Patent US 4,359,759

The radiographic system includes an x-ray source for irradiating a patient with x-radiation. An image intensifier receives the x-radiation which has traversed the patient and produces an optical image of a radiation shadowgraph of the examined area of the patient. A television camera converts the optical image into a video signal. An image processor stores each frame of the video signal generated by the television camera as an electronic image of the optical image viewed on the image intensifier. Alternately, a plurality of frames from the television camera may be combined to produce a composite image. A bias light is provided adjacent the target of a television camera to illuminate the target before an optical image from the image intensifier is monitored by the television camera. This improves the linearity of the response of the television camera, particularly to low amplitude light intensities on the first few video frames generated by the camera.