JPS63206903A - Measuring instrument for magnetic recording/ reproducing characteristic - Google Patents

Abstract

PURPOSE:To realize measurement of the deviation value between the recording and reproducing tracks by separating plural test signal components from the signals obtained by reproducing a recording medium that recorded simultaneously plural test signals of different frequencies and detecting continuously the amplitudes of said signal components to measure the frequency characteristics with high resolution in the scanning direction of a magnetic head. CONSTITUTION:The filters 21a and 21b and wave detectors 22a and 22b separate plural test signal components from the reproduced signals and detect simultaneously and continuously the amplitudes of these signal components. As a result, plural recording/reproducing output data of different frequencies are obtained at one time at the same revolving position. Thus the frequency characteristics can be measured in a short time and at the same time no positioning job is required for the measurement data so that the resolution is improved. Then the deviation value can be calculated between the recording and reproducing tracks from those reproduction data.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to changes in the spacing between a magnetic head and a magnetic recording medium in magnetic recording and reproducing devices such as VTRs (video tape recorders) and magnetic disks, and The present invention relates to a magnetic recording/reproduction characteristic measuring device that measures the amount of deviation between a track and a reproduction track.

[Prior Art] FIG. 6 is a block diagram showing the configuration of a magnetic recording and reproducing characteristic measuring device according to the applicant's earlier application, in which (1) shows the configuration of the 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, (θ), (7) is a switch that switches the input Φ output side of the test signal and reproduction signal input to v r R (1), (3) is a recording amplifier, (10) is a variable frequency oscillator, and (11) is an attenuator. During recording, test signals of a predetermined frequency and a predetermined level are switched (8), (7) according to instructions from the computer (13). via V T
It is input to R(1) and recorded on the magnetic tape (3). (8
) is a switch (B).

(7) is a 1f raw amplifier that amplifies the playback signal input from the playback amplifier, (21) is a low-pass filter that removes harmonic components of the output signal of playback amplifier (8), and (22) is a filter (
A detector that detects the test signal component input from (21) and continuously outputs a detected signal with a level corresponding to the amplitude.
3) is an A/D converter that samples the input detection signal and converts it into a digital signal, and (24) is an A/D converter.
A memory stores the digital data input from the converter (23), and (13) is a computer that performs control and predetermined calculations, and sequentially switches the frequency of the test signal of the oscillator (10) and controls the attenuator (11). record the test signal with the magnetic head (4) at the optimum recording current,
The spacing amount or spacing change amount is calculated by reading data from the memory (24) and performing calculations to be described later.

FIG. 7 shows the magnetic head (4a) of the VTR (1),
(4t)), magnetic tape (3) and rotating drum (2)
2 is a diagram showing the positional relationship of
It shows the direction of travel.

The 29/4 magnetic heads (4) are mounted on the rotating drum (2) at positions 180' from each other, and the magnetic tape (3) is wound diagonally around the rotating drum (2) over a range of just over 1800 degrees. It is being Therefore, even when the rotating drum (2) rotates, one or both of the magnetic heads (4) are always in contact with the magnetic tape (3).

Next, the operation will be explained. During recording, the oscillator (10),
and an attenuator (11) are controlled, and a test signal f of a predetermined frequency and a predetermined level is input to the recording amplifier (9) and sent to the magnetic head (4) through the switch (El), (7) and the rotary transformer (5). is applied, and the optimum recording current is applied to the magnetic tape (3) to produce a test signal f.
is recorded.

Also, during reproduction, the recorded signal recorded on the magnetic tape (3) is reproduced by the magnetic head (4), and the rotary transformer (5) and the switches (6), (?
) and is amplified by the reproducing amplifier (8).

The playback signal amplified by the playback amplifier (8) is passed through the filter (2).
1), the harmonic components are removed through the test signal f, and only the fundamental wave component of the test signal f remains.The amplitude of the signal is continuously detected by the wave detector (22), and is sampled by the A/D converter (23) and converted into a digital signal. It is converted into a signal and stored in memory (24
).

