JPH0661121B2 - Magnetic recording / reproducing characteristic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a change in the spacing amount between a magnetic head and a magnetic recording medium in a magnetic recording / reproducing apparatus such as a VTR (video tape recorder) or a magnetic disk, and recording. The present invention relates to a magnetic recording / reproducing characteristic measuring device for measuring a deviation amount between a track and a reproducing track.

[Prior Art] FIG. 6 is a block diagram showing a configuration of a magnetic recording / reproducing characteristic measuring apparatus according to the prior application of the present applicant. (1) is a VTR to be measured (hereinafter referred to as “VTR”), (2) Is a rotating drum, (3) is a magnetic tape, (4) is a magnetic head, (5) is a rotary transformer,
(6) and (7) are switches for switching the input / output side of the test signal and reproduction signal input to the VTR (1), (9) is a recording amplifier, and (1)
0) is a variable frequency oscillator, and (11) is an attenuator. At the time of recording, a test signal of a predetermined frequency and a predetermined level is sent to the VTR via the switches (6) and (7) according to the command of the computer (13).
Input to (1) and record on magnetic tape (3). (8) is a reproduction amplifier that amplifies the reproduction signal input from the switches (6) and (7), (21) is a low-pass filter that removes harmonic components of the output signal of the reproduction amplifier (8), and (22) is a filter. A detector that detects the test signal component input from (21) and continuously outputs a detection signal of a level according to the amplitude, (23) samples the input detection signal and converts it to a digital signal A
/ D converter, (24) is a memory for storing digital data output from the A / D converter (23), (13) is a computer for controlling and performing a predetermined operation, and is an oscillator.
The frequency of the test signal in (10) is sequentially switched and the attenuator (1
1) is controlled to record a test signal with the magnetic head (4) at the optimum recording current, the data is read from the memory (24), and the later-described calculation is performed to calculate the spacing amount or the spacing variation amount.

FIG. 7 is a view showing the positional relationship between the magnetic heads (4a) and (4b) of the VTR (1), the magnetic tape (3) and the rotary drum (2), and the arrow (15) indicates that of the rotary drum (2). Direction of rotation, arrow (16)
Indicates the traveling direction of the magnetic tape (3).

The two magnetic heads (4) are placed on top of each other on the rotating drum (2).
The magnetic tape (3) is attached at a position of 0 °, and the magnetic tape (3) is wound around the rotating drum (2) obliquely over a range of slightly over 180 °. Therefore, even if the rotary drum (2) rotates, one or both of the magnetic heads (4) is always in contact with the magnetic tape (3).

Next, the operation will be described. During recording, the oscillator (10) and the attenuator (11) are controlled by the control signal from the computer (13), the test signal f of a predetermined frequency and a predetermined level is input to the recording amplifier (9), and the switch is turned on.
The test signal f is recorded on the magnetic tape (3) by being supplied to the magnetic head (4) through (6), (7) and the rotary transformer (5) and being supplied with the optimum recording current.

At the time of reproduction, the recording signal recorded on the magnetic tape (3) is reproduced by the magnetic head (4), passes through the rotary transformer (5) and the switches (6) and (7), and is reproduced. It is amplified in 8).

The reproduction signal amplified by the reproduction amplifier (8) passes through the filter (21) to remove the harmonic component, and only the fundamental wave component of the test signal f is detected, and the amplitude is continuously detected by the detector (22). , Is sampled by the A / D converter (23), converted into a digital signal, and stored in the memory (24).

Since the magnetic head (4) of the VTR (1) is attached to the rotating drum (2) and is rotating, if the rotating position of the rotating drum (2) is different, the contact between the magnetic head (4) and the tape (3) will occur. The state may change. In such a case, the magnetic head (4
As for the vicinity of the gears a) and (4b), the tape
A minute spacing occurs between (3) and the reproduction output level changes when the spacing amount changes.

The reproduction output in such a case is as shown in, for example, FIG. 8 (a) when viewed from the output of the filter (21), and when viewed at the output of the detector (22), its amplitude value is extracted and It becomes like FIG. 8 (b). The detected signal is sampled by the A / D converter (23) and converted into a digital signal, and sequentially stored in the memory (24) as digital data having the values shown in FIG. 8 (c) together with the position data.

From the digital data stored in the memory (24), the computer (13) detects the points corresponding to the inlet and the outlet of the rotary drum (2) and processes them to obtain the ninth point.
The characteristic of the reproduction output level with respect to the rotational position of the magnetic head (4) as shown in the figure can be obtained.

