Collimator assembly for x-ray tube

Abstract

The invention relates to a collimator assembly for an X-ray tube. The collimator assembly has a near-focus shading assembly with a plurality of near-focus shades and a far-focus shading assembly with a plurality of far-focus shades. The light shield close to the focus can be adjusted between a maximum open position and a maximum closed position by means of a number of first drivers, so that the light shield close to the focus forms a large light shield opening close to the focus in the maximum open position and forms a small light shield opening close to the focus in the maximum closed position. The light shield remote from the focus can be adjusted between a maximum open position and a maximum closed position by means of a number of second drives, such that the light shield remote from the focus forms a large light shield opening remote from the focus in the maximum open position and a small light shield opening remote from the focus in the maximum closed position. The first driver and the second driver are different drivers from each other. By means of one of the first drives, the filter plate can be moved onto a large shade opening close to the focal point in the maximum open position of the shade close to the focal point.

Description

TECHNICAL FIELD

[0001] The invention relates to a collimator assembly for an X-ray tube,

[0002] - wherein the collimator assembly has a near-focus diaphragm assembly with a plurality of near-focus diaphragms and a far-from-focus diaphragm assembly with a plurality of far-from-focus diaphragms,

[0003] - wherein the near-focus diaphragms are adjustable by means of a number of first drives between a maximum open position and a maximum closed position, such that the near-focus diaphragms form a large near-focus diaphragm opening in the maximum open position and a small near-focus diaphragm opening in the maximum closed position,

[0004] - wherein the far-from-focus diaphragms are adjustable by means of a number of second drives between a maximum open position and a maximum closed position, such that the far-from-focus diaphragms form a large far-from-focus diaphragm opening in the maximum open position and a small far-from-focus diaphragm opening in the maximum closed position. BACKGROUND

[0005] Such a collimator assembly is known. In this collimator assembly, the second drives are identical to the first drives. The first drives usually act directly on the far-from-focus diaphragms and via additional kinematics on the near-focus diaphragms.

[0006] The collimator assembly, which is equally applicable in the prior art and in the context of the invention, is more or less directly post-positioned in the light path from the X-ray source to the X-ray detector. In particular, the collimator assembly is arranged between the X-ray source and the examination object, usually a person. By means of the diaphragm assemblies of the collimator assembly, the light path from the X-ray source to the X-ray detector is restricted in order to subject the examination object to ionizing X-ray radiation only in the required range and no longer beyond it.

[0007] Depending on the specific mode of operation of the X-ray assembly, different filter plates, usually made of copper, can also be introduced into the light path between the near-focus diaphragm assembly and the far-from-focus diaphragm assembly. These filter plates serve for beam hardening. These filter plates usually have a relatively small thickness, for example a thickness of 0.1 mm, 0.2 mm and 0.3 mm. The filter plates are arranged on a rotatable element in analogy to different objectives of a microscope, such that one of the filter plates is introduced into the light path or not, as required.

[0008] X-ray detectors need to be calibrated from time to time. It can be necessary, for example, to carry out a calibration of the X-ray detector once a year. In order to calibrate the X-ray detector, a thicker filter plate is introduced into the beam path in the region of the collimator assembly. The filter plate can have a thickness of 0.6 mm or 2.1 mm, for example.

[0009] It is theoretically conceivable to arrange the filter plate on a rotatable element as well. This would result, however, in the rotatable element and thus also the collimator assembly as a whole having to be constructed very voluminously. This approach is therefore not pursued in practice. Instead, the prior art collimator assemblies have a receiving rail on the side facing away from the light-shielding assembly close to the focal point in the region of the light-shielding assembly remote from the focal point, into which a thicker filter plate can be manually moved. Due to the enlargement of the radiation cross section on the path from the X-ray source to the light-shielding assembly remote from the focal point, the thicker filter plate is relatively large-area and heavy.

[0010] The calibration of the X-ray detector is carried out in the prior art by a service technician. The service technician moves to the respective X-ray device, moves the thicker filter plate into the receiving rail and then initiates the calibration sequence. SUMMARY

[0011] It is the task of the present application to provide the possibility with the aid of which a permanent arrangement of a thicker filter plate in a collimator assembly can also be achieved, wherein it should be possible to move the thicker filter plate into and out of the beam path in a simple manner as required.

[0012] This task is solved by a collimator assembly according to the application. Advantageous design variants of the collimator assembly are the subject matter of the description.

