JPH06258022A - Measuring method of hole position - Google Patents

Abstract

PURPOSE:To allow highly accurate measurement of the central position of a circular hole made in a work. CONSTITUTION:The surface of a work W is irradiated with horizontal and vertical slit lights 101, 102 projected from light sources 11, 12 while traversing a circular hole Wa and the image thereof is picked up by means of cameras 21, 22. Optical axis of one slit light 101 is inclined significantly so that the slit light 10, does not impinge on the inner peripheral face of the hole on the side of point A thus preventing the point A from shifting from the edge of the circular hole Wa due to the slit light image of the inner peripheral face of the hole. Two circles having a predetermined diameter corresponding to that of the hole Wa are drawn, while passing through points A, C and point A, D, on a plane including the point A and two end points C, D of the irradiating image of the slit light 102 and the intermediate point between the centers of both circles is determined as the central position of the circular hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hole position measuring method for optically measuring the center position of a circular hole formed in a work.

[0002]

2. Description of the Related Art Conventionally, as a measuring method of this kind, according to Japanese Patent Laid-Open No. 3-160303, as shown in FIG. 5, two slit lights a and b intersecting each other across a circular hole Wa are formed on the surface of a work W. Irradiation, and the irradiation image of these slit lights is picked up by one camera c having an optical axis oblique to the optical surfaces of both slit lights, and irradiation of one slit light a that matches the edge of the circular hole Wa. The positions of the two end points a1 and a2 of the image and the two end points b1 and b2 of the irradiation image of the other slit light b are detected, and the perpendicular bisector of the connection line between a1 and a2 and b1 and b2.
It is known that the center position of the circular hole Wa is indexed as the intersection of the two connections with the perpendicular bisector. Here, since each of the slit lights a and b obliquely intersects the line of sight of the camera c, the irradiation image of each slit light becomes a light-section image, and the analysis method of light-section is performed from the position of each end point on the screen of the camera. Based on this, the spatial coordinate value of each end point can be calculated, and thus the center position of the circular hole Wa in the spatial coordinate system can be obtained.

[0003]

By the way, the circular hole Wa
When is displaced from the position directly facing the camera c, an image of the slit light irradiated on the inner peripheral surface of the hole in the displacement direction is also captured. For example, when the end point a1 is displaced from the line of sight of the camera c,
On the screen of the camera c, the end point a1 shifts inward by the plate thickness of the work, resulting in a measurement error of the center position of the circular hole Wa. In view of the above points, an object of the present invention is to provide a method capable of more accurately measuring the center position of a circular hole.

[0004]

[Means for Solving the Problems] In order to achieve the above object,
The present invention is a method for optically measuring the center position of a circular hole formed in a work, which comprises irradiating the surface of the work with two slit light beams, a first slit light beam and a second slit light beam that intersect each other across the circular hole. The irradiation image of the slit light is taken by the imaging means,
In the one in which the position of the end point of each irradiation image that matches the hole edge of the circular hole is detected and the center position of the circular hole is indexed from the position of these end points, one of the first slit light of the both slit light is a circular hole. Even if the predicted maximum deviation of the first slit light is generated, the first slit light does not hit the inner peripheral surface of the circular hole on the side of one of the two end points of the irradiation image of the first slit light, The surface of the work is irradiated, and the spatial coordinate values of the first end point and the second end point of one of the two end points of the irradiation image of the second slit light and the third end point of the other end point are displayed on the screen of the imaging means. A circle that is calculated from the position of each end point and that is drawn on a plane including these three end points in the spatial coordinate system and has a predetermined diameter corresponding to the hole diameter of the circular hole and that passes through the first end point and the second end point. And a center coordinate value of a circle passing through the first end point and the third end point, And obtaining the middle point of the center of these two circles centered position of the circular hole.

[0005]

[Function] The first slit which is one of the end points of the irradiation image of the first slit light
Since the first slit light does not impinge on the hole inner peripheral surface on the end point side, the position of the first end point can be accurately detected, but the hole inner peripheral surface on the other end point side of the irradiation image of the first slit light does not have the first slit light. Since one slit light hits, the position of the other end point cannot be accurately detected, and therefore the positions of the first end point and the second and third end points of the irradiation image of the second slit light, the total of three end points. The center position of the circular hole is obtained from. in this case,
Obtaining the equation of a circle drawn on a plane in a spatial coordinate system including these three end points and passing through these three end points,
Although it is conceivable to use the center coordinates of this circle as the center position of the circular hole, there may be some error in the positions of the second and third end points, and due to this error, the circle passing through the three end points The diameter of the circle may greatly differ from the diameter of the circular hole, and the center of the circle may deviate from the actual center of the circular hole. On the other hand, the diameters of the two circles drawn in the present invention are preliminarily set to values corresponding to the hole diameters of the circular holes, and both circles pass through the highly accurate first end point. The middle point of the center does not shift to the left from the center of the circular hole,
The center position of the circular hole can be accurately measured.

