JP2000337834A - Shape measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measuring device capable of measuring the shape of an object even if a part of markers of a measuring head is unrecognizable. SOLUTION: In the shape measuring device in which the three-dimensional shape of an object to be measured is measured by converting a point of measurement of an object to be measured picked up by the measuring head 10 in a coordinate system centering a measuring head 10 into coordinates in a world coordinate system on the basis of locational information obtained on the basis of the image of markers 14 of the measuring head 10 picked up by a stereo camera 21, corresponding markers 14 are distinguished on the basis of the arrangement of the image of the markers 14 picked by the stereo cameras 21 and 22, or corresponding markers 14 are distinguished by tracking the movement of the image of the markers 14 to obtain information on the locations of the markers 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring device for measuring a three-dimensional shape of an object by freely moving a measuring head by a user.

[0002]

2. Description of the Related Art Conventionally, there has been known an active stereo type shape measuring apparatus which irradiates spot light or slit light to an object to be measured and restores a shape from a position of an optical image observed on a surface.

As an active stereo shape measuring device, there is one that scans slit light with a rotating mirror.
In a shape measuring device provided with such a scanning mechanism,
Although the shape of the surface of the measured object observed from the measuring instrument can be measured, the shape of the entire measured object cannot be measured.

On the other hand, in order to measure the shape of the whole object to be measured, a rotary stage is used to move the object to be measured in 360.
An active stereo shape measuring device for observing from all around the degree has been developed. However, when the object to be measured has a complicated shape, there is an area that cannot be observed even by using the rotary stage, and therefore, the shape of the entire object to be measured cannot be measured.

On the other hand, a shape measuring apparatus which can measure the entire shape of an object having a complicated shape by grasping the measuring head by the measurer and moving the measuring head around the object to perform measurement is known. Proposed.

[0006]

However, in order to measure the position and orientation of the measuring head, it is necessary to associate the marker image photographed by the camera with the marker position on the measuring head. If a part of the marker goes out of the common field of view of the two cameras or is hidden by the hand of the measurer holding the measurement object or the measurement head,
There is a problem that it is not possible to recognize which marker image of the measuring head is the image of the marker captured by the camera, and it becomes impossible to measure the shape of the measured object.

Accordingly, an object of the present invention is to provide a shape measuring apparatus capable of measuring the shape of an object even when a part of a marker of a measuring head cannot be recognized.

[0008]

According to the present invention, there is provided a shape measuring apparatus having at least four markers, which can be freely moved by a measurer, and a coordinate system of the center of the measuring head using the measuring head. Measurement point coordinate calculation means for obtaining the coordinates of the measurement point on the DUT, measurement head imaging means for imaging the measurement head from a predetermined position, and a measurement head in the world coordinate system using the measurement head imaging means Measuring head position calculating means for obtaining information on the position of the measuring head, and a coordinate system of the center of the measuring head obtained by the measuring point coordinate calculating means based on the information on the position of the measuring head obtained by the measuring head position calculating means. And a coordinate conversion means for converting the coordinates of the measurement point on the object to be measured into coordinates in the world coordinate system. A head position calculating unit configured to identify a marker corresponding to each marker image based on an arrangement of the marker image captured by the measurement head imaging unit; A shape measuring device comprising: marker tracking means for tracking movement; and means for obtaining information on the position of a measuring head based on the position of each marker image in a world coordinate system.

With this configuration, three or more of the plurality of markers attached to the measuring head are
If the image is taken by the measurement head imaging means and is tracked by the marker tracking means, information on the position of the measurement head is obtained from those marker images.

More specifically, the measuring head position calculating means includes:
When the movement of all the marker images can be tracked by the marker tracking means, each marker image identifies the corresponding marker by the marker identification means. When there is a marker image whose movement cannot be tracked by the marker tracking means, tracking can be performed. The marker image corresponding to the moved marker image is identified based on the identification result of the marker image before the movement.

With such a configuration, in addition to the tracking by the marker image tracking means, when all the markers have been tracked, the marker image is further identified by the marker identification means.

Further, the measuring head position calculating means includes a marker number detecting means for detecting the number of marker images picked up by the measuring head image picking up means, and the number of marker images detected by the marker number detecting means is determined. When the number of markers is the same as the number of markers attached to the measurement head, each marker image identifies the corresponding marker by the marker identification means, and the number of marker images detected by the marker number detection means is attached to the measurement head. When the number is smaller than the number of markers, each marker image identifies a corresponding marker by the marker tracking means.

With such a configuration, the marker identifying means and the marker tracking means are selectively used in accordance with the number of marker images picked up by the image pickup means, and the marker images are identified.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. [1] Description of Measurement Principle FIG. 1 shows a schematic configuration of a shape measuring apparatus according to an embodiment of the present invention.

