JPH02270104A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To suppress the recording of low frequency distortion while sufficiently holding the reproduced output of a main signal by composing the gap width of a recording magnetic head at <=0.2 of the recording wavelength of a recording signal. CONSTITUTION:When the recording wavelength of the recording signal is lambda, a magnetic gap width (g) of a recording magnetic head is set at g<=0.2lambda. When the above formula is applied to the FM audio head of a VTR in a VHS type, since an FM carrier center frequency for audio signal is 1.5MHz, and a relative speed is 5.8m/s, an inequation g<=0.77mum is obtained. In a practical case, since a head life is shortened when a gap depth Gd is too small, Gd cannot be made too small. Consequently (g) cannot be made too small. The effective gap width is approximately 0.7mum. Thus a magnetic recording/reproducing device which can suppress the disturbing components against the main signal can be obtained while the reproduced output of the main signal is being sufficiently held.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a VH3 system high-fidelity VTR that records video signals and audio signals in a superimposed manner on the same location on a magnetic tape.
The present invention relates to magnetic recording and reproducing devices such as the above.

[Prior art] Figure 8 is from the Journal of the Society of Television Engineers, Vol. 37, No. 12 (198
3) is a schematic perspective view of the main parts of a conventional VH3 system VTR disclosed in 3), and FIG. 9 is a side view thereof. In the figure, (31) is a magnetic head for recording FM video signals (hereinafter referred to as video head), (32) is a magnetic head for recording FM audio signals (hereinafter referred to as audio head), (3
3) is a magnetic tape, and this magnetic tape (33) consists of a base film (34) and a magnetic layer (35).

(301) is the magnetic layer (35) of the magnetic tape (33)
A video signal recording layer (3G2) is recorded on the surface layer of the magnetic tape (33) via the video head (31).
) in the deep part of the magnetic layer (35) of the audio head (
32).

Fig. 10 is a graph showing the spectrum of the recording signal, in which (a) is the video signal spectrum from the video head (31), (41) is the low frequency conversion color signal with a center frequency of 829 KHz, and (42) is the Carrier frequency is 3.4'
~4.4 MHz FM luminance signal. Also, the first
Figure 0 (b) is the audio signal spectrum from the audio head (32), where (51) and (52) are 1.3 M
This is an FM audio signal assigned to two channel frequencies of Hz and 1.7 MHz.

Next, the operation of the above configuration will be explained.

Magnetic tape (33) in the direction of the arrow in Figures 8 and 9.
By running the audio head (32
) to form a recording layer (302), an FM audio signal is recorded in the deep layer of the magnetic layer (35) of the magnetic tape (33), and from above the magnetic layer (302) is recorded via a video head (31). A recording layer (301) is formed by recording an FM video signal in a superimposed manner on the surface layer (35).

Furthermore, by giving the video head (31) and the audio head (32) different azimuth angles during playback, it is difficult to pick up each other's signals, and as is clear from FIG. 10, the spectrum (a) of the video signal The spectrum (b,) of the audio signal is placed in the low power band of , so that reproduction with less interference between signals is performed.

By the way, in the above configuration, the gap length (g) of the audio head (32) is determined as follows, when the recording wavelength of the recording signal is (λ).

When g=on, the playback output becomes 0 due to gap loss, and when g>on, no playback output is obtained at all.
On the other hand, if the gap length (8) is made too small, the magnetic field from the gap becomes too strong, and the efficiency particularly in the long wavelength region decreases.

From the above, in conventional magnetic recording and reproducing devices,
Journal of the Television Society Vol. 35, No. 2 (1981) No. 6
As shown on page 6, the length of the above gap (
When the shortest recording wavelength of g) is (λin), g = 0.255λin ~ 0.5λin ・・
・・・・・・・・・・・・■ was set. therefore,
In the VH3 system VTR, λwin = (relative speed)/(maximum frequency) = 5.
8 (m/s) / 1.7 (MHz) = 3.4 ru ■ Therefore, by substituting this into the above equation 0, g = 0
．． 25X 3.4~0.5X 3.4=0.85~1
．． 7. It was composed of ・・・・・・・・・・・・■.

FIG. 11 is a graph showing the recording spectrum of an FM audio signal by a VH3 system VTR equipped with an audio head (32) having the gap length (g) as described above. In the same figure, (51) has a frequency of 1.3 MHz
The first FM audio signal carrier, (52) has a frequency of 1
．． 7 MHz second FM audio signal carrier, (53)
, (54), and (55) are distortions of the FM audio signal carrier, which are mixed and recorded in the low frequency conversion color signal (41) recorded by the video head (31).

Here, the frequency of the first FM audio signal carrier (51) is fcl, and the frequency of the second FM audio signal carrier (52) is
+7) If the frequency is fc2, the above type (53), (
54).

(55) frequency fc3. fc4, fc5 are f
c3= fc2- fcl= 400 KHzfc4
= fcl -2(fc2-fcl) = 500
KHzfc5=fc2-2(fc2-fcl)=
It becomes 900 KHz.

