SU847037A1 - Method of stereo x-ray grammetric survey - Google Patents

Description

(54) C-WAY STEREORENTGENOGRAMMETRIC SURVEY.

one

The invention relates to X-ray photogrammetry and is intended primarily for the topometry of hollow objects.

There is a method of stereoscopic X-ray photography, which provides for contrasting the external surface of the Object, obtaining a stereo pair of X-ray images with known elements of internal and external orientation, measuring the coordinates of the object images on the stereo pairs and determining the coordinates of the object points from the measured internal and external orientation 1 .

However, the known method does not allow to determine the coordinates of the internal structure of the object.

In addition, there is a method of stereographic X-ray imaging of internal organs, which involves obtaining a stereo pair of X-ray images with known elements of internal and external orientation, measuring the coordinates of object images in stereo pairs and determining the coordinates of object points from measured coordinates

points of the snapshot taking into account the values of the element (internal and external orientation 2.,

The disadvantage of this method is that it only determines the size and position of the object being studied, for example, the trachea, and reproduce the topography of the wall of the hollow organ, where

10 pathologists occur, fails. This is due to the low resolution of the X-ray image, removed at a great distance from the area under study, and the shading of the area under study by structures,

15 located between the subject and the photographic material. For example, a tracheal image may be obscured by the structure of the spine.

20

The purpose of the invention is to improve the accuracy of determining the coordinates of object points.

This goal is achieved by the fact that in the method of stereoscopic X-ray photography by obtaining a stereo pair of X-ray images with known elements of the internal and external orientation, measuring the coordinates of the images of the object on

30 snapshots of stereo pairs and definitions

coordinates of object points by measured coordinates of image points taking into account known values of elements of internal and external orientation, simultaneously with receiving each of the main stereo pairs additional images are exposed on the photo material on which radiopaque marks are superimposed, and the photo material is located in the immediate vicinity of the object under study in the overlap area main pictures of a stereo pair, form a stereo pair from additional pictures, and elements of internal and external orientation the additional stereo pair is determined by the measured coordinates of the images of the marks on the main and additional images of the object.

FIG. 1 and FIG. 2 shows the principle of obtaining the main and additional stereo pairs of images; Figs. Images of the main stereo pair; Fig.4 snapshots of an additional stereo pair; in fig. 5 and FIG. 6 - main and additional X-ray images of the object; in fig. 7 is a geometrical connection between the main and additional with nami.

The method is carried out as follows. ,

The object to be examined, for example, a hollow vessel 1, on the inner wall of which there are cracks 2 to be measured, is placed on the deck 3 of the object table of the radiographic stand. It is better to use a special two-tube radiographic stand, for example, a stereo x-ray device, which has a mechanism for adjusting the x-ray tubes. Usually by adjusting, the main point of the image coincides with the origin of the coordinate system of the image (x UO focal lengths of the left and right images were identical (ff). Under the deck 3 of the subject table there is a cassette 4 with x-ray film 5. With the help of holders b made from plexiglass, an additional cassette 7 with an X-ray film 8 is inserted into the vessel 1. On the front side of the cassette 7, radiopaque marks 9, for example, four, are fixed. The steel balls with a diameter of 1-2 mm can serve as marks. place the bottom at the vertices of the square. Object 1 and cassette 7 are oriented so that the area of study of the crack 2 is in the area of the stereo X-ray overlap of the stereo pair formed by the images

. Stereo X-ray

produced by alternate operation

X-ray tubes. Initially, the x-ray lena 1 is switched on, the real focus of which is open) keH at point F. After recharging the film, the cassettes 4 and 7 are reset. X-ray diffraction is performed with an HF tube 11, the actual focus of which is located at point F (see Fig. 2.). .

The obtained images of P, P and P p form the main and additional stereo pairs (Fig, 4),

An additional shot of P (figure 5) gives a clear image of 12 cracks. 2 and the inner surface of the container, while the main image P shows the image quality 12 of the cracks 2 and the inner surface and is much worse (the geometric blur is strongly influenced). In addition, the image of the cracks 2 is shaded by the image 13 of the structure 14 of the opposite wall of the vessel 1, Control marks 9 are depicted by dots on the main stereo pair a, b, c, d and on the additional - a, b, c, d.

