JPS63218815A - Position measuring method - Google Patents

Abstract

PURPOSE:To calculate the three-dimensional position of an object with good accuracy, by determining a reference two-dimensional image and the position of the image at the aiming point of the object in a reference two-dimensional image and determining the three-dimensional coordinates of the aiming point on the object from the position of the aiming point and a predetermined distance. CONSTITUTION:An image analyzer 5 reads the image shown on a drawing 20A taken by a TV camera 2 from an image memory 6 and cuts the mask 22A containing the image of the aiming point predetermined on the image. Next, the image of a drawing 20B taken by a camera 3 is read from the memory 6 and a mask 22B having the same size is cut from the image centering around the position where the aiming point is present and the correlation between the mask images cut from the drawings 20A, 20B is calculated. Then, calculation is performed with respect to some positions moved up and down, and left and right centering around a region where the presence of the aiming point is estimated to calculate a position where correlation is largest. Then, two-coordinates positions p1, q1, r1 and p2 q2, r2 are set to the identification position of the objective aiming point. From these values, the coordinates position (x, y, z) of the aiming point is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a position measuring method, and more specifically, to measure the three-dimensional coordinate position of an object placed in a three-dimensional space using a television camera. The present invention relates to a simple distance measurement method using such a simple imaging means.

BACKGROUND ART Conventionally, methods for determining the coordinate position of an object in three-dimensional space using a television camera include (1) projecting a slit image onto the object from a light source to display a slit striped pattern on the object surface; (2) A method of determining the three-dimensional coordinate position of an object by analyzing the line width interval of the striped shadow pattern on the surface of the object's image captured by a television camera; A method of determining the three-dimensional coordinate position of an object using the correlation between images has been known.

Problems to be Solved by the Invention However, in method (1), the object must be photographed in a dark room, and in method (2), it is difficult to identify the same point on the object in three screens. This method has drawbacks such as requiring complicated processing for determination.

Therefore, the present invention solves the above-mentioned drawbacks, and provides a position measuring method that can measure the position under normal lighting, has a simple equipment configuration, and can accurately measure the three-dimensional coordinate position of a target object with a simple processing procedure. Our goal is to provide the following.

Means for Solving the Problems According to the present invention, a reference two-dimensional image is obtained by photographing a target object using an imaging means placed at a reference position, and the object is placed at a reference position a given distance away from the reference position. A reference two-dimensional image is obtained by photographing the target object using an imaging means, and the correlation between the reference two-dimensional image and the reference two-dimensional image is determined, and the correlation between the reference two-dimensional image and the reference two-dimensional image is determined. determine the position of the image of the point of interest on the target object, and determine the point of interest on the target object from the respective positions of the point of interest in the reference two-dimensional image and the reference two-dimensional image and the given distance. Provided is a position measuring method characterized by determining a three-dimensional coordinate position of.

Effect In the method described above, by performing correlation processing on two images taken at two positions close to each other, the standard position and the reference position, the two-dimensional coordinate position of the image of the target object's point of interest in each image is determined. can be identified. On the other hand, since the distance between the lens surface of the optical system of the imaging means and the imaging surface can be known, the distance between the above-mentioned standard position and the reference position as well as the image of the point of interest of the target object in the two images can be known. From the two-dimensional coordinate position, the position of the point of interest of the target object can be found three-dimensionally geometrically.

In this process, the identity of the target object image is determined by performing correlation processing on the image contents of the target object, but since the similarity of the images targeted for correlation calculation is high, the conventional It is easier to process than correlation processing. Furthermore, since the position of the point of interest of the target object is determined three-dimensionally, the three-dimensional position of the object can be determined with high accuracy.

Embodiments Hereinafter, embodiments of the position measuring method according to the present invention will be described with reference to the accompanying drawings. It should be noted that the following examples merely illustrate the present invention. Therefore, the present invention is not limited to these embodiments, and various changes and modifications can be made within the scope of the claims.

FIG. 1 is a block diagram of an apparatus for implementing the position measuring method according to the invention. The illustrated position measuring device has a pair of television cameras 2 and 3 that photograph a target object 1 . The television cameras 2 and 3 have the same focal length f of the lenses of their photographic optical systems, and are installed horizontally apart from each other by a distance d. One of the images taken by the television cameras 2 and 3 is selected by the television camera switching device 4, and the images are sent to the image memory 6 via the image analysis device 5.
is memorized. In this embodiment, the image analysis device 5 digitizes the input video signal and outputs it to the image memory 6, reads the image data from the image memory 6, performs correlation processing to be described later, and performs necessary arithmetic processing. do. On the other hand, the image memory 6 has a capacity to store at least two images.

