JPH08313214A - Position-specifying method - Google Patents

Abstract

PURPOSE: To specify the position of a moving object on the basis of the amount of time-based change of an image by a method wherein corresponding points in two images picked up from two spots are calculated from the respective time-based changes at the spots. CONSTITUTION: Image pickup devices 1 and 2 are installed at two spots A and B being apart by a distance L from each other. Images A1 and B1 picked up by the devices 1 and 2 at the time t1 are taken in image memories 3 and 4 respectively and images A2 and B2 picked up at the time t2 are taken in image memories 5 and 6 respectively. Based on the images taken in, difference images A2-A1 and B2-B1 are prepared by an image processing part respectively. In these difference images, an amplitude is large only in a region wherein a change occurs by a move of an object, while the amplitude is small in a region such as a background wherein the change is small. A circumscribed template, e.g. a rectangular template, is set about the changing region and points PA and PB of the centers of the rectangles are made corresponding points. The position of the object is specified on the basis of positions of picture elements of the points PA and PB of the centers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method used for image measurement, and more particularly to an image processing method used for specifying a position of a moving object and measuring a distance.

[0002]

2. Description of the Related Art FIGS. 5 (a), 5 (b) and 5 (c) are diagrams showing a method of measuring a distance to an object by specifying a position P of the object by an image processing technique. The law is
Positioned by two image pickup devices A and B separated by a distance L respectively
After picking up an image of the object at P, searching for and identifying the corresponding points in the two images obtained by each imaging device, the angle θa at which the corresponding point is viewed from point A and the corresponding point from point B are determined. It is a stereo image method that specifies the position of P by the triangulation method of calculating the viewing angle θb respectively. In the stereo image method, calculation of corresponding points in two images is the most important. As a method of calculating the corresponding points, there is a method of calculating the cross-correlation of images and using the position having the largest correlation as the corresponding points.

However, in the above-mentioned conventional method, a portion that can be observed in the image obtained by one of the image pickup devices cannot be observed in the image obtained by the other image pickup device,
As a result, there is a drawback that the corresponding points in the two images cannot be calculated. For example, when the position of the ship is not specified as shown in FIG. 6, the image taken by the image pickup apparatus A is shown in FIG.
Although the side of the ship can be seen in the image of Fig. 6C, which is the image taken by the image pickup device B, only the rear part of the ship can be confirmed. Parts cannot be used as corresponding points. Therefore, in the above-mentioned conventional method, it is necessary to specify the corresponding points only from the portions that can be commonly observed in the images obtained at the two points A and B. It is necessary to set it in advance by using it, which limits the measurement target.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to eliminate the drawbacks such as the situation where the measurement is difficult and the measurement object is limited as described above.
An object of the present invention is to provide a position specifying method in which a measurement target is not limited by calculating corresponding points in one image from a temporal change of each point.

[0005]

SUMMARY OF THE INVENTION A first means of a position specifying method according to the present invention for achieving the above object is to take an image of an object at a time t1 and a time t2 at a plurality of points separated by a known distance. Then, an area showing a temporal change is obtained from the difference image between the time t2 and the time t1, and the corresponding points of the object are calculated from the area,
The feature is that the position is specified by the triangulation method. The second means of the position specifying method according to the present invention is to detect an image A at time t1 at two points A and B separated by a known distance l.
Images A2 and B2 are taken at time point 1, B1 and time t2, and the time points t2 and
It is characterized in that the corresponding points of A and B are calculated from the difference images A2-A1 and B2-B1 with respect to t1 using the area showing the temporal change, and the position is specified by the triangulation method. A third means of the position specifying method according to the present invention is, in the first or the second means, creating a template for calculating a corresponding point with respect to an area showing a temporal change, and setting a predetermined position of the template. Is used as the corresponding point, and the position is specified by the triangulation method.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the drawings showing the embodiments. 1 and 2 are a block diagram and a flow chart of an embodiment of the present invention, respectively.
As shown in FIG. 1, the image pickup devices 1 and 2 are installed at two points A and B separated by a distance L, and at time t1, the images A1 and B1 picked up by the image pickup devices 1 and 2 are stored in the image memories 3 and 4, respectively. At the time t2, the images A2 and B2 captured by the image capturing devices 1 and 2 are captured in the image memories 5 and 6, respectively.

FIGS. 3 (a) and 3 (b) are examples of images A1 and B1 captured at time t1, and FIGS. 3 (c) and 3 (d) are examples of images A2 and B2 captured at time t2. Based on the captured image, an image processing unit not shown in FIG.
, (F), the difference images A2-A1 and B2-B1 are created respectively (FIG. 2, steps S1 to S3). In these difference images, the amplitude is large only in the area changed by the movement of the object, and the amplitude is small in the area where the change is small such as the background. The shaded areas in Figs. 3 (e) and (f) show the large amplitude regions. In the present invention, a template circumscribing the change area, for example, a rectangular template is set, and the center points PA (xa, ya) and PB (xb, yb) of the rectangle are set as corresponding points. Each center point
The position P of the object is specified based on the pixel positions of PA and PB (steps 4 to 6).

FIG. 4 is a principle diagram of a position specifying method using the triangulation method in the present invention. Here, image pickup devices are installed at two points A and B such that the optical axes of the respective lenses are parallel to each other. Let the plane containing the two optical axes be the xy plane, the axis perpendicular to the plane xy be the z axis, the coordinates of the object be P (x, y, z), and H be the legs of the perpendicular line hung in the xy plane. , The focal length of the lens is f, and the center of each image plane of the image pickup devices A and B is 0A.
, 0B. The image plane is inverted vertically and horizontally.

From the similarity relation, the following expression xa: x = f: y-xb: (l-x) = f: y ya: z = yb: z = f: y holds. By solving the above equation, x = l ・ xa / (xa-xb) y = f ・ L / (xa-xb) z = l ・ ya / (xa-xb) = l ・ yb / (xa-xb) The position is calculated as

In the above description, the optical axes are assumed to be parallel for the sake of simplification of description, but the optical axes do not necessarily have to be parallel, and the relationship between the optical axes of the image pickup devices at two points does not have to be. If known, the position can be specified. Further, in the above embodiment, 2
Although the point measurement has been described as an example, the present invention is not limited to this, and more accurate position identification can be performed by calculating the corresponding points described above at a plurality of points and specifying the position of the object. Becomes

[0011]

Since the present invention is configured as described above, the position of a moving object can be specified by the time change amount of an image with the passage of time, and corresponding points can be detected in images at two points. The position can be accurately specified even in a situation where it is impossible.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention.

FIG. 2 is a flowchart showing a position specifying procedure according to the present invention.

3 (a), (b), (c) and (d) are explanatory views of an image captured by the present invention, and (e) and (f) are diagrams showing a difference image and corresponding points.

FIG. 4 is a principle diagram showing position identification by a triangulation method.

5A is a plan view showing a stereo image method using a conventional triangulation method, FIG. 5B is a view showing an image taken at a point A in FIG. 5A, and FIG. The figure which shows the image imaged in the B point.

[Explanation of symbols]

 1, 2 imaging device, 3, 4, 5, 6, image memory.

Claims (3)

[Claims] 1. A plurality of points separated by a known distance,
Images of the object are taken at time t1 and time t2, respectively.
And a region showing a temporal change from the difference image between time t1 and
A position specifying method characterized in that corresponding points of the object are calculated from the area and the position is specified by a triangulation method. 2. Images A1, B1 at time t1 and images A2, B2 at time t2 at two points A, B separated by a known distance L.
Respectively, and the difference images A2-A between time t2 and time t1
1, B2-B1 to obtain a region showing a temporal change, calculate the corresponding points between the images based on the region showing the temporal change, and specify the position by triangulation. The position identification method according to item 1. 3. A template for calculating corresponding points is created with respect to the region showing the temporal change, and a predetermined position of the template is set as a corresponding point, and the position is specified by a triangulation method. 3. The position identifying method according to claim 1, wherein