Proceedings PaperLens optical coupling versus fiber optical coupling: the impact on x-ray TV image quality with CCDs and pick-up tubes
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The limited light sensitivity of the TV-pick-up devices and the desire for low dose imaging in X-ray fluoroscopy causes the use of extremly high aperture lens optics between X-ray image intensifier and TV-sensor (1). Therefore a contrast reducing optical feedback between the TV-sensor and the output screen of the X-ray image intensifier may occur, if the light of the output screen of the X-ray image intensifier is reflected from the sensor's photoconductor. The contrast relations in the case of lens coupling of X-ray IL of different output structures with some CCD-sensors and different kinds of pick-up tubes have been measured and will be discussed. One possible way to reduce contrast loss due to stray light is direct fiber optical coupling. We investigated such systems with fiber optic pick-up tubes and a CCD equipped with a fiber optic plate in front of the sensor area coupled via a fiber optical taper to an X-ray image intensifier with fiber optic output window. The drawback of every direct fiber optical coupling is, however, that the light flux to the TV-sensor cannot be controlled. Therefore an adaptation of such a system to the practical needs of varying indMdual applications cannot be performed. Some imaging properties oflens coupling, fiber optical coupling and mixed coupling (fiber optics and lens optics in one system) have been evaluated and will be compared. Some precautions against loss in contrast and requirements regarding signal to noise ratio will be outlined.