JP3189557B2 - Three-dimensional shape measurement method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a three-dimensional shape, and more particularly to a method for measuring the three-dimensional shape of various objects. The present invention relates to a method of measuring the position of each point on the surface of the object, and measuring the three-dimensional shape of the measured object by integrating the position information of each point.

[0002]

2. Description of the Related Art A method for measuring a three-dimensional shape of an object to be measured by a non-contact type measuring means is used in various technical fields as a method for accurately and quickly measuring the three-dimensional shape of an object to be measured. Also, various measuring devices to which such a three-dimensional shape measuring method can be applied have been proposed.

For example, there is a measuring device in which a measuring instrument of non-contact type measuring means is movably installed along a plane parallel to the surface plate above a surface plate on which an object to be measured is placed. While moving the measuring instrument back and forth and right and left, the position of a point on the DUT located immediately below the measuring instrument is measured at each position. As a specific example of the non-contact type measuring means, for example, irradiate a spot light from directly below the measuring instrument, receive the reflected light reflected on the surface of the object to be measured again by the measuring instrument, from the light receiving position There is a method of measuring a distance from a measuring instrument to an object to be measured by the principle of triangulation. By subtracting the distance from the measuring instrument to the object to be measured from the distance from the measuring instrument to the surface of the surface plate, the height of the object to be measured at that point can be obtained. If the height of the measured object is obtained for many points on the measured object, the three-dimensional shape of the entire measured object can be measured.

[0004]

However, in the conventional method and apparatus for measuring a three-dimensional shape as described above,
There is a problem that it takes time to prepare for starting the measurement, and the measurement accuracy of the three-dimensional shape is not sufficient.

That is, in the conventional measuring apparatus as described above, if the surface of the surface plate on which the object to be measured is mounted and the moving surface on which the measuring instrument moves are not exactly parallel surfaces, the object to be measured is The height measurement at each point in is inaccurate,
The measurement accuracy of the three-dimensional shape deteriorates. In addition, if the direction of the spot light emitted from the measuring instrument is not exactly right below, an error occurs in the distance from the measuring instrument to the object to be measured.

For this reason, in the conventional measuring apparatus, when the measuring instrument and its moving mechanism are mounted on the surface plate, the moving surface of the surface plate and the measuring instrument is made to be an accurate parallel plane by using a level or the like. In addition, it was necessary to carry out careful work, which was a very laborious work. In addition, while using the measuring device, due to external force such as vibration or impact or environmental change,
In some cases, the measurement results may be inaccurate due to the displacement of the position or posture of the measuring device or the moving mechanism. Therefore, on a regular basis,
In some cases, it was necessary to check or correct the mounting positions and postures of the measuring instrument and the moving mechanism.

[0007] Further, there is no problem when the measurement surface of the measurement object faces the irradiation light from the measuring instrument, but the measurement surface of the measurement object is inclined with respect to the irradiation light from the measurement. In this case, the reflected light from the measurement surface cannot be captured by the measuring instrument, and the measurement cannot be performed. Therefore, the position of the measuring instrument can be changed so that the irradiation light from the measuring instrument faces the measuring surface of the measuring object, or the measuring instrument can be swung freely, so that the measuring surface of the measuring object can be measured. It was conceived to change the direction of light irradiation in accordance with the shape of.

However, if the measuring instrument is tilted to change the direction of light irradiation, the inclination of the measuring instrument with respect to the surface of the surface plate naturally changes. There is no continuity with the measurement result. Even if the distance from the measuring device to the measuring point is the same, the height of the measuring point varies depending on the inclination of the measuring device. For this reason, it has not been possible to measure one object by changing the inclination of the measuring instrument depending on the location.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to improve the measurement accuracy of a three-dimensional shape by accurately knowing the position and orientation of a measuring instrument, that is, a measuring means. Even if the measuring means is tilted or the posture is changed according to the shape of the object to be measured, the measurement can be performed without any problem, and the installation and adjustment of the measuring means is easy and the three-dimensional shape is easy to work. And to provide a device.

