JPH04328308A - Composite type magnetic head - Google Patents

Abstract

PURPOSE:To shield the leakage magnetic fluxes from another magnetic head and to decrease the crossinterferences of recording and reproduced signals. CONSTITUTION:This composite type magnetic head is constituted by disposing a pair of the magnetic heads 57, 58 formed with magnetic gaps g1, g2 having azimuth angles theta1, theta2 varying from each other in proximity to face each other in the traveling direction of the heads and is provided with thin films 93, 94 of good conductors which shield the leakage magnetic fluxes from the magnetic gaps g1, g2 of these magnetic heads 57, 58 on the opposite surface 62b, 77b facing each other of these magnetic heads 57, 58.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to, for example, digital VT
The present invention relates to a composite magnetic head useful for use in R (digital video tape recorder) and the like.

0002

2. Description of the Related Art When recording and reproducing a large amount of data at once in magnetic recording, for example, as shown in FIG. 12, magnetic gaps g1 and g having different azimuth angles are formed.
A pair of magnetic heads 101 and 102 having a magnetic tape 101 and 102 are arranged adjacent to each other at a predetermined interval in the head running direction indicated by the arrow Recording and reproducing methods are effective.

By the way, the above magnetic heads 101 and 102
When performing helical scanning, these magnetic heads 1
As the running angle of the magnetic heads 1 and 102 with respect to the magnetic tape 103 increases, it becomes necessary to reduce the gap distance GL between the two magnetic heads 101 and 102 from the viewpoint of high-density recording of the amount of recorded information.

However, the magnetic head 101,1
When the gap distance GL of 02 is decreased, the magnetic cores 105, 1 facing each other among the magnetic cores 104, 105 and 106, 107 forming the magnetic gaps g1, g2
Since the facing distance L of 07 is close, a problem of leakage magnetic flux occurs. That is, the magnetic flux generated from one magnetic gap g1 enters the other magnetic gap g2, causing mutual interference (crosstalk) with the recording/reproduction signal of the other magnetic gap g2. As a result, the recording/reproduction signal deteriorates, making it impossible to perform good recording/reproduction.

Therefore, in the past, the above-mentioned magnetic head 1
There is a method of arranging a magnetic shielding plate to shield leakage magnetic flux between 01 and 102, and a method of winding a coil around these magnetic heads 101 and 102 in a figure 8 shape, and using this figure 8 coil to reverse the phase of the signal component due to the leakage magnetic flux. A method was used in which the two factors were combined to cancel each other out.

However, when considering recording and reproducing more data, the facing distance L between the magnetic heads 101 and 102 becomes smaller, so it is necessary to provide a magnetic shielding plate in the minute gap, 101, 102
It is difficult to wind a figure-eight coil in any case.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned conventional circumstances, and is intended to reliably shield magnetic flux leakage from one of the magnetic heads disposed close to each other. An object of the present invention is to provide a composite magnetic head that can prevent mutual interference between recording and reproduction signals and perform good recording and reproduction.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention arranges a pair of magnetic heads having magnetic gaps having different azimuth angles in close proximity to each other and facing each other in the head running direction. This composite magnetic head is characterized in that a good conductor thin film is formed on at least one of the mutually opposing surfaces of these magnetic heads to shield magnetic flux leakage from the magnetic gap of the other magnetic head.

[0009]

[Operation] In the composite magnetic head according to the present invention,
A good conductor thin film is provided on at least one of the mutually opposing surfaces of a pair of magnetic heads that are arranged close to each other and face each other in the head running direction, so that the other magnetic head is provided with a thin film of good conductivity that shields leakage magnetic flux from the magnetic gap of the other magnetic head. The leakage magnetic flux from the magnetic head is shielded by the good conductor thin film. Therefore, mutual interference between recording and reproduction signals of these magnetic heads is reduced, and good recording and reproduction can be performed.

0010

[Embodiments] Specific embodiments to which the present invention is applied will be described below. In this example, the amount of recorded information is compressed with little reproduction distortion, the track width is 10 μm or less, and the short wavelength is 0.
．． It has a high recording density of 1.25μm2/bit at 5μm, and a tape width of 8μm with a low bit error rate.
A composite magnetic head, in which a pair of magnetic heads with different azimuth angles are placed close to each other and facing each other in the head running direction, enables long-term recording and playback of digital image signals on a narrow magnetic tape. This is an example.

First, a method for compressing the amount of recorded information with less reproduction distortion will be explained with reference to the drawings. This method converts an input digital image signal into block-by-block data consisting of a plurality of pixel data, compresses and encodes the blocked data in block units, and converts the compression-encoded data into a channel code. The channel-encoded data is recorded on a magnetic tape by the magnetic head of this embodiment mounted on a rotating drum. Hereinafter, the configuration on the recording side and the configuration on the reproduction side will be explained separately.

FIG. 1 shows the entire configuration of the recording side, in which a digital luminance signal Y formed from three primary color signals R, G, and B from a color video camera, for example, is input to input terminals indicated by 1Y, 1U, and 1V, respectively. , digital color difference signal U
, V are supplied. In this case, the clock rate of each signal is the same as the frequency of each component signal of the D1 format. That is, the sampling frequencies are 13.5 MHz and 6.75 MHz, and the number of bits per sample is 8 bits. Therefore, the data amount of the signals supplied to the input terminals 1Y, 1U, and 1V is approximately 216 Mbps. The data amount is compressed to approximately 167 Mbps by a valid information extraction circuit 2 which removes blanking time data from this signal and extracts only information in the valid area.

The luminance signal Y of the output of the effective information extraction circuit 2 is supplied to the frequency conversion circuit 3, and the sampling frequency is converted from 13.5 MHz to 3/4 of that. For example, a thinning filter is used as the frequency conversion circuit 3 to prevent aliasing distortion from occurring. The output signal of the frequency conversion circuit 3 is supplied to the blocking circuit 5, and the order of luminance data is converted into the order of blocks. The blocking circuit 5 is provided for the block encoding circuit 8 provided at the subsequent stage.

FIG. 3 shows the structure of a coding unit block. This example is a three-dimensional block, and by dividing a screen spanning, for example, two frames, a large number of unit blocks (4 lines x 4 pixels x 2 frames) are formed as shown in the figure. Note that in FIG. 3, solid lines indicate lines for odd fields, and broken lines indicate lines for even fields.

Furthermore, among the outputs of the effective information extraction circuit 2,
Two color difference signals U and V are supplied to a sub-sampling and sub-line circuit 4, each having a sampling frequency of 6.
．． After being converted from 75 MHz to half that, the two digital color difference signals are selected line by line from each other and combined into one channel of data. Therefore, a line-sequential digital color difference signal is obtained from this sub-sampling and sub-line circuit 4. FIG. 4 shows the pixel configuration of the signal converted into sub-samples and sub-lines by the sub-sampling and sub-line circuit 4. In FIG. 4, ◯ indicates a sub-sampling pixel of the first color difference signal U, △ indicates a sampling pixel of the second dye signal V, and × indicates the position of a pixel thinned out by the sub-samples.

The line sequential output signal of the sub-sampling and sub-line circuit 4 is supplied to a blocking circuit 6. In the blocking circuit 6, similarly to the blocking circuit 5,
Scan order color difference data of the television signal is converted to block order data. This blocking circuit 6, like one of the blocking circuits 5, converts the color difference data into (4
Convert to a block structure of lines x 4 pixels x 2 frames). The output signals of these blocking circuits 5 and 6 are supplied to a combining circuit 7.

In the synthesis circuit 7, the luminance signal and the color difference signal converted into the block order are converted into one-channel data, and the output signal of the synthesis circuit 7 is sent to the block encoding circuit 8.
supplied to This block encoding circuit 8 includes an encoding circuit adapted to the dynamic range of each block (referred to as ADRC), DCT (Dis
create Cosine Transform)
Circuits etc. can be applied. The output signal of the block encoding circuit 8 is supplied to the framing circuit 9 and converted into data having a frame structure. In this framing circuit 9, switching between the pixel system clock and the recording system clock is performed.

The output signal of the framing circuit 9 is supplied to an error correction code parity generation circuit 10 to generate the parity of the error correction code. The output signal of the parity generation circuit 10 is supplied to a channel encoder 11, and channel coding is performed to reduce the low frequency portion of the recorded data. The output signal of the channel encoder 11 is supplied to a pair of magnetic heads 13A, 13B via recording amplifiers 12A, 12B and a rotary transformer (not shown), and is recorded on a magnetic tape. Note that the audio signal and the video signal are compressed and encoded separately and supplied to the channel encoder 11.

By the above signal processing, the input data amount of 216 Mbps is reduced to approximately 167 Mbps by extracting only the effective scanning period, and further reduced to 84 Mbps by frequency conversion, sub-sampling, and sub-line. This data is compressed to approximately 25 Mbps by compression encoding in the block encoding circuit 8,
Adding additional information such as subsequent parity and audio signals, the amount of recorded data is approximately 31.56 Mbps.

Next, the configuration on the playback side will be explained with reference to FIG. 2. In FIG. 2, magnetic heads 13A, 13
The playback data from B is transferred to the rotating transformer and playback amplifier 14.
It is supplied to the channel decoder 15 via A and 14B. The channel decoder 15 demodulates the channel coding, and the output signal of the channel decoder 15 is supplied to a TBC circuit (time base correction circuit) 16. In this TBC circuit 16, time axis fluctuation components of the reproduced signal are removed. The reproduced data from the TBC circuit 16 is supplied to the ECC circuit 17, where error correction and correction using an error correction code are performed. The output signal of the ECC circuit 17 is supplied to a frame decomposition circuit 18.

The frame decomposition circuit 18 separates each component of the block encoded data, and
The recording system clock is switched to the pixel system clock. Each piece of data separated by the frame decomposition circuit 18 is supplied to a block decoding circuit 19, where restored data corresponding to the original data is decoded for each block, and the decoded data is supplied to a distribution circuit 20. This distribution circuit 20 separates the decoded data into a luminance signal and a color difference signal. The luminance signal and the color difference signal are supplied to block decomposition circuits 21 and 22, respectively. The block decomposition circuits 21 and 22 convert the decoded data in the order of blocks into the order of raster scanning, contrary to the blocking circuits 5 and 6 on the transmitting side.

The decoded luminance signal from the block decomposition circuit 21 is supplied to an interpolation filter 23. In the interpolation filter 23, the sampling rate of the luminance signal is 3fs to 4fs.
(4fs=13.5MHz). Digital luminance signal Y from interpolation filter 23 is taken out to output terminal 26Y.

On the other hand, the digital color difference signals from the block decomposition circuit 22 are supplied to the distribution circuit 24, and the line sequential digital color difference signals U and V are separated into digital color difference signals U and V, respectively. The digital color difference signals U and V from the distribution circuit 24 are supplied to an interpolation circuit 25, where they are interpolated. The interpolation circuit 25 interpolates thinned line and pixel data using the restored pixel data, and the sampling rate is 4f from the interpolation circuit 25.
s digital color difference signals U and V are obtained, and the output terminal 2
It is taken out to 6U and 26V respectively.

By the way, the above-mentioned block encoding circuit 8 is an ADRC (Adaptive Dynamic
(Range Coding) encoder is used. This ADRC encoder detects the maximum value MAX and minimum value MIN of multiple pixel data included in each block, detects the dynamic range DR of the block from these maximum value MAX and minimum value MIN, and adapts to this dynamic range DR. Then, requantization is performed using a smaller number of bits than the number of bits of the original pixel data. Another example of the block encoding circuit 8 is to convert the pixel data of each block into DCT (Discrete C
osine Transform), this DC
A configuration may be used in which the coefficient data obtained at T is quantized, the quantized data is run-length Huffman encoded, and compression encoded.

[0025]Here, an example of an encoder that uses an ADRC encoder and does not cause image quality deterioration even when multi-dubbing is performed will be described with reference to FIG. In FIG. 5, a digital video signal (or digital color difference signal) in which one sample is quantized to 8 bits, for example, is inputted to an input terminal 27 from the synthesis circuit 7 of FIG. Input terminal 2
Blocked data from 7 is maximum value, minimum value detection circuit 2
9 and a delay circuit 30. The maximum value and minimum value detection circuit 29 detects the minimum value MIN and maximum value MAX for each block.
Detect. The input data from the delay circuit 30 is delayed by the time required for the maximum value and minimum value to be detected. Pixel data from the delay circuit 30 is supplied to a comparison circuit 31 and a comparison circuit 32.

The maximum value MAX from the maximum value/minimum value detection circuit 29 is supplied to a subtraction circuit 33, and the minimum value MIN is supplied to an addition circuit 34. The subtraction circuit 33 and the addition circuit 34 are supplied with a value of one quantization step width (Δ=1/16DR) when performing non-edge matching quantization with a fixed length of 4 bits from the bit shift circuit 35. The bit shift circuit 35 is configured to shift the dynamic range DR by 4 bits so as to perform division by (1/16). The subtraction circuit 33 obtains a threshold value of (MAX-Δ), and the addition circuit 34 obtains a threshold value of (MIN+Δ). Threshold values from these subtraction circuit 33 and addition circuit 34 are supplied to comparison circuits 31 and 32, respectively. Note that the value Δ that defines this threshold value is not limited to the quantization step width, and may be a fixed value corresponding to the noise level.

The output signal of the comparator circuit 31 is connected to the AND gate 3
6, and the output signal of the comparison circuit 32 is supplied to the AND gate 37. Input data from the delay circuit 30 is supplied to the AND gate 36 and the AND gate 37. The output signal of the comparison circuit 31 becomes high level when the input data is larger than the threshold value, and therefore, the output terminal of the AND gate 36 receives pixel data of the input data included in the maximum level range of (MAX to MAX-△). is extracted. On the other hand, the output signal of the comparator circuit 32 becomes high level when the input data is smaller than the threshold value, and therefore the output terminal of the AND gate 37 has (MIN~MIN+
Pixel data of input data included in the minimum level range of Δ) is extracted.

The output signal of AND gate 36 is supplied to an averaging circuit 38, and the output signal of AND gate 37 is supplied to an averaging circuit 39. These averaging circuits 38, 39
calculates an average value for each block, and a block period reset signal is sent from the terminal 40 to the averaging circuits 38 and 39.
is supplied to. From the averaging circuit 38, (MAX~
The average value MAX' of the pixel data belonging to the maximum level range of MAX-△) is obtained, and the average value MAX' of the pixel data belonging to the maximum level range of
An average value MIN' of pixel data belonging to the minimum level range of .about.MIN+Δ) is obtained. The average value MIN' is subtracted from the average value MAX' by a subtraction circuit 41, and the dynamic range DR' is obtained from the subtraction circuit 41.

Further, the average value MIN' is supplied to the subtraction circuit 42, and the average value MIN' is subtracted from the input data passed through the delay circuit 43 in the subtraction circuit 42, thereby forming data PDI after the minimum value has been removed. . This data PDI and the modified dynamic range DR' are sent to the quantization circuit 44.
supplied to In this embodiment, the number of bits n allocated for quantization is 0 bits (no code signal is transferred),
It is a variable length ADRC of 1 bit, 2 bits, 3 bits, or 4 bits, and edge matching quantization is performed. The allocated bit number n is determined for each block by the bit number determination circuit 45, and data with the bit number n is supplied to the quantization circuit 44.

[0030] The variable length ADRC has a dynamic range D
Efficient encoding can be performed by reducing the number n of allocated bits for a block with a small R' and increasing the number n of allocated bits for a block with a large dynamic range DR'. That is, the threshold value for determining the number of bits n is T1 to T4 (T1<T2<T3<T
4), the code signal is not transferred to the block with (DR′<T1), and only the information of the dynamic range DR′ is transferred, and the block with (T1≦DR′<T2) is
(n=1), (T2≦DR'<T3) blocks are (n=2), (T3≦DR'<T4) blocks are (n=3), (DR The block where '≧T4) is (n=4).

In such variable length ADRC, the threshold value T1~
By changing T4, the amount of generated information can be controlled (so-called buffering). Therefore, variable length ADRC can also be applied to a transmission line such as the digital video tape recorder of the present invention, which requires the amount of information generated per field or frame to be a predetermined value.

The buffering circuit 46 that determines the threshold values T1 to T4 for setting the generated information amount to a predetermined value has a plurality of sets of threshold values (T1, T2, T3, T4), for example, three sets.
Two sets of threshold values are prepared, and these sets of threshold values are distinguished by parameter codes Pi (i=0, 1, 2, . . . , 31). The amount of generated information is set to decrease monotonically as the number i of the parameter code Pi increases. However, as the amount of generated information decreases, the quality of the restored image deteriorates.

Threshold value T from buffering circuit 46
1 to T4 are supplied to the comparator circuit 47, and the dynamic range DR' via the delay circuit 48 is supplied to the comparator circuit 47. Delay circuit 48 delays DR' by the time required for buffering circuit 46 to determine the set of thresholds. In the comparison circuit 47, the dynamic range DR' of the block is compared with each threshold value, and the comparison output is supplied to the bit number determination circuit 45, which determines the number n of allocated bits for the block. The quantization circuit 44 uses the dynamic range DR' and the assigned number of bits n to calculate the minimum value removed data P that has been passed through the delay circuit 49.
DI becomes code signal D by edge matching quantization.
Converted to T. The quantization circuit 44 is composed of, for example, a ROM.

The corrected dynamic range DR' and average value MIN' are outputted via the delay circuits 48 and 50, respectively, and furthermore, a parameter code Pi indicating a combination of the code signal DT and the threshold value is outputted. In this example, since the signal that has been non-edge match quantized is newly edge match quantized based on dynamic range information, there is little image deterioration when dubbing.

Next, the above-mentioned channel encoder 11 and channel decoder 15 will be explained. As shown in FIG. 6, the channel encoder 11 is an adaptive scrambling circuit to which the output of the parity generation circuit 10 is supplied, and is provided with a plurality of M-sequence scrambling circuits 51. The configuration is such that an M sequence that provides an output with few DC components and direct current components is selected. Precoder 52 for partial response class 4 detection method, 1/1-D2
(D is a unit delay circuit) calculation processing is performed. The output of this precoder 52 is recorded and reproduced by magnetic heads 13A, 13B via recording amplifiers 12A, 13A, and the reproduced output is amplified by reproduction amplifiers 14A, 14B.

On the other hand, in the channel decoder 15, as shown in FIG.
The arithmetic processing circuit 53 on the playback side performs the calculation of 1+D on the outputs of the playback amplifiers 14A and 14B. In addition, in the so-called Viterbi decoding circuit 54, the arithmetic processing circuit 5
Noise-resistant data decoding is performed on the output of No. 3 by calculation using data correlation, certainty, etc. The output of the Viterbi decoding circuit 54 is supplied to a descrambling circuit 55, and the data rearranged by the scrambling process on the recording side is returned to the original sequence, thereby restoring the original data. The Viterbi decoding circuit 54 used in this embodiment provides a 3 dB improvement in reproduction C/N conversion compared to the case where bit-by-bit decoding is performed.

Next, a composite magnetic head according to this embodiment for recording channel-encoded data on a magnetic tape using the above-described method will be described. As shown in FIGS. 8 and 9, the composite magnetic head of this embodiment has different azimuth angles θ1 and θ on the same head base 56.
A pair of magnetic heads 57 and 58 having magnetic gaps g1 and g2 having a magnetic gap g1 and g2 of There is. In addition,
The magnetic heads 57 and 58 correspond to the magnetic heads 13A and 13B shown in FIGS. 1 and 2 described above.

First, one of the magnetic heads 57 and 58 will be explained by taking as an example. The magnetic head 57 includes a first magnetic core portion 59 made of a ferromagnetic oxide material and a ferromagnetic metal thin film 60 deposited on the magnetic core portion 59 using a vacuum thin film forming technique.
The magnetic core half 61 , and the second magnetic core half 64 similarly composed of a magnetic core portion 62 made of a ferromagnetic oxide material and a ferromagnetic metal thin film 63 are connected to the ferromagnetic metal thin film 6 .
0 and 63 are abutted surfaces, and are integrally joined by a fused glass 65.

The magnetic core portion 59 constituting the first magnetic core half 61 is made of, for example, Mn-Zn ferrite or Ni-
For winding a coil (not shown) made of a ferromagnetic oxide material such as Zn ferrite, which supplies recording signals to the surface facing the ferromagnetic metal thin film 60 or extracts reproduction signals from the magnetic tape. It has a coil winding groove 66. Furthermore, a glass groove 67 is provided on the surface of the magnetic core portion 59 facing the ferromagnetic metal thin film 60, which is filled with a fused glass 65 in order to make the bonding with the second magnetic core half body 64 more reliable. is formed. The coil winding groove 66 is formed in the magnetic core portion 5 which becomes the surface in contact with the magnetic tape.
The inclined surface 66a on the magnetic recording medium contacting surface 68 side regulates the depth of the magnetic gap g1 of the magnetic head 57. On the other hand, the glass groove 67
It is provided in the vicinity of the surface 69 on the opposite side to the magnetic recording medium contacting surface 68 of No. 9, and is formed as a shallow groove with a concave side surface.

The portion of the magnetic core portion 59 facing the ferromagnetic metal thin film 60 is cut out on both sides in the chip thickness direction, and a substantially central portion thereof remains long and narrow along the sliding direction of the magnetic tape. It is formed to do so. A cutout portion 70 that cuts out the opposing portion of the magnetic core portion 59;
Reference numeral 71 is a track width regulating groove for regulating the track width Tw1 of the magnetic gap g1 of the magnetic head 57. Therefore, the elongated core portion (hereinafter referred to as metal thin film forming portion 59a) 59a formed by the cutout portions 70 and 71 forms the magnetic gap g1.
The width is the same as the track width Tw1 of . The metal thin film forming portion 59a is inclined at the same angle as the azimuth angle θ1 of the magnetic gap g1 with respect to the sliding direction of the magnetic tape.

On the other hand, the ferromagnetic metal thin film 60 is attached to the magnetic recording medium facing surface 6 along the surface facing the metal thin film forming portion 59a.
From side 8, the surface 69 on the opposite side is covered. That is, the ferromagnetic metal thin film 60 is deposited over the entire opposing surface of the metal thin film forming portion 59a, except for the coil winding groove 66 and the glass groove 67. For this ferromagnetic metal thin film 60, a ferromagnetic material having a high saturation magnetic flux density and excellent soft magnetic properties is used.

Such ferromagnetic materials include Fe-Al-
Si alloy, Fe-Al alloy, Fe-Si-Co alloy, Fe-Ni alloy, Fe-Al-Ge alloy, Fe
-Ga-Ge alloy, Fe-Si-Ge alloy, Fe-
Ferromagnetic metal materials such as Co-Si-Al alloys, or F
e-Ga-Si alloys, and even the above-mentioned Fe-Ga-Si
In order to further improve the corrosion resistance and wear resistance of the alloys,
In an alloy whose basic composition is Fe, Ga, Co (including those in which a part of Fe is replaced with Co), Si, Ti, Cr,
Mn, Zr, Nb, Mo, Ta, W, Ru, Os, Rh
, Ir, Re, Ni, Pb, Pt, Hf, and V.

In addition, ferromagnetic amorphous alloys, so-called amorphous alloys (for example, alloys consisting of one or more elements of Fe, Ni, Co and one or more elements of P, C, B, Si, or The main components are Al, Ge, Be, Sn, I
Metal-metalloid amorphous alloys such as alloys containing n, Mo, W, Ti, Mn, Cr, Zr, H, Nb, etc., or whose main components are transition elements such as Co, Hf, Zr, rare earth elements, etc. Metal-metal amorphous alloys) etc. are also used.

Among these ferromagnetic materials, 1.25 μm
In order to achieve a high recording density of 2/bit or more, it is particularly preferable to use a material with a saturation magnetic flux density of 14 kG or more, for example, Fe-G with a saturation magnetic flux density of 14.5 kG.
An a-Si-Ru alloy is preferred. If such a ferromagnetic material having a high saturation magnetic flux density is used, recording can be performed even on a magnetic tape having a high coercive force without causing magnetic saturation. The method for depositing the ferromagnetic material is as follows:
Vacuum thin film formation technology, such as evaporation method, sputtering method,
Examples include ion plating method.

On the other hand, the magnetic core portion 62 constituting the second magnetic core half 64 is made thinner in the sliding direction of the magnetic tape, and is made of Mn-Zn ferrite or Ni like the magnetic core portion 59 described above. - Made of ferromagnetic oxide material such as Zn ferrite. The portion of the magnetic core portion 62 that faces the ferromagnetic metal thin film 63 is cut out on both sides in the chip thickness direction, and is formed so that its substantially central portion remains elongated along the sliding direction of the magnetic tape. ing. Cutout portions 72 and 73 that cut out opposing portions of the magnetic core portion 62
Similar to the magnetic core portion 59 described above, these are track width regulating grooves that regulate the track width Tw1 of the magnetic gap g1 of this magnetic head 57. Therefore, the elongated core portion (hereinafter referred to as metal thin film forming portion 62a) 62a formed by the notches 72 and 73 has the same width as the track width Tw1 of the magnetic gap g1. Note that, like the metal thin film forming part 59a, this metal thin film forming part 62a is also formed in the same direction as the metal thin film forming part 59a and at the same angle as the azimuth angle θ1 of the magnetic gap g1 with respect to the sliding direction of the magnetic tape. Have been slanted.

The ferromagnetic metal thin film 63 is coated as a continuous film along the opposing surface of the metal thin film forming portion 62a from the magnetic recording medium facing surface 68 to the opposite surface 69. It is formed. Note that this ferromagnetic metal thin film 63 is made of the same ferromagnetic material as the ferromagnetic metal thin film 60 described above.

The first magnetic core half 61 and the second magnetic core half 64 constructed as described above are brought into contact with each other using the ferromagnetic metal thin films 60 and 63 as abutment surfaces, and are Notches 70, 72 and 71, 73 facing each other
A fused glass 65 is filled in between and the two are integrally bonded. Then, these first magnetic core half bodies 61 and the second magnetic core half body 61
The magnetic core half 64 is the ferromagnetic metal thin film 60, 6
By interposing a fused glass 65 or a gap spacer between the ferromagnetic metal thin films 60 and 63, a magnetic gap g1 having a track width Tw1 is formed at the interface between the ferromagnetic metal thin films 60 and 63. The magnetic gap g1 here is provided with a predetermined azimuth angle θ1 in the clockwise direction with respect to the direction perpendicular to the sliding direction of the magnetic tape.

Further, the azimuth angle θ1 is preferably set to 10 degrees or more in order to reduce crosstalk from the magnetic gap g2 of one of the magnetic heads 58 provided on the same head base 56. In this example, the azimuth angle θ1 of the magnetic gap g1 is 2
It was 0 degrees. In addition, the track width Tw1 of the magnetic gap g1 is as follows: In the case of ATF (auto tracking), recording and reproduction are performed while picking up signals from adjacent tracks.
+0μm to +3μ from track pitch P on magnetic tape
It is desirable to widen the area by m. In addition, the above magnetic gap g
If the track width Tw1 of 1 is made too wide, adjacent crosstalk during reproduction will become large, so the above range is most desirable. Specifically, since the track pitch P is 10 μm or less, the track width Tw1 of the magnetic gap g1 is 10 μm to 13 μm. In this embodiment, since the track pitch P on the magnetic tape is 5 μm, the track width Tw1 is set to 7 μm.

In particular, in the magnetic head 57, the surface facing the other magnetic head 58 disposed close to each other, that is, the surface facing the magnetic core portion 62 constituting the second magnetic core half 64. The other magnetic head 5 is attached to 62b.
A thin film 93 of good conductivity is formed to shield magnetic flux leakage from the magnetic gap g2 of 8. The good conductor thin film 93 is
Conductor thin film with small electrical resistivity ρ, for example electrical resistivity ρ<
It consists of a thin film of silver, Cr, and aluminum with a thickness of 10 −6 Ω·cm. This good conductor thin film 93 is formed over the entire opposing surface 62b of the magnetic core portion 62 by, for example, a thin film manufacturing process, such as wet or dry plating. The thickness of the good conductor thin film 93 at this time is 1 μm to 1 μm in order to reliably shield leakage magnetic flux from the other magnetic head 58.
It is desirable that the thickness be about 50 μm. If the film thickness is less than 1 μm, it becomes difficult to reliably shield leakage magnetic flux. Note that the upper limit of the film thickness may be 50 μm or more, but this is limited by the distance between the magnetic head 58 and the opposing magnetic head 58 .

When the good conductor thin film 93 is provided, when the leakage magnetic flux from the other magnetic head 58 tries to flow into this magnetic head 57, an eddy current is generated in the good conductor thin film 93 according to the amount of magnetic flux change, and the external Generates a magnetic field in a direction that prevents changes in the magnetic field. As a result, leakage magnetic flux from the other magnetic head 58 is shielded by the good conductor thin film 93.

The other magnetic head 58 has a similar configuration, with a third magnetic core consisting of a magnetic core portion 74 made of a ferromagnetic oxide material and a ferromagnetic metal thin film 75 deposited on this magnetic core portion 74. The half body 76 and a fourth magnetic core half body 79 similarly composed of a magnetic core portion 77 made of a ferromagnetic oxide material and a ferromagnetic metal thin film 78 protrude through the ferromagnetic metal thin films 75 and 78. Fused glass 80 as mating surface
It is constructed by being joined and integrated.

In this magnetic head 58, similarly to the magnetic head 57 described above, the portions of the magnetic core portions 74 and 77 facing the respective ferromagnetic metal thin films 75 and 78 have opposite sides thereof in the chip thickness direction. The notch is formed so that its substantially central portion remains elongated along the sliding direction of the magnetic tape. The cutout portions 81, 82 and 83, 84 which cut out the opposing portions of the magnetic core portions 74, 77 have a track width Tw of the magnetic gap g2 of the magnetic head 58.
2. This is a track width regulating groove that regulates the width of the track. Therefore, the elongated core portions 74a, 77a (hereinafter referred to as metal thin film forming portions 74a, 77a) formed by these notches 81, 82 and 83, 84 are as follows:
The width is the same as the track width Tw2 of the magnetic gap g2.

Note that the metal thin film forming portions 74a and 77a
is inclined at the same angle as the azimuth angle θ2 of the magnetic gap g2 with respect to the sliding direction of the magnetic tape in the opposite direction to the previous metal thin film forming portions 59a and 62a. Further, a coil winding groove 85 and a glass groove 86 are formed on the surface of the one magnetic core portion 74 facing the ferromagnetic metal thin film 75 . A side surface 77b of the other magnetic core section 77 opposite to the metal thin film forming section 77a is inclined in the opposite direction to that of the magnetic core section 62 of the magnetic head 57.

On the other hand, in the ferromagnetic metal thin films 75 and 78, the ferromagnetic material is formed on the magnetic recording medium facing surface 87 of the magnetic core portion 74 along the opposing surfaces of the metal thin film forming portions 74a and 77a. Therefore, the surface 88 on the opposite side is formed by a vacuum thin film forming technique.

In this magnetic head 58, the third magnetic core half 76 and the fourth magnetic core half 79 are abutted against each other using their ferromagnetic metal thin films 75 and 78 as abutting surfaces, so that they face each other. Notches 81, 82 and 8
A fused glass 80 is filled between 3 and 84 and bonded and integrated. A magnetic gap g2 having a track width Tw2 is formed between the ferromagnetic metal thin films 75 and 78. The magnetic gap g2 here is provided with a predetermined azimuth angle θ2 in the counterclockwise direction with respect to the direction perpendicular to the sliding direction of the magnetic tape. That is, the azimuth of the magnetic gap g2 is opposite to the azimuth of the magnetic gap g1 of the magnetic head 57. Note that the azimuth angle θ of the magnetic gap 2 is
2 is set to the same angle as the azimuth θ2 of the magnetic gap g1.

In this magnetic head 58, similarly to the previous magnetic head 57, the surface of the magnetic head 58 facing the magnetic head 57, that is, the fourth magnetic core half 7
A good conductor thin film 94 is formed on the facing surface 77b of the magnetic core portion 77 constituting the magnetic head 9. The thin film 94 is a good conductor and shields leakage magnetic flux from the magnetic gap g1 of the magnetic head 57. Therefore, leakage magnetic flux from the magnetic head 57 facing the magnetic head 58 is reliably shielded by the good conductor thin film 94.

The pair of magnetic heads 57 and 58 configured as described above are arranged close to each other on the same head base 56 with the thin films 93 and 94 of good conductors facing each other as opposing surfaces. This is a composite magnetic head called azimuth. These magnetic heads 57, 58
are provided with a step D approximately equal to the track pitch P on the magnetic tape 89 shown in FIG. 10 recorded by these magnetic heads 57 and 58 in the track pitch direction shown by arrow Y in FIG. Note that the step D here refers to the distance between the ends of the magnetic gaps g1 and g2 of the respective magnetic heads 57 and 58 in the track pitch direction on the head base 56 side in the track width direction.

That is, by disposing one of the magnetic heads 57 on the head base 56 on a spacer 90 having the same thickness as the step D, this magnetic head 5
The distance between the ends of the magnetic gap g1 of No. 7 and the magnetic gap g2 of the magnetic head 58 provided directly on the head base 56 in the track width direction is equal to the step D. Therefore, the magnetic gap g1 of the magnetic head 57 disposed on the spacer 90 is disposed with a step D on the head base 56 side with respect to the magnetic gap g2 of the magnetic head 58 disposed directly on the head base 56. It turns out.

Since the track pitch P on the magnetic tape 89 is set to be 10 μm or less, the step D is set to 10 μm or less in accordance with this. In this embodiment, since the track pitch P is 5 μm, the step difference D
was set to 5 μm in accordance with this. Therefore, the thickness of the spacer 90 was also set to 5 μm.

Furthermore, these magnetic heads 57, 5
8 is provided with a step GL equal to the inter-track step d on the magnetic tape 89 in the head running direction shown by arrow X in FIG. Note that the inter-track level difference d referred to here is
It refers to the distance between the ends of the recording area of each recording track 91, 92 in the head running direction. The step GL is the magnetic gap g1 of each magnetic head 57, 58 in the head running direction.
, g2, the distance between the centers of the track widths Tw1 and Tw2.

The step GL here is selected from the viewpoint of ensuring a recording area for image signals, and is set to, for example, 500 μm or less. If the step GL is 500 μm or more, the image signal area becomes narrow, which is disadvantageous for long-term reproduction. On the other hand, if they are too close, the core thickness of the opposing magnetic core portions 62 and 77 will become thinner, and the head efficiency will decrease due to a decrease in the core cross-sectional area. Therefore, in this example, the step GL is set to 200 μm.

In the composite magnetic head constructed in this manner, the head base 56 is attached to the drum each time it rotates. Then, the rotating drum is rotated and scanned,
A recording pattern as shown in FIG. 10 is formed by the composite magnetic head on the magnetic tape 89 that is relatively transported along the circumferential surface of the rotating drum. At this time, the amount of transport of the magnetic tape 89 per unit time and the number of rotations of the magnetic head are adjusted so that the level difference GL between the magnetic heads 57 and 58 in the head running direction is equal to the level difference d between tracks on the magnetic tape 89. determined.

Recording tracks 91 and 92 on the magnetic tape 89 recorded by the composite magnetic head have a step difference GL in the head running direction of the pair of magnetic heads 57 and 58.
will be recorded with a step difference d equal to . Therefore, each of the magnetic heads 57, 58 reaches the end of the image area 91a, 92a or the audio area 91b, 92b of the respective recording track 91, 92 at the same time. As a result, when performing after-recording in which audio signals are recorded later, after-recording of each signal can be performed satisfactorily without affecting other signals. Furthermore, two magnetic heads 57 integrated on the same head base 56,
Since recording and playback are performed simultaneously using 58, the tape width is 8 m.
Recording density 1.25 for magnetic tape 89 below m
Even when recording and reproducing at μm2/bit or more, it is possible to record and reproduce digital image signals for a long time without increasing the bit error rate due to abnormal track patterns.

