EP2333786B1 - Asymmetric slit diaphragm and device and method for producing same - Google Patents

Abstract

The aperture has an absorption element (52) with a non-even outer surface (54), whose partial region lies on a ruled surface. Another absorption element (56) has another non-even outer surface (58), whose surface contour is formed partially complimentary to the outer surface of the former absorption element. The two absorption elements are positioned such that a gap is formed between the two outer surfaces. The distance in a direction (y) perpendicular to an optical axis (x) between generatrixes of the ruled surface reduces toward an imaging region. Independent claims are also included for the following: (1) a device for manufacturing a slot aperture (2) a method for manufacturing a slot aperture.

Description

The invention relates to a slit diaphragm, in particular an asymmetrical slit diaphragm with extended opening angle for imaging radiating and backscattering objects, according to the preamble of claim 1, and an apparatus and a method for producing the same, according to the preambles of claims 8 and 13.

Frequently the problem arises of determining the form of hidden sources of high-energy, in particular ionizing radiation beyond the optical spectrum (in particular X-ray or gamma radiation with photon energies above 20 keV) of unknown structure or spatial structure. The radiation source can be, for example, the effective focal spot on the anode of an x-ray tube or surface-distributed radiating material. The latter can be radioactive waste distributed over a room in a collecting bin, whereby alleged discrepancies between declaration and actual content must be clarified. Further examples of radiation sources whose shape one wishes to image are deposits with uranium-containing ores or nuclear facilities, in which it is often of importance not only to determine the nature of the radiation, but also to determine the spatial structure of the radiation sources. In addition to the sources mentioned, which generate the high-energy radiation directly, are also those that generate them by X-ray or Gammarückstreuung. With the help of the image of backscattered radiation, it is also possible, for example, to examine objects radiographically for which only one-sided access is possible.

To illustrate the shape of such radiation sources, it is obvious to apply the principle of a camera. Quite different area detectors can be used: film material, storage disks, storage foils, semiconductor flat detectors, vidicams, image intensifiers or converter foils. Since such recordings can also and especially occur in environments in which persons should not enter, if possible, the simplest operability must be ensured. The simplest functionality and handling would be to remotely place a corresponding device with retrieval after the exposure time without any operation of any controls.

It is known to use the Lochkameraprinzip when imaging with the help of high-energy radiation. In a pinhole camera or camera obscura , a small hole on a projection surface produces an image of illuminated or radiating objects. The small diameter of the diaphragm limits the incident beam to a small opening angle and thus prevents the complete overlap of the beams in the imaging surface. Radiation from an upper portion of a radiating body is incident on the lower edge of the projection surface while, conversely, rays are imaged from the lower portion to the upper edge of the projection surface. Thus, each point of the object is imaged as slices on the projection surface, so that the superimposition of the slice images provides an image of the radiating body whose resolution depends on the distance of the radiating body and the shape of the diaphragm.

The problem with high-energy radiation is that, because of its high permeability, the thickness of the material for the pinhole diaphragm must be large, that is to say in relation to the half-value thickness of the intensity of the radiation used for imaging. Therefore, the achievable image quality is essentially determined by aperture diameter and material thickness and density. Often, therefore, one obtains at best a shadow image of the actual pinhole, wherein the pinhole, which is to serve for imaging, due to the wall thickness becomes a collimator, which can pass only a straight-line beam. Therefore, the aperture in the hole cameras is often trumpet-shaped with the narrow spot to the radiation source designed so as not to lose the imaging properties completely. In the case of high-energy radiation, the solutions known from the prior art have a considerable deviation from the ideal hole-camera principle due to the required material thickness.

In the patent DE 10 2005 029 674 B4 a shutter is disclosed which overcomes some of the disadvantages described. The aperture can be realized with almost any material thickness without losing its imaging properties. The diaphragm is suitable for limiting radiation originating from a radiation source, in particular high-energy radiation, and for directing it to an imaging region along an optical axis x according to the hole-camera principle. The diaphragm comprises a first absorption element, which has a first non-planar outer surface whose surface contour can be described at least partially by a function of the form z (x, y) = f (y) * x + n, and a second absorption element which a second non-planar outer surface whose surface contour is formed at least partially complementary to the non-planar outer surface of the first absorbent member, wherein the two absorption elements are positioned or positioned so that between the two non-planar outer surfaces, a gap is present.

The disadvantage of this panel that the camera body is unwieldy and heavy; including the shield, the camera assembly typically weighs 200 to 300 kg. Another disadvantage is the long exposure time; In particular when imaging backscattering objects, an exposure time of more than half an hour may be required due to the low intensity of the backscatter radiation.

The object of the invention is therefore to provide a slit diaphragm for a pinhole camera, which compared to that in the patent DE 10 2005 029 674 B4 disclosed aperture a more compact camera design and a higher intensity on the imaging surface and thus allows a shorter exposure time. The object area to be imaged should be retained.

According to the invention the object is achieved by means of a slit diaphragm, in particular an asymmetrical slit diaphragm with extended opening angle for imaging radiating and backscattering objects, with the features mentioned in claim 1.

