JPH06131726A - Evaluation device for magneto-optical disk - Google Patents

Abstract

PURPOSE:To obtain an evaluation device for a magneto-optical disk provided with an adjusting mechanism capable of exactly evaluating the recording/ reproducing characteristic of the magneto-optical disk. CONSTITUTION:A spindle motor 13 driving a magneto-optical disk 1 is fixed on a feeding mechanism 15 in the Y direction. In order to exactly measure the recording/reproducing characteristic of the magneto-optical disk 1, skew adjustment on the YZ plane is performed making a laser light spot 16 the center of rotation by means of a first skew adjusting table 17 provided with a turn table 21 connected to an optical pickup 11 by a connector 24. Then, skew adjustment on the XZ plane is performed making the spot 16 the center of rotation by means of a second skew adjusting table 27 provided with a turn table 30. Also, a turn table 33 in the circumferential direction, making the spot 16 the center of rotation for adjusting the position of a three beam spots for tracking control, and an XY table 44 for adjusting the position of a magnetic head 12 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium evaluation device,
In particular, the present invention relates to a recording medium evaluation device suitable for evaluation of a small magneto-optical disk having a diameter of 64 mm.

[0002]

2. Description of the Related Art ROM disks (CD), MO disks, etc. have been proposed and put into practical use as data recording media, but in recent years, they are smaller than these disks and have a diameter of 64 mm. A recording medium in which a disc is housed in a cartridge has been proposed. This disc is a rewritable magneto-optical disc, and recording and reproduction will be briefly described below.

First, a recording method of the magneto-optical disk (hereinafter referred to as a disk) will be described with reference to FIG. As this recording method, a magnetic field modulation overwrite method is adopted as shown in FIG. This recording method is applied to the recording track area on the disc 1 which is desired to be rewritten.
By irradiating a laser beam of about mW, the magnetic film formed on the disk is cured at a Curie temperature (for example, about 180).
(° C) and above to extinguish the magnetization.

At this time, the objective lens 3 is sandwiched with the disc 1 in between.
The magnetic field of "N" or "S" is generated by reversing the direction of the current flowing through the magnetic head 2 provided on the opposite side of the optical pickup 4 composed of the same as above, in accordance with the data to be recorded. Then, the area to be rewritten on the disc 1 moves from the laser spot position as the disc 1 rotates,
When the temperature falls below the Curie temperature, the magnetic field of "N" or "S" corresponding to "1" or "0" of the data is recorded. In this recording method, in order to maintain the conventional recording time (up to 74 minutes), since the diameter of the disc is small, the recording is performed by using the audio compression technique based on the psychoacoustic minimum hearing limit characteristic and masking characteristic. .

On the other hand, as shown in FIG. 5 (A), the reproduction of the disk is performed by applying 0.5 to the magnetic signal recorded in the recording track on the disk 1 in the direction of "N" or "S".
When a laser beam of about mW is irradiated, the polarization plane of the return light slightly rotates in the forward or reverse direction due to the Kerr effect, corresponding to the N pole or the S pole. When the return light passes through the beam splitter 5 and the polarization beam splitter 6, if the polarization plane of the return light is in the positive direction, the distribution amount to the light receiving element A is larger than that to the light receiving element B. Therefore, the light amount difference (A-B) of the light receiving element is calculated by the calculation circuit 7, and the data is read depending on whether the result is positive or negative.

Conventionally, there is an error rate of bits recorded as a target for measuring and evaluating the recording characteristics of such a disc. This error rate has an error associated with a change in magnetic field and an error associated with a change in laser power, as is clear from the recording and reproducing methods of the disc. Then, when the error rate is measured and the disk is evaluated (220 pieces / second or less), the accuracy of the measuring mechanism has a great influence. The disk recording / reproducing apparatus includes an optical pickup 4, a magnetic head 2, a spindle motor (not shown), and a holding mechanism (not shown) for them. In this recording / reproducing mechanism, the disk surface and the optical axis of the optical pickup 4 must be orthogonal to each other when recording / reproducing.

