JP2001021316A - Regular reflection type displacement gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a regular reflection type displacement gauge which can reduce error due to inclination of a surface to be measured, by installing a biaxial optical system. SOLUTION: This displacement gauge is equipped with an optical system including a light irradiating means casting a light on an object to be measured and a light receiving element receiving a light reflected from the object, and an operation processing means processing an output signal from the light receiving element and obtaining position information of the object. Two sets of the optical systems having the same irradiation point of lights on the object are installed. A first optical system 10 and a second optical system 20 are installed in the position relation that at least a light entering a light receiving element 12 of the first optical system 10 and a light entering a light receiving element 22 of the second optical system 20 are displaced in the opposite direction when the object is inclined. The operation processing means corrects measurement error caused by the inclination of the object to be measured on the basis of at least an output signal of the element 12 of the first system 10 and an output signal of the element 22 of the second system 20, and obtains position information of the object to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regular reflection type displacement meter, and more particularly to an optical regular reflection type displacement meter for measuring a displacement of a surface to be measured in a non-contact manner.

[0002]

2. Description of the Related Art FIG. 9 shows a conventional example. In the figure, the surface to be measured S is arranged parallel to the XY plane of the XYZ orthogonal coordinate system, and is displaced in the Z direction. The light irradiating means (laser transmitter) 53 irradiates the laser light L obliquely to the surface S to be measured, and outputs the reflected light to the light receiving element 5 disposed at the destination.
The light is received at 1. As the light receiving element 51, a PSD (Position-Sensitive Detectors) capable of detecting displacement of incident light is used. In such a configuration, the measured surface S is Z
When the displacement is made in the direction, the spot position of the light incident on the light receiving element 51 is displaced in accordance with the displacement amount in the Z direction. Therefore, by detecting the displacement amount of the spot position, the displacement amount in the Z direction of the measured surface S is detected. Can be detected.

[0003]

However, in the above conventional example, when the surface S to be measured is inclined, the laser light L
Is reflected, the measurement direction is inconvenient. That is, as shown in FIG. 10, when the surface to be measured S is tilted, the reflection direction of the laser light L is shifted as shown by the dotted line in FIG. 10, so that there is a disadvantage that a measurement error occurs.

[0006] As shown in FIG.
Is a transparent body such as glass, not only reflected light from the surface to be measured S, but also light transmitted through the transparent body and reflected on the back surface N is added as noise, which causes a measurement error. The reason for this is that in the displacement meter using the PSD, due to the characteristics of the element,
In order to detect the center of gravity of the received light as the position of the surface S to be measured, as shown in FIG.
In addition, the reflected light 55 from the back surface N of the transparent body is added to shift the center of gravity.

SUMMARY OF THE INVENTION An object of the present invention is to provide a regular reflection type displacement meter which can improve the disadvantages of the conventional example and, in particular, can reduce errors due to the inclination of the surface to be measured by providing a biaxial optical system. is there. Another object of the present invention is to use a PSD for one light receiving element and a CCD for the other light receiving element in the two-axis optical system, thereby reducing not only the error of the inclination but also the error in the measurement of the transparent body. It is an object of the present invention to provide a specular displacement type displacement meter which can be used. Still another object of the present invention is to obtain a higher accuracy than a displacement meter using only a CCD by performing a reference calculation on data from a PSD and a CCD.
An object of the present invention is to provide a regular reflection type displacement meter capable of high-speed measurement.

[0006]

The present invention employs the following structure to achieve the above object. 2. The specular displacement displacement meter according to claim 1, wherein the optical system includes a light irradiating unit that irradiates light to the object to be measured and a light receiving element that receives light reflected from the object to be measured, and an output signal from the light receiving element. And a processing unit for obtaining position information of the object to be measured, wherein the optical system comprises: a first optical system for irradiating the object with the same light irradiation point. A light incident on the light receiving element of the first optical system and a light incident on the light receiving element of the second optical system in directions opposite to each other when the device under measurement is tilted. A first optical system and a second optical system are installed in a displaced positional relationship, and the arithmetic processing means includes an output signal of a light receiving element of the first optical system and the second optical system.
And correcting the measurement error caused by the tilt of the object to be measured based on the output signal of the light receiving element of the optical system to obtain the position information of the object to be measured.

