JPH01235004A - Defect detecting system for magnetic medium - Google Patents

Abstract

PURPOSE:To realize the 100% detection of modulation of a high frequency with high accuracy and at the same time to improve the checking accuracy and the reliability of a magnetic medium by adding the waveheight values of each one round together for each designated numeric value and comparing these added waveheight values with those of the adjacent sectors. CONSTITUTION:The signal of a fixed amplitude is read out of a magnetic medium 1 by a magnetic head 2 and amplified by a reproducing circuit 3. Hen a waveheight value detecting circuit 4 detects the waveheight values D1, D2, D3 and so on. Each of these waveheight values is converted into the digital waveheight value respectively. These digital waveheight values are successively written into a memory 6 with the synchronization of a timing generating circuit 7. The circuit 7 adds those values D1, D2... together via an adder 80 for recording until a signal is sent to a memory 81 from the circuit 7. At the same time, the waveheight values DK+1, DK+2,... equivalent to (k) bits are added together by an adder 90 and recorded into a memory 91 at the time point when the signal is transmitted from the circuit 7. Then the total value of the memory 81 is compared with that of the memory 91. Thus it is possible to measure the characteristics required for a servo medium with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a defect detection method for magnetic media, and more particularly to a defect detection method for magnetic media that detects high frequency modulation errors.

[Conventional technology]

In order to increase the track density of magnetic media used in recent magnetic recording and reproducing devices, consideration has been given to narrowing the track width or reducing the amount of off-track in order to increase the recording density. In order to reduce this amount of off-track, a method called track servo has been adopted. This type of servo method writes a special pattern of signals in a special area and uses this information to reduce the amount of off-track. .

1. The main technique used since then has been to read two different signals and determine the amount of off-track and off-track direction based on the difference in signal output peak values.

Conventionally, in order to inspect this type of medium, it was necessary to actually write servo information on the medium and judge it as servo position information of the magnetic recording/reproducing device as described above.

[Problem to be solved by the invention]

In the above-mentioned conventional inspection method, medium defect information is only detected as positional deviation information, and it is not possible to accurately determine whether the defect is in the medium or the follow-up circuit.

In addition, as a similar inspection method, media defects (drops, etc.)
There is a method of tightening the level of output (out, modulation), but this must be so strict that even normally good products must be marked as defective in order to guarantee the original servo information. This is because the detection sensitivity is poor because the level is set relative to the average output of the negative cycle. Also, the method for determining the output difference between adjacent tracks is based on the magnetic head and recording/reproducing circuit used for recording/reproducing.

The reproducibility deteriorated due to ambient temperature, power supply noise, etc., and included the above-mentioned problems.

[Means to solve the problem]

The magnetic medium defect detection method of the present invention includes a reproducing circuit that reproduces a magnetic medium on which a signal of a constant amplitude is recorded, a peak value detection circuit that detects the peak value of the reproduced signal, and converts the peak value into a digital quantity. converting, to a 'D converter, an addressable memory device into which the digital quantity is written, and adding the data read from the memory device for each specified quantity and converting this sum into another The memory device includes the memory device in which the address is written, and a circuit that compares the added value with the added value of the next specified quantity of the same track.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the invention. In FIG. 1, one embodiment of the present invention is a magnetic medium defect detection method for inspecting a magnetic medium on which a signal of a constant amplitude is recorded, and includes a reproducing head 2 that reads a signal of a constant amplitude from a magnetic medium 1; A reproduction circuit 3 that reproduces the signal from the reproduction head 2, a peak value detection circuit 4 that detects the peak value of the reproduced signal, an A/D converter 5 that converts this peak value into a digital quantity, and a digital quantity that converts this digital quantity. an addressable memory device 6 for writing;
Adder and memory device 8. Adds the read data in specified quantities and writes the added value to another address. It also includes a comparator circuit 10 that compares this added value with the next designated amount of added values on the same track, and a timing generating circuit 7 that supplies timing signals to each section based on the output signal of the reproducing circuit.

In this embodiment, a signal of constant amplitude on a magnetic medium 1 is read by a magnetic head 2, the signal is amplified by a reproduction circuit 3, and then detected and rectified by a peak value detection circuit 4. In this peak value detection circuit 4, as shown in FIG. 2, the peak value DI,
D2 + D3... is detected. Each wave height value is converted into a digital wave height value D1 by the A/D converter 5. D2, D
After being converted to 3, the data is sequentially written into the memory device 6 in synchronization with the timing generation circuit 7. At the same time, the timing generation circuit 7 adds and records the peak values, D2, . When the signal from the timing generation circuit 7 is output, the bit division high value is sent to the memory 91 through the adder 90 in the same way, 42.
. . . are added and recorded (V,,).

When the timing generation circuit 7 reads 2 bits, the total value of the memory 81 and the memory 91 is input to the comparison circuit 10,
The slice levels H, P, and M are compared using the following conditional expression.

■ −〇　・　×100≦H, P, MVn+X,.

Similarly, the next 3-bit addition value is written into the memory 81 and substituted as V yl *2 in place of the conditional expression (2) and calculated.

The added value of the peak values for each bit one after another is compared with the added value of the peak values for the previous bit. If the present memory device 6 has a capacity equal to the BiSoto number written on the magnetic medium, it is also possible to compare adjacent outputs in bits.

By comparing the outputs between adjacent media in this way, it becomes possible to analyze high frequency waveforms that could not be quantified until now, and it becomes possible to accurately measure the characteristics required for the servo medium.

〔Effect of the invention〕

As explained above, the present invention can be applied to
By adding up to several hundred bits from and comparing it with the peak value of the adjacent sector (area), it becomes possible to accurately detect 100% of high frequency modulation (bypass modulation), greatly improving the accuracy and reliability of magnetic media inspection. .

[Brief explanation of the drawing]

FIG. 1 is a circuit system diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing output waveforms of main parts, addition values, and memory address correspondence diagrams. DESCRIPTION OF SYMBOLS 1... Magnetic medium, 2... Playback head, 3... Playback circuit, 4... Peak value detection circuit, 5... A/D converter, 6... Memory, 7... timing generation circuit, 8,
9... Adder and memory, 10... Comparison circuit.

Claims (1)

[Claims] a reproduction circuit that reproduces a magnetic medium on which a signal of a constant amplitude is recorded; a peak value detection circuit that detects the peak value of the reproduced signal; an A/D converter that converts the peak value into a digital quantity; an addressable memory device into which a quantity is written, a memory device in which data read from the memory device is added for each specified quantity and the added value is written to another address; A defect detection method for magnetic media consisting of a circuit that compares the added value for each specified quantity on the same track.