The magnetic head (4) of the VTR (1) is a rotating drum (
2) and rotates, so the rotating drum (
If the rotational position of 2) is different, the magnetic head (4) and tape (
3) The contact state may change. In such a case, in the vicinity of the gap between the magnetic heads (4a) and (4b), a minute spacing occurs between the magnetic heads (4a) and (4b) and the tape (3), and when this amount of spacing changes, the reproduction output level changes.

If we look at the reproduced output in such a case as the output of the filter (21), it will be as shown in Figure 8(a), for example, and the output of the detector (21) will be as shown in Fig.
Looking at the output of 2), the amplitude value is extracted and the 8th
This detected signal, as shown in Figure 8(b), is sampled by the A/D converter (23) and converted into a digital signal, and stored in the memory (20) as digital data with the values shown in Figure 8(C). Stored sequentially with data.

From the digital data stored in this memory (24), the computer (I3) detects and processes the locations corresponding to the inlet and outlet of the rotating drum (2), thereby creating a magnetic field as shown in FIG. The characteristics of the reproduction output level with respect to the rotational position of the head (4) can be determined.

By performing such measurements on a plurality of test signals selected at appropriate frequency intervals.

Rotational positions PG and PI of the magnetic head as shown in FIG.
, P2. ...The frequency characteristic with Pn as a parameter can be obtained, and from this frequency characteristic diagram, the change in the amount of spacing with respect to the rotational position ffi P 1 of the magnetic head can be determined using the method described below (1988 Electrical Related It can be obtained as described in G14-2 of the conference proceedings of the Kansai Branch Association of Academic Societies, and it is possible to analyze the contact state between the magnetic head and the magnetic tape.In other words, it is possible to analyze the contact state between the magnetic head and the magnetic tape.In other words, when recording is performed on the magnetic recording medium at the optimum recording current, and when the reproduction The frequency characteristics of the reproduced signal are determined by (spacing loss) + (head core loss) + (reproduction gap loss).

This is known from the Institute of Electronics and Communication Engineers' Magnetic Recording Study Group Material MR75-28, and it is thought that the frequency characteristics of the reproduced signal change depending on the rotational position of the magnetic head due to the change in the amount of spacing.

The amount of change in the spacing amount (hereinafter referred to as the "amount of spacing change") ΔS can be determined by the following equation (1).

Here, C and V are relative speeds [m/S], and f is frequency [H2]
, ΔLS is a proportional constant for the amount of change [dB] in the spacing loss LS, and the value of is approximately 130 [d
B].

Among the frequency characteristics using the rotational position of the magnetic head as a parameter shown in FIG.
The difference between the frequency characteristics of l*P2, . . . Pn is shown in FIG. 11. The slope of each characteristic curve at each rotational position Pl, P2...Pn of the magnetic head in FIG. If P+
+ P 2 . . . The spacing change amount ΔS in Pn can be determined.

FIG. 12 shows the relative spacing amount when O is the spacing amount at the rotational position PO of the magnetic head where the spacing amount is the smallest.

[Problems to be Solved by the Invention] When determining the relative spacing amount with respect to the rotational position of the magnetic head, the conventional magnetic recording/reproduction characteristic measuring device tests the reproduction output for each rotational position of the magnetic head at a plurality of different frequencies. Measure the signal sequentially, and from the measurement results,
Since the frequency characteristics for each rotational position are determined and the relative spacing at each rotational position is then determined, there is a problem in that the measurement time is long.

Further, the spacing amount is not stable and varies somewhat every time even at the same rotational position. However, with conventional measuring devices, the relative spacing amount is calculated on the assumption that the spacing amount at the same rotational position is constant, so it is not possible to accurately determine the amount of change in spacing. Furthermore, with conventional measurement equipment, the recording and reproducing characteristics of the target are measured for multiple frequencies one after another, making it difficult to accurately match the relative position of the reproducing output of each frequency. The problem was that it was difficult to increase the directional resolution.

This invention was made to solve the above-mentioned problems, and it increases not only the amount of spacing with respect to the rotational position of the magnetic head but also the amount of change in spacing at each rotational position of the magnetic head in the direction of the rotational position of the magnetic head. The purpose is to obtain a measuring device that can measure with high resolution and in a short time.

Furthermore, the purpose of this invention is to measure recording tracks and scanning tracks during playback (hereinafter referred to as
The object of the present invention is to provide a measuring device that can also measure the amount of deviation from the playback track (referred to as a "reproduction track").

[Means for Solving the Problems 1] The measuring device according to the present invention includes a test signal source that generates a test signal including a plurality of frequency components, and a reproduction signal reproduced from a magnetic recording medium on which the test signal is recorded. A plurality of filters that separately extract a plurality of frequency components, a plurality of detectors that continuously detect each output of these filters, and a magnetic head of the magnetic recording/reproducing device from the output data of these detectors. It is provided with calculation means for calculating either or both of the amount of change in spacing with respect to the recording medium and the deviation between the recording track and the reproduction track.

[Function] In this invention. The plurality of filters and the plurality of detectors separate the plurality of test signal components included in the reproduced signal and simultaneously and continuously detect the amplitude of each signal component. Therefore, recording/reproducing output data of a plurality of different frequencies at the same rotational position can be obtained simultaneously, so the measurement time can be shortened, and alignment of the measurement data is not required, so the resolution is improved. The calculation means calculates the amount of change in spacing at each rotational position of the magnetic head, or the amount of deviation between the recording track and the reproduction track, from these reproduced data.

[Embodiments of the Invention] Examples of the invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a block diagram of this embodiment, and parts with the same reference numerals as in FIG. 6 indicate the same components. In FIG. The generating oscillator (10b) is an oscillator that generates, for example, a 5.5 MH2 sine wave test signal fb, and the two test signals fa and fb are selected to have frequencies where harmonic components do not interfere with each other. fb
is selected to be a frequency that is not an integral multiple of fa.

(lla) and (Ilb) are attenuators, which are synthesized by the recording amplifier (9) and adjusted by the attenuator (llb) so that the component of the test signal fb is supplied to the magnetic head (4) with the optimum recording current. On the other hand, the component of the test signal fa is adjusted by an attenuator (lla) so that the recording current is 1/2 to 1/20 of the test signal fb. The reason for setting the level of the test signal fd in this way is that a sufficient reproduction level can be obtained even at a low level due to the AC bias effect of the high-frequency test signal fb, and that if the recording level of fa is increased, the reproduction of fb This is because the signal level is low, the S/N is lowered, and the measurement accuracy is lowered. The filter (21b) also receives the test signal f
A bandpass filter and a detector (22
a), (22b) are bandpass filters (21a
) and (21b), the amplitudes of the test signal components inputted from the A/D converters (23
a) Output to (23b), A/D: I7
The converters (23a) and (23b) each sample the input signal with a synchronized sampling signal and convert it into a digital signal, and the memory (24a),
(24b) indicates input digital data tQ.

In this way, in this embodiment, two test signals fa
, fb is output from the A/D converter (23
a), (23b) is obtained with the sampling time interval. Therefore, it is possible to measure the frequency characteristics at each sampling time point, that is, at each rotational position of the magnetic head divided by sampling time intervals in the rotational direction.

In addition to the above-mentioned spacing variation ΔS, factors that may cause variations in the reproduction output from the magnetic head include discrepancies between the recording track and the reproduction track due to tape vibration, etc., and the spacing variation ΔS is (1 ), and the track deviation amount Tws can be determined by the following equation (2).

Here, LTW is the loss due to track deviation [dB] rw
s is the track deviation rate [%], and Lrw can be determined from the frequency characteristics by calculations described later.

That is, the loss LS due to a change in the spacing amount appears as a change in the slope of the five frequency characteristics.

Furthermore, the loss LTII due to track deviation has the same frequency characteristic slope and appears as a change in the reproduction output level.

FIG. 2 shows three different types of magnetic heads in this embodiment.
This is a diagram showing the detection output levels of the detectors (22a) and (22b) at two rotational positions m P + and P 2 1 P 3 , where A, B, and C are respectively at rotational positions PI IF
5.

