JPH0252204A - Measuring instrument for three-dimensional coordinate - Google Patents

Abstract

PURPOSE:To improve an accuracy for a measurement and especially to make the accurate measurement for remote objects by changing a magnification of the optical system on an image pickup device and also providing magnification changing means to restart coordinate calculating means. CONSTITUTION:The optical system 9a having a changeable magnification is included in the image pickup device 9. By the coordinate calculating means 10, an image of the object A to be measured is picked-up many times, while changing the focusing position of the image pickup device 9. Then, among many obtained pictures, the pictures focused on each part of the object A to be measured area decided, and three dimensional coordinates for each part of the object A are obtained from the condition of the optical system 9a at the time when the image of each picture are picked-up. By the magnification changing means 11, the coordinate calculating means 10 is restarted along with changing the magnification of the optical system 9a. When the coordinate calculating means 10 is restarted, the focused pictures among the many pictures picked-up by the image pickup device 9 in the condition having a short depth of the object, are decided, thereby the three dimensional coordinates of the object A to be measured are accurately obtained. The three dimensional coordinates with the high accuracy are obtained accordingly even in the case the distance to the object is long.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to improvement of a three-dimensional coordinate measuring device.

(Prior Art) Conventionally, there have been various methods for obtaining a total of 41 three-dimensional coordinates of a measurement object having a three-dimensional extent, one of which is a focusing point position changing method. This method images the object to be measured many times without changing the focal point position of the imaging device, and then determines a focused image for each part of the object from among the many images obtained. The distance from the state of the optical system of the imaging device to each part of the object to be measured, that is, the three-dimensional coordinates of each part, is determined.

In order to determine the above-mentioned focused image, the contrast of the image is usually determined by using an imaging device having an optical system with a predetermined depth of focus to capture an object having a three-dimensional spread. The in-focus areas have the highest contrast, while the out-of-focus areas cause blurring, resulting in contrast. In other words, when the in-focus point position is changed continuously from the front to the back, the contrast at the edges of the image is initially small due to the brushing, increases as the focus comes into focus, and reaches its maximum when the focus is in focus. Become,
Beyond that point, it becomes smaller and smaller due to brushing.

Therefore, the distance corresponding to the in-focus position of the optical system when the image with the largest differential component is obtained can be regarded as the distance to the feature point, and the in-focus position is The distance can be measured by finding the one with the largest edge differential component among a number of different images.

FIG. 2 shows an example of a three-dimensional coordinate measuring device using the above method. A video camera] forms an image of a measurement target (subject) A on an image sensor 3 via a lens 2,
Convert to video signal. The video signal is converted from an analog signal to a digital signal by an analog/digital (A/D) converter 4 and transferred to a processing device 5. The processing device 5 performs differential calculation processing on the digital signal, detects the contrast of the image of the subject A, and further controls the lens controller 6 based on this result to determine the position of the lens 2, that is, the in-focus position of the video camera 1. change. Also,
The image of the subject A after the focal point position has been changed is converted into a video signal by the video camera 1 in the same manner as described above, and is transferred to the processing device 5 via the A/D converter 4 and processed. By repeating this series of processing, the contrast in a large number of images with different focal point positions is detected, and by selecting the image with the highest contrast for each part of the subject A, the contrast between each part of the subject A is detected. Distance is required.

(Problem to be Solved by the Invention) Incidentally, the measurement accuracy in the above-described apparatus depends on the contrast detection accuracy.

When an object point is imaged on a conjugate image plane by an optical system, if the image plane is moved back and forth, the rays passing through the exit pupil of the optical system and converging on the image point become blurred on the image plane. produces an image.

The size of this brush is proportional to the angle of divergence of the beam of light converging toward the image point and the amount of deviation from the correct position of the image plane, and the size of the brush is smaller than the resolution ε of the image sensor. For example, the image is considered to be practically clear, that is, the contrast is large. When the position of the image plane is fixed, the range of the object that produces a clear image on it is called the object (depth of field).

