JPH0414682A - Medium inspection system for servo disk - Google Patents

Abstract

PURPOSE:To detect a degree of defects on an entire disk face with fidelity by comparing a peak value of a read signal of an (n+1)th track with an average value of peaks for each sector corresponding to an n-th track so as to detect a difference voltage. CONSTITUTION:A test signal is sequentially written in all tracks TR(n) in total N tracks by using an index detected by an index detector 31 as a start index through a test signal write circuit 42, a write amplifier 431 and a magnetic head 1a by a command from an MPU 41. Then a signal Rs(n) read from the n-th track is read by the head 1a and a read amplifier 432 and the signal is inputted to a mean value detection circuit 45 via a switch 44. On the other hand, an angle signal detected by a detector 32 is inputted to a signal generating circuit 46, a sector signal is generated and inputted to the circuit 45 to detect a mean value of signals Rs(n) in each sector and stored in a memory 411 via an A/D converter 47. A detection circuit 49 compares a value read from the memory 411 with each waveform of the signal Rs(n+1), detects a difference voltage and it is displayed on a display device 412.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for inspecting the medium of a servo disk using a servo surface method. Technology] The track pitch of magnetic disks used in information processing devices is becoming increasingly finer due to higher density, and when accessing data, it is necessary to control the position of the magnetic head relative to the track with high precision. Position control is performed using a servo system. In a magnetic disk drive, a plurality of magnetic disks are mounted on a spindle and rotated simultaneously, and a magnetic head corresponding to each disk seeks a predetermined track to access data. In the servo surface servo method, a suitable one of a plurality of disks is used as a servo disk, and a servo signal is written on it. The servo signal is very important, and if there is a defect in the disk medium, an error will occur in the servo signal and correct position control will not be performed, so it is inspected by an inspection device during the production stage.

FIGS. 2(a) to 2(C) show servo signals set on the servo disk, position control based on these signals, and a conventional inspection method. In figure (a), a large number of tracks TR are set at a constant pitch on a servo disk 1, and the disk 1
is attached to the spindle 2 and rotates. Each track TR
A servo signal p (n) shown in FIG. 3(b) is written by the magnetic head 1a to (n). In position control, the magnetic head 13 is moved between adjacent TR(n) and TR(n
il), and as the disk 1 rotates, half widths of p (n) and p (n+1) on both sides are simultaneously read out. When the voltages of both read signals are equal, it is assumed that the magnetic head 1a is located in the correct position between the two tracks, and when there is a difference in voltage, the carriage mechanism is controlled by the difference voltage, and each magnetic head for data reading is controlled. It moves to the center of the track.

A conventional inspection method for servo signals in an inspection device will be explained with reference to FIG. 2(C). Each track TR(n)
is divided into sectors S (fat), and a synchronization pulse TP and a servo signal p (n) are written to each sector, and as in the case of position control above, the magnetic head is moved between the two tracks. The readout signal Rs shown in the figure is obtained by reading out the 1/2 width of both tracks, and R8 is further shaped into a pulse RP. Here, the number of pulses of TP is greater than that of p (n), so it is distinguished, and TP
Gate signals GATEl and GAT delayed by a predetermined time "l'Dl" and TD2 with tP as the starting point.
Make E2. Servo signal p (n) is detected by GATE1, and p (n+1) is detected by GATE2, and these are sampled and held to obtain the peak value vP(n).
and yP(nil) is changed. These are compared by a comparator, and if there is a difference between the two, a differential voltage is output and an error is detected.

[Problem to be Solved] The above error detection method for servo signals does not detect defects on the entire surface of the disk. That is, the position of the synchronization pulse written to the track or the blank space in the middle of the servo signal is not inspected for defects. Inspection of magnetic disks has two stages: first, a single servo disk is inspected by a single-plate inspection device, and then it is mounted in a magnetic disk device and inspected while it is in operation. It is reasonable. However, since the purpose of the single-plate inspection is to inspect the entire surface of the disk as precisely as possible, the above-mentioned inspection method is not appropriate. Furthermore, the above inspection has the disadvantage that the detected defect data is not proportional to the size of the defect. This will be explained with reference to FIG. In the figure, it is assumed that there is a defect (a) of area A at the illustrated position of one track TR(n), and if the active area of the magnetic head is B, then the ratio occupied by the defect is A/B. In this case, the magnetic head 1a acts across both tracks TR(n) and TR(n+1), and the detection signal for defect (a) decreases at the rate of A/H.

On the other hand, a defect (
(b), the area of the defect (0) acting on the magnetic head is A/2, so the signal decline rate is A/2B.
becomes. For example, when the area ratio A/B of both defects (a) and (b) to TR(n) is 10%, (
The decrease in the detection signal for (b) is 10%, and for (0) it is 5%. As described above, the detection signal changes depending on the position of the defect, so that the size of the defect cannot be accurately detected, and only the presence or absence of the defect is detected as an error.

To solve the above-mentioned drawbacks, there is a need for an inspection method that can inspect the entire surface of a disk without blank spaces and can faithfully detect the size of defects.This invention provides a method for solving the above-mentioned problems for single-board inspection equipment. The purpose is to provide the following.

