RU2413396C1 - Laser centraliser for x-ray emitter - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: laser centraliser for an x-ray emitter has a housing in which there is a laser range finder, the laser axis of which is parallel to the longitudinal axis of the x-ray emitter, two mirrors, the first made from organic glass and placed at the intersection of the axes of the laser and x-ray beams perpendicular to the formed plane at an angle of 45 degrees to the axis of the laser, and the second mirror is placed on the axis of the laser at an angle of 45 degrees to the said axis, and its centre lies at a distance A from the centre of the first mirror, which is equal to the distance from the said mirror to the focus of the x-ray tube on the axis of the x-ray beam, a television system consisting of a lens, a CCD matrix and a monitor, wherein the optical axis of the lens passes through the centre of the second mirror and coincides with the perpendicular running from the said centre to the axis of the laser. There is a light filter in front of the lens for increasing contrast of the images of laser structures on the object, and there is an annular structure of N>8 microlasers on the axis of the laser of the range finder, perpendicular to the axis and symmetrically placed about the axis at a distance B from the centre of the second mirror. Optical axes of the microlasers are inclined to the axis of the laser of the range finder at an angle α/2 to the planes formed by axes of the microlasers and the axis of the laser and which, after reflection from the first mirror, form on the object an image of the annular structure of laser spots, the dimensions and shape of which correspond to the size and shape of the zone illuminated by x-rays. The axis of the laser of the range finder after reflection from the first mirror coincides with the axis of the x-ray beam and forms on the object a laser spot which coincides with the point of intersection of the axis of the laser beam with the object and with the centre of the annular structure of laser spots formed by the annular matrix of the microlasers. The second mirror has a centre opening for passage of the beam of the laser range finder. The annular matrix of microlasers with diametre D lies at a distance B=D/2tg(α/2) from the centre of the second mirror, where α is the divergence angle of x-ray beams. The centraliser also includes a rectangular matrix of microlasers with an order of K*T, where K and T are dimensions of the radiographic film in the holder for radiographing. This matrix lies in the housing of the centraliser symmetrically about the axis of the x-ray beam. Optical axes of M>8 microlasers are parallel to each other and he axis of the x-ray beam and form on the object a rectangular structure of laser spots with dimensions K*T, which does not change when the distance from the object to the centraliser L changes and through which the ratio of dimensions of the zone of the object illuminated with x-rays and the actual zone for recording radiographic images, determined by dimensions of the radiographic film used, can be determined. For better distinction of this and the annular structure of laser spots, the radiation of microlasers which form the rectangular structure can be modulated with frequency F>=1-10 Hz, and the focal distance f of the lens of the television camera satisfies the condition f<R*L min/s, where L min is the minimum distance from the object to the centraliser in the working measurement range of these distances, c is the size of the CCD matrix of the television camera, R is the diagonal of the sheet of the radiographic film with dimensions K*T.

EFFECT: high reliability owing to prevention of faults during operation of the laser centraliser due to spurious glares on the surface of the mirror of the laser range finder.

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Description

The invention relates to the field of non-destructive testing of objects using x-ray radiation. A known centralizer for an x-ray emitter, comprising a laser rangefinder and a television camera, the optical axes of which are parallel to the axis of the x-ray beam, and also an annular array of microlasers, forming on the object an image of the ring structure of laser spots, the position, size and shape of which coincide with similar geometric parameters of the zone, X-ray transmitted [1].

The disadvantages of this centralizer are the presence of a translucent mirror in front of the laser range finder, which causes malfunctions due to spurious light flares on the surface of this mirror, as well as the impossibility of assessing the ratio of the sizes of the object’s translucent zone by x-ray radiation and the film cassette used for radiography.

The purpose of the invention is the elimination of these disadvantages.