[Problems to be Solved by the Invention] Since the conventional magnetic recording and reproducing device is configured as described above, when reproducing the main signal from the surface layer of the magnetic tape, the main signal is subject to interference such as low frequency distortion. There was a problem that components were mixed in and appeared as beats in the reproduced image.

Further, as a countermeasure, it may be possible to set the recording current of the FM signal carrier to a small value, but in this case, there is a problem that the reproduction output becomes insufficient and the S/N ratio deteriorates.

This invention was made in order to solve the above-mentioned problems, and provides a magnetic recording and reproducing device that suppresses the mixing of interfering components into the main signal while maintaining a sufficient reproduction output of the main signal. The purpose is to provide

[Means for Solving the Problems] The magnetic recording/reproducing device according to the present invention has a magnetic recording head with a magnetic gap length (g) such that when the recording wavelength of a recording signal is (in), g≦0. .It is characterized by being composed of two people.

[Function] According to the present invention, by configuring the magnetic gap length (g) to be 0.2 times or less the recording wavelength (λ) of the recording signal, recording in the low frequency region is weakened and distortion components are reduced. Interference with playback output due to contamination can be reduced.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

FIGS. 1 and 2 show a VH3 according to an embodiment of the present invention.
These are a schematic perspective view and a side view of the main parts of a system VTR. In each of these figures, the difference from the conventional example shown in FIGS. 8 and 9 is the gap length (g) of the audio head (32). ), and when the recording wavelength of the recording signal is (ON), the other configuration is exactly the same as the conventional example shown in FIGS. 8 and 9, except that g≦0.2 people. The same reference numerals are given to the corresponding parts, and detailed explanation thereof will be omitted.

Next, a method for determining the gap length (g) of the audio head (32) will be explained in detail.

FIG. 3 is a graph showing the change in reproduction output (dB) with respect to the recording current I (dB) flowing through the magnetic head, that is, the input/output characteristics. As is clear from the figure, the recording current I (dB) flowing through the magnetic head ), P in the same figure increases.
The maximum output is reached at the point. The recording depth (d) of the magnetic tape at this time is (input/4), where the recording wavelength is (input).
0).

Here, by reducing the length of the head gap, magnetization saturation can be caused and input/output characteristics as shown by the dotted line in FIG. 3 can be obtained. Recording depth at this time (d
s), Journal of the Television Society, Vol. 35, No. 2 (1981
) Based on the Karcist equation published on page 64, we find that, on the center axis of the gap (!-0) where the magnetic field is strongest, the horizontal component of the magnetic field (the depth at which the horizontal component of the magnetic field reaches the coercive force (Hc) of the tape) If y = ds, then (Ha) is the magnetic field inside the gap, and Bs/L O Bs: Saturation magnetic flux density of the herad core material 0: Magnetic permeability of vacuum (permeability inside the gap (almost the same as the magnetic flux), so solving the above equation for (ds) yields,
Looking at this equation (2), since it is unrelated to the recording wavelength, the recording depth is constant regardless of the recording frequency.

On the other hand, if the length of the head gap is sufficiently large, the recording depth (d) will be (in/4) over all frequencies, where in = ma r/f (ma r: relative velocity of the table head, f:
frequency), the recording wavelength (input) is inversely proportional to the frequency (f). Therefore, as shown in Figure 4, the recording depth (ds) of formula (■) is the recording depth d = input/4 at a certain frequency.
There exists a point where d=ds at a longer recording wavelength, that is, at a lower frequency, and it is impossible to record up to input/4.

Therefore, the output in this region deteriorates. This ds=
If the frequency that provides the recording wavelength (input) of input/4 is set as the center frequency (fc) of the FM audio carrier, recording of frequencies lower than the audio carrier frequency can be weakened while the output of the FM audio carrier remains unchanged. Therefore, it is sufficient to find (g) which gives . The above formula is (g
), we get .

Generally, if only the gap length (8) is shortened, the reproduction gap loss will be reduced in a range where magnetic saturation does not occur, and the output will increase, but the inductance will increase.

The relationship between inductance (L) and gap length (g) is expressed by the following equation.

Here, N: Number of windings R So: Head magnetic resistance RC: Herad core magnetic resistance Rg: Gap magnetic resistance The head core magnetic resistance (Rc) is the gap magnetic resistance (
Since it is set sufficiently smaller than Rg), it becomes.

Also, Here, S: cross-sectional area of the gap Le 0: Magnetic permeability of gap T trade: head track width Gd: Gap depth So, becomes.

Since the frequency band transmitted by magnetic recording and reproduction cannot be changed from the standard, the inductance (L) cannot be changed, nor can the track width be changed, so when formula (2) is written in terms of (N), the following is obtained. In other words, changing the gap length (g) will change the inductance (L), but by adjusting the number of turns (N) and gap depth (Gd), the inductance (L) can be kept constant. can be kept.