Figure 3 shows the relationship between the image on the image plane and the object depth. In the figure, Q is the image plane, 0 is the object plane conjugate to the image plane Q, E is the optical system, and here the focal length f is This is the central plane of the lens 7, and the distance between the image plane Q and the central plane E is a1, and the distance between the centroid plane E and the object plane O is b.

The object point on the object plane O forms a clear image on the image plane Q via the lens 7. In addition, object points on planes 01 and 02, which are located at distances Δ1 and Δ in front and behind object plane 0, form circular images of a predetermined size on image plane Q via lens 7. If the diameter of this circular image is less than or equal to the resolution ε, it can be considered that a clear image has been formed on the image plane Q.

When the diameter of the circular image on the image plane Q corresponding to the object point on the planes 01 and 02 is equal to the resolution ε, the planes 01 and 0
The distance between Δ-Δ2-Δ1 (1) is called the object depth.

Also, if the lateral magnification of the lens 7 is β and the diameter of the exit pupil by the aperture 8 is D, then IβID)ε, then Δ2−−Δ1
Therefore, the object depth Δ is Δ=Δ2−Δ1−2ε·b/lβID (2).

In this way, since there is a certain range of object surfaces where a clear image can be obtained on the image plane Q, that is, a large contrast can be obtained, it is difficult to measure distance with high precision with the above device. In particular, the distance to the subject, that is, the distance Mb in equation (2)
There was a problem that the larger the value, the larger the object depth Δ, which deteriorated the measurement accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and provide a three-dimensional coordinate measuring device that has high measurement accuracy and is capable of measuring even distant objects with high precision.

(Means for Solving the Problem) FIG. 1 shows an outline of a three-dimensional coordinate measuring device of the present invention, in which 9 is an imaging device having an optical system 9a that can change the magnification, and 10 is an imaging device. The measurement target A is imaged many times while changing the focal point position of 9, and a focused image for each part of the measurement target A is determined from among the many images obtained, and the imaging device at the time of each image capture Coordinate calculation means 9 calculates the three-dimensional coordinates of each part of the measurement object A from the state of the optical system 9a, and 11 a magnification change that changes the magnification of the optical system 9a of the imaging device 9 and restarts the coordinate calculation means 10. It is a means.

FIG. 4 shows an outline of another three-dimensional coordinate meter 4) according to the present invention. 15 corresponds to the imaging devices 12 and 13, respectively, the imaging device 12;
The measurement target A is imaged many times while changing the focal point position of 1B and 1B, and a focused image for each part of the measurement target A is determined from among the many images obtained. First and second coordinate calculating means for calculating the three-dimensional coordinates of the left image and the right image for each part of the object A, 411 in total, from the states of the optical systems 12a and 13a of the devices 12 and 13; search range limiting means for determining the range in which the total Al11 objects A having similar three-dimensional coordinates exist based on the three-dimensional coordinates of the left image and the right image obtained by [coordinate calculation means] 4 and 15; is a third coordinate calculation means that searches for a corresponding point within the range in the left image and right image captured by the imaging devices 12 and 13, and calculates its three-dimensional coordinates.

Further, FIG. 5 shows still another three-dimensional coordinate meter 411 of the present invention.
This shows an outline of the device. In the figure, 14 and 15 are first and second coordinate calculation means similar to the device in FIG. 4, and Koro is a search range limiting device similar to the device in FIG. 4.]7 Reference numerals 18 and 19 denote a pair of left and right image pickup devices having optical systems 18a and 1.9a, respectively, which can change the magnification; 20 and 2] denote a first and Second
The magnifications of the optical systems 18a and 19a of the imaging devices 18 and 19 are changed corresponding to the coordinate calculation means 14 and 15 of
These are first and second magnification changing means for restarting the computer.

(Function) According to the apparatus shown in FIG. 1, the magnification changing means 1 changes the magnification of the optical system 9a of the imaging device 9. For example, when it increases, the object depth of the optical system 9a of the imaging device 9 also changes.
In other words, it becomes smaller.

FIG. 6 shows the relationship between the lateral magnification of the optical system and the object depth. In the optical system, for example, lenses 22 and 23, if lens 22 has a larger lateral magnification than lens 23, that is, it has a longer focal length. The object depth Δ01 of the lens 22 is smaller than the object depth Δ02 of the lens 23.

