JPH0589457A - Inspecting method for medium of magnetic disk - Google Patents

Abstract

PURPOSE:To execute reliable medium inspection for a magnetic disk whose storage capacity is 2GB or more. CONSTITUTION:A medium whose maximum usable frequency exceeds the inspectable frequency of a certifier in the standpoint of a standard is inspected by reducing properly the frequency of a test code lower than the maximum usable frequency. The inspectable frequency 2f of the certifier in the standpoint of the standard is made 18MHz, and in the case of the disk whose maximum usable frequency of the medium is 36MHz, the frequency of the test code is made 24MHz of the two-thirds of the maximum usable frequency. The constitution of the test code is made code constitution in which the basic pattern of '100' continues, and the magnetic medium is inspected by writing and reading the test code three times as shifting cyclically its '1' bit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medium inspection method for hard magnetic disks.

[0002]

2. Description of the Related Art A hard magnetic disk (hereinafter simply referred to as a disk) which is widely used as an information recording medium is inspected for its recording characteristics by a certifier during the manufacturing process. The inspection is performed in detail for various items, but the basic ones will be described with reference to FIG. The test code “1010 ...” Shown in (b) is written / read by the certifier to a predetermined track 1a of the disk 1 shown in FIG. 2 (a), and the peak value of the read signal is set to its average value. By comparison, missing errors, extra errors,
Alternatively, the modulation characteristic or the like is inspected. Here, regarding the relationship between the recording performance of the medium and the frequency of the test code, the maximum usable frequency of the recorded data of the disk is limited by the recording performance of the medium, and if this maximum used frequency is 2f, it corresponds to this. The time width Δt of the bit "1" of the test code is 1 / 2f. The repetition frequency of the test code in which "10" is repeated is f. On the other hand, in the certifier, it is desirable to reproduce the waveform of the read signal as faithfully as possible. For this reason, the frequency characteristic is 0 to 2f so that the harmonic component thereof is reproduced as much as possible with the repetition frequency f as the fundamental wave. It is designed and manufactured so that it becomes flat between the above and gradually lowers. This frequency 2f is the upper limit of the inspectable frequency according to the certification standard. FIG. 3 (a) shows the frequency characteristics of a conventional certifier for a disc having a recording capacity of 1 GB (gigabyte), and the maximum usable frequency 2f ₁ of this disc is 18 MHz.
z, and correspondingly, the frequency characteristic of the detection sensitivity of the certifier is approximately 18M as shown by the curve S.
It is flat up to Hz, and gradually decreases above that, and 18 MHz is the upper limit of the inspectable frequency according to the standard.

[0003]

By the way, recently, the recording performance of the medium has been improved and a large-capacity disk of 2 GB or more has appeared, and in the case of 2 GB, the maximum usable frequency 2f ₂ is (a) 2) 2f ₁ 2 of 2GB
It is double 36MHz. On the other hand, the detection sensitivity characteristic of the certifier has not been improved yet, and a large-capacity disk is about to be inspected without conforming to this. Fig. 3 (b) shows 2G using a conventional certifier.
The waveform of the read signal from the disk B is shown as an example. In the signal waveforms (a), (b) and (c), the crest value is lower than the normal level L _s due to the lack of the head because the harmonics are attenuated L _R
Has fallen to. On the other hand, in waveforms (d) and (e), the crest value itself is lowered due to the performance of the medium itself, which results in a missing error. The error detection method using a certifier is to compare the crest value of each signal with respect to the average value of the crest value as described above, so that the average value also decreases when the crest value decreases due to the attenuation of harmonics, Waveforms (d) and (e), which should cause a missing error, may have a relatively high peak value and may not cause an error. In addition, the modulation characteristics and errors due to the modulation characteristics are greatly affected by the attenuation of the harmonics. It should be noted that the frequency characteristics of the detection sensitivity are more important than in the prior art because the peak value of the read signal tends to be lower in the disk with the increased recording capacity. As a sub-optimal measure against the above problems, a method for performing reliable inspection by a certifier without improving the performance of a 2 GB disk is urgently needed. Furthermore, the increase in recording capacity due to the improvement in the performance of the medium and the improvement in the performance of the certifier are, as it were, a play of the weasel. On the other hand, a general method that allows reliable inspection is desirable. The present invention has been made in view of the above, and an object thereof is to provide a reliable medium inspection method by a conventional certifier regardless of a standard for a disk having a recording capacity increased to 2 GB or more. To do.

[0004]

SUMMARY OF THE INVENTION The present invention is a medium inspection method which achieves the above object, wherein in the above-mentioned certifier, the maximum usable frequency exceeds the inspectable frequency specified by the certifier. Then, the frequency of the test code is appropriately reduced from the maximum usable frequency for the inspection. Inspectable frequency 2 according to certification standards
f is 18 MHz, and the maximum usable frequency of the medium is 36 MH
In the case of the z disc, the frequency of the test code is set to 24 MHz, which is 2/3 of the maximum usable frequency of 36 MHz.
The test code has a code structure in which a basic pattern of "100" is continuous, and one bit of this code structure is cyclically shifted and written / read three times to inspect the magnetic medium.

