JPH0926316A - Noncontact three-dimensional displacement detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncontact three-dimensional displacement detection apparatus by which the accuracy of the return position of a stylus of a touch probe is evaluated by a noncontact measurement without performing a mechanical driving operation. SOLUTION: A measuring member 5 is attached to the tip of a stylus 4 of a fixed touch trigger probe 3. One plane of the member 5 is imaged by imaging systems 7a, 8a from the X-axis direction. The other plane is imaged by imaging systems 7b, 8b from the Y-axis direction. Obtained images are sent to an image processor 9, straight lines which correspond to two edges on the respective images are found. The image coordinate value of the point of intersection of the two straight lines is found. In addition on the basis of the image coordinate value of the point of intersection obtained on every image, the three-dimensional coordinate value of the point of intersection of three edges of the measuring member 5 is found. Then, the stylus 4 is displaced, and the return dislocation of the tip of the stylus 4 is detected on the basis of three-dimensional space coordinate values before and after a relief operation and a return operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact three-dimensional displacement detection device for non-contact measurement and evaluation of the return accuracy of a touch probe for a three-dimensional coordinate measuring machine.

[0002]

2. Description of the Related Art A stylus attached to a touch probe for a three-dimensional coordinate measuring machine performs an escape operation when it comes into contact with a work, and returns to its original position when the external force disappears. A mechanism for performing the escape movement and the return movement of the stylus is called a seating mechanism. Usually, the touch probe is equipped with a contact sensor that detects that the stylus has contacted the work, and is configured to generate a trigger signal (for example, Japanese Patent Publication No. 58-17).
No. 402). Such a probe is called a touch trigger probe.

The return error of the high precision touch trigger probe is caused by the variation of the contact sensor (depending on the contact direction, contact speed, etc.) and the return position error of the seating mechanism (direction,
It depends on the pressing force of the spring and the speed of return). Generally, the contact sensor has sufficiently high sensitivity, the error of is smaller than the error of, and the accuracy of the touch trigger probe is mostly controlled by the seating mechanism, which causes the measurement error. Conventionally, in order to measure and evaluate the detection accuracy of this touch trigger probe, a high-precision three-dimensional coordinate measuring machine or a dedicated high-precision moving mechanism has been used. For example, a touch trigger probe is attached to the coordinate measuring machine, the stylus is brought into contact with the work, and the operation of capturing the X, Y, Z coordinate values of the coordinate measuring machine by the trigger signal is repeated, and the captured coordinate values The stylus return accuracy is measured and evaluated based on the variation of.

[0004]

However, in the conventional method, when an attempt is made to evaluate a high-precision touch trigger probe, in addition to the above-mentioned error, the three-dimensional coordinate measuring machine or the high-precision moving mechanism moves. The error caused by the vibration and the shaking caused by the error is included and cannot be separated. Therefore, there is a problem that it is not possible to measure and evaluate only the error of the touch probe itself.

The present invention has been made in consideration of the above circumstances, and non-contact three-dimensional displacement detection that enables evaluation of return position accuracy of a touch probe by non-contact measurement without performing mechanical driving. The purpose is to provide a device.

[0006]

SUMMARY OF THE INVENTION The present invention is a three-dimensional displacement detecting device for detecting a return position displacement of a stylus tip of a touch probe in a non-contact manner, and a Z in a three-dimensional space of X, Y, Z. Attached to the stylus tip of the touch probe fixed along the axis, it has two planes orthogonal to each other, and these two planes intersect with the ridge line in addition to the ridge line determined by the two planes. A measuring member having another ridge line, a first image capturing means for capturing an image including two ridge lines on one of the two planes of the measuring member in the X-axis direction, and the measurement in the Y-axis direction. Second image pickup means for picking up an image including two ridgelines on the other of the two planes of the member, and image data obtained by the first image pickup means are processed to form two ridgelines, respectively. Against A first straight line detecting means for obtaining a straight line from image coordinate values of at least two or more points, and a first straight line detecting means for obtaining an image coordinate value of an intersection of the two straight lines obtained by the first straight line detecting means. Intersection detection means,
Second straight line detecting means for processing the image data obtained by the second image pickup means to obtain straight lines respectively corresponding to the two ridge lines from image coordinate values of at least two or more points; A second intersection detecting means for obtaining the image coordinate value of the intersection of the two straight lines obtained by the second straight line detecting means, and an image coordinate value of each intersection obtained by the first and second intersection detecting means. Based on the three-dimensional position detecting means for obtaining the three-dimensional spatial coordinate value of the intersection of the three ridges of the measuring member and the three-dimensional position detecting means before and after the stylus is displaced to perform the escape operation and the return operation. A positional deviation detecting means for detecting the positional deviation of the stylus tip on the basis of the obtained three-dimensional space coordinate value is provided.