By performing such measurement for a plurality of test signals selected at appropriate frequency intervals, the rotational positions P ₀ , P ₁ , P ₂ , ... P _n of the magnetic head as shown in FIG. 10 are used as parameters. The frequency characteristic can be obtained, and from this frequency characteristic diagram, the change in the spacing amount with respect to the rotational position P _i of the magnetic head will be described below (Proceedings of the Joint Conference of the Kansai Branch of the Electrical Relations Society in 1986 G14- Two
It is possible to analyze the contact state between the magnetic head and the magnetic tape. That is,
The frequency characteristic of a signal recorded and reproduced on a magnetic recording medium with an optimum recording current is determined by (spacing loss) + (head core loss) + (reproducing gear loss), the Institute of Electronics and Communication Engineers Magnetic Recording Research Group. It is known from the document MR75-28 and the like, and it is considered that the frequency characteristic of the reproduction signal changes depending on the rotational position of the magnetic head, because of the change of the spacing amount. The amount of change ΔS in the spacing amount (hereinafter, referred to as “spacing change amount”) ΔS can be obtained by the following equation (1).

Here, v is the relative velocity [m / S], the frequency [H _z], ΔL _s the amount of change in spacing loss L _s [d
B] and K are proportional constants, and the value of K is about 13 according to the Proceedings 235 of the IEICE General Conference (1985).
It is 0 [dB].

Of the frequency characteristic of a parameter the rotational position of the magnetic head shown in FIG. 10, based on the rotational position P ₀ frequency characteristic and most nearly flat, the rotational position P ₁ of the magnetic head,
FIG. 11 shows the difference between the frequency characteristics of P ₂ , ... P _n . The slope of each characteristic curve at each rotational position P ₁ , P ₂ ... P _n n of the magnetic head in FIG. By substituting for each rotational position P ₁ ,
The spacing change amount ΔS at P ₂ ... P _n can be obtained.

FIG. 12 shows the relative spacing amount when the spacing amount at the rotational position P ₀ of the magnetic head having the smallest spacing amount is 0.

[Problems to be Solved by the Invention] In the conventional magnetic recording / reproducing characteristic measuring apparatus, when the relative spacing amount with respect to the rotational position of the magnetic head is obtained, the reproducing output for each rotational position of the magnetic head is tested at a plurality of different frequencies. Sequential measurement is performed on the signal, and the frequency characteristic for each rotational position is obtained from the measurement result, and the relative spacing amount at each rotational position is obtained from this, so
There was a problem that the measurement time was long.

Further, the spacing amount is not stable and varies a little with each rotation even at the same rotation position. However, in the conventional measuring device, the relative spacing amount is calculated on the assumption that the spacing amount at the same rotation position is constant, so that the accurate spacing variation amount cannot be obtained. Furthermore, in the conventional measuring device, since the recording / reproducing characteristics of the measured object are successively measured for a plurality of frequencies, it is difficult to accurately adjust the relative position of the reproducing output of each frequency. There was a problem that it was difficult to increase the directional resolution.

The present invention has been made in order to solve the above-mentioned problems, and the amount of spacing change at each rotational position of the magnetic head along with the relative spacing amount with respect to the rotational position of the magnetic head in the rotational position direction of the magnetic head. An object of the present invention is to obtain a magnetic recording / reproducing characteristic measuring device capable of measuring with high resolution in a short time.

Further, an object of the present invention is to record a recording track which cannot be measured by a conventional measuring apparatus and a scanning track during reproduction (hereinafter,
It is an object of the present invention to obtain a magnetic recording / reproducing characteristic measuring device capable of measuring a deviation amount from a “reproducing track”).

[Means for Solving the Problems] A magnetic recording / reproducing characteristic measuring apparatus according to the present invention includes a test signal source for generating a composite test signal having a plurality of different frequency components, and a magnetic recording / reproducing apparatus for the composite test signal. Recording means for continuously recording corresponding to a predetermined rotation position of the rotary head in, and reproducing means for continuously reproducing a reproduced signal from the magnetic recording medium of the magnetic recording and reproducing device in which the composite test signal is recorded, Separation means for separating the plurality of components corresponding to the different frequency components from the reproduction signal, and the amplitudes of the components corresponding to the separated frequency components are respectively detected to continuously output a plurality of reproduction output levels. From the level detection means, the reproduction output level output from the level detection means, and the frequency corresponding to the plurality of reproduction output levels. Of the reproduction output level with respect to the frequency of the signal, and a spacing change amount calculating means for calculating a spacing change amount from the change amount of the inclination, a reproduction output level output from the level detecting means, and the plurality of reproduction outputs. A track deviation amount calculating means for calculating the reproduction output level corresponding to the frequency of the reproduction signal of zero from the relationship with the frequency corresponding to the level, and calculating the track deviation amount from the change amount of the reproduction output level. It is equipped with.