According to the present invention, when the object to be measured is tilted, the light incident on the light receiving element of the first optical system and the light incident on the light receiving element of the second optical system are displaced in directions opposite to each other, The error of the output signal from the light receiving element of each optical system based on the displacement is canceled by the arithmetic processing means, so that the error due to the inclination of the surface to be measured can be reduced.

According to a second aspect of the present invention, there is provided a specular reflection type displacement meter according to the first aspect, wherein the light receiving element of the first optical system is a PSD and the second optical system is a light receiving element. The light receiving element is a CCD, and the arithmetic processing means corrects the transparent object based on the output of the CCD before correcting the measurement error caused by the inclination of the object to be measured. , And the effect of noise reflected on the back surface is removed. According to the present invention, since the CCD is used as the light receiving element of the second optical system, not only the error in the inclination of the surface to be measured can be reduced, but also the error due to noise transmitted through the transparent body and reflected on the back surface of the transparent body. Can also be reduced. In addition, by performing a reference operation on data from the PSD and the CCD, it is possible to perform higher precision and higher speed measurement than a displacement meter using only the CCD.

According to a third aspect of the present invention, in the regular reflection type displacement meter according to the second aspect, the arithmetic processing means calculates the thickness of the transparent body based on an output of the CCD. A thickness calculator is provided, wherein the thickness of the transparent body is calculated based on the output of the PSD and the output of the CCD, after correcting a measurement error caused by the inclination of the object to be measured. According to the present invention, the light applied to the transparent body is divided into a component reflected on the front surface (measured surface S) of the transparent body and a component reflected on the back surface of the transparent body. Is received at. The thickness calculating means of the arithmetic processing means extracts, from the output of the second light receiving element (CCD), the incident position of the component reflected on the front surface of the transparent body and the incident position of the component reflected on the back surface of the transparent body, respectively. Then, since the thickness of the transparent body is calculated based on the extracted difference data of the incident position, the thickness of the transparent body can be measured with high accuracy.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. The regular reflection type displacement meter according to the first embodiment aims at reducing an error due to the inclination of the surface to be measured, and a light irradiation unit for irradiating the surface to be measured with light obliquely, and a light source from the surface to be measured. Two sets of optical systems including a light receiving element for receiving the reflected light are provided with the same light irradiation point on the surface to be measured.

FIG. 1A shows a configuration of a first optical system 10 including a first light irradiating means 11 and a first light receiving element 12. FIG. 1B shows a configuration of a second optical system 20 including a second light irradiation unit 21 and a second light receiving element 22. FIG. 2 is a diagram in which a light irradiation position P of each of the optical systems 10 and 20 is viewed from a normal direction of the surface S to be measured.

In the following description, it is assumed that the surface S to be measured is a plane arranged in parallel with the XY plane in the XYZ rectangular coordinate system. Each of the light irradiation means 11 and 21 is constituted by a laser transmitter. In addition, each light irradiation means 11 and 21
The laser irradiation position P on the measured surface S is fixed at a reference position (predetermined Z coordinate) of the measured surface S in the Z direction, where the angle between the light irradiation direction and the XY plane is fixed to each other. Are fixed to the Z coordinate such that Each of the light irradiation units 11 and 21 is not limited to an element that self-generates a laser, and may be an optical element that reflects a laser generated by another element in a predetermined direction.

Each of the light receiving elements 12 and 22 is constituted by a PSD capable of detecting a displacement of incident light. Further, each of the light receiving elements 12, 22 is fixed at the same Z coordinate,
In addition, the angle between the light receiving surface and the XY plane is fixed to be equal to each other.

As shown in FIG. 2, the optical systems 10 and 20 are set so that the XY components in the light irradiation direction are not parallel and are not orthogonal. For this reason, each optical system 1
The optical elements 0 and 20 can be arranged at positions where they do not collide with each other and do not block the optical path. Thereby, when the surface S to be measured is inclined, the light receiving element 1 of the first optical system 10
The first optical system 10 and the second optical system 20 are arranged in a positional relationship where the light incident on the second 2 and the light incident on the light receiving element 22 of the second optical system 20 are displaced in opposite directions. .

