JPH05234056A - Magnetic recording and reproducing device - Google Patents

Abstract

(57) [Summary] [Object] To provide a magnetic recording / reproducing apparatus capable of high-density recording and capable of obtaining high reproduction output. [Structure] As the magnetic recording medium, a magnetic recording medium having a CoPtBO-based metal magnetic thin film as a magnetic layer is used. here,
When the CoPtBO-based metal magnetic thin film is formed, by setting the oxygen introduction amount to 1 to 10 SCCM, more preferably 5 to 10 SCCM, a high reproduction output can be obtained. Further, if the oxygen introduction amount is 1 to 4 SCCM, D ₅₀ becomes large,
High density and high reproduction output can be obtained. Recording and reproduction are performed on such a magnetic recording medium by using a ring-type magnetic head. The gap length of the ring type magnetic head is 0.2 to 0.
It is 6 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus using a magnetic recording medium having a CoPtBO-based metal magnetic thin film as a magnetic layer.

[0002]

2. Description of the Related Art In the field of information recording, higher recording density and higher recording capacity are required, and so-called metal thin film type magnetic recording media are used in place of conventional coating type magnetic recording media. It is like this. A CoNi-based metal magnetic thin film is used as the magnetic layer of the metal thin film type magnetic recording medium.

However, the CoNi-based metal magnetic thin film has a limit as a material itself in terms of coercive force, saturation magnetization, magnetic anisotropy, etc. Under such circumstances, the applicant of the present invention discloses Japanese Patent Application Laid-Open No. 2-74012. The publication proposes a CoPtBO-based metal magnetic thin film as a new magnetic thin film. A magnetic recording medium having the CoPtBO-based metal magnetic thin film as a magnetic layer has a large coercive force and saturation magnetization, and has excellent magnetic characteristics, so that high recording density is expected.

[0004]

However, the above-mentioned magnetic recording medium using the CoPtBO-based metal magnetic thin film as the magnetic layer is still in the development stage, and its study on the recording / reproducing characteristics cannot be said to be sufficient. Therefore, the present invention is
It was proposed in view of such circumstances, and CoPt
By clarifying the recording / reproducing characteristics in a magnetic recording medium using a BO-based metal magnetic thin film as a magnetic layer, high density recording is possible,
It is an object of the present invention to provide a magnetic recording / reproducing device capable of obtaining a high reproduction output.

[0005]

Means for Solving the Problems As a result of intensive investigations by the present inventors, it was found that CoPtB cannot be achieved.
In a magnetic recording medium having an O-based metal magnetic thin film as a magnetic layer, the magnetic characteristics change greatly with the amount of oxygen introduced during film formation, and in recording / reproducing with a ring-type magnetic head, the coercive force in the in-plane direction The present inventors have completed the present invention by finding that the reproduction output becomes large with the maximum amount of oxygen introduced, and that the coercive force in the perpendicular direction should be focused on when performing high density recording.

That is, the magnetic recording / reproducing apparatus of the present invention uses a ring type magnetic head having a gap length of 0.2 to 0.6 μm, is formed with an oxygen introduction amount of 1 to 10 SCCM, and has a coercive force of 1000 in the in-plane direction. Recording and reproduction are performed on a magnetic recording medium having a CoPtBO-based metal magnetic thin film of Oersted or higher as a magnetic layer.

The magnetic recording medium used in the present invention is a magnetic recording medium having a CoPtBO-based metal magnetic thin film formed as a magnetic layer. Here, the CoPtBO-based metal magnetic thin film is made of a magnetic material represented by the following composition formula. (Co _a Pt _b B _c ) _100-x O _x However, in the formula, a, b, c and x represent the composition in atomic%, and a + b + c = 100, 0 ≦ b ≦ 50, 0.1 ≦
c ≦ 30 and 0 <x ≦ 15.

In the CoPtBO-based metal magnetic thin film, the coercive force in the in-plane direction is increased by selecting the amount of oxygen introduced at the time of film formation, and the reproduction output is increased when recording / reproducing by the ring type magnetic head. .. For example, CoPt
The amount of oxygen introduced when the BO-based metal magnetic thin film is formed is 1 to 1
If it is 0 SCCM (oxygen partial pressure 30 to 300 μTorr), the oxygen content in the film will be about 2 to 15 atomic%, and the coercive force in the in-plane direction will be 1000 (Oe) or more, and standardized reproduction at 2 kFRPI Output is 100 nV _OP (μm · turn · m
/ S) or higher. In particular, the amount of oxygen introduced is 5
When it is set to -10 SCCM, the coercive force in the in-plane direction is further enhanced, and high reproduction output can be realized.