It shows the frequency characteristics at P3, and each frequency characteristic A
, B, and C, the spacing variation amount ΔS and the track deviation amount T-5 can be determined.

Since the frequency characteristics A and B have almost the same slope, the spacing amount at the rotational positions P1 and P2 is the same and the one rotational position P3 is the largest, and the tracking deviation amount Tll5
is obtained as the level difference at the point by extending each characteristic A, B, C to the frequency O, so the one rotation position Pl
The track deviations fi T 11s of P3 and P3 are the same, and the deviation is largest at rotational position 22 P2.In this way, at each time point (that is, each rotational position), the reproduction output level at two high and low frequencies can be measured simultaneously. Therefore, the relative spacing amount and track deviation amount at that point in time can be known.

In addition, if characteristic curves A, B, and C are selected as data measured three times at the same rotational position of the magnetic head, the amount of spacing change and track deviation at that rotational position can be known, and a large number of measurement data can be obtained. Then, the average value and the range of its dispersion can be determined.

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 of its dispersion.

Further, the average value a of the amount of track deviation and the range of its dispersion with respect to the rotational position of the magnetic head are shown in FIG.

FIG. 5 is a block diagram of another embodiment of the present invention. (25a) and (25b) are the detectors (2
2a) and (22b) are sample-hold circuits that temporarily hold the detection output values, and (28) is a switch that switches the sample-hold circuits (25a) and (25b) and inputs the held values to the A/D:1 inverter. , the sample and hold circuits (25a) and (25b) output the detection outputs output from the detectors (22a) and (22b) at the same time, that is, the amplitudes of the two high and low test signal components simultaneously reproduced by the magnetic head. Read the value,
The data is configured to be converted into digital data by an A/D converter (23) and stored in a memory (24).

According to this embodiment, the A/D converter and memory are
It can be configured in series, simplifying the circuit configuration.

In addition, in the above embodiment, the oscillator (10a) and the oscillator (t
ab) was used to generate multiple frequency components.

The plurality of frequency components may be generated by other methods such as generating FM modulated waves using an FM modulator.

Further, in the above embodiment, the frequency characteristics were measured using two test signals having different frequencies, but a configuration may be adopted in which the frequency characteristics are measured using three or more test signals having different frequencies.

Furthermore, in the above embodiment, after the digital signal from the A/D converter is stored in the memory, the computer performs calculations to determine the amount of change in spacing and the amount of track deviation. The amount of spacing change and the amount of track deviation may be determined by directly calculating the digital signal from.

Furthermore, in the above embodiment, the output of the detector is converted into a digital signal by the A/D converter, and then the calculation is performed digitally, but the calculation may be performed by an analog circuit. In this case, the calculation time is It has the advantage of being shorter and having a simpler circuit configuration.

Further, in the above embodiment, the amount of change in spacing and the amount of track deviation are measured, but it is also possible to measure only either the amount of change in spacing or the amount of track deviation.

Furthermore, in the above embodiment, the points corresponding to the entrance and exit of the rotating drum are detected by processing the data stored in the memory using a computer. Data may be stored in memory using the signal itself as a trigger, so that specific addresses in the memory correspond to drum entrances and exits.

Furthermore, in the above embodiment, the filter and detector were configured as separate blocks, but since these blocks are the basic components of the spectrum analyzer, instead of the filter and detector block, the spectrum analyzer is configured with a frequency span of 0. It may also be used as

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

Furthermore, in the above embodiment, the magnetic recording/reproducing apparatus for recording on a magnetic medium and the magnetic recording/reproducing apparatus for reproducing signals from the magnetic medium are the same; , 'Ji error may be performed by recording on a magnetic medium using a magnetic recording and reproducing device, and reproducing the magnetic medium using a magnetic recording and reproducing device to be measured, thereby determining the lu1g. in this case,
Once recorded on a magnetic medium using a standard magnetic recording/reproducing device.

At the time of measurement, it is only necessary to reproduce this magnetic medium, and there is no need to record, so the measurement time is shortened. Furthermore, it is possible to measure how much the reproduction track of the magnetic recording and reproducing device to be measured deviates from the recording track of the magnetic recording and reproducing device that serves as a reference, that is, the reference track.

[Effects of the Invention] As explained above, the present invention records a plurality of test signals having different frequencies simultaneously on a magnetic recording medium, and separates the plurality of test signal components from the signal reproduced from the recording medium. Continuously detects the amplitude of the magnetic head and measures the frequency characteristics with high resolution in the scanning direction of the magnetic head.
Since it is configured to calculate the amount of spacing change and the amount of track deviation from these frequency characteristics, it is possible to measure the frequency characteristics at each time, that is, at each scanning position of the magnetic head with high density, and Data for multiple test frequencies at one scanning position can be measured at the same time, so analysis of contact conditions between the magnetic head and recording medium, such as spacing changes and track deviations, can be quickly performed with high resolution. This has the effect of providing a magnetic recording and reproducing characteristic measuring device that can perform the following steps.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
FIG. 2 is a diagram for explaining the contents of the measurement data in this example, FIG. 3 is a diagram showing the relative spacing amount with respect to the rotational position of the magnetic head measured in this example, and FIG.
5 is a block diagram showing the configuration of another embodiment of the present invention, and FIG. 6 is a block diagram showing the configuration of the recording/reproducing characteristic measuring device according to the earlier application of the present invention. , FIG. 7 is a diagram showing the positional relationship between the rotating drum, magnetic head, and magnetic tape of a VTR, and FIG. 8 is a diagram showing signal waveforms and their states at various parts of the conventional measuring device shown in FIG. 6. Fig. 9 is a diagram showing an example of measuring the reproduction output level with respect to the rotational position of the magnetic head using a conventional measurement device, Fig. 10 is a frequency characteristic diagram using each rotational position of the magnetic head as a parameter in the conventional measurement device, and Fig. 11 Figure 10 shows the measurement example in Fig. 10, which shows the data with the longest frequency characteristic. It is a figure which shows the measurement example of the relative spacing amount of a head and a magnetic tape. (3)... Magnetic tape, (4)... Magnetic head, (
6). (7), (28)...Switch, (10a)
, (10b) ---oscillator, (lla),
(llb)...Attenuator, (]3)...Computer, (21a), (21b)...Band pass filter, (22a), (22b) = Detector, (23), (23a) . (23b) -A/D: lampata, (24)
, (24a). (24b)--Memory, (25a), (25b
) - Sample and hold circuit. Note that in each figure, the same reference numerals indicate the same or corresponding parts.

Claims (6)

[Claims] (1) A test signal source that generates a test signal including a plurality of frequency components, and a plurality of filters that extract the plurality of frequency components from the signal reproduced from the magnetic recording medium of the magnetic recording and reproducing device that records the test signal. , a plurality of detectors that individually and continuously detect the amplitude of the signal components that have passed through these filters, and the amount of change in spacing between the magnetic head and recording medium of the magnetic recording/reproducing device in question from the output data of these detectors. and a calculation means for calculating either or both of the amount of deviation between the recording track and the reproduction track. (2) The magnetic recording and reproducing characteristic measuring device according to claim 1, wherein the calculating means is constituted by an analog calculating unit. (3) A magnetic recording device according to claim 1, comprising an A/D converter that converts the amplitude of the detection output output from a wave detector into a digital signal, and a calculation means constituted by a digital calculation unit. Reproduction characteristics measuring device. (4) The magnetic recording and reproducing characteristics according to claim 3, which includes a digital memory that stores digital signals output from an A/D converter, and is configured to read data from this digital memory and perform calculations. measuring device. (5) The test signal generated from the test signal source is a signal containing a sine wave signal of two frequencies, high and low, and the frequency of the high frequency test signal is set to an integral multiple of the frequency of the low frequency test signal. A magnetic recording/reproduction characteristic measuring device according to claim 1. (6) The magnetic recording and reproducing characteristics measuring device according to claim 1, wherein the test signal is an FM modulated wave signal.