[0013] According to the application, a collimator assembly of the type mentioned at the outset is designed in such a way that

[0014] - the first drives and the second drives are different drives from one another, and

[0015] - with the aid of one of the first drives, the filter plate can be moved onto the large light-shielding close-to-focal-point opening in the maximum opening position of the light-shielding close to the focal point.

[0016] The use of mutually different drives for adjusting the near-focus and the far- focus diaphragms, although requiring more drives than in the prior art, on the contrary enables the use of smaller and weaker drives. However, first the kinematics required in the prior art can be dispensed with, so that one and the same drive can act not only on the near-focus diaphragm but also on the far- focus diaphragm. Since the first and second drives are position-adjusting, a coordinated adjustment of the near-focus and the far-focus diaphragms can be easily achieved. By using one of the first drives not only for adjusting the near-focus diaphragm but also for moving the filter plate, moreover, no own drive is required for moving the filter plate.

[0017] For adjusting the near-focus diaphragm, it is presently preferred that

[0018] - the near-focus diaphragms are arranged on a first side of a base plate, which extends parallel to a plane defined by the large near-focus diaphragm openings,

[0019] - one first drive moves an intermediate element, which is likewise arranged on the first side of the base plate,

[0020] - a slide guide is arranged on the intermediate element, into which a first follower pin arranged on one of the near-focus diaphragms is inserted, or vice versa, a first follower pin is arranged on the intermediate element, which is inserted into a slide guide arranged on one of the near-focus diaphragms,

[0021] - the slide guide has a first section extending parallel to the base plate and a second section adjoining the first section, which extends at an obtuse angle to the first section, and

[0022] - when the first follower pin is located in the first section of the slide guide, the near-focus diaphragm is always located in the maximum open position, and when the first follower pin is located in the second section of the slide guide and as far as possible away from the first section of the slide guide, the near-focus diaphragm is always located in the maximum closed position.

[0023] With this design, the adjustment of the respective near-focus diaphragm can be carried out in a simple manner between the maximum open position and the maximum closed position. Thus, during the passage of the first follower pin through the second section of the slide guide, the adjustment of the respective near-focus diaphragm between the maximum open position and the maximum closed position is carried out.

[0024] In the minimal case, only one of the near-focus diaphragms is adjusted by means of one first drive. It is also possible, however, for a plurality of near-focus diaphragms to be adjusted by means of at least one first drive. If, for example, there are four near-focus diaphragms (which delimit a rectangular near-focus diaphragm opening), there can be, for example, two first drives, wherein each of the two first drives together adjusts two opposing diaphragms.

[0025] In the minimal case, there is only one filter plate, which can be moved onto the large near-focus diaphragm opening by means of one first drive. If there are a plurality of first drives, the respective filter plate can be moved onto the large near-focus diaphragm opening by means of the respective first drive. Thus, in the case of two first drives, one filter plate or two filter plates (separately or together) can be moved onto the large near-focus diaphragm opening as required. In the case of four first drives, a maximum of four filter plates can be moved onto the large near-focus diaphragm opening.

[0026] Preferably, the intermediate element is configured as a ring, which can be rotated about an axis extending orthogonally to the base plate by means of one first drive. In this case, the axis contains the center of the large near-focus diaphragm opening (and also of the small near-focus diaphragm opening). It is also possible, in particular in the case of the intermediate element being designed as a ring, for two opposing diaphragms to be jointly adjusted by means of the same intermediate element.

[0027] Preferably, the first follower pin is positively guided by means of a slot guide. As a result, it is not necessary to provide a return spring or the like, which loads the near-focus diaphragm with a return force. As a result, it is also not necessary to overcome this return force by means of one first drive. The first drive can thus be designed comparatively small.

[0028] Preferably, the intermediate element also has a second follower pin, which passes through the base plate through a recess in the base plate. However, the second follower pin does not act on the other near-focus diaphragm and also not on the far-from-focus diaphragm, but rather on the filter plate. The action on the filter plate is such that, when the first follower pin is located in the second section of the slot guide, the filter plate is always moved out of the large near-focus diaphragm opening, and when the first follower pin is located in the first section of the slot guide at a predetermined position spaced apart from the second section of the slot guide, the filter plate is always moved onto the large near-focus diaphragm opening. Thus, during the passage of the first follower pin through the first section of the slot guide, the filter plate is moved onto or out of the large near-focus diaphragm opening. The predetermined position can be, in particular, the end of the first section of the slot guide remote from the second section of the slot guide.