If the amount of oxygen introduced when forming the CoPtBO-based metal magnetic thin film is 1 to 4 SCCM, the so-called half-value magnetization reversal density D ₅₀ (recording density at which the reproduction output becomes 1/2) becomes large. Since the linear recording density can be increased, it is advantageous for high density recording.

The above-mentioned effect is great when the gap length of the ring type magnetic head used for recording and reproducing is large, and therefore when recording and reproducing on the magnetic recording medium of the present invention, the gap length is 0.2 to. It is preferable to use a ring type magnetic head of 0.6 μm. The gap length is 0.2
If it is less than μm, sufficient recording cannot be performed. On the contrary, if the gap length exceeds 0.6 μm, high density recording becomes difficult.

[0011]

In the CoPtBO-based metal magnetic thin film, the magnetic characteristics greatly change depending on the amount of oxygen introduced during film formation, and when the amount of oxygen introduced is within the range of 1 to 10 SCCM, especially 5 to 10 SCCM, the in-plane direction The coercive force has a large value, and a high reproduction output is achieved when recording / reproducing is performed using a ring type magnetic head having a gap length of 0.2 to 0.6 μm.

Further, when the amount of oxygen introduced is 1 to 4 SCCM, the half-value magnetization reversal density D ₅₀ is increased, and the linear recording density is increased. Therefore, high density recording can be achieved even when recording / reproducing is performed by the ring type magnetic head having a relatively wide gap length (0.2 to 0.6 μm) as described above.

[0013]

EXAMPLES Specific examples to which the present invention is applied will be described in detail below based on experimental results. Example 1 First, a high frequency magnetron sputtering apparatus was used to form a CoPtBO-based metal magnetic thin film on a non-magnetic support. The sputtering conditions are as follows. <Sputtering conditions> Target: Co ₇₁ Pt ₂₂ B ₇ (numerical values represent atomic%) Substrate: Tempered glass power: 300 W Total pressure: 10 mTorr Substrate temperature: Water-cooled target-substrate distance: 80 mm Background pressure: 1.2 × 10 ^-6 Torr

At the time of sputtering, a mixed gas of oxygen gas and argon gas was used as a sputtering gas, and the total flow rate of this sputtering gas was 100 SCCM. Then, the introduction amount of oxygen gas was controlled by changing the mixing ratio of oxygen gas and argon gas while adjusting the total pressure of the sputtering atmosphere to be 10 mTorr.

FIG. 1 shows changes in magnetic characteristics (coercive force) with respect to the amount of introduced oxygen. From Fig. 1, the vertical coercive force Hc _V
And in-plane direction of the coercive force Hc _H, behave differently with respect to the introduction amount of oxygen, the coercive force Hc _H-plane direction, in the region of introduction oxygen amount 1~10SCCM, 1000 (Oe) or more higher The value was shown. In particular, a high coercive force Hc _H is obtained and the oxygen introduction amount is 7 SCCM in the introduced oxygen amount range of 5 to 10 SCCM.
At that time, the maximum value of about 2100 (Oe) was taken. On the other hand, the coercive force Hc _V in the vertical direction was maximum when the oxygen introduction amount was 4 SCCM, and the value was about 3800 (Oe).

Next, a so-called contact type electromagnetic conversion characteristic measuring device for a stretch disk was modified for a hard disk and the electromagnetic conversion characteristics were measured. The magnetic head used for the measurement is a MIG (metal in gap) type magnetic head, and the gap lengths are 0.15 μm and 0.35 μm.
There are two types, m. The specifications of the magnetic head used are as follows.

