JPH0758526B2 - Video signal magnetic recording / reproducing method and video signal magnetic recording / reproducing apparatus - Google Patents

Description

The present invention relates to a video signal magnetic recording / reproducing method and a video signal magnetic recording / reproducing apparatus.

Conventional technology In VTR, a video signal is recorded on a magnetic tape using a magnetic head and is also reproduced. In this case, in order to reduce the size and weight of the VTR and increase the density, or to increase the horizontal resolution to achieve high-quality images, the horizontal resolution of the carrier frequency of the frequency-modulated luminance signal (FM luminance signal) is set high. There is a high-quality VTR. In such a high definition VTR, if the minimum recording wavelength of the video signal is λ _min , the high S / N
In order to obtain the maximum head reproduction output, the gap width of the magnetic head is set to, for example, approximately 1/3 of λ _min .

Here, the frequency spectrum of the conventional VTR is as shown in, for example, FIG.
I _A low-frequency conversion subcarrier frequency is 629kHz, FM luminance signal I
Carrier frequencies of sync tip level, white peak level and white peak clip level of I _A are respectively
These are 3.4MHz, 4.4MHz and 5.4MHz. On the other hand, the frequency spectrum in the high-quality VTR is as shown in FIG. 5 (B), for example, the low-frequency conversion carrier color signal I _{B has} a low-frequency conversion color subcarrier frequency of 629 kHz, and the FM luminance signal II _{B has} a sync chip. The carrier frequencies of the level, white peak level and white peak clip level are set to 5 MHz, 7 MHz and 9 MHz, respectively.

In the conventional VTR that records and reproduces the signal of the frequency spectrum shown in FIG. 6 (A), the low-frequency conversion carrier color signal I _A
The recording wavelength 9.22Myuemu, the recording wavelength of the FM luminance signal I _B at the White peak clip level is 1.1 .mu.m. Therefore,
The gap width of the video recording / reproducing head used in the conventional VTR is 0.35 μm to 0.40 μm, which is approximately 1/3 of the minimum recording wavelength of 1.1 μm.
Was set to.

On the other hand, in the high-quality type VTR for recording and reproducing a signal of a frequency spectrum shown in FIG. 6 (B), the recording wavelength lambda _C of the low frequency converted carrier chrominance signal I _B is about 9.22Myuemu, FM of white peak clipping level The recording wavelength (that is, the minimum recording wavelength) λ _W of the luminance signal II _B is about 0.64 μm. Therefore,
As described above, the gap width of the video recording / reproducing head used for the high-quality VTR is set to 0.2 μm, which is approximately 1/3 of λ _W.

Here, a high-quality VTR has a high coercive force (for example, 800 Oe to 900 O).
When a video signal having a frequency spectrum as shown in FIG. 6 (B) is recorded / reproduced on the high-grade tape of e), the gap width of 0.35 μm to 0.40 μ is used as a magnetic head.
of the conventional FM head with a gap width of 0.2 μm and the high-definition head with a gap width of 0.2 μm are compared, the FM luminance signal carrier at the white peak clip level is higher when the high-quality head is used. 4 dB at 9 MHz
Playback output improved by ~ 19 dB, and horizontal resolution is 400 TV
More than a book will be realized.

Even when the above high-quality type head is used for a conventional VTR to record and reproduce a video signal of a frequency spectrum as shown in FIG. 6 (A) on a conventional tape having a low coercive force (for example, 600 Oe to 700 Oe), The playback output in the FM luminance signal band meets the standards for conventional VTRs.

Therefore, even if a high-quality head having a gap width of 0.2 μm is used in the FM luminance signal band between the conventional VTR and the high-quality VTR, they are compatible with each other.

However, since the high-quality head has a narrow gap width that emphasizes the improvement of high-frequency characteristics in order to enhance the horizontal resolution, this high-quality head is used in a conventional VTR. When a video signal is recorded and reproduced on a conventional tape, the recording gap becomes large due to the narrow gap, especially in the low frequency conversion color subcarrier frequency of 629 kHz, and the magnetic flux efficiency during reproduction decreases. There was a point.

In this case, the reproduction output level of the low-frequency conversion carrier color signal is reduced by about -4 dB to -5 dB and the S / N thereof is also reduced as compared with the case of using the conventional head. This tendency also appears in high-quality VTR systems that use high-quality heads and high-quality tapes, and high frequency characteristics such as luminance signal frequency characteristics are greatly improved, and horizontal resolution is 400 TV lines or more. The S / N is equal to or higher than that of the conventional VTR system using the conventional head and the conventional tape, but the reproduction output level at the low-frequency conversion color subcarrier frequency of 629 kHz decreases by -5 dB, and the S / N also decreases. However, there is a problem that the color quality of the reproduction screen is deteriorated.

