JPS6333608A - Radius measuring apparatus - Google Patents

Abstract

PURPOSE:To prevent the lowering of measuring accuracy due to a difference in the center hole diameter of an optical disc, by matching the outer diameter of a support with the center hole diameter maintaining the level of the optical disc accurately. CONSTITUTION:A cylindrical housing 2 is erected on a base 1 and a rotor 4 is provided thereon through a bearing 3. A driving section 10 is arranged on the top of the rotor 4 to reciprocate a positioning pawl 11 with a driving source such as hydraulics to be introduced externally. When the eccentricity is measured, the pawl 11 is moved to make the circumferential diameter smaller than the center hole diameter of the optical disc 23. Then, the pawl 11 is opened gradually to bring an internally circumferential spacer 17 of the disc 23 into contact with a contact part 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radius measuring device suitable for measuring, for example, the concentricity of a recording track with respect to a center hole of a disk-shaped recording medium.

[Conventional technology]

In recent years, in recording and reproducing devices such as optical disk drives and magnetic disk drives, the track width has become narrower and the rotational speed of the recording medium has become faster in order to achieve higher recording density and faster access speed. There is a tendency to become

As the track width becomes narrower or the rotational speed of the recording medium increases, phenomena such as crosstalk between tracking signals and information signals, or off-track of the head tend to occur, making it difficult to record and reproduce signals correctly. It becomes difficult. In order to prevent such problems, it is necessary to precisely form the concentricity of the recording tracks with respect to the center of rotation of the recording medium. In order to research a recording/reproducing device that can form such highly accurate recording tracks, a radius measuring device that can accurately measure the concentricity of the recording track with respect to the rotation center of the recording medium is required.

FIGS. 5 and 6 show examples of the structure of a support provided in a conventionally known radius measuring device of this type.

In FIG. 5, 21 is a cylindrical support that supports the optical disk 23, 22 is a drive shaft that rotates the support 21, and 2
4 is a measuring device for measuring the true eccentricity between the center hole and the group.

During the measurement, the optical disk 23 is placed on a table formed on the top surface of the drive shaft 22 with one center hole of the optical disk 23 aligned with the support 21 . Next, the drive shaft 22 is rotated by a drive source such as a motor or manually, and the amount of displacement of the optical disk 23 from the center of the group is measured by the measuring device 24. This measures the eccentricity between the center hole of the optical disc and the group.

In FIG. 6, the support 21 is changed from a cylinder to a cone support 25. In FIG. As in the case of FIG. 5, the center hole of the optical disk 23 is inserted into the support 25, and the amount of eccentricity is measured in the same manner as described above.

[Problem that the invention seeks to solve]

However, among conventional radius measuring devices, those with cylindrical supports require a clearance X of about 20 μm in order to fit the center hole of the optical disk 23 into the support 21. Optical disc 2 for X
This causes an error in the centering of 3. Generally, the track pitch of an optical disk is about 1.6 μm, so if there is a centering error of 20 μm, it is impossible to accurately measure the amount of eccentricity.

Furthermore, since the optical disk 23 is likely to be tilted in the case of the conical support 25, it is difficult to measure the true eccentricity between the center hole and the group.

[Means for solving problems]

The present invention solves the problems of the prior art as described above, and makes it possible to simply determine the center of rotation of the object to be measured A, and to accurately measure the radius from this center of rotation to the recording track to be measured. In order to provide a radius measuring device, at least three positioning claws are arranged equally on the same radius with respect to the rotation center of the support body, and the positioning claws can be moved forward and backward by the same amount with respect to the rotation center of the support body. It is characterized by the following.

[Effect]

According to the above means, the positioning claw can be freely positioned in alignment with the center hole of the object to be measured, and a radius measuring device can be constructed without creating a clearance between the center hole and the positioning claw.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a partial sectional view showing an embodiment of the present invention, and FIG. 2 is a sectional view of an optical disk support section.

A cylindrical housing 2 is erected on a base 1, and a rotating body 4 is rotatably provided via a bearing 3.

The bearing 3 is arranged via a spacer 5.6 and a collar 7.8. A drive unit 10 is disposed above the rotating body 4, and uses hydraulic pressure, air pressure, etc. introduced from the outside as a drive source to reciprocate the positioning pawl 11 in the horizontal direction. Rotating body 4
A vibrator 12 for introducing hydraulic pressure or the like to the drive unit 10 is disposed inside the pipe 12, and a connector 13 is connected to the end of the pipe 12.

