JPH0854234A - Three-dimensional coordinate position measuring method - Google Patents

Abstract

PURPOSE:To obtain a three-dimensional coordinate position measuring method in which the error due to thermal deformation caused by variation of the atmospheirc temperature or vibration at the time of movement can be corrected at the spot immediately before taking a measurement and the three-dimensional coordinate position can be measured conveniently. CONSTITUTION:Light is projected to first, second and third targets 21, 22 and 23 for which the true value of distance from a reference axis 20 connecting the centers of rotation 4a, 7a of first and second mirrors are known and the light projection angles and the image pickup angles are measured. Error amounts are then operated, respectively, based on the measurements and the coordinate position of a spot image on an object is corrected using the error amounts. This constitution realizes a highly accurate measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional coordinate position measuring method, and more particularly to a calibration method for calibrating a device error of a three-dimensional coordinate position measuring device using the principle of triangulation.

[0002]

2. Description of the Related Art Conventionally, the principle of triangulation has been widely used as one of the methods for contactlessly measuring the three-dimensional coordinate position of an object to be measured. FIG. 9 shows an example of a three-dimensional coordinate position measuring device using this triangulation principle. In this three-dimensional coordinate position measuring device 1, the laser light 3 from the light source 2
Is projected, a spot image 6 is formed on the DUT 5 through the first mirror 4. The spot image 6 is condensed on the condensing unit 8 via the second mirror 7 and is imaged on the optical sensor 8a provided therein. The rotation angle of the first mirror 4 and the rotation angle of the second mirror 7 are respectively the first drive unit 9
Also, it is detected by the first encoder 11 and the second encoder 12 built in the second drive unit 10 and input to the control unit 13. In addition, the light source 2 and the light condensing unit 8 have a rotating structure 14
the support structure 14 of the device 1 which is integrally mounted in a.
It is mounted on b so as to be rotatable in the direction of arrow A. The rotation angle of the rotating structure 14a is detected by the third encoder 16 incorporated in the third driving unit 15, and the control unit 13
Is input to The distance L between the rotation center 4a of the first mirror 4 and the rotation center 7a of the second mirror 7 is a triangulation reference distance L, which is a constant value. The measurement procedure by the conventional device 1 will be described below. By a predetermined operation of the operation unit 17, the third drive unit 15 is driven and the rotary structure unit 14a is rotated. Further, the first mirror 4 is rotated so that the laser beam 3 is projected onto the object to be measured 5, and the spot image 6 is irradiated onto the object to be measured 5. Then, the second mirror 7 is rotated and the spot image 6 is reflected by the second mirror 7 and imaged on the optical sensor 8a. The position of the formed image is detected by the optical sensor 8a, is converted into the image forming position information of the spot image via the image detecting unit 18, and is input to the control unit 13. The rotation of the second mirror 7 is further controlled based on this image formation position information. Then, when the spot image formed on the optical sensor 8a reaches, for example, the center point position of the optical sensor 8a, the rotation angle of the second mirror 7 and the rotation angle of the first mirror 4 are obtained. The coordinate position of the spot image 6 on the object to be measured 5 is calculated from the obtained both rotation angles and the distance L between the rotation center 4a of the first mirror 4 and the rotation center 7a of the second mirror 7. Hereinafter, the principle of calculating the three-dimensional coordinate position of the spot image 6 will be described with reference to FIG. This is the principle of triangulation itself.
The vertices of the triangle ABC in FIG. 9 correspond to the rotation center 4 a of the first mirror 4, the rotation center 7 a of the second mirror 7 and the spot image 6 in FIG. 9, respectively. Therefore, the reference distance L is the distance between the vertices A and B here. Each axis of the coordinate system is set as follows. The straight line AB is the Z axis, and the direction from the vertex A to the vertex B is the positive direction. Line segment AB
The axes passing through the midpoint O and orthogonal to the straight line AB are the X axis and the Y axis as shown in FIG. Rotating structure 1 in FIG.
The axis of rotation of 4a coincides here with the Z axis. Therefore, when the rotating structure 14a rotates, the triangle ABC
Rotates about the Z axis, that is, the side AB as the axis of rotation. Further, the line of intersection between the plane formed by the triangle ABC and the XY plane is the R axis. The angles formed by the side AC and the side AB with respect to the R axis are set to θ1 and θ2, respectively. However, regarding these angles, the directions of arrows P and Q in the drawing are positive. The angle formed by the R axis and the Y axis is φ. However, the direction of the arrow S is the forward direction. Θ1 is calculated from the rotation angle of the first mirror 4 measured by the first encoder 11, and θ2 is calculated from the rotation angle of the second mirror 7 measured by the second encoder 12. Further, the rotation amount of the third drive unit 15 measured by the third encoder 16 is φ.
At this time, the coordinate position R on the R axis of the spot image 6 is expressed as follows.