An absorption element here is to be understood as an element which has at least one region which at least partially absorbs the radiation. A gap is to be understood as meaning a region which absorbs the radiation to a small extent. It may be filled with air or other suitable material which absorbs the radiation less than the portions of the absorption elements at least partially absorbing the radiation, which material may be in the form of a separate insert or a coating applied to at least one of the non-planar surfaces ,

A ruled surface is an area in which there is a straight line at every point on the surface that lies completely within the surface. These completely in-plane straight lines are referred to as the generators of the control surface. The Gaussian curvature of a surface at a point is the product of its two main features in the point; the principal curvatures of the area at a point are the minimum value and the maximum value of the curvatures of all curves resulting from intersecting the area with a plane containing the surface normal on the point.

und ist somit auf der gesamten Fläche von Null verschieden.An example of a rule surface is that in the patent DE 10 2005 029 674 B4 used surface, which can be described by a function of the form z (x, y) = f (y) * x + n . The generators of this control surface have the straight line equations r = (0, y ₀ , n) + λ (1,0, f (y ₀ )), where each value of the parameter y ₀ corresponds to exactly one generator. In particular, the area covered by the in the patent DE 10 2005 029 674 B4 the function z (x, y) = C * y * x + n described by the straight line equation r - = (O, y ₀ , n) + λ (1.0, Cy ₀ ) . Its Gaussian curvature at the point (x, y, z (x, y)) is $$\mathrm{\kappa }=-\frac{C^2}{{\left(1+C^2\left(x^2+y^2\right)\right)}^2}$$

and is therefore different from zero over the entire area.

To determine which ruled surfaces for further development in the patent DE 10 2005 029 674 B4 disclosed apertures are considered, the directions in which beams can invade unhindered or almost unhindered. The generators of the control surface provide a one-parameter set of directions along which rays of light can enter unimpeded. However, to create a two-dimensional image, a two-dimensional manifold of rays must pass through the aperture. The required second degree of freedom results from the fact that bundles of rays incident on a plane of the control surface in the tangential plane pass through the diaphragm almost unhindered if they do not differ too much from the generator passing through this point, since in this case only one gives slight, at the distance from the point under consideration square deviation from the control surface.

As a condition for the realization of a two-dimensional mapping thus results that the change in direction when passing through the generatrix and the change in direction when rotating the generators in the tangent plane from each other must be linearly independent; only in this case, these two changes in direction lead to a two-dimensional manifold unhindered or almost unhindered transmitted beams.

It is known from differential geometry that the Gaussian curvature of a rule surface disappears at a point just when the derivative of the direction vector of the generator and the tangent perpendicular to the generator are collinear. It It follows that a two-dimensional image is produced if and only if the Gaussian curvature of the control surface does not disappear anywhere in the used subarea of the control surface.

From the patent DD 240 091 A1 and the publication DE 40 00 507 A1 For example, panels for high-energy radiation are known in which partial areas of ruled surfaces are used to form a gap, ie of cones or flat areas. In both cases, however, the Gaussian curvature disappears over the entire control surface, which is thus not suitable for obtaining two-dimensional images.

In order to increase the intensity on the imaging surface, the camera structure is to be brought closer to the object. Both the downsizing of the camera body and the closer approach to the object require an enlargement of the viewing angle. This becomes all the more necessary when small-area semiconductor-based flat panel detectors are to be used. These have the advantage of not only converting the image directly into digital signals, but also being available with very high sensitivity. The enlargement of the viewing angle requires a corresponding adaptation of the diaphragm geometry in order to achieve a fan-shaped beam guidance.

A fan-shaped beam guide was also in the published patent application DE 10 2005 048 519 A1 revealed focal point oriented roller blind used. However, this is not based on the Lochkameraprinzip, but directed in each position only one beam to the detector located in a focal point; a two-dimensional image is obtained only by turning the roller shutter and line by line scanning of the object.

Like the one in the patent DE 10 2005 029 674 B4 disclosed aperture is the slit diaphragm according to the invention suitable to limit radiation emitted by a radiation source, in particular high-energy radiation and directed along an optical axis according to the Lochkameraprinzip on an imaging area, and comprises a first absorption element, which has a first non-planar outer surface of the at least one subregion lies on a control surface whose Gaussian curvature does not disappear in the subregion, and a second absorption element which has a second non-planar outer surface whose surface contour is at least partially complementary to the non-planar outer surface of the first absorption element is, wherein the two absorption elements are positioned or positioned so that between the two non-planar outer surfaces, a gap is present.

The diaphragm according to the invention is further characterized in that the distance in a direction perpendicular to the optical axis between the generatrices of the control surface decreases towards the imaging region. This ensures that the approximately along the generatrix of the control surface incident beam converge almost unhindered through the aperture, converge behind the aperture and meet as close to the aperture on an imaging range, which can be significantly smaller than the diaphragm body. It is preferred that, at least in a partial region of the first non-planar outer surface, the distance between the generatrices of the control surface and the imaging region decreases in each direction perpendicular to the optical axis. It is thereby achieved that the radiation bundles incident approximately along the generatrix of the control surface converge particularly strongly towards the imaging region.