[0029] Preferably, the filter plate has a curved or bent section, so that the second follower pin can be moved under the filter plate, while the first follower pin is moved in the first section of the slide guide onto the second section of the slide guide. Thereby, the movement of the respective focus proximity shutter and the movement of the filter plate can be more easily coordinated with each other.

[0030] The collimator assembly preferably has a return spring, by means of which a return force is exerted onto the filter plate when moving onto the large focus proximity shutter opening. Thereby, it is achieved, inter alia, that the filter plate does not need to be forcibly guided by the second follower pin. The expression "when moving onto the large focus proximity shutter opening" in connection with the expression "exerting a return force" is to be understood as the direction of the return force. Thus, when moving onto the large focus proximity shutter opening, the return force points against the movement of the filter plate, while in the case of moving out of the large focus proximity shutter opening, the return force points with the movement of the filter plate.

[0031] The collimator assembly preferably has a stop, onto which the filter plate is always pressed by the return spring when the filter plate is not deflected by the second follower pin in the direction of the large focus proximity shutter opening. Thereby, a defined rest position of the filter plate is achieved when moving out of the large focus proximity shutter opening.

[0032] The movement of the filter plate is preferably a pivoting movement about an axis, which extends orthogonally to the plane defined by the large focus proximity shutter opening. A pivoting movement about such an axis can be realized more reliably than a linear movement in a plane extending parallel to the plane defined by the large focus proximity shutter opening. In particular, a tilting of the filter plate cannot be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above-described characteristics, features and advantages of the present application, as well as ways and means of realizing the same, will become more fully apparent from the following description, taken in conjunction with the accompanying drawings. Accordingly, it is to be understood that this application is not limited to the particular embodiments described, as such may vary. Therein:

[0034] Figure 1 An X-ray assembly is shown,

[0035] Figure 2 A focus proximity shutter assembly is shown in a maximum open position,

[0036] Figure 3 A focus proximity shutter assembly is shown in a maximum closed position, Figure 2

[0037] Figure 4 ​A perspective view of the collimator assembly is shown from an angle above.

[0038] Figure 5 Shown from the lower diagonal Figure 4 A perspective view of the collimator assembly.

[0039] Figure 6 The inner wall of the intermediate element is shown in the unfolded diagram, and

[0040] Figure 7 A side view of the filter plate is shown. Detailed Implementation

[0041] according to Figure 1 The X-ray assembly includes an X-ray source 1. The X-ray source 1 emits X-ray radiation during operation, which is detected by an X-ray detector 2. The X-ray radiation passes through the object being inspected 3 (e.g., a person). A collimator assembly 4 is arranged between the X-ray source 1 and the object being inspected 3. The collimator assembly 4 has a light-shielding assembly 5 near the focal point and a light-shielding assembly 6 away from the focal point. The light-shielding assembly 5 near the focal point is arranged closer to the X-ray source 1 than the light-shielding assembly 6 away from the focal point.

[0042] The light-shielding assembly 5 near the focal point has multiple light-shielding elements 7 near the focal point, for example, according to... Figure 2 and 3 The illustration shows four light-shielding elements 7 near the focal point. The light-shielding elements 7 near the focal point are based on... Figure 1 The first driver 8 can be used to open the device to the maximum position. Figure 2 ) and maximum closing position ( Figure 3 Adjust between ) . The light-shielding element 7 near the focal point forms a large light-shielding opening near the focal point in the maximum open position ( Figure 2 And in the fully closed position, a small light-shielding opening is formed near the focal point. Figure 3 Typically, the adjustment of opposing, near-focal-point light-shielding components 7 is caused by a single first driver 8, in pairs. The near-focal-point light-shielding components 5... Figure 1 The middle is drawn at the maximum closed position.

[0043] The light-shielding component 6, located away from the focal point, is typically constructed to be completely similar to the light-shielding component 5, located near the focal point. This light-shielding component away from the focal point has multiple light-shielding elements 9 located away from the focal point. The light-shielding elements 9 are configured according to... Figure 1 Adjustment is achieved using the second driver 10. The second driver 10 is a different driver from the first driver 8. The light-shielding assembly 6, located away from the focal point, is... Figure 1 The middle part is drawn in the maximum open position.

[0044] In addition, according to Figure 1There is also a filter plate 11. The filter plate 11 is usually made of copper. The filter plate usually has a thickness of 0.6 mm or 2.1 mm. The filter plate 11 is movable onto the large near-focus diaphragm opening. The expression "movable onto the large near-focus diaphragm opening" means that the filter plate 11 in this case completely covers the large near-focus diaphragm opening. That is to say, from the X-ray source 1, only the X-ray radiation that has previously passed through the filter plate 11 reaches the X-ray detector 2. This is independent of whether the filter plate 11 is arranged closer to the X-ray source 1 than the near-focus diaphragm assembly 5 or further away from the X-ray source 1 than the near-focus diaphragm assembly 5 (where the latter is shown in Figure 1 and is also preferred).