Therefore, according to the present invention, the gap width of the magnetic head is selected to a value that can provide a reproduction output higher than a required level in both the low-frequency conversion carrier color signal and the FM luminance signal band, and by using a high-quality magnetic tape. An object of the present invention is to provide a video signal magnetic recording / reproducing method and a video signal magnetic recording / reproducing apparatus which solve the above problems.

Means for Solving the Problems The first invention is a low-frequency conversion carrier color signal having a coercive force of 800 Oe to 900 Oe, a recording wavelength generated from an image signal being λc, and a recording wavelength at a white peak clip level of λw. A video signal magnetic recording / reproducing method for recording / reproducing the video signal using a magnetic head having a gap width of g on a high-quality magnetic tape for recording a frequency-modulated luminance signal. λw / g ≧ 2.4 and about 42 ≧ λc / g ≧ 34 are set, and the low-frequency conversion carrier color signal, the frequency-modulated luminance signal, and the magnetic head are used for the high-quality magnetic tape. The present invention provides a video signal magnetic recording / reproducing method characterized by recording / reproducing.

A second invention is a low-frequency conversion carrier color signal having a coercive force of 800 Oe to 900 Oe, a recording wavelength of which is λc, and a frequency-modulated luminance signal having a recording wavelength of λw at a white peak clip level. A high-quality magnetic tape for recording; and a magnetic head set to satisfy about 2.9 ≧ λw / g ≧ 2.4 and about 42 ≧ λc / g ≧ 34 when the gap width is g, The present invention provides a video signal magnetic recording / reproducing apparatus characterized by recording / reproducing the low-frequency conversion carrier color signal and the frequency-modulated luminance signal on a high-quality magnetic tape by using the magnetic head.

Action Both of the above inequalities are obtained by experiments, etc., as will be described later, and by selecting the gap width of the magnetic head to a value that satisfies both inequalities and using a high-quality magnetic tape, The recording loss, the decrease in magnetic flux efficiency during reproduction, and the gap loss are reduced in both bands of the frequency conversion carrier color signal and the FM luminance signal.

Embodiment FIG. 1 and FIG. 2 respectively show a plan view and a side view of an embodiment of a magnetic head used in the present invention. In both figures, the magnetic head 1 is composed of magnetic head halves 2a and 2b made of ferrite, which is an oxide-based ferromagnetic material, and glass-based adhesives 3a, 3b, 4,5 (shown in satin in the figures), etc. It Magnetic head half 2
A gap portion A is formed in a and 2b. Reference numerals 6, 7 and 8 denote grooves for coil winding.

By the way, generally, the horizontal resolution is proportional to the maximum available frequency bandwidth from the frequency corresponding to 50% of white in the FM luminance signal to the upper side band of the low-frequency conversion carrier color signal. In this case, as shown in FIG. 3, since the ratio of the levels of the sync signal portion and the video signal portion of the composite video signal is 40: 100,
In the frequency spectrum of the conventional VTR as shown in FIG. 6 (A), the FM carrier frequency corresponding to white 50% is Becomes Here, since the frequency of the upper sideband of the low-frequency conversion carrier color signal I _A is 629 + 500 ≈ 1130 (kHz), the maximum recordable frequency band is 4.04-1.13 = 2.91 (MHz). Therefore, the horizontal resolution of the conventional VTR is 2.91 × 80 ≈ 233 (TV lines) because 1 MHz of the luminance signal corresponds to about 80 TV lines. Similarly, the horizontal resolution of the high definition VTR having the frequency spectrum as shown in FIG. 6 (B) is calculated to be about 410 TV lines.

FIG. 4 shows an example of normalized reproduction output vs. frequency characteristic in the conventional VTR and the high-quality VTR. This characteristic diagram shows the case where the relative speed of the tape head is 5.8 m / sec, the conventional VTR uses a low coercive force (700 Oe) magnetic tape, and the high-quality VTR uses a high coercive force (850 Oe) magnetic tape. It was obtained from the VTR recording / playback experiment results. Here, the characteristics L _A and L _B shown by the solid lines are characteristic curves when the gap width g of the magnetic head is 0.20 μm and 0.25 μm in the high-quality VTR, and the characteristics L _C and L _D shown by the broken lines are shown. Is a conventional VTR
At the magnetic head gap width g of 0.35 μm and
The characteristic curve when 0.40 μm is shown.