Further, the optical pickup mechanism, the magnetic head, etc. provided in the measuring mechanism for evaluating the disk will affect the measuring accuracy unless the skew is optimally adjusted accurately with respect to the disk surface to be evaluated. The reliability of the signal obtained cannot be obtained. That is, the degree of adjustment of the measurement mechanism causes a measurement error.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a magneto-optical disk evaluation apparatus having an adjusting mechanism capable of accurately evaluating the recording / reproducing characteristics of the disk.

[0009]

The present invention comprises an optical pickup and a magnetic head, and records a predetermined data on a magnetic film formed on the disk by irradiating a laser beam spot from the optical pickup. In the evaluation device, first and second skew adjusting swivel tables connected to the optical pickup for rotating an optical axis of the optical pickup in two directions orthogonal to each other with the laser light spot as a center of rotation; The magneto-optical disk evaluation apparatus is configured by providing a table for moving the optical pickup in a direction orthogonal to the pickup feed direction and an XY table for moving the magnetic head in parallel.

[0010]

[Embodiment] As is clear from the description of the above problems, the disk evaluation mechanism is designed so that the shaft runout of the spindle motor, the surface runout of the disk chucking portion, the surface runout eccentricity of the disk, etc. do not affect the measurement. The optical pickup of the evaluation device requires a focus servo and tracking servo mechanism, and a mechanism for keeping the distance to the disk constant in the magnetic head mounting part. Especially, the signal measured for the first time is accurately adjusted by skew adjustment. It is possible to improve reliability.

A specific example of the disk evaluation apparatus of the present invention will be described below with reference to FIGS. 1, 2 and 3. FIG. 1 is a side view of the evaluation device, FIG. 2 is a plan view thereof, and FIG. 3 shows an example of a skew adjustment table constituting the present invention. The disk evaluation device 10 is basically the same as the recording / reproducing device, and includes an optical pickup 11, a magnetic head 12, a spindle motor 13, and a disk clamper 1 for fixing a disk.
4. The disk drive mechanism 15 driven by the table drive motor 38 is provided. This disc feeding mechanism 15
It is composed of a fixed table 47 fixed to the base 46 and a Y-direction movable table 48 mounted on the fixed table 47 and having the spindle motor 13 attached thereto.

In particular, the evaluation apparatus of the present invention is provided with the following adjusting mechanism in order to remove the influence of the skew and the like on the evaluation. First, this adjusting mechanism will be described. The skew adjustment mechanism of this evaluation apparatus is adjusted with a laser light spot 16 (hereinafter referred to as spot 16) irradiated from the objective lens 3 of the optical pickup 11 onto the surface of the disk 1 as the center of rotation. Further, in order to measure the disc, a reference disc is prepared and adjustment is performed manually as described below.

As the reference disc, surface wobbling,
Prepare a disk made of a glass substrate that does not cause "warpage". Recording / reproduction is performed on a glass disk having no “warpage” as a reference, and the optical axis position where the maximum amplitude of the RF signal is detected, that is, the angle between the surface of the disk 1 and the optical axis is 9
The optical pickup 11 of the evaluation device is adjusted so as to be 0 degree. Below, an adjustment mechanism capable of accurately performing this optimum position adjustment will be described.

The skew of the optical pickup 11 is basically adjusted to the optimum position with respect to the surface of the reference glass disk, that is, the optical axis thereof is vertical and the spot 16 is irradiated on the disk surface without tilting. Thus, the spot 16 is adjusted as the center of rotation. In order to eliminate the inclination of the optical axis with respect to the disk surface, basically two adjustments are made. Where the disc is in the XY plane,
The feeding direction of the optical pickup 11 is the Y axis, and the direction of the optical axis having no skew is the Z axis. And the spot 16
Will be described as being at the origin of the coordinates.

First, the first is YZ for a disc.
Manually adjust the skew on the surface. 17 is a first skew adjustment table for manually performing the first skew adjustment,
As shown concretely in FIG. 3, the table 17 can be manually adjusted by a knob 18, and a scale 1 that serves as a guide for the adjustment.
It is provided with two tables denoted by 9, and one of these surfaces has a curved structure. Table 1
7 is composed of a swivel table 21 having a curved surface aligned with the curved surface of the fixed table 20, which slides on the fixed table 20 having the curved surface formed therein. The turning table 21 slides and turns so as to draw an arc around the spot 16 by rotating the knob 18 manually.