The additional stereo pair is used for decoding and measuring the coordinates of the point image of the object, and the elements of the internal and external orientation of the images of the additional stereo pair are determined from the measured coordinates of the images of the radiopaque marks on the main and additional X-rays of the object. Elements of internal and external orientation of images. The main stereo pairs are known.

To determine the elements of the internal and external orientation of additional images, we use the well-known linkage formulas in photogrammetry between the x coordinates. , y, point of the image and coordinates Xi, Y, corresponding point of terrain I

 (U, -Х) -УХЛ)) 1) ° с, 1.х, -х „), СХ-Х,) - (2г,) 1

city () (state

 C ,,, - (X - X,) (, (7.-2);

where yj - coordinates of the main point of the image; f is the focal distance

snapshot;

XP, YQ, ZO - coordinates of the point of photographing;

Claims (2)

a-, / C corrective cosines evolution from the corner elements of external orientation, a, 7K as follows: a- (cbsct.-cosjg, - sinet-slnu} sinl & aa -cosot-sln - sinat "slnu)" cosjt; an, -z1n (X cosaj; b cosLt) sinx ,; Ь „cosuj-cosu; (2 (jj; c since cosjl + coscfc-sinu sin; sinotSinK + cosctsiriLU C. COSctCOSW. In our case (Fig. 7) of the formula (1), the following view is a, c rVa, - x.j.y.-. with „V Y- f о-.-b Y.-fc ,, where X, v ;. are the coordinates of the images of the check marks a {| | c with d, measured on the additional image in system x y xy y are the coordinates of the main point of the image in the system If xy o; f is the focal length of the image P, and y is the coordinates of the images of the reference marks a, b, measured on the main image in the system xy,; f is the focal distance of the image P To determine the values of the elements ct, w ,, XQ, PP, and f, it is sufficient to solve the system of equations (3) compiled by at least three check marks. With an increase in the number of check marks, and hence the number of equations, the problem can be solved by the method of least squares. The elements of internal and external orientation are determined independently of the left P and right P images of additional stereopairs. The coordinates of object points are determined by the coordinates of their images on an additional stereo pair taking into account the elements of the internal and external orientation of these images and using well-known link formulas. between the coordinates of the ki of the object and its image on the pairs of images .. The process stereorentgenogram metric shooting can improve the quality of X-ray Image voltage and improve the accuracy of measuring the coordinates have been reduced geometric blur (see. Fig.5, PacqMOTpHM formula of geometric unsharpness, -4 / where d is the value of geometric unsharpness UF - the size of the real. focus x-ray tube; f is the focal distance of the shot; h - removal of the object point from the photo material. The key picture is taken at f 100G mm, AF 1 mm, h h 200 mm. Enter these values in the formula (4), we get 2 mm. An additional shot is obtained at f 800 mm, AF 1 mm, h-10 mm. In this case, LD -0.01 mm. A sharp decrease in the geometric unsharpness increases the resolution of the X-ray image and, consequently, improves the accuracy of measuring the coordinates. The shading of the study area by structures located between the subject and the photographic material (see Figs. 5 and 6) is excluded, which is extremely viable, since the process of decryption of the studied area of the object is greatly facilitated and accelerated. Claims An inventive stereo x-ray method for taking x-ray stereo pairs with known interior and exterior orientation elements, measuring object image coordinates in stereo image pairs, and determining object coordinates using measured coordinates of image points using interior and exterior orientation parameters, characterized in that , in order to improve the accuracy of determining the coordinates of the points of the object, simultaneously with the receipt of each of the main The stereo pairs exhibit additional images on the photo material on which radiopaque marks are placed, the photo material is located in the immediate vicinity of the object under study in the overlap area of the main stereo pair images, the stereo pair is formed from the additional images, and the internal stereo pairs are measured using the measured coordinates images of tags on the main and additional images from the object. . Sources of information taken into account during the examination 1. USSR Author's Certificate No. 626349, cl. G 01 C 11 / 06.18.05.1977. 2. Surveying and aerial photography. Lime universities. 1977, No. 5, P..119124 (prototype) .., VT-t ih H V, a47 4A L / - / / I 5f -fa v {pue. // VV v m V r. yi .ii / feix -rVw .j:, / y ::,; t / 1; four