In a preferred embodiment of the invention, there is a central axis which intersects each of the generators of the control surface. As a result, the mapping rule is simplified, and with a suitable position of the diaphragm body, the area around the central axis can be used as the imaging area. On the other hand, it is achieved that the diaphragm can be produced by means of a device according to claim 9 or a method according to claim 14.

It is particularly preferred that the polar angles of the direction vectors of the generatrix of the control surface with respect to the central axis are linearly related to the intersection of the generatrix of the control surface with the central axis. This ensures that the mapping rule is approximately linear and the diaphragm can be produced by means of a device according to claim 10 or a method according to claim 15.

Under a linear relationship with the intersection of the generatrix of the control surface with the central axis is to understand a linear relationship with the distance of the intersection of the generatrix of the control surface with the central axis of any fixed point on the central axis. If the polar angles of the direction vectors of the generatrix of the control surface with respect to the central axis are in such a linear relationship with the intersection of the generatrix of the control surface with the central axis and this linear relationship is not constant In other words, ie both polar angles vary with the point of intersection, then the Gaussian curvature of the control surface does not disappear anywhere. Thus, the set of all ruled surfaces in which the polar angles of the direction vectors of the generators of the ruled surface with respect to the central axis are not constantly linearly related to the intersection of the generatrices of the ruled surface with the central axis is a subset of the ruled surfaces whose Gaussian curvature does not disappear anywhere; that is, the feature that the polar angles of the direction vectors of the generatrix of the control surface with respect to the central axis in non-constant linear relationship with the intersection of the generatrix of the control surface with the central axis, resulting in a slit diaphragm according to the invention, without the additional requirement that the Gaussian curvature the ruled surface disappears nowhere.

In a further preferred embodiment of the invention, the central axis is outside the diaphragm body. This ensures that the detector can be arranged in the vicinity of the central axis, so that an image can be recorded on the smallest possible area.

In a further preferred embodiment of the invention, the absorption elements have a trapezoidal plan, which widens towards the radiation source. This ensures that the outer shape of the absorption elements corresponds to the area used for the fan-shaped beam guidance.

In a further preferred embodiment of the invention, the opening of the gap on the radiation source facing side of the slit is greater than the opening of the gap on the imaging region side facing the slit. This ensures that the beams passing through the gap also converge in the direction perpendicular to the gap.

In a further preferred embodiment of the invention, the slit diaphragm comprises, in addition to the one gap, at least one further gap, the shape of which in each case results essentially from an affine image from the shape of the one gap, as in German Patent Application No. 10 2008 025 109.7-54 described in more detail. As a result, a better imaging quality and / or a larger imaging range and / or a higher beam yield is achieved. An affine image is an image of the three-dimensional space on itself, which maps each straight line to a straight line.

In the European patent application EP 2 062 705 A1 discloses an apparatus and a method for producing slit diaphragms, with which in the patent DE 10 2005 029 674 B4 disclosed slit diaphragm and in the published patent application DE 10 2005 048 519 A1 revealed focal point-oriented roller blind can be produced. It is a further object of the present invention to further develop this teaching in order to provide an apparatus and a method for producing a slit diaphragm according to the invention.

According to the invention this object is achieved by means of a device and a method for producing a slit diaphragm according to the features mentioned in claim 8 or claim 13.

Like the one in the European patent application EP 2 062 705 A1 In the disclosed apparatus, the apparatus for producing a slit includes a cutting tool adapted to cut along a straight line, and means adapted to effect relative movement between the cutting tool and a workpiece such that the cutting tool passes along the workpiece a line which corresponds to a beam path in the slit diaphragm to be produced. The cutting tool is adapted to cut along a first direction. The means comprise a holding element, on which a workpiece can be fastened and which is rotatably mounted about a first axis of rotation. The means are adapted to effect a first rotational movement of the retaining element about the first axis of rotation and at the same time a translational movement of the retaining element along the first axis of rotation. The first rotational movement and the translational movement of the retaining element are coupled.

This teaching is further developed by the present invention in that the means are further adapted to effect a second rotational movement of the holding member and the first axis of rotation about a second axis of rotation simultaneously with the first rotational movement and the translational movement, and the second rotational movement and translational movement of the retaining element are coupled. It is thereby achieved that the distance in the direction of the first axis of rotation between the cut beam paths decreases in the direction perpendicular to the first and second axes of rotation.

Preferably, the first axis of rotation, the second axis of rotation and the line along which the cutting tool cuts have a common point of intersection. Thereby it is achieved that the slit diaphragm produced by means of the device has the advantageous additional feature of claim 2. It is particularly preferred that the second axis of rotation is perpendicular to the cutting direction of the cutting tool and perpendicular to the first axis of rotation. It is further preferred that the translational movement and the first rotational movement are linearly coupled and the translational movement and the second rotational movement are linearly coupled. Such a linear coupling can be accomplished with particularly simple technical means. Furthermore, it is achieved that the slit diaphragm produced by means of the device has the advantageous additional feature of claim 3.

In a preferred embodiment of the invention it is provided that the cutting tool is arranged immovably. It is thus preferred that the cutting tool is stationary and the workpiece is guided around it. The starting point of this preferred embodiment is not to clamp the workpiece in a fixed support and to guide the tool, but conversely to move it in a controlled manner around a milling cutter or a cutting jet.