[0045] The movement of the filter plate 11 is effected by means of one of the first drives 8. When the filter plate 11 is moved, the near-focus diaphragm 7 that is adjusted by this first drive 8 is in the maximum open position of the near-focus diaphragm 7.

[0046] Figure 4 and Figure 5 A possible specific design of the collimator assembly 4 is shown. According to Figure 4 and Figure 5 , the collimator assembly 4 has a base plate 12. The base plate 12 extends parallel to the plane defined by the large near-focus diaphragm opening. The near-focus diaphragms 7 are arranged on a first side of the base plate 12. In Figure 4 and Figure 5 only two of the near-focus diaphragms opposite one another in the near-focus diaphragm 7 are shown. The side of the base plate 12 on which the near-focus diaphragms 7 are arranged is then referred to as the upper side of the base plate 12 according to the usual arrangement (X-ray source 1 above, X-ray detector 2 below).

[0047] The first drives 8 are arranged on the base plate 12, by means of which the filter plate 11 is also moved. The other first drives 8 are usually likewise arranged on the base plate 12. However, these other first drives are of secondary importance for further embodiments of the application and are therefore not shown in Figure 4 and Figure 5 . The following embodiments always relate to the first drives 8, by means of which the filter plate 11 is also moved.

[0048] The first drives 8 move an intermediate element 13 according to Figure 4 . The intermediate element is likewise arranged on the upper side of the base plate 12. For example, the first drives 8 can act via pinions 14 onto a toothed portion 15 of the intermediate element 13. At present, the intermediate element 13 is moved according to Figure 4 and Figure 5The illustration in Fig. 13 of the application is preferred, wherein the intermediate element 13 is configured as a ring. In this case, the ring can be rotated about an axis 16 extending orthogonally to the base plate 12 by means of the first drive 8. The axis 16 is in accordance with the Figure 2 The center of the illustration in Fig. 13 of the application also comprises a small aperture of the diaphragm close to the focal point. Figure 3 The center of the illustration in Fig. 13 of the application also comprises a small aperture of the diaphragm close to the focal point.

[0049] In accordance with the Figure 4 At the intermediate element 13, a slide guide 17 is arranged. A follower pin 18 is inserted into the slide guide 17, which follower pin is arranged on the diaphragm 7 close to the focal point. The follower pin 18 is subsequently referred to as a first follower pin 18 in order to be able to linguistically distinguish it from a second follower pin which is also introduced later.

[0050] Figure 6 The inner wall of the intermediate element 13 is illustrated in an expanded view together with the slide guide 17. In accordance with the Figure 6 (As can also be seen from this solution in Figure 4 The slide guide 17 has a first section 19 and a second section 20. The first section 19 extends parallel to the base plate 12. The second section 20 adjoins the first section 19, however forms an obtuse angle a with the first section 19. The angle a is mostly in the range between 150° and 170°.

[0051] If the intermediate element 13 is moved by means of the first drive 8 (here: rotated) and the first follower pin 18 is located in the second section 20, the height position of the first follower pin 18 relative to the base plate 12 thereby changes. The further the first follower pin 18 is lifted relative to the base plate 12, the further the respective diaphragm 7 close to the focal point is moved towards the maximum closed position. In particular, when the first follower pin 18 is located within the second section 20 and as far as possible away from the first section 19, the respective diaphragm 7 close to the focal point is located in the maximum closed position. Conversely, if the first follower pin 18 is moved closer towards the base plate 12, the first follower pin 18 is moved further towards the base plate 12 and the respective diaphragm 7 close to the focal point is moved further towards the maximum open position. If the first follower pin 18 reaches the first section 19, the respective diaphragm 7 close to the focal point is located in the maximum open position. In order to move the diaphragm 7 close to the focal point, the diaphragm 7 close to the focal point can be pivoted, for example, about a pivot axis 21.

[0052] If the intermediate element 13 is moved by means of the first drive 8 (here: rotated) and the first follower pin 18 is located in the first section 19, the height position of the first follower pin 18 relative to the base plate 12 does not change due to the course of the first section 19 parallel to the base plate 12. Thus, the respective diaphragm 7 close to the focal point is in the maximum open position. This is independent of at which point the first follower pin 18 just lies within the first section 19.