To do this, in the laser centralizer for the x-ray emitter, containing a housing in which the laser range finder is located, the laser axis of which is parallel to the longitudinal axis of the x-ray emitter, two mirrors, the first of which is made of plexiglass, at the intersection of the axes of the laser and x-ray beams perpendicular to the plane they form at an angle of 45 degrees to the laser axis, and the second is located on the laser axis at an angle of 45 degrees to it, and its center is at a distance A from the center of the first mirror, equal to the distance from about the focus of the X-ray tube along the axis of the X-ray beam, a television system consisting of a lens, a CCD matrix and a monitor, while the optical axis of the lens passes through the center of the second mirror and coincides with a perpendicular drawn from this center to the laser axis, a filter is located in front of the lens to increase the contrast of images of laser structures on the object, and on the axis of the laser of the range finder, perpendicular to it and symmetrically relative to it at a distance B from the center of the second mirror, an annular structure is established of laser numbers N> 8, whose optical axes are inclined to the laser axis of the rangefinder at angles α / 2 in the planes formed by the axes of the microlasers and the laser axis, and which, after reflection from the first mirror, form an image of the ring structure of laser spots on the object, the dimensions and shape of which correspond the size and shape of the zone, X-rayed, the laser axis of the range finder after reflection from the first mirror coincides with the axis of the X-ray beam and forms a laser spot on the object that coincides with the intersection point of the p axis x-ray beam with an object and with the center of the annular structure of laser spots formed by the annular matrix of microlasers, the second mirror is made with a central hole for the beam of the laser rangefinder, the annular matrix of microlasers with a diameter D is installed from the center of the second mirror at a distance B = D / 2tg (α / 2 ), where α is the angle of divergence of the x-ray beam, a rectangular matrix of microlasers of size K * T is introduced into the centralizer, where K and T are the dimensions of the radiographic film in the cassette for radiography, this matrix and it is located on the centralizer case symmetrically with respect to the axis of the x-ray beam, the optical axes of microlasers of number M> 8 are parallel to each other and the axis of the x-ray beam and form a rectangular structure of laser spots of size K * T on the object, which does not change when the distance from the object to the centralizer L, and with the help of which it is possible to judge the ratio of the size of the zone of the object, x-rayed and the real registration area of radiographic images, determined by the size of the applied radio optical film, moreover, to better distinguish between this and the ring structure of laser spots, the radiation of microlasers forming a rectangular structure can be modulated with a frequency Ф> = 1-10 hertz, and the focal length F of the camera lens is selected taking into account the ratio F <R * Lmin / C where Lmin is the minimum distance from the object to the centralizer in the working range of changes in these distances, C is the size of the CCD matrix of the camera, R is the diagonal of the sheet of the radiographic film of size K * T.

The invention is illustrated by drawings (figure 1, a, b, c, d, d), which shows the General scheme of the centralizer (figure 1 a) and its individual elements.

The centralizer 1 comprises a housing 2 in which the first Plexiglas mirror 3 is located, the second mirror 4 with a central hole for the passage of the beam of the laser rangefinder 6 [2], the ring matrix 5 of the microlasers 13, the filter 7, the lens 8, the CCD matrix 9 and the monitor 10 television system, frame 11 with a rectangular matrix of microlasers 14. FIG. 1 b, c shows the arrangement of microlasers 13 and 14 in the respective matrices. Figure 1 g presents the design scheme for selecting the focal length of the lens. Figure 1 e shows a monitor screen with images of the annular and rectangular structures of laser spots on the object 12. The microlasers 13 and 14 can be identical or with different spectral, modulation and energy characteristics depending on the optical characteristics of the object 12 to ensure sufficient image contrast corresponding structures of laser spots.

Laser centralizer operates as follows. The operator combines the annular structure of laser spots with the area of the object to be controlled and visually inspects its surface. In this case, the rectangular matrix microlasers can be turned off to eliminate factors that impede this process. Then measure the distance from the object to the centralizer. The rectangular matrix microlasers are turned on and an assessment is made of the conformity of the film sizes and the area exposed to x-ray radiation. If necessary, the centralizer is positioned relative to the object, achieving the maximum filling of the film area with useful information, i.e. the complete inclusion of the ring structure of laser spots in the rectangular structure of laser spots. Then make a repeated measurement of the distance from the object to the centralizer using a laser range finder and proceed directly to the implementation of radiographic control procedures.

