JP3087389B2 - Magneto-optical disk inspection apparatus and method of selecting magneto-optical head used therein - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical disk inspection apparatus for inspecting the characteristics of a magneto-optical disk and a method of selecting a magneto-optical head used for the apparatus.

[0002]

2. Description of the Related Art Magneto-optical discs have attracted attention for use as storage devices in computer systems instead of magnetic discs, floppy discs, and the like, and therefore require particularly long life and high reliability. For that purpose, inspection of the magneto-optical disk at the shipping stage is an important point.

Conventionally, a magneto-optical disk inspection apparatus inspects a magneto-optical disk using one recording / reproducing head, but recently, a magneto-optical disk using a plurality of, for example, four recording / reproducing heads. A disk inspection device has been realized.
In this magneto-optical disk inspection apparatus, a track of the magneto-optical disk is divided into an inner circumference and an outer circumference, and two recording / reproducing heads are arranged on each of the tracks. Further, by using the two arranged recording / reproducing heads separately for recording and reproducing, the inspection time is significantly reduced as compared with a conventional magneto-optical disk inspection apparatus which performs inspection with one magneto-optical head. It has the advantage that it can be shortened.

[0004]

However, since there are a plurality of recording / reproducing heads used in a magneto-optical disk inspection apparatus, there is a problem of variations in performance. For example, recording / reproducing is performed on a standard magneto-optical disk for measuring the characteristics of the recording / reproducing head, and the bit error rate (BER) is examined. It can be seen that there is variation.

In order to suppress the variation in BER between the four recording / reproducing heads used in this magneto-optical disk inspection apparatus, the recording power of a good recording / reproducing head having a low BER is deliberately deviated from an optimum value. Although the variation between the four recording / reproducing heads of the magneto-optical disk inspection apparatus has been reduced by adjusting to another recording / reproducing head having a high BER, the recording power adjustment range of the recording / reproducing head is reduced in this method. In addition, a good recording / reproducing head having a low BER cannot be used at an optimum recording power, and thus has a problem in stability. Further, in the above method, even if the same magneto-optical disk is inspected by a plurality of magneto-optical disk inspection devices, the BER varies, and the BER value of the magneto-optical disk inspected by each magneto-optical disk inspection device is changed. However, there is also a problem that is different.

SUMMARY OF THE INVENTION It is an object of the present invention to enable a recording / reproducing head to be used with an optimum recording power, and even if the performance of the recording / reproducing head varies, a bit error rate of a magneto-optical disk generated between magneto-optical disk inspection devices. It is an object of the present invention to provide a magneto-optical disk inspection apparatus capable of reducing variations in the optical disk, and a method of selecting a magneto-optical head used for the apparatus.

[0007]

The above object is achieved by a plurality (n).
Comprising a magneto-optical head capable of recording / reproducing of the individual), one that
Part (m) is used exclusively for recording, and the rest (nm) are reproduced
In the magneto-optical disk inspection apparatus for inspecting characteristics of the magneto-optical disk using the private, the plurality of magneto-optical head
Chi, with a bit error rate and the previous SL magneto-optical disk obtained by reproducing the magneto-optical disk in advance signal is recorded
In order from the large most <br/> difference between a preset reference bit error rate Te, the recording of m of said magneto-optical head dedicated
This is achieved by a magneto-optical disk inspection apparatus characterized in that the apparatus is used for inspection.

[0008] The above-described object, in the selected way to select a magneto-optical head capable of recording / reproducing is to be used in the magneto-optical disk inspection apparatus for inspecting characteristics of the magneto-optical disk as a recording-only head or a read-only head, The signal is recorded in advance.
Comparing the preset <br/> reference bit error rate bit error rate obtained by reproducing the recorded optical disk with respect to the magneto-optical disk, as the difference between the reference bit error rate is largest Number required in order from
This is achieved by a method for selecting a magneto-optical head used in a magneto-optical disk inspection apparatus, wherein only a recording-only head is selected.

[0009]

According to the present invention, each recording / reproducing head can be used in an optimum state, so that the stability of the magneto-optical head can be improved. Variations in the bit error rate of the magneto-optical disk existing between the magnetic disk inspection devices can be reduced.

[0010]

FIG. 1 shows a magneto-optical disk inspection apparatus according to an embodiment of the present invention and a method of selecting a magneto-optical head used in the apparatus.
This will be described with reference to FIGS. 1A and 1B are a plan view and a cross-sectional view of a main part of the magneto-optical disk inspection device of the present embodiment.

