Patent Number: 042108179
Section: claims

1. An apparatus for practicing biplane radiography comprising first and second X-ray emitters arranged to direct x-rays through a common object along intersecting planes and first and second film changers for sequentially presenting film for exposure by x-rays generated by said first and second x-ray emitters respectively, the improvement for eliminating cross-fogging comprising: first and second shielding means associated with the first and second film changers respectively, each said shielding means having radiolucent and radiopaque portions alternately disposed in front of the associated film changer to allow or block passage of x-rays to the film presented for exposure, respectively; and  means for synchronizing the shield means to dispose the radiopaque portion of one shielding means in front of the film presented for exposure by its associated film changer when the radiolucent portion of the other shielding means is disposed in front of the film presented for exposure by its associated film changer. 2. The apparatus of claim 1 wherein at least one of said shielding means comprises a flexible endless belt having alternating radiolucent and radiopaque portions with said endless belt forming a loop which surrounds said film changer. 3. The apparatus of claim 1 wherein at least one of said shielding means comprises a planar member having adjacent radiolucent and radiopaque portions and mounted for movement in a plane parallel to the plane of the film presented for exposure. 4. The apparatus of claim 3 wherein said shielding means comprises a disc mounted for rotation in said plane parallel to the plane of the film presented for exposure and having alternating sectors of radiolucent and radiopaque material. 5. The apparatus of claim 3 wherein said shielding means comprises a planar member having one radiopaque and one translucent section mounted for reciprocal movement.