Patent Number: 
Section: claims

1. An apparatus for radiation analysis of a sample to be examined, in which a radiation beam runs along an optical path from a radiation source to a radiation detector via the sample to be examined, in which optical path a collimator with collimating elements is present, said collimator, as a result of a movement through the radiation beam, exhibits a variable aperture angle for the radiation beam, wherein the collimating elements are rotated through the radiation beam to vary a magnitude of a collimating element length (L) exposed to the radiation beam. 2. An apparatus for radiation analysis as claimed in  claim 1 , in which the collimating elements have the form of mutually parallel plates and in which said movement comprises a rotation around a shaft perpendicular to the plates. claim 1 3. An apparatus for radiation analysis as claimed in  claim 2 , in which the plates have an elliptical shape. claim 2 4. An apparatus for radiation analysis as claimed in  claim 2 , in which the plates at least partly have an elliptical shape. claim 2 5. An apparatus for radiation analysis as claimed in  claim 1 , in which collimating elements have the form of channels, said channels having a same-size cross section and mutually different lengths, and said movement of the collimating elements comprises a displacement transverse to the longitudinal direction of the channels. claim 1 6. An apparatus for radiation analysis as claimed in  claim 5 , in which the channels are embodied as X-ray optical fibers. claim 5 7. A collimator to be used in an apparatus for radiation analysis by means of a radiation beam, with a plurality of collimating elements arranged with spacing between each of the collimating elements, said collimator comprising a movement mechanism for movement of the collimating elements through the radiation beam, so that the collimator exhibits a variable aperture angle for the radiation beam along a longitudinal direction of the collimating elements, wherein the movement mechanism is arranged for exposing a variable length (L) of the collimating elements to the radiation beam so that, as a result, the variable aperture angle for the radiation beam is obtained. 8. A collimator as claimed in  claim 7 , in which the collimating elements have the shape of mutually parallel plates, and in which the movement mechanism is arranged for rotating the collimator around a shaft perpendicular to the plates. claim 7 9. A collimator as claimed in  claim 8 , in which the plates have a rectangular shape. claim 8 10. A collimator as claimed in  claim 8 , in which the plates at least partly have an elliptical shape. claim 8 11. A collimator as claimed in  claim 7 , in which the collimating elements are in the form of channels having a cross section in itself in which channels have mutually different lengths, and in which the movement mechanism is arranged for displacing the collimator transversely to the longitudinal direction of the channels. claim 7 12. A collimator as claimed in  claim 11 , in which the channels are embodied as X-ray optical fibers. claim 11