The magneto-optical disk 1 to be inspected is mounted on a rotating shaft of a spindle motor 2 and fixed from above by a clamper 4. The inspection area of the magneto-optical disk 1 is divided into an outer peripheral area P and an inner peripheral area Q on the disk surface. On the lower surface side of the magneto-optical disk 1, four recording / reproducing heads 6a to 6d are provided. Each head 6a-6d
Are provided with linear motors 8a to 8d.
a to 6d are linearly driven in the radial direction of the magneto-optical disk.

As a means for applying a magnetic field to the magneto-optical disk 1, an elongated permanent magnet 1 extending in the radial direction is provided on the upper surface side of the magneto-optical disk 1 facing the recording / reproducing heads 6a to 6d.
0a to 10d are provided. These permanent magnets 10a
10 to 10d are magnet holding portions 4 extending from the center of the clamper 4.
a to 4d. FIG. 2 shows details of the recording / reproducing head 6a mounted on the magneto-optical disk inspection apparatus of the present embodiment. Since the recording / reproducing heads 6b to 6d are the same, illustration is omitted. The laser light emitted from the laser light source 12 is made parallel by the collimator lens 14 and shaped by the shaping prism 16. The shaped laser light is
The light is converted into linearly polarized light by the polarizer 18 and is incident on the objective lens 22 via the half mirror 20. The objective lens 22 is driven following the movement of the magneto-optical disk 1.

When data is reproduced, the reflected laser light whose polarization plane is Kerr-rotated in accordance with the magnetization direction of the magneto-optical disk 1 is reflected by the half mirror 20 and is incident on the analyzer 24, and the laser light is reflected in accordance with the Kerr rotation angle. The emitted laser light is incident on the light detector 26. The magnetization direction of the magneto-optical disk 1 is detected based on the output signal of the optical detector 26. When recording data, a permanent magnet
By irradiating and heating a laser beam while applying a magnetic field according to 10a, the magnetization direction of the magneto-optical disk 1 is reversed to record.

The magneto-optical disk inspection apparatus of this embodiment has two recording / reproducing heads for the inspection areas P and Q of the magneto-optical disk 1 to be inspected among the four recording / reproducing heads 6a to 6d. Are arranged, and one of the two recording / reproducing heads arranged in each area is used as a recording-only head, and the other is used as a reproducing-only head, so that the magneto-optical head is provided by the recording-only head. The characteristics of the magneto-optical disk 1 are inspected by reading data written on the disk 1 with a read-only head.

A method of selecting the four recording / reproducing heads 6a to 6d mounted on the magneto-optical disk inspection apparatus as a recording-only head or a reproducing-only head will be described with reference to FIG. FIG. 3 is a diagram showing recording / reproducing characteristics of a plurality of magneto-optical heads used in one embodiment of the present invention. The method of selecting a magneto-optical head according to the present embodiment uses a standard magneto-optical disk to perform recording and reproduction using each of the recording / reproducing heads 6a to 6d, and a bit error rate (BER).
Is measured, the recording / reproducing characteristics of each of the recording / reproducing heads 6a to 6d are grasped from the measured BER variation, and the optimum reproducing-only head is selected by evaluation.

First, reproduction characteristics of each of the recording / reproduction heads 6a to 6d are obtained. Using a standard magneto-optical disk on which data is recorded by a specific recording head, the data of the standard magneto-optical disk is reproduced by each of the four recording / reproducing heads 6a to 6d, and the four recording / reproducing heads 6a 6d, the bit error rate (BE) of the standard magneto-optical disk
R) is measured.

Multiple (n) magneto-optical disk inspection devices
In some cases, using the same standard magneto-optical disk, the BER is measured for a total of 4n of the four recording / reproducing heads 6a to 6d mounted on each magneto-optical disk inspection device. The reference BER of the standard magneto-optical disk is determined using the measured four or 4n BERs. If there are a plurality of magneto-optical disk inspection devices, the reference BER of the standard magneto-optical disk
Is determined, the machine difference (variation) between the magneto-optical disk inspection devices can be reduced.

