JP2574350B2 - Rotating head type magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head type magnetic recording and reproducing apparatus for recording and reproducing signals on a magnetic tape using a rotary head, such as a video tape recorder.

2. Description of the Related Art In recent years, video tape recorders (hereinafter referred to as VTRs) have become increasingly smaller and lighter, with higher image quality, higher sound quality, and more functions. The number of rotating heads has increased significantly due to the addition of rotating audio (hereinafter referred to as FM audio) heads for higher quality and higher sound quality, the addition of special playback heads and multi-functional rotating erase heads, etc. I have. Accordingly, even in VTRs of the same format, the number of rotary heads varies depending on the model.

For this reason, when the compatible heads with different numbers of rotating heads are compatible with each other, the tapes vibrate when the rotating heads move into and out of the tape. Had deteriorated.

Problems to be Solved by the Invention One of the major problems caused by the difference in the number of rotating heads between models is that tape rotation that occurs when the rotating head enters and leaves the tape during compatible playback between VTRs with different numbers of rotating heads. The causes of the local distortion or color unevenness of the reproduction screen due to the influence and the deterioration of the reproduction image quality are as follows. Vibration occurs in the magnetic tape due to the impact of the rotating head, which is mounted on the magnetic tape wound around the rotating drum and protrudes by a predetermined amount at a high speed, enters and leaves at high speed, and the vibration of the magnetic tape occurs as it is. A change in the relative speed between the rotating head and the magnetic tape causes a change in the time axis of the recording signal and the reproduction signal.

At this time, the magnetic tape is moved to the tape drive (capstan,
Pinch roller (not shown) and supply reel (not shown)
, The vibration due to the impact when the rotary head enters or leaves the head is instantaneously transmitted to the entire magnetic tape, and the entire string is vibrated. (If there is a fixed post with large friction or a rotating roller with large inertia between the tape drive and the supply reel, the location may be a knot of the string, but the magnetic tape on the rotating drum is The same vibration occurs at any place (the vibration level is slightly different depending on the place).)

If the timing and the amount of relative speed change between the magnetic tape and the rotary head during recording and playback are exactly the same, there is no change in the playback signal and there is no effect on the playback image quality. If the numbers are different, or if the timing of the rotating head entering and leaving the magnetic tape during recording and playback is out of sync, the playback signal will fluctuate on the time axis, causing the playback screen to bend, The phase relationship between the subcarrier and the reproduced video signal is disturbed, and hue variation (color shift) occurs. In view of the above-mentioned problems, the present invention reduces the vibration of the magnetic tape that occurs when the rotating head enters and separates from the magnetic tape. Another object of the present invention is to provide a configuration of a rotary head type magnetic recording / reproducing apparatus capable of obtaining a good reproduction image quality with almost no color shift.

Means for Solving the Problems The winding of the magnetic tape around a rotating drum having a plurality of rotating heads is performed by moving the rotating head into and out of the magnetic tape with respect to the rotation angle of the rotating head for forming one field screen. This is a rotating head type magnetic recording / reproducing apparatus wound with an overlap of an angle corresponding to a tape length of about 0.5 times a vibration wavelength of a magnetic tape vibration generated by a shock at the time.

According to the above-described means, the vibration of the magnetic tape caused by the impact when the rotary head enters the magnetic tape and the vibration of the magnetic tape generated when the rotary head separates are mutually canceled, and the overall magnetic tape Vibration is reduced.

Embodiment An embodiment of the present invention will be described with reference to FIGS. A pair of rotating video heads on which a magnetic tape 1 is wound
A rotating drum 4 having 2a, 2b and a pair of rotating audio heads 3a, 3b rotates at 1800 rpm in the direction of arrow A to form a one-field screen between 0 ° and 180 ° in FIG. Numeral 1 is wound on a rotating drum with an overlap of aI and aO. At this time, each rotary head 2a, 2b, 3
The vibrations of the magnetic tape 1 caused by the impact of the a and 3b into the magnetic tape 1 at the projecting portion B are represented by I2a, I2b and I3 shown in FIG.
a, I3b and continuously IT, and the vibration of the magnetic tape 1 generated by the impact at the detached portion C from the magnetic tape 1 respectively becomes O2a, O2b, O3a, O3b shown in FIG. Becomes OT. The wavelength of the magnetic tape at this time is λ,
Since the overlap a (aI + aO) of the magnetic tape 1 is set to an amount corresponding to 0.5 times the vibration wavelength λ, the intruding portion B
As shown in FIG. 4, there is a phase shift of 0.5.times..lambda. Therefore, the minus component of the magnetic tape vibration IT due to the intruding portion B and the plus component of the magnetic tape vibration OT due to the detaching portion C are canceled out, and the overall magnetic tape vibration waveform is shown in FIG.
Thus, the vibration of the magnetic tape can be substantially reduced. In the experiment, the magnetic tape vibration caused by the intruding portion B tends to have a large negative component and the magnetic tape vibration caused by the detaching portion C tends to have a large positive component. With the above configuration and operation, there is almost no change in the relative speed between the rotating head and the magnetic tape due to the vibration of the magnetic tape. Absent. Therefore, a stable and good reproduction image quality can be always obtained under any reproduction conditions.

According to the rotary head type magnetic recording / reproducing apparatus of the present embodiment,
The relative speed between the rotary head 1 and the magnetic tape 3 caused by the jump of the magnetic tape 3 hardly changes, and the reproduction screen has a bend or a color shift on the compatible playback between VTRs having different numbers of rotary heads. Not at all. Therefore, a stable and good reproduction image quality can be always obtained under any reproduction conditions.

According to the rotary head type magnetic recording / reproducing apparatus of the present invention, since the magnetic tape vibration generated when the rotary head enters and leaves the magnetic tape can be greatly reduced, the relative position between the rotary head and the magnetic tape can be reduced. Little change in speed occurs,
Even during compatible playback between VTRs with different numbers of rotating heads, no bends or color shifts occur on the playback screen. Therefore, a stable and good reproduction image quality can be always obtained under any reproduction conditions.

[Brief description of the drawings]

FIG. 1 is a plan view of a main part of an embodiment of the present invention, FIG. 2 is a waveform diagram of a magnetic tape vibration when the rotary head enters, FIG. 3 is a waveform diagram of a magnetic tape when the rotary head separates, and FIG. It is a comprehensive magnetic tape vibration waveform diagram. 1 ... magnetic tape, 2 ... rotating video head, 3 ... rotating audio head, 4 ... rotating drum, aI, aO ... overlapping part.

Claims (1)

(57) [Claims] 1. The method according to claim 1, wherein the magnetic tape is wound around a rotating drum having a plurality of rotating heads when the rotating head enters and separates from the magnetic tape with respect to a rotation angle for forming one field screen of the rotating head. A rotary head type magnetic recording / reproducing apparatus, which is wound with an overlap at an angle corresponding to a tape length of about 0.5 times the vibration wavelength of the magnetic tape vibration generated by the magnetic head.