[0006]

FIG. 1 shows an outline of an apparatus for measuring the position of a circular hole Wa formed in a work W. The apparatus comprises a pair of first and second slit light sources 1 ₁ , 1 ₂ . First and second one
It is composed of a pair of cameras 2 ₁ and 2 ₂ and a computer 3 which inputs image signals from the cameras 2 ₁ and 2 ₂ . The slit light sources 1 ₁ and 1 ₂ and the cameras 2 ₁ and 2 ₂ are mounted on a support frame (not shown) attached to the operating end of a robot or the like in a required positional relationship, and are moved and set to a predetermined measurement position facing the work W. .

The first slit light source 1 ₁ is configured to emit the horizontal first slit light 10 ₁ , and the second slit light source 1 ₂ is configured to emit the vertical second slit light 10 _2. Accordingly, the linear irradiation images of the slit lights 10 ₁ , 10 ₂ which are irradiated on the surface of the work W so as to traverse the circular hole Wa are captured by the both cameras 2 ₁ , 2 ₂ . Two left and right end points A and B that match the hole edge of the circular hole Wa appear in the irradiation image of the first slit light 10 ₁ , and also in the irradiation edge of the circular hole Wa in the irradiation image of the second slit light 10 _2. Up and down 2
Two endpoints C and D appear.

Both cameras 2 ₁ , 2 ₂ have their optical axes 0 ₁ , 0 _{2 respectively.}
Are arranged so as to cross obliquely as shown in FIG. 2 on a horizontal plane that coincides with the optical plane of the first slit light 10 ₁ , and the horizontal coordinate axis of the second slit light 10 ₂ on the horizontal plane in the optical axis direction. Is the X-axis, the horizontal coordinate axis orthogonal thereto is the Z-axis, the vertical coordinate axis orthogonal to the horizontal plane is the Y-axis, and the coordinate value of each end point in the spatial coordinate system with the origin 0 at the intersection of the optical axes 0 ₁ and 0 ₂ is It is calculated from the positions of the respective end points on the screen of both cameras 2 ₁ , 2 ₂ by the principle of triangulation method. The screens of the first camera 2 ₁ and the second camera 2 ₂ in the state of FIG.
As shown in (a) and (b) of the figure, when the horizontal x-axis and the vertical y-axis are taken on the screen with the center point corresponding to the origin 0 as the origin, the x-axis coordinate value of the screen and y The axial coordinate values represent the horizontal distance and the vertical distance from the origin 0 on the projection planes Q ₁ and Q _{2 of the} cameras 2 ₁ and 2 ₂ in the spatial coordinate system.
For example, consider the point A, the first camera 2 ₁ projection plane Q ₁
Horizontal distance x-axis coordinate value x ₁ next to the point A on the first camera 2 ₁ screen from the origin 0 of the projection point A ₁ of the point A to, likewise the second camera 2 ₂ to the projection plane Q ₂ The horizontal distance from the origin 0 of the projected point A ₂ of the point A is x of the point A on the screen of the second camera 2 _2.
The axis coordinate value becomes x ₂ . Then, the equation of the line of sight e ₁ drawn from the first camera 2 ₁ to A ₁ is obtained from x _1, and the equation of the line of sight e ₂ drawn from the second camera 2 ₂ to A ₂ is obtained from x ₂ , The X-axis coordinate value and the Z-axis coordinate value of point A in the spatial coordinate system can be calculated as the intersections. Incidentally, A
Since the point is the end point of the first radiation image of the slit light 10 ₁ matching the X-Z coordinate plane, Y-axis coordinate value of the point A becomes zero, Y-axis coordinate value as point C or point D For the end points that do not become zero, X of the line of sight of each camera 2 ₁ , 2 ₂ with respect to the end points
-The equation of the projection line on the Z coordinate plane is obtained from the x-axis coordinate value of the end point on the screen of each camera 2 ₁ , 2 ₂ , and as the intersection of both projection lines, the X-axis coordinate value of the end point and the Z-axis are the same as above. The coordinate value is calculated, and the distance between the first camera 2 ₁ and a plane including the intersection point parallel to the projection plane Q ₁ of one of the cameras, for example, the first camera 2 ₁ , is obtained. The ratio of this distance to the distance between the first camera 2 ₁ and its projection plane Q ₁ is multiplied by the y-axis coordinate value of the end point on the screen of the first camera 2 ₁ to obtain the Y-axis coordinate value of the end point. Calculate.

It should be noted that the optical axes are both the first and second slit light beams 10
_{It is also} possible to use one camera arranged so as to be oblique to the optical planes of ₁ and 10 ₂ and calculate the spatial coordinate value of each end point by the light-cutting analysis method as in the above-described conventional technique.

