JPH1163952A - Three-dimensional shape measurement target and collimation plane tilt measurement method - Google Patents

Abstract

(57) [Summary] [Problem] A target used for three-dimensional measurement of a structure, which has a high measurement accuracy of a direction and an inclination angle of a collimation plane, and a method of measuring measurement point coordinates using the target with high accuracy. I will provide a. SOLUTION: A collimating mark graphic 1 is marked on a collimating plane 2 of a target, and a tilt angle measuring mark graphic 3 is marked on another collimating plane 4 which is parallel to the collimating plane 2 and has a different height h. A three-dimensional shape measurement target, characterized in that: The image of the collimation mark figure 1 and the inclination angle measurement mark figure 3 of the target is subjected to image analysis by the image processing device 12, whereby
The centroid P of the collimation mark graphic and the centroid Q of the inclination angle measurement mark graphic are determined, and the difference between the coordinate values of the centroids of the two mark graphics on the image coordinate plane and the known values of the collimation plane and the inclination measurement plane are determined. A method for measuring the inclination of the collimation plane, which simultaneously determines the direction of the inclination of the collimation plane of the target and the absolute amount of the inclination from the height difference h.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an automobile, an aircraft,
Target for industrial measurement of workpieces such as antennas, and three-dimensional shape measurement used in three-dimensional shape measurement and analysis systems for measuring three-dimensional shapes of civil engineering, building structures, and large structures such as ships and analyzing the measured values It is about.

[0002]

2. Description of the Related Art Automobiles, aircraft, antennas and bridges,
Obtaining accurate measurement data of three-dimensional shapes of building steel frames, ships, and other members constituting large steel structures is important in terms of assuring shape and dimension performance and assuring assembly and installation work. In conventional three-dimensional shape measurement, a human looks into a lens, finds a measurement point on a measurement target, collimates the measurement point, and performs triangulation by a forward intersection method or distance measurement using a light wave distance meter. The three-dimensional coordinate value of the measurement target measurement point has been obtained by the angle measurement method.

However, in these measurement methods, since the collimating operation is performed by human vision, the operation is complicated, time-consuming, inefficient, and causes a reduction in measurement accuracy.

In order to solve such a drawback, it is conceivable to automate the collimation work. In some cases, an automatic collimation system using a lightwave distance measuring instrument equipped with a reflective target and a CCD camera is considered. Measurement systems have also been developed.

In these conventional three-dimensional shape measuring systems, when measuring points on a measurement object cannot be directly collimated by a measuring instrument installed at a certain position, the measuring points are deviated from the measuring points. It is necessary to set a target.

In this case, the three-dimensional coordinate value of the measurement point, that is, the actual shape of the object to be measured cannot be accurately obtained only by collimating one target and obtaining the three-dimensional coordinate value of the center of the target. Conventionally, in order to solve this problem, for example, two targets are arranged so that the measuring point is located on the extension line connecting the centers of the targets that can be collimated from the measuring instrument, and the center of each target is measured. do it,
A method of determining the position of a measurement point has been adopted. However, in this method, it is necessary to collimate two targets with respect to one measurement point, and it takes time for collimation and image processing, and the work of attaching the target to the measurement point is complicated and inefficient. There was a problem.

The present inventors have solved this problem by collimating only one target which is set to be deviated from the measurement point, and performing image analysis of a mark figure written on the collimation plane.
A method of obtaining the three-dimensional coordinate value of a measurement point from the three-dimensional coordinate value of the collimated point of the displaced target is disclosed in Japanese Patent Application No. 06-27254.
No. 1 and Japanese Patent Application No. 07-058690. In these methods, in order to collimate one target and determine the three-dimensional coordinate value of the measurement point from the three-dimensional coordinate value of the collimation point, it is necessary to determine the inclination of the collimation plane on which the mark is arranged. Therefore, for example, in Japanese Patent Application No. 06-272541, if the collimation plane of a target on which a perfect circle mark is arranged is inclined, the inclination of the collimation plane is determined by using the fact that the imaged mark looks elliptical. Seeking.

Further, Japanese Patent Application No. 09-018973 discloses a method of measuring the inclination of the collimation plane by measuring and measuring three points on the collimation plane of the target.

In these measurement methods, a reflection target of a type in which a collimation mark figure is arranged on a collimation plane composed of a microprism is used.