[Action]

According to the present invention, a plurality of components corresponding to different frequency components are separated from the reproduction signal continuously reproduced from the recording medium of the magnetic recording / reproducing apparatus in which the composite test signal is recorded, and the separated components are separated. Amplitude of each component is detected individually to continuously detect multiple playback output levels,
From the relationship between the detected reproduction output level and the frequency corresponding to the reproduction output level, the slope of the reproduction output level with respect to the frequency of the reproduction signal and the size of the reproduction output level at which the frequency of the reproduction signal corresponds to zero are obtained. The amount of spacing change and the amount of track deviation can be calculated from the amount of change in the inclination and the amount of change in the level, so that characteristic measurement such as analysis of the contact state between the rotary head and the magnetic recording medium can be performed with high resolution. It can be performed accurately and quickly under

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a block diagram of this embodiment, and the portions denoted by the same reference numerals as in FIG. 6 respectively show the same components. In FIG., (10a), for example an oscillator for generating a sine wave signal _a of 1.5MH _z, (10b) is an oscillator that generates a sine wave test signal _b of example 5.5MH _z, 2 one test signals _{a, b} are It is selected to a frequency not higher harmonic components interfere with each other, in particular _b is selected to the frequency is not an integer multiple of _a.

(11a) and (11b) are attenuators, which are synthesized by the recording amplifier (9) and are connected by the attenuator (11b) so that the component of the test signal _b is applied to the magnetic head (4) at almost the optimum recording current. It is adjusted, the other components of the test signal _a, the test signal _b
Of the attenuator (11
Adjusted according to a). The reason for setting the level of the thus test signal _a, that a sufficient reproduction level can be obtained with a low level ac bias effect due to high test signal _b frequencies, and increasing the recording level of _{a, b}
This is because the reproduction signal level becomes low, the S / N is lowered, and the measurement accuracy is lowered. (21a) is _a bandpass filter for extracting the component of the test signal _a from the reproduction signal input from the reproduction amplifier (8), (21b) is a bandpass filter for extracting the component of the test signal _b , and a detector (22a ) And (22b) are A / D converters that continuously detect the amplitudes of the test signal components input from the bandpass filters (21a) and (21b).
Output to (23a), (23b), A / D converter (23a), (23b)
Each sample the input signal with a synchronized sampling signal, convert it into a digital signal, and store it in the memory (2
4a). (24b) stores the input digital data.

Thus, in this embodiment, two test signals are simultaneously
The playback output for _a and _b is the A / D converter (23
It is obtained at the sampling time intervals of a) and (23b). Therefore, it is possible to measure the frequency characteristic at each sampling time point, that is, at each rotational position obtained by dividing the rotational position of the magnetic head in the rotational direction at sampling time intervals.

In addition to the spacing change amount ΔS described above, a difference between the recording track and the reproduction track due to vibration of the tape is considered as a factor that causes the reproduction output from the magnetic head to fluctuate. ), And the track deviation amount T _WS can be calculated by the following (2)
It can be obtained by a formula.

Here, L _TW is a loss due to track deviation [dB] T _ws is a rate [%] of track deviation, and L _TW can be obtained from frequency characteristics by a calculation described later.

That is, the loss L _S due to the change in the spacing amount is represented as a change in the slope of the frequency characteristic, and the loss L _TW due to the track deviation is represented as a change in the reproduction output level because the slope of the frequency characteristic is the same.

FIG. 2 shows that, in this embodiment, three magnetic heads having different magnetic heads are used.
The detectors (22a) and (22) at the two rotational positions P ₁ , P ₂ , and P ₃
In the figure showing the detection output level of b), A, B, and C respectively show the frequency characteristics at the rotational positions P ₁ , P ₂ , and P ₃ , and from the relationship between the respective frequency characteristics A, B, and C, the spacing is shown. The fluctuation amount ΔS and the track shift amount T _WS can be obtained.

