning.

Conventional rotary head systems of this type include those shown in FIGS. 1 and 2. This rotary head system is a so-called two-rotary head system equipped with two rotary heads. In these figures, 1 is a tea cylinder-shaped cylinder, 2 is a head bar for attaching a rotating head connected to the shaft of a control motor (not shown) at the center of the cylinder 1, and H1 and H2 are each end of the head bar 2. the first, which is fixed to each, and is slightly exposed to the outside of the cylinder 1 through the slit 3 of the cylinder 1.
The second rotary head, 4, 4, is a tape guide, and 5 is a video tape. Arrow A indicates the running direction of the video tape 5, and arrow B indicates the rotation direction of each rotary head H1, H2.

In such a two-rotary head system, each rotary head H
The head speed v and rotation radius r of the rotary heads H1 and H2 are set so that the half rotation time t of the rotary heads H1 and H2 corresponds to one field of the video signal. Incidentally, recording of video signals on the video tape 5 using this method is shown in FIG.

In FIG. 3, TR1, TRr2, . . . are tracks on which video signals are recorded by the respective rotary heads H1, H2.

Arrow C indicates the direction of travel of the rotary head. However, the third
The figure shows the videotape 5 viewed from the magnetic surface. In such a rotating two-head system, if the length of the videotape 5 wrapped around the outer peripheral surface of the cylinder 1 is l, then the equation l=πr=vt is established between the half-rotation time t, the head speed v, and the rotation radius r. holds true.

In this equation, even if the rotation radius r is small, the half-rotation time t is always fixed at approximately 16.6 milliseconds, so by slowing down the head speed v, one field of video signals can be processed during a half-rotation. Can be recorded. However, if the rotation radius r is made smaller and the tape winding length l is made shorter, the inclinations of the recording tracks TR1, TR2, . . . in FIG. 3 become more perpendicular to the tape running direction. Therefore, there is no videotape compatibility between a VTR miniaturized by reducing the diameter of the cylinder 1 using this system and a VTR of the same system, which has a different cylinder 1 system.

An object of the present invention is to provide a rotary head system capable of downsizing a VTR by ensuring compatibility with video tapes of other systems even if the diameter of the cylinder is reduced. With the goal.

In order to achieve such an object, the present invention has n rotating heads (where n is an even number of 4 or more), each rotating head is arranged at equal intervals along the slit of the cylinder, and the rotating heads are arranged at equal intervals along the slit of the cylinder. Wraps the videotape for (n-1)/n rounds, and sets the switching timing of the head drive signal given to each rotary head when each rotary head rotates to the start position of winding the videotape around the cylinder. , the (n-1)/n rotation time of the rotary head corresponds to one field of the video signal, and the rotation radius of the rotary head is [n/2(n-1)]/r (where r is the number of rotations of the two heads). The radius of rotation of the rotary head in the

Hereinafter, the present invention will be explained in detail based on an embodiment shown in the drawings.

FIG. 4 is a plan view showing the schematic configuration of this embodiment, and FIG. 5 is a side view showing the same configuration.
Portions corresponding to those in FIGS. 1 and 2 are given the same reference numerals. This embodiment has a tea caddy-shaped cylinder 1.

Inside this cylinder 1, there are rotating heads H1, H2, H3,
n H4s (n is an even number of 4 or more), four in this embodiment, are arranged. This arrangement is at equal intervals along the slit 3 of the cylinder 1, in this example every 90°. The first and second rotating heads H1 and H2 are attached to the head bar 2, and the third and fourth rotating heads H3 and H4 are attached to the other head bar 2.
′, respectively. Both head bars 2, 2' are fixed to the shaft of a control motor (not shown) at the center of the cylinder 1, so that they can be rotated integrally with each other. 4, 4, and 5 are the same as in FIG.