The device under test 100 is placed on a table 201. The support 201 is attached to the base 201. A horizontal bar 203 is attached to an upper part of the support column 202.

The shape measuring device is composed of a measuring head 10 that can be freely moved by a measurer, stereo cameras 21 and 22 attached to both ends of a horizontal bar 203, and a personal computer that controls them and performs various calculations. And a control device 30. The imaging lens of each of the stereo cameras 21 and 22 has a marker 14 shown in FIG.
A band-pass filter 23 for selectively transmitting the frequency band of light emitted by the light source is attached.

FIG. 2 and FIG. 3 show a schematic configuration of the measuring head 10.

The measuring head 10 has a rectangular parallelepiped casing 11 having a front opening, one CCD camera 12 and a slit light source 13 housed in the casing 11, and six LED light sources 14a provided on the upper surface of the casing 11. ~ 1
And a marker 14 made of 4f. As the slit light source 13, a semiconductor laser is used.

Six LED light sources 1 constituting the marker 14
Reference numerals 4a to 14f are not point-symmetrically arranged to specify the direction of the measuring head 10, but are arranged line-symmetrically with respect to the center line of the measuring head 10. Here, the casing 1
LED light sources 11b, 11c, 11d, 11
The five points e and 11f are arranged so as to form a rectangle, and the LED light source 11a is arranged at the center of gravity of the five points. In addition,
In order to measure the position and direction of the measuring head 10 in a three-dimensional space, it is sufficient to use at least three LED light sources as markers, but by using four or more LED light sources, The accuracy of the measurement of the position and direction of is improved in a least square manner.

FIG. 4 shows the measurement principle of the shape measuring device.

The coordinates of a measurement point A are measured by using a measurement head 10 which can be freely moved by a measurer.
The measured coordinates are represented by coordinates (x, y, z) in the coordinate system of the center of the measuring head. This coordinate system corresponds to the measuring head 10
Is a coordinate system that moves with the movement of.

On the other hand, the shape of the DUT 100 is represented by a fixed coordinate system, and this coordinate system is called world coordinates. The coordinates of the measurement point measured by the measurement head 10 in the world coordinate system are (X, Y, Z). DUT 10
Since the shape of 0 needs to be described in the world coordinate system,
The coordinates (x, y, z) of the measurement point A measured by the measurement head 10 in the coordinate system of the center of the measurement head are converted to the world coordinate system. This conversion is performed using the rotation matrix R representing the movement of the measuring head 10 and the translation vector t based on the following equation 1.

[0023]

(Equation 1)

Therefore, the position and direction of the measuring head 10 in the world coordinate system are obtained as a rotation matrix R and a translation vector t, so that the coordinates (x, y, z) of the center of the measuring head in the coordinate system can be obtained. Can be converted to

The above-described processing is performed while moving the measuring head 10 around the measured object 100, and a set of coordinates (X, Y, Z) in the world coordinate system of the measured points obtained each time is obtained as a set of the measured object. 100 shapes are described.

The shape measurement by this shape measuring device is executed according to the following processing procedure.

First step: Using the measuring head 10,
The coordinates of the measurement point on the measured object in the coordinate system of the center of the measurement head are obtained.

Second step: Information on the position of the measuring head 10 in the world coordinate system, that is, a rotation matrix R and a translation vector t representing the movement of the measuring head 10 in the world coordinate system are provided on the measuring head 10. Marker 1
4 is obtained by measuring stereo images with the stereo cameras 21 and 22.

Third step: Based on the rotation matrix R and the translation vector t obtained in the second step, the coordinates of the measuring point on the object to be measured in the coordinate system of the center of the measuring head obtained in the first step are Convert to world coordinates.

Hereinafter, each of these steps will be described. [2] Description of First Step FIG. 5 shows a method of measuring the position of a measuring point by the measuring head 10.

The coordinate system of the center of the measuring head is such that the optical center of the CCD camera 12 is the origin, the optical axis direction is the z axis, and the CCD
This is a coordinate system in which the horizontal direction of the camera 12 is the x axis and the vertical direction of the CCD camera 12 is the y axis. The image plane S of the CCD camera 12 is located at a focal distance f from the origin. That is, the image plane S is a plane parallel to the xy plane and z = f.

The position measuring method itself by the measuring head 10 is a known measuring method called a light section method. A predetermined point on a line on the surface of the DUT 100 on which the slit light from the slit light source 13 is irradiated is defined as a measurement point A.

The coordinates of the center of the measuring head at the measuring point A are (x, y, z), and the coordinates of the observation point A 'corresponding to the measuring point A on the image plane S are (xs, ys, f). , And the equation of the plane representing the slit light is ax + by + cz + d = 0. F at the coordinates (xs, ys, f) of the observation point A '
Is known as the focal length of the CCD camera 12,
(Xs, ys) is obtained from the pixel position of the slit light observed on the image plane.

