JPS59110018A - Inspecting method of magnetic recording medium - Google Patents

Abstract

PURPOSE:To inspect the variation state of the amplitude of a playback output with good linearity up to a high frequency by inputting a digital signal and a signal which indicates the position of recording and the reproduction of a magnetic recording body directly or through a memory, and processing those signals digitally. CONSTITUTION:An envelope detecting circuit consists of a level comparing circuit 17, up/down counter 28, and DA converter 29; and 35 is a clock oscillation circuit and 36 is a memory. When the envelope detecting circuit 61 is used, the output corresponding to the recording/reproduction output from the magnetic recording body is obtained as a digital signal even at 10-30MHz frequencies. Further, the correspondence relation between the digital signal 33 corresponding to the envelope of the recording/reproduction output from the magnetic recording body and a recording/reproduction position on the magnetic recording body is stored in the memory 36, and this data is inputted to a computer 21 successively for digital arithmetic processing, checking the variation state of the recording/reproduction output at a position on a magnetic disk by calculations. This method obtains the signal corresponding to the envelope of the recording/reproduction output from the magnetic recording body as the digital signal and checks the variation state of the output precisely.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for inspecting fluctuations in recording and reproducing output of a magnetic recording medium such as a magnetic disk or magnetic tape.

Magnetic recording body inspection apparatuses generally have a dropout inspection function and the like, as well as a function of inspecting the state of fluctuation in recording/reproduction output, ie, modulation, depending on the position of the magnetic recording body.

FIG. 1 shows a block diagram of the modulation inspection part of a conventional magnetic recording medium inspection apparatus using a magnetic disk as an example, where 1 is a magnetic disk, 2 is a magnetic head, 3 is a recording adder, and 4 is a recording clock. Oscillator, 5 is regenerative amplifier, 6
9 is a reproduction output envelope detection circuit composed of a rectifying circuit 7 and an integrating circuit 8;
Hold circuit] Maximum i1'f formed by 1 and t
+-Minimum value detection circuit, 12 is an AD converter, 13 is an integration circuit for detecting an average output value 1rjl l? 4.14 is a modulation error level setting circuit using a DC amplifier,
15 is a modulation error detection circuit using a comparator;
Reference numeral 16 indicates a magnetic disk rotation mechanism unit for rotating the magnetic disk 1; 17 indicates a rotation angle IW detector for generating a rotation angle 11'' signal of the magnetic disk 1; and 18 indicates a magnetic head feeder for moving the magnetic head 2. 19 is a track detection circuit that outputs the track position of the magnetic heald 2; 20 is a control circuit for operating each circuit according to instructions from a computer 21; This is a control circuit for sending output signals to the computer 21.

In FIG. 1, a signal according to a clock generated by a recording clock oscillator 4 is amplified by a recording amplifier 3,
lt % is supplied to the head 2 as a recording current5. #Make 11 disks Ka k'. The signals recorded on the magnetic disk 1ζ in this way are reproduced by the magnetic disk 2, and the output width a! +<h After being amplified by 5, a reproduction output envelope detection circuit 6 obtains a DC output according to the amplitude of the reproduction output, that is, an envelope output 22. Then, the maximum value 1i[A and the minimum value B of the envelope output 22 are detected in an analog manner by the crotch value/minimum value detection circuit 9, which is converted into a digital signal by the AD converter 12I, and the modulation M=
(Calculate AT()/(A+B). Also, by integrating the envelope output 22 by the integrating circuit 13, the average output iV is calculated.

is detected and amplified or attenuated by the DC amplifier 14 to set a positive modulation error level Vp and a negative modulation error level VM, and these are compared with the envelope output 22 by the comparator 15i, and the envelope output 22 is positive. When the modulation error level is larger than Vp or smaller than the negative modulation error level ■M, it is regarded as a modulation error, and the rotation angle and track position of the magnetic disk 1 at that time are detected by the rotation angle detection circuit 17 and the track detection circuit 19, respectively. and input it into the computer 21.

The reproduced output envelope detection circuit 6 obtains a DC output according to the amplitude of the reproduced output, that is, an envelope output 22, and the rectifier circuit 7 used here is a C4 transistor 23, 24Q) base as shown in FIG. - Circuits that utilize nonlinearity between emitters were often used. However, when using this rectifier circuit, the linearity of the playback output amplitude versus the DC output is poor, especially for low-level signals, and the playback output fluctuates within a range from low to high levels in magnetic disk inspection equipment. If it is large, there is a drawback that the inspection accuracy deteriorates.

