JPS5948324B2 - Inclination detection roughness measurement method using light reflection - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tilt angle detection roughness measurement method 15 using light reflection.

A parallel, narrow light beam is applied to a minute portion of the surface to be measured, the center of specular reflection or diffused reflection on that surface is detected, the tilt angle of the minute portion on the surface to be measured is detected, and this is integrated in the direction in which the light beam is swept. Then, the roughness waveform of the surface to be measured can be obtained.

What needs to be considered in particular when measuring roughness using this type of light reflection is whether the surface to be measured is a specular reflection surface such as a mirror surface or a diffuse reflection surface such as a rough surface. This means that there are 25 differences in the form of reflected light,
It is desired that roughness can be measured accurately no matter which reflective surface is applied.

Furthermore, since the reflectance of the surface to be measured is not always constant, it is also necessary to be able to perform measurements 30 while making corrections corresponding to changes in the reflectance of the surface to be measured. The measurement method of the present invention measures the roughness waveform in consideration of such problems, and basically measures the roughness waveform without contact using two optical sensors and a simple circuit system. The present invention is characterized in that it is configured such that it can be used, and that it is effective for application when the surface to be measured 35 is a specular reflection surface.

Examples of the present invention will be described in detail below.

First, as shown in FIG. 1, when a parallel narrow light beam such as a laser is projected from the light source 2 onto a minute portion of the roughness waveform of the surface to be measured 1, the intensity distribution of the reflected light is When is a specular reflecting surface such as a mirror, as shown in the figure, there is a distribution in which there is specular reflection in the direction with an angle of deviation θ that corresponds to the inclination of the minute part of the measured surface, and there is some diffuse reflection on the left and right sides. becomes. Therefore, bilaterally symmetrical optical sensors 3a and 3b having a light-receiving surface extending over a wide solid angle directly above the surface to be measured 1
If the two optical sensors directly receive the reflected light from the surface to be measured, and the differential amplifier 4 calculates the difference in their outputs, a differential output as shown by curve A in Figure 2 can be obtained. It will be done.

Figure 2 shows the relationship between the difference output and the declination angle θ.When the declination angle θ becomes large enough that the center of the reflected light deviates from the optical sensor, and when the declination angle θ is approximately O, the difference Output is O
However, the difference output between them is almost constant regardless of the angle of deviation θ.

Therefore, in the present invention, in order to be able to measure the inclination angle of a minute portion on the surface to be measured by detecting the difference output, the reflected light from the surface to be measured is weighted according to the declination angle θ of the center. Then, the light is received by the optical sensors 3a and 3b.

FIG. 1 shows an optical wedge 6 in front of the left and right optical sensors 3a and 3b, which absorbs more reflected light near the center and less absorption near the periphery, as a means for performing the above weighting.
This shows the case where .

When the reflected light is received with such weighting and the difference between the outputs is taken by the differential amplifier 4, the difference output is the second
As shown by curve B in the figure, it is approximately proportional to the declination angle θ within a certain range, and therefore, the inclination angle of the minute portion of the surface to be measured that is hit by the light beam can be determined from the difference output. . Furthermore, the surface to be measured 1 is moved in the direction of arrow
The roughness curve f(x) can be obtained by integrating in the scanning direction of the light beam on the surface 1 to be measured. As a means for performing the above weighting, a method as shown in FIG. 3 can also be used.

That is, in the above embodiment, a quadrangular optical sensor is generally used, but the optical sensors 3a and 3b are formed into a triangular shape divided at the center or a spherical triangular shape,
The above-mentioned weighting can also be performed by arranging the apex portions so as to butt each other. In this case, the optical sensor itself does not have to be formed into the above-described shape, but a triangular light-receiving surface may be left on the flat or hemispherical dome-shaped optical sensor and the rest may be covered. If the optical sensors 3a and 3b having such a shape are used, the output current of the optical sensor is approximately proportional to the area hit by the light, so that the reflected light of the light projected from the light source 2 through the slit 7 onto the surface to be measured 1 is reduced. Declination angle θ
When θ is small, the output is small because the reflected light is close to the center of the optical sensor, and when the angle of deviation θ is large, the output is large because the reflected light hits the periphery of the optical sensor, which causes weighting. It can be carried out.