The means may comprise a first, a second and a third threaded shaft, wherein the first threaded shaft is parallel to the first axis of rotation, the second threaded shaft is located on the first axis of rotation and the third threaded shaft is located on the second axis of rotation. A rotational movement of the three threaded shafts may be coupled by a gear system.

The first screw shaft may include a portion formed as a screw shaft through which a support arm to which the second screw shaft is connected is movable along the first rotation axis.

As in the European patent application EP 2 062 705 A1 In the method according to the invention for producing a slit, a relative movement between a cutting tool which is suitable for cutting along a straight line and a workpiece is carried out such that the cutting tool cuts the workpiece along a line corresponding to a beam path in the plane a first rotational movement of the workpiece about a first axis of rotation and simultaneously a translational movement of the workpiece along the first axis of rotation is performed and the first rotational movement and the translational movement of the workpiece are coupled.

This teaching is further developed by the present invention such that a second rotational movement of the workpiece and the first axis of rotation about a second axis of rotation is carried out simultaneously with the first rotational movement and the translation movement and the second rotational movement and the translational movement of the workpiece are coupled.

Preferably, the first axis of rotation, the second axis of rotation and the line along which the cutting tool cuts have a common point of intersection. It is thereby achieved that the slit diaphragm produced by the method has the advantageous additional feature of claim 2. It is particularly preferred that the second axis of rotation is perpendicular to the cutting direction of the cutting tool and perpendicular to the first axis of rotation. It is also particularly preferred that the translational movement and the first rotational movement are linearly coupled and the translational movement and the second rotational movement are linearly coupled. Such a linear coupling can be accomplished with particularly simple technical means. Furthermore, it is achieved that the slit diaphragm produced by the method has the advantageous additional feature of claim 3.

For cutting the slot, any method known in the art may be used, including, for example, milling, fine milling, precision milling, blasting, jet milling or sawing.

Figur 1

eine bildgebende Einrichtung mit einer Blende;

Figur 2

(schematisch) eine Testanordnung;

Figur 3

eine Perspektivansicht eines ersten Ausführungsbeispiels einer erfindungs- gemäßen Schlitzblende;

Figur 4

eine Explosionsdarstellung der in Figur 3 gezeigten erfindungsgemäßen Schlitzblende;

Figur 5

eine Perspektivansicht des ersten Absorptionselements der in Figur 3 gezeigten erfindungsgemäßen Schlitzblende;

Figur 6

eine Perspektivansicht eines zweiten Ausführungsbeispiels einer erfindungsgemäßen Schlitzblende;

Figur 7

eine Perspektivansicht eines dritten Ausführungsbeispiels einer erfindungs- gemäßen Schlitzblende;

Figur 8

eine Perspektivansicht einer erfindungsgemäßen Vorrichtung zum Strahlfräsen einer Schlitzblende.

The invention will be explained in more detail in embodiments with reference to the accompanying drawings. Show it:

FIG. 1

an imaging device with a diaphragm;

FIG. 2

(schematically) a test arrangement;

FIG. 3

a perspective view of a first embodiment of a slit diaphragm according to the invention;

FIG. 4

an exploded view of in FIG. 3 shown slit diaphragm according to the invention;

FIG. 5

a perspective view of the first absorbent member of in FIG. 3 shown slit diaphragm according to the invention;

FIG. 6

a perspective view of a second embodiment of a slit diaphragm according to the invention;

FIG. 7

a perspective view of a third embodiment of a slit diaphragm according to the invention;

FIG. 8

a perspective view of a device according to the invention for beam milling a slit.

FIG. 1 illustrates the Lochkameraprinzip at an imaging device 100. From a radiation source 102, for example, a test body, high-energy radiation 104, in particular X-rays or gamma rays, emitted. The radiation 104 strikes a diaphragm 110, by which it is delimited and directed along an optical axis x according to the hole-camera principle onto an imaging region 106. The imaging region 106 is typically a projection surface on which an image of the test body 102 is created. In the imaging area 106 is a receiving unit 108, which is sensitive to the radiation 104, in particular a detector or a camera.

FIG. 2 shows schematically a test arrangement. A continuously radiating, powerful x-ray tube 112 generates radiation, which is masked out by an all-round shield, here a lead wall 114 with window. The radiation passing through the window of the lead wall 114 is incident on an aluminum plate as scatter filter 116. The actual test object 118 is arranged between the scatter filter 116 and the diaphragm 120 according to the invention, which is integrated in a shielding wall 122 made of lead. In this case, an X-ray film or an image-forming film (English: phosphor imaging plate) in a cassette serves as the detector 124 on the projection surface 126. The invention is not limited to this arrangement. In particular, the invention can also be used for imaging backscattered radiation, for example for radiographic examination of objects for which only one-sided access is possible.

FIG. 3 shows a perspective view of a first embodiment of a slit 50 according to the invention according to claim 3. The slit 50 comprises a first absorption element 52 having a first non-planar outer surface 54 and a second Absorption member 56 having a second non-planar outer surface 58. Between the two non-planar outer surfaces 54 and 58 is a gap 60. The absorption elements have a trapezoidal plan, which widens towards the radiation source; the lateral brackets 62a and 62b have a corresponding complementary shape.