FIG. 3A shows measured reproduction characteristics of each head. In the present embodiment, the BER of a standard magneto-optical disk is determined for a total of 24 recording / reproducing heads of six magneto-optical disk inspection devices (1st to 6th units) equipped with 4 recording / reproducing heads 6a to 6d. Measured. FIG.
The horizontal axis of (a) indicates the measured head number of the magneto-optical head. For example, the head number 16a indicates the recording / reproducing head 6a of the first magneto-optical disk inspection apparatus, and the head number 16b indicates the recording / reproducing head 6b.
The vertical axis in FIG. 3A indicates the bit error rate (BER).

The standard magneto-optical disk used for the BER measurement is a magneto-optical disk having a diameter of 130 mm (5.25 inches). The number of tracks of this magneto-optical disk is 1875.
1 track, 31 sectors per track,
The number of bytes per sector was 660 bytes, and predetermined 500 tracks of this standard magneto-optical disk were used as a measurement area.

FIG. 3A shows that the recording / reproducing head B
It can be seen that the reproduction characteristics evaluated by the ER have variations both within the magneto-optical disk inspection device and between the magneto-optical disk inspection devices. From the measured BER, the reference BER value at the time of reproduction was set to 7.0 × 10 ⁻⁶ . Next, the recording characteristics of each of the recording / reproducing heads 6a to 6d are obtained. Each record /
Using a specific standard magneto-optical disk for determining the recording characteristics of the reproducing heads 6a to 6d, the four recording / reproducing heads 6 of the magneto-optical disk inspection device are used for the standard magneto-optical disk.
Recording is performed by one of the heads a to 6d. The data written on the standard magneto-optical disk is reproduced by a specific reproducing head, and the BER of the standard magneto-optical disk is measured.
Hereinafter, the BER of the standard magneto-optical disk by the remaining three heads is measured in the same manner.

Multiple (n) magneto-optical disk inspection devices
In some cases, record on the same standard magneto-optical disk,
The BER for each of the four recording / reproducing heads 6a to 6d mounted on each magneto-optical disk inspection device is measured, and the measured four or 4n BERs are used to record the standard magneto-optical disk during recording. Determine the reference BER. FIG.
(B) shows the measured recording characteristics of the recording / reproducing heads 6a to 6d. The units on the vertical and horizontal axes are the same as those in FIG. 3A showing the reproduction characteristics.

The recording characteristics of the recording / reproducing head are as follows.
It can be seen that there is little variation in the reproducing heads 6a to 6d, and a substantially constant BER is obtained between the magneto-optical disk devices. FIG. 3B shows that when data is recorded on the magneto-optical disk, almost the same BER can be obtained using any of the recording / reproducing heads 6a to 6d as the recording head. Also, from FIG. 3A, it can be seen that when data is read from the magneto-optical disk, when the recording / reproducing heads 6a to 6d are used as reproducing heads, the BER variation among the heads is large.

That is, there is no problem in using any of the recording / reproducing heads 6a to 6d as the recording head. Of the four recording / reproducing heads 6a to 6d, BE with respect to the reference BER value
The two recording / reproducing heads whose R values deviate greatly were selected as recording-only heads, and the remaining two recording / reproducing heads were selected.
If the reproducing head is used as a reproducing-only head, B measured by the remaining two recording / reproducing heads
The average value of the ER approaches the value of the reference BER, so that the reproduction characteristics can be improved.

A specific description will be given by using the magneto-optical disk inspection apparatus of the third unit. Four recording / reproducing heads 36a-
36d (corresponding to 6a to 6d in FIG. 1), the recording / reproducing head whose BER value was measured as a reproducing characteristic greatly deviated from the reference BER value (7.0 × 10 ⁻⁶ ). If the recording / reproducing head 36b whose BER value deviates greatly next to the recording / reproducing head 36b is selected as the recording-only head, and the remaining recording / reproducing heads 36a and 36d are used as the reproducing-only heads, the two reproducing-only heads 36a , 36
The average value of the BER according to d can be made closer to the value of the reference BER.

In the magneto-optical disk inspection apparatus shown in FIG. 1, the recording / reproducing heads 6a and 6b form a set,
A set is composed of the reproducing heads 6c and 6d. An area P outside the magneto-optical disk 1 is assigned to a set of the recording / reproducing heads 6a and 6b, and an area Q inside the magneto-optical disc 1 is assigned to a set of the recording / reproducing heads 6c and 6d. Then, the recording / reproducing head 6a for inspecting the area P is used as a reproducing-only head, and the recording / reproducing head 6b is used as a recording-only head. Further, the recording / reproducing head 6d for inspecting the area Q is used as a reproducing-only head, and the recording / reproducing head 6c is used as a recording-only head.

