| 摘要 |
Unused camera pixel locations are recovered when shifting from photographing an x-ray scintillation image of a larger subject to that of a substantially smaller one by using a suitably shorter optical path combined with appropriate changes in focus. The optical path for large subjects involves a first mirror followed by a second mirror. The camera receives light from the second mirror, and is in a fixed and unchanging physical relationship to that second mirror, forming a unitary mirror-camera assembly. To shorten the optical path that unitary assembly is rotated about an axis from a position where it was in the optical path downstream from the first mirror to one where the second mirror is interposed between the scintillation screen and the first mirror, and also such that the camera looks in a different direction along the shortened optical path length. Focus adjustment to accommodate the different optical paths may be accomplished by changing the spacing of elements internal to the lens, or, the entire lens assembly can be moved a bit closer to or further away from the camera body. The scintillation image may be replaced with a glass plate carrying a document illuminated from within a housing carrying the unitary mirror-camera assembly.
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