JPS59217230A - Defect detector for magnetic recording medium - Google Patents

Abstract

PURPOSE:To detect an error of a reproduced signal originating from phase distortion of a magnetic recording medium and improve the quality by detecting a shift in peak point generated by a peak point detecting means on the basis of the phase distortion of the reproduced signal through a window obtained by a window generating means. CONSTITUTION:The window generating circuit 5 sends out window signals having waveforms C and D on the basis of a zero point detection signal. The peak detecting circuit 3 detects peaks of a waveform A and sends out pulse shown by B. A flip-flop 6 is set with the waveform C by using pulses B as a clock and a flip-flop 7 is set with the waveform D by using the pulses B as a clock. If a magnetic recording medium has a defect to has phase distortion in a reproduced waveform, the waveform A shifts in peak point and zero point as shown by a dotted line. The waveforms C and D are generated on the basis of the zero point of a normal waveform which is several cycles before the waveform A, so their positions are accurate, and the flip-flop 7 is not set because of the position shift of pulses shown by dotted lines of B, so that a phase error occurrence signal is sent out through an OR circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to means for detecting electromagnetic defects on the surface of a magnetic recording medium, and more particularly to a magnetic recording medium defect detection apparatus for detecting fluctuations in the phase direction.

(b) Prior art and problems Due to manufacturing problems with magnetic recording media such as magnetic disk media and magnetic tape media, when reproducing recorded signals,
Due to a defect on the surface of the medium, the playback signal cannot be reproduced properly.
It may be wrong. Such defects are detected, and if they are usable, their positions are recorded and marked as defective.

The means for detecting electromagnetic defects on the surface of the medium is 41.

Analyze the signal obtained by doing so, and show its amplitude fluctuations.1.Missing bits (bits whose amplitude is below a certain value and a signal error occurs), modulation (amplitude modulation), and noise after erasure of records. Technique: 1-Is there a method commonly used to evaluate stravit? ). The amplitude of the reproduced signal and the amplitude of the noise generated by media defects after recording and erasing are considered as it'T' fIIliL7, but recently it has become clear that the fluctuation in the phase direction, which is good for improving recording density, is a major factor that affects the quality of the reproduced signal. It has become. Therefore, the conventional test in the amplitude direction () has the disadvantage that it cannot provide a satisfactory magnetic recording medium.

(C) Purpose of the Invention The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to detect defects in a magnetic recording medium by detecting fluctuations in the phase direction of a reproduced signal. An object of the present invention is to provide a recording medium defect detection device.

(d) Structure of the Invention The structure of the present invention includes means for detecting a peak point of a signal reproduced from a magnetic recording medium, means for detecting a zero point of the reproduced signal, and delaying a signal obtained by iη from the zero point detecting means. and means for configuring a window from the output of the delay means, and means for generating a window based on the phase distortion of the reproduced signal. Detection is performed using the window obtained from

(e) Embodiment of the invention FIG. 1 is a block diagram of a circuit showing an embodiment of the invention.
FIG. 2 is a diagram showing waveforms of various parts to explain the operation of FIG. 1. A signal is input from which a test record recorded on a magnetic recording medium is read by a magnetic head. The signal amplified by the automatic gain adjustment amplifier 1 has a waveform as shown in FIG. 2 and enters a zero point detection circuit 2 and a peak detection circuit 3. Zero point detection circuit 2 detects zero points such as those shown at 9 and 10 and sends them to delay circuit 4. Delay circuit No. 4 delays the extra zero point detection signal and sends it to the window generation circuit 5.

The delay time can be adjusted within several cycles of waveform A. The window generating circuit 5 sends out a window consisting of a rectangular wave shown by waveforms C and D based on the zero point detection signal. The window is generated at a position where the peak of waveform A can be detected by adjusting the delay time of the delay circuit. The peak detection circuit 3 detects a peak in the waveform and sends out a pulse as shown in B. Flip-flop 6 is clocked by pulse +3 and has waveform C, and flip-flop 7 is clocked by pulse B.
They are each set using the waveform as the clock.

If there is a defect in the magnetic recording medium and phase distortion occurs in the re-outgoing waveform, the peak and zero points of the waveform A will shift as shown by the dotted line. Since waveforms C and D are generated by the zero point of the normal waveform several cycles before the waveform, their positions are normal, and the flip-flop 7 is caused by the position shift of the pulse shown by the dotted line in B. First, a phase error occurrence signal is sent to the output via OR cycle #1Pi8.

(f) As described in detail, the present invention makes it possible to detect errors in endogenous signals based on phase distortion of a magnetic recording medium, which could not be detected using conventional methods, so that high-quality magnetic recording can be achieved. media can be supplied.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a circuit showing an embodiment of the present invention, and FIG. 2 is a diagram showing waveforms of various parts to explain the operation of FIG. 1. 1 is an automatic gain adjustment amplifier, 2 is a zero point detection circuit, 3 is a peak detection circuit, 4 is a delay circuit, 1/8.5 is a window generation circuit, and 6.7 is a flip-flop.

Claims (1)

[Claims] means for detecting a peak point of a signal reproduced from a magnetic recording medium; means for detecting a zero point of the reproduced signal; means for delaying the signal obtained from the zero point detecting means; and a means for generating a magnetic field, and detects a positional fluctuation of a peak point generated by the peak point detecting means based on the phase distortion of the reproduced signal using a window obtained from the window generating means. Recording medium defect detection device.