JPS6329308A - Magnetic head - Google Patents

Abstract

PURPOSE:To improve S/N and the color picture quality of a reproduced picture by selecting the gap width of a magnetic head so as to satisfy specified relations relative to the recording wavelength of a low frequency conversion carrier chrominance signals and the recording wavelength of a luminance signal to be frequency-modulated. CONSTITUTION:A magnetic head selects a gap width (g) to the value to satisfy both inequalitis lambdac/g<=42 and lambdaw/g>=2 to a recording wavelength lambdac of low frequency conversion carrier chrominance signals and the recording wavelength lambdaw of a luminance signal to be frequency-modulated in a white peak clip level. Both inequalities are obtained by an experiment, etc., the gap width of a magnetic head is selected to the value to satisfy both inequalities and in both bands of the low frequency conversion carrier chrominance signals and an FM luminance signal, a recording loss, a magnetic flux reduction at the time of reproduction and a gap loss are respectively decreased. Thus, a common magnetic head is used and a satisfactory S/N video signal can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic head, and more particularly to a magnetic head for recording and reproducing a low frequency converted carrier chrominance signal and a frequency modulated luminance signal on a magnetic recording medium.

In conventional VTRs, a magnetic head is used to record video signals on a magnetic tape and to reproduce the video signals. In this case, the carrier frequency of the frequency-modulated luminance signal (FM luminance signal) is set high in order to make the VTR compact, light, and high-density, or to increase the horizontal resolution and improve the image quality. There are high-definition VTRs with high horizontal resolution. In such a high-quality VTR, assuming that the minimum recording wavelength of a video signal is λmin, the gap width of the magnetic head is set to approximately 1/3 of λmin, for example, in order to obtain a high S/N and maximize the head reproduction output. It was set to .

Here, the frequency spectrum in a conventional VTR is, for example, as shown in FIG.
The carrier frequencies of the sync depth level, white peak level, and white peak clip level of the M luminance signal IIA are 34MHz, 4.4M)-1z, and 5.4Mf(z, respectively.On the other hand, the frequency spectrum in the high-quality V'TR For example, as shown in FIG. 5(B), the low-frequency conversion color n of the low-frequency conversion carrier color signal IB is
1 carrier frequency is 629kHz7, carrier frequency of FMi degree signal ■8 sync chip level, white peak level, and white peak clip level is 5 to IH, respectively.
It is set at 7°7M l-1z and 9MHz.

In a conventional VTR that records and reproduces signals with the frequency spectrum shown in FIG. 6(A) above, the recording wavelength of the low frequency conversion carrier color signal IA is 922 μm, and the recording wavelength of the FM luminance signal Is at the white peak clip level is 11 μl. It is. Therefore, the gap width of the video recording/reproducing head used in conventional VTRs is approximately 1/1 of the minimum recording wavelength of 11 μm.
3 was set at 0.35 μlm to 0.40 μl.

On the other hand, in a high-quality VTR that records and reproduces signals with a frequency spectrum as shown in FIG. The recording wavelength (ie, the minimum recording wavelength) λw of the signal IIe is about 0.64μ. Therefore, as mentioned above, the gap width of the video recording/reproducing head used in high-quality VTRs is approximately 1/3 of λw, which is 0.2 μm1. : Set.

Here, use a high-quality VTR with high holding power (for example, 800Q).
The above-mentioned figure 6 (B
) When recording and reproducing a video signal having a frequency spectrum as shown in FIG.
, 35μ11-0.40μ- and a high-quality head with a gap width of 02μl, the white peak clip level is higher when using the high-quality head. At the carrier frequency of 98H2 of the FM luminance signal, the reproduction output is improved by about 4'' to 19 dB, and the horizontal resolution is also achieved at 400 TV lines or more.

The above high-quality heads can be used in conventional VTRs with low holding force (
For example, even when recording and reproducing a video signal with a frequency spectrum as shown in FIG. 6(A) on a conventional tape (60008 to 7000e), the re-output of the FM luminance signal band does not meet the standards of the conventional VTR. ing.

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

Problems to be Solved by the Invention However, since the above-mentioned high-quality head has a narrow gap width that emphasizes improvement of high-frequency characteristics in order to increase horizontal resolution, it is difficult to use this high-quality head in a conventional VTR. When recording and reproducing video signals on a conventional tape, the narrowing of the gap increases the recording loss in the low frequency region, especially in the low conversion color subcarrier frequency 629k+-IZ, and the magnetic flux efficiency during reproduction increases. There was a problem in that the gear wheel loss would decrease and the gear loss would become large.

In this case, the external output level of the low-pass conversion carrier color signal is approximately -4,B to -5+ compared to when using the conventional head.
f3 decreases, and its S/N also decreases. This trend also appears in high-quality VTR systems that use high-quality heads and high-quality tapes, and high-frequency characteristics such as volatile signal frequency characteristics have been greatly improved, and horizontal W? Zodochi 4
The brightness signal S/N is equivalent to or higher than a conventional VTR system using a conventional head and a conventional tape, but the low frequency conversion color signal 1 carrier frequency is 629k.
There was a problem in that the reproduction output level at Hz decreased by -5 outputs, the S/N ratio also decreased, and the color image quality of the reproduction screen deteriorated.

Therefore, the present invention solves the above problem by selecting the gap width of the magnetic head to a value that allows reproduction output at a required level or higher to be obtained in both bands of the low frequency conversion carrier chrominance signal and the F~1 luminance signal. The purpose of the present invention is to provide a magnetic head with improved characteristics.

Means for Solving the Problems The magnetic head according to the present invention sets its gap width Q to the recording wavelength λc of the low-pass conversion carrier color signal and the recording wavelength λw of the 411 signal for frequency modulation at the white peak clip level. On the other hand, it is constructed by selecting a value that satisfies the Sanno equation of λc/Q≦42.2w/Q≧2.

Effect The above two inequalities have been obtained through experiments, etc., as described later. By selecting the gap width of the magnetic head to a value that satisfies these two inequalities, the low frequency conversion carrier color signal and the FM In both bands of the luminance signal, recording loss, reduction in magnetic flux efficiency during reproduction, and gap loss are reduced.

Embodiment FIGS. 1 and 2 show a plan view and a side view, respectively, of an embodiment of a magnetic head according to the present invention. In both figures, magnetic head 1
are magnetic head half-holes 2a, 2b made of ferrite, which is an oxide-based ferromagnetic material, and glass-based adhesives 3a, 3b, 4.
5 (shown in matte finish in the figure), etc. A gap portion A is formed between the magnetic head half-rests 2a and 2b.

Further, 6.7 and 8 indicate coil winding grooves, respectively.

By the way, the horizontal resolution is generally the white 5 of the FMti degree signal.
It is proportional to the highest available frequency bandwidth from the frequency corresponding to 0% to the upper sideband of the low-pass transform carrier color signal. In this case, as shown in FIG. 3, the level ratio of the synchronization signal part and the video signal part of the composite video signal is 40:100.
Therefore, the conventional VTR as shown in FIG. 6(A)
In the frequency spectrum of , F corresponding to 50% white
The M carrier frequency is as follows. Here, the frequency of the upper sideband of the low-pass conversion carrier color signal IA is 629+500''=1130 (kHz), so
The highest frequency band that can be recorded is 4.04-1.13=2
．． 91 (MHz). Therefore, the horizontal resolution of the conventional VTR is 2.91×80 strings 233 (TV lines), since 1 MHz of the luminance signal corresponds to about 80 TV lines. Similarly, when the horizontal resolution of a high quality VTR with a frequency spectrum as shown in FIG. 6(B) is determined, it is approximately 410 TV lines.

FIG. 4 shows the normalized playback output versus frequency characteristics of an example of the conventional VTR and high-quality VTR. This characteristic diagram assumes that the tape head relative speed is 5.8i/sec,
A magnetic tape with a low holding force (700Qe) is used for conventional VTRs, and a magnetic tape with high holding force (8500Qe) is used for high-quality VTRs.
) was obtained from the results of a VTR recording and reproducing experiment using a magnetic tape. Here, the characteristics LA and Ls shown by solid lines are the characteristics of the magnetic head gear 1 in a high-quality VTR.
? The characteristic curves are shown when the knob width q is 0.20 μl and 0.25 μm, respectively, and the characteristics Lc and Lo shown by broken lines are obtained when the gap width 9 of the magnetic head is 0.
．． The characteristic curve when it is 35 μm and 040LtIIl is shown.