<Magnetic Head A> Type: MIG type magnetic head Magnetic film: Fe-Ga-Si-Ru (saturation magnetic flux density 14.5 kG) Track width: 30 μm Gap length: 0.15 μm Number of windings: 20 turns

<Magnetic Head B> Type: MIG type magnetic head Magnetic film: Fe-Ga-Si-Ru (saturation magnetic flux density 12 kG) Track width: 25 μm gap length: 0.35 μm Number of windings: 20 turns

FIG. 2 shows the normalized output (2 kFRPI) with respect to the amount of oxygen introduced when recording and reproducing using each magnetic head.
Indicates. The standardized output is a reproduction output standardized by the track width, the number of turns, and the relative speed. Figure 2
A high standardized output is obtained when a magnetic head B having a gap length of 0.35 μm is used. Especially, when recording / reproducing on a magnetic recording medium with an oxygen introduction amount of 7 SCCM, about 190 nV _OP (μm・ Turn ・ m / s), a very large standardized output can be obtained.

Thus, when the magnetic head B having the gap length of 0.35 μm is used, the coercive force Hc in the in-plane direction is obtained.
_The normalized output also increased with an increase in _H , and the normalized output also became the maximum in that the coercive force Hc _{H in} the in-plane direction became the maximum.
Therefore, as described above, the amount of oxygen introduced during the film formation of the CoPtBO-based metal magnetic thin film is 1 to 10 SCCM, especially 5 to 10 SCCM.
It has been found that the use of the SCCM enables high-density recording even with the magnetic head B having a relatively wide gap length.

Magnetic recording suitable for high density recording
The magnetic characteristics of the medium were examined. Example 2 As in Example 1 above, the spa is changed while changing the amount of oxygen introduced.
The CoPtBO-based gold on the non-magnetic support
A metal magnetic thin film was formed. As the sputtering gas,
Pure argon gas and argon gas containing 10% oxygen gas
And the total flow rate of this sputter gas is 100
SCCM.

Then, the half-value magnetization reversal density D ₅₀ of the magnetic tape having the CoPtBO-based metal magnetic thin film as a magnetic layer was measured. The result is shown in FIG. In addition, the magnetic head used for the measurement is M for a video tape recorder (VTR).
It is an IG (metal-in-gap) type magnetic head,
There are two types of gap lengths, 0.15 μm and 0.35 μm.

As shown in FIG. 3, whichever magnetic head was used, the smaller the amount of oxygen introduced, the larger the half-value magnetization reversal density D _{50 and} the magnetic head having a gap length of 0.35 μm. Shows a high value of almost 100 kFRPI in the range where the oxygen introduction amount is 4 SCCM or less. This corresponds to the rising portion of the vertical coercive force Hc _V in FIG. 1, and corresponds to the state where the vertical anisotropy is large.

On the other hand, in the range where the amount of oxygen introduced exceeds 4 SCCM, when the magnetic head having the gap length of 0.35 μm is used, the half-value magnetization reversal density D ₅₀ is rapidly reduced. This range corresponds to the region where the in-plane coercive force Hc _H in FIG. 1 reaches a peak. From this fact, the amount of oxygen introduced during film formation of the CoPtBO-based metal magnetic thin film was 1 to 4 SCCM (0.013 P in oxygen partial pressure).
By adopting a), even when a magnetic head having a relatively wide gap length is used, a large half-value magnetization reversal density D ₅₀ can be obtained, which is an extremely high density compared to the case where a magnetic head having a narrow gap length is used. It turns out that it is possible to make a record.

The magnetic recording / reproducing apparatus described above can obtain a very high standardized output as described above, and is therefore preferably applied to a digital VTR. Therefore, the configuration of a suitable digital VTR will be described by applying this embodiment.

As a digital VTR for digitizing a color video signal and recording it on a recording medium such as a magnetic tape, a D1 format component type digital VTR and a D2 format composite type digital VTR have been put to practical use.

The former D1 format digital VTR
Is 1 for the luminance signal and the first and second color difference signals.
After A / D conversion at a sampling frequency of 3.5 MHz and 6.75 MHz, a predetermined signal processing is performed and recording is performed on a magnetic tape. Since the sampling frequency of these component components is 4: 2: 2. 4: 2:
It is also called two methods.

On the other hand, in the latter D2 format digital VTR, the composite color video signal is sampled with a signal having a frequency four times the frequency of the color subcarrier signal, A / D converted, and subjected to predetermined signal processing. , I record it on a magnetic tape.