Therefore, in the apparatus, when the coordinate calculating means 10 is further restarted by the magnification changing means 11, a focused image is determined from among the many images taken by the imaging device 9 in a state where the object depth is small. , from which the three-dimensional coordinates of the measurement object A can be determined with high precision.

According to the apparatus shown in FIG. 4, the measurement target A is selected from a large number of left and right images taken by the first and second coordinate calculation means 14 and 15 while changing the focal point positions of the imaging devices 12 and 13. A focused left image and right image are determined for each part of the image capturing device 12 and 1 at the time of capturing each image.
The three-dimensional coordinates of the left image and the right image for each part of the measurement object A are determined from the states of the optical systems 1, 2a and 13a of No. 3. Further, from the three-dimensional coordinates of these left and right images, the search range limiting means 16 determines the range in which the measurement object A having similar three-dimensional coordinates exists, and the third coordinate calculating means 17 determines the range in which the measurement object A exists. 12 and 1
The range in the left image and right image captured by 3, that is, a total of 4 by the first and second coordinate calculation means 14 and 15.
11. From the results, a corresponding point is searched within the expected range, and its three-dimensional coordinates are determined.

Further, according to the apparatus shown in FIG. 5, the object depth is changed by the first and second magnification changing means 20 and 21 corresponding to the first and second coordinate calculating means 14 and 15, for example, when the object depth is small. The three-dimensional coordinates of the left image and the right image for each part of the measurement target A are determined based on a large number of left and right images captured by the imaging devices 18 and] 9, and from these, similar three-dimensional coordinates are determined in the same manner as described above. The range in which the measurement target A exists is determined, and further the range in the left image and right image captured by the imaging devices 18 and 19,
That is, a search is made for a corresponding point within a range where the existence of the corresponding point is predicted with a higher probability, and its three-dimensional coordinates are determined.

(Embodiment) FIG. 7 shows a first embodiment of the three-dimensional coordinate measuring device of the present invention, and here, an example corresponding to the device shown in FIG. 1 described above is shown. In the figure, 31 is a video camera, 32 is a camera mount, 133 is an A/D converter, 34 is a camera controller, 35 is a lens controller, and 36 is a processing device.

The video camera 31 includes an optical system that can change magnification, here a zoom lens 31a, and forms an image of the measurement object (subject) A on an image sensor (not shown) through the zoom lens 31a. Convert to video signal. The camera mount 32 supports the video camera 31 so as to be swingable in any horizontal or vertical direction.

The camera controller 34 drives the camera mount 32 based on a control command from the processing device 36, and changes the imaging direction of the video camera 31.

The lens controller 35 controls the zoom lens 31a of the video camera 31 based on control commands from the processing device 36.
to change its magnification and focal point position.

The processing device 36 is composed of a well-known computer or the like, and controls the camera controller 34 and the lens controller 35 according to a predetermined program, and receives the video signal of the subject A converted into a digital signal via the A/D converter 33. Then, predetermined arithmetic processing is performed to calculate the three-dimensional coordinates of the subject A.

FIG. 8 is a flowchart corresponding to the program of the processing device 36, and the program and the processing device 36 realize the coordinate calculating means 10 and the magnification changing means 11 in FIG.

Next, the operation will be explained.

First, the processing device 36 operates the camera mount 32 and the zoom lens 31a via the camera controller 34 and the lens controller 35, and sets the magnification and focus position of the zoom lens 31a to a predetermined initial state (for example, the magnification is 1).
Step s
i), input an image (step s2). At this time, if the subject A is not photographed (step s3), the camera mount 32 is operated via the camera controller 34,
The field of view of the video camera 31 is moved in a predetermined scanning direction (
Step s4): Input the image again.

Next, the processing device 36 receives input from the video camera 31
The video signal converted into a digital signal by the /D converter 33 is subjected to differential calculation processing similar to that in the conventional example, and the contrast (image blur) of the image of the subject A is detected (step s5). Further, the processing device 36 repeats step 5687), image input (step s8), and image blur detection (step s5) to change the focal point position of the zoom lens 3 and a based on the detection results, and obtains the maximum contrast value. The resulting in-focus position is determined (step s9).