[Equation 1] Here, the method of calculating θ1 and θ2 from the respective rotation angles of the first mirror 4 and the second mirror 7 is as follows. First, on the side of the first mirror 4, the first encoder 11 is attached so that the rotation angle measurement value of the first mirror 4 becomes approximately 0 when θ1 = 0. Then, a deviation of the predicted value of the rotation angle of the first mirror 4 from 0 when θ1 = 0 is defined as a zero point offset of the first encoder 11. The zero point offset of the second encoder 12 is similarly defined. The zero point offset amounts of the first encoder 11 and the second encoder 12 are measured in advance. From the rotation angle of the first mirror 4 measured by the first encoder 11, the first encoder 1
Since the optical axis angle is twice the mirror angle, the value after subtracting the zero point offset of 1 is doubled to be θ1. Similarly, θ2 is obtained from the rotation angle of the second mirror 7 measured by the second encoder 12. The third encoder 16 for calculating the value of the angle φ also has a zero point offset, but this only causes the coordinate system of the device 1 to rotate by the zero point offset and does not contribute to the error in the coordinate position measurement value.

[0003]

In the conventional three-dimensional coordinate position measuring device 1 as described above, an error in the reference distance L occurs due to a component size error of a structure, an assembly error, or a thermal expansion / contraction effect due to a temperature change. Occurs. Further, the first encoder 11 and the second encoder 12 always have a zero point offset. Although the approximate values of these errors can be measured at the time of assembly and corrected as device parameters, the error amount is slight depending on the usage status of the device 1, but it also changes thereafter.
Since this change appears as a measurement error, highly accurate three-dimensional measurement could not be performed. The present invention has been made in view of the above circumstances. For example, it is possible to correct an error caused by thermal deformation due to a change in air temperature, vibration during movement, or the like on the spot immediately before measurement, and highly accurate tertiary It is an object of the present invention to provide a three-dimensional coordinate position measuring method that allows easy measurement of original coordinate position.

[0004]

In order to achieve the above object, a first aspect of the invention is to project spot light onto an object to be measured and to place the spot light on the object to be measured with an image pickup surface spaced a predetermined distance from the light projecting point. The spot image projected onto the object is imaged, and the measurement is performed by performing triangulation using the projection angle of the spot light, the imaging angle of the spot image, and the distance between the projection point and the imaging surface. In a three-dimensional coordinate position measuring method for calculating the position coordinates of a spot image on an object, at least 3 values for which the true value of the distance from the reference axis connecting the light projecting point and the imaging surface is known
The projection angle and the imaging angle are measured for each of the reference points, the respective error amounts are calculated based on the respective measured values, and the position coordinates of the spot image on the object to be measured are calculated using the respective error amounts. Is configured as a three-dimensional coordinate position measuring method. A second invention is that the spot light is projected onto the object to be measured, the spot image projected onto the object to be measured is picked up by an imaging surface which is separated from the light projection point by a predetermined distance, and the spot light is projected. Three-dimensional coordinate position for calculating the position coordinates of the spot image on the object to be measured by performing triangulation using the light angle, the imaging angle of the spot image, and the distance between the light projecting point and the imaging surface. In the measuring method, at least three reference points of which the true value of the distance from the reference axis connecting the light projecting point and the imaging surface is known are known in either one of the light projecting angle and the image capturing angle. The angle is set so that an unknown angle of the projection angle or the imaging angle is measured for each of the reference points, and each error amount is calculated based on each of the measured values. , The object to be measured using each of the above error amounts That are configured as a three-dimensional coordinate position measuring method characterized by correcting the position coordinates of the spot image. Furthermore, the three-dimensional coordinate position measuring method is characterized in that the number of reference points to be measured is two, assuming that the error amount of the projection angle is equal to the error amount of the imaging angle. .