In any case, these digital VTs are
Since R is designed on the premise that both are used for broadcasting stations, image quality is given the highest priority, and a digital color video signal in which one sample is A / D converted into, for example, 8 bits is substantially compressed. It is designed to record without doing anything. Therefore, for example, a D1 format digital VTR can obtain a reproduction time of at most about 1.5 hours even if a large cassette tape is used, which is unsuitable for use as a general domestic VTR.

Therefore, here, for example, a signal having a shortest wavelength of 0.5 μm is recorded with respect to a track width of 5 μm, a recording density of 1.25 μm ² / bit is realized, and reproduction distortion of recorded information is reduced. This method is also applied to a digital VTR capable of recording / reproducing for a long time even if a magnetic tape having a tape width of 8 mm or less is used by using a method of compressing in any form.

The configuration of this digital VTR will be described below.

A. Signal Processing Unit First, the signal processing unit of the digital VTR will be described. FIG. 4 shows the entire structure on the recording side.
Digital luminance signals Y and digital color difference signals U and V formed from, for example, three primary color signals R, G and B from a color video camera are supplied to input terminals 1U and 1V, respectively. 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, each sampling frequency is 1
3.5MHz and 6.75MHz, and these 1
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 about 216 Mbps. The data amount of the blanking time is removed from this signal, and the data amount is compressed to about 167 Mbps by the effective information extraction circuit 2 that extracts only the information of the effective area.

Then, 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 thereof. As the frequency conversion circuit 3, for example, a thinning filter is used so that aliasing distortion does not occur. The output signal of the frequency conversion circuit 3 is supplied to the blocking circuit 5, and the order of the luminance data is converted into the order of blocks. The block forming circuit 5 is provided for the block encoding circuit 8 provided in the subsequent stage.

FIG. 6 shows the structure of a block as a coding unit. This example is a three-dimensional block, and for example, by dividing a screen across two frames, a large number of unit blocks of (4 lines × 4 pixels × 2 frames) are formed as shown in FIG. In addition, in FIG. 6, a solid line indicates an odd field line, and a broken line indicates an even field line.

Of the outputs of the effective information extraction circuit 2,
The two color difference signals U and V are supplied to the sub-sampling and sub-line circuit 4, and after the sampling frequencies are respectively converted from 6.75 MHz to half thereof, the two digital color difference signals are selected line by line from each other, Combined with the data. Therefore, a line-sequential digital color difference signal is obtained from the sub-sampling and sub-line circuit 4. FIG. 7 shows the pixel configuration of the signal subsampled and sublined by the subsampling and subline circuit 4. 7 in FIG.
Indicates a sub-sampling pixel of the first color difference signal U, and Δ
Indicates the sampling pixel of the second dye signal V, and x indicates the position of the pixel thinned by the sub-sample.

The line-sequential output signal from the sub-sampling and sub-line circuit 4 is supplied to the blocking circuit 6. In the blocking circuit 6, one blocking circuit 5
Similarly, the color difference data in the scanning order of the television signal is converted into the data in the block order. Like the one blocking circuit 5, the blocking circuit 6 converts the color difference data into a block structure of (4 lines × 4 pixels × 2 frames). The output signals of the blocking circuit 5 and the blocking circuit 6 are supplied to the synthesizing circuit 7.

In the synthesizing circuit 7, the luminance signal and chrominance signal converted in the order of blocks are converted into 1-channel data, and the output signal of the synthesizing circuit 7 is supplied to the block coding circuit 8. As the block encoding circuit 8, an encoding circuit (referred to as ADRC) adapted to the dynamic range of each block and a DCT (Dis) will be described later.
A create cosine transform circuit or the like can be applied. The output signal from the block encoding circuit 8 is further supplied to the framing circuit 9 and converted into frame structure data. In the framing circuit 9, the pixel system clock and the recording system clock are changed.

Next, the output signal of the framing circuit 9 is supplied to the error correction code parity generation circuit 10 to generate the error correction code parity. The output signal of the parity generation circuit 10 is supplied to the channel encoder 11, and channel coding is performed so as to reduce the low frequency part of the recording data. Channel encoder 11
Output signal of the pair of magnetic heads 13 via recording amplifiers 12A and 12B and a rotary transformer (not shown).
It is supplied to A and 13B and recorded on the magnetic tape. The audio signal and the video signal are separately compression-coded and supplied to the channel encoder 11.