In this cylinder 1, the video tape 5 is (n-1)/n
Can be wrapped around. The radius r' of this cylinder 1 is n/2 (n-1) of the rotation radius r of the rotating two-head system, ~H
4 is supplied with a drive signal from a head drive signal circuit (not shown), and this drive signal is supplied only while each of the rotary heads H1 to H4 is in contact with the video tape 5 through the slit 3 of the cylinder 1. This drive signal is applied to the rotary heads H1 to H4 located at the winding end position P3 of the video tape 5 when each of the rotary heads H1 to H4 is rotated to the winding start position P2 of the video tape 5. Switching is performed by a drive signal switching circuit (not shown). Each rotary head H1 to H4 covers cylinder 1, where t is one field of the video signal, that is, about 16
．． 6 milliseconds, and the control motor rotates the rotating head H1 via the head bars 2, 2' corresponding to this set time.
~H4 is driven and controlled. Therefore, in the two-rotating head system, the rotation speed is 30 revolutions per second, and for example, when there are four rotary heads, the rotation speed is 45 revolutions per second.

Therefore, in this rotary n-head system having such a configuration, in this embodiment, the four-rotary head system, the winding of the video tape 5 with respect to the cylinder 1 = πr. Therefore, it becomes equal to the winding πr of the video tape 5. Also,
This is equal to 16.6 milliseconds, which is the time it takes for the rotary heads to make a half revolution in the rotary heads H1 to H4 mode. Therefore, the recording tracks TR1', TR2', . . . shown in FIG. 6 recorded on the videotape 5 by the method of this embodiment are as follows.
Recording track TR shown in FIG. 3 using the rotating two-head system
1, TR2, and so on.

In this way, according to this embodiment, compatibility is ensured between a videotape on which the radius r' of cylinder 1 is recorded and a videotape based on the rotary two-head system. Note that in the embodiments described above, rotating heads fixed to the same head bar have the same azimuth, and rotating heads fixed to the adjacent head bar have different azimuths. Further, each of the rotary heads H1 to H4 can be similarly applied to the case of reproducing a video signal.

As described above, according to the present invention, there are at least four rotating heads, each rotating head is arranged at equal intervals along the slit of the cylinder, and the video tape (n-
1) Set the switching timing of the drive signal given to each rotary head when each rotary head rotates to the video tape winding start position, and set the timing of switching the drive signal given to each rotary head for (n-1)/n rounds of each rotary head. Since the rotation time for n rounds is set to 1 field of the video signal (where r is the rotation radius of the rotating head in the rotating 2-head system), the length of the videotape winding and the rotation time of the rotating head are set to 1 field of the video signal. The time it takes to travel between windings of videotape to record the data can be made equal to that of the rotating two-head system. Therefore, there is compatibility between video tapes recorded using the method according to the present invention and video tapes recorded using the rotating two-head method. Moreover, in the present invention, the rotation radius of the rotary head is 2 rotations.
Since the size is n/2 (n-1) of that of the head type, the cylinder can be made smaller and the VTR can be made smaller.

[Brief explanation of drawings]

Figures 1 to 3 show conventional examples, with Figure 1 being a plan view and Figure 2 being a plan view.
The figure is a side view, FIG. 3 is a schematic diagram of a video tape on which a video signal is recorded by a conventional method, FIGS. 4 to 6 show an embodiment of the present invention, FIG. 4 is a plan view, and FIG. The figure is a side view,
FIG. 6 is a schematic diagram of a videotape on which a video signal is recorded according to the embodiment method. 1...Cylinder, 2,2'...Head bar, 3...
・Slit, 4, 4...Tape guide, 5...Video tape, H1-H4...Rotating head

Claims (1)

[Claims] (1) n rotating heads for recording and reproducing video signals (
However, n is an even number of 4 or more), and each rotary head is arranged at equal intervals along the slit of the cylinder, and the video tape is wound around the cylinder for (n-1)/n rounds and applied to each rotary head. The switching timing of the drive signal is set when each rotary head rotates to the video tape winding start position, and the rotation time of each rotary head for (n-1)/n revolutions is set for one field of the video signal. A rotary head system for a VTR characterized in that the rotation radius of the rotary head in the rotary head system is set to .