JPH04315802A - Method and device for magnetic recording and reproducing - Google Patents

Abstract

PURPOSE:To enable excellent recording and reproducing in a wide band in a magnetic recording and reproducing device with a reproducing head and a recording head provided independently from each other. CONSTITUTION:The recording is performed with the recording head having a recording gap length g1 obtained from an experimental formula of G1=a.lambda<b> (where 0.45<=a<=0.55, 0.26<=b<=0.27) having a desired recording wave length lambdaas a variable, and the reproducing is performed with the reproducing head having the reproducing gap length g2 of a shortest recording wave length of lambda0/n (where 2.5<=n<=4).

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a magnetic recording and reproducing method and apparatus for video tape recorders (VTRs), and in particular,
The present invention relates to a magnetic recording and reproducing method and apparatus in which a recording head for recording information signals such as video signals on a magnetic recording medium and a reproducing head for reproducing the information signals are independently provided.

0002

[Prior Art] Conventionally, when magnetically recording and reproducing information signals on a magnetic recording medium (hereinafter referred to as a recording medium) such as a magnetic tape, there has been a method using a recording/reproducing head that serves both recording and reproduction, and a method using a recording head and a recording head. An independent system with an independent playback head can be seen.

Recording/reproducing heads have been mainly used in household VTRs and the like for convenience, but since the functions of the recording head and reproducing head are different, higher performance magnetic heads using independent magnetic heads have been used. A recording/playback device was desired.

In general, it is considered desirable for a recording head used during recording to have a magnetic gap with relatively large magnetic resistance in order to improve recording efficiency.

That is, in a recording head, magnetic flux corresponding to an information signal is transmitted to a coil wound around a ring-shaped magnetic circuit consisting of a magnetic core with a small magnetic resistance and a magnetic gap with a large magnetic resistance. Induced by passing an electric current. This magnetic flux flows through the magnetic circuit,
When the magnetic resistance of the magnetic gap is large, magnetic flux tends to leak near the magnetic gap, forming a leakage magnetic field that widely spreads outward.

At this time, when a recording medium is brought close to or in contact with the magnetic gap of the recording head and relative motion is applied to the recording head and the recording medium, changes in the leakage magnetic field are recorded as residual magnetization in the magnetic layer of the recording medium. I can do it.

[0007] When reproducing information signals recorded on this recording medium, a reproducing head having a ring-shaped magnetic circuit consisting of a magnetic gap and a magnetic core, like the recording head, is usually used.

When a recorded recording medium is brought close to or in contact with the magnetic gap of the reproducing head, the magnetic flux generated from the magnetic layer flows through the magnetic circuit so as to bypass the magnetic gap having a large magnetic resistance. At this time, when relative motion is applied between the reproducing head and the magnetic recording medium, the reproducing magnetic flux flowing through the magnetic circuit changes according to the change in residual magnetization, so an induced voltage is generated in the coil, and the information signal can be extracted as an electrical signal. I can do it.

Generally, in order to improve reproduction efficiency, it is necessary to cause no loss in the reproduction magnetic flux flowing into the magnetic circuit. Factors that affect the reproducing magnetic flux include a separation loss due to the distance d between the recording medium and the reproducing head, or an air gap loss Lg due to the gap length of the head. This air gap loss Lg can be expressed as a function of the ratio g/λ between the recording wavelength λ and the magnetic gap length g of the reproducing head. This air gap loss Lg is zero when g/λ=0, and indicates a minimum point at a value where the value of g/λ is an integer value of approximately 1 or more, and at this minimum point, the reproduced output is zero (null). (However, if g/λ is taken on the x-axis and Lg is taken on the y-axis, Lg
The value of g/λ indicating the first minimum point (the value of g/λ is approximately 1) (indicated by a minus value of ) is obtained by an approximate formula,

0
010]

[Equation 1] It is well known that Equation 1 is expressed. Therefore, the range

[0011]

[Equation 2] The void loss Lg defined by Equation 2 is a monotonically decreasing function.

