KR19980052449A - Specimen of specular laser triangulation sensor or compensation method of angle error of sensor - Google Patents

Abstract

The present invention relates to the provision of a method for compensating for a measurement error according to an inclination angle when an object to be measured or a sensor head is inclined in use of a specular laser triangulation sensor.

The method of the present invention takes into account the geometric angle of the laser triangular sensor with the inclination angle θ taking into account that the displacement is added with an additional value X due to the inclination angle θ rather than the true displacement AB when the object to be measured or the sensor head is tilted. The difference between the measured displacement and the true displacement is obtained from the obtained inclination angle θ, and then the true displacement is obtained by subtracting the difference value from the measured displacement.

Description

Specimen of specular laser triangulation sensor or compensation method of angle error of sensor

The present invention relates to a method for compensating for errors caused by the tilt angle of a specimen or sensor in the use of a specular laser trigonometry sensor.

Triangular sensors using a laser (hereinafter abbreviated as sensor) are characterized by the principle that the working distance (distance between the specimen and the sensor) can be larger than other types of precision sensors. It is used a lot in). Unlike the diffuse reflection type, the specular reflection type is used for ultra-precision measurement of 0.01 μm class, and as shown in FIG. 1, the laser is irradiated to the measurement target with specular reflection, and the displacement is calculated from the image formation position of the reflected light. In order to reduce the size, a semiconductor laser is used.

In principle, light emitted from the semiconductor laser 2 driven by the drive circuit 1 passes through the lens 3 and is irradiated to the object under test. The light reflected at the point A of the object under test is imaged at A 'on the detector 5 through the condenser lens 4. If the measured object moves by A-B, the light from the light source reaches point B and the scattered light is imaged at point B 'which is shifted by A'-B' on the detector 5. The relationship between the displacement A-B and the deviation A'-B 'can be obtained geometrically. Since the lasers 2, the lenses 3, 4, the detectors 5, etc. are fixed positions, the outputs of the lasers 2, the lenses 3, 4, and the like are not changed, and the linear relationship can be obtained by correcting the relationship between A-B and A'-B 'in advance.

However, the specular triangulation sensor can accurately obtain the A-B displacement only when the object to be measured is placed vertically and horizontally as in the case of FIG. 1. If the object to be measured or the sensor head is slightly inclined, the displacement of A-B cannot be obtained as shown in FIG. 2, and the measured displacement is A-B + X.

The present invention has been studied in the background, to provide a method for compensating for errors in the use of a specular laser triangulation sensor even when the object or sensor has a tilt angle to enable accurate measurement Has its purpose.

1 is a structural diagram of a specular triangular sensor using a laser.

2 is a geometrical relationship diagram for obtaining the actual displacement when the specimen or sensor is tilted,

3 is a geometrical relationship diagram for obtaining a slope of a specimen or a sensor head,

* Description of the symbols for the main parts of the drawings *

1: driving circuit 2: laser

3,4 Lens 5: Detector

Hereinafter, with reference to the accompanying drawings, the method of the present invention for achieving the above object will be described in detail.

In the use of the specular laser triangulation sensor, if the measured object or the sensor head has the same inclination angle θ as shown in FIGS. 2 and 3, the true displacement AB is not measured and the actual measured displacement is the value of AB plus X. .

Therefore, to find the true displacement A-B, X must be subtracted from the displacement A-B + X, which is measured by X.

The method of the present invention comprises the steps of obtaining the X value according to the following procedure and subtracting the X value thus obtained from the measured displacement value A-B + X.

1) After fixing the object to be measured at the X1 position as shown in FIG. 3, the sensor value Z1 is measured, and the specular sensor is moved by X2-X1 to measure the sensor value Z2.

2) The slope θ can be obtained by the following equation.

θ = arctan [| Z2-Z1 | / (X2-X1)]

3) When the slope θ is obtained, Y can be obtained by the following equation in the geometric relationship of FIG. 2.

Y = X * tan (90-θ)

4) If Y is found, X can be found as

[X * tan (90-θ)] / (A-B) = tan (M / 2)

X = [tan (M / 2) * (A-B) / tan (90-θ)

5) Once X is found, subtract X from the measured displacement (A-B + X) to find the true displacement (A-B).

Therefore, the method of the present invention has the effect of making accurate measurement possible by compensating for the measurement error according to the measurement object or the sensor head when the specular laser triangulation sensor is tilted.

Claims (1)

In the use of the specular laser triangulation sensor, if the measured object or the sensor head has an inclination, obtaining the inclination angle θ, obtaining the difference between the measurement displacement and the true displacement with the obtained θ value, and calculating the difference value. Comprising a true displacement by subtracting from the measurement displacement of the specular laser triangular sensor, characterized in that the compensation method for the angle error of the sensor or sensor.