As can be seen from FIG. 4, the normalized playback output (playback sensitivity) at a carrier frequency of 5 MHz near the white peak level of the FM luminance signal in the conventional VTR and the carrier at the white peak level of the FM luminance signal in the high-quality VTR. The reproduction sensitivity at a frequency of 7 MHz is almost at the same level. In this case, in a high-definition VTR, for example, the frequency deviation from the sync tip level of the FM luminance signal to the white peak level is 2 MHz, which is twice that of the conventional VTR.
/ N improved by about 6 dB, and horizontal resolution is 400 TV as mentioned above.
More than a book is achieved.

However, when a magnetic head with a gap width of 0.2 μm is used in a high-quality VTR, the magnetic flux efficiency during reproduction decreases due to the narrowing of the gap, and the recording loss due to head saturation in the low frequency region due to the high holding power of the tape. In addition, conventional VT
Compared to R, the reproduction output level decreased by about -4.9 dB and the S / N also decreased at a frequency of 500 kHz, which was close to the low-frequency conversion color subcarrier frequency of 629 kHz.

By the way, as described above, when the gap width of the magnetic head is set, it should be set to about 1/3 to 1/4 of the minimum recording wavelength λ _W (that is, set to λ _W / g = 3 to 4). Was common. However, if the gap width is set as described above, the reproduction output level is lowered in the low-frequency conversion carrier color signal band.

Therefore, according to the present invention, the recording wavelength λ _C corresponding to the low-frequency conversion carrier color signal, the recording wavelength (minimum recording wavelength) λ _W corresponding to the FM luminance signal at the white peak clip level, and the gap width g of the magnetic head are 3 Experiment by focusing on three values,
It is characterized in that a relational expression that minimizes the reduction in the reproduction output level is obtained.

Here, λ _C = 9.22 μm, λ _W = 0.64 μm, and the frequency 50 when the gap width g is changed from 0.2 μm to 0.4 μm.
The table below shows the experimental measurement results of the playback output level at 0kHz, 5MHz, and 9MHz.

The playback output level value (dB) in the table above is the gap width 0.4μ.
m, that is, reproduction output at each frequency when recording / reproducing a conventional tape with a conventional VTR using a magnetic head of λ _C /g=23.05 and λ _W /g=1.61 (that is, a conventional VTR system The maximum reproduction output level) is used as a reference value (that is, 0 dB), and the amount of displacement from this reference value is shown.

From FIG. 4 and the table above, the gap width is 0.25.
With a magnetic head of μm, that is, λ _{C /} g = 36.88 and λ _{W /} g = 2.58, even when recording and reproducing a conventional tape with a conventional VTR, and when recording and reproducing a high-quality tape with a high-quality VTR. However, the drop in the standardized playback output level at a frequency of 500 kHz is within about -2 dB, and the color signal S / N can be sufficiently secured without any problem in practical use.

On the other hand, when recording and reproducing a high-quality tape with a high-quality VTR using the magnetic head having the gap width of 0.25 μm, the gap width is 0.20 μm, that is, λ _C /g=46.10 and λ _W / g
= 9MHz compared to using a magnetic head of 3.22
There is a drop of about 2 dB in the standardized playback output level. However, this is a range (about 4 dB) that can be sufficiently compensated by the sharpness Q of the head. Also, in the above case, the playback output level of the high definition VTR at the frequency of 7 MHz is also the same as that of the conventional VTR.
About 2 dB lower than the playback output level at a frequency of 7 MHz. However, in this case, the FM of the high definition VTR
Since the frequency deviation width of the luminance signal is 2 MHz, which is twice that of the conventional VTR, as described above, it is possible to secure the luminance signal S / N equal to or higher than that of the conventional VTR even in the high quality VTR.

Next, a relational expression (inequality) for optimizing the gap width of the magnetic head will be described. In obtaining this relational expression, in the above table, the output decrease of the reproduction output level at the frequency of 500 kHz is within −2 dB, and the output decrease of the reproduction output level at the frequency of 9 MHz is
Gap width 0.2 μm, ie λ _C / g = 46.10 and λ _W / g =
The two conditions were set within −3 dB from the value (+19.5 dB) when recording / reproducing a high-quality tape using the magnetic head of 3.22.

In this case, the relational expression satisfying the above condition is 2.93 ≧ λ _W / g, 41.91 ≧ λ _C / g (1) from the above table, and the relational expression satisfying the condition is 3.22 ≧ λ _W / g ≧ 2.38, 46.10 ≧ λ _C /g≧34.15 (2)

Therefore, the relational expression satisfying both the above equations (1) and (2) is 2.93 ≧ λ _W /g≧2.38, 41,91 ≧ λ _C /g≧34.15 (3).