Since the frequency characteristics A and B have almost the same inclination, the spacing amounts at the rotational positions P ₁ and P ₂ are the same, and the rotational position P ₃ is the largest. Further, since the track deviation amount T _WS is obtained as a level difference at the point where the characteristics A, B, and C are extrapolated to the frequency 0, the track deviation amounts T _{WS at} the rotational positions P ₁ and P ₃ are the same. The rotational position P ₂ has the largest deviation. Thus, at each point in time (ie each rotational position)
At the same time, by simultaneously measuring the reproduction output levels at high and low frequencies, it is possible to know the relative spacing amount and the track shift amount at that time.

If the characteristic curves A, B, and C are selected as the measurement data of three times at the same rotational position of the magnetic head, the spacing change amount and the track shift amount at the rotational position can be known, and the number of measurement data is large. Then, the average value and the range of its variation can be obtained.

FIG. 3 shows the average value a of the relative spacing amount with respect to the rotational position of the magnetic head calculated by calculating these data by the computer (13) and the range b of the variation thereof.

Further, FIG. 4 shows the average value a of the track shift amount with respect to the rotational position of the magnetic head and the range b of the variation thereof.

FIG. 5 is a block diagram of another embodiment of the present invention. In the figure, (25a) and (25b) are sample and hold circuits that temporarily hold the detection output values of the detectors (22a) and (22b), and (26) is the sample and hold circuits (25a) and (25b) A switch for inputting the hold value to the A / D converter. From the sample hold circuits (25a) and (25b), the detection signal (22
The detected outputs from a) and (22b), that is, the amplitude values of the high and low test signal components reproduced simultaneously by the magnetic head, are read, converted by the A / D converter (23) into digital data, and stored in the memory ( 24).

According to this embodiment, the A / D converter and the memory are
It can be configured one after another, and the circuit configuration becomes simple.

Although a plurality of frequency components are generated using the oscillator (10a) and the oscillator (10b) in the above embodiment, a plurality of frequency components may be generated by another method such as generating an FM modulated wave by an FM modulator. Frequency components may be generated.

Further, in the above embodiment, the frequency characteristic is measured by using the test signals having two different frequencies, but the frequency characteristic may be measured by using the test signals having three or more different frequencies.

In the above embodiment, the digital signal from the A / D converter is temporarily stored in the memory, and then the calculation of the spacing change amount and the track shift amount is performed by the computer. The spacing change amount and the track shift amount may be obtained by directly calculating the digital signal from the D converter.

In the above embodiment, the output of the detector is converted into a digital signal by the A / D converter and then digitally calculated. However, the calculation may be performed by an analog circuit. In this case, the calculation time is shortened and the circuit configuration is simplified.

Further, in the above embodiment, the spacing change amount and the track shift amount are measured, but only one of the spacing change amount and the track shift amount may be measured.

In the above embodiment, the data stored in the memory is processed by the computer to detect the points corresponding to the inlet and the outlet of the rotary drum. By storing the data in the memory by using the signal itself as a trigger, specific addresses in the memory may correspond to the drum entrance and the exit.

Further, in the above-mentioned embodiment, the filter and the detector are constructed as separate blocks, but since these blocks are the basic constituent elements of the spectrum analyzer, the spectrum analyzer has a frequency span of 0 instead of the block by the filter and the detector. You may use as.

Further, in the above embodiment, the case where the recording / reproducing characteristic of the VTR is measured has been described, but another magnetic recording / reproducing apparatus such as a magnetic disk may be used.

Further, in the above-mentioned embodiment, the magnetic recording / reproducing apparatus for recording on the magnetic medium and the magnetic recording / reproducing apparatus for reproducing the signal from the magnetic medium are the same, but the magnetic recording / reproducing apparatus as the reference is used for recording on the magnetic medium. Recording may be performed and the measurement may be performed by reproducing this magnetic medium by a magnetic recording / reproducing apparatus to be measured. In this case, once recorded on the magnetic medium by the reference magnetic recording / reproducing apparatus,
At the time of measurement, it suffices to reproduce this magnetic medium and there is no need to record it, so the measurement time is shortened. Further, there is an effect that it is possible to measure how much the reproduction track of the magnetic recording / reproducing apparatus to be measured is deviated from the recording track of the reference magnetic recording / reproducing apparatus, that is, the reference track.

