Patent Number: 052241459
Section: claims

1. An X-ray beam limiting apparatus for a stereoscopic X-ray tube having first and second X-ray focal points separated from each other by a predetermined distance, comprising; pivotable blade means for limiting inner edges of pyramid-shaped X-ray beams emitted from the first and second X-ray focal points, while pivoting around a common center line of pivot shafts, respectively; and,  first slidable blade means for limiting outer edges of the pyramid-shaped X-ray beams emitted from the first and second X-ray focal points, while sliding on a plane substantially perpendicular to travelling paths of the pyramid-shaped X-ray beams.  a stepping motor driven by pulse signals;  a lead screw member pivotably driven by the stepping motor;  a guide plate member pivotably journalled to the lead screw member; and  a blade with an X-ray beam shielding part pivotably driven by the guide plate member.  a circular fixed blade positioned between said pivotable blade means and said first slidable blade means, for shielding the pyramid-shaped X-ray beams which exceed an outer case of an X-ray detecting plane of the X-ray tube.  a compensating filter blade positioned below said circular fixed blade along the X-ray travelling paths, for compensating X-ray absorption occurring in an organ of a biological body under medical examination; and  a second slidable blade means positioned below said compensating filter blade along the X-ray travelling paths, for setting an X-ray projection field of the X-ray tube.  a second slidable blade means positioned below said first slidable blade means along the X-ray travelling paths, for setting an X-ray projection field of the X-ray tube. 2. An X-ray limiting apparatus as claimed in claim 1, wherein said pivotable blade means each includes: 3. An X-ray limiting apparatus as claimed in claim 1, further comprising: 4. An X-ray limiting apparatus as claimed in claim 3, further comprising: 5. An X-ray limiting apparatus as claimed in claim 3, further comprising: 6. An X-ray limiting apparatus as claimed in claim 1, wherein said distance of the first and second focal points is selected to be approximately 35 mm.