JPS58122410A - Surface shape measuring method - Google Patents

Abstract

PURPOSE:To converge laser light to a body surface and to utilize it as a signal which shows the shape of the body surface by irradiating a moving body with the laser light and detecting and converting its reflected light into an electric signal, and using it as a control signal. CONSTITUTION:Light from a laser light source 1 is passed through a lens 2, beam splitter 3, etc., and then reflected by a disk 8 to illuminate a photodetection surface 7 after changing in route by 90 deg. through the splitter 3. The photo- detection surface 7 is divided into four surfaces (a), (b), (c), and (d); when a point 9 coincide with a reflecting surface 8', the shape of the incident light is circular, but if it deviates to over or under the reflecting surface 8', the shape is elliptic having a long axis in a direction ac or bd. The driving system consisting of a differential amplifier 10, compensating circuit 11, etc., drives a driving motor 15 equipped with an objective lens 5 to make a convergent point 9 concident with the disk surface 8'. Meanwhile, the output of a power amplifier 12 is utilized as a signal for showing the surface shape.

Description

Detailed Description of the Invention (1) Technical Field of the Invention The present invention relates to a method KI for non-contactly detecting the shape of an object surface.
A method for detecting the surface shape of a moving object, such as a rotating disk, is determined.
)Technical background In devices such as optical disks and magnetic disks, in which a κ1 sickle medium is attached to the surface of a disc-shaped substrate and recording and playback is performed without rotating the substrate, the irregularities of the circular plane in the rotating state κ are The shape influences the recording characteristics.Therefore, knowing the flat surface roughness of the disk used in this type of device (1m) is a huge cost in building a disk manufacturing device. 0.

Like this! # When targeting a moving object, a non-contact detection method is required, and conventionally, a static cylinder wrinkle type detection method has been mainly used. m distribution capacitance 1al! In this method, in order to avoid Solution 1 and 1, the detection sensitivity must be increased, and in order to maintain the thin axis property of Oki 1, #ill and area cannot be made too small. Therefore, it is only possible to detect the average value of a relatively wide range of the subject (several mm square root skin), and a completely different method is required to detect irregularities in a smaller range. (dl Purpose of the Invention The purpose of the present invention is to provide a non-contact surface profile measurement method with finer resolution. When the light is irradiated and the reflected light is received, the stI laser beam is focused on the object R- using the electric power No. 411 obtained in this way, and the output number for the malting is used to determine the shape of the surface of the object. 8 is a disc-shaped The uneven shape of the surface 118' of the object (hereinafter simply referred to as a disk) is measured.

The laser light from the semiconductor laser #1 becomes parallel light through the lens 2, and the beam splitter 3,
The field passes through the light plate 4 and the objective lens 5 and is emitted onto the disk 8. *The parallel light edge is converged on point 9 by lens 5, and becomes point 9.
is on the disc surface 8', the circumstances of which will be explained later.0 After the reflected light from the disc surface 8' passes through the objective lens 5 and the polarizing plate 4 again, it is routed by the beam 1 ritter 3. 9
Turned to 0 degrees, received light through cylindrical lens 6 Nt17
The 0 received light Nli+7 entering the VC is 6ca, b, c as shown in Figure 2.
.

If the point 9 coincides with the reflection [II] 8', then the shape of the incident light is circular, as shown in Figure 2 (a) ic, but A9 is 4IitR
When sliding upward or downward on the surface, the optical movement K causes the shape of the light incident on the light receiving surface 7 to change with the long axis in the 6cm-c direction or the b-d direction. It becomes an oval shape〇Here, the light receiving head of each surface a, b, c, d is converted into an electric signal and the output is V as V be V C*
If V d is (Va+Vc)-(Vb+Va)
! A driving system consisting of a differential amplifier lO1 compensation circuit 11 and a power amplifier 12 generates a signal that
However, the voice coil motor 15 was increased to 14 mL, and the convergence point 9 was placed on the disk surface 8'! @Compensation circuit 11Fi
Since the voice coil motor 15 has a response characteristic that decreases with respect to high frequencies, this is to compensate for the stiffness. Even if the disk rotates and the surface position moves up and down due to the unevenness of its surface, the above-mentioned Since the servo system operates and the convergence point of the laser beam follows the fluctuation, the power amplifier 1
For example, the output voltage of the power amplifier 12 can be used as a signal representing the surface shape of the disk surface 8'.
3 to the oscilloscope 14, the shape corresponding to the disk surface 8' can be directly observed. The filter circuit 13 is provided by the damage compensation circuit 11 and is for recompensating the travel characteristics. The compensation circuit 11 has a strong high frequency range.
Due to its characteristics, it is usually a low-pass filter.In addition to being used directly as shown above, it can also be used to determine the quality of finished thighs by setting an excessive slice level. Yes ◎ The above explanation is for a rotating disk, but the basic KF
It is clear that the present invention is for measuring the surface shape Kj of an object moving in a direction substantially perpendicular to the optical axis.

It is also evident that the present invention has a resolution comparable to the dimensions of the laser beam convergence point. 4Iri can also be used to measure its thickness or change in thickness ◎ In this case, as shown in Figure 3, the convergence point of the laser beam is first set on one table ii] 8
After obtaining information about the position tK of the surface 8', the laser beam is focused on the other surface 81, and the table ik8 is
111, which obtains the 'vI rights regarding #, and calculates the thickness of the distance between the two surfaces by taking the difference between the two.

Although this method cannot be strictly applied to moving objects, if the object is a relatively slow moving object, it is possible to limit the measurement error to a combination of the measurement errors for a stationary object.◇ The thickness of a plate-like object can be measured by using two systems, an optical system and an electrical system, as shown in Figure 4. Te1~
7 optical systems and 10 to 120 electrical systems are prepared, and optical systems 1' to 7 have the same function for the other surface 811LC.
', prepare electrical systems 10' to 12'.

When the two surfaces 8'a8' are controlled so that the convergence point of the laser beam is located on each surface, positional information regarding both sides of the disk at the same position at the same time is provided. In particular, by using this, changes in plate thickness can be quickly determined with high resolution.
Since the two @ signals are in the same phase, it is only necessary to combine them using one of them and input it to the oscilloscope.

If you want to compare *6111 changes on two surfaces side by side, you can achieve your goal by using the two-phenomenon oscilloscope 1.

In the above explanation, an oscilloscope is used as a direct viewing means, but the same effect can be obtained even if this is replaced with a tlFiX-y recorder.

(gl According to the effect of the invention #4, it is possible to quickly and accurately measure the shape of a moving object's surface.

[Brief explanation of the drawing]

Claims (1)

[Claims] (13.1II.
The optical system is controlled so that the Wk2 laser beam is focused on one surface of the object, and the #W11I official blade wound g is m1.
1 to 2 Surface shape of a moving object characterized by being used as a signal representing the shape of the subject's surface life 1M11 feet h @. (2) Feature 1 characterized by alternately performing the operation of converging the primary laser beam on one surface of the subject and the self-made operation of converging it on the other surface that exists in parallel in Table (2).
Scope of 1FF visit - Surface shape measurement method described in item 1 0 (3) # +! Compare the two power outputs obtained by ff distribution optical and electrical flat membranes, and compare the two outputs obtained by the II century! Surface shape measuring method 0 according to claim 1, characterized in that the relative position in the lI direction is detected.