JPS60227105A - Measuring instrument for surface deflection - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an apparatus for optically measuring surface runout of a rotating disk.

[Background of the invention]

Conventionally, capacitance-type micro-displacement meters have been generally used to measure the surface runout of nine-rotation disks, but the surface to be measured must be made of a conductive material, and the glass disk must be made of a material such as Te. It is not possible to measure the surface runout of a rotating disk or the like on which a non-conductive material is deposited. In order to remove such restrictions on the material of the surface to be measured, the present invention uses light as a probe for measuring surface runout.

[Purpose of the invention]

An object of the present invention is to have a simple configuration, and to easily adjust the measurement range and measurement sensitivity according to the magnitude of surface runout of the surface to be measured.
Moreover, it is an object of the present invention to provide a highly reliable surface runout measuring device.

[Summary of the invention]

First, the principle of the present invention will be explained using FIG.

In FIG. 1, 1 is a disk rotating around 3 in the direction of the arrow. A light beam 100 is incident approximately perpendicularly to the surface of the disk 1 and is reflected at a point 10. Normally, the reflected luminous flux 20
0 points in a different direction from the incident light beam 100 depending on the direction of the surface at point 10. Now, take point 10 as the origin and draw X as shown in Figure 1.

Take the y and z axes. That is, or the direction of rotation at point 10, y is the direction of the radius, and 2 is the direction of the axis of rotation of the disk 1. If the angle between the tangent surface at point 10 and the There is a relationship called x. If the disk with radius r is rotating at a constant angular velocity ω, then dz 1 dz On the other hand, if the deflection angle in the X-axis direction of the reflected light beam 200 is θ, then 0=29, so dz θ −= r ω “ tan − dt 2 .Here, for a sufficiently small deflection angle, dz r
ω θ dt 2 Therefore, the magnitude Z of the vertical deviation is given by ω θ dt 2 . Further, the vertical vibration acceleration α is given by:

In this way, by measuring the angle θ of the reflected light beam 200, it is possible to know the magnitude and acceleration of vertical vibration.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples. FIG. 2 is a configuration diagram showing an embodiment of the measuring device according to the present invention. In the figure, 1 is a rotating disk, and 2 is a surface to be measured. 3 is a rotation center, and 4 is a motor for rotating the disc 1.

5 is a light source that emits a substantially parallel light beam, for example, He −
It is a Ne laser or a semiconductor laser. The parallel light beam emitted from the light source 5 is reflected by the polarizing prism 6, directed in a direction substantially perpendicular to the surface 2 of the disk 1, and passes through the λ/4 plate 7.
It is incident on point 10 on surface 2. The reflected light beam whose direction is slightly changed according to the direction of the surface at the point 10 is reflected by the λ/4 plate 7.
, passes through the deflection prism 6 and enters the light spot position detector 8. In the light spot position detector 8, current flows through the output terminals 2OA and 20B depending on the position 9 of the reflected light beam 200, and a voltage is generated by the resistor R.

Normally, at the center of the light spot position detector 8, X=O), and if the current sensitivity of the light spot position detector 8 is α. The amount of displacement X of the light beam 200 is
If the deflection angle is θ (according to the definition in FIG. 1) and the distance from the measurement point 10 to the light spot position detector 8 is θ, then when O is sufficiently small, x=Q θ.

If the rotational speed of the measuring disk is ω and the radius of the measuring point 10 is r', then according to the principle described above, the time differential of the vertical deflection amount 2 of the measuring surface 2 of this disk is dt, 2 11Rα The flow component is If we simply integrate it, we can see that the cause of the occurrence is a slight inclination of the incident beam 100, a slight deviation in the position adjustment of the light spot position detector 8, etc., and the DC component is completely OK. It's almost impossible. It is necessary to take out only such items.

Fig. 3 shows the amount of vertical deflection,
and the circuit configuration for detecting vertical vibration acceleration. Third
In the figure, numeral 21 is a differential amplifier, which is a circuit that generates the voltage V mentioned above. 22 and 23 are a so-called differential circuit whose purpose is to cut the DC component using a capacitor and a resistor, but the time constant 1/RC must be set to be sufficiently larger than the rotation period of the measuring disk. This output 30
A represents the speed fluctuation of the amount of vertical runout.

24 and 25 are an integrating circuit and a differentiating circuit, respectively, and 30B and 30C provide outputs proportional to the amount of vertical vibration and the vertical vibration acceleration. The respective proportionality constants are r, ω, Q, R, and α.

and rotation constant, all of which can be calculated from known quantities. That is, according to this embodiment, the absolute value of the amount of vertical vibration and the acceleration of vertical vibration can be easily measured.

In addition, in order to eliminate the effects of uneven reflectance on the measurement surface 2 and fluctuations in the intensity of the light source 5, the circuit shown in FIG. 4 is used. That is, in FIG. 4, the output voltage V of 20A and 20B,
2o, V'2o (7) This is a circuit that takes out the difference VA white AB and the sum ■1 from the terminal Du using the differential amplifier 21 and the adder circuit 26 to output V which is proportional to V+. It is used in place of the differential amplifier 21. (2) Since + is proportional to the amount of light beam 200 due to the characteristics of the optical position detector 8, it is completely unaffected by uneven reflectance and changes in the intensity of the light source. In addition, in this way, even when measuring the vertical runout of a disk with different types of vapor deposited films on the surface to be measured 2, there is no need to correct the measured value due to the difference in reflectance, and any Even in the case of a disc, the absolute value of the amount of vertical deflection and the vertical deflection acceleration can always be obtained.

〔Effect of the invention〕

As described above, according to the present invention, since the surface runout of the rotating disk is measured using light, there are few restrictions on the material of the surface to be measured, and since the alternating current component from the detector output side is used, the speed of incident light is If the device is tilted, it is resistant to misalignment of the light spot position detector and can perform highly reliable surface runout measurements with an easily adjustable device.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a configuration diagram of an embodiment of the present invention, and FIG. : A configuration diagram showing a circuit for calculating vertical vibration acceleration. FIG. 4 is a configuration diagram showing a circuit that eliminates the effects of uneven reflectance of the surface to be measured and changes in the amount of light from the light source. 1st

Claims (1)

[Claims] ■A light source that emits a nearly parallel beam; a light spot position detector that outputs a signal according to the illumination position of the incident beam; , an optical system that guides the reflected light flux from the surface to be measured to the light spot position detector, a circuit that extracts an alternating current component of the output of the detector at the light spot position, and an integral value and/or differential value of the alternating current component. A device for measuring surface runout of a rotating disk, characterized in that it is equipped with a circuit for taking out the information.