FIG. 2 is a diagram illustrating the principle of a position measuring method using the apparatus of FIG. 1.

In FIG. 2, 0 is the coordinate origin of the ranging system, which is set at the point where the horizontal optical axis of the television camera 2 intersects the lens surface of the photographing optical system. Assuming a rectangular three-dimensional coordinate system (X, Y, Z) with the coordinate origin 0 as the reference, the optical axis of the television camera 2 is the X axis, and the horizontal axis perpendicular to the X axis at the coordinate origin 0 is the Y axis. , the vertical axis perpendicular to the X axis at the coordinate origin 0 is Z
The axis. Therefore, the optical axis of the television camera 3 is separated from the optical axis of the television camera 2 by a distance d along the Y axis,
It is parallel to the optical axis of the television camera 2, and furthermore, the lens surface of the photographing optical system of the television camera 3 is on the same plane as the lens surface of the photographing optical system of the television camera 2.

Furthermore, since the photographing optical systems of the television camera 2 and the television camera 3 have the same focal length, their image planes are also located on a common plane.

In this coordinate system, the coordinate position of the point of interest P of the target object is defined as (x, y, z), and furthermore, a plane parallel to the lens surface of the photographing optical system and including the point of interest P is defined as the object plane. On the other hand, the image plane of the television camera 2 is located at a focal distance f from the coordinate origin O, and the coordinate position of the image ■1 of point P on the object captured on the image plane is (1) +, q++ r , ). Further, the image plane of the television camera 3 is located at a distance f from the lens surface of the television camera 3 along its forward axis.

Therefore, it is located on the X-axis at a focal distance f away from the Y-Z plane. The coordinate position of (R, I2) of point P on the object captured on the image plane of the television camera 3 is (p2.Q2.
I2).

Note that h is the distance along the X-axis from the television camera to the point of interest on the object.

Next, an embodiment of the method according to the present invention will be described using FIGS. 1 and 2.

First, the television camera 2 photographs the target object l to be measured. This photographed image is sent to the image analysis device 5 through the television camera switching device 4. Image analysis device 5
stores this image for one screen in the image memory 6. Next, the television camera switching device 4 is operated, and the target object 1 is photographed by the television camera 3, which is located a distance d from the television camera 2. This photographed screen is also sent to the image analysis device 5 through the television camera switching device 4, and stored in the image memory 6 for one screen.

At this time, assuming that the focal lengths of the two television cameras are the same and that the optical axes of the two television cameras are parallel, the coordinate values of the point of interest P on the target object and the two television cameras are The following relationship holds true between the coordinate values of the image of point P on the image plane.

By solving the above equation for x, y, and z, the coordinate values (x, y, z) of the ninth point of interest P are as follows.

X”d-1)l/(q2 Q+) y=d I Q+/(q2 Q+) (2)z
=d−r+/(q2 qI) Here, d is a measurable value and is the coordinate value of the object image captured by the television camera (+)+, Ql+ rl ) and (1)2. q2. The value of I2) is a value that can be measured by the image analysis device 5. Therefore, the coordinate value of the point of interest on the target object can be determined from the coordinate value of one point of interest on the object images captured by the two television cameras.

Next, a method for identifying the same point of interest on a target object on two images taken by television cameras 1 and 2 will be described.

FIG. 3 is a diagram illustrating a method for identifying the same point of interest from these two images. FIG. 3(a) is an image taken by the television camera 2, and FIG. camera 3
This is an image taken in . 3(a) and 3(b), images 2OA and 20B of the target object 1 of FIG. 1 are illustrated. Masks 22A and 22B are set for the images 2OA and 20B, respectively, for extracting the point of interest P taken on the target object.

Here, the operation of identifying the point of interest is performed as follows. That is, the image analysis device 5 reads the television camera 2 from the image memory 6.
The image shown in FIG. 3(a) taken in 1 is read out, and a mask 22A of an appropriate size containing an image of a predetermined point of interest P is cut out from the image. Next, the image shown in FIG. 3 et al. taken by the television camera 3 is read out from the image memory 6, and a mask of the same size as the above is placed on the image, centering on the position where the target point of interest P is estimated to exist. 2
Cut out the screen with 2B. The correlation between this mask image cut out from FIG. 3(b) and the mask image cut out previously from FIG. 3(a) is calculated. This correlation calculation is performed for several positions by moving the cutout mask vertically and horizontally around the estimated existence area of point P on Figure 3, etc., and among them, the position with the largest correlation is demand. The two coordinate positions for point P obtained through this operation are the identified position (pl) of the target point of interest.

q+, r+) and (+)2. Q2. r2). That is, the center of the mask 22Δ becomes the identified position (p+, Q++ r+) of the target point of interest, and the center of the mask 22B when the image with the highest correlation with the image in the mask 22A is obtained is the identified position of the target point of interest. This becomes the identified position (p2. q2. r2).

Therefore, by using equation (2) above for these values, the coordinate position (x, y, z) of the point of interest can be obtained.

In the above explanation, the images taken by the two television cameras are stored in the image memory 6, and then the correlation between the image contents at the candidate position of the point of interest is calculated. It is clear that it is also possible to perform correlation determination calculations on the signals themselves.

Further, in the above description, the case where two television cameras 2 and 3 are used as the television camera was explained, but if only one television camera, for example television camera 2, is used, the first
Even if a camera moving device is used instead of the television camera switching device 4 shown in the figure to photograph one image, the television camera is moved in parallel by a specified distance d, and a second image is photographed. It is clear that the same distance measuring operation can be performed.

Next, an embodiment will be described in which the three-dimensional position detection accuracy of the above-described position measuring method is improved. That is, in the method described above, if the distance d between the television cameras that photograph the target object twice is small, the distance detection accuracy may not be sufficient, as can be seen from equation (2). In this case, the shooting position d of the TV camera is set to be large, but if d becomes large, the image content of the object's focus point will appear different in the two images, and there is a risk that the correlation will not be detected accurately. be.

FIG. 4 is a diagram explaining the operation of a highly accurate position measuring method that solves this drawback, with reference numbers 2A, 2B, 2C...
2N indicates each position of the television camera moved by an interval d along the Y axis.

5(a), 5(a), 5(c), and 5(d) are diagrams showing images taken at each television camera position in FIG. 4, with reference numbers 24A, 24B, 24C, . . . 24N. indicates a mask of the point of interest in each image.

The operation of this highly accurate position measuring method is as follows. That is, as shown in FIG. 4, the target object is photographed while continuously moving the television camera along the Y axis. At this time, images with slightly different image contents are obtained from each television camera, as shown in FIG. Here, it is assumed that a mask 24A corresponding to the point of interest of the target object is cut out from the first image, for example, FIG. 5(a). Next, bring this cut-out mask to the estimated position of the corresponding point of interest in the next image (Figure 5(b)) and investigate the correlation (pattern matching).
I do. Here, if the distance d between the television cameras i2A and 2B is sufficiently close, a high correlation is guaranteed. Therefore, the mask 24B at the position of the point of interest where the highest degree of correlation was obtained is cut out from the images in Figure 5, et al., and used as the standard pattern for the correlation investigation for the next photographed image, that is, the image in Figure 5 (C). do. Next, similar processing is performed on the image shown in FIG. 5(C) obtained at the television camera position 2C, and correlation is investigated using this newly cut out reference pattern. In this way, since the image content of the point of interest is similar between consecutive images, it is possible to extract the position of the point of interest while ensuring a high correlation. As a result, it will be possible to determine the identity of a point of interest on an object with high accuracy for images taken by two television cameras separated by nd (n is the number of repetitions), and with high accuracy. Position measurements can be performed.

As described in detail, according to the position measuring method of the present invention, a target object can be photographed by an imaging means such as a television camera under normal lighting conditions. In addition, the two captured images are very similar as can be seen from the capturing method, and when calculating the correlation, it is easy to estimate the existence range of the point of interest, and the amount of calculation can be small. Therefore, three-dimensional distance measurement can be performed with high accuracy. Furthermore, since the equipment configuration including the television camera is simple, it can be put to a wide range of practical applications.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the configuration of a device that implements the position measuring method according to the present invention, FIG. 2 is a diagram illustrating the principle of the position measuring method according to the present invention, and FIG. 3 shows the same points of interest. Figure 4 is a diagram illustrating the identification method; Figure 4 is a diagram illustrating the operation of the high-precision ranging method in the position measurement method according to the present invention; Figure 5 is a diagram illustrating the operation of the high-precision ranging method in the position measurement method according to the present invention; It is a figure showing an image. [Main reference numbers] l...Target object 2.3...Television camera 4...Television camera switching device 5...Image analysis device 6...Image 1 image memory 22A, 22B, 24A, 24B, 24C, 24N...・
·mask

Claims (9)