On the other hand, the gap loss (Lg) is It is expressed as

The reproduction output changes depending on the gap loss (Lg) and the number of windings (N). It also changes slightly depending on the gap depth (Gd), but this is negligible. Therefore, let the conventional gap length be (g'l), the gap loss be (Lgl), and the number of windings be (old), and the gap length of this embodiment be (g2) and the gap loss be (Lg2).
), and the number of windings is (N2), in order to keep the playback output from changing depending on the recording wavelength (input), LglXN1
= Lg2XN2 ・・・・・・・・・・・・■ Only needs to be satisfied. From the 0.0 formula, the following can be obtained. From the ■ formula, the following can be obtained. That is, at the recording wavelength (on), when the gap length changes from (gl) to (g2), the winding is set from (N1) to (N2) so that the output does not change. At that time, in order to keep the inductance (L) unchanged, the gap depth may be changed from (Gdl) to (Gd2) so as to satisfy the above equation 0.

With the above, as shown in FIG. 5, the low frequency recording characteristic of the audio head (32) can be changed from curve A to curve B while maintaining the output at the recording wavelength (input C).

By the way, the relationship between the coercive force (Ha) of the tape and the saturation magnetic flux density (Bs) of the R head is as follows: Bs [G] ≧5Hc [5el] is the condition for a head that can sufficiently record on the tape. /Bs [When finding the maximum value of Oe/Gl, 115 = 0.25 a Hc/
Bs≦0.25 [Oe/Gl has a unit system of Cg 51.
When converting from system to MKSA system, Bs [T] = f3s[G] x 10Ha
[A/ml = Hc [Oel X 79.8, He/Bg≦199,000 [A/m, T].

Calculating the range of (g) from formula ■, including river 0=4π×lO, g≦0.2 people ・・・・・・・・・・・・・・・・・・
・Becomes [phase].

When the [phase] formula is applied to the FM audio head of a VH3 system VTR, the FM audio carrier center frequency is 1.5 M.
Hz, and the relative velocity is 5.8 mis, so g≦0
．． 7? In reality, if the gap depth (Gd) is made too shallow, the life of the head will be shortened, so (Gd) cannot be made too small. Therefore, as can be seen from equation 0, (g) The effective gap length that cannot be made too small is 0. Before and after the full meal.

In the above embodiment, the case of two-layer recording was described, but three-layer recording may also be used. In other words, as shown in FIG. 6, the two recording layers (301) and (30
A recording layer (30B) for PCM audio signals is added between 2), and in the same figure, (31) is the video head;
(3B) is a PCM audio head, (32) is an FM audio head, (33) is a magnetic tape, (30 is a base film, (35) is a magnetic layer, (301) is an image formed by a video head (31) Signal recording layer, (
30G) is a PCM audio signal recording layer formed by the PCM audio head (36), and (302) is an audio signal recording layer formed by the FM audio head (32).

FIG. 7 shows the spectrum of the PCM signal recorded by the PCM audio head (36), and in the same figure,
(41) and (42) are the video head (31), respectively.
) are the low frequency conversion color signal and FM luminance signal recorded by the FM audio head (51) and (52).
(74) is a two-channel FM audio carrier recorded by a PCM audio head (36).
) is a PCM audio signal recorded by.

In the configuration shown in FIG. 6, first, the FM audio head (32) is used to generate an FM audio signal (5
I), (52) are recorded on the magnetic layer (35) to form a recording layer (302), and then the PCM audio head (
The PCM audio signal (74) shown in FIG. 7 is recorded by the video head (36) to form a PCM audio signal recording layer (3o6), and the video signal (41) shown in FIG. 42) is recorded to form a video signal recording layer (301). In this case as well, since the distortion of the FM audio carrier interferes with the color signal, the gap length (g) is set to g≦0.2λ as in the above embodiment.

Further, based on the same principle, distortion of PCM audio may interfere with FM audio signals and color signals. The gap length (g) of the PCM audio head (3B) at this time is g≦0. 46 Roux, and around 0.4 enteral doses are effective.

[Effects of the Invention] As described above, according to the present invention, by configuring the gap length (g) of the recording magnetic head to be 0.2 or less of the recording wavelength of the recording signal, the reproduction output of the main signal can be increased. It is possible to suppress the recording of low frequency distortion while maintaining a sufficient amount of distortion.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of the main parts of a VH3 system VTR according to an embodiment of the present invention, FIG. 2 is a side view of FIG. 1, and FIG. 3 is a graph showing the input/output characteristics of a recording magnetic head. Fig. 4 is a graph showing the frequency characteristics of the recording depth of the magnetic recording head, Fig. 5 is a graph showing the output characteristics of the magnetic recording head,
FIG. 6 shows a VH3 system VTR according to another embodiment of the present invention.
FIG. 7 is a graph showing the spectrum of the recording signal with the configuration of FIG. 6, and FIG.
A schematic perspective view of the main parts of a three-system VTR, Figure 9 is a side view of Figure 8, Figure 10 is a graph showing the spectrum of a signal recorded in two layers, and Figure 11 is a distortion component generated in the magnetic recording system. This is a graph explaining. (31)...Video head, (32)...Audio head, (33)...Magnetic tape, (30...Base film, (35)...Magnetic layer, (3B)...
PCM audio head, (g)...Gap length. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) When the length (g) of the magnetic gap of the recording magnetic head is the recording wavelength of the recording signal (λ), g≦0.2λ
A magnetic recording/reproducing device characterized in that it is configured as follows.