Thereafter, the processing device 36 moves the imaging field of view of the video camera 31, and the processing device 36 moves the imaging field of view of the video camera 31 to
Repeat the process of step S9 (step s1.O5ll)
).

Next, the processing device 36 changes the focal length, that is, the magnification of the video camera 31, and repeats the processes from step 52 to step sll described above for all the magnifications (step s1).
．． 2. s13) Based on these results, calculate the distance to each part of object A, that is, the three-dimensional coordinates (
Step 514).

According to this embodiment, an image of the subject A can be obtained using the zoom lens 31a with the magnification changed, that is, with the object depth changed, and the in-focus position of the video camera 31 with the small object depth is determined for each part of the subject A. Since the distances to each part of the subject A are calculated from these, highly accurate three-dimensional coordinates can be obtained.

Further, in this embodiment, the magnification is changed after scanning the entire field of view, or the magnification may be sequentially changed for a certain range of field of view, and then the field of view may be changed. Note that the full field of view is the movable range of the camera mount 32 or the angle of view of the video camera 31 when the magnification is at its lowest.

FIG. 9 shows a second embodiment of the three-dimensional coordinate measuring device of the present invention, and here an example corresponding to the device shown in FIG. 4 described above is shown. In the figure, 37 and 38 are video cameras, 39 and 40 are camera mounts, 41 and 42 are A/D converters, 43 and 44 are camera controllers, 45 and 46 are lens controllers, and 47 is a processing device.

The video cameras 37 and 38 are equipped with standard lenses 37a and 38a, respectively, and are arranged at a predetermined interval, and capture left and right images of the subject A through the standard lenses 37a and 38a. An image is formed on an element (not shown) and converted into a video signal.

Camera mounts 39 and 40 are for video cameras 37 and 3.
8 is supported so as to be swingable in any direction horizontally or vertically.

Camera controllers 43 and 44 drive camera mounts 39 and 40 based on control commands from processing device 47, and change the imaging directions of video cameras 37 and 38. Lens controllers 45 and 46 control video cameras 37 and 38 based on control commands from processing device 47.
The standard lenses 37a and 38a are driven to change their focal point positions.

The processing device 47 consists of a well-known computer or the like, and processes the camera controllers 43 and 44 according to a predetermined program.
It also controls the lens controllers 45 and 46, receives video signals corresponding to the left and right images of the subject A converted into digital signals via the A/D converters 41 and 42, and performs predetermined arithmetic processing. Do subject A
Calculate the three-dimensional coordinates of

10(a) and 10(b) are flowcharts corresponding to the program of the processing device 47, in which the program and the processing device 47 cause the first and second coordinate calculating means 14 and 1 in FIG.
5. Search range limiting means 16 and third coordinate calculating means]
7 is realized.

Next, the operation will be explained.

First, the processing device 47 detects the distance to each part of the left image and right image of the subject A, that is, the three-dimensional coordinates, based on the focusing point position change method using the video cameras 37 and 38, respectively (step sp 1..

5p2).

The operations in steps sp1 and sp2 are performed in the tenth step sp1 and sp2.
This is the same as the first embodiment except that the magnification of the video camera is not changed as shown in Figure (b).
The explanation will be omitted.

Next, the processing device 47 divides the left image and right image of the subject A into a plurality of ranges having similar distances based on the distance values to each part of the left image and right image of the subject A described above (step 5p3).

Further, the processing device 47 searches for corresponding points based on the well-known binocular stereoscopic viewing method for each of the ranges (search ranges) in the left and right images of the subject A inputted via the video cameras 37 and 38. (Step s p4)
, based on this, the distance to each part of subject A, that is, 3
Calculate dimensional coordinates (step s p5) 0 According to the present embodiment, prior to detecting three-dimensional coordinates by binocular stereoscopic viewing, three-dimensional coordinates are calculated by a focal point position change method using two video cameras 37 and 38. Since the range having similar 3D coordinates, that is, the range in which corresponding points are expected to exist, was determined from the 3D coordinates of the left image and the right image, the range of the search for corresponding points can be narrowed, and the calculations associated with the search for corresponding points can be narrowed. Not only can the amount be reduced, but also the accuracy can be improved, and more accurate three-dimensional coordinates can be obtained.