The equation of the plane representing the slit light is obtained by calibrating the measuring head 10. Therefore,
(x, y, z) is obtained by solving a simultaneous equation represented by the following Expression 2 with x, y, z, and α as unknowns.

[0035]

(Equation 2)

This processing is performed by the control device 30 based on the output of the CCD camera 12. [3] Description of Second Step FIG. 6 is a flowchart showing the processing order of the second step. A series of processing described below is performed by the stereo camera 2
This is performed by the control device 30 on the basis of the outputs of the signals 1 and 22.

In the second step, first, binarization processing is performed on the captured images of the stereo cameras 21 and 22 using a predetermined threshold. At this time, the images captured by the stereo cameras 21 and 22 are captured through the band-pass filter 23, and are binarized to obtain the LED.
A plurality of images including the light sources 14a to 14f are extracted. (Steps S01 and S02) Further, for each image extracted by this binarization processing,
The size and average luminance value are calculated, and an image whose calculated value is larger than a predetermined threshold is extracted. The images extracted by the binarization processing usually include LED light sources 14a to 14
Although noise components other than the image of f are included, those noise components are removed by noise removal processing using a threshold value because the noise components are smaller in size and luminance value than the images of the LED light sources 14a to 14f. (Step S03) Next, the remaining image (tracking target image) from which noise components have been removed by the noise removal processing is compared with the images (tracking reference images) of the LED light sources 14a to 14f specified in the previously captured image. By associating, the movement from the tracking reference image to the tracking target image is tracked. For this tracking processing, a known method such as a cross-correlation method is used. (Step S0
4) Then, when tracking is performed for all tracking reference images,
Each of the tracking target images and the LED light sources 14a to 14f are associated again based on the arrangement of the tracked tracking target images. Specifically, the center of gravity is calculated for the six tracked tracking target images, and the tracking target image closest to the center of gravity is LE.
The D light source 14a is identified as an image and its LED
The tracking target image closest to the image of the light source 14a is
b. Then, with respect to the remaining four tracking target images, the LED light sources 14c, 14d, 14e, and 14 are clockwise each based on the image of the LED light source 14b.
identified as an image of f. (Steps S05 and S06) Then, a part of the LED light sources 14a to 14f of the measuring head 10 is out of the common field of view of the stereo cameras 21 and 22, or is hidden by the measurer's hand, and the tracking target image is obtained. If the tracking cannot be performed, that is, if there is an image for which no tracking target image exists, if at least three of the other tracking reference images can be tracked,
Based on the tracking result, an image of the corresponding LED light source is identified. If the number of tracking reference images for which tracking has been performed is less than three, the position and direction of the measuring head 10 cannot be specified, and the process is stopped. (Step S
07 to S09) From the images of the LED light sources 14a to 14f (if not all of the images of the LED light sources 14a to 14f are identified) in each of the stereo cameras 21 and 22 identified in this way, a stereo image is obtained. The coordinates of the LED light sources 14a to 14f in the world coordinate system are calculated using a well-known technique. (Step S1
0) Next, a rotation matrix R representing the movement of the measuring head 10 and a translation vector t are obtained. That is, the coordinates of the center of the measurement head of each of the LED light sources 14a to 14f that are known in advance are (xi, yi, zi). Here, i is an integer whose maximum value is the number of identified images among the images of the LED light sources 14a to 14f. The coordinates of the LED light sources 14a to 14f measured by the stereo cameras 21 and 22 in the world coordinate system are defined as (Xi, Yi, Zi).
A rotation matrix R and a translation vector t representing the movement of the measuring head 10 are obtained as a matrix R and a vector t satisfying the following Expression 3. The calculation of the rotation matrix R and the translation vector t is performed by the control device 30. (Step S1
1)

[0038]

(Equation 3)

[4] Description of Third Step Rotation matrix R and translation vector t obtained in the second step
And coordinates (x, y, z) of the center of the measurement point at the measurement point measured by the measurement head 10 using the above equation (1).
Is converted into world coordinates (X, Y, Z), whereby the coordinates of the measurement point in the world coordinate system are obtained. This coordinate conversion is performed by the control device 30.

As described above, according to the present embodiment, even when all of the images of the LED light sources 14a to 14f of the measuring head 10 cannot be recognized, the measurement of the object to be measured can be performed. The measurement error caused by the method and the measurement position is reduced, and a highly reliable shape measurement can be performed.

When all the tracking reference images can be tracked, the tracking reference images are again associated with the LED light sources 14a to 14f based on the arrangement of the tracked target images. Even in this case, since the position of the measuring head in the world coordinate system is obtained using the maximum number of tracking target images that can be tracked, the stereo cameras 21 and 22 are used.
It is possible to perform measurement with as high accuracy as possible in accordance with the imaging state of.