In addition, as a rectifier circuit with good linearity of reproduction output amplitude versus DC output, a diode 25 as shown in FIG. A rectifier circuit using an amplifier 26 was also often used. However, due to the limitations of the frequency and number characteristics of operational amplifiers, this circuit does not operate correctly for signals with high frequencies of 10', M Hy or higher, and is no longer compatible with the increasing density and frequency of magnetic disk drives. Ta.

(5) Also, in FIG. 1, the analog circuits 9 to 15 for inspecting the state of the envelope output 22 use many operational amplifiers, etc. 5! : is complicated, and also requires many adjustments such as offset Bi node and gain adjustment.

The present inventor previously developed a circuit for detecting the peak value of a continuous alternating current signal, such as the recording/reproducing output of a magnetic disk, with good linearity up to high frequencies, using a continuous alternating current signal having the configuration shown in FIG. A peak value detection circuit is proposed. This circuit converts the digital signal 33 into the analog signal 34ζ.
) A converter 29 and a level comparison circuit 27 that compares the level of the analog signal 34 and the peak value of the human-powered continuous alternating current signal 30; controlled,
The device is characterized in that it includes an up/down counter 28 that outputs the digital signal 33, and is configured such that the level of the analog signal 34 is approximately equal to the peak value of the input continuous alternating current signal 30.

The magnetic recording body inspection device shown in Fig. 1 (in this case, the envelope (6)) - By replacing the loop detection circuit 6 with the continuous AC signal peak value extraction circuit, the envelope of the recording and reproduction output can be detected with good linearity up to high frequencies. Therefore, the quality of the magnetic recording medium can be inspected with precision up to high frequencies. , analog ++j
l JJI! The drawback is that it requires a lot of time for adjusting the offset and gain of the circuit.
f(1).

The purpose of the present invention is to eliminate the drawbacks of the conventional inspection method for a-air recording media, use a simple configuration with as few analog processing circuits as possible, and a circuit with few adjustment points, and detect the fluctuation state of the reproduced output amplitude at a high frequency. Output 1: An object of the present invention is to provide a recording medium inspection method that can inspect a recording medium with good linearity.

The present invention is a magnetic recording medium of the order of 1t1? In a magnetic recording medium inspection method that uses a computer to inspect the state of fluctuations in recording and reproduction output due to a DA converter for detecting the signal; a level comparison circuit for comparing the level of the analog trout number with the peak value of the recording/reproducing output from the magnetic recording medium; and control of addition and subtraction counts of the clock signal by the output of the level comparison circuit. using an envelope detection circuit configured such that the digital signal corresponds to the peak value of the recording/reproduction output from the @ gas recording medium, and is equipped with an up/down counter that outputs the digital signal, 18
ii) A magnetism system characterized by inputting a first generation digital signal and a signal representing the position of the magnetic recording medium for recording and reproduction into a computer as data, either directly or through a memory, and digitally processing the data by the computer. This invention provides a recording medium inspection method.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows a block diagram of a magnetic recording medium inspection apparatus used in the magnetic recording medium inspection method using a magnetic disk as an example, and 6' is a level comparison circuit 27, an up/down counter 28, and a DA. 35 is a clock oscillation circuit, and 36 is a memory.

That is, in contrast to the envelope locking circuit shown in FIG. 4, which outputs an analog signal having a level approximately equal to the liquid height 1i'-+ of the input continuous AC signal 30 corresponding to the recording/reproduction output from the magnetic recording medium. The present invention ζ focuses on the fact that the digital signal 33 also corresponds to the peak value of the input continuous alternating current signal 30, and uses an envelope detection circuit configured to output this signal. As a result, even at a high frequency of 10 to 30 MHz, an output corresponding to the envelope of the recording/reproducing output from the magnetic recording medium can be obtained with high precision as a digital signal. Furthermore, a memo IJ-36f stores the correspondence relationship between the digital signal 33 corresponding to the envelope of the recording/reproduction output from the magnetic recording body and the position 1 related to the recording/reproduction of the magnetic recording body;
By sequentially inputting the data to the converter 21 and performing digital arithmetic processing, for example, the maximum value A and the minimum value A-gB in the recorded rack of the digital signal 33 corresponding to the envelope i are detected,
Modulation M=(A-B)/(A+I'!)
Calculate the envelope number, and calculate the 3P average 11 in the corresponding recording track of the corresponding isotal No. 18 33.
f4°\l.