For the description of the first non-planar outer surface 54 is in FIG. 3 drawn a Cartesian coordinate system, whose origin lies at the center of the first non-planar outer surface 54, the x- axis lies in the direction of the optical axis and the γ-axis lies on the central axis through which all generators of the control surface on which the first not -plane outer surface 54 is, run. The imaging area is behind the aperture 50 in the direction of the positive x-axis.

The height h _{1 of} the opening of the gap 60 at the front of the aperture 50 is greater than the height h _{2 of} the opening of the gap 60 at the back of the aperture 50. For example, the height h _{1 can be} 3 mm and the height h ₂ 1 mm , The rear opening of the gap is steeper than the front opening of the gap due to the fan-shaped beam guide. The width d of the front side of a lateral support may for example be 10 to 25 mm.

FIG. 4 shows an exploded view of in FIG. 3 shown slit diaphragm according to the invention. As an example, two generators E ₁ and E _{2 of} the control surface are drawn. The portion of the generatrix E ₂ extending on the first non-planar outer surface 54 is highlighted for clarity. The distance in the y-direction, ie in the direction of the central axis, between the generatrices E ₁ and E ₂ decreases towards the imaging region. In the partial region of the first non-planar outer surface with x <0, the distance between the generatrix of the control surface in the z-direction, and thus in each direction perpendicular to the optical axis, also decreases towards the imaging region.

FIG. 5 shows a perspective view of the first absorbent member of in FIG. 3 shown inventive aperture with exemplary dimensions, for example, the values h ₃ = 14 mm, h ₄ = 16 mm, h ₅ = 30 mm, h ₆ = 13 mm, h ₇ = 17 mm, b ₁ = 13 mm, b ₂ = 50 mm, t = 50 mm and α = 15 ° can assume.

FIG. 6 shows a perspective view of a second embodiment of a slit 70 according to the invention. The slit 70 comprises a first absorption element 72 with a first non-planar outer surface and a second absorption element 76th with a second non-planar outer surface. For clarity, only the gap 80 is shown, not the complementary non-planar outer surfaces forming it, which are close together. In addition, for comparison, a slit 70 'according to the patent DE 10 2005 029 674 B4 drawn with a first absorption element 72 ', a second absorption element 76' and a gap 80 ', wherein both diaphragms have the same central axis and are described in the same Cartesian coordinate system whose γ-axis lies on the common central axis.

As in the case of the slit diaphragm of the first exemplary embodiment, the absorption elements of the slit diaphragm of the second exemplary embodiment have a trapezoidal plan view. The lines of intersection of the gaps with the outer boundary surfaces of the respective slit are shown, namely in each case the two outermost generatrices E ₃ and E ₄ or E ₃ 'and E ₄ ', the opening of the slit on the side of the slit diaphragm, O _1, facing the radiation source or O ₁ ', and the opening of the gap on the imaging region side facing the slit, O ₂ and O ₂ '. The generatrices of the control surface, on which the first non-planar outer surface of the first absorption element of the slit diaphragm of the second embodiment lies, converge in the y-direction, ie in the direction of the central axis. Also, their z-coordinates approach each other in the range x <0, in which the first non-planar outer surface lies. Thus, in this embodiment, on the entire first non-planar outer surface, the distance between the generatrix of the control surface and the imaging region decreases in each direction perpendicular to the optical axis.

In this embodiment, the γ-axis is outside the diaphragm body. As a result, the detector can be arranged in the vicinity of the gamma axis at a small distance from the slit diaphragm on a particularly small area. Such asymmetric design of the visor body has already been in the German patent application with the file number 10 2008 025 109.7-54 disclosed; However, in the present invention, not only the diaphragm body but also the (unlimited) control surface is asymmetrical with respect to the γ-axis.

FIG. 7 shows a perspective view of a third embodiment of a slit 90 according to the invention, in which, as in the German patent application with the file reference 10 2008 025 109.7-54 described in more detail, in addition to the gap 92, a further gap 94 is arranged, the shape of which results from an affine image of the shape of the gap 92. In this embodiment, the affine mapping is a rotation about the central axis y about the angle β. The angle β influences both the intensity distribution in the image field as well as the width of the reproduced image; he can be chosen freely. If required, additional columns can be added. There are no overlaps between the various columns when the central axis y lies outside the slit 90 or, as shown in this embodiment, on the rear interface of the slit 90. In addition to the slit 90, a further diaphragm body 90 'is shown to clarify the beam paths, but this is not part of the slit 90.

FIG. 8 shows a perspective view of an inventive apparatus for beam milling a slit of cube-shaped raw material (semi-finished) with half-milled block. (For clarity, details of the suspension, the drive and the clamping of a blank are not shown.) This device is suitable for manufacturing a slit diaphragm according to claim 3. In this case, a cube-shaped workpiece 10 with both a linearly advancing feed and two simultaneously occurring Spins moved. These three movements are coupled together. In the present embodiment, all three movements are in a fixed linear relationship, so that they can be coupled with a simple mechanical translation. The drawn Cartesian coordinate system is to be understood as a body-fixed on the workpiece 10 related; it corresponds to the in the Figures 3 . 4 and 6 drawn Cartesian coordinate systems.