Returning to FIG. 1 and FIG. 2, reference numeral 23 is a housing for accommodating an optical device such as a beam splitter constituting the optical pickup 11 and having a reference plane 22 (XY plane) of the optical system. Interlocks with the turning of the turning table 21.

Reference numeral 24 denotes a connecting body for connecting the housing 23 and the turning table 21. The connecting body 24 is fixed to the reference surface 22 of the housing 23 with a screw or the like, and the flat portion 25 of the turning table 21 (see FIG. 3). ) Fixed. And the knob 18
When the revolving table 21 is driven with, the casing 23 is interlocked with the connecting body 24, and revolves around the spot 16 in the YZ plane. As a result, the optical axis is also interlocked to rotate in the YZ plane with the spot 16 as the center of rotation,
Optimal adjustment (skew adjustment) of the optical axis of the optical pickup 11 can be performed. After the adjustment is completed, the clamp knob 26 (C in FIG. 3) is used for clamping.

The first skew adjustment of the optical axis is the adjustment of the inclination of the optical axis on the YZ plane with respect to the disc, while the second skew adjustment of the optical axis is on the XZ plane orthogonal to the YZ plane. Is performed as follows. Reference numeral 27 is a second skew adjustment table having the same structure as the first skew adjustment table 17, and is manually adjusted by the knob 28. The second skew adjustment table 27 is composed of a fixed table 29 and a swivel table 30 which slides on the dovetail. The swivel table 30 is connected to the fixed table 20 of the first skew adjustment table 17 by a connecting body 31. ing.

The swivel table 30 swivels in a direction orthogonal to the swivel direction of the swivel table 21 of the first skew adjusting table 17, and the optical pickup 1
The skew adjustment of the optical axis on the XZ plane 1 is performed. After that, the clamp is performed as in the first skew adjustment. As described above, the first skew adjustment table 17 and the second skew adjustment table 27 are used to manually perform the first and second skew adjustments on the YZ plane and the XZ plane of the optical axis of the optical pickup 11. Complete the adjustment.

Next, in addition to the above-mentioned two skew adjustments, the following adjustments are necessary for measuring the disk,
The adjusting mechanism will be sequentially described. The three-beam method is adopted for the tracking adjustment of the proposed disk. Therefore, it is necessary to adjust so that the spot (main beam spot) 16 serving as the center of rotation is located directly above the recording track and the tracking control beam spot is located directly above the control track.

In order to perform this spot position adjustment, the evaluation apparatus of the present invention is provided with a circumferential turning table 32 for rotating the optical pickup 11 in the XY plane in the disc circumferential direction. The circumferential turning table 32 is attached below the second skew adjusting table 27,
The optical reference plane (X
It turns in parallel with the (Y plane) 22.

The circumferential turning table 32 has a turning table 33 having a curved surface on its inner surface and a fixed table 34.
It consists of two dobles that slide on each other. The turning table 33 is fixed to the fixed table 29 of the second skew adjustment table 27. Then, the protrusion 34 that interlocks with the swivel table 33 is driven by the knob 35 to swivel the optical pickup 11 in the circumferential direction with the spot 16 as the center of rotation, and the position of the three-beam spot is optimally adjusted. Clamp at 36. A spring (not shown) that biases the protrusion 34 is housed inside the clamper 36, and the adjustment in the circumferential direction is performed by the knob 35 against the spring.

Next, a straight line 37 passing through the center of the disk 1
(FIG. 2) The spot 16 which is the center of rotation rides on the
In order to match the moving direction of the movable table 48 which is driven by the table drive motor 38 and moves in the Y direction, an X table 40 (FIG. 1) which can be manually adjusted by the knob 39 is provided in a direction (X direction) orthogonal to this. . After the completion of the adjustment in the X direction, the knob 41 clamps.

Further, there is provided a magnetic head (recording head) 12 which applies a magnetic field during recording on the disk. The core 2 (B in FIG. 5) of the magnetic head 12 is mounted and fixed on an XY table 44 that can be manually adjusted by the knobs 42 and 43 so that the center of the core 2 (B in FIG. 5) is at the optimum position for recording. Reference numeral 45 denotes a magnetic head circuit mounting substrate attached to the XY table 44.