[0053] The arrangement of the slide guide 17 and the first follower pin 18 can also be reversed. Thus, instead of the design shown in Figure 4 and 5 it is equally possible for the first follower pin 18 to be arranged on the intermediate element 13 and for the follower pin 18 to be embedded in a slide guide 17 arranged on the respective focus-adjacent light barrier 7. The functional principle does not change thereby.

[0054] According to Figure 6 , the movement of the first follower pin 18 is limited by the slide guide 17 not only upwards (= away from the base plate 12) but also downwards (= towards the base plate 12) at each point of the slide guide 17 at which the first follower pin 18 is located at this point in time. The first follower pin 18 is thus forced to be guided by means of the slide guide 17. It is alternatively possible for the first follower pin 18 to be guided on one side only by means of an edge of the slide guide 17 and for the respective focus-adjacent light barrier 7 to be loaded with a spring force in the direction of this edge. However, this design is not preferred.

[0055] As already mentioned, the intermediate element 13 has, in addition to the first follower pin 18, a further follower pin 22, which is subsequently referred to as the second follower pin 22. The second follower pin 22 is arranged according to Figure 5 through the base plate 12 by means of a recess 23 in the base plate 12. The second follower pin 22 acts onto a filter plate 11, which is arranged according to Figure 5 on the underside of the base plate 12. In particular, in the illustration of Figure 5 , the filter plate 11 can be pivoted about an axis 24 by means of the second follower pin 22. The movement of the filter plate 11 is thus a pivoting movement about the axis 24. The axis 24 extends orthogonally to the plane defined by the large focus-adjacent light barrier opening. In the given arrangement of the filter plate 11 on the base plate 12, the axis 24 also extends orthogonally to the base plate 12.

[0056] Figure 5 A position (rotational position) is shown in which the second follower pin 22 just begins to act onto the filter plate 11 as soon as the intermediate element 13 is rotated in the illustration of Figure 5 in the clockwise direction, or in which the second follower pin just stops acting onto the filter plate 11 as soon as the intermediate element 13 is rotated in the counterclockwise direction. The filter plate 11 is thus located in a rest position in Figure 5 , in which the filter plate also does not move partially onto the large focus-adjacent light barrier opening. However, the greater the extent to which the intermediate element 13 is rotated in the clockwise direction starting from the position shown in Figure 5 , the greater the extent to which the filter plate 11 is moved from Figure 5The greater the degree to which the indicated position pivots about the axis 24. At the latest when the second follower pin 22 reaches the lower end of the recess 23, the filter plate 11 is moved onto the large, near-focus diaphragm opening. Figure 5

[0057] During the entire movement of the filter plate 11 (and during the corresponding position or rotational position of the intermediate element 13), the first follower pin 18 is located in the first section 19 of the runner guide 17. The reverse of this is that when the first follower pin 18 is located in the second section 20 of the runner guide 17, the filter plate 11 is always (completely) moved out of the large, near-focus diaphragm opening. Furthermore, for the same reason, when the first follower pin 18 is located at a predetermined position within the first section 19, which is spaced apart from the second section 20, the filter plate 11 is (completely) moved onto the large, near-focus diaphragm opening. In the usual case, the predetermined position is the end of the first section 19, which is spaced apart from the second section 20. But this end is of secondary importance.

[0058] According to the illustration in Figure 5 , there is preferably a return spring 25. Upon movement onto the large, near-focus diaphragm opening, a return force is exerted onto the filter plate 11 by means of the return spring 25. The return spring 25 shown in Figure 7 is thus a tension spring. But in other arrangements of the return spring 25, a design as a pressure spring or as a coil spring is also possible. When the filter plate 11 is not deflected by the second follower pin 22 in the direction of the large, near-focus diaphragm opening, this filter plate 11 is pressed by the return spring 25 against the stop 26.

[0059] The filter plate 11 has, according to Figure 7 , a starting section 27, an end section 28 and an intermediate section 29 between the starting section 27 and the end section 28. The end section 28 is the section of the filter plate 11 that is moved onto the large, near-focus diaphragm opening. The starting section 27 is the section of the filter plate 11 in which the axis 24 is currently present. The intermediate section 29 is curved or, as shown in ​ , is bent. Due to the intermediate section 29, the end section 28 is spaced apart from the base plate 12. Thereby, the second follower pin 22 can be moved under the filter plate 11, while the first follower pin 18 moves in the first section 19 of the runner guide 17 onto the second section 20 of the runner guide 17. This design makes it easy to decouple the movement curve of the near-focus diaphragm 7 on the one hand and the movement curve of the filter plate 11 on the other hand as required.