[0010]

A three-dimensional shape measuring apparatus according to the present invention, which solves the above-mentioned problems, is a non-contact type measuring means which is movable with respect to a fixed object to be measured. In the method of measuring the position of each point of the three-dimensional shape of the object to be measured, a reference spherical body and a reference plane are arranged on the stationary surface of the object to be measured, and the reference spherical body and At least three points on each surface of the reference plane are measured relative to the measurement means by the measurement means, and the position of each point on the reference sphere measured here is used as the center of the reference sphere relative to the measurement means. And the relative attitude of the reference plane relative to the measurement means is determined from the position of each point on the reference plane, and based on these results, the measurement means with respect to the stationary surface of the object is measured. Know your position and posture.

An object to be measured is usually measured on a stationary surface such as a surface plate whose surface is finished to an accurate flat surface. However, even if it is not placed on the surface plate, it is sufficient that it is supported at a fixed position by being pinched or suspended by some means. In this way, the surface serving as a reference when the object to be measured is arranged at a fixed position is referred to as a stationary surface.

As the non-contact measuring means, various known measuring means such as a measuring instrument for performing distance measurement by triangulation with a spot light such as a laser are used. The measurement principle and internal mechanism can be freely combined with known techniques. Non-contact type measurement means using various radiations, electromagnetic waves, magnetism, ultrasonic waves, etc. instead of light can also be adopted.

The moving mechanism of the non-contact type measuring means can adopt the same structure as the moving mechanism in the known three-dimensional shape measuring apparatus. The movement of the measuring means may be any combination of a linear motion in the front / rear, left / right or vertical directions, a turning motion in a horizontal or vertical plane, and the like, as necessary. As the moving mechanism, it is preferable that the movement mechanism can perform a movement of inclining the measuring direction of the measuring means. The measuring direction of the measuring means is the irradiation direction of the spot light, and is the direction in which the measuring point to be measured is to be arranged.

The reference spherical body may be a complete spherical body, or a partial spherical body such as a body in which a pillar protrudes from a part of the spherical body, a hemisphere, or a combination of a solid and a sphere such as a rectangular parallelepiped. . It is only necessary that the measuring means has a spherical surface capable of taking at least three or more measurement points at which position measurement can be performed. The diameter of the reference spherical body and the area of the spherical surface may be set in consideration of the measurement principle and accuracy of the measuring means, the processing accuracy of the spherical surface, and the like. For example, in the case of a measuring unit that performs triangulation using a spot light, the diameter of the spot light is 1
Those having a sphere diameter of about 0 to 100 times are preferred. The reference spherical body is preferably made of a material that can be formed into an accurate and smooth spherical surface without unevenness or distortion that affects the measurement. Specifically, ceramic is a preferred material. Hard metals, synthetic resins, and vitreous materials can also be used.

The reference spherical body is set in advance separately from the measuring means. Specifically, for a stationary surface such as a surface plate,
It may be attached at an appropriate position, and may be formed integrally with the surface plate, or may be fixed with screws or metal fittings. The reference spherical body may be located at a position away from the stationary surface, for example, by providing the reference spherical body at the tip of a support standing on the surface plate. Further, the reference spherical body may be detachably attached to a plurality of positions on a stationary surface such as a surface plate. If the mounting position of the reference spherical body can be changed, the reference spherical body can be mounted in a place that does not hinder the measurement according to the shape of the object to be measured. In the present invention, it is only necessary that the position of the reference spherical body serving as the reference of the position of the measuring means is fixed so as not to move during a continuous series of measuring operations.

In the same manner as the reference spherical body, if the reference plane has a plane capable of taking at least three or more measurement points at which the position can be measured by the measuring means, its planar shape and area can be freely set. it can. The reference plane body is formed of the same material as the reference spherical body. The reference plane body may be located on the same plane as the stationary plane or at a position apart from the stationary plane as long as it is arranged at a fixed position and posture with respect to the stationary plane of the device under test. The reference plane body may be arranged parallel to the stationary surface, or may be inclined, and the inclination angle can be set arbitrarily.
Like the reference spherical body, the reference plane body may be detachably attached to a plurality of positions on a stationary surface such as a surface plate. The reference plane body and the reference spherical body may be integrally formed so that both can be handled together.

A reference plane represented by the surface of the reference plane,
One coordinate system is determined based on the origin represented by the spherical center of the reference spherical body. This coordinate system is an absolute coordinate system that does not change depending on the movement position or the posture of the measuring means.

In the present invention, the position and orientation of the measuring means are known by measuring the reference spherical body and the reference plane by the measuring means.

That is, the measuring means measures the positions of at least three measurement points on the surfaces of the reference spherical body and the reference plane body. Here, what is measured is a relative position based on the position and orientation of the measuring means.