[0005]

First, regarding the reduction of the frequency of the test code, the frequency characteristic of the detection sensitivity of the certifier reproduces to some extent even at a frequency higher than the inspectable frequency according to the standard, but up to twice the high frequency. Not growing. Therefore, when a test code having a doubled frequency is used for a medium having a doubled recording capacity, the harmonics are attenuated and the waveform is not reproduced faithfully. Therefore, if the harmonic component is reproduced to some extent by using a test code of an appropriate frequency between these, a better medium inspection can be expected by a test code of double the frequency. Explaining the above with concrete numerical values, the inspectable frequency 2 according to the certification standard
If f is 18 MHz, the second and third harmonics are 36
MHz and 54 MHz. On the other hand, a disc with a recording capacity of 2 GB has a maximum usable frequency of 36 MHz.
On the other hand, the frequency of the test code is set to 24 MHz, which is 2/3 of the maximum usable frequency of 36 MHz. The second and third harmonics are 48 MHz and 72 MHz, and at least the second harmonic is not attenuated so much and the third harmonic is also attenuated to some extent, but the waveform is reproduced well by these and the fundamental wave, and reliability is improved. A certain medium inspection is performed. The above checking method is a suboptimal measure to the last, and there is always an unsatisfactory resentment.
The number of inspections by this is improved again as follows. That is, the test code has a code structure in which basic patterns of "100" are continuous, and this code structure is cyclically shifted bit by bit, and the medium is inspected by writing / reading three times. The reliability of the inspection is improved by the inspection three times, but the reliability is expected to be further improved by writing / reading “1” on the entire track.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention, in which (a) is a frequency allocation diagram and (b) is a test code configuration diagram. Figure 1
In FIG. 3A, the curve S is the same as the curve S in FIG. 3A and shows the frequency characteristic of the detection sensitivity of the conventional certifier corresponding to the 1 GB disk. The frequency 2f _A of the test code for a 2 GB disc is 2/3 24 MHz of the highest usable frequency 2f ₂ = 36 MHz of the disc.
z. Frequency 2f _A is the inspectable frequency on the certification standard 2f ₁ = 18 MHz 4/3 = 1.33
This is equivalent to double, and as described above, the second harmonic wave is reproduced at a good level and the third harmonic wave is attenuated to some extent, so that the normal frequency 2f ₂ for a 2 GB disk is reproduced.
The medium is better tested than with = 36 MHz. Next, in FIG. 1 (b), the test code has a code configuration in which a basic pattern of "100" is continuous, and the phase of the bit "1" is cyclically shifted (a), (b) and (c). Then, the medium is inspected by sequentially writing / reading these three times. The reliability is improved by the inspection for three times and the bit "1" being written / read over the entire track. In this case, the time width Δ of each bit “1”
t _A is the 1 / 2f _A of the reciprocal of the frequency 2f _A, the repetition frequency of each bit 1.5f _A = 18MH
z becomes the certifier's inspectable frequency 2f ₁ =
It corresponds to 18 MHz, which is advantageous for waveform reproduction. In the above embodiment, the maximum usable frequency is 2 GB with 36 MHz.
However, in general, even if the maximum usable frequency of the medium exceeds the inspectable frequency specified by the certifier, the reliability of the test code can be improved by properly selecting the frequency according to the above. It is possible to perform a medium inspection with certainty. Note that the method of aligning the phase of the bit "1" for the above-mentioned three times of writing is easily performed by the conventional technique, and therefore the description thereof will be omitted.

[0007]

As described above, in the medium inspection method according to the present invention, the detection sensitivity characteristic of the certifier is such that the harmonics of the read signal are reproduced to some extent even at a frequency higher than the standard inspectable frequency. Focusing on the medium, the frequency of the test code is appropriately reduced from the maximum usable frequency for the medium whose maximum usable frequency exceeds the inspectable frequency in the standard of Certifier, and the inspection is performed. In this case, the medium is almost well tested using a test code of 24 MHz which is ⅔ of the highest used frequency, and the code configuration of the test code is
The number of inspections by this is improved to improve the reliability of the inspection. The effect of enabling reliable medium inspection by a conventional certifier on a disc having a recording capacity of 2GB or more is obtained. There is a big one.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) is a frequency arrangement diagram and (b) is a configuration diagram of a test code.

2A and 2B are explanatory views of a method of inspecting a magnetic disk by a certifier, where FIG. 2A shows a magnetic disk and a track, and FIG. 2B shows a configuration of a conventional test code.

3A and 3B are explanatory diagrams of problems in medium inspection of a magnetic disk having a recording capacity of 2 GB by a conventional certifier, where FIG. 3A is a frequency layout diagram and FIG. 3B is a waveform of a read signal.

[Explanation of symbols]

1 ... hard magnetic disk, just disk, tracks 1a ... disc, S ... the frequency characteristic curve of the detection sensitivity of the certification Ya, L _s ... normal level, L _R ... lowered level, 2f ₁ ... maximum operating frequency of 1GB of disk, 2f ₂ ... maximum usable frequency of ₂ GB disk, 2f _A ... frequency of test code in the present invention.

Claims (3)

[Claims] 1. In a certifier for writing / reading a test code to / from a track of a magnetic disk and inspecting the medium of the magnetic disk by the peak value of the read signal, the maximum usable frequency is based on the standard of the certifier. A method of inspecting a medium for a magnetic disk, wherein the frequency of the test code is appropriately reduced from the maximum usable frequency for inspecting the medium exceeding an inspectable frequency. 2. A testable frequency according to the standard of the certifier is set to 18 MHz, and the frequency of the test code is set to 2 / of the maximum usable frequency of 36 MHz for the magnetic disk whose maximum usable frequency of the medium is 36 MHz. 3. The magnetic disk medium inspection method according to claim 1, wherein the frequency is 3 to 24 MHz. 3. The medium according to claim 1, wherein a test code having a code structure in which a basic pattern of "100" is continuous is cyclically shifted bit by bit and written / read three times to inspect the medium. Magnetic disk medium inspection method.