JPH0642944A - Surface-roughness measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a surface-roughness measuring apparatus wherein the roughness of a surface and the displacement of the surface can be measured simultaneously by using one laser light source. CONSTITUTION:A laser beam is generated by a semiconductor laser 1, the laser beam is condensed by a condensing lens 4 and projected perpendicularly onto the surface of an object 7 under test, reflected light 8 with reference to a projection from the condensing lens 4 is condensed by a condensing lens 10, and an image of the reflected light is formed on a position measuring element 12 for surface displacement detection. In addition, a positive reflection component from the surface of the object 7 under test is taken out by a mirror 3 which has been arranged and installed between the semiconductor laser 1 and the condensing lens 4, and the specular reflection component is photodetected by a phototransistor 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the surface roughness of an object, and more particularly to a technique effectively used for simultaneously measuring the surface roughness and the surface displacement of an object.

[0002]

2. Description of the Related Art When measuring the surface condition of an object, there are many measurement symmetries, and typical ones are surface displacement (unevenness, etc.) and surface roughness. Each of them has a measuring device in combination with a laser light source, an optical system, and a light receiving element. For example, when measuring surface displacement, a surface displacement meter that applies the principle of triangulation is used.
For measuring the surface roughness, there is a surface roughness measuring device using a photo-contact method.

[0003]

According to the study by the present inventor, the conventional technique for measuring the surface state by the measuring devices each having only a single function is the measuring device according to the number of kinds of measuring items. However, there is a problem in that the cost is increased and the usability is poor.

Conventionally, as a method of measuring the surface roughness in a non-contact manner, there is a method of measuring an interference fringe generated by the interference between the projected light and the reflected light. However, a method of simultaneously measuring a surface displacement of several 100 μm and a surface roughness of 1 μm or less with one device has not been considered.

Therefore, an object of the present invention is to provide a technique capable of simultaneously measuring surface roughness and surface displacement using one laser light source.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0007]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

That is, a laser light source for generating a laser beam, a first optical system for collecting the laser beam from the light source and projecting the laser beam perpendicularly to the surface of the object to be measured, and the first optical system A second optical system for collecting reflected light with respect to the projection of
A first detection element for detecting a surface displacement, which is arranged at a focus position of the second optical system, and the first optical system which is arranged between the laser light source and the first optical system. An optical member for taking out the specular reflection component with respect to the light projected from and the second detection element for receiving the specular reflection component from the optical member are provided.

[0009]

According to the above-mentioned means, the reflected light reflected at a certain angle with respect to the laser beam projected perpendicularly to the object to be measured is imaged on the first detection element by the second optical system,
The surface displacement can be measured from the change of the image point, and the specular reflection component traveling in the opposite direction with respect to the projected laser beam is condensed by the first optical system, and is reflected on the second detection element by the optical member. Then, the surface roughness can be measured based on the ratio between the output of the detection element and the output of the first detection element. Therefore, the surface displacement and the surface roughness can be measured at the same time.

[0010]

1 is a block diagram showing an embodiment of a surface measuring apparatus according to the present invention.

In the surface measuring apparatus of this embodiment, a mirror provided with a pinhole 2 (for passing the light from the collimator lens 2 with a narrow diameter) on the emission optical path of the semiconductor laser 1 as a laser light source. 3 (optical member) and a condenser lens 4 (first optical system) are sequentially arranged.
A diaphragm 5 is provided on the light exit side of the condenser lens 4, and a projected laser beam 6 that has been focused is projected onto an object to be measured 7.

Reflected lights 8 and 9 are generated on both sides of the projected laser beam 6 at the same angle (θ). A condenser lens 10 (second optical system) is arranged to collect the reflected light 8, and a condenser lens 11 is arranged to collect the reflected light 9.
(Third optical system) is provided. Further, a position detection element (PSD: Position) is provided at the focal position of the condenser lens 10.
Sensitive Detector, a semiconductor optical sensor that outputs an analog signal proportional to the position of the incident spot light) 12 (first
The detection element) is disposed, and similarly, the position detection element 13 (third detection element) is disposed at the focal position of the condenser lens 11. Further, the specularly reflected light component condensed by the condenser lens 11 is guided to the emission optical path of the mirror 3, and the condenser lens 4
The phototransistor 14 (second detection element) is disposed at the focal position of.

Next, the operation of the embodiment having the above configuration will be described.