By means of a motor (not shown), a first threaded shaft 16 is driven, which runs parallel to the γ-axis. The first threaded shaft 16 has a portion 18 which is formed as a worm shaft. By mechanical interaction with the region 18, a holding arm 20 arranged parallel to the z axis is moved in a direction parallel to the γ axis, whereby a second threaded shaft 22 connected to the holding arm 20 and arranged along the γ axis and the workpiece 10 arranged thereon is moved linearly along the γ-axis. Furthermore, the device comprises a third threaded shaft 40, which runs along the z-axis. The rotation of the three threaded shafts 16, 22 and 40 is synchronized, wherein the mechanical transmission via a gear system 24 is accomplished. The gear system 24 consists of three gears (front or bevel gears) 26, 28 and 42, which are mounted on the three threaded shafts 16, 22 and 40, a perpendicular to the γ-axis worm shaft 30 and a further threaded shaft 44, the one area 46, which is formed as a screw shaft. On the worm shaft 30, a further gear 32 is mounted, and on the threaded shaft 44, a further gear 38 is mounted. The worm shaft 30 drives the gear 28 on the second threaded shaft 22, while also a transmission of Rotary movement between the mutually perpendicular gears 26, 32 takes place. In this embodiment, a reduction of the speed of 2: 1 takes place at this point. As a result, the rotational movement is transmitted to the workpiece 10, which is arranged on the second threaded shaft 22 by means of a holder 36a, 36b. Due to the concurrent linear down movement (along the γ-axis), the axis of the second threaded shaft 22 must be telescopically connected to the support 36a, 36b of the workpiece so as to transmit the rotation, the downward movement directed along the γ-axis but at the same time not hindered. In order to sweep an opening angle of γ = 60 °, while the workpiece 10 is moved downwards over the distance d, in this arrangement the gear wheel 28 must have a radius r of 3d / 2π, ie of around d / 2.

Further, the threaded shaft 44 drives the gear 42 on the third threaded shaft 40 via the formed as a screw shaft portion 46, while also a transmission of the rotational movement between the two gears 26, 38 takes place. The third threaded shaft 40 is fixed in space, and the entire device including the first and second threaded shaft is mounted so that it rotates upon rotation of the third threaded shaft 40 about this. Since the drawn coordinate system is to be understood as being body-fixed relative to the workpiece 10, the first threaded shaft 16 and the second threaded shaft 22 are still parallel to the γ-axis after rotation about the third threaded shaft 40.

During the rotational movement of the workpiece 10 about the second screw shaft 22 and the third screw shaft 40 and the simultaneous translational movement along the γ-axis, a slit is cut into the workpiece 10 by a cutting jet 12. The cutting beam 12 extends in the illustrated position of the workpiece parallel to the x-axis and keeps this direction during the entire milling process at room, so does not participate in the rotation of the workpiece 10 and related to this body-fixed coordinate system. He follows the beam path through the produced aperture.

In the illustration, the workpiece 10 is symmetrically inserted into the holder 36 a, 36 b to the in FIG. 3 illustrated inventive slit diaphragm of the first embodiment produce. To the in FIG. 6 shown slit diaphragm of the second embodiment and in FIG. 7 shown slit diaphragm of the third embodiment, in which the central axis extends outside the diaphragm body to produce, the workpiece 10 is asymmetrical use, so that through the second threaded shaft 22 extending axis of rotation outside the diaphragm body comes to rest. In order to produce a slit diaphragm having a plurality of columns as in the third embodiment, a plurality of milling operations may be performed, wherein the workpiece 10 is to be inserted in a respective position corresponding to the gap to be milled.

The workpiece 10 consists of a suitable collimator material, for example Densimet as mechanically processable tungsten alloy. For X-rays, especially backscattered X-rays, lead is in principle also suitable, but difficult to process mechanically. Conceivable would be the production in the casting process. A mold could be made with a blank of another suitable material.

The device according to the invention and the method according to the invention are suitable for producing a slit diaphragm according to the invention, using the example of the device according to claim 9, in particular according to claim 10, the method according to claim 14, in particular according to claim 15, and the slit diaphragm according to claim 2, in particular according to Claim 3, shown.

The beam paths cut by the device according to claim 9 and the method according to claim 14 are described in the above-introduced body-fixed coordinate system, ie the Cartesian coordinate system firmly connected to the workpiece. The origin of the coordinate system lies in the common intersection of the two axes of rotation and the cutting line of the cutting tool, and the y- axis points along the first axis of rotation. The x- axis and the z- axis lie so that they are in the in FIG. 8 represented, as a starting position considered position of the workpiece along the cutting line of the cutting tool or along the second axis of rotation. The line equation of the cutting line of the cutting tool will now be described in this coordinate system. In the starting position it has the form $$\overrightarrow{r}=\left(0,0,0\right)+\mathrm{<figure-callout\; id="1"\; label="\lambda "\; filenames="imgf0005.png"\; state="\{\{state\}\}">\lambda </figure-callout>}\left(1,0,0\right)\mathrm{,}$$

