| 摘要 |
An X-ray examination apparatus is provided with an exposure control for controlling the X-ray source and for adjusting the signal amplification of the television camera which converts the image on the exit window of the X-ray image intensifier into a video signal. The signal amplification of the television camera is adjustable so as to enable the reproduction of a wide dynamic range of images on the exit window with adequate image contrast and image brightness. In order to avoid annoying transitions in image brightness due to the variation of exposure control signals, the exposure control is configured to supply a control signal which varies smoothly in response to changes in image brightness and image contrast, for example during fluoroscopy where a series of images is formed by X-ray exposure. In a preferred embodiment the exposure control supplies a control signal which varies linearly between minimum and maximum levels as a function of mean brightness.
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