As described above, according to the present invention, a composite test signal composed of a plurality of mutually different frequency components is continuously recorded in association with a predetermined rotational position of the rotary head in the magnetic recording / reproducing apparatus. From the reproduction signal continuously reproduced from the recording medium of the magnetic recording / reproducing apparatus in which the composite test signal is recorded, the components corresponding to a plurality of different frequency components are separated, and the amplitudes of the separated respective components are respectively separated. While detecting and continuously detecting multiple playback output levels,
From the relationship between the detected reproduction output level and the frequency corresponding to the reproduction output level, the slope of the reproduction output level with respect to the frequency of the reproduction signal and the size of the reproduction output level at which the frequency of the reproduction signal corresponds to zero are obtained. Since the amount of change in spacing and the amount of track deviation can be calculated from the amount of change in the inclination and the amount of change in the level, the frequency characteristics of frequency components different from each other at each rotational position of the rotary head can be increased. Therefore, it is possible to perform characteristic measurement such as analysis of the contact state between the rotary head and the magnetic recording medium with high resolution, accurately and quickly. .

[Brief description of drawings]

FIG. 1 is a block diagram showing the construction of an embodiment of the present invention,
FIG. 2 is a diagram for explaining the content of the measurement data in this embodiment, and FIG. 3 is a diagram showing the relative spacing amount with respect to the rotational position of the magnetic head measured in this embodiment.
FIG. 5 is a diagram showing a track shift amount, FIG. 5 is a block diagram showing a configuration of another embodiment of the present invention, and FIG. 6 is a block diagram showing a configuration of a recording / reproducing characteristic measuring device according to a prior application of the present invention. FIG. 7 is a diagram showing the positional relationship among the rotating drum of the VTR, the magnetic head and the magnetic tape, and FIG. 8 is a diagram showing the signal waveforms and states of the respective parts of the conventional measuring device shown in FIG. FIG. 9 is a diagram showing an example of measurement of a reproduction output level with respect to a magnetic head rotational position by a conventional measuring device, FIG. 10 is a frequency characteristic diagram in which each rotational position of the magnetic head in the conventional measuring device is used as a parameter, FIG. 10 is a frequency characteristic diagram at each rotational position of the magnetic head based on the data having the most extended frequency characteristic in the measurement example of FIG. 10, and FIG. 12 is a magnetic head and magnetic field with respect to the rotational position of the magnetic head by the conventional measuring device. tape Is a diagram showing an example of measurement of the relative spacing amount. (3) ... Magnetic tape, (4) ... Magnetic head, (6), (7), (26) ...
Switch, (10a), (10b) ... Oscillator, (11a), (11b) ... Attenuator, (13) ... Computer, (21a), (21b) ... Bandpass filter, (22a), (22b) ... Detector , (23), (23a),
(23b) ... A / D converter, (24), (24a), (24b) ... Memory, (25a), (25b) ... Sample and hold circuit. In the drawings, the same reference numerals indicate the same or corresponding portions.

Claims (3)

[Claims] 1. A test signal source for generating a composite test signal composed of a plurality of mutually different frequency components, and the composite test signal is continuously recorded in correspondence with a predetermined rotational position of a rotary head in a magnetic recording / reproducing apparatus. Recording means, reproducing means for continuously reproducing a reproduced signal from the magnetic recording medium of the magnetic recording / reproducing apparatus in which the composite test signal is recorded; and a component corresponding to the plurality of different frequency components from the reproduced signal. Separating means, level detecting means for respectively detecting the amplitudes of the separated components corresponding to the frequency components and continuously outputting a plurality of reproduction output levels, and reproduction output levels outputted from the level detecting means. And the frequency corresponding to the plurality of reproduction output levels, the slope of the reproduction output level with respect to the frequency of the reproduction signal is obtained. From the relationship between the spacing change amount calculating means for calculating the spacing change amount from the charge amount and the reproduction output level output from the level detecting means and the frequencies corresponding to the plurality of reproduction output levels, the frequency of the reproduction signal is zero. A magnetic recording / reproducing characteristic measuring apparatus, comprising: a track deviation amount calculating means for calculating a reproduction output level corresponding to the above, and calculating a track deviation amount from the amount of change in the reproduction output level. 2. In any two frequency components of the frequency components of the composite test signal generated from the test signal source,
2. The magnetic recording / reproducing characteristic measuring device according to claim 1, wherein the frequencies are set so that their frequency relationships do not become integral multiples. 3. The magnetic recording / reproducing characteristic measuring device according to claim 1, wherein the composite test signal is an FM modulated wave signal.