JPH0263242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus (hereinafter referred to as
This invention relates to a method particularly suitable for improving the playback quality of a VTR (abbreviated as VTR).

In conventional helical scan VTRs, video and audio signals are recorded on magnetic tape. After processing the input video and audio signals, they are sent to different locations on the magnetic tape via dedicated heads. (track).

That is, a video signal is recorded in a video head on a video track provided diagonally with respect to the longitudinal direction of the magnetic tape, and an audio signal is recorded on an audio track provided along the longitudinal direction of the magnetic tape.

Incidentally, in recent years, with improvements in magnetic heads and magnetic tapes, the magnetic recording and reproducing characteristics of video signals have improved. For this reason, the amount of tape required to obtain a desired S/N ratio is small, and recording density has been improved by slowing down the tape speed. However, in this case, since the audio head is fixed for the audio signal, the band of the reproduced sound output becomes narrower as the tape speed becomes slower, and the S/N ratio also deteriorates.

In response to this, it has been proposed to frequency modulate the audio signal and multiplex the FM audio signal 18 in the band between the FM modulated luminance signal 16 and the low frequency converted chroma signal 17, as shown in FIG. It has been considered. In this case, the relative speed between the tape and the head is greatly increased, and the sound quality is significantly improved. However, if the FM luminance signal 16 and low-frequency conversion chroma signal 17 are set in the same band as before, the band between the two signals is narrow, so both signals crosstalk with the FM audio signal 18, resulting in poor playback image quality or playback sound quality. Causes deterioration. That is, there is a drawback in that it is difficult to improve the reproduced sound quality while maintaining compatibility with the conventional method.

An object of the present invention is to eliminate the drawbacks of the prior art described above, and to significantly improve the playback image quality while maintaining compatibility with the prior art even when recording video signals at high density.
Our goal is to provide VCRs.

In order to achieve the above object, the present invention first records an audio modulated signal that is FM modulated in accordance with an audio signal on a recording track for a video signal, and then records a luminance modulated signal that is FM modulated in accordance with a luminance signal. The chroma low-frequency signal that has been low-frequency converted is overwritten and recorded on the same track on which the audio modulation signal is recorded. Note that the audio modulation signal is set in a band between the luminance modulation signal and the chroma low frequency signal. In addition, rotary heads for video signals are provided for each of the low speed mode and the standard speed mode, in which the tape running speed has become slower than the conventional standard speed mode in response to high-density recording, and also for the audio modulation signal. A rotary head is provided, and the arrangement of the video rotary head and the audio rotary head for each tape speed mode and the height of the mounting surface between these heads have a predetermined relationship. In this way, the video signal can be recorded to the maximum possible track pitch, and the audio modulation signal can be overwritten and recorded within the video recording track.

The present invention will be explained below by way of an example. Second
FIG. 3 shows the arrangement of the head on the cylinder according to the present invention. In FIG. 2, two pairs of image heads 20 and 21 and 22 and 23 are arranged on a cylinder 19 with an interval of approximately 180 degrees and have different azimuth angles.
1 is for standard speed mode (speed v ₁ ), 22 and 2
3 is installed for low speed mode (speed v ₂ ). Also on the cylinder 19 are a pair of audio heads 24 and 25, which are similarly spaced apart by approximately 180 degrees and have different azimuth angles, and are separated from the video heads 20 and 21 by an angle α ₁ and It is located at an angle α ₂ from the image heads 22 and 23. Note that the direction of rotation of the cylinder 19 is indicated by an arrow 26. Also, the azimuth angle between the gap facing surface of each head and the plane perpendicular to the head rotation direction is, for example, +θ for the video heads 20 and 22, -θ for the video heads 21 and 23, and -θ for the audio heads 24 and 25, respectively. + and - angles are provided to reduce crosstalk between audio and video signals that occur between adjacent and same tracks due to azimuth loss.

Also, the video heads 20 to 23 and the audio head 24,
There is a step in the height of the mounting surface of 25 as shown in Figure 3.
Td ₁ Td ₂ is provided. As shown in FIG. 5, the track width of the video head is set to 2 for the standard speed mode so that the recording track width can be made as wide as possible according to each tape speed and the S/N ratio can be improved.
0.21 is wider.

With the heads arranged as described above, video heads 20 and 21 are selected for standard speed mode, and video heads 22 and 23 are selected for low speed mode and are used in conjunction with audio heads 24 and 25. And the angles α ₁ , α ₂ and the step shown in Figures 2 and 3
By setting Td ₁ and Td ₂ in the relationship described below depending on the tape running speed, the audio modulation signal is recorded first, and then the video modulation signal is overwritten in good condition in both modes. The audio modulation signal is recorded deep into the magnetic layer of the magnetic tape, and then a brightness modulation signal with a higher frequency than the audio modulation signal is recorded while erasing the audio modulation signal on the surface of the magnetic layer.