FIG. 11 shows a third embodiment of the three-dimensional coordinate measuring device of the present invention, and here an example corresponding to the device shown in FIG. 5 described above is shown. In the figure, 39 and 40 are camera mounts, 4
1 and 42 are A/D converters, 43 and 44 are camera controllers, 48 and 49 are video cameras, 50 and 51
52 is a lens controller, and 52 is a processing device.

Video cameras 48 and 49 each have a zoom lens 48
a and 49a and are arranged at a predetermined interval, and the object A is photographed through the zoom lenses 48a and 49a.
The left and right images are formed on an image sensor (not shown) and converted into video signals.

Lens controllers 50 and 51 drive zoom lenses 48a and 49a of video cameras 48 and 49 based on control commands from processing device 52, and change their magnification and focal point position.

The processing device 52 is composed of a well-known computer or the like, and processes the camera controllers 43 and 44 according to a predetermined program.
It also controls the lens controllers 50 and 51, receives video signals corresponding to the left and right images of the subject A converted into digital signals via the A/D converters 4 and 42, and performs predetermined arithmetic processing. Subject A
Calculate the three-dimensional coordinates of Note that the other configurations are the same as in the second embodiment.

12(a) and 12(b) are flowcharts corresponding to the program of the processing device 52, in which the program and the processing device 52 are used to calculate the first and second coordinates calculating means 14 and 15 and the search range limiting means 16 in FIG. , third coordinate calculation means 17
In addition, first and second magnification changing means 20 and 21 are realized.

Next, the operation will be explained.

First, the processing device 52 detects the distance to each part of the left image and right image of the subject A, that is, the three-dimensional coordinates, based on a focusing point position change method that involves changing the magnification using the video cameras 48 and 4, respectively. (Step spa, 5p7).

The operations in steps Sp6 and sp7 are performed in the twelfth step.
As shown in Figure (1), it is the same as the first embodiment, so its explanation will be omitted.

Hereinafter, as in the case of the second embodiment, the processing device 52 converts the left image and right image of the subject A from the distance values to each part of the left image and right image of the subject A to have similar distances. In Step 5p3), each of the ranges (search ranges) in the left and right images of subject A inputted via the video cameras 48 and 49 is divided into a plurality of ranges, and correspondence is determined based on the well-known binocular stereoscopic viewing method. A point search is performed (step 5p4), and based on this, the distance to each part of the subject A, that is, the three-dimensional coordinates are calculated (step 5p5).

According to this embodiment, the range of corresponding point search required prior to detection of three-dimensional coordinates by binocular stereoscopic viewing is
Since the calculation is performed more precisely based on the image input from 9, the amount of calculation involved in searching for corresponding points can be further reduced compared to the second embodiment, and the accuracy can be further improved. It is possible to obtain more accurate three-dimensional coordinates.

In the embodiment, a zoom lens whose focal length can be changed continuously is used as an optical system whose magnification can be changed, but a lens whose focal length can be changed stepwise may also be used.

(Effects of the Invention) As explained above, according to the present invention, by changing the magnification of the optical system of the imaging device, a focused image of a subject with a reduced object depth can be obtained. Since three-dimensional coordinates are calculated, three-dimensional coordinates with few errors can be obtained, and particularly when the distance to the subject is long, highly accurate three-dimensional coordinates can be obtained.

Further, according to the present invention, focused images are obtained from a pair of left and right imaging devices, three-dimensional coordinates of the left image and right image of the subject are calculated from the focused images, and three-dimensional coordinates of the left image and right image of the subject are calculated based on these. The range in which similar 3D coordinates can be obtained is limited, and the 3D coordinates are calculated by searching for corresponding points within this range using the well-known binocular stereoscopic method. It is possible to reduce the amount of calculation required to obtain , and to obtain corresponding points with high precision, thereby obtaining highly accurate three-dimensional coordinates.