The positive modulation error level Vp to the modulation error level VM is calculated by multiplying this by a constant factor, and these are compared with the digital signal 33 sent to the envelope detection circuit to determine whether the digital signal 33 is This method detects as a modulation error when it is larger than the positive modulation error level Vp or smaller than the negative modulation error level VN+. The signal corresponding to the envelope of the recording/reproducing output from the magnetic recording medium is extracted as a digital signal, and the subsequent processing is done digitally, so it is simple and requires a circuit with few adjustment points. It is possible to check the state of the variable axis of the recording and reproduction output from the magnetic recording medium.

In FIG. 5, a clock 1t [31 is generated (
10) Although a useless clock oscillator 35 is shown, it may also be used in common with the recording clock oscillator 4, and the clock signal 31 is generated from the reproduction output 30 by the phase rotation lυ1 oscillator.
It may also be configured to generate ().

In addition, memo IJ-: (6) records the correspondence between the digital signal 33 corresponding to the magnetic (recording/reproducing output θ) envelope and the recording p of the magnetic recording body] For example, in the case of a magnetic disk, the envelope ζ in one recording track is
The corresponding digital signal 33 may be set at a fixed angle interval (1).The memory 36 shown in FIG.
・-In Ku 21? γ;) may be used directly.

Note that although explanation 1 above uses the case of a magnetic disk as an example, explanations corresponding to explanation 1 apply to other magnetic recording media such as magnetic tape and magnetic drums. By using the 1lII system and the associated detection circuit, the state of fluctuation in the recording/reproducing output can be inspected in exactly the same manner as in A'7.

As described above, according to the magnetic recording medium inspection method according to the present invention, the analog processing circuit system is extremely small and a simple circuit with almost no adjustment points is used, and the magnetic recording medium can be inspected with high precision and linearity up to high frequencies. It is possible to inspect the state of fluctuations in the recording and playback output of

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional magnetic disk inspection device, FIGS. 2 and 3 are circuit diagrams showing an example of the rectifier circuit in FIG. 1,
FIG. 4 is a block diagram showing an example of an envelope detection circuit, and FIG. 5 is a block diagram of a magnetic recording body inspection apparatus used in an embodiment of the magnetic recording body inspection method according to the present invention. In these figures, 1 is a magnetic disk, 2 is a magnetic head, 3ftft recorder, 4 is a recording clock oscillator, 5 is a reproduction amplifier, 6.6' is a reproduction output envelope detection circuit, 7 is a rectifier circuit, and 8 is an integration circuit. , 9 is a maximum value/minimum value detection circuit, 10 is a comparator, 11 is a sample/hold circuit, 12 is an AD converter, 13 is an integration circuit, 14 is a DC amplifier, 15 is a comparator, 16 is a magnetic disk rotation mechanism Part 1
7 is a rotation angle rW detector; 18 is a magnetic head feeding mechanism;
19 is a track detection circuit, 20 is a control circuit, 21 is a beater, 22 is an envelope output, 23.24i:
25 is a diode, 26 is an operational amplifier, 27 is a level comparison circuit, 28 is an up/down counter, 29 is a DA converter, 35 is a clock oscillator,
36 indicates memory. (13) Year 2 Figure 5th Fertility

Claims (1)

[Claims] In a method for inspecting magnetic recording bodies that uses a computer to inspect the state of fluctuations in the recording and reproduction output depending on the position of the magnetic recording body, a digital signal is converted into an analog signal as a circuit that detects the envelope of the recording and reproduction output from the magnetic recording body. A DA converter that converts into a signal, a level comparison circuit that compares the level of the analog signal with the peak value of the recording/reproduction output from the magnetic recording medium, and an addition count/subtraction count of the clock signal based on the output of the level comparison circuit. and an up/down counter that outputs the digital signal, and is configured such that the digital signal corresponds to the peak value of the recording/reproduction output from the magnetic recording medium. , a magnetic recording medium characterized in that the digital signal and the signal representing the position of the magnetic recording medium for recording and reproduction are input as data to a computer directly or through a memory, and the data is digitally processed by the computer. Record inspection method.