[0005]

According to the first invention, the spot light is projected onto the object to be measured, and the spot image projected on the object to be measured is picked up by the image pickup surface separated by a predetermined distance from the light projection point. The position coordinates of the spot image on the object to be measured are calculated by performing triangulation using the projection angle of the spot light, the imaging angle of the spot image, and the distance between the projection point and the imaging surface. In doing so, the projection angle and the imaging angle are measured for at least three reference points whose true value of the distance from the reference axis connecting the projection point and the imaging surface is known.
The respective error amounts are calculated on the basis of the respective measured values. The position coordinates of the spot image on the object to be measured are corrected using the respective error amounts. This makes it possible to correct an error caused by, for example, thermal deformation due to a change in temperature, vibration during movement, or the like immediately before measurement, and highly accurate three-dimensional coordinate position measurement can be easily performed. According to the second aspect of the invention, when calculating the position coordinates of the spot image on the object to be measured, at least the known true value of the distance from the reference axis connecting the light projecting point and the imaging surface is known. The reference points are arranged such that only one of the projection angle and the imaging angle is a known angle. An unknown one of the projection angle and the imaging angle is measured for each of the reference points. The respective error amounts are calculated on the basis of the respective measured values. The coordinate position of the spot image on the object to be measured is corrected using each of the error amounts. In this case, either the projection angle or the imaging angle may be measured. Furthermore, assuming that the error amount of the projection angle and the error amount of the imaging angle are equal, and the number of reference points to be measured is two, the number of measurements can be further reduced.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the accompanying drawings for the understanding of the present invention. The following embodiments are examples of embodying the present invention and are not intended to limit the technical scope of the present invention. FIG. 1 is an explanatory view showing the basic principle of the three-dimensional coordinate position measuring method according to the first embodiment of the first invention, and FIG. 2 is the three-dimensional coordinate according to the first embodiment of the second invention. Explanatory diagram showing the basic principle of the position measuring method, FIG. 3 is an explanatory diagram showing the basic principle of the three-dimensional coordinate position measuring method according to the second embodiment of the first invention,
FIG. 4 is an explanatory view showing the basic principle of the three-dimensional coordinate position measuring method according to the second embodiment of the second invention, and FIG. 5 is the three-dimensional coordinate position measuring method according to the third embodiment of the first invention. 7 is an explanatory diagram showing the basic principle of the three-dimensional coordinate position measuring method according to the third embodiment of the second invention, FIG.
Is an explanatory view showing the basic principle of the three-dimensional coordinate position measuring method according to the fourth embodiment of the first invention, and FIG. 8 is the fourth embodiment of the second invention.
FIG. 9 is an explanatory diagram showing the basic principle of the three-dimensional coordinate position measuring method according to the embodiment of the present invention, and FIG. 9 is a schematic diagram (shared with the conventional example) showing a schematic configuration of an apparatus to which the above three-dimensional coordinate position measuring method can be applied. As shown in FIG. 9, the device 1a according to the three-dimensional coordinate position measuring method according to the first embodiment of the first invention projects laser light 3 (spot light) onto the object 5 to be measured, and The spot image 6 projected on the object to be measured 5 is imaged at the rotation center 7a of the second mirror 7 corresponding to the imaging surface which is separated from the rotation center 4a of the first mirror 4 corresponding to the point by the distance L. Conventionally, the position coordinates of the spot image 6 on the DUT 5 are calculated by triangulation using the projection angle of the laser light 3, the imaging angle of the spot image 6 and the distance L. Similar to the example. However, in this embodiment, as shown in FIG.
As shown in, the correction target 21 corresponding to at least three reference points whose true value of the distance from the reference axis 20 connecting the rotation center 4a of the first mirror 4 and the rotation center 7a of the second mirror 7 is known. , 22, and 23, the above-mentioned projection angle and imaging angle are measured, the respective error amounts are calculated based on the respective measured values, and the position of the spot image 6 on the DUT 5 is calculated using the respective error amounts. It differs from the conventional example in that the coordinates are corrected.