The laser beam emitted from the semiconductor laser 1 is focused by the pinhole 2, then reaches the condenser lens 4 via the mirror 3, is condensed by the condenser lens 4, and is focused by the diaphragm 5. The light is projected vertically onto the surface of the measurement object 7. The angle θ with respect to this light projection (here, θ = 30 °)
The reflected lights 8 and 9 are generated. At the same time, the reflected light intensity distribution 15 is generated in a leaf shape in the vertical direction, and specularly reflected light is generated toward the projection optical axis. This specular reflection component (I ₀ ) is condensed by the condenser lens 4, reflected by the mirror 3 in the direction at right angles, and then reaches the phototransistor 14.

On the other hand, the reflected light 8 is condensed by the condenser lens 10 and forms an image on the position detecting element 12. At the same time, the reflected light 9 is condensed by the condenser lens 11 and forms an image on the position detection element 13. In the position detecting elements 12 and 13, if there is a change in the vertical direction of the reflection point on the DUT 7,
In response to this, the image point on the position detecting element moves, and the surface displacement can be measured from this moving amount according to the principle of triangulation.

The surface displacement can also be measured by the position detecting element 13. That is, the reflected light 9 is condensed by the condenser lens 11 and imaged on the position detection element 13. The surface displacement is measured from the movement of this image point.
In this way, when the displacement of the reflected light is detected by the two systems, there is a large unevenness (or steep unevenness) on the DUT 7 and the reflected light does not reach the condenser lens (that is, a blind spot occurs. Even if) exists, no measurement failure will occur.

Furthermore, the reflection intensity ratio (I ₀ / I ₃₀ ) between the specular reflection component I ₀ incident on the phototransistor 14 and the irregular reflection component I ₃₀ incident on the position detecting element 12 (or the position detecting element 13) is determined. Based on this, the surface roughness Ra can be obtained. The relationship between the reflection intensity ratio and the surface roughness Ra is as shown in FIG. 2 (here, the case of θ = 30 ° is shown).
If the reflection intensity ratio is obtained, the surface roughness Ra can be uniquely obtained.

As described above, according to this embodiment, the surface displacement (for example, the measuring range of about 2 mm) and the surface roughness (for example, the measuring range Ra> 0) are obtained by one laser light source and one reflection point. .1 μm) can be measured at the same time.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, in the above-mentioned embodiment, the semiconductor laser is used as the laser light source, but a gas laser (for example, He-Ne) can be used instead.

In the above embodiment, the mirror 3 with a pinhole is used, but a right angle prism may be provided with a pinhole.

Further, the position detecting element (PSD) may be replaced with a phototransistor having a diaphragm at the light entrance portion. In this case, the surface displacement cannot be measured, but the surface roughness can be measured.

[0023]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.
It is as follows.

That is, a laser light source for generating a laser beam, a first optical system for converging the laser beam from the light source and projecting the laser beam perpendicularly to the surface of the object to be measured, and the first optical system A second optical system for collecting reflected light with respect to the projection of
A first detection element for detecting a surface displacement, which is arranged at a focus position of the second optical system, and the first optical system which is arranged between the laser light source and the first optical system. Since the optical member for extracting the specular reflection component with respect to the light projected from the light source and the second detection element for receiving the specular reflection component from the optical member are provided, the surface roughness and the surface displacement can be obtained by using one laser light source. Can be simultaneously measured, and the cost and size of the measuring device can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a surface measuring apparatus according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between surface roughness and a reflection intensity ratio.

[Explanation of symbols]

 1 Semiconductor Laser 2 Pinhole 3 Mirror 4 Condenser Lens 5 Aperture 6 Projected Laser Beam 7 DUT 8, 9 Reflected Light 10, 11 Condenser Lens 12, 13 Position Detection Element 14 Phototransistor 15 Reflected Light Intensity Distribution

Claims (5)

[Claims] 1. A laser light source for generating laser light,
A first optical system that collects laser light from the light source and projects the laser light perpendicularly to the surface of the object to be measured, and a second optical system that collects reflected light with respect to the light projected from the first optical system. A system, a first detection element for detecting a surface displacement provided at a focal position of the second optical system, and the first detection element provided between the laser light source and the first optical system. 2. An apparatus for measuring surface roughness, comprising: an optical member for extracting a specular reflection component with respect to the light projected from the optical system, and a second detection element for receiving the specular reflection component from the optical member. 2. A third optical system having an optical path at the same angle as the optical path of the second optical system and condensing reflected light from the object to be measured, and a focus position of the third optical system. The surface roughness measuring device according to claim 1, further comprising a third detection element for detecting a surface displacement, which is disposed in the. 3. The surface roughness measuring device according to claim 1, wherein the optical member is a mirror having a pinhole through which laser light from the laser light source passes. 4. The surface roughness measuring device according to claim 1, wherein the first and third detecting elements are position detecting elements (PSD). 5. The surface roughness measuring device according to claim 1, wherein the second detection element is a phototransistor.