By the above-mentioned signal processing, the input data amount 216 Mbps is reduced to about 167 Mbps by extracting only the effective scanning period, and further it is reduced to 84 Mbps by the frequency conversion, the sub-sample and the sub-line. This data is compressed and encoded by the block encoding circuit 8 to be compressed to about 25 Mbps,
By adding additional information such as parity and audio signal after that, the recording data amount becomes 31.56 Mbps.

Next, the structure on the reproducing side will be described with reference to FIG. At the time of reproduction, as shown in FIG. 5, reproduction data from the magnetic heads 13A and 13B is first supplied to the channel decoder 15 via the rotary transformer and the reproduction amplifiers 14A and 14B. Channel decoder 15
At, the channel coding is demodulated, and the output signal of the channel decoder 15 is supplied to the TBC circuit (time base correction circuit) 16. In this TBC circuit 16, the time-axis fluctuation component of the reproduction signal is removed. The reproduction data from the TBC circuit 16 is supplied to the ECC circuit 17,
Error correction using the error correction code and error correction are performed. The output signal of the ECC circuit 17 is supplied to the frame decomposition circuit 18.

The frame decomposition circuit 18 separates each component of the block coded data from each other, and
The clock of the recording system is changed to the clock of the pixel system. The respective data separated by the frame decomposing circuit 18 are supplied to the block decoding circuit 19, the restored data corresponding to the original data is decoded for each block, and the decoding data is supplied to the distribution circuit 20. The 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 the block decomposition circuits 21 and 22, respectively. The block decomposing circuits 21 and 22 convert the decoding data in the order of blocks into the order of raster scanning, contrary to the blocking circuits 5 and 6 on the transmission side.

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

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

B. Block Coding As the block coding circuit 8 in FIG.
(Adaptive Dynamic Range Co
ding) encoder is used. The ADRC encoder detects the maximum value MAX and the minimum value MIN of a plurality of pixel data included in each block, and detects the maximum value MA.
The dynamic range DR of the block is detected from X and the minimum value MIN, the coding adapted to this dynamic range DR is performed, and the requantization is performed with the number of bits smaller than the number of bits of the original pixel data. As another example of the block encoding circuit 8, pixel data of each block is converted into DCT (Discrete Cosine Tran).
After sform), the coefficient data obtained by this DCT may be quantized, and the quantized data may be run-length Huffman encoded and compression-encoded.

Here, an example of an encoder that uses an ADRC encoder and in which image quality does not deteriorate even when multi-dubbing is performed will be described with reference to FIG. In FIG. 8, for example, a digital video signal (or digital color difference signal) in which one sample is quantized into 8 bits is input to the input terminal 27 from the synthesizing circuit 7 in FIG. Input terminal 2
Blocked data from 7 is maximum and minimum value detection circuit 2
9 and the delay circuit 30. The maximum value / minimum value detection circuit 29 determines the minimum value MIN and the maximum value MAX for each block.
To detect. From the delay circuit 30, the input data is delayed for the time required to detect the maximum value and the minimum value.
The pixel data from the delay circuit 30 is supplied to the comparison circuit 31 and the comparison circuit 32.

The maximum value MAX from the maximum / minimum value detection circuit 29 is supplied to the subtraction circuit 33, and the minimum value MIN is supplied to the addition circuit 34. The subtractor circuit 33 and the adder circuit 34 are supplied from the bit shift circuit 35 with a value of one quantization step width (Δ = 1 / 16DR) when non-edge matching quantization is performed with a fixed length of 4 bits. 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). The threshold values from the subtraction circuit 33 and the addition circuit 34 are supplied to the comparison circuits 31 and 32, respectively. The value Δ defining this threshold is not limited to the quantization step width and may be a fixed value corresponding to the noise level.

The output signal of the comparison circuit 31 is the AND gate 3
6 and the output signal of the comparison circuit 32 is supplied to the AND gate 37. The 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 has the pixel data of the input data included in the maximum level range of (MAX to MAX-Δ). Is extracted. On the other hand, the output signal of the comparison circuit 32 becomes high level when the input data is smaller than the threshold value. Therefore, the output terminal of the AND gate 37 is (MIN to MIN).
The pixel data of the input data included in the minimum level range of + Δ) is extracted.