[0010]

Problems to be Solved by the Invention Japanese Patent Application No. Hei 07-2
According to No. 58538, the center of an image can be obtained with considerably high accuracy by analyzing a circle or ellipse image which has been imaged and processed. However, the method of obtaining the inclination of the collimation plane from an elliptic image obtained by imaging a perfect circle on the collimation plane is based on image processing by an image processing device and a computer as long as the number of pixels of the CCD camera is finite. However, there is a limit in accurately detecting the inclination of the collimation plane from the ellipse image of the mark figure described in (1).

For example, a mark of a perfect circle having a diameter of 50 mm arranged on a collimation plane of a target 15 m away from the collimator with a collimation plane of the target substantially orthogonal to the collimation direction of the measuring instrument is magnified by 30 times. When an ellipse image obtained by imaging through a telescope is analyzed by an image processing apparatus having an effective pixel number of 500 × 500, the minor axis of the elliptical image is 1 in comparison with the major axis.
If a pixel error is included, the inclination of the collimation plane will be an error of about 8 °. As described above, when the target is slightly inclined with respect to the collimating direction of the measuring instrument, it is difficult to accurately determine the inclination of the collimating plane of the target from the ratio of the major axis and minor axis of the ellipse. In particular, when the inclination is small, there is a problem that accuracy is deteriorated.

In the method disclosed in Japanese Patent Application No. 09-018973, the distance of three points on the target surface is measured and measured to determine the inclination of the collimation plane. Horns and one
There is a problem that it is necessary to perform the image processing twice, and it takes a long time to measure one measurement point. Furthermore, in image processing of a general image including a target image captured by an imaging device, it has been sometimes difficult to clearly identify a plurality of mark figures in a target area from the background and accurately detect them.

The present invention has been made on the basis of the above circumstances, and includes a target used to analyze a mark image picked up by a measuring instrument and accurately determine the inclination of a reference plane of the target. It is an object of the present invention to provide a method for accurately and quickly obtaining the direction and the inclination angle of the collimation plane using this target.

[0014]

The present invention has the following features as means for solving the above-mentioned problems. (1) That is, the present invention uses a measuring device 11 equipped with an imaging device, an image processing device 12 that performs image processing of an imaged target, and a measuring device configured by an analysis computer 13 to measure an object to be measured. In the three-dimensional shape measurement target used for three-dimensional shape measurement in which the three-dimensional shape measurement target 10 provided at the measurement point 20 is collimated to measure the three-dimensional coordinate value of each measurement point, a collimation mark figure 1 is marked on the collimation plane 2 of the target, and the inclination angle measurement mark figure 3 is marked on another collimation plane 4 which is parallel to the collimation plane 2 and has a different height h.

The above-mentioned three-dimensional shape measuring target uses a reflection type as a collimating surface, and a collimating surface 2 on which a collimating mark graphic 1 is written and a collimating surface 4 on which a tilt angle measuring mark graphic 3 is written. Are held in parallel by a spacing member 5a having a shape that cannot be seen from the collimation direction within the measurement inclination range 2β, and a frame 6 indicating a target area is marked on the outer periphery of the target, and the collimation plane 2 is visually observed. The automatic collimation can be performed by writing the base line 7 on the applicable mark figure 1.

(2) In performing three-dimensional shape measurement using the target of the present invention, as a method of measuring the direction of inclination and the inclination angle of the collimation plane, a collimation mark figure 1 and an inclination angle measurement mark figure 3 are used. Are analyzed by the image processing device 12 to obtain the centroid P of the collimation mark graphic and the centroid Q of the inclination measurement mark graphic, respectively, and the coordinates of the centroids of the two mark graphics on the image coordinate plane. From the value difference and the known height difference h between the collimation plane and the inclination measurement plane, the direction of the collimation plane of the target and the absolute amount of the inclination are simultaneously determined.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, two collimating surfaces are provided on one target, a collimating mark graphic 1 is marked on one collimating surface 2, and a tilt angle measuring mark graphic 3 is collimated. With the configuration described on the other collimating plane 4 that is parallel to the plane 2 and has a different height, the centroids of the two figures are obtained by image analysis from the images of the respective mark figures captured by the imaging device,
The direction and magnitude of the inclination are determined from the difference between the coordinate values of each centroid and the known height difference h between the two collimation planes.

Using the difference between the coordinate values of the centroids obtained by this method and the direction and magnitude of the inclination of the collimation plane, a target provided at a position deviated from the measurement point to be measured is used. The three-dimensional shift amount between the center point and the measurement point is calculated, and furthermore, the measurement is performed based on the direction of the measurement point and the offset amount of the target obtained by image analysis from the mark figure of the captured target image. The three-dimensional coordinate value of the point is determined. It is to be noted that a specific calculation formula of the coordinate transformation is omitted here, but if it is necessary to know in detail, Japanese Patent Application No. Hei 06-27706
Reference is made to this since it is disclosed in US Pat.

When a reflective type target such as a microprism is used as the target of the present invention, the collimated measuring surface reflects natural light or artificial illumination light, shines brightly, and emerges from the background, so that the target area is clearly identified. be able to. However, in this case, when the trunk 5 connecting the collimation plane 2 on which the collimation mark graphic 1 is described and the collimation plane 4 on which the inclination measurement mark graphic 3 is described enters the field of view, the trunk 5 becomes 5A, when the image shown in FIG. 5A is subjected to the binarized image processing, the torso 5 may be erroneously recognized as a mark figure as shown in FIG. 5B. Therefore, as a countermeasure, the trunk portion 5 connecting the collimating surface 2 and the collimating surface 4 is not visible from the collimating direction within 2β within the measurement inclination range, for example, by using a taper material or a spacing member for a small diameter rod. , As shown in FIGS. 6A and 6B.

FIG. 6 (c) is an image obtained by binarizing the image obtained by photographing the target shown in FIGS. 6 (a) and 6 (b). Only the running mark figure 3 is captured as an image.

Further, as shown in FIG. 7, a frame 6 indicating a target area is marked on the outer periphery of the target, and a base line 7 is marked on the collimation mark graphic 1 on the collimation plane 2 to enable automatic collimation.

The frame 6 is provided for automatically recognizing the target from the shape of the frame captured by the automatically scanning CCD camera, and the base line 7 is provided for recognizing the direction of the measuring point. is there. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0023]

FIG. 1 is a diagram showing an entire configuration of an automatic three-dimensional coordinate measuring and analyzing system for a large structure to which a target for measuring a three-dimensional shape according to the present invention is applied. The provided measurement target 10, a measurement device 11 equipped with a CCD camera, an image processing device 12 for analyzing an image obtained from the CCD camera unit of the measurement device, and analysis and measurement of control of the measurement device, coordinate transformation, etc. It is composed of a device such as a computer 13 with a monitor on which a program for storing results is operated.

On the collimating surface of the target 10, a collimating mark graphic 1 with a high contrast with the collimating surface 2 is arranged. On the inclination measuring surface 4, a tilt measuring surface 4 with a high contrast with the inclination measuring surface 4 are arranged. ing. The mark figures 1 and 3 are imaged by a CCD camera as an image pickup device and used as image signals.
An image pickup device having an appropriate size according to the number of effective pixels and the viewing angle is used. In a part of the collimation plane of the target 10, in a measurement system using an optical distance meter, for example,
It is necessary to use a reflection sheet using a microprism as the material of the collimating surface 2.

Further, if the whole or a part of the target is colored according to the purpose, it is convenient for detecting and identifying the target using a color CCD camera.

The target of the present invention is provided with a collimating surface 2 and a tilt measuring surface 4 having different heights, a collimating mark figure 1 on the collimating surface 2 and a tilt angle measuring surface 4 on the tilt measuring surface 4. It is necessary to mark 3.

FIG. 2A shows a target 10 according to the present invention.
FIG. 2 is a front view of one embodiment, and FIG. 2B is a side view thereof. In this target, a perfect circle collimation mark figure 1 having a high contrast with respect to the collimation plane 2 such as black or brown is written in the center of the collimation plane 2 of a target on a bright ground such as white or yellow. A similar inclination measurement surface 4 of the ground is provided on a plane parallel to the rear of the collimation plane at an interval h, and a concentric circle larger than the collimation mark graphic 1 is described as the inclination angle measurement mark graphic 3.

The size of the target mark figure is measured by a CCD camera having a telescope unit with a magnification of 30 times and analyzed by an image processing unit having about 500 × 500 effective pixels. The collimation distance 1
20mmφ circle if the target is used at 0m,
In addition, if the target (height difference) h between the mark surfaces is 10 mm and the collimating distance is 30 m, a circle of 60 mmφ is appropriate, and the height difference between the mark surfaces is approximately 30 mm.

In this embodiment, since no special target is used, the body 5 of the spacing member 5a connected in parallel with the inclination measuring surface 4 at an interval h from the collimating surface 2 is connected to the collimating surface 2. Although a cylindrical target having the same size is used, when a reflective target is used, as described in the previous section, the body 5 is determined to be black during the binarization process, and a part of the mark graphic for collimation or tilt angle measurement is used. Torso 5
It is desirable that the collimation plane 2 on which the collimation mark graphic 1 is written and the collimation plane 4 on which the inclination angle measurement mark graphic 3 is written are moved from the collimation direction within the measurement inclination range 2β. It is held in parallel by a spacing member 5a having a shape that cannot be seen.

When a CCD camera is automatically scanned to automatically collimate a target, the target image is clearly distinguished from the background from a general image including the target captured by the CCD camera unit, and is raised. For example, a sheet-type reflective target in which a mark figure is marked on a material of a microprism is used, and a mark image for collimation or a mark for collimation angle measurement is marked on the collimation surface 2 and the inclination angle measurement surface 4. In order to clearly identify the target image from the background image, a frame 6 having a high contrast is described on the outer periphery of the target, and a collimation mark graphic 1 shown in FIG.

Next, a method for measuring the inclination angle of the target with respect to the collimation axis using the target of the present invention will be described with reference to FIGS. FIG. 3 shows a target image when the target 10 is tilted with respect to the collimating axis of the camera.
It is a mark figure for collimation and inclination angle measurement which has been binarized by the image processing apparatus. When the target has an angle with respect to the collimation axis, the center (xd, yd) of the inclination measurement mark graphic 3 with the center (xs, ys) P of the collimation mark graphic 1 in the image plane coordinate system ox, y as the origin. yd) Since the direction of the line segment connecting Q indicates the direction of the maximum inclination of the collimation plane of the target, the relationship between the y axis and the angle α formed by the maximum inclination direction of the collimation plane is expressed by Equation (1). It is represented by

Sin α = (xd−xs) / (yd−ys) (1) Further, a value obtained by dividing a distance between PQs on the image coordinate plane by a height difference h between two mark planes is a collimation plane. , That is, the angle θ between the collimation axis 8 and the collimation plane is given by Expression (2).

Θ = ± arctan {[(xd−xs) ² + (yd−yf) ² ] / h} (2) In the above equation (2), a view as shown in FIG. If the inclination θ of the collimation plane 2 with respect to the quasi-axis 8 is defined, the coordinate axis S is set in the direction of the line segment PQ with the center P of the collimation mark figure as the origin.
Is set as shown in FIG. 3, as shown in FIG. 4 (b), which side of the center Q of the inclination measurement mark graphic is positive or negative with respect to the center P of the collimation mark graphic 1? , The sign of the inclination θ of the collimation plane can be determined.

When the inclination θ of the collimating plane is measured and analyzed using the target of the present invention, if the accuracy of the center position of the ellipse obtained by the image analysis is δs, the precision Δθ of the inclination of the collimating plane corresponding to this is Δθ. Is represented by equation (3).

Δθ = 2δs / h (3) For example, a perfect circle mark having a diameter of 60 mm 30 m ahead is imaged through a telescope with a magnification of 30 times and the number of effective pixels is 500 × 5.
When the analysis is performed by the image processing unit 00, the ellipse has a major axis of about 50 pixels, and the standard deviation of the center position accuracy is about 0.2 pixels.
Considering that the standard deviation of the center position accuracy is 0.
2 mm. Therefore, the height difference between the two mark planes is 30
If mm, the standard deviation of the inclination accuracy is 0.3 / 100, which is 0.8 ° when converted into an angle, which is an order of magnitude improvement over the conventional method.

[0036]

According to the target of the present invention and the method for measuring the inclination of the collimating plane using the same, even if the target is set at a position deviated from the measuring point on the measuring object, it can be stably and quickly operated. The inclination of the collimation plane with respect to the collimation axis can be measured with high accuracy. As a result, the three-dimensional shape measurement by the measurement system equipped with the imaging device can be performed with high accuracy by calculation from the inclination of the collimation plane.