In the present invention, preferably, the measuring member attached to the tip of the stylus is a cube. Alternatively, a rectangular parallelepiped, a quadrangular pyramid or the like can be used as the measuring member.

[0008]

According to the present invention, the touch probe having the measuring member of a predetermined shape attached to the tip of the stylus is fixed in the Z-axis direction of the three-dimensional space by using an appropriate frame or the like,
It is possible to pick up two planes of the measurement member from the X and Y axis directions and perform image processing to detect the spatial coordinates of one point of the measurement member without contact. By performing this spatial coordinate detection operation before and after the stylus is given a predetermined displacement to perform the escape operation and the return operation, it is possible to detect the return position shift of the stylus tip.

Therefore, according to the present invention, since the touch probe is in a fixed state and is not mechanically driven as in the case of using a conventional three-dimensional coordinate measuring machine, the influence of vibration and shaking is eliminated, and the touch probe itself is not affected. It enables accurate measurement and evaluation of restoration accuracy. Moreover, an expensive high-precision three-dimensional coordinate measuring machine and a high-precision moving mechanism are not required.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a displacement detecting device according to an embodiment of the present invention. A touch trigger probe 3 to be measured as shown in the figure is attached and fixed to a frame 2 formed integrally with the base 1 in a suspended state along the Z axis of the three-dimensional spatial coordinates of X, Y, and Z. It Probe 3
The stylus 4 is attached to the stylus 4 to perform an escape operation and a return operation by an external force, and a measuring member 5 used for measuring the tip position of the stylus 4 is attached to the tip of the stylus 4. The measuring member 5 is a cube in this embodiment.

A magnifying optical system 7a including an illumination system is mounted on the table 6a fixed to the frame 2 in order to image the measuring member 5 at the tip of the stylus from the X-axis direction. CCD camera 8 for taking a magnified image
a is attached. Similarly, another table 6b fixed to the frame 2 has a magnifying optical system 7b and a CCD camera 8b for imaging the measuring member 5 from the Y-axis direction.
Is provided. The optical systems 7a and 7b are respectively focus-adjusted to predetermined positions on two orthogonal planes of the measuring member 5.

The image signals obtained by the CCD cameras 8a and 8b are sent to the image processing device 9 and subjected to image processing in cooperation with the host computer 10 as described later to detect a specific position of the measuring member 5. That is, the tip position of the stylus 4 is detected and the accuracy of the returning operation is evaluated. Further, in this embodiment, a linear actuator 11 is provided in order to automatically perform the escape operation and the return operation of the stylus 4. This actuator 11
Is controlled by the computer 10 to repel the stylus 4 as shown by the broken line in FIG. However, the escape operation may be performed by manually repelling the stylus tip without providing the actuator 11.

Next, a specific position measuring operation in this embodiment will be described. FIG. 2 is an enlarged view of the measuring member 5 attached to the tip of the stylus 4. The optical system 7a and the CCD camera 8a for taking an image in the X-axis direction, and the optical system 7b and the CCD camera 8b for taking an image in the Y-axis direction are arranged so as to take an image of one vertex 53 of the measuring member 5. There is. That is, the plane 51 that captures images from the X-axis side and the plane 52 that captures images from the Y-axis side are in a relationship orthogonal to each other.
From the axial direction, an image including a ridge line B determined by the two planes 51 and 52 and another ridge line A on another plane 51 is captured at the same time. From the Y-axis direction, the ridge line B
And an image including another ridgeline C on the plane 52 at the same time is captured. Then, the spatial coordinates of the apex 53 where the three ridgelines A, B and C intersect at one point are obtained.

Regarding the arrangement of the measuring member 5, it is not always necessary to make these two planes 51 and 52 orthogonal to the X axis and the Y axis of the three-dimensional space coordinates determined by the base 1 and the frame 2. . As described above, it suffices if an image including two ridgelines A, B and B, C can be picked up in each of the X and Y axis directions.

With the arrangement of the image pickup system described above, the images obtained by the CCD cameras 8a and 8b are respectively as shown in FIG.
(A) and (b) are obtained. That is, the CCD camera 8a
From FIG. 3, an image where two ridgelines A and B intersect, as shown in FIG. 3A, and from the CCD camera 8b, an image where two ridgelines B and C intersect, as shown in FIG. To be
In the image of FIG. 3A, the horizontal axis is the Y axis, the vertical axis is the Z axis,
In the image of FIG. 3B, the horizontal axis is the X axis and the vertical axis is the Z axis.
Since the ridgelines A, B, and C appear as so-called edges on the image as shown in the figure, they will be referred to as edges on the image below.

