WO2011069770A1

WO2011069770A1 - Asymmetrical slot aperture and device and method for the production thereof

Info

Publication number: WO2011069770A1
Application number: PCT/EP2010/067273
Authority: WO
Inventors: Kurt Osterloh; Uwe Zscherpel; Uwe Ewert
Original assignee: BAM Bundesanstalt für Materialforschung und -prüfung
Priority date: 2009-12-08
Filing date: 2010-11-11
Publication date: 2011-06-16
Also published as: ATE545935T1; EP2333786A1; EP2333786B1

Abstract

The invention relates to a slot aperture (50, 70, 90), in particular for an imaging apparatus (100), which is suited for limiting in particular highly energetic radiation (104) originating from a radiation source (102) and directing said radiation along an optical axis (x) according to the pinhole camera principle to an imaging region (106), wherein the slot aperture (50, 70, 90) comprises a first absorption element (52, 72) which has a first non-even outer surface (54), of which at least one partial region lies on a ruled surface, the gaussian curvature thereof disappearing nowhere in the partial region, wherein the slot aperture (50, 70, 90) comprises a second absorption element (56, 76) having a second non-level outer surface (58), the surface contour thereof being formed at least partially complimentarily to the non-level outer surface (54) of the first absorption element (52, 72), and wherein the two absorption elements (52, 72; 56, 76) are positioned or can be positioned so that there is a gap (60, 80, 92) between the two non-level outer surfaces (54, 58). The distance in a direction (y) perpendicular to the optical axis (x) between the generatrixes of the ruled surface reduces toward the imaging region (106). The invention further relates to a device and method for producing a slot aperture, wherein a first rotational movement, a second rotational movement and a translational movement are coupled to each other.

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. Often the problem arises to determine 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 20keV) 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, there are also those which generate these by X-ray or gamma backscattering. 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 from the lower portion are imaged onto 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.

In the case of high-energy radiation, the problem arises that because of their high penetration capacity, 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. For this reason, the aperture in the apertured cameras is often shaped like a trumpet with the narrow spot as source of radiation 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.

Patent DE 10 2005 029 674 B4 discloses a diaphragm 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 comprising 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 typically has a weight of 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 allows a more compact camera structure and a higher intensity on the imaging surface and thus a shorter exposure time over the aperture disclosed in the patent DE 10 2005 029 674 B4. 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 which at least partially absorb the radiation, the material being in the form of a separate insert or a coating applied to at least one of the non-planar surfaces may be present.

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 principal curvatures in the point; the principal curvatures of the area in a point are the minimum value and the maximum value of the curvatures of all curves resulting from intersecting the surface with a plane containing the surface normal on the point. An example of a rule surface is the surface used in the patent DE 10 2005 029 674 B4, 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, / (y ₀ )), each value of the parameter y ₀ corresponding to exactly one generator. In particular, the surface which is described by the function z (x, y) = C * y * x + n disclosed in the patent DE 10 2005 029 674 B4 is characterized by

Straight lines are generated with the straight line equations r = (0, y ₀ , n) + λ (1.0, Cy ₀ ). Your Gaussian

Curvature in point (x, y, z (x, y)) is

and is therefore different from zero over the entire area.

In order to determine which ruled surfaces could be suitable for a further development of the diaphragm disclosed in the patent specification DE 10 2005 029 674 B4, the directions in which radiation beams can enter unimpeded or almost unhindered are considered. The generators of the control surface provide a one-parameter set of directions along which rays of light can enter unimpeded. To create a two-dimensional image, however, a two-dimensional multiplicity of radiation beams must pass through the diaphragm. 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 at a point disappears if and only if 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 patent specification DD 240 091 A1 and the published patent application DE 40 00 507 A1, panels for high-energy radiation are known in which partial areas of control surfaces are used to form a gap, specifically 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.

Fan-shaped beam guidance was also used in the focal point-oriented roller shutter disclosed in the published patent application DE 10 2005 048 519 A1. 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 only obtained by turning the roller blind and scanning the object line by line.