Here, as shown in FIGS. 3A and 3B, when the surface S to be measured is inclined from a solid line to a dotted line, the reflection of the laser light from each of the light irradiation means 11 and 21 is performed. The direction changes, and as a result, the laser incident position on each of the light receiving elements 12 and 22 changes even though the Z coordinate of the surface S to be measured is not displaced. As shown in FIGS. 3A and 3B, when the surface S to be measured is inclined upward and downward, the first optical system 10 shown in FIG. The position is shifted upward from a solid line as shown by a dotted line. On the other hand, in the second optical system 20 shown in FIG. 3B, the incident position on the light receiving element 22 shifts downward from the solid line as indicated by the dotted line.

FIG. 4 shows the relationship between the light receiving position of each of the light receiving elements 12 and 22 in the Z direction and the light receiving center of gravity. That is, the position where the position C should be the center of gravity is shifted to the position B in the plus direction in the first light receiving element 12 and shifted to the position A in the minus direction in the second light receiving element 22. The shift amount of the center of gravity becomes equal between AC and BC.

Therefore, as shown in FIG. 4, a center-of-gravity calculating means 12 for calculating the center of light reception from the output of the first light-receiving element 12.
a, a center of gravity calculating means 22a for calculating a light receiving center of gravity from the output of the second light receiving element 22, and a light receiving center of gravity and a center of gravity of the first light receiving element 12 calculated by the center of gravity calculating means 12a calculated by the center of gravity calculating means 12a. Correction means 30 for averaging the positions of the centers of gravity of the two light receiving elements 22; displacement calculation means 40 for calculating the Z-direction displacement of the surface S to be measured based on the output of the correction means 30; Measured surface S
And a display means 50 for displaying the displacement of the object S, the displacement of the surface S to be measured is relatively accurately calculated by reducing or eliminating the influence of the inclination of the surface S to be measured. It becomes possible. Note that the configuration of the arithmetic processing unit 101 is not limited to the configuration of this embodiment,
Other configurations may be used.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIG. The second embodiment aims at reducing the error at the time of measuring the transparent body. In the first embodiment, the PSD is provided to the first light receiving element 12 of the two-axis optical system and the second light receiving element is provided. A CCD is used for each element 22. Further, a supplementary processing unit 22b is added to the arithmetic processing unit 102 of the present embodiment. The second
The center of gravity calculating means 22a connected to the light receiving element 22 of C
Means for calculating the barycenter data of the pixel value from the output of the CD is configured. Other configurations are the same as those in the first embodiment.

The complementary processing means 22b includes the second light receiving element 2
The resolution of the finite pixel data of the CCD is improved by extracting the position data at which the amount of light is detected most from the output of the 2 (CCD) and performing complementation processing of the pixel value from the peripheral data. The correction unit 30 corrects the output data of the first light receiving element 12 (PSD) using the data complemented by the complement processing unit 22b as reference data.

More specifically, the data Xc (data obtained from the CCD) calculated by the center-of-gravity calculating means 22a and the data Xp (data obtained from the PSD) calculated by the center-of-gravity calculating means 12a are calculated. , And obtain inclination correction data. Using a simple formula, the correction amount δXc is ｛(Xc + X
p) / 2｝ −Xc. This value is the correction amount of the value Xccd obtained by the complement processing means 22b. Thus, the data obtained from the CCD is calculated as follows: X = Xccd + δXc · k (θ) Here, k (θ) is a correction coefficient including optical characteristics and the like.

Based on this data, a correction operation is performed on the data Xp obtained from the PSD. Assuming that the calculated data is Zi, it is expressed as Zi = Xpi + (Xp−X), and the position data at which the amount of light is most detected is obtained based on the PSD data. Where (Xp-X) is the CCD
Indicate the data at the time when the data of one line pixel has been collected (in this processing example, X is the position data at which the amount of light is detected most), and Zi and Xpi are the timings other than the arithmetic processing. Show data. In other words, in a time zone in which no measured value is obtained during the CCD data acquisition time (idle feed time, dummy signal time, signal transfer time, etc.),
Using (Xp−X) calculated using the immediately preceding data Xc and the position information Xp of the PSD at that time as correction reference data, X
A correction operation is performed on pi to calculate Zi with a small error.