The following will explain the case of an NTSC VHS system VTR. With the improvement in recording density, VTRs of the above type have a 1/3 speed mode, which is three times slower than the standard speed mode, for the tape running speed, thereby realizing high density recording. In this case, the video recording track pitch T _p is as follows: Standard speed mode: T _p1 60 μm; 1/3 speed mode: T _p2 20 μm.

First, let's talk about the 1/3 speed mode. In this case, the audio heads 24, 25 and the video head 2
If the track widths T _s and T _v2 of No. 2 and 23 are set to the above-mentioned track pitch T _p2 =20 μm or more, the audio and video modulated signals are recorded to fill the track pitch, and the highest density recording can be achieved. By the way, after the audio heads 24 and 25, there is a video head 2.
2 and 23 trace the recording track, so if there is no step Td, the left end position Q ₁ of the recording start of the video head will be determined according to the delayed angle α ₂ as shown in FIG.
is shifted from the left end position _Q2 of the audio head where recording started, and the left video track that was recorded earlier is erased by the audio head, and the audio signal is not overwritten or erased by the video head in this area, and the audio signal is also on the surface. The problem arises that . This deviation is expressed as α ₂ /180°×T _p2 . Therefore, by adding the same height difference T _d2 to the mounting heights of the audio heads 24, 25 and the video heads 22, 23 as shown in FIG. You will be able to record. That is, if T _d2 = α ₂ ° / 180° × T _p2 (1) is approximately satisfied, high-density recording of video and audio signals can be achieved in low-speed mode.

On the other hand, in the case of standard speed mode, the audio head 24,
25 and the track width Ts of the video heads 20 and 21,
If Tv ₁ is set to the track pitch T _p1 =60 μm or more, the audio and video modulated signals are recorded to the fullest extent of the track pitch. Also, in this case, if there is no step, the deviation in the left end position of the recording start between the audio head and the video head will be α ₁ °/180° Approximately T _p1 occurs, and the previous video track is erased. Therefore, in this case, if T _d1 =α ₁ °/180°×T _p1 (2) is approximately satisfied, the above-mentioned deviation can be eliminated as shown in FIG.

In other words, by arranging the heads such that equations (1) and (2) are satisfied at the same time, video and audio can be recorded at full pitch on the same track in both standard speed and 1/3 speed modes, achieving the highest recording density. .

In the above example, 1/3 speed was used as the low speed mode, but even if the tape running speed changes,
It is clear that the same effect can be obtained at any speed, just by changing the values of T _p1 and T _p2 .

In addition, in the above example, we explained the case where there is one low speed mode and one low speed mode for a total of two modes, but when there are three or more modes (n mode), T _do = αn゜ / 180゜ × T _po …If (3) is satisfied, the same effect can be obtained. Please note that T _do
αn and T _po are the step difference, head arrangement angle, and track pitch, respectively, in the n mode.

By the way, in Figures 2, 3, 5, and 7, as specific numerical examples, α ₁ = 60°, α ₂ =
90°, T _d1 =20 μm, and T _d2 =10 μm, which satisfy equations (1) and (2). The track width of the head is Tv ₁ ≧60 μm, Tv ₂ ≧20 μm, Ts ≧60 μm,
This enables the highest density recording. However, in consideration of crosstalk from adjacent tracks during playback, it is better to make the track width of the head as close to the track pitch as possible. If we focus on the reduction of crosstalk from adjacent speakers in low-speed voice mode (there is no azimuth effect in this case) and allow S/N degradation in standard-speed voice mode, Tv ₁ ≒ 60 μm, Tv ₂
The most appropriate values are approximately 20 μm and 20 (Tp ₂ )≦Ts≦40 μm (2Tp ₂ ). In this case, the recording track patterns are as shown in Fig. 8 in 1/3 speed mode and standard speed mode, respectively.
The result will be as shown in Figure 9 (illustrated with Ts = 30 μm).

Another specific embodiment of the present invention is shown in FIG.
It is shown in FIG. In this case, the step Td ₁ = Td ₂ = 10μ
m, only the audio head has a step. α ₁ = 30° α ₂ =
90°, satisfying equations (1) and (2). The head track width is the same as in the above case. For example, if Tv ₁ =60 μm, Tv ₂ =20 μm, and Ts = 30 μm, the recording track pattern will be the same as in FIGS. 8 and 9.

On the other hand, if there is no step difference between each image head, that is, T _d1 = T _d2 , it is sufficient to satisfy α ₁ /α ₂ = T _p2 /T _p1 from equations (1) and (2). I understand.