Like the aperture disclosed in the patent specification DE 10 2005 029 674 B4, the slit diaphragm according to the invention is suitable for limiting, in particular high-energy, radiation emanating from a radiation source and directing it to an imaging region along an optical axis according to the hole-camera principle, and comprises a first absorption element, which has a first non-planar outer surface, of which at least a partial region lies on a control surface whose Gaussian curvature does not disappear anywhere in the partial region, 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 plane outer surface of the first absorbent member formed 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 one

Partial area of the first non-planar outer surface of the distance between the generatrix of the control surface is reduced to the imaging area 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. This simplifies the mapping rule and, given a suitable position of the visor 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 generators 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; ie, the feature that the polar angles of the direction vectors of the generators of the control surface with respect to the central axis in not constant linear relationship with the

Intersection point of the generator of the control surface with the central axis are, leads to a slit diaphragm according to the invention, without the additional requirement that the Gaussian curvature of the control surface does not disappear anywhere.

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 a mapping of the three-dimensional space onto itself, which maps each straight line to a straight line. European Patent Application EP 2 062 705 A1 discloses an apparatus and a method for producing slit diaphragms, with which the slit diaphragm disclosed in the patent DE 10 2005 029 674 B4 and the focal point-oriented roller diaphragm disclosed in the published patent application DE 10 2005 048 519 A1 are disclosed let produce. 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 device disclosed in European patent application EP 2 062 705 A1, the device for producing a slit diaphragm according to the invention comprises a cutting tool which is suitable for cutting along a straight line and means which are suitable for relative movement between the cutting tool and one To cause a workpiece such that the cutting tool cuts the workpiece along a line corresponding 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 holding 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 holder and to guide the tool, but conversely to move it movably 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 threaded shaft may include an area formed as a worm shaft through which a holding arm, to which the second screw shaft is connected, is movable along the first axis of rotation.

As in the method disclosed 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 cutting the workpiece along a line corresponding to a beam path in the slit diaphragm to be produced, cutting the workpiece along a fixed first direction, performing a first rotational movement of the workpiece about a first axis of rotation and simultaneously translating the workpiece along the first axis of rotation; Rotational movement and the translational movement of the workpiece are coupled. This teaching is further developed by the present invention in that, simultaneously with the first rotational movement and the translational movement, a second rotational movement of the workpiece and the first rotational axis about a second rotational axis is performed 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 coupled linearly and the translation 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.

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

Figure 1 is an imaging device with a diaphragm;

Figure 2 (schematically) a test arrangement;

Figure 3 is a perspective view of a first embodiment of a slit diaphragm according to the invention; an exploded view of the slit diaphragm shown in Figure 3 according to the invention; Figure 5 is a perspective view of the first absorption element of the slit diaphragm shown according to the invention;

Figure 6 is a perspective view of a second embodiment of a

slit diaphragm according to the invention;

Figure 7 is a perspective view of a third embodiment of a slit diaphragm according to the invention; Figure 8 is a perspective view of a device according to the invention for

Beam milling of a slit diaphragm.

FIG. 1 illustrates the hole camera principle on an imaging device 100.

From a radiation source 102, for example a test body, high-energy radiation 104, in particular X-ray or gamma radiation, is emitted. The radiation

104 strikes a diaphragm 1 10, through which they are limited and along an optical

Axis x is directed to an imaging area 106 according to the Lochkameraprinzip.

The imaging area 106 is typically a projection surface on which a

Image of the test body 102 is generated. In the imaging region 106 is a receiving unit 108, which is sensitive to the radiation 104, in particular a

Detector or a camera.

FIG. 2 schematically shows a test arrangement. A continuously radiating, powerful X-ray tube 1 12 generates radiation, which is hidden by an all-round shield, here a lead wall 1 14 with window. The radiation passing through the window of the lead wall 1 14 falls on an aluminum plate as a stray filter 1 16. The actual test object 1 18 is disposed between the stray filter 1 16 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 exemplary embodiment of a slotted diaphragm 50 according to the invention. The slotted diaphragm 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 describing the first non-planar outer surface 54, a Cartesian coordinate system is shown in FIG. 3 whose origin lies at the center of the first non-planar outer surface 54, whose x-axis lies in the direction of the optical axis and whose y-axis on the Central axis lies through which all generators of the control surface, on which the first non-planar outer surface 54 is located run. The imaging area is behind the aperture 50 in the direction of the positive x-axis.

The height h-ι 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 hi 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 the slit diaphragm according to the invention shown in FIG. As an example, two generators E- ₁ and E _{2 of} the control surface are shown. 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 generators E- ₁ and E ₂ decreases towards the imaging area. 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 absorption element of the panel according to the invention shown in FIG. 3 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, bi = 13 mm, b ₂ = 50 mm, t = 50 mm and oc = 15 °. 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 having a first non-planar outer surface and a second absorption element 76 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 is drawn with a first absorption element 72', a second absorption element 76 'and a gap 80', both diaphragms having the same central axis and being described in the same Cartesian coordinate system, whose y-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 slotted diaphragm of the second exemplary embodiment have a trapezoidal basic crack. The lines of intersection of the gaps with the outer boundary surfaces of the respective slit are shown, namely 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 facing the radiation source, Oi or OY, and the opening of the gap on the side facing the imaging area of the slit, 0 ₂ or 0 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. In this exemplary embodiment, the total non-planar outer surface of the first non-planar outer surface is thus reduced

Distance between the generators of the control surface to the imaging area in each direction perpendicular to the optical axis.

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

FIG. 7 shows a perspective view of a third exemplary embodiment of a slit 90 according to the invention, in which, as described in more detail in German Patent Application No. 10 2008 025 109.7-54, in addition to the slit 92, a further slit 94 is arranged, the shape of which an affine mapping emerges from 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 a device according to the invention for the jet milling of a slit of cubic raw material (semi-finished product) with a 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 according to claim 3. Here, a cube-shaped workpiece 10 takes place both with a linear advancing feed and two simultaneously - denden rotations 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 drawn in Figures 3, 4 and 6 Cartesian coordinate systems.

By means of a motor (not shown), a first threaded shaft 16 is driven, which runs parallel to the 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 support arm 20 arranged parallel to the z-axis is moved in a direction parallel to the axis, whereby a second threaded shaft 22 arranged along the y-axis and the workpiece 10 arranged thereon are linear with the support arm 20 is moved along the y-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 screw shaft 30 arranged perpendicular to the y-axis and a further threaded shaft 44 which has a region 46 , which is formed as a worm 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 downward movement (along the y-axis), the axis of the second threaded shaft 22 must be telescopically connected to the workpiece holder 36a, 36b with a tube 34 so as to transmit the rotation, the downward along the axis simultaneously but 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 gearwheel 28 must have a radius r of 3ό / 2ττ, 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 to the workpiece 10, the first threaded shaft 16 and the second threaded shaft 22 are still parallel to the y-axis after rotation about the third threaded shaft 40.

During the rotational movement of the workpiece 10 about the second threaded shaft 22 and the third threaded shaft 40 and the simultaneous translational movement along the y-axis, a slot 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 aperture to be produced.

In the illustration, the workpiece 10 is inserted symmetrically into the holder 36a, 36b to produce the slit diaphragm of the first embodiment according to the invention shown in FIG. In order to produce the slit diaphragm of the second exemplary embodiment shown in FIG. 6 and the slit diaphragm of the third exemplary embodiment in which the central axis runs outside the diaphragm body, the workpiece 10 is to be inserted asymmetrically, so that the slits through the second 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 Denimet as a 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 intersected by the device according to claim 9 and the method according to claim 14 are fixed in the above body-fixed, i. described with the workpiece firmly connected Cartesian coordinate system. 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 in such a way that they lie in the position of the workpiece viewed in FIG. 8 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 initial position it has the form r = (0,0,0) + λ (1,0,0).