In the embodiment of the present invention, the first mirror 4 is used for convenience.
The positions of the rotation center 4a and the rotation center 7a of the second mirror 7 are set upside down as compared with the conventional example, but this is not an essential difference (the same applies to each of the following embodiments).
Hereinafter, the device 1a will be described in more detail. In this device 1a, the reference axis 20 is installed so as to be perpendicular to the floor surface 19. The correction target is placed on the floor surface 19 so that a total of three correction targets, that is, the first target 21, the second target 22, and the third target 23 are aligned with the device 1. The true value Rt of the distance in the depth direction of the first, second, third targets 21, 22, 23 is from below the device 1a to the first, second, third targets 21, 2.
It is measured by a measure 24 stretched in parallel with the floor surface 19 toward 2, 23. At the time of error correction, first, the measured value of the distance in the depth direction by the measure 24 of the first, second and third targets 21, 22, 23 is input to the control unit 13 via the operation unit 17. Then, triangulation is performed in the order of the first, second, and third targets to calculate the projection angle θ1, the imaging angle θ2, and the distance Rm in the depth direction of the device 1a to obtain the angle errors Δθ1 and Δθ2 and the distance error ΔL. In the subsequent measurement, the projection angle θ1, the imaging angle θ2, and the measured value Rm of the distance in the depth direction are calculated as Δθ1,
Correction is performed using Δθ2 and ΔL, and the three-dimensional coordinate position of the measurement point is calculated. Here, the measurement principle of the device 1a will be described. Also in the present device 1a, the coordinate position of the measurement point is measured based on each of the principles shown in the equations already described in the conventional technique. Therefore, ...
If the distance R of the formula can be calculated accurately from the formula, the position coordinates of the spot image 6 can be measured with high accuracy.

Here, the distance R is a true value Rt, and the angles θ1,
If θ2 and the distance L are true values themselves, the true value Rt is given by the following equation from the above equation.

[Equation 2] Here, assuming that the small fluctuation errors Δθ1 and Δθ2 are included in the angles θ1 and θ2 during the actual measurement, and the small fluctuation error ΔL is included in the reference distance L, the measured value Rm of the distance R at that time is as follows. .

(Equation 3) When the equations are substituted into the above equations and arranged, the following equations are obtained. However, when transforming the equation, Δθ1, Δθ
Considering that both 2 and ΔL are minute amounts, tan Δθ1 = Δθ1 tan Δθ2 = Δθ2, and Δθ1 ² , Δθ2 ² and ΔLΔθ1, ΔLΔθ2
The term is assumed to be negligible.

[Equation 4] From the above equation, three simultaneous equations are established by the measured values of the correction targets at three different true values Rt. Therefore, these equations are solved to calculate each small variation error Δθ1, Δθ2 and ΔL. Therefore, it is possible to correct each minute variation in the angles θ1 and θ2 and the distance L.

As described above, it is not necessary for all the coordinate values of the three-dimensional coordinates to be known as the reference point for error correction, and it is sufficient to measure the distance in the depth direction by a measure, for example. Therefore, it is possible to easily set the correction target and perform the correction calculation at the site where the three-dimensional coordinate position measuring apparatus 1a is used. That is, ΔL and Δθ1, Δθ2, which are minute variations of the offset distance error of the triangulation reference distance L and the projection angle θ1 and the imaging angle θ2, which are caused by thermal deformation due to temperature change, vibration during movement, and the like, are measured. It is possible to make corrections on the spot immediately before. Thereby, highly accurate three-dimensional coordinate position measurement can be easily performed. By the way, for the correction target, if either the projection angle θ1 or the imaging angle θ2 is known,
The number of measurements can be reduced. The second invention focuses on this point and will be described below. 1st of 2nd invention
1b by the three-dimensional coordinate position measuring method according to the embodiment
Is the rotation center 4 of the first mirror 4 as shown in FIG.
The correction targets 21, 22, and 23 corresponding to at least three reference points whose true value of the distance from the reference axis 20 connecting the a and the rotation center 7a of the second mirror 7 are known are set to the above projection angle or the above The targets 21 and 2 are arranged such that one of the imaging angles is a known angle.
2 and 23, the unknown angle of the projection angle or the imaging angle is measured, the error amount of each is calculated based on the measured values, and the measured object is measured using the error amounts. 5 is different from the conventional example in that the coordinate position of the spot image 6 on 5 is corrected.