From the measured positions of at least three points on the reference spherical body, the relative position of the center of the spherical surface of the reference spherical body with respect to the measuring means is determined by performing appropriate arithmetic processing in accordance with the law of geometry. Can be Such arithmetic processing may be performed using an arithmetic processing device such as a microcomputer incorporated in the control device of the measuring means and an arithmetic processing program. Note that in order to find the center of the sphere of the reference sphere, it is theoretically sufficient to know the positions of at least three points and the radius of the reference sphere. The center of the sphere is found. In addition, by measuring the number of positions exceeding the theoretically necessary number, errors in the measured positions can be reduced. From the positions of the three points on the reference plane, the relative attitude of the reference plane to the measuring means is determined. The calculation process at this time is performed in the same manner as in the case of the reference spherical body.

Based on the relative position of the spherical center of the reference spherical body with respect to the measuring means and the relative attitude of the reference plane with respect to the measuring means, in the absolute coordinate system determined by the reference spherical body and the reference plane, The position and orientation of the measuring means are determined.

Based on the obtained information on the position and orientation of the measuring means, the information on the position and attitude of the measuring means in the movement control system of the measuring means is corrected, and the measurement data is corrected.

[0023]

The coordinate system can be determined by determining the origin position of the coordinates and the plane indicating the direction of the coordinate axes. Therefore,
A coordinate system can be determined in which the center of the fixed reference spherical body is the origin and the surface of the reference plane is the reference plane.

Next, if the positions of at least three points on the spherical surface are known, the position of the center of the sphere is obtained. That is, if the positions of three points on the spherical surface and the radius of the sphere or the positions of four points on the spherical surface are determined, the center of the sphere is determined. If the positions of the three points on the plane are known, the inclination of the plane, that is, the posture, is obtained.

Therefore, the position of at least three points on each surface of the reference spherical body and the reference plane body, which are fixed separately from the measuring means, is measured. The relative position of the center of the sphere and the relative posture of the plane of the reference plane are determined. Here, based on an absolute coordinate system determined by the center of the reference spherical body and the plane of the reference plane, the position and orientation of the measuring means in this coordinate system can be obtained.

If the method of measuring the position of a point on the reference spherical body is used to determine the origin of the absolute coordinate system, the origin itself is provided and the position can be measured by the measuring means. It is much easier to operate and more accurate. This is because, for example, even if the origin display is provided on the surface of a surface plate or the like, it is difficult to measure the measurement means accurately at the origin display position, and moreover, the physically formed origin display has Due to the constant extent, it is difficult to measure the origin in a strict sense. However, it is easy to measure the position of an arbitrary point on a reference spherical body having a certain size. In addition, no matter where the positions of the plurality of measurement points are selected, the position of the center of the sphere calculated from the positions of the measurement points is mathematically strictly determined.

If the accurate position and orientation of the measuring means are determined in this way, there is an installation error when the measuring means is installed, or a manufacturing error or an installation error occurs in the members constituting the measuring means and its moving mechanism. Even if there is an error or variation in the position determination and / or control of the measuring means inside the moving mechanism, the influence of the error or variation on the measurement result can be easily corrected.

That is, information on the position and orientation of the measuring means can be added to the calculation elements at the time of measurement without performing the work of physically adjusting or correcting the installation of the measuring means physically and accurately. Just process the information,
The displacement of the position and orientation of the measuring means is corrected, and the measurement accuracy can be improved.

Further, even if the position error due to the movement of the measuring means is accumulated by performing continuous measurement, the position of the measuring means using the reference spherical body and the reference plane body at an appropriate stage. If the information on the position and orientation of the measuring means is corrected by measuring the position and orientation of the measuring means, errors do not accumulate and do not greatly affect the measurement accuracy.

When the operation of tilting the measuring direction of the measuring means is performed in accordance with the shape of the object to be measured, the position and orientation of the measuring means can be measured using the reference spherical body and the reference plane body. Is performed to correct the information on the position and orientation associated with the inclination in the measurement direction, accurate measurement can be performed even when the measurement direction is inclined. In addition, even if a single DUT is measured in a state where the measurement direction is not tilted and in a state where the measurement direction is tilted or a state where the tilt angle is different, the measurement results in those different states are converted to the respective states. By making corrections based on the position and orientation of the measuring means in (1), all the measurement results can be processed in the same manner.

