Recording Scan Data in Photographic Colour During Live Time. I. From the Conventional Scanner. II. From a Ten Detector Scanner

The authors have developed instruments for scan recording in colour, combining the speed, versatility and silence of the cathode-ray tube, the contrast and latitude of a photographic process, and the rapid development of Polaroid colour film. I. The electron beam of a modified cathode-ray oscilloscope is made to track the motion of the scanner detector. The beam is normally off but is flashed on at each impulse from the scanner analyser. The screen is photographed in colour during a time exposure through a train of colour filters driven back and forth through the lens system of the camera by a servo mechanism controlled by the ratemeter circuit of the scanner. The instrument is calibrated so that the maximum intensity photographs in red. As count- rates decrease, other filters are driven into place to photograph the screen in continuously varying saturated hues of orange, yellow, green, blue