By doing so, the inspection time can be halved by simultaneously performing the inspection of the area P and the inspection of the area Q which the magneto-optical disk inspection apparatus of this embodiment basically has. By making the BER obtained by the recording / reproducing head close to the reference BER, it is possible to reduce the machine difference between the magneto-optical disk inspection devices and perform highly reliable inspection.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, in the present embodiment, the present invention is applied to a magneto-optical disk inspection device equipped with four recording / reproducing heads. However, the present invention is applied to a magneto-optical disk inspection device having two or more recording / reproducing heads. The present invention can also be applied to the present invention.

[0028]

As described above, according to the present invention, each recording /
Since the magneto-optical head can be selected so that the reproducing head is used in an optimum state, the stability of the apparatus is improved, and the recording /
It is possible to realize a magneto-optical disk inspection apparatus capable of measuring the bit error rate of a magneto-optical disk to be inspected without depending on the fluctuation of the performance of the reproducing head while suppressing the fluctuation between the inspection apparatuses.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magneto-optical disk inspection device according to one embodiment of the present invention.

FIG. 2 is a diagram showing a magneto-optical head used in one embodiment of the present invention.

FIG. 3 is a diagram showing recording / reproducing characteristics of a plurality of magneto-optical heads used in one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magneto-optical disk 2 ... Spindle motor 4 ... Clamper 4a-4d ... Magnet holding part 6a-6d ... Recording / playback head 8a-8d ... Linear motor 10a-10d ... Permanent magnet 12 ... Laser light source 14 ... Collimator lens 16 ... Shaping Prism 18 ... Polarizer 20 ... Half mirror 22 ... Objective lens 24 ... Analyzer 26 ... Optical detector

Claims (3)

(57) [Claims] A plurality of (n) magneto-optical heads capable of recording / reproducing, a part (m) of which is used exclusively for recording,
In the remainder (n-m number of) optical disk inspection apparatus for inspecting characteristics of the magneto-optical disk with the reproduction-only, among the plurality of magneto-optical head reproduces the magneto-optical disk in advance signal is recorded pre with a bit error rate and the previous SL magneto-optical disk obtained Te
In order of difference has the most large <br/> the order set reference bit error rate, the m-number of the magneto-optical head to record only
A magneto-optical disk inspection device characterized by being used . 2. A selection method you select <br/> magneto-optical recording / reproducing magneto-optical head that uses the characteristics of the disk to a magneto-optical disk inspecting apparatus for inspecting a recording-only head or a read-only head, It is obtained by reproducing a magneto-optical disk on which signals have been recorded in advance.
That the bit error rate and pre for the magneto-optical disk
Compares the reference bit error rate that is fit set, or not a difference between said reference bit error rate is largest
A method for selecting a magneto-optical head for use in a magneto-optical disk inspection apparatus, wherein a required number of heads are selected as recording-only heads in order . 3. A magneto-optical head capable of recording / reproducing 2n recording / reproducing data, wherein an inspection area of a magneto-optical disk to be inspected is divided into n divided areas, and n of the 2n magneto- optical heads are divided into n divided areas. It was a recording-only head, as the remaining n pieces of read-only head, arranged one not a one of said playback-only head and the recording-only head, respectively to said n pieces of divided areas,
A method for selecting a magneto-optical head for use in a magneto-optical disk inspection device for inspecting characteristics of the magneto-optical disk by reading data written on the magneto-optical disk by the recording-only head by the read-only head, reproduces the data of the magneto-optical disk in advance signals are recorded by a particular recording head in each of the 2n pieces of the magneto-optical head, SL before for each of the 2n pieces of the magneto-optical head
The bit error rate of the optical disk is measured to determine a reference bit error rate before the SL optical <br/> magnetic disk using the 2n bit error rate that is measured, among the 2n pieces of the magneto-optical head , The reference bit error
The n number of magneto- optical heads are selected as the recording-only heads in order from the one with the largest difference between the bit error rate value and the bit rate , and the remaining n magneto- optical heads are used as the read-only heads. A method of selecting a magneto-optical head for use in a magneto-optical disk inspection apparatus, wherein the average value of the bit error rate measured by the read-only head is close to the value of the reference bit error rate. .