Patent Number: 046413359
Section: claims

1. An improvement to a stereo radiographic X-ray apparatus comprising first, second and third spaced-apart radiation focal points arranged such that the first and second focal points lie in a plane and the third focal point is located intermediate the first and second focal points in the plane, the improvement comprising: first and second pairs of X-ray opaque shutter leaves, each pair of shutter leaves being associated with a corresponding one of the first and second focal points and positioned to collimate radiation therefrom in planes which are perpendicular to said plane and comprising an internal shutter leaf and an external shutter leaf which are so positioned that the two internal shutter leaves are adjacent each other between the two external shutter leaves and radiation from the third focal point can be collimated by the two internal shutter leaves; and  means for independently moving the shutter leaves, such that each of the said pairs of shutter leaves can individually collimate radiation from its corresponding focal point for stereo radiography and the two internal shutter leaves can alternatively collimate radiation from the third focal point and to close shutter apertures through which radiation from the first and second focal points is directed.