[0031]

Next, an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entire structure of the three-dimensional shape measuring apparatus. A gate-shaped support structure 22, a traveling support post 24, a turning portion 25, and a rotating arm 2 are placed on a platen 10 made of a hard plate made of hard metal, ceramics, or other highly rigid material.
6 and the like, a measuring instrument 20 as a non-contact type measuring means is attached. The support structure 22 is provided in a beam shape in the horizontal direction to both ends across the center of the surface plate 10,
The traveling support 24 can freely move horizontally along the support structure 22. In the lower part of the traveling support 24, the turning part 2
5 turns horizontally. The rotating arm 26 extending in the horizontal direction with respect to the turning portion 25 rotates in the vertical direction together with the measuring instrument 20 at the tip. By combining the movements of the traveling support 24, the turning portion 25, and the rotating arm 26, the measuring device 20 can be moved to an arbitrary position on the surface plate 10 and the inclination of the measuring device 20 can be freely changed. It has become.

An object X for measuring a three-dimensional shape is placed on the surface plate 10. A reference spherical body 40 and a reference plane body 30 are mounted on the surface plate 10 on the side of the object X. The reference plane 30 is made of a thin rectangular ceramic plate, and the surface is finished to an accurate plane. An example of the dimensions of the reference plane 30 is 5 × 1
It is about 0 cm and has a flatness of about 2 μm. The surface of the reference plane 30 is attached in parallel with the surface of the surface plate 10.

The reference spherical body 40 is a spherical body made of ceramic, and is attached to a position slightly higher than the surface of the surface plate 10 by a vertical support shaft 42 joined to the bottom.

A method for measuring the three-dimensional shape of the object X using the measuring device having the above structure will be described.

First, the measuring device 20 measures the positions of three points S _{1 to} S ₃ on the surface of the reference plane 30. When the positions of the three points on the plane are determined, the posture or inclination of the plane is known, so that the relative posture or inclination of the reference plane 30 with respect to the measuring instrument 20 is obtained. In practice, since the reference plane 30 is fixed to the surface plate 10, the measuring device 20
The relative posture or inclination of the reference plane 30 with respect to the reference plane represents the posture or inclination of the measuring device 20 with respect to the reference plane 30 or the surface plate 10.

Next, the measuring device 20 measures the positions of three points P _{1 to} P ₃ on the surface of the reference spherical body 40. When the positions of the three points on the spherical surface are determined, the radius of the reference spherical body 40 is known in advance, so that the position of the center of the reference spherical body 40 is known. This state is described in detail in FIG. 2. When the spot light R is applied to the three points P _{1 to} P ₃ to determine the respective positions, the three points P _{1 to} P ₃ are present on the surface. A sphere with a specific radius is uniquely determined. Thus, the position of the spherical center C of the reference spherical body 40 with respect to the measuring device 20 is obtained. This means that, if the center C of the spherical surface of the reference spherical body 40 is set as the origin, the position of the measuring device 20 with respect to the origin C is obtained.

As a result, the accurate attitude or inclination of the measuring device 20 with respect to the base 10, ie, the reference plane fixed to the stationary surface, and the accurate position of the measuring device 20 with the center C of the reference spherical body 40 as the origin. Is determined. In other words, the position and orientation of the measuring device 20 in the absolute coordinate system determined by the reference plane fixed to the stationary surface and the origin are determined.

The measuring device 20 controls the position and orientation of the inside of the moving mechanism based on the traveling amount and the turning amount of the traveling support 24 and the turning portion 25 as the moving mechanism. The position of the measuring device 20 is detected by various sensors provided. The deviation between the information on the position and orientation of the measuring device 20 in the coordinate system inside the moving mechanism, that is, the control coordinate system, and the position and orientation in the absolute coordinate system based on the reference plane and the origin are obtained, Correct the control coordinate system on the moving mechanism side. That is, the information of the origin and the axial direction of the control coordinate system is corrected. Instead of physically or mechanically adjusting the installation of the moving mechanism itself, it is only necessary to modify the control coordinate system as internal information such as a control program incorporated in the control device of the moving mechanism. . If the control coordinate system on the moving mechanism side is accurately corrected, the movement control of the measuring device 20 and the determination of the position and orientation can be performed using only the control coordinate system on the moving mechanism side.

The measuring operation on the object X to be measured by the measuring device 20 is performed in the same manner as in a normal three-dimensional shape measuring method. Specifically, the measuring device 2
By irradiating the spot light from 0 and catching the reflected light, the distance from the measuring device 20 to the measuring point Q, that is, the relative position from the measuring device 20 can be determined. At this time, the position and orientation of the measuring device 20 are obtained by adding the measured value at the measuring point Q to the moving amount of the measuring device 20 in the control coordinate system inside the moving mechanism, the control coordinate system and the absolute coordinate system. Since the correction is made by the deviation, accurate measurement results can always be obtained.

During the measurement while moving the measuring device 20, errors in the amount of movement inside the moving mechanism may accumulate, causing a deviation from an accurate position and posture. . In such a case, every time measurement is performed for a certain period of time, the reference spherical body 40 and the reference plane
If the coordinate system is corrected by the measurement of 0, the accumulation of errors due to the movement of the measuring device 20 can be eliminated.

If the object X is an object consisting of only a flat surface, the reflected light of the spot light R radiated vertically downward from the measuring device 20 can be reliably captured by the measuring device 20. When the measurement object X has a complicated curved surface or inclined surface, it is difficult for the measuring device 20 facing vertically downward to catch the reflected light.

Therefore, if the rotating arm 26 is turned in accordance with the shape of the object X and the measuring device 20 is tilted to change the irradiation direction of the spot light R, the inclined surface and the vertical surface of the object X can be measured. As for the measurement point Q, accurate position measurement can be performed. As described above, when the measuring device 20 is tilted, if the coordinate system is corrected by the measurement of the reference spherical body 40 and the reference plane 30 as described above, accurate measurement can be performed in the same manner as when the measuring device 20 is not tilted. Measurement can be performed. While changing the inclination of the measuring device 20 with respect to one object X depending on the location,
The three-dimensional shape of the whole object X can be accurately measured.

[0044]

According to the method and the apparatus for measuring a three-dimensional shape according to the present invention described above, the position and orientation of the non-contact type measuring means are obtained by utilizing the above-mentioned reference spherical body and reference plane body. Can be known exactly.

As a result, it is possible to easily correct a measurement error caused by an installation error of the measuring means and its moving mechanism. Rather than physically correcting the position and orientation of the measuring means and moving mechanism, it simply corrects information in the coordinate system that determines the position and orientation. It is possible.

In particular, even when the measuring means is tilted in accordance with the shape of the object to be measured, the position and orientation associated with the inclination can be easily corrected. It is possible to perform accurate measurement by moving to the position and orientation most preferable for the measurement point.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a method for measuring the position of a reference spherical body.

[Explanation of symbols]

10 plate (stationary surface) 20 meter (non-contact measurement means) 22 to 26 moving mechanism 30 reference flat body 40 reference measurement points on the sphere body C ball center Q DUT P ₁ to P ₃ a reference sphere bodies on Measurement points S _{1 to} S ₃ Measurement points on the reference plane X X DUT

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiji Hamano 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-60-205311 (JP, A) JP-A-63- 96504 (JP, A) JP-A-1-202611 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01B 21/00-21/32

Claims (4)

(57) [Claims] In a method for measuring the position of each point on an object to be measured by a movable non-contact type measuring means and measuring the three-dimensional shape of the object to be measured, a reference spherical body fixed in advance is provided. At least three points on each surface of the reference plane are measured by the measurement means relative to the measurement means, and the position of each point on the reference sphere measured here is used to measure the sphere of the reference sphere relative to the measurement means. Find the relative position of the center,
And determining the relative orientation of the reference plane relative to the measuring means from the position of each point on the reference plane, and obtaining information on the position and orientation of the measuring means based on these results. Shape measurement method. 2. The three-dimensional shape measuring method according to claim 1, wherein a fixed position of the reference spherical body and / or the reference plane body can be changed. 3. The three-dimensional shape measuring method according to claim 1, wherein the non-contact measuring means is a means using a laser. 4. A tertiary system comprising: a stationary surface on which an object to be measured is fixed; and a non-contact type measuring means which is movable with respect to the stationary surface and the object to be measured and measures the position of each point on the object to be measured. In the original shape measuring device, a three-dimensional shape is provided on the stationary surface side with a reference spherical body and a reference plane body capable of measuring positions of at least three points on the surface by the non-contact type measuring means. Measuring device.