[0060] ​The application has a number of advantages. In particular, the following feasible solution is provided, which can be implemented simply, namely that the filter plate 11 is integrated into the collimator assembly 4 and can be moved automatically into the beam path from the X-ray source 1 to the X-ray detector 2. The collimator assembly 4 according to the application can be constructed compactly. As a result of the automated method of the filter plate 11, it is even possible to automate the calibration process itself.

Claims

1. Collimator assembly for an X-ray tube (1), - wherein, - having a near-focus diaphragm assembly (5) with a plurality of near-focus diaphragms (7) and a far- focus diaphragm assembly (6) with a plurality of far- focus diaphragms (9), - wherein the near-focus diaphragms (7) are adjustable between a maximum open position and a maximum closed position by means of a number of first drives (8) such that the near-focus diaphragms (7) form a large near-focus diaphragm opening in the maximum open position and a small near-focus diaphragm opening in the maximum closed position, - wherein the far-focus diaphragms (9) are adjustable between a maximum open position and a maximum closed position by means of a number of second drives (10) such that the far-focus diaphragms (9) form a large far-focus diaphragm opening in the maximum open position and a small far-focus diaphragm opening in the maximum closed position, characterized in that - the first drives (8) and the second drives (10) are different drives from one another, and - by means of one of the first drives (8), a filter plate (11) is movable onto the large near-focus diaphragm opening in the maximum open position of the near-focus diaphragms (7).

2. Collimator assembly according to claim 1, characterized in that - the near-focus diaphragms (7) are arranged on a first side of a base plate (12) which extends parallel to a plane defined by the large near-focus diaphragm opening, - the one first drive (8) moves an intermediate element (13) which is likewise arranged on the first side of the base plate (12), - a first follower pin (18) arranged on one of the near-focus diaphragms (7) is embedded in a slot guide (17) arranged on the intermediate element (13) or vice versa, - the slot guide (17) has a first section (19) which extends parallel to the base plate (12) and a second section (20) which adjoins the first section (19) and extends at an obtuse angle (a) to the first section (19), and - when the first follower pin (18) is located in the first section (19) of the slot guide (17), the near-focus diaphragm (7) is always located in the maximum open position and when the first follower pin (18) is located in the second section (20) of the slot guide (17) and as far as possible away from the first section (19) of the slot guide (17), the near-focus diaphragm is always located in the maximum closed position.

3. Collimator assembly according to claim 2, characterized in that The intermediate element (13) is configured as a ring which can be rotated by means of the one first drive (8) about an axis (16) which extends orthogonally to the base plate (12) and which contains the center of the large, near-focus diaphragm opening.

4. Collimator assembly according to claim 2 or 3, characterized in that The first follower pin (18) is forced guided by means of the runner guide (17).

5. Collimator assembly according to claim 2, 3 or 4, characterized in that The intermediate element (13) has a second follower pin (22) which passes through the base plate (12) through a recess (23) in the base plate (12) and acts onto the filter plate (11) in such a way that the filter plate (11) is always moved out of the large, near-focus diaphragm opening when the first follower pin (18) is located in the second section (20) of the runner guide (17) and is always moved onto the large, near-focus diaphragm opening when the first follower pin (18) is located in a predetermined position in the first section (19) of the runner guide (17) which is spaced apart from the second section (20) of the runner guide (17).

6. Collimator assembly according to claim 5, characterized in that The filter plate (11) has a curved or bent section (29) in such a way that the second follower pin (22) can be moved under the filter plate (11) while the first follower pin (18) moves in the first section (19) of the runner guide (17) onto the second section (20) of the runner guide (17).

7. Collimator assembly according to any of the preceding claims, characterized in that The collimator assembly has a return spring (25) by means of which a return force is exerted onto the filter plate (11) when it is moved onto the large, near-focus diaphragm opening.

8. Collimator assembly according to claim 7, characterized in that The collimator assembly has a stop (26) onto which the filter plate (11) is always pressed by the return spring (25) when it is not deflected by the second follower pin (22) in the direction of the large, near-focus diaphragm opening.

9. Collimator assembly according to any of the preceding claims, characterized in that The movement of the filter plate (11) is a pivoting movement about an axis (24) which extends orthogonally to the plane defined by the large, near-focus diaphragm opening.

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