As can be seen from Figure 4, the Yasiri frequency 5 near the white peak level of the FMi degree signal in the conventional VTR
The normalized reproduction output (reproduction sensitivity) at MHz and the reproduction sensitivity at the carrier frequency of 7 MHz at the white peak level of the FM luminance signal in a high-quality VTR are approximately at the same level. In addition, in this case, a high-quality VTR
For example, the frequency deviation from the sync tip level to the white peak level of the FM luminance signal z3 is
Since it is 2 M l-1z, which is twice that of
More than a TV book can be achieved.

However, in high-quality VTRs, the gap width is 0.2 μm.
When using a magnetic head of
In addition to the loss, compared to conventional VTRs, the low frequency conversion color i?
IIw1 sending frequency 629kHz frequency 500k close to H2
In H2, the playback output level decreased by about -4.9 cEm, and the S/Nt)(l) decreased.

By the way, as mentioned above, when setting the gap width of the magnetic head, it should be set to about 1/3 to 1/4 of the minimum recording wavelength λw (that is, set to λw / Q = 3 to 4). However, if the gap width is set as described above, the reproduced output level will decrease in the low frequency conversion carrier color signal band.

Therefore, the present invention provides three values: a recording wavelength λc corresponding to a low-band conversion carrier color signal, a recording wavelength (minimum recording wavelength) λw corresponding to an FM luminance signal at a white peak clip level, and a gap width Q of a magnetic head. This method is characterized by conducting experiments focusing on , and finding a relational expression that minimizes the decrease in the playback output level.

Here, when λc = 9.22 μm and λw = 0.64 μm, and the gap width Q is changed from 0.2 μm to 0.4 μl, the frequencies are 500 kHz, 5 MHz, and 9 MH2.
The table below shows the experimental measurement results of the playback output level.

Conventional VT using a magnetic head with a width of 04 μm, i.e. λc/G = 23.05 and λw10 = 1.61
The playback output at each frequency when recording and playing back a conventional tape with R (i.e., the maximum playback output level of the conventional VTR system) is the standard v < -i, 0ct
3) shows a sequence of displacements from this reference value.

Here, from the above-mentioned FIG. 4 and the above-mentioned table, the gap width is 0.
With a magnetic head of 25 μm, that is, λc/Q = 36.88 and λw/Q = 2.58, even when recording and reproducing conventional tapes with a conventional VTR, it is possible to record and play back a conventional tape with a high-quality VTR.
Even when recording and playing back high-quality tape with TR, the frequency is 5.
The normalized playback output level decreases by approximately -2c at 00kHz2.
B or less, and it is possible to secure a color signal S/N that is sufficient for practical purposes.

On the other hand, when a magnetic head with a gap width of 025 μm is used to record and reproduce a high quality VTRrH high quality tape, the gap width is 020 μm, that is, λc/Q=46
．． Compared to the case of using a magnetic head of 10 and 2w/q=3.22, there is a decrease of about 2J3 in the normalized reproduction output level of frequency 9M)-1z. but,
This can be fully compensated for by the sharpness Q of the head (approximately 4, f
3). In the above case, high-quality type V
The reproduction output level of the TR at a frequency of 7 MHz is also approximately 2 dB lower than the reproduction output level of a conventional VTR at a frequency of 7 MHz. However, in this case, the frequency deviation width of the FM luminance signal of the high-definition VTR is 2M)-1z, which is twice that of the conventional VTR, so as mentioned above, even the high-definition VTR is equivalent to the conventional VTR. The above luminance signal S/N can be ensured.

Next, a relational expression (inequality) for optimizing the gap width of the magnetic head will be explained. To find this relational expression, in the table above, 0 frequency 500k)-1
2. The output decrease in the reproduction output level at frequency 9MH2 is within -2, f3, and
/ CJ = 46.10 and λw / C1 = 3.22, the value when recording and reproducing a high-quality tape (+19.5.E) using a magnetic head is within -3 dB. Two points were required.