The output signal of the AND gate 36 is supplied to the averaging circuit 38, and the output signal of the AND gate 37 is supplied to the averaging circuit 39. These averaging circuits 38, 39
Calculates the average value for each block, and the reset signal of the block period from the terminal 40 is averaged by the averaging circuits 38, 39.
Is being supplied to. From the averaging circuit 38, (MAX ~
The average value MAX ′ of the pixel data belonging to the maximum level range of (MAX−Δ) is obtained, and the averaging circuit 39 outputs (MIN).
The average value MIN ′ of the pixel data belonging to the minimum level range of ˜MIN + Δ) is obtained. The subtraction circuit 41 subtracts the average value MIN ′ from the average value MAX ′.
From the dynamic range DR '.

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 to form the data PDI after removal of the minimum value. .. The data PDI and the modified dynamic range DR ′ are used by the quantization circuit 44.
Is supplied to. In this embodiment, the number of bits n assigned to quantization is 0 bit (code signal is not transferred),
It is a variable length ADRC that is any one of 1 bit, 2 bits, 3 bits, and 4 bits, and is subjected to edge matching quantization. The allocated bit number n is determined for each block in the bit number determination circuit 45, and the data of the bit number n is supplied to the quantization circuit 44.

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

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

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

Threshold value T from buffering circuit 46
1 to T4 are supplied to the comparison circuit 47, and the dynamic range DR ′ through the delay circuit 48 is supplied to the comparison circuit 47. The delay circuit 48 delays DR ′ by the time required for the buffering circuit 46 to determine the threshold set. In the comparison circuit 47, the dynamic range DR ′ of the block is compared with each threshold value, the comparison output is supplied to the bit number determination circuit 45, and the allocated bit number n of the block is determined. In the quantizing circuit 44, the data PDI after the minimum value removal via the delay circuit 49 is converted into the code signal DT by the edge matching quantization using the dynamic range DR ′ and the allocated bit number n. The quantization circuit 44 is composed of, for example, a ROM.

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

C. Channel Encoder and Channel Decoder Next, the channel encoder 11 and the channel decoder 15 of FIG. 4 will be described. As shown in FIG. 9, the channel encoder 11 is an adaptive scramble circuit to which the output of the parity generation circuit 10 is supplied, and a plurality of M-sequence scramble circuits 51 are prepared. The M-sequence is selected so that an output having a small number of components and DC components can be obtained. The precoder 52 for the partial response class 4 detection method performs arithmetic processing of 1 / 1-D ² (D is a unit delay circuit). The output of the precoder 52 is passed through the recording amplifiers 12A and 13A to the magnetic head 1
Recording and reproduction are performed by 3A and 13B, and reproduction output is amplified by reproduction amplifiers 14A and 14B.

On the other hand, in the channel decoder 15, as shown in FIG. 10, the arithmetic processing circuit 53 on the reproducing side of the partial response class 4 performs 1 + D arithmetic on the outputs of the reproducing amplifiers 14A and 14B. Further, in the so-called Viterbi decoding circuit 54, noise-resistant data decoding is performed on the output of the calculation processing circuit 53 by calculation using the correlation and the accuracy of the data. The output of the Viterbi decoding circuit 54 is supplied to the descrambling circuit 55, the data rearranged by the scrambling process on the recording side is returned to the original series, and the original data is restored. With the Viterbi decoding circuit 54 used in this embodiment, the reproduction C / N conversion is improved by 3 dB as compared with the case of performing the decoding for each bit.

D. The traveling magnetic heads 13A and 13B are attached to the drum 76 in an integrated structure as shown in FIG. A magnetic tape (not shown) is obliquely wound around the peripheral surface of the drum 76 at a winding angle slightly larger than 180 ° or slightly smaller than 180 °.
A and the magnetic head 13B are configured to scan the magnetic tape at the same time.

The directions of the gaps of the magnetic head 13A and the magnetic head 13B are inclined in opposite directions (for example, the magnetic head 13A is inclined + 20 ° with respect to the track width direction, and the magnetic head 13B is inclined −20 °). Are set so that the amount of crosstalk between adjacent tracks is reduced by so-called azimuth loss during reproduction.

12 and 13 show magnetic heads 13A,
This shows a more specific structure when 13B is an integral structure (so-called double azimuth head). For example, the magnetic head 13 integral with the upper drum 76 rotated at a high speed.
A and 13B are attached, and the lower drum 77 is fixed. Here, the winding angle θ of the magnetic tape 78 is 16
The drum diameter is 6 ° and the drum diameter φ is 16.5 mm.