Furthermore, according to the present invention, focused images are obtained from a pair of left and right imaging devices with respective object depths reduced, and three-dimensional coordinates of the left and right images of the subject are calculated from these images. The three-dimensional coordinates are calculated by limiting the range in which similar three-dimensional coordinates can be obtained in the left and right images of the subject, and searching for corresponding points within the range using the well-known binocular stereoscopic method. Therefore, the amount of calculation required to find corresponding points from the left and right images can be significantly reduced, and the corresponding points can be found with extremely high accuracy, so that three-dimensional coordinates with even higher precision can be obtained.

In addition, any of the devices of the present invention can perform measurements using natural light, and can measure the three-dimensional coordinates of objects, scenery, etc. in natural light, and can generate three-dimensional information for image databases and CAD with high precision. Furthermore, it has the advantage that it can be applied to terrain analysis using aerial photographs, automatic driving of automobiles, visual control of robots, etc.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing an overview of the three-dimensional coordinate measuring device of the present invention, Fig. 2 is a configuration diagram showing an example of a conventional three-dimensional coordinate measuring device, and Fig. 3 shows the image on the image plane and the object depth. 4 is a functional block diagram showing an overview of another three-dimensional coordinate measuring device of the present invention, and FIG. 5 is a functional block diagram showing an overview of still another three-dimensional coordinate measuring device of the present invention. FIG. 6 is an explanatory diagram showing the relationship between the lateral magnification of the optical system and the object depth, FIG. 7 is a block diagram showing the first embodiment of the three-dimensional coordinate measuring device of the present invention, and FIG. 8 is a block diagram. FIG. 7 is a flowchart corresponding to the program of the processing device, FIG. 9 is a configuration diagram showing a second embodiment of the three-dimensional coordinate measuring device of the present invention, and FIG. 10(a)
(b) is a flowchart corresponding to the program of the processing device in FIG. 9, FIG. 11 is a configuration diagram showing a third embodiment of the three-dimensional coordinate measuring device of the present invention, and FIGS. 12(a) and (b) are 11th
3 is a flowchart corresponding to a program of the processing device shown in FIG. 9.12.13, 18.19...imaging device, 9a],
2a, 13a, 18a, 19a...optical system, 10...
- Coordinate calculation means, 11...Magnification changing means, 14...
First coordinate calculation means, 15/Second coordinate calculation means, 16
. . . Search range limiting means,] 7. Third coordinate calculation means, 20. First magnification changing means, 21. Second magnification changing means. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (3)

[Claims] (1) Using an imaging device and imaging the object to be measured many times while changing the focal point position of the imaging device, and determining a focused image for each part of the object to be measured from among the many images obtained; A three-dimensional coordinate measuring device comprising: a coordinate calculating means for calculating three-dimensional coordinates of each part of a measurement target from the state of the optical system of the imaging device at the time of each image capturing; A three-dimensional coordinate measuring device, characterized in that it includes a magnification changing means for changing the magnification of an optical system of an imaging device and restarting a coordinate calculating means. (2) A pair of left and right image pickup devices arranged at a predetermined interval, and a pair of left and right image pickup devices, each of which images the object to be measured many times while changing the focused position of the image pickup device. A focused image for each part of the measurement target is determined from a large number of images, and the three-dimensional coordinates of the left image and right image for each part of the measurement target are determined from the state of the optical system of the imaging device at the time of capturing each image. The first and second coordinate calculation means calculate a search range limiting means for determining an existing range; and a third coordinate calculation for searching for a corresponding point within the range in the left image and right image captured by a pair of left and right imaging devices, and determining its three-dimensional coordinates. A three-dimensional coordinate measuring device characterized by comprising: means. (3) Using a pair of left and right imaging devices each having an optical system that can change the magnification, the magnification of the optical system of the imaging device is changed and the coordinate calculation means corresponds to the first and second coordinate calculation means, respectively. 3. The three-dimensional coordinate measuring device according to claim 2, further comprising first and second magnification changing means for restarting the three-dimensional coordinate measuring device.