Conventionally, the magnetic gap length g0 of the reproducing head
is determined to be approximately 1/3 to 1/2 of the shortest recording wavelength λ0, taking into account the gap loss of the shortest recording wavelength λ0 desired for reproduction.

[0013] Here, the method of determining the magnetic gap length of the reproducing head in the present invention will be explained.

First, a set of test signals of various wavelengths is recorded on a recording medium using a reference recording head of an appropriate type, and when this signal is reproduced by a corresponding reproduction head,
By finding the wavelength λ of the null point that indicates the first minimum value, the gap length g0 of the reproducing head is calculated backward from Equation 1 and determined electrically. The effective gap length determined by the method described above is also used as the gap length of the recording head.

On the other hand, as mentioned above, in order to improve the recording efficiency of the recording head, it is better for the magnetic gap length of the recording head to be slightly wider than the magnetic gap length of the reproducing head. It has been explained that the information spreads widely outward and is effectively recorded on the recording medium in the downstream region of the magnetic gap (the region where the recording medium is separated from the magnetic head) throughout its depth. However, since the magnetic gap length of the recording head also affects the dimensions of the recording area within the recording medium, simply being larger is not necessarily better. In other words, the shorter the magnetic gap length of the recording head, the smaller the spread of leakage magnetic flux, and the smaller the recording area for the same recording current. , it may be advantageous to make the magnetic gap length of the recording head relatively short.

[0016]

[Problems to be Solved by the Invention] When a recording head and a reproducing head are used independently in a wideband recording/reproducing device such as a VTR, it is necessary to handle a wide band from short recording wavelengths to long recording wavelengths. When placing emphasis on short recording wavelengths and shortening the magnetic gap length of the recording head, long wavelength recording cannot be performed satisfactorily; There was a disadvantage that recording of short wavelengths could not be performed sufficiently.

[0017] Therefore, how to determine the optimum magnetic gap length of the recording head has been an extremely important issue when recording over a wide band.

[0018]

[Means for Solving the Problems] The present invention has been made to solve the above problems, and includes a recording head for recording an information signal on a recording medium, and a recording head for reproducing the recorded information signal. In a magnetic recording and reproducing method in which a reproducing head is provided independently, the magnetic gap of the recording head is set to G.
1, G1 = a・λb (However, 0.45≦
a≦0.55, 0.26≦b≦0.27), where the magnetic gap length between the recording head and the reproducing head is G2, and the shortest recorded wavelength is λ0, G2 = λ
The present invention aims to provide a magnetic recording and reproducing method and an apparatus thereof, which are characterized by using a reproducing head that satisfies 0/n (2.5≦n≦4).

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory plan view of a recording head and a reproducing head used in the present invention. In the figure, 1 is a recording head, 2 is a reproducing head, and both are magnetic recording media 3.
It has a ring-shaped core having a recording gap 1a or a reproducing gap 2b on the front surface in sliding contact with the recording gap 1a or the reproduction gap 2b. Recording head 1
The ring-shaped core of the read head 2 is composed of a pair of magnetic core halves 1b, 1c and 2b, 2c, and is made of SiO2.
A magnetic closed circuit is formed by abutting each other through a magnetic gap material made of a non-magnetic material such as . A coil 1d or 2d is wound to interlink with this magnetic closed circuit.

As described above, the effective gap length determined electrically is used as the recording gap length g1 of the recording gap 1a and the reproduction gap length g2 of the reproduction gap 2a of the present invention.

FIG. 2 is a graph showing frequency allocation during recording in a home VTR, and the following description will be made using the same figure.

In conventional home VTRs, the color signal C on the high frequency side of the video signal is separated from the luminance signal Y and recorded using a different method.

That is, the color signal C is converted from a high frequency band around 3.58 MHz overlapped with the luminance signal Y to a low frequency band of 6 to 700 KH2 (low frequency converted color signal C1), and this low frequency converted color signal C1 is Luminance signal Y (5.4MHz ~ 7MHz)
It is recorded superimposed on In this case, the low-frequency conversion color signal C
1, the FM wave of the luminance signal Y serves as an AC bias, so the luminance signal Y is directly recorded.

In such a VTR system, the shortest recording wavelength λ0 corresponds to the white peak frequency (7 MHz) of the FM signal frequency of the luminance signal Y, and λ0
The value of is approximately 0.83 μm (the tape head relative speed is 5
．． 8m/sec).

In this VTR system, when the recording medium 3 coated with magnetic particles having both acicular anisotropy and cubic anisotropy is used, the signal of this shortest wavelength λ0 is most efficiently reproduced. The reproduction gap length g2 of the reproduction head is determined from the experimental results shown in FIG.
= 0.28μm, and the practical range is 0.21μm
≦gl≦0.33 μm was obtained. This length corresponds to 1/4 to 1/2.5 of the shortest recording wavelength λ0.

FIG. 3 shows the shortest recording wavelength λ0 = 0.83 μm.
The reproduction gap length g2 of the reproduction head in the recording signal of
This is a graph that experimentally determined the relationship between the reproduction gap length g2 (μm) and the relative reproduction output (μm) on the horizontal axis and the relative reproduction output (dB) on the vertical axis, where the reproduction gap length g2 = 0.
Although the reproduction output of 28 μm is normalized as 0 dB, the peak value 4 of the reproduction output is when the reproduction gap length g2 = 0.
It matches that of 28 μm.

The above experiment was conducted as follows. That is, using a magnetic head having a magnetic gap length of 0.28 μm, which has conventionally been used as the most optimal value for a recording/reproducing head, as the recording head 1, the shortest recording wavelength λ0 = 0.83 μm.
m recording signals were recorded on the recording medium 3 (tape head relative speed 5.8 m/sec) and reproduced by samples of a plurality of reproduction heads 2 having different reproduction gap lengths g2 to obtain the reproduction output of each reproduction head. As is clear from the figure, a null point 5 exists when the reproduction gap length g2 is approximately 0.73 μm.

Furthermore, the value of the reproduction gap length g2 corresponding to the point where the reproduction output is low by about 0.2 dB from the peak point 4 is as follows:
They are 0.21 μm and 0.33 μm, respectively, which are within the range of practical use as a reproducing head.

FIGS. 4 to 8 are graphs showing experimentally obtained relationships between the reproduction gap length g2 of the reproduction head and the relative reproduction output using the recording wavelength λ of the recording signal as a parameter. 1.0μm, 1.4 respectively
5μm, 2.9μm, 9.2μm, 0.64μm
The reproduction output when the reproduction gap length g2 = 0.28 μm is normalized to 0 dB as described above. As is clear from the figure, as the recording wavelength λ increases, the peak point of the relative reproduction output, that is, the value of the reproduction gap length g2 corresponding to the optimum reproduction gap length shifts to a larger value, but as shown in FIG. The maximum peak value is +1. at λ=9.2 μm.
It is about 5dB, and the playback gap length g2 is 0.28μ.
It can be seen that there is no practical problem even if m is selected.

Next, the reproduction gap length g2 of the reproduction head 2
is set to g2 = 0.28 μm, and the recording gap g1
Create recording heads with different sizes and find the optimal recording gap g1
We conducted an experiment to determine.

FIG. 9 shows the shortest recording wavelength λ0 =0.83μ
The recording gap length g of the recording head for a recording signal of m
1 and the relative reproduction output by a reproduction head with a reproduction gap length g2 = 0.28 μm. Length g1 = 0.28μm
The reproduction output at is standardized as 0 dB. The peak point 6 of the relative reproduction output exists at g10=0.5 μm, and the peak value is a small value of about +0.1 dB.

FIGS. 10 to 14 show experimentally determined relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 μm using the recording wavelength λ of the recording signal as a parameter. This is a graph. The recording wavelength λ of the parameters is 1.0 μm,
1.45μm, 29μm, 9.2μm, 0.64μm
m and recording gap length g1 as a variable, the reproduction output of each of the above wavelengths at recording gap length = 0.28 μm (head-tape relative speed 5.8 m/sec
) is normalized to 0 dB as above.

[0033]

[Table 1] Table 1 summarizes the relationship between the optimum gap length g10 for each recording wavelength λ and the maximum relative reproduction output at that time.
As is clear from the table, the optimum gap length g10 tends to increase as the recording wavelength λ increases.

For example, the shortest recording wavelength λ of the white peak
0, the maximum relative playback output is +0.1 dB, and the corresponding optimal recording gap length g10 is approximately 0.48 μm.
However, the recording wavelength λ near the low-pass conversion color signal frequency is
In the case of 9.2μm, the maximum relative playback output is +5dB,
The corresponding optimum recording gap length g10 is approximately 0.9μ
It is m.

This means that the reproduction output increases by about 5 dB compared to the recording gap length of 0.28 μm.

FIG. 15 is a logarithmic graph showing the relationship between the recording wavelength λ and the optimum recording gap length g10. is plotted. However, for recording wavelengths λ = 0.84 μm and 0.64 μm, the optimal recording gap length has a certain range;
Its central value is plotted. If we connect these points in sequence, we get the equation of the straight line shown in equation 3.

[0037]

It was found that [Equation 3] can be obtained. However, the slope of the straight line is a=0.
50, coefficient b=0.2675.

Therefore, the optimum recording gap length g10 that maximizes the relative reproduction output with respect to the recording wavelength λ can be determined by Equation 3.

[0039] Incidentally, the slope a and the coefficient b of the straight line in Equation 3 are as follows:
Although it varies somewhat depending on variations in the surface condition of the recording medium, coercive force, track width of the recording head, gap depth, etc., within the range of currently available recording media and magnetic heads, the invention is within the following range. This has been experimentally confirmed by others.

That is, the slope b of the straight line is 0.26≦a≦
0.27, and the coefficient b is 0.45≦b≦0.55, and the optimum recording length may be determined using a number 3 within this range.

More specifically, when the recording gap length is focused on the shortest recording wavelength λ0 corresponding to the white peak frequency of 7 MHz of the luminance signal (recording wavelength 0.
(equivalent to 28 μm), recording gap length g1 is approximately 0.48
μm, or when placing emphasis on the recording wavelength λ corresponding to the low-pass conversion color signal frequency of around 630 KHz (recording wavelength λ=
9.2 μm) and 0.9 μm. In addition, if both are important, the recording wavelength λ at the midpoint is
All you have to do is choose.

In the VTR system used in the present invention, the range of the optimum recording gap length g10 in the range of straight line slope a of 0.26≦a≦0.27 and the range of coefficient b of 0.45≦b≦0.55. can be obtained from Equation 3 as shown in Equation 4. (However, the recording wavelength λ is 0.28 μm ≦λ≦9.2
μm)

[0043]

[Equation 4] As mentioned above, by determining the recording gap length according to Equation 3, it is possible to efficiently record over a wide band compared to the conventional magnetic head that can be used as both a recording and reproducing head (magnetic gap length 0.28 μm). This makes it possible to realize a magnetic recording and reproducing device that has clearer color images and higher resolution images than conventional VTRs.

[0044]

As described above, in the magnetic recording and reproducing method in which a recording head for recording an information signal on a recording medium and a reproducing head for reproducing the recorded information signal are independently provided, The magnetic gap of the recording head is G1
When G1 = a・λb (however, 0.45≦a≦
0.55, 0.26≦b≦0.27) and the magnetic gap length between the recording head and the reproducing head is G2, and the shortest recorded wavelength is λ0, then G2 = λ0
/n (however, 2.5≦n≦4), good recording and playback characteristics can be obtained over a wide band, and for example in VTR systems, conventional recording and playback characteristics are achieved.
It is possible to provide a recording/reproducing device that has high resolution and clear color images compared to a device using a re-head.

[Brief explanation of the drawing]

FIG. 1 is an explanatory plan view of a recording head and a reproducing head used in the present invention.

FIG. 2 is a graph showing frequency allocation during recording in a home VTR.

FIG. 3 is a graph obtained experimentally of the relationship between the reproduction gap length g2 of the reproduction head and the relative reproduction output for a recording signal with the shortest recording wavelength λ0 = 0.83 μm.

FIG. 4 is a graph obtained experimentally of the relationship between the reproduction gap length g2 of the reproduction head and the relative reproduction output for a recording signal with a recording wavelength λ=1.00 μm.

FIG. 5 is a graph obtained experimentally of the relationship between the reproduction gap length g2 of the reproduction head and the relative reproduction output for a recording signal with a recording wavelength λ=1.45 μm.

FIG. 6 is a graph obtained experimentally of the relationship between the reproduction gap length g2 of the reproduction head and the relative reproduction output for a recording signal with a recording wavelength λ=2.90 μm.

FIG. 7 is a graph obtained experimentally of the relationship between the reproduction gap length g2 of the reproduction head and the relative reproduction output in a recording signal with a recording wavelength λ=9.20 μm.

FIG. 8 is a graph obtained experimentally of the relationship between the reproducing gap length g2 of the reproducing head and the relative reproducing output for a recording signal with a recording wavelength λ=0.64 μm.

[Fig. 9] Recording with the shortest recording wavelength λ0 = 0.83 μm.
It is a graph obtained experimentally of the relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 μm in the signal.

FIG. 10 is a graph obtained experimentally of the relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 μm for a recording signal with a recording wavelength λ = 1.00 μm. .

FIG. 11 is a graph obtained experimentally of the relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 μm for a recording signal with a recording wavelength λ = 1.45 μm. .

FIG. 12 is a graph obtained experimentally of the relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 µm for a recording signal with a recording wavelength λ = 2.90 µm. .

FIG. 13 is a graph obtained experimentally of the relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 µm for a recording signal with a recording wavelength λ = 9.20 µm. .

FIG. 14 is a graph obtained experimentally of the relationship between the recording gap length g1 of the recording head and the relative reproduction output of the reproduction head with the reproduction gap length g2 = 0.28 μm for a recording signal with a recording wavelength λ = 0.64 μm. .

FIG. 15 is a log-log graph showing the relationship between the recording wavelength λ and the optimum recording gap length g10.

[Explanation of symbols]

1 Recording head 1a Recording head magnetic gaps 1b, 1c
Recording head magnetic core half 1d Recording head coil 2 Reproduction head 2a Reproduction head reproduction gaps 2a, 2b
Reproducing head magnetic core half 2d Reproducing vent coil 3 Recording medium g1 Recording gap length g2 Reproducing gap length g10 Optimum recording gap length

Claims (2)

[Claims] 1. A magnetic recording and reproducing method in which a recording head for recording an information signal on a recording medium and a reproducing head for reproducing the recorded information signal are independently provided, comprising:
When the magnetic gap of the recording head is G1, G1
=a・λb (However, 0.45≦a≦0.55, 0.
26≦b≦0.27), the magnetic gap length between the recording head and the reproducing head is G2, and the shortest recorded wavelength is λ0, then G2 = λ0 /n (however, 2
．． A magnetic recording and reproducing method characterized by using a reproducing head that satisfies (5≦n≦4). 2. A magnetic recording and reproducing apparatus independently comprising a recording head for recording an information signal on a recording medium and a reproducing head for reproducing the recorded information signal,
When the magnetic gap length of the recording head is G1,
G1 = a・λb (However, 0.45≦a≦0.55,
0.26≦b≦0.27), and the magnetic gap length between the recording head and the reproducing head is G2, and the shortest recorded wavelength is λ0, then G2 = λ0 /n (however,
2.5≦n≦4) A magnetic recording and reproducing device characterized in that it uses a reproducing head that satisfies the following.