[Means for Solving the Problems] The present invention is a medium inspection method for a servo-surface servo disk using a magnetic disk inspection device. The magnetic head is sequentially sought to the center of each of the total number N of tracks set on the servo disk under the control of a microprocessor, and for one revolution of each track using the index signal obtained by rotation of the servo disk as the starting point, Write/output a continuous "l" test signal at a constant frequency. The average value of each wave height value of the readout signal from the track number n [n=1 to (N-1)] is detected for each sector obtained by equally dividing the track into an appropriate number in the circumferential direction and stored in the memory. Remember. Each peak value of the read signal from the track numbered (n+1) adjacent to the track numbered n is compared with the average value of each corresponding sector, and the difference voltage between the two is detected.

The above-mentioned equal division of sectors into each track is performed by inputting an angle signal obtained from a disk rotation angle detector provided in the inspection device to the above-mentioned microprocessor.

[In the above-described servo disk inspection method, all N tracks are inspected by continuous test signals of "1", so that no blank areas are left uninspected. In the test, each peak value of the read signal of the track numbered (n+1) is compared with the average value of each peak value of each corresponding sector of the track numbered n, so the test signal is determined in the circumferential direction of the disk. Correct comparison is made by removing the influence of fluctuations, and since the test signal is read out with the magnetic head facing the center of the track, the ratio of the area of the defect to the area of action of the magnetic head is directly expressed as a differential voltage. Detected and the size of the defect can be correctly determined.

[Embodiment] Figures 1 (a) and 1 (b) show a block diagram of the inspection unit 4 and test signals in an embodiment of a magnetic disk inspection apparatus to which the servo disk medium inspection method according to the present invention is applied. . In figure (a), a microprocessor (M
PU) 41, the test signal writing circuit 42
, the index detected by the index detector 31 by the write amplifier 431 and the magnetic head 1a
INDEX) as the starting point, 1 of each TR(n) of the total number N
The test signal WP shown in FIG. 3(b) is written sequentially around the circumference.

Next, by the magnetic head fa1 read amplifier 432,
A readout signal Rs(n) is read out from the track with number n, and the signal Rs(n) is manually inputted to the average value detection circuit 45 via the switch 44. On the other hand, the angle signal detected by the rotation angle detector 32 is input to the sector division signal generation circuit 46, and a sector division signal is generated and the average value detection circuit 45
is given to the signal Rs(n
) is detected.

A V E (r) is digitized by the A/D converter 47 and sequentially stored in the memory (MEM) 411 by the MPU 41 . Next, the magnetic head 1a moves to the center of TR(nil) and the signal Rs(n+1) is read out.
The voltage is manually applied to the differential voltage detection circuit 49 via the read amplifier 43b and the switched switch 44. Differential voltage detection circuit 4
9 is given the average value A V E (r) read out from the MEM 411 by the MPU 41 and converted into an analog by the D/A converter 48, and the signal Rs(n
+1) are compared for each sector S (r), and the difference voltage between them is detected and input to the MPU 41, edited into a predetermined format, and output to the display 412.

The above processing is sequentially performed on all N tracks by sequentially changing n from 1 to (N-1). Further, the number of sectors is set to a large number, such as 512 or 1024, to avoid the influence of fluctuations due to the rotational angular position of the test signal as much as possible. Note that the average value detection circuit 45 and the differential voltage detection circuit 49 are based on ordinary technology, and detailed explanations thereof will be omitted.

[Effects of the Invention] As is clear from the above explanation, in the servo disk medium inspection method according to the present invention, continuous "1"
With the test signal, all the tracks, N in total, are tested without any blank areas. In addition, each wave height value of the test signal is compared with the average value of each wave height value for each corresponding sector of the adjacent track, so the influence of fluctuations in the test signal due to the circumferential direction of the disk is removed, allowing accurate comparison. done, and furthermore,
Since reading is performed with the magnetic head facing the center of the track, the ratio of the area of the defect to the active area of the magnetic head is directly detected as a differential voltage, and the size of the defect can be accurately determined. The effect of applying this method to a device for detecting defects in servo disks with high precision is significant.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are block diagrams and diagrams showing test signal waveforms in an embodiment of the servo disk medium inspection method according to the present invention, and FIGS. 2(a), (b), and (C) 3 is an explanatory diagram of tracks set on a servo disk of the servo surface type, servo signals written to the tracks, and a conventional inspection method. FIG. 3 is an explanatory diagram of one point of the conventional inspection method. 1... Servo disk, la... Magnetic head,
2... Spindle, 31... Index detector,
32... Rotation angle detector, 4... Inspection section, 41.
...Microprocessor (MPU), 411...Memory (MEM), 42...Test signal writing circuit, 431...Write amplifier, 432...Read amplifier, 44...Switch, 45... Average value detection circuit, 4
6... Sector division signal generation circuit, 47... A/D converter, 48... D/A converter.

Claims (2)

[Claims] (1) In the medium inspection of a servo disk using the servo surface method using a magnetic disk inspection device, the magnetic head is sequentially sought to the center of each of the total number N of tracks set on the servo disk under the control of a microprocessor. Writing/reading a continuous test signal of "1" at a constant frequency for one revolution of each track, starting from an index signal obtained by rotation of the servo disk,
The average value of each wave height value of the read signal from the track number n [n=1 to (N-1)] is detected for each sector obtained by dividing the track into an appropriate number of equal parts in the circumferential direction, and the average value is stored in the memory. and the number (n+
A servo disk characterized in that each peak value of the read signal from the track of 1) is compared with an average value of each corresponding sector, and a difference voltage between each of the peak values and the average value is detected. media inspection method. (2) In the above, an angle signal obtained from a rotation angle detector of the servo disk provided in the inspection device is input to the microprocessor to equally divide the sectors into the tracks. servo disk media inspection method.