As a processing method of the center-of-gravity calculating means 22a, for example, there is a method of obtaining x satisfying the following equation and complementing its neighborhood to improve the resolution.

[0023]

(Equation 1)

As described above, the second light receiving element 22 has a CCD
Is used, it is possible not only to reduce the error in the inclination of the surface S to be measured, but also to reduce the error due to noise transmitted through the transparent body and reflected on the back surface of the transparent body.

The operation time of the CCD is slower than the signal processing time of the PSD. Therefore, the correction means 3 is used during the calculation of the CCD data similar to that of the conventional general image processing type displacement meter or in place of the calculation of the conventional CCD data.
0 corrects the PSD data based on the reference data received from the complementing processing means 22b, so that the displacement measurement of the transparent body can be performed at high speed. This processing algorithm not only reduces errors due to noise when measuring a transparent object, but also enables faster and more accurate processing than conventional image processing displacement meters that use a single CCD. It is also possible to perform a measurement in which the inclination error of is reduced.

(Third Embodiment) A third embodiment of the present invention will be described with reference to FIGS. In the third embodiment,
In the second embodiment, the thickness can be measured using the position detecting function of the CCD.

In general, as shown in FIG. 7, the light irradiated on the transparent body is reflected on the surface (measured surface S) of the transparent body 52 and on the back surface N of the transparent body 52. Each component is received by the CCD (light receiving element 22).

As shown in FIG. 8, a thickness calculating means 60 is newly added to the arithmetic processing means 103 of this embodiment. The thickness calculation means 60 outputs the second light receiving element 22 (CC
From the output of D), the incident position of the component reflected on the front surface S of the transparent body 52 and the incident position of the component reflected on the back surface N of the transparent body 52 are respectively extracted, and the difference data of the extracted incident positions is extracted. The thickness of the transparent body 52 is calculated based on this, and this thickness is displayed on the display means 50. Other configurations are the same as those of the second embodiment.

In this case, the same effect as in the above embodiment can be obtained, and the thickness of the transparent body 52 can be measured without contact. Further, the thickness of the transparent body can be measured while reducing the inclination error. Hereinafter, the processing procedure will be described.

For example, as shown in the second embodiment, the inclination correction data is obtained from the center-of-gravity calculation processing data of the CCD and the PSD. Thus, the data obtained by the CCD is calculated as follows: X = Xccd + δXc · k (θ) Here, k (θ) is a correction coefficient including optical characteristics and the like. By applying the above calculation formula to the above extracted data, the thickness of the transparent body can be measured while reducing the inclination error.

Also, since the same processing as in the second embodiment can be applied to the processing procedure (in this processing procedure, the PSD
Since the data processing time and the CCD data processing time hardly overlap), the thickness measurement and displacement measurement can be performed without changing any settings by using the surface data as displacement data. It is. Further, it is also possible to set the back surface data as displacement data by setting. This indicates that it is possible to detect which surface (front surface, back surface) has a large change when the thickness changes in the thickness measurement.

In addition, by using the correlation data between the barycenter data of the PSD and the position data of the CCD, the transmittance data of the transparent body can be output as relative data. This indicates that the thickness information of the measurement target and the transmittance change at the measurement position can be separated to some extent, which is effective for detecting a defect of the transparent body. In an embodiment using a CCD, a mode changeover switch may be provided in the arithmetic processing means so that high-speed measurement using only the conventional PSD can be performed in accordance with the operation of this switch.