The positioning pawl 11 is formed in an L-shape as shown in FIG. 2, and a contact portion 18 that contacts the inner spacer 17 of the optical disk 23 is formed on the outside of the upright piece. In addition, 19
2 is a replica plate, and 20 is an outer peripheral spacer.

In the above configuration, when measuring the amount of eccentricity, the positioning pawl 11 is moved in advance to make its outer diameter smaller than the diameter of the center hole of the optical disc 23. Next, hydraulic pressure or the like is supplied to the drive section 10 to gradually open the positioning pawl 11 and bring the contact section 18 into contact with the inner peripheral spacer 17 of the optical disk 23.

Next, while rotating the rotating body 4, the amount of displacement from the center of the group of the optical disc 23 is measured by the measuring device 24, and the eccentricity of the center hole of the optical disc and the group can be measured.

The radius measuring device of the above embodiment can center the optical disk within ±
This can be done with an accuracy of 2 μm.

FIG. 3 is a partial sectional view showing another embodiment of the present invention, and FIG.
The figure is a sectional view taken along the line IV-IV in FIG. 3. A support body 31 having a conical upper portion is inserted into the drive unit 10 and moves up and down in response to hydraulic pressure. Three grooves 32 are formed at equal angles in the elongated direction of the conical portion of the support 31, and a 3-shaped positioning pawl 33 is slidably fitted into each groove 32. The inner surface of the groove 32 has an inclined angle to prevent the positioning pawl 33 from falling off. The bottom surface of the positioning claw 33 is placed on the base 34 and the support 31
As the support 31 rises, it moves away from the center of the support, and as the support 31 descends, it approaches the center of the support. That is, the positioning pawl 33 moves backward or forward toward the center of the support on the surface of the table 34 in conjunction with the upward and downward movements of the support 31.

In the above configuration, when measuring the amount of eccentricity, the support 3
1 is lowered, and the positioning claw 33 is moved toward the center of the support. Next, align the center hole diameter with the positioning claw 33,
The optical disc 23 is placed on the surface of the table 34. In this state, the support body 31 is gradually raised, and the positioning claws 33 are gradually opened to match the center hole of the optical disc 23.

Next, the rotating body 4 is rotated, and the amount of eccentricity is measured in the same manner as described above.

Incidentally, by providing a guide to support the optical disk so that the optical disk is always perpendicular to the rotation center, it is possible to eliminate vertical and downward vibrations when the optical disk rotates. This can eliminate measurement errors.

〔Effect of the invention〕

As explained above, according to the present invention, the outer diameter of the support part is made to match the diameter of the center hole while accurately maintaining the horizontal plane of the optical disc, which reduces the measurement accuracy due to the difference in the diameter of the center hole of the optical disk. It is possible to prevent this and measure eccentricity with high precision.

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing one embodiment of the present invention, FIG. 2 is a sectional view of an optical disk support, FIG. 3 is a front sectional view showing another embodiment of the invention, and FIG. IV-I in Figure 3
5 is a sectional view showing a conventional radius measuring device, and FIG. 6 is a sectional view showing another conventional radius measuring device. 1...Base, 2...Housing, 3
... Bearing, 10 ... Drive section, 1
1.33...Positioning claw, 12...Pipe, 23...Optical disc, 1 Base
10・Support mouth 41 and Iku 2・11 Ushino 2′11゜Kanfu 3, Bearshin 7°゛12・Ha6if 0 4 Rotation cz'13 Kookunu 5.6・Suhe 0-sa 23. Optical disc 7.8.7
7rah 24. 5 bows, Fig. 2 η Fig. 3 31 Shitsubofu 324 gin 331 sentence i Shiinu Meshi 34 tape [shi]

Claims (1)

[Claims] In a radius measuring device comprising a rotatable support on which an object to be measured is attached, and a measuring means for measuring a radius from the center of rotation of the support, at least three A radius measuring device characterized in that two positioning claws are arranged equally, and the positioning claws can be moved forward and backward by the same amount with respect to the center of rotation of the support.