Since the first axis of rotation rotates with the workpiece and thus has a fixed direction in the body-fixed coordinate system, while the second axis of rotation changes its direction in the body-fixed coordinate system when rotating about the first axis of rotation, the rotation about the second axis of rotation must first be applied and then only the rotation about the body-fixed first axis of rotation and the displacement along the same. A rotation by an angle θ results in the initial position in the z-direction lying second axis of rotation $$\overrightarrow{r}\mathrm{=}\left(\mathrm{0},\mathrm{0},\mathrm{0}\right)\mathrm{+}\mathrm{\lambda }\left(\cos ,\mathrm{sin\; \theta },\mathrm{0}\right)\mathrm{,}$$

und eine Verschiebung um eine Strecke y₀ entlang der körperfest in γ-Richtung liegenden ersten Drehachse führt schließlich auf $$\overrightarrow{r}\mathrm{=}\left(\mathrm{0},y_0,\mathrm{0}\right)\mathrm{+}\mathrm{\lambda }\left(\mathrm{cos\vartheta \; cos\varphi },\mathrm{sin\; \vartheta },\mathrm{cos\vartheta \; sin\; \varphi }\right)\mathrm{.}$$

A rotation by an angle φ around the body fixed in γ-direction first rotation axis then yields $$\overrightarrow{r}\mathrm{=}\left(\mathrm{0},\mathrm{0},\mathrm{0}\right)\mathrm{+}\mathrm{\lambda }\left(\mathrm{cos\theta \; cos\phi },\mathrm{sin\; \theta },\mathrm{cos\theta \; sin\; \phi }\right).$$

and a displacement by a distance y ₀ along the first axis of rotation lying body-fixed in the γ-direction finally leads $$\overrightarrow{r}\mathrm{=}\left(\mathrm{0},y_0,\mathrm{0}\right)\mathrm{+}\mathrm{\lambda }\left(\mathrm{cos\theta \; cos\phi },\mathrm{sin\; \theta },\mathrm{cos\theta \; sin\; \phi }\right)\mathrm{,}$$

The slit diaphragm produced thus has a central axis in the y- axis, through which all cutting lines run, and thus has the additional feature of claim 2. If the two rotational movements and the translational motion are coupled linearly, there is a distance between the distance y ₀ , which indicates the position of the intersection of the section line with the central axis, and the angles θ and φ, which are the polar angles of the direction vector (cosθ cosφ, sinθ, cosθ sinφ ) with respect to the γ-axis are a linear relationship. Thus, in this case, the slit diaphragm produced has the additional feature of claim 3. The direction vector of the section line forms the angle π / 2-θ with the γ-axis. Since this angle is linearly related to the γ-coordinate of the point of intersection with the central axis, (with a suitable choice of the direction of rotation) the distance in the γ-direction of the cutting lines decreases towards the imaging region. Thus, the slit diaphragm thus produced also has the characterizing part of claim 1.

The Gaussian curvature of the control surface of the slit diaphragm produced in this way results in a break with the counter - φ̇cos ² θ, where φ̇ is the constant rate at which the angle φ changes linearly along the central axis. The angles υ = ± π / 2, at which this curvature disappears, are not used, since the beam path in this case run along the central axis and would not lead in the direction of the imaging area. With a non-zero rate of change φ̇ of the angle φ, the Gaussian curvature does not vanish anywhere in the subarea of the ruled surface used for imaging.

LIST OF REFERENCE NUMBERS

10

workpiece

12

cutting tool

16

first thread shaft

18

worm shaft

20

holding arm

22

second threaded shaft

24

gear system

26

gear

28

gear

30

worm shaft

32

gear

34

pipe

36a, b

bracket

38

gear

40

third thread shaft

42

gear

44

threaded shaft

46

worm shaft

50

slit

52

first absorption element

54

first non-flat outer surface

56

second absorption element

58

second non-planar outer surface

60

gap

62a, b

brackets

70, 70 '

slit

72, 72 '

first absorption element

76, 76 '

second absorption element

80, 80 '

gap

90

slit

90 '

further visor body

92

gap

94

another gap

100

Imaging device

102

radiation source

104

radiation

106

imaging area

108

receiver unit

110

cover

112

X-ray tube

114

lead wall

116

Light diffuser

118

test object

120

cover

122

shielding

124

detector

126

projection

E ₁ , E ₂

generating

E ₃ , E ₄ , E ₃ ', E ₄ '

utmost generators

O ₁ , O ₂ , O ₁ ', O ₂ '

Opening of the gap

Claims (15)

1. Slit aperture (50, 70, 90), particularly for an imaging apparatus (100), which is suitable for delimiting radiation (104), more particularly high-energy radiation, emitted from a radiation source (102) and for directing it, according to the pinhole camera principle, onto an imaging region (106) along an optical axis (x),
   wherein the slit aperture (50, 70, 90) comprises a first absorption element (52, 72), which has a first non-planar external face (54), of which at least one part lies on a ruled surface, the Gaussian curvature of which does not vanish anywhere in the part,
   wherein the slit aperture (50, 70, 90) comprises a second absorption element (56, 76), which has a second non-planar external face (58), the surface contour of which is formed at least in part complementary to the non-planar external face (54) of the first absorption element (52, 72), and wherein the two absorption elements (52, 72; 56, 76) are or can be positioned such that there is a gap (60, 80, 92) between the two non-planar external faces (54, 58),
   characterized in that
   the distance in one direction (y) perpendicular to the optical axis (x) between the generatrices of the ruled surface reduces towards the imaging region (106).
2. Slit aperture (50, 70, 90) according to Claim 1,
   characterized in that
   there is a central axis (y) that intersects every generatrix of the ruled surface.
3. Slit aperture (50, 70, 90) according to Claim 2,
   characterized in that
   the polar angles of the directional vectors of the generatrices of the ruled surface are, in respect of the central axis (y), linearly related to the intersection of the generatrices of the ruled surface with the central axis (y).
4. Slit aperture (70, 90) according to Claim 2 or 3,
   characterized in that
   the central axis (y) is situated outside of the aperture frame.
5. Slit aperture (50, 70) according to one of the preceding claims,
   characterized in that
   the absorption elements (52, 72; 56, 76) have a trapezoidal outline, which expands towards the radiation source (102).
6. Slit aperture (50) according to one of the preceding claims,
   characterized in that
   the opening (h₁) of the gap (60) on the side of the slit aperture (50) facing the radiation source (102) is greater than the opening (h₂) of the gap (60) on the side of the slit aperture (50) facing the imaging region (106).
7. Slit aperture (90) according to one of the preceding claims,
   characterized in that
   the slit aperture (90), in addition to the one gap (92), comprises at least one further gap (94), the shape of which substantially emerges from an affine transformation of the shape of the one gap (92).
8. Device for producing a slit aperture (50, 70, 90), comprising
   a cutting tool (12) that is suitable for cutting along a straight line, and
   means that are suitable for bringing about a relative movement between the cutting tool (12) and a workpiece (10) such that the cutting tool (12) cuts the workpiece (10) along a line that corresponds to a beam path in the slit aperture (50, 70, 90) to be produced,
   wherein
   the cutting tool (12) is suitable for cutting along a first direction (x);
   the means comprise a holding element (36a, 36b) onto which a workpiece (10) can be attached and which is mounted such that it can rotate about a first rotational axis (22);
   the means are suitable for bringing about a first rotational movement of the holding element (36) about the first rotational axis (22) and, simultaneously, bringing about a translational movement of the holding element (36) along the first rotational axis (22); and
   the first rotational movement and the translational movement of the holding element (36) are coupled,
   characterized in that
   the means are furthermore suitable for bringing about a second rotational movement of the holding element (36) and of the first rotational axis (22) about a second rotational axis (40), simultaneously with the first rotational movement and the translational movement, and
   the second rotational movement and the translational movement of the holding element (36) are coupled.
9. Device according to Claim 8,
   characterized in that
   the second rotational axis (40) runs along a second direction (z) that is perpendicular to the cutting direction (x) of the cutting tool (12) and perpendicular to the first rotational axis (22) and
   the first rotational axis (22), the second rotational axis (40) and the line along which the cutting tool (12) cuts, have a common point of intersection.
10. Device according to Claim 8 or 9,
    characterized in that
    the translational movement and the first rotational movement are coupled linearly and the translational movement and the second rotational movement are coupled linearly.
11. Device according to one of Claims 8 to 10,
    characterized in that
    the means comprise a first (16), a second (22) and a third (40) threaded shaft,
    wherein the first threaded shaft (16) runs parallel to the first rotational axis (22), the second threaded shaft (22) lies on the first rotational axis (22) and the third threaded shaft (40) lies on the second rotational axis (40) and wherein a rotational movement of the three threaded shafts (16, 22, 40) is coupled by a gearwheel system (24).
12. Device according to Claim 11,
    characterized in that
    the first threaded shaft (16) comprises a region (18), which is embodied as a worm drive, by means of which a holding arm (20), to which the second threaded shaft (22) is connected, can be moved along the first rotational axis (22).
13. Method for producing a slit aperture,
    wherein a relative movement between a cutting tool (12), which is suitable for cutting along a straight line, and a workpiece (10) is carried out such that the cutting tool (12) cuts the workpiece (10) along a line that corresponds to a beam path in the slit aperture to be produced;
    the workpiece (10) is cut along an unchangeable first direction (x);
    a first rotational movement of the workpiece (10) about a first rotational axis (22) and, simultaneously, a translational movement of the workpiece (10) along the first rotational axis (22) are carried out; and
    the first rotational movement and the translational movement of the workpiece (10) are coupled,
    characterized in that
    a second rotational movement of the workpiece (10) and of the first rotational axis (22) about a second rotational axis (40) is carried out simultaneously with the first rotational movement and the translational movement and
    the second rotational movement and the translational movement of the workpiece (10) are coupled.
14. Method according to Claim 13,
    characterized in that
    the second rotational axis (40) runs along a second direction (z) that is perpendicular to the cutting direction (x) of the cutting tool (12) and perpendicular to the first rotational axis (22) and
    the first rotational axis (22), the second rotational axis (40) and the line along which the cutting tool (12) cuts, have a common point of intersection.
15. Method according to Claim 13 or 14,
    characterized in that
    the translational movement and the first rotational movement are coupled linearly and the translational movement and the second rotational movement are coupled linearly.

Images