Therefore, on the magnetic tape 78, one field of data is divided into five tracks and recorded. With this segment system, the length of the track can be shortened, and the error due to the linearity of the track can be reduced.

As described above, by performing the simultaneous recording with the double azimuth head, the error amount due to the linearity can be reduced as compared with the case where the pair of magnetic heads are arranged at the facing angle of 180 °. In addition, since the head-to-head distance is small, the pairing adjustment can be performed more accurately. Therefore, with such a traveling system, recording / reproducing can be performed on a narrow track.

[0062]

As is apparent from the above description, in the present invention, the optimum conditions for performing recording / reproduction on a magnetic recording medium having a CoPtBO-based metal magnetic thin film as a magnetic layer have been clarified, and high reproduction has been achieved. It is possible to achieve output. That is, by controlling the amount of oxygen introduced into a magnetic recording medium having a CoPtBO-based metal magnetic thin film as a magnetic layer to increase the coercive force in the in-plane direction and selecting the gap length of the magnetic head to be used, 100 nV at 2 kFRPI. _OP
It is possible to obtain a standardized output of (μm · turn · m / s) or more.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between an oxygen introduction amount and a magnetic characteristic (coercive force) in a CoPtBO-based metal magnetic thin film.

FIG. 2 is a characteristic diagram showing a relationship between an oxygen introduction amount and a normalized output (2 kFRPI) in a CoPtBO-based metal magnetic thin film.

FIG. 3 is a characteristic diagram showing the relationship between the amount of oxygen introduced and the half-value magnetization reversal density D _{50 in} a CoPtBO-based metal magnetic thin film.

FIG. 4 is a block diagram showing a configuration of a recording side of a signal processing unit of a digital VTR that compresses and records a digital image signal in a form such that reproduction distortion is small.

FIG. 5 is a block diagram showing a configuration on a reproduction side of a signal processing unit.

FIG. 6 is a schematic diagram showing an example of a block for block coding.

FIG. 7 is a schematic diagram for explaining subsampling and sublines.

FIG. 8 is a block diagram showing an example of a block encoding circuit.

FIG. 9 is a block diagram showing an outline of an example of a channel encoder.

FIG. 10 is a block diagram showing an outline of an example of a channel decoder.

FIG. 11 is a plan view schematically showing an example of the arrangement of magnetic heads.

FIG. 12 is a plan view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

FIG. 13 is a front view showing a configuration example of a rotating drum and a winding state of a magnetic tape.

[Explanation of symbols]

 1Y, 1U, 1V ... Component signal input terminals 5, 6 ... Blocking circuit 8 ... Block coding circuit 11 ... Channel encoder 13A, 13B ... Magnetic head 15 ... Channel decoder 19 ... Block decoding circuit 21, 22 ... Block decomposition circuit

Claims (4)

[Claims] 1. A ring-type magnetic head having a gap length of 0.2 to 0.6 μm is used to form a film with an oxygen introduction amount of 1 to 10 SCCM and a coercive force in the in-plane direction of 1000 C or more.
A magnetic recording / reproducing apparatus for performing recording / reproducing on a magnetic recording medium having an oPtBO-based metal magnetic thin film as a magnetic layer. 2. A CoPtBO-based metal magnetic thin film is composed of (Co _a
Pt _b B _c ) _100-x O _x (where a, b, c, x in the formula
Represents the composition in atomic%, and a + b + c = 10
0, 0 ≦ b ≦ 50, 0.1 ≦ c ≦ 30, and 0 <x ≦ 15. 3. The magnetic recording / reproducing apparatus according to claim 1, having the composition 3. A C film formed with an oxygen introduction amount of 5 to 10 SCCM.
The magnetic recording / reproducing apparatus according to claim 1, wherein recording / reproducing is performed on a magnetic recording medium having an oPtBO-based metal magnetic thin film as a magnetic layer. 4. The magnetic recording / reproducing apparatus according to claim 1, wherein recording / reproducing is performed on a magnetic recording medium having a magnetic layer of a metal magnetic thin film formed with an oxygen introduction amount of 1 to 4 SCCM.