EXTENDED MONOCHROMATIC X-RAY SOURCE

摘要

An extended radiating aperture for X-rays is provided by means of a stationary target of a heavy metal positioned for uniform illumination by high speed electrons emanating from a cathode and accelerating through a difference of potential between the cathode and the target. The target is in the form of a relatively thin film which can be deposited on a substrate transparent to X-radiation. A layer of fluorescent material is placed adjacent the substrate on the opposite side thereof from the target so that X-rays generated within the target material pass through the target material and impinge on the fluorescent layer. The fluorescent material enhances the monochromaticity of the X-ray spectrum by emitting fluorescent X-radiation while substantially absorbing incident X-radiation having energies above the fluorescent radiation spectrum. A zone plate is positioned adjacent the fluorescent layer to spatially modulate the radiation of the radiating aperture to provide this radiation with a spatial frequency spectrum suitable for obtaining high resolution roentgenograms. The zone plate provides a coding on the roentgenogram which is then decoded by an optical processor to form a visible image of an object being X-rayed. Alternative embodiments of the invention include the use of an inclined transmissive target, a transmissive target having serrations, and the use of a moire pattern mask between the target and the fluorescent material to augment fluorescent radiation from the target and to inhibit the passage of X-radiation normal to the layer of fluorescent material.