In this case, the relational expressions that satisfy the above condition (■) are as follows from the above table: 298≧λw/Q, 41.91≧λc/Q
...(1), and the relational expression that satisfies condition (■) is 322≧λw/Q≧2.38.

46, 10≧λc / Q≧34.15
... becomes ■.

Therefore, the relational expression that satisfies both equations (1) and (2) above is: 293≧λw / CJ≧2.38° 4191≧λc / Q≧34.15 ・
... becomes ■.

In equation (3) above, if we take into account errors in experimental measurement results and changes in tape running speed, equation (3) can be roughly transformed into equation (4).
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2w/g≧2. λc/g≦42...(
4) Next, in Figure 5, the gap width is 0435 μm (Zunawara, λc / Q = 26.3, 2w / Q = 1
．． Using the recording and playback level at each frequency when using the magnetic head a of 84) as a reference value, the gap width is 02.
5μl1l (i.e., λc/Q = 36.88
, λw/g = 2.58) and a gear ship width of 02 μm (i.e., λc/g = 46.1.-2).
2 is a graph comparing the recording and reproducing levels when using a magnetic head C with w/Q = 322).

Here, RA and PA indicate the recording level and rewrite output level when using magnetic head b with a gap width of 0 and 25 μm, respectively, and R8 and Pa indicate a gap width of 0.20 μm, respectively.
Showing the recording level and reproduction output level when using a μm magnetic head C, 1 In this case, the gap width is 025 μl.
The magnetic head b is a head according to the present invention that satisfies the above formula (4), while the magnetic head C having a gap width of 0.20 μm is a conventional head that does not satisfy the formula (4).

From Figure 5, low-pass conversion color subcarrier frequency 629kl-1
In the region below the frequency IMH2, which is the sum of 2, the magnetic head C
The magnetic head b has a recording loss of 12 times more than the magnetic head a, but the magnetic head b according to the present invention has a recording loss of -2.13 times or less. Also, in reproduction, the magnetic head b according to the present invention recovers reproduction loss due to gap loss and reduction in reproduction efficiency to almost the standard value at a frequency of around 1 MHz. On the other hand, in the FM luminance signal band, the reproduction output level of magnetic head C is about 1 cE higher than that of magnetic head B at a frequency of 9 MHz, but this has no practical effect for the above-mentioned reason.

According to the present invention, there is virtually no reduction in the reproduction output sensitivity of the low frequency conversion carrier chrominance signal, and the reproduction output sensitivity of the FM luminance signal with a wide band and high carrier frequency is improved. In addition, the brightness signal S/N is equal to or higher than that of conventional VTRs, and high-quality playback image quality with horizontal resolution of 400TV or higher can be obtained, which is better than conventional VT
Both R and high-quality VTRs that record and reproduce FM luminance signals with high carrier frequencies have features such as being able to record and reproduce 1g video with a good S/N using a common magnetic head.

[Brief explanation of the drawing]

1 and 2 are a plan view and a side view, respectively, showing an embodiment of the magnetic head according to the present invention, FIG. 3 is a diagram for explaining the relationship between the level and frequency of a video signal, and FIG. 4 FIG. 5 is a normalized playback output versus frequency characteristic diagram of an example of a conventional VTR and a high-quality VTR, and FIG. 5 shows the recording level and playback level of a conventional magnetic head and a magnetic head according to the present invention, respectively. , FIGS. 6(A) and (B) are respectively conventional V
FIG. 2 is a frequency spectrum diagram of an example of a TR and a high-quality VTR. 1...Magnetic head, 2a, 2b...Magnetic head half-closed, 3a, 3b, 4.5-...Glass adhesive, 6,7° 8...Coil winding groove, A... gap section. Patent applicant: Victor Company of Japan Co., Ltd. . Saka number iMHz-

Claims (1)

[Scope of Claims] In a magnetic head for recording and reproducing a low-band conversion carrier color signal and a frequency-modulated luminance signal on a magnetic recording medium, the gap width g of the magnetic head is defined as the recording wavelength of the low-band conversion carrier color signal. For λ_c and the recording wavelength λ_w of the frequency modulated luminance signal at the white peak clip level, values are selected and configured to satisfy both the inequalities λ_c/g≦42 and λ_w/g≧2. Features a magnetic head.