The above relations between the main geometric parameters of the optical elements of the centralizer - the focal length of the lens F, the size of the matrix C, the diagonal of the rectangular matrix R and the distance from the object to the centralizer L are illustrated in Fig. 1 a and do not need additional explanations. Note that the angle of the field of view of the lens is W = 2arctg (C / 2F), which is also clear from FIG. 1 a [3]. Figure 1 g shows similar triangles OAV and OEP, the ratio of the heights of which is proportional to the ratio of their bases, i.e. R * C = Lmin / F, whence F <R * Lmin / C follows. The fulfillment of this condition ensures that the image of the rectangular matrix of microlasers is in the field of view of the lens of the television system in the entire range of changes in the distance from the centralizer to the object, starting with its minimum value. In this case, the focal length of the lens is considered to be significantly less than this distance, i.e. F << L, which is almost always performed in practice, because usually L> = 3 m, and F <= 50-100 mm.

Information sources

1. RF patent No. 2237984. Laser centralizer for x-ray emitter.

2. Laser rangefinder "DISTO", avenue of the company LEICA, Austria.

3. Handbook of the designer of optical-mechanical devices, L., Mechanical Engineering, 1986, 680 pp.

Claims (1)

A laser centralizer for an x-ray emitter, comprising a housing in which a laser rangefinder is located, the laser axis of which is parallel to the longitudinal axis of the x-ray emitter, two mirrors, the first of which is made of plexiglass and is located at the intersection of the laser axes and the x-ray beam perpendicular to the plane they form at an angle of 45 ° to laser axis, and the second is located on the laser axis at an angle of 45 ° to it at a point located at a distance A from the center of the first mirror, equal to the distance from this center to the focus of the x-ray smoothes along the axis of the X-ray beam, a television system consisting of a lens, the optical axis of which coincides with the perpendicular drawn from the center of the second mirror in the plane formed by the laser axes and the longitudinal axis of the X-ray emitter, CCD matrix and monitor, a light filter for contrasting images of laser structures on the object located in front of the lens, an annular matrix of N≥8 microlasers, the optical axes of which are inclined to the laser axis at an angle α / 2 in the planes formed by the axes of the microlasers and laser d flax meter, where α is the angle of divergence of the X-ray beam, these microlasers are located symmetrically with respect to the axis of the laser of the rangefinder on a circle of diameter D at a distance B from the center of the second mirror and form an annular structure of laser spots on the object after reflection from the first mirror, the dimensions and shape of which correspond to the size and the shape of the zone of the object, x-rayed and the center of which coincides with the point of intersection of the axis of the x-ray beam with the object illuminated by the laser of the range finder, characterized in then the second mirror is made with a central hole for the passage of the laser beam from the range finder, the annular matrix of microlasers is installed at a distance B = D / 2tg (α / 2), a rectangular matrix of M = 8 microlasers located on the centralizer case symmetrically with respect to the x-ray axis is introduced into the centralizer of the beam, the matrix size K × T corresponds to the size of the applied radiographic film, the optical axes of the rectangular matrix microlasers are parallel to each other and the x-ray beam axis and with the help of these microlasers In this case, a rectangular structure of laser spots is formed, the size and shape of which remain unchanged when the distance from the object to the centralizer changes, which makes it possible to judge about the ratio of the size of the object zone illuminated by X-ray radiation and the marked ring structure of laser spots and the actual surface area of the film exposed, while the focal length of the lens of the television system is selected taking into account the ratio F≤R · L min / C, where R is the diagonal of a rectangular sheet of film of size K × T, L min is the minimum The distance from the object to the centralizer in the working range of this distance changes, which ensures that the rectangular matrix of laser spots on the object is constantly in the field of view of the television system.

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