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 ΰ results in the initial position in the z-direction lying second axis of rotation r = (0,0,0) + λ (οο8-θ, 8ίηθ, 0).

A rotation through an angle φ about the first axis of rotation lying body-fixed in the y-direction then yields r = (0,0,0) + λ

οοβφ, βίη'θ, οοβ'θ βίη φ), and a shift by a distance y ₀ along the first axis of rotation fixed in the y-direction finally leads to r = (0, 7 ₀ , 0) + λ (οο 8ΐ3-cosq ^ sini ^ cosiS-sin cp).

The slit diaphragm produced thus has a central axis in the y-axis through which all cutting lines extend, and thus has the additional feature of claim 2. If the two rotational movements and the translational motion are coupled linearly, then there is the distance y ₀ , which indicates the position of the intersection of the section line with the central axis, and the angles and φ, which the polar angle of

Direction vector (cosi3-cos (p, sini3-, cosi3 'sincp) with respect to the y-axis are a linear relationship.) In this case, the produced slit has the additional feature of claim 3. The direction vector of the section line forms with the y Since this angle is linearly related to the y-coordinate of the point of intersection with the central axis, the distance in the y-direction of the intersection lines decreases (with a suitable choice of direction of rotation) to the imaging region the slit diaphragm produced in this way 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 - (cos ² i3-, where φ is the constant rate at which the angle φ changes linearly along the central axis.) The angles = ± π / 2 where this curvature disappears are not used because the beam path in this case would be along the central axis and would not lead in the direction of the imaging area, so if the rate of change φ of the angle φ is nonzero then the Gaussian curvature does not disappear anywhere in the image used Subarea of the ruled area. 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 threaded shaft

42 gear

44 threaded shaft

46 worm shaft

50 slit diaphragm

52 first absorption element

54 first non-flat outer surface

56 second absorption element

58 second non-flat outer surface

60 gap

62a, b brackets

70, 70 'slit diaphragm

72, 72 'first absorption element

76, 76 'second absorption element

80, 80 'gap

90 slit diaphragm

90 'further visor body

92 gap

94 further gap

100 imaging device

102 radiation source 104 radiation

106 imaging area

108 receiving unit

1 10 aperture

1 12 x-ray tube

1 14 lead wall

1 16 scatter filter

1 18 test object

120 aperture

122 shielding wall

124 detector

126 projection surface

Egg, E ₂ generators

E ₃ , E ₄ , E ₃ ', E ₄ ' extreme generatrix

Oi, 0 ₂ , Οι \ 0 ₂ 'Opening of the gap

Claims

Slit diaphragm (50, 70, 90), in particular for an imaging device (100), which is suitable, from a radiation source (102) emanating, in particular high-energy radiation (104) to limit and along an optical axis (x) on the Lochkameraprinzip directed to an imaging area (106), wherein the slit (50, 70, 90) comprises a first absorption element (52, 72) having a first non-planar outer surface (54), at least a portion of which lies on a control surface whose Gaussian curvature does not disappear anywhere in the subarea,

wherein the slit (50, 70, 90) comprises a second absorbent member (56, 76) having a second non-planar outer surface (58) whose surface contour is at least partially complementary to the non-planar outer surface (54) of the first absorbent member (54). 52, 72), and

the two absorption elements (52, 72; 56, 76) being positioned or positionable such that a gap (60, 80, 92) is present between the two non-planar outer surfaces (54, 58),

characterized in that

the distance in a direction (y) perpendicular to the optical axis (x) between the generatrix of the control surface decreases toward the imaging region (106).

Slit diaphragm (50, 70, 90) according to claim 1,

characterized in that

a central axis (y) exists which intersects each of the generators of the control surface.

Slit diaphragm (50, 70, 90) according to claim 2,

characterized in that

the polar angles of the direction vectors of the generatrix of the control surface with respect to the central axis (y) are linearly related to the intersection of the generatrix of the control surface with the central axis (y).