By processing the image of FIG. 3A taken from the X-axis direction by the image processing device 9, the Y of the apex 53,
The Z coordinate can be obtained, and the image is taken from the Y axis direction.
By processing the image of (b) by the image processing device 9,
The X and Z coordinates of the apex 53 can be obtained. Therefore, by repeating the escape operation and the returning operation of the stylus 4 by the actuator 11, it is possible to detect the variation in the returning position of the apex 53, that is, the variation in the returning position of the stylus 4.

Specifically, FIG. 3 taken from the X-axis direction.
Taking the image of (a) as an example, a method of detecting the apex 53, which is the intersection of two ridges, will be described below. As shown in FIG. 4A, four edge detection tools 21 to 24 are set for the image shown in FIG. These tools 21-2
Reference numeral 4 is a symbol that specifies a location from which a change point of a gray level (brightness level) of the image memory for edge detection is read out, corresponding to an address of the image memory in the image processing apparatus 9. It will always be set to the same position even if changes.

In this case, the tool 21 detects the image coordinate value of one point 31 on the edge A, and the tool 22 detects the image coordinate value of another point 32 on the edge A. Similarly, the tool 23 detects the coordinate value of one point 33 on the edge B, and the tool 24 detects the coordinate value of another point 34 on the edge B. Then, from the above detection result, a straight line connecting the points 31 and 32 is calculated, and the point 33 is similarly calculated.
Calculate a straight line connecting between and. Since these straight lines correspond to the edges A and B, respectively, the Y and Z coordinates of the apex 53 are obtained as the intersection points of these straight lines.

On the other hand, FIG. 4B shows the actuator 11
An example of detection in the case where there is an error in the return position when the stylus 4 is pushed in to perform an escape operation and then returns is shown. The edge detecting tools 21 to 24 are fixed as described above, so that the point 3 on the edge A which is displaced is displaced.
1 ', 32' and points 33 ', 34' on the edge B are detected, and the image coordinate value of the apex 53 'is obtained by the same processing as that described above.

The detectable image coordinate value is the coordinate difference from the origin on each image, but can be converted to the actual dimension if the dimension corresponding to one pixel is known. Normally, the width of a work having a known size is detected, and depending on how many pixels there are, 1
A dimension corresponding to a pixel can be calculated.

What has been described with reference to FIG. 4 is the processing of an image obtained by the image pickup system in the X-axis direction. What is required for this is the apex 53 on the YZ plane before and after the escape and return operations. The coordinate difference is 53 '. Although not shown in the figure, Y
The displacement of the apex 53 on the XZ plane can be detected by performing the same processing on the captured image from the axial direction. Then, from these detection results, it is possible to detect the return position shift of the vertex 53 in the X, Y, Z three-dimensional space coordinates.

The above sequence of image processing is controlled by the host computer 10. The outline of the control flow is shown in FIG. As mentioned above, X
The X, Y, and Z coordinates of the apex 53 of the measuring member 5 are calculated based on the captured images from the axial direction and the Y-axis direction (S
1). Further, the actuator 11 is driven to perform the escape operation and the return operation of the stylus 4 (S2), and the X, Y of the apex 53 'of the measuring member 5 is based on the captured images from the subsequent X-axis direction and Y-axis direction. , Z coordinate is calculated (S
3). Then, the return position shift is calculated from the difference between the coordinates of the vertex 53 and the coordinates of the vertex 53 '(S4). Hereinafter, the same processing is repeated a necessary number of times while determining the number of repetitions (S5).

If the above image processing is represented by functional blocks, it becomes as shown in FIG. First straight line detecting means 61a
Is processing image data obtained by the CCD camera 8a that captures an image in the X-axis direction, and obtains straight lines respectively corresponding to the two ridgelines A and B from image coordinate values of two points. The first intersection detecting means 62a obtains the image coordinate value of the intersection of the two straight lines obtained by the first straight line detecting means 61a. The second straight line detecting means 61b is
The image data obtained by the CCD camera 8b that captures an image in the Y-axis direction is processed to obtain straight lines corresponding to the two ridge lines from the image coordinate values of the two points, respectively, and the second intersection point detecting means 62b is obtained. Calculates the image coordinate value of the intersection of the two straight lines obtained by the second straight line detecting means 61b.

The three-dimensional position detecting means 63 detects the intersection 53 of the three ridges of the measuring member 5 based on the image coordinate values of the respective intersections obtained by the above-mentioned first and second intersection detecting means 62a and 62b. The three-dimensional spatial coordinate values of X, Y, Z are obtained. Then, the positional deviation detecting means 64 detects the returning positional deviation of the stylus tip based on the three-dimensional spatial coordinate values obtained by the three-dimensional position detecting means 63 before and after the stylus 4 is displaced to perform the escape operation and the return operation. To do.