[Claims] (1) A reference two-dimensional image is obtained by photographing a target object with an imaging means placed at a reference position, and a reference two-dimensional image is obtained by photographing the target object with an imaging means placed at a reference position a given distance from the reference position. Obtain a two-dimensional image, determine the correlation between the standard two-dimensional image and the reference two-dimensional image, and determine the position of the image of the target object in the standard two-dimensional image and the reference two-dimensional image. and determining the three-dimensional coordinate position of the point of interest on the target object from the respective positions of the point of interest in the standard two-dimensional image and the reference two-dimensional image and the given distance. position measurement method. (2) With respect to the optical axis of the imaging means placed at the reference position,
Claim (1) characterized in that the reference two-dimensional image is prepared by photographing the target object using the imaging means with the optical axes of the imaging means placed at the reference position parallel to each other. Position measurement method described in section. (3) The imaging means is placed at the reference position such that the lens surface of the optical system of the imaging means placed at the reference position and the lens surface of the optical system of the imaging means placed at the reference position are located on the same plane. The position measuring method according to claim 1 or 2, characterized in that the reference two-dimensional image is prepared by positioning the target object and photographing the target object by the imaging means. (4) The coordinate position (x, y, z) of the point of interest of the target object in the orthogonal three-dimensional coordinate [X, Y, Z] system is expressed by the formula x=d・p_1/(q_2-q_1) y=d・q_1/(q_2-q_1) z=d・r_1/(q_2-q_1) However, X: The origin is the intersection of the optical axis of the imaging means placed at the reference position and the lens surface of the optical system; Coordinate axis Y along the optical axis of the imaging means placed at the reference position: The coordinate axis Y is perpendicular to the X-axis with the intersection of the optical axis of the imaging means placed at the reference position and the lens surface of the optical system as the origin, and the image taken at the reference position. Coordinate axis Z located within a plane formed by the optical axis of the means and the optical axis of the imaging means placed at the reference position: the intersection of the optical axis of the imaging means placed at the reference position and the lens surface of the optical system Coordinate axis d perpendicular to the X-axis and Y-axis as the origin: distance p_1 on the Y-axis between the optical axis of the imaging means placed at the reference position and the optical axis of the imaging means placed at the reference position p_1: the reference position and coordinate position q_1 on the X-axis of the image plane of the imaging means placed at the reference position: coordinate position r_1 on the Y-axis of the point of interest on the image plane of the imaging means placed at the reference position: The coordinate position q_2 on the Z-axis of the point of interest on the image plane of the imaging means placed at the reference position: determined by the coordinate position on the Y-axis of the point of interest on the image plane of the imaging means placed at the reference position. Range number (3)
Position measurement method described in section. (5) A television camera is used as the imaging means, and two television cameras are placed at the standard position and the reference position to photograph the standard two-dimensional image and the reference two-dimensional image, respectively. Claim No. (1)
The position measuring method according to any one of paragraphs to (4). (6) A television camera is used as the imaging means, one television camera is placed at the reference position to photograph the reference two-dimensional image, and the television camera is further moved to the reference position to capture the reference two-dimensional image. A position measuring method according to any one of claims (1) to (4), characterized in that an image is photographed. (7) After preparing the reference two-dimensional image by placing the target object at the reference position and photographing it with the imaging means, a first reference image is placed at a given distance d in a given direction from the reference position. A first reference two-dimensional image is prepared by photographing the target object by the imaging means at the position, and a correlation between the reference two-dimensional image and the first reference two-dimensional image is determined, and the reference two-dimensional image is obtained. determining a first reference area including the point of interest image of the target object in the first reference two-dimensional image that has the highest correlation with the area including the point of interest image of the target object in the two-dimensional image; Furthermore, a second reference two-dimensional image is prepared by photographing the target object with the imaging means at a second reference position further away from the first reference position by the given distance d in the given direction. The correlation between the first and second reference two-dimensional images is determined, and the second intermediate two-dimensional image having the highest degree of correlation with respect to the first intermediate reference area is selected. Determine a second reference area that includes the focal point image of the target object, repeat the above operation n (n≧2) times, determine the n-th reference area of the n-th reference two-dimensional image, and then Three-dimensional coordinates of the point of interest on the target object from the position of the point of interest in the dimensional image, the position of the point of interest within the n-th reference area in the n-th reference two-dimensional image, and the distance nd. A position measuring method according to any one of claims (1) to (6), characterized in that the position is determined. (8) The image obtained by the imaging means is stored in an image storage device, the image stored in the image storage device is read out, and the correlation is detected by an image analysis device. The position measuring method according to any one of the ranges (1) to (7). (9) Claim (1) characterized in that two television cameras are arranged at the standard position and the reference position to photograph the standard two-dimensional image and the reference two-dimensional image, respectively. The position measuring method according to any one of paragraphs to (8).