The device 1b will be described in more detail below. In this device 1b, the reference axis 20 is installed so as to be perpendicular to the floor surface 19. Also in this case, the correction target is a total of three of the first target 21, the second target 22, and the third target 23.
Here, all are arranged so as to be lined up on a predetermined optical axis straight line on the light projecting side. The true value Rt of the distance in the depth direction of these first, second and third targets 21, 22, 23 is measured by a measure (not shown) or a predetermined value measured in advance by a jig 25 for holding each target. It can be determined by mounting each target at the position. At the time of error correction, first, the measured values of the distances in the depth direction of the first, second and third targets 21, 22, 23 are input to the control unit 13 via the operation unit 17. Further, the projection angle θ
The measured value of 1 is input to the control unit 13 via the operation unit 17. After that, the first, second and third targets 21, 2 are
Triangulation in the order of No. 2 and 23 to calculate the imaging angle θ2 and the distance Rm in the depth direction, and small fluctuation errors Δθ1 and Δθ2
And ΔL are obtained. Here, the light projection angle θ1 is a known angle, but conversely, the imaging angle θ2 may be a known angle and the light projection angle may be measured. Further, since the minute variation errors Δθ1 and Δθ2 are both minute amounts, it can be assumed that they are equal. 3 and 4 are examples in which the number of correction targets is reduced to two by assuming Δθ1 = Δθ2. In this way, the number of measurements can be reduced and simple three-dimensional coordinate position measurement can be performed. Hereinafter, modified examples according to the first and second inventions will be shown. FIG. 5 shows a modification of the first invention.
The difference from the first embodiment is as follows.

First, second, and third correction targets
The targets 21, 22 and 23 are arranged in a line with respect to the apparatus 1e so as to be aligned with each other in a straight line, and are arranged so as to float from the floor surface 19. With this, the same effects as those of the embodiment shown in FIG. 1 can be obtained. FIG. 6 shows a modified example according to the second invention. Here, the jig 25 for mounting the first, second, and third targets 21, 22, and 23 rotates in conjunction with the rotation of the light-projecting-side first mirror 4 so that the direction of the jig 25 always matches the projection angle. As a result, the projection angle when measuring the first, second, and third targets 21, 22 and 23 is always kept constant. The true value Rt from the device 1f of the first, second and third targets 21, 22 and 23 is measured by a measure (not shown) or each target is placed at a predetermined position of the jig 25 where the distance is measured in advance. It can be determined by mounting. When correcting the error,
First, the measured values of the distances in the depth direction of the first, second and third targets 21, 22, 23 are controlled by the control unit 1 via the operation unit 17.
Enter in 3. In addition, the measured value of the projection angle θ1 is displayed on the operation unit
It is input to the control unit 13 via 7. Thereafter, triangulation is performed in the order of the first, second and third targets 21, 22, 23 to calculate the imaging angle θ2 and the distance Rm in the depth direction.
Then, the minute fluctuations Δθ1, Δθ2 and ΔL are obtained. This also makes it possible to obtain the same effect as that of the embodiment shown in FIG. Further, FIG. 7 is a modification of the first invention, which is a modification of the embodiment of FIG. 5, and here, by setting the minute fluctuation error Δθ1 = Δθ2,
The number of correction targets is reduced to two. FIG. 8 shows a modified example of the second invention, in which the number of correction targets is reduced to two by setting the minute fluctuation Δθ1 = Δθ2 based on the embodiment of FIG.