[0033]

According to the regular reflection type displacement meter of the present invention, the measuring optical system including the light irradiating means for irradiating the object to be measured and the light receiving element for receiving the reflected light from the object to be measured can be measured. Equipped with two sets of light irradiating points on the object, signal processing is performed so that the error of the output signal generated in each light receiving element is canceled by the inclination of the surface to be measured, so errors due to the inclination of the surface to be measured are reduced. It is expected that not only the inclination error but also the error in the measurement of the transparent body can be reduced, and that the measurement can be performed with higher accuracy and higher speed than the displacement meter using only the CCD.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system according to a first embodiment of the present invention. FIG. 1A is a configuration diagram of a first optical system, and FIG.
(B) shows the configuration of the second optical system.

FIG. 2 is a configuration diagram showing an arrangement relationship between both optical systems shown in FIG.

3A and 3B are explanatory diagrams showing a relationship between a tilt of a surface to be measured and a change in an incident position of reflected light on a light receiving element. FIG. 3A is an explanatory diagram of a first optical system, and FIG. () Is an explanatory diagram relating to the second optical system.

FIG. 4 is an explanatory diagram showing a principle of correcting a measurement error caused by a tilt of a surface to be measured.

FIG. 5 is a block diagram of an arithmetic processing unit applied to the first embodiment.

FIG. 6 is a block diagram of an arithmetic processing unit applied to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of an optical system according to a third embodiment of the present invention.

FIG. 8 is a block diagram of an arithmetic processing unit applied to a third embodiment.

FIG. 9 is an explanatory diagram showing a measurement principle of a conventional general regular reflection type displacement meter.

FIG. 10 is an explanatory diagram showing a problem of a conventional example.

FIG. 11 is an explanatory diagram showing a problem of a conventional example.

FIG. 12 is an explanatory diagram showing a problem of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 1st optical system 11 1st light irradiation means 12 1st light receiving element 12a Center-of-gravity calculation means 20 2nd optical system 21 2nd light irradiation means 22 2nd light-receiving element 22a Center-of-gravity calculation means 22b Complement processing means Reference Signs List 30 correction means 40 displacement calculation means 50 display means 52 object to be measured 60 thickness calculation means 101 arithmetic processing means 102 arithmetic processing means 103 arithmetic processing means S surface to be measured N back surface of transparent body P irradiation point of light to the object to be measured

Continued on the front page (72) Inventor Akira Sato 1-2-1-1, Sakado, Takatsu-ku, Kawasaki, Kanagawa Prefecture (72) Inventor Hiromitsu Furushima 1-2-1-1, Sakado, Takatsu-ku, Kawasaki, Kanagawa Corporation Mitutoyo F-term (reference) 2F065 AA17 AA65 BB13 BB22 BB24 DD03 EE03 GG04 HH04 HH12 HH14 JJ02 JJ03 JJ16 JJ25 JJ26

Claims (3)

[Claims] An optical system including a light irradiating means for irradiating the object with light and a light receiving element for receiving reflected light from the object to be measured, and an output signal from the light receiving element being processed to process the object to be measured. Wherein the optical system includes a first optical system and a second optical system that make the irradiation point of light on the object to be measured the same. A first positional relationship in which the light incident on the light receiving element of the first optical system and the light incident on the light receiving element of the second optical system are displaced in opposite directions when the object to be measured is tilted. An optical system and a second optical system are provided, and the arithmetic processing unit is configured to perform the measurement based on an output signal of the light receiving element of the first optical system and an output signal of the light receiving element of the second optical system. It is characterized in that the measurement error caused by the inclination of the object is corrected and the position information of the object to be measured is obtained. Specular reflection type displacement meter for the. 2. The specular displacement type displacement meter according to claim 1, wherein the light receiving element of the first optical system is a PSD.
The light receiving element of the second optical system is a CCD, and the arithmetic processing means corrects a measurement error caused by a tilt of the object to be measured, which is a transparent body, before correcting the measurement error.
A specular displacement type displacement meter, wherein the influence of noise transmitted through the transparent body and reflected on the back surface is removed based on the output of the CCD. 3. The regular reflection type displacement meter according to claim 2, wherein the arithmetic processing means includes a thickness calculating means for calculating a thickness of the transparent body based on an output of the CCD, and the PS
A specular reflection displacement meter, wherein the thickness of the transparent body is calculated after correcting a measurement error caused by the inclination of the object to be measured based on the output of D and the output of the CCD.