The structure of the disk evaluation apparatus of the present invention has been described above. The evaluation apparatus is controlled as follows. So that the optimum signal can be read from the disc,
The evaluation device 10 in which the adjustment of the skew and the like of the optical pickup 11 has been completed using the reference glass disk.
Then, the recording / reproducing characteristics of the disk to be measured are measured and evaluated by the system shown in the block diagram of FIG.

In the system shown in FIG. 4, the operator inputs data from the keyboard 49 according to a menu screen on a CRT (not shown). The host computer 50 analyzes the input information and sends a command to the system controller 51. The system controller 51 analyzes the command and sends the command to the drive controller 52. The drive controller 52 analyzes the command and drives the actuator drive device 5 incorporated in the optical pickup 11 (FIG. 1).
3 is controlled and measurement is performed.

The measured signal is sent to the host computer 50 or the external measuring instrument 57 such as the spectrum analyzer 54, the digital oscillograph 55 and the function generator 56 through the system controller 51 through the measuring instrument interface GPIB, and the quality of the disc is judged. Make an evaluation decision.

[0028]

According to the present invention, skew adjustment, tracking servo mechanism adjustment, and magnetic head position adjustment can be precisely performed. As a result, recording / reproducing of a disk such as RF signal characteristics such as pit / groove modulation degree, servo signal characteristics such as tracking servo signal, substrate optical characteristics such as recording film reflectance, recording characteristics such as magnetic field strength vs. block error rate, etc. It becomes possible to take out highly reliable data on the characteristics and to accurately evaluate and judge the recording / reproducing characteristics and the like.

Further, the quality of the disc can be kept constant by making an evaluation judgment based on the data obtained by the measuring instrument of the present invention, and the compatibility of each production facility and the compatibility of each manufacturer can be ensured. Will be easier.

[Brief description of drawings]

FIG. 1 is a side view of an evaluation device of the present invention.

FIG. 2 is a plan view of the evaluation device of the present invention.

FIG. 3 is a diagram showing a skew adjustment table.

FIG. 4 is a block diagram of a control unit of the evaluation device of the present invention.

FIG. 5 is an explanatory diagram of a recording / reproducing system of a magneto-optical disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 11 Optical pickup 12 Magnetic head 13 Spindle motor 15 Disk feed mechanism 16 Laser light spot used as a rotation center 17 First skew adjustment table 21, 30 Skew adjustment swivel table 24 Coupling body 27 Second skew adjustment table 32 Circumferential turning table 38 Disk feed mechanism drive motor

Claims (4)

[Claims] 1. A magneto-optical disk evaluation apparatus comprising an optical pickup and a magnetic head, wherein predetermined data is recorded on a magnetic film formed on a disk by irradiating a laser beam spot from the optical pickup. Magneto-optical disk evaluation, characterized in that first and second skew adjusting turning tables connected to the optical pickup for rotating the optical axis in two directions orthogonal to each other with the laser light spot as a rotation center are provided. apparatus. 2. The magneto-optical disc evaluation apparatus according to claim 1, further comprising a table for moving the optical pickup in a direction orthogonal to the optical pickup feed direction. 3. A magneto-optical disc evaluation apparatus comprising an optical pickup and a magnetic head, wherein predetermined data is recorded on a magnetic film formed on a disc by irradiating a laser beam spot from the optical pickup. XY for moving the optical head in parallel with the first and second skew adjusting turning tables connected to the optical pickup, which rotate the optical axis in two directions orthogonal to each other with the laser light spot as the center of rotation.
A magneto-optical disk evaluation apparatus provided with a table. 4. A magneto-optical disc evaluation apparatus comprising an optical pickup and a magnetic head, wherein predetermined data is recorded on a magnetic film formed on a disc by irradiating a laser beam spot from the optical pickup. First and second skew adjusting turning tables connected to the optical pickup for rotating an optical axis in two directions orthogonal to each other with the laser light spot as a rotation center, and in a direction orthogonal to the optical pickup feed direction. A magneto-optical disk evaluation apparatus comprising a table for moving the optical pickup in parallel and an XY table for moving the magnetic head in parallel.