Considering the error of the experimental measurement result and the change of the tape running speed in the expression (3), the expression (3) is roughly expressed by the expression (4).
Can be rewritten like a formula.

λ _W / g ≧ 2, λ _C / g ≦ 42 (4) Next, FIG. 5 shows a gap width of 0.35 μm (that is, λ _C / g
= 26.3, λ _W /g=1.84), the gap width is 0.25 μm (that is, λ _C /g=36.88, λ _W / g =) using the recording and reproducing levels at each frequency when the magnetic head a is used. 2.
58) magnetic head b and gap width 0.2 μm (ie λ _C
9 is a graph comparing recording and reproducing levels when a magnetic head c of /g=46.1, λ _W /g=3.22) is used.

Here, R _A and P _{A respectively} indicate the recording level and the reproduction output level when the magnetic head b having a gap width of 0.25 μm is used, and R _B and P _{B respectively} indicate the magnetic head c having a gap width of 0.20 μm.
The following shows the recording level and the reproduction output level when is used.
In this case, the magnetic head b having a gap width of 0.25 μm is the head according to the present invention which satisfies the above formula (4).
The magnetic head c having a gap width of 0.20 μm is a conventional head that does not satisfy the expression (4).

As shown in FIG. 5, the magnetic head c has a recording loss of −2 dB or more as compared with the magnetic head a in the region of a frequency of 1 MHz or less including 629 kHz in the low frequency conversion color subcarrier frequency. The head b has a recording loss of −2 dB or less. Also in reproduction, in the magnetic head b used in the present invention, the reproduction loss due to the gap loss and the reduction of the reproduction efficiency is almost restored to the reference value in the vicinity of the frequency of 1 MHz. on the other hand
In the FM luminance signal band, the magnetic head c at a frequency of 9 MHz
The reproducing output level is about 1 dB higher than that of the magnetic head b, but this has no practical effect due to the above reason.

EFFECTS OF THE INVENTION As described above, according to the present invention, there is almost no reduction in reproduction output sensitivity of the low-frequency conversion carrier color signal, and the band is widened, and
The reproduction output sensitivity of FM luminance signal with high carrier frequency can be improved, and the luminance signal S / N is equal to or higher than that of the conventional VTR, and high-quality magnetic tape is reproduced to obtain a horizontal resolution of 40.
It has features such as the ability to obtain high-quality reproduced images of 0 or more lines.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are a plan view and a side view, respectively, showing an embodiment of a magnetic head used in the present invention, and FIG. 3 shows the relationship between the level of a video signal and the frequency. FIG. 4 is an explanatory diagram, FIG. 4 is a normalized reproduction output vs. frequency characteristic diagram of an example of a conventional VTR and a high-quality VTR, and FIG. 5 is a recording level of a conventional magnetic head and a magnetic head according to the present invention. FIGS. 6 (A) and 6 (B) are diagrams showing reproduction levels, respectively, and are frequency spectrum diagrams of an example of a conventional VTR and a high-quality VTR, respectively. 1 ... Magnetic head, 2a, 2b ... Magnetic head half, 3a, 3b,
4,5 …… Glass adhesive, 6,7,8 …… Coil winding groove, A
…… Gap part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Tagami 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan, Ltd.

Claims (2)

[Claims] 1. A low-pass conversion carrier color signal having a coercive force of 800 Oe to 900 Oe, a recording wavelength generated from a video signal being λc, and a recording wavelength at a white peak clip level of λc.
A video signal magnetic recording / reproducing method for recording / reproducing the video signal using a magnetic head having a gap width of g on a high-quality magnetic tape for recording a frequency-modulated luminance signal of w. ≧ λw / g ≧ 2.4 and about 42 ≧ λc / g ≧ 34 are set, and the low-frequency conversion carrier color signal and the frequency-modulated luminance signal are applied to the high-quality magnetic tape by using the magnetic head. A video signal magnetic recording / reproducing method characterized by performing recording / reproducing as described above. 2. A low-pass conversion carrier color signal having a coercive force of 800 Oe to 900 Oe, a recording wavelength generated from an image signal being λc, and a recording wavelength at a white peak clip level is λ.
A high-quality magnetic tape for recording a frequency-modulated luminance signal of w, and when the gap width is g, satisfy about 2.9 ≧ λw / g ≧ 2.4 and about 42 ≧ λc / g ≧ 34. A video signal magnetic recording / reproducing apparatus comprising a set magnetic head, and recording / reproducing the low-frequency conversion carrier color signal and the frequency-modulated luminance signal on the high-quality magnetic tape by using the magnetic head. .