Patent Number: 
Section: abstract

Collimator apparatus is provided for an X-ray imaging system comprising an X-ray tube disposed to project an X-ray beam, and a detector spaced apart from the X-ray tube for receiving X-rays of the beam within an Active Imaging Area (AIA). The apparatus comprises a first collimator positioned along the path of the beam, the first collimator being vertically adjustable, and being operable to symmetrically collimate the beam. The apparatus further comprises a second collimating device positioned between the first collimator and the detector. The second collimating device limits the uppermost rays of the symmetrically collimated beam which reach the detector to a predetermined upper boundary. Thus, the second collimating device serves to fix the upper edge of the AIA on the detector. At the same time, the second collimating device allows the lowermost rays of the symmetrically collimated beam reaching the detector, which define the lower edge of the AIA, to have a lower boundary which is determined by selective adjustment of the first collimator.