By the way, the first slit light source 1 ₁ has a hole on the side of one end point of the irradiation image of the first slit light 10 ₁ , for example, on the left side point A side even if the circular hole Wa has the maximum expected deviation. To prevent the first slit light 10 ₁ from hitting the inner peripheral surface,
It is arranged at a large inclination to the left, so that the point A exactly coincides with the hole edge of the circular hole Wa, but the first slit light 1
The first slit light 10 ₁ impinges on the hole inner peripheral surface on the B point side, which is the other end point of the irradiation image of 0 ₁ , and in the state of FIG. 2, the hole inner peripheral surface on the B point side on the screen of the second camera 2 _2. The image of the first slit light 10 ₁ radiated on the image of the first slit hole 10 ₁ is reflected, and the right end point B of the irradiation image of the first slit hole 10 ₁ is at the work W from the hole edge of the circular hole Wa.
It will be displaced inward by the plate thickness of. Therefore, B point is not used for the measurement of the hole positions, as follows, based on the position of the total three end points of the two end points serving points C and D of the A point and the irradiation image of the second slit light 10 ₂ The center position of the circular hole Wa is indexed.

That is, the spatial coordinate values of the points A, C and D are calculated as described above, the equation of the plane P including these three points as shown in FIG. 4 is obtained in the spatial coordinate system, and the equation is drawn on the plane. An equation of a first circle S1 passing through the points A and C and a second circle S2 passing through the points A and D, which is a circle having a predetermined diameter corresponding to the diameter of the circular hole Wa to be formed, Both circles S1 and S2
From the spatial coordinate values of the centers M1 and M2 of the
The spatial coordinate value of the midpoint M is calculated, and the position of the midpoint M is set as the center position of the circular hole Wa. Here, the points C and D may not exactly coincide with the hole edge of the circular hole Wa, but the diameters of both circles S1 and S2 are predetermined and both circles S1 and
Since both S2 pass through the point A with high accuracy, both circles S1,
The midpoint M of the centers M1 and M2 of S2 does not deviate to the left from the center of the circular hole Wa, and the equation of a circle passing through the three points A, C, and D is obtained, and the center of the circle is defined as the center of the circular hole. The center position of the circular hole Wa can be measured more accurately than in the case of performing.

[0012]

As is apparent from the above description, according to the present invention, even if the work is displaced to some extent, one of the two end points of the irradiation image of the first slit light is the first end point. Accurately matches the edge of the circular hole, and even if the positions of the second and third end points of the irradiation image of the pair 2 slit light include some errors, the first and second end points are The position of the midpoint between the center of the circle of the predetermined diameter passing through and the center of the circle of the predetermined diameter passing through the first and third end points does not deviate to the left from the center of the circular hole, and the center position of the circular hole is accurate. It can be measured well.

[Brief description of drawings]

FIG. 1 is a perspective view showing an outline of an example of a measuring apparatus used for carrying out the method of the present invention.

FIG. 2 is a plan view of the main part.

3A and 3B are diagrams showing screens of respective cameras.

FIG. 4 is a diagram showing a circle drawn so as to pass through end points.

FIG. 5 is a perspective view of a conventional example.

[Explanation of symbols]

W workpiece Wa circular hole 1 _1, 1 ₂ slit light source 10 ₁ first slit light 10 ₂ second slit light 2 _1, 2 ₂ camera (imaging means) A first end point C second end point D third endpoint S1, S2 yen M1, M2 Circle center M Midpoint center of two circles (center of circular hole)

Claims (1)

[Claims] 1. A method for optically measuring the center position of a circular hole formed in a work, comprising irradiating the surface of the work with first and second slit light beams that intersect each other across the circular hole. An image of these slit light irradiation images is picked up by an image pickup means to detect the position of the end point of each irradiation image that matches the hole edge of the circular hole, and the center position of the circular hole is calculated from the position of these end points. The first slit light of one of the two slit lights is not changed to the first slit light even if the predicted maximum deviation of the circular hole occurs.
The surface of the work is irradiated so that the first slit light does not hit the inner peripheral surface of the circular hole on the side of the first end point of one of the two end points of the irradiation image of the slit light, and the first end point and the second end point are irradiated. The spatial coordinate values of one of the two end points and the other third end point of the two end points of the irradiation image of the slit light are calculated from the position of each end point on the screen of the image pickup means, and these 3 in the spatial coordinate system are calculated.
A circle having a predetermined diameter corresponding to the diameter of a circular hole drawn on a plane including two end points, the center coordinate value of a circle passing through the first end point and the second end point, and the first end point and the third end point. A method for measuring a hole position, characterized in that the center coordinate value of a circle passing through is calculated, and the midpoint between the centers of these circles is determined as the center position of the circular hole.