Patent Number: 046726527
Section: claims

1. An x-ray apparatus, comprising in combination: an x-ray tube for transmission of x-rays through an object under examination;  an image intensifier for receiving said x-rays transmitted through said object;  a video camera coupled to said image intensifier for generating a video signal corresponding to the attenuation of said x-rays transmitted through said object;  a semitransparent diaphragm arranged between said x-ray tube and said image intensifier, said diaphragm being positioned close to said x-ray tube and comprising  a circuit for evaluation coupled to said video camera for receiving said video signal and for generating a control signal therefrom for controlling said means for sliding said blades, said evaluation circuit comprising  a position determination circuit for correlating the position of said blades with said video signal from clock signals and from control signals which determine selected blades of interest;  a converter stage for receiving said video signal;  a gate coupled to said position determination circuit and said converter stage, said gate providing an output signal;  a detector receiving said output signal of said gate for detecting the peak value of said video signal, said detector issuing a detector output signal; and  a comparator for comparing said detector output signal with an adjustable threshold, said comparator generating a control signal for controlling said means for sliding said blades. 2. The x-ray apparatus of claim 1, wherein said region has a centerline and said blades are perpendicular to said centerline. 3. The x-ray apparatus of claim 1, wherein said region has a centerline and said blades are at an angle of at least 20.degree. and at most 90.degree. with respect to said centerline. 4. The x-ray apparatus of claim 1, further comprising first and second motors each corresponding to one of the groups of blades, and means for engaging individual ones of the blades with its corresponding motor, such that said individual blades are made to slide independently. 5. The x-ray apparatus of claim 4, wherein said engaging means comprises a coupling magnet. 6. The x-ray apparatus of claim 1, further comprising a rotatable ring to which said blades are mounted, such that said blades may be aligned with the scanning direction of said video camera. 7. The x-ray apparatus of claim 1, wherein said evaluation circuit comprises: