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AssigneeU.S. Philips Corporation
InventorsRudolph M. Snoeren, Jan W. Slotboom
Estimating the term…
An x-ray examination apparatus includes an imaging arrangement, devised for performing fluoroscopy. Which has image sensors that are efficiently optically coupled with an x-ray sensitive radiation conversion screen. Consequently, the image sensors produce an electrical signal having a high signal-to-noise ration when low doses of x-radiation are administered. An x-ray conversion screen is provided with a tapetum filter so as to concentrate light in the forward direction. Furthermore, the x-ray conversion screen is preferably fitted with a light reflecting layer for reflecting light that has been reflected by the tapetum filter, said light reflecting layer being transparent for x-radiation. Further concentration of light in the forward direction is achieved by placing a light-transparent material having a suitable refractive index between the radiation conversion screen and lenses that concentrate the light onto the image sensors. Semiconductor image sensors in the form of charge-coupled devices are provided for converting a visible image into an electronic video signal. In order to improve the effectiveness of the CCDs, weak avalanching is applied so as to increase both sensitivity and signal-to-noise ratio of the sensors.
An x-ray examination apparatus comprising an x-ray source, an imaging arrangement comprising a radiation conversion means facing the x-ray source, for converting image carrying x-radiation into image carrying visible radiation, image conversion means having a plurality of image sensors for converting the image carrying visible radiation formed by said radiation conversion means into an electrical signal, and a plurality of lenses aligned with the radiation conversion means, so that respective regions of said radiation conversion means are imaged on respective ones of said image sensors, and further comprising multilayer means intermediate the image sensors and the lenses for concentrating a light intensity distribution produced by the radiation conversion means substantially in a single direction by transmitting light having an angle of incidence in a region around normal incidence and reflecting light having an angle of incidence beyond said region.
A radiation conversion screen, suitable for use in an x-ray examination apparatus, the radiation conversion screen comprising an x-ray sensitive phosphor layer, a further layer at a first side of the x-ray sensitive phosphor layer for transmitting x-radiation and reflecting visible radiation and, on a second side of the x-ray sensitive phosphor layer opposite the first side, a tapetum filter having a substantial transmittivity for light having an angle of incidence in a region around normal incidence and having a substantial reflectivity of light having an angle of incidence beyond said region.
Dependencies are inferred from the claim text.