When the target is automatically collimated, the target area can be clearly identified from the background, and the mark figure for collimation and inclination measurement in the target area can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the overall configuration of a large structure meter measurement system using a target according to the present invention.

FIG. 2A is a front view showing a target 10 in which a perfect circle collimating mark graphic 1 is arranged on a collimating plane and a concentric inclination measuring mark graphic 3 is arranged on an inclination measuring plane according to an embodiment of the present invention. FIG. 2B is a side view of the same.

FIG. 3 is a plan view showing collimation and inclination measurement mark graphics and images of 3 when the target 10 of FIG. 2 is inclined with respect to a collimation axis.

FIG. 4A shows a case where the target 10 in FIG.
1B is a plan view of the target 10 when it has an angle θ with respect to the collimation axis 8 of FIG. 1, and (b) of the collimation mark figure 1 on the target 10 viewed along the collimation line 8. It is a front view which shows a shape.

5A is a plan view showing a captured image when the target 10 in FIG. 2 is inclined with respect to the collimation axis, and FIG.
Is a plan view showing a binary image obtained by binarizing the captured image.

FIG. 6 (a) is a trunk 5 between a collimation plane and an inclination measurement plane.
Side view of one embodiment of the present invention with a taper at (b)
Is a side view of another embodiment of the present invention in which the collimating surface and the inclination measuring surface are connected by a small-diameter rod, and (c) is a photographed image of the target shown in (a) and (b). FIG. 3 is a plan view showing a binarized binary image.

FIG. 7 is a perspective view of a target for automatic collimation according to another embodiment of the present invention.

[Explanation of symbols]

1: collimation mark figure 2: collimation plane 3: inclination angle measurement mark figure 4: inclination measurement plane 5: trunk 5a: spacing material 6: frame 7: base line 8: collimation axis of measuring instrument 10: target 11: Measuring machine 12: Image processing device 13: Computer 20: Object to be measured P: Image center of collimation mark graphic 1 Q: Image center of tilt angle measurement mark graphic 3 L: Long axis Ls: Collimation mark graphic image Major axis d: major axis of mark figure image for inclination angle measurement S: minor axis of mark figure image 2β: measurement inclination range

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G06F 17/00 G06F 15/20 D G06T 7/00 15/62 415

Claims (4)

[Claims] 1. A measuring instrument 11 equipped with an imaging device, an image processing device 12 for performing image processing of an imaged target,
Using a measuring device configured by the analysis computer 13,
In the three-dimensional shape measurement target used for three-dimensional shape measurement in which the three-dimensional shape measurement target 10 provided at a measurement point on the measurement target 20 is collimated and three-dimensional coordinate values of each measurement point are measured, The corresponding mark figure 1 is marked on the collimating plane 2 of the target, and the mark figure 3 for measuring the inclination angle is parallel to the collimating plane 2 and has a height h.
A three-dimensional shape measurement target described on another collimation plane 4 having a different shape. 2. A collimating surface 2 on which a collimating mark graphic 1 is marked using a reflection type collimating surface, and a tilt angle measuring mark graphic 3
2. The target for three-dimensional shape measurement according to claim 1, wherein the collimating plane 4 described in the above is held in parallel by a spacing member 5a having a shape that cannot be seen from the collimating direction within the measurement inclination range 2β. . 3. A collimating device according to claim 1, wherein a frame indicating a target area is marked on an outer periphery of the target, and a base line is marked on the collimating mark graphic on the collimating surface to enable automatic collimation. Item 3. The target for three-dimensional shape measurement according to Item 2. 4. The centroid P of the collimation mark graphic and the centroid of the inclination angle measurement mark graphic are obtained by image-analyzing the image of the collimation mark graphic 1 and the inclination angle measurement mark graphic 3 by the image processing device 12. Q is obtained, and from the difference between the coordinate values of the centroids of the two mark figures in the image coordinate plane and the known height difference h between the collimation plane and the inclination measurement plane, the direction of the inclination of the collimation plane of the target and the absolute inclination 4. The method for measuring the inclination of a collimating plane using a target for measuring a three-dimensional shape according to claim 1, wherein the amounts are obtained simultaneously.