A specific example of this case is shown in FIGS. 12 and 13.
As shown in the figure. This is a case where the height difference between each image head is made equal. If the head track width conditions are the same as in the above example, the recording track patterns will be as shown in FIGS. 8 and 9.

By the way, in the above example, it is possible to record as much as possible between the track pitches and achieve a significant improvement in sound and image quality, but it is possible to achieve a significant improvement in sound and image quality, but there may be tracking deviations and differences in Td during playback.
Deterioration occurs due to mass production variations in angle α.

That is, if the forward displacement αn°/180°×T _po changes, the audio head may partially trace the left video track and erase the video modulation signal.
To deal with this, the level difference for the above-mentioned deviation may be made slightly larger. That is, T _do ≧αn゜/180゜×T _po . On the other hand, if it can be fixed almost at a certain step, then the track pitch T _po will be almost constant, so it is obvious that the angle α should be made smaller.
In this case, if it is set to 27 as shown in Figs. 14 and 15, the recording track pattern will be as shown in Fig. 14 (in 1/3 speed mode) and Fig. 15 (in standard speed mode),
Particularly in the standard speed mode, there is also the effect that interference from audio to video due to tracking deviation does not vary greatly.

In the above description, the azimuth angles of the audio heads 24 and 25 are set to + and -, respectively, but it is clear that even if the azimuth angles are reversed, the azimuth effect can be obtained and the effects of the present invention can be similarly obtained.

Of course, the same applies to PAL system VTRs and Beta system home VTRs other than this cited example.

As explained above, according to the present invention, the best high-density recording can be achieved even at tape running speeds other than the standard speed, and good reproduction sound and image quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the operation of a conventional VTR, FIGS. 2 and 3 are diagrams showing an embodiment of the head arrangement according to the present invention, and FIGS.
FIG. 5 is a recording track pattern diagram explaining an embodiment of the present invention, FIGS. 10 and 11 are diagrams showing another embodiment of the present invention, and FIGS. 12 and 13 are diagrams showing still another embodiment of the present invention. It is a figure showing one example. 19...Cylinder, 20-23...Video head, 24, 25...Audio head, 26...Head traveling direction.

Claims (1)

[Scope of Claims] 1. In a helical scan type magnetic recording and reproducing device, first and second video heads and first and second audio heads are installed on a rotating body, and the first and second video heads are installed on a rotating body. The head and the first and second audio heads are each arranged at substantially symmetrical positions with respect to the rotation axis, and the gap facing surfaces of each head are tilted in different directions with respect to a plane perpendicular to the direction in which the head travels. , and a step Td is provided between the first and second audio heads and the first and second video heads, and a straight line connecting the first and second audio heads and the first and second video heads are provided. The angle between the image head and the connecting straight line is α [deg], and the track pitch is
When Tp, the heads are arranged so as to have the relationship Td≧α[deg]/180[deg]×Tp, and the first and second audio heads are placed closer to the first and second video heads. A magnetic recording/reproducing device characterized by performing overwriting recording in advance. 2. In a helical scan type magnetic recording/reproducing device, first and second video heads for a standard tape running speed, third and fourth video heads for a tape running speed different from the standard speed, and a third video head for a tape running speed different from the standard speed are provided. 1. 2nd
and an audio head are installed on a rotating body, and the first and second video heads, the third and fourth video heads, and the first and second audio heads are each set approximately relative to the rotation axis. arranged in symmetrical positions, and the faces facing the gap of each head are inclined in different directions with respect to a vertical plane in the direction of travel of the heads,
Further, a step Td ₁ is provided between the first and second audio heads and the first and second video heads, and the first and second audio heads and the third and fourth video heads are installed.
A step Td ₂ is provided in the mounting with the video head, and the angle between the straight line connecting the first and second audio heads and the straight line connecting the first and second video heads is α ₁ [deg]. , the angle formed by the straight line connecting the first and second audio heads and the straight line connecting the third and fourth video heads is α ₂ [deg], and the track pitch of the standard speed and the speed different from the standard speed are respectively When Tp ₁ and Tp ₂ , set each head so that the relationship is Tp ₁ ≧ α ₁ [deg] / 180 [deg] × Tp ₁ Tp ₂ ≧ α ₂ [deg] / 180 [deg] × Tp ₂ . 1. A magnetic recording and reproducing apparatus characterized in that the first and second audio heads are placed in advance of the first, second, third and fourth video heads for overwriting recording. 3 Determine the track width of the first and second audio heads.
3. The magnetic recording and reproducing apparatus according to claim 2, wherein each of the heads is arranged so as to satisfy the relationship Tp ₂ ≦Ts≦2×Tp ₂ , where Ts is Ts.