The measuring head 10 may be different from the above-described embodiment as long as it measures the position of the measuring point on the object to be measured by an active stereo measuring method. For example, a spot light source may be used instead of the slit light source 13. Alternatively, the position of the measurement point (the coordinates of the center of the measurement head) may be measured by two CCD cameras.

As the marker 14, the LED light sources 14a to 14a
It is not limited to 14f but may be any that can be extracted by a stereo camera. For example, LED light sources 14a-
A seal having a high reflectance may be used instead of 14f.
The number of the markers 14 may be four or more.

In the above-described embodiment, when the tracking process is performed, if the tracking can be performed from all the tracking reference images, the LED light source 1 is returned based on the arrangement of the tracked tracking target images.
4a to 14f are configured to be associated with each other. After counting the number of tracking target images, the configuration is such that the tracking target images are associated with the LED light sources 14a to 14f based on the count value. May be. In this case, if the count value matches the number of the LED light sources 14a to 14f of the measurement head 10, the LED is determined based on the arrangement of each tracking target image.
If the count value is less than the number of the LED light sources 14a to 14f of the measurement head 10, the LED light sources 14a to 14f are tracked.
14f and the LED light sources 14a to 14a
The 4f image is identified. If the count value is less than 3, the measurement is stopped and the process is stopped.

In this case, when the recognition process based on the arrangement is possible, the tracking target image and the LE are more accurately compared with the tracking process.
Since recognition processing capable of associating with the D light sources 14a to 14f is used, and tracking processing is used when the recognition processing is not possible, tracking processing and recognition processing do not overlap, and processing is speeded up. It becomes possible.

[0046]

According to the present invention, an object to be measured can be measured even when a part of the marker image of the measuring head cannot be recognized. Mistakes are reduced, and highly reliable shape measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a shape measuring device according to an embodiment of the present invention.

FIG. 2 is a front view showing a configuration of a measuring head.

FIG. 3 is a plan view showing a configuration of a measuring head.

FIG. 4 is an explanatory diagram illustrating a measurement principle.

FIG. 5 is an explanatory diagram illustrating a method of measuring a position of a measurement point by a measurement head.

FIG. 6 is a flowchart showing a processing order of a second step.

[Explanation of symbols]

 10: Measuring head 12: CCD camera 13: Slit light source 14: Marker 21: Stereo camera 22: Stereo camera

Continuation of the front page (72) Inventor Hiroshi Kamosono 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term (reference) 2F065 AA04 AA53 BB29 DD03 DD04 FF05 GG06 GG16 HH05 JJ03 JJ26 LL22 PP04 QQ04 QQ21 QQ32 QQ34 5B047 AA07 BA02 BB06 5B057 AA20 BA02 BA19 BA23 CA20 CD01 DA07 DB02

Claims (3)

[Claims] 1. A measuring head having at least four markers and freely moved by a measurer, and using the measuring head, a coordinate of a measuring point on an object to be measured in a coordinate system of a center of the measuring head is determined. Measuring point coordinate calculating means,
Measuring head imaging means for imaging the measuring head from a predetermined position; measuring head position calculating means for obtaining information on the position of the measuring head in a world coordinate system using the measuring head imaging means; and measuring head position calculating means Based on the information on the position of the measuring head obtained by the above, the coordinates of the measuring point on the object to be measured in the coordinate system of the measuring head center obtained by the measuring point coordinate calculating means are converted into the coordinates of the world coordinate system. A shape measuring device comprising: a coordinate conversion unit configured to perform conversion; wherein the measurement head position calculation unit identifies a marker corresponding to each marker image based on an arrangement of the marker image captured by the measurement head imaging unit. Marker identifying means for performing tracking, marker tracking means for tracking movement of each marker image picked up by the measuring head imaging means, Means for obtaining information on the position of the measuring head based on the position in the world coordinate system. 2. The measuring head position calculating means, when the movement of all the marker images can be tracked by the marker tracking means, identifies the marker corresponding to each marker image by the marker identifying means, 2. The shape measuring apparatus according to claim 1, wherein when there is a marker image whose movement cannot be tracked by the tracking means, the marker image that has been tracked identifies the corresponding marker based on the identification result of the marker image before movement. . 3. The measuring head position calculating means includes a marker number detecting means for detecting the number of marker images picked up by the measuring head image picking up means. When the number is the same as the number of markers attached to the measurement head, each marker image identifies a corresponding marker by the marker identification means, and the number of marker images detected by the marker number detection means is measured. 2. The shape measuring apparatus according to claim 1, wherein when the number of markers is smaller than the number of markers attached to the head, each marker image identifies a corresponding marker by the marker tracking means.