When such an optical sensor is used, correction for changes in reflectance can be achieved by dividing the left and right optical sensors 3a and 3b into two at the center, and connecting optical sensors 8a and 8 with a constant width between them.
b is provided, and the inclination of the surface to be measured 1 is detected by taking the difference between the outputs of the optical sensors 3a and 3b using the differential amplifier 4, and the voltage is determined by the sum of the outputs of the optical sensors 8a and 8b for detecting reflectance. It is only necessary to control the attenuation rate of the control attenuator 9, and thereby it is possible to obtain a roughness curve f(x) in which the influence of reflectance changes is removed. In addition, in each of the above methods, when projecting the light beam from the light source 2 onto the surface to be measured 1, the light beam is projected onto the surface to be measured 1.
It is not necessary to make the light incident directly on the surface of the object, but it is also possible to make it incident obliquely. In this case, it is sufficient to install a pair of photosensors in the direction of regular reflection when the surface to be measured is flat. It is possible to eliminate the need to form a path for incident light between the two.

Furthermore, with this method, it is of course possible to measure the roughness of the surface to be measured 1 even if it is a diffusely reflecting surface. As is clear from the detailed explanation above, according to the method of the present invention,
The reflected light from the minute portion of the roughness waveform of the surface to be measured is weighted according to its polarization angle θ and received by the optical sensor.
By processing the output of the optical sensor with a simple circuit system, it is possible to measure the roughness waveform of the surface to be measured without contact, and it is especially effective for measuring the roughness waveform when the surface to be measured is a specular reflective surface. be. In addition, an optical wedge is placed in front of the optical sensor as a means of weighting the reflected light from the measurement surface according to the declination angle of its center. can be attached.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram regarding the measurement method of the present invention, and FIG. 2 is a diagram showing the relationship between the output from the differential amplifier and the polarization angle of reflected light.
FIG. 3 is an explanatory diagram regarding another method of the present invention. 1... Surface to be measured, 2... Light source, 3a,
3b... Optical sensor, 4... Differential amplifier, 5... Integrating circuit, 6... Optical wedge, 8a. 8b... Optical sensor for detecting reflectance,
9... Voltage controlled attenuator.

Claims (1)

[Claims] 1. A light beam that is parallel and thin is projected from a light source onto a minute portion in the roughness waveform of a surface to be measured, and when the surface to be measured is a flat surface, a pair of parallel light beams are projected symmetrically on both sides of the specular reflection direction. An optical sensor covering a wide solid angle is arranged, and the reflected light from the surface to be measured is weighted according to the declination angle of the center and received by the sensor, and a differential amplifier is used to calculate the difference between the outputs of both optical sensors. In this method, a roughness waveform is obtained by detecting the inclination angle of a minute portion on the surface to be measured and integrating this in the scanning direction of the light beam on the surface to be measured. Inclination detection roughness measurement using optical reflection that weights reflected light according to the declination angle at the center by arranging an optical wedge that absorbs more reflected light in the vicinity and less absorption near the periphery. Method. 2. An optical sensor that projects a parallel, narrow light beam from a light source onto a minute portion of the roughness waveform of the surface to be measured, and covers a pair of wide solid angles symmetrically on both sides of the specular reflection direction when the surface to be measured is flat. The reflected light from the surface to be measured is weighted according to the declination angle of the center and received by the above sensor, and the difference between the outputs of both optical sensors is taken by a differential amplifier. In the method of obtaining a roughness waveform by detecting the inclination angle of a minute portion on a surface and integrating this in the scanning direction of the light beam on the surface to be measured, a reflectance detection light of a constant width is placed in the center of the left and right optical sensors. By arranging the sensor and operating the voltage-controlled attenuator connected to the differential amplifier by the sum of the outputs of the optical sensors for detecting reflectance, the attenuation rate of the output of the differential amplifier is controlled, and the attenuation rate of the output of the differential amplifier is controlled. A tilt angle detection roughness measurement method using light reflection, characterized by correcting changes in reflectance of a surface.