[0012]

Since the three-dimensional coordinate position measuring method according to the present invention is configured as described above, an error caused by, for example, thermal deformation due to a change in temperature or vibration at the time of movement can be immediately measured immediately before measurement. It is possible to correct with, and it is possible to easily perform highly accurate three-dimensional coordinate position measurement.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a basic principle of a three-dimensional coordinate position measuring method according to a first embodiment of the first invention.

FIG. 2 is an explanatory diagram showing the basic principle of a three-dimensional coordinate position measuring method according to the first embodiment of the second invention.

FIG. 3 is an explanatory diagram showing a basic principle of a three-dimensional coordinate position measuring method according to a second embodiment of the first invention.

FIG. 4 is an explanatory diagram showing a basic principle of a three-dimensional coordinate position measuring method according to a second embodiment of the second invention.

FIG. 5 is an explanatory diagram showing a basic principle of a three-dimensional coordinate position measuring method according to a third embodiment of the first invention.

FIG. 6 is an explanatory diagram showing the basic principle of a three-dimensional coordinate position measuring method according to a third embodiment of the second invention.

FIG. 7 is an explanatory diagram showing a basic principle of a three-dimensional coordinate position measuring method according to a fourth embodiment of the first invention.

FIG. 8 is an explanatory diagram showing the basic principle of a three-dimensional coordinate position measuring method according to a fourth embodiment of the second invention.

FIG. 9 is a schematic diagram showing a schematic configuration of an apparatus to which the above three-dimensional coordinate position measuring method can be applied (shared with a conventional example).

FIG. 10 is an explanatory diagram showing the principle of triangulation.

[Explanation of symbols]

 1a to 1h ... Three-dimensional coordinate position measuring device 3 ... Laser light (spot light) 4a ... Rotation center of first mirror (corresponding to light projection point) 5 ... Object to be measured 6 ... Spot image 7a ... Rotation center of second mirror (Corresponding to imaging surface) 20 ... Reference axis 21 ... First target (corresponding to reference point) 22 ... Second target (corresponding to reference point) 23 ... Third target (corresponding to reference point)

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Shingo Sumie 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Co., Ltd., Kobe Research Institute (72) Inventor Taizo Yoshida, Nada-ku, Kobe City, Hyogo Prefecture Iwayakitamachi 4-5-22 Shinko Plant Construction Co., Ltd.

Claims (3)

[Claims] 1. A spot image projected onto the object to be measured by projecting spot light onto the object to be measured, and an image pick-up surface projected on the object to be measured at an imaging surface separated by a predetermined distance from the projection point. ，
In a three-dimensional coordinate position measuring method for calculating the position coordinates of the spot image on the object to be measured by performing triangulation using the image pickup angle of the spot image and the distance between the light projecting point and the image pickup surface. , The projection angle and the imaging angle are measured for at least three reference points whose true value of the distance from the reference axis connecting the projection point and the imaging surface is known, and based on the measured values, respectively. Is calculated, and the position coordinates of the spot image on the object to be measured are corrected by using the respective error amounts. 2. A spot image projected onto the object to be measured by projecting spot light onto the object to be measured, and a spot image projected onto the object to be measured is picked up by an image pickup surface separated by a predetermined distance from the light projection point. ，
In a three-dimensional coordinate position measuring method for calculating the position coordinates of the spot image on the object to be measured by performing triangulation using the image pickup angle of the spot image and the distance between the light projecting point and the image pickup surface. , At least three reference points whose true value of a distance from a reference axis connecting the light projecting point and the image pickup surface is known, and one of the light projecting angle and the image pickup angle is a known angle. Are arranged as described above, the unknown angle of the projection angle or the imaging angle is measured for each of the reference points, and each error amount is calculated based on each of the measured values. A three-dimensional coordinate position measuring method, characterized in that the position coordinate of the spot image on the object to be measured is corrected using an error amount. 3. The number of reference points to be measured is set to two on the assumption that the error amount of the projection angle is equal to the error amount of the imaging angle. 3D coordinate position measurement method.