In the above embodiment, the measuring member 5 attached to the tip of the stylus 4 is a cube, but it may be a rectangular parallelepiped as shown in FIG. 7 (a). Also in this case, as indicated by reference numerals corresponding to FIG. 2, two planes 5 orthogonal to each other are provided.
1, 52 with two ridges A and B on one plane 51
And has two ridgelines B and C sharing the ridgeline B on the other plane 52 and having a vertex 53 intersecting with one of these three ridgelines A, B and C. Thus, the accuracy of the return position of the stylus 4 can be detected. The same applies to a horizontally long rectangular parallelepiped instead of a vertically long rectangular parallelepiped.

Further, the measuring member 5 may be a quadrangular pyramid as shown in FIG. 7 (b). Also in this case, the reference numerals corresponding to those in FIG. 2 are attached. The two planes 51 and 52 are also orthogonal to each other, and two ridge lines A, B and B, C appear on each plane 51, 52, and a vertex 53 as an intersection of them appears. 4 return position detection is possible.

In the embodiment, the two-point detection is used to obtain the linear equation on the captured image of the ridgeline of the measuring member.
A straight line may be obtained by performing multi-point detection of two or more points, which enables more accurate position detection. In the example, the touch-trigger probe to be evaluated was attached to the frame to perform non-contact measurement, but the same non-contact measurement was performed without driving the measurement instrument in a state where the touch-trigger probe was attached to, for example, a three-dimensional coordinate measuring instrument. It is possible to detect and evaluate the return position accuracy of the stylus by performing.

[0028]

As described above, according to the present invention, the touch probe having the measuring member of a predetermined shape attached to the tip of the stylus is fixed in the Z-axis direction of the three-dimensional space,
Two planes of the measuring member are imaged from the X and Y axis directions, the spatial coordinates of one point of the measuring member are detected by image processing in a non-contact manner, and this spatial coordinate detecting operation is performed by giving a predetermined displacement to the stylus and escaping. By performing before and after performing the return operation, the return position shift of the stylus tip can be detected. According to the present invention, unlike the case where the touch probe is mechanically driven by the three-dimensional coordinate measuring machine, the influence of vibration, shaking, etc. is eliminated, and the accurate return accuracy of the touch probe itself can be measured and evaluated.

[Brief description of drawings]

FIG. 1 shows a configuration of a displacement detection device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a measuring member used in the same example.

FIG. 3 shows two captured image examples of the same embodiment.

FIG. 4 is a diagram for explaining an image processing operation of the embodiment.

FIG. 5 shows a control flow of image processing of the embodiment.

FIG. 6 shows functional blocks of image processing of the embodiment.

FIG. 7 shows a measuring member used in another embodiment.

[Explanation of symbols]

1 ... Base, 2 ... Frame, 3 ... Touch trigger probe, 4 ... Stylus, 5 ... Measuring member, 6a, 6b ... Table, 7a, 7b ... Enlarging optical system, 8a, 8b ... CCD camera, 9 ... Image processing device, 10 ... Host computer.
51, 52 ... Plane, A, B, C ... Ridge line, 53 ... Vertex.

Claims (2)

[Claims] 1. A three-dimensional displacement detection device for detecting a return position displacement of a stylus tip of a touch probe in a non-contact manner, the touch being fixed along a Z-axis of a three-dimensional space of X, Y, Z. A measuring member attached to the tip of the stylus of the probe and having two planes orthogonal to each other, and each of these two planes having a ridge line defined by the two planes and another ridge line intersecting with the ridge line at one point. And a first imaging unit that captures an image including two ridges on one of the two planes of the measurement member in the X-axis direction, and the other of the two planes of the measurement member in the Y-axis direction Second image pickup means for picking up an image including two ridgelines on the plane, and the image data obtained by the first image pickup means are processed to reduce straight lines respectively corresponding to the two ridgelines. First straight line detecting means for obtaining from image coordinate values of at least two points, and first intersection point detecting means for obtaining image coordinate values of intersection points of two straight lines obtained by the first straight line detecting means. Second line detection means for processing the image data obtained by the second image pickup means to obtain straight lines respectively corresponding to the two ridge lines from image coordinate values of at least two or more points, Second intersection point detecting means for obtaining the image coordinate value of the intersection point of the two straight lines obtained by the second straight line detecting means, and image coordinate value of each intersection point obtained by the first and second intersection point detecting means And a three-dimensional position detecting means for obtaining a three-dimensional spatial coordinate value of an intersection of three ridge lines of the measuring member, and the three-dimensional position detection before and after the stylus is displaced to perform an escape operation and a return operation. Non-contact 3D displacement detecting apparatus characterized by comprising a displacement detection means for detecting a return position displacement of the stylus tip on the basis of the three-dimensional space coordinate values obtained by means. 2. The non-contact three-dimensional displacement detection device according to claim 1, wherein the measuring member is a cube.