Slit diaphragm (70, 90) according to claim 2 or 3,

characterized in that

the central axis (y) lies outside the diaphragm body.

Slit diaphragm (50, 70) according to one of the preceding claims,

characterized in that the absorption elements (52, 72; 56, 76) have a trapezoidal plan which widens towards the radiation source (102).

Slit diaphragm (50) according to one of the preceding claims,

characterized in that

the opening (s) of the gap (60) on the side of the slit (50) facing the radiation source (102) is larger than the opening (h ₂ ) of the slit (60) on the side of the slit (FIG. 50).

Slit diaphragm (90) according to one of the preceding claims,

characterized in that

the slit (90) comprises, in addition to the one slit (92), at least one further slit (94), the shape of which results essentially from an affine image of the shape of the one slit (92).

Apparatus for manufacturing a slit (50, 70, 90) comprising

a cutting tool (12) adapted to cut along a straight line, and

Means adapted to effect relative movement between the cutting tool (12) and a workpiece (10) such that the cutting tool (12) intersects the workpiece (10) along a line corresponding to a beam path in the slit aperture (50 , 70, 90),

in which

the cutting tool (12) is adapted to cut along a first direction (x);

the means comprise a holding element (36a, 36b) on which a workpiece (10) can be fastened and which is rotatably mounted about a first axis of rotation (22); the means are adapted to cause a first rotational movement of the holding element (36) about the first axis of rotation (22) and at the same time a translational movement of the holding element (36) along the first axis of rotation (22); and

the first rotational movement and the translatory movement of the holding element (36) are coupled,

characterized in that

the means are further adapted to cause a second rotational movement of the holding element (36) and the first rotation axis (22) about a second rotation axis (40) simultaneously with the first rotational movement and the translational movement, and the second rotational movement and the translational movement of the retaining element (36) are coupled.

Device according to claim 8,

characterized in that

the second axis of rotation (40) along a second direction (z) perpendicular to

Cutting direction (x) of the cutting tool (12) and perpendicular to the first axis of rotation (22) extends and

the first axis of rotation (22), the second axis of rotation (40) and the line along which the cutting tool (12) intersects have a common point of intersection.

Device according to claim 8 or 9,

characterized in that

the translational movement and the first rotational movement are linearly coupled and

the translational movement and the second rotational movement are linearly coupled.

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) is parallel to the first axis of rotation (22), the second threaded shaft (22) lies on the first axis of rotation (22), and the third threaded shaft (40) lies on the second axis of rotation (40) and wherein a rotational movement the three threaded shafts (16, 22, 40) are coupled by a gear system (24).

Device according to claim 1 1,

characterized in that

the first screw shaft (16) comprises a portion (18) formed as a screw shaft through which a support arm (20) to which the second screw shaft (22) is connected is movable along the first rotation axis (22).

Method for producing a slit diaphragm,

wherein relative movement is performed between a cutting tool (12) adapted to cut along a straight line and a workpiece (10) such that the cutting tool (12) passes along the workpiece (10) a line corresponding to an optical path in the slit diaphragm to be produced;

the workpiece (10) is cut along a fixed first direction (x);

a first rotational movement of the workpiece (10) about a first axis of rotation (22) and simultaneously a translational movement of the workpiece (10) along the first axis of rotation (22) is carried out; and

the first rotational movement and the translatory movement of the workpiece (10) are coupled,

characterized in that

a second rotational movement of the workpiece (10) and the first axis of rotation (22) about a second axis of rotation (40) is performed 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. The method according to claim 13,

characterized in that

the second axis of rotation (40) extends along a second direction (z) perpendicular to the cutting direction (x) of the cutting tool (12) and perpendicular to the first axis of rotation (22) and

the first axis of rotation (22), the second axis of rotation (40) and the line along which the cutting tool (12) intersects have a common point of intersection. 15. The method according to claim 13 or 14,

characterized in that

the translational movement and the first rotational movement are coupled linearly and