For example, two magnetic heads having different azimuth angles are arranged on a rotating drum 180 degrees opposite each other,
Similarly, at a recording density of 1.25μm2/bit or more, 8
When recording and reproducing on a magnetic tape 89 with a width of mm, due to the eccentricity of the rotating drum, tracks recorded by a preceding magnetic head are recorded by a subsequent magnetic head disposed 180 degrees opposite to each other. An abnormal track pattern occurs in which the tracks partially overlap. For this reason,
Part of the signal recorded by the preceding magnetic head is erased, resulting in insufficient reproduction output and a very high bit error rate. However, according to the magnetic head of this embodiment, since the two magnetic heads 57 and 58 are arranged on the same head base 56, even if there is eccentricity of the rotating drum, the magnetic heads 57 and 58
Both recording tracks 91 and 92 recorded in 8 are tilted in the same direction, and do not overlap with the other recording track. Therefore, sufficient playback output can be obtained,
Bit error rate does not become high.

Here, when actually recording and reproducing a signal with a wavelength of 0.3 μm on a magnetic tape with a tape width of 8 mm using the composite magnetic head of this embodiment in the standard mode (SP) with a track pitch of 10 μm, the recording The time was 3 hours. Similarly, when recording and reproduction was performed in double speed mode (LP) with a track pitch of 5 μm, the recording time was 6 hours.

Also, at this time, each magnetic head 57, 58
When we measured the mutual interference (crosstalk) of
As shown by the median line A, it can be seen that mutual interference is extremely reduced. On the other hand, the good conductor thin films 93, 94
It can be seen that the mutual interference is large in the case where the radiator is not provided (indicated by the middle line B in FIG. 11). Note that FIG. 11 shows data when Cu thin films with a film thickness of 10 μm are used as the good conductor thin films 93 and 94.

As described above, in the magnetic head to which this embodiment is applied, the good conductor thin films 93 and 94 are formed on the opposing surfaces of both the magnetic heads 57 and 58. A similar effect can be obtained by providing a good conductor thin film 93. Further, in order to more reliably shield leakage magnetic flux, a figure-eight coil may be wound around these magnetic heads 57 and 58.

[0068]

Effects of the Invention As is clear from the above description, according to the composite magnetic head of the present invention, a pair of magnetic heads disposed close to each other opposite to each other in the head running direction has one magnetic head on the opposing surface of the other magnetic head. Since a good conductor thin film is provided to shield magnetic flux leakage from the magnetic gap of the magnetic head, leakage magnetic flux from the other magnetic head can be reliably shielded by the good conductor thin film. Therefore, mutual interference between recording and reproduction signals of these magnetic heads can be reduced, and good recording and reproduction can be performed.

Furthermore, according to the composite magnetic head of the present invention, since two magnetic heads are arranged on the same head base, even if there is eccentricity of the rotating drum, etc., the recording recorded by these magnetic heads will not be affected. Since the tracks are both tilted in the same direction, there is no overlap with the other recording track, sufficient reproduction output is obtained, and the bit error rate does not become high.

Furthermore, according to the present invention, a method of compressing the amount of recorded information with little reproduction distortion is adopted, and recording and reproduction are simultaneously performed using a pair of magnetic heads provided on the same head base. Even when recording and reproducing on a narrow magnetic tape with a track width of 10 μm or less and a short wavelength of 0.5 μm with a high recording density of 1.25 μm2/bit or more and a tape width of 8 μm or less, digital images can be recorded with a low bit error rate. It becomes possible to record and play back signals for a long time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the recording side of a signal processing unit that compresses digital image information with little reproduction distortion.

FIG. 2 is a block diagram showing the configuration of the reproduction side of a signal processing unit that compresses digital image information with little reproduction distortion.

FIG. 3 is a diagram illustrating an example of blocks for block encoding.

FIG. 4 is a diagram used to explain subsampling and sublines.

FIG. 5 is a block diagram of an example of a block encoding circuit.

FIG. 6 is a block diagram schematically showing an example of a channel encoder.

FIG. 7 is a block diagram schematically showing an example of a channel decoder.

FIG. 8 is an enlarged front view of the main parts of a composite magnetic head to which the present invention is applied, seen from the opposing surface side.

FIG. 9 is a side view of a composite magnetic head to which the present invention is applied.

FIG. 10 is a diagram showing a tape format of a magnetic tape on which digital image information and audio signals are recorded by a composite magnetic head to which the present invention is applied.

FIG. 11 is a characteristic diagram showing mutual interference when recording and reproducing information is performed on a magnetic tape using a composite magnetic head to which the present invention is applied.

FIG. 12 is an enlarged front view of the main parts of a conventional composite magnetic head seen from the opposing surface side.

FIG. 13 is a diagram showing how a conventional composite magnetic head records and reproduces information on a magnetic tape.

[Explanation of symbols]

57, 58...Magnetic head 61...First magnetic core half 64...Second magnetic core half 76...Third magnetic core half 79...Fourth magnetic core Half body 60, 63, 75, 78...Ferromagnetic metal thin film 93, 9
4...Good conductor thin film

Claims (1)

[Claims] Claims: 1. A composite magnetic head in which a pair of magnetic heads having magnetic gaps having different azimuth angles are disposed close to each other and facing each other in the head running direction, wherein A composite magnetic head characterized in that at least one of the magnetic heads is formed with a good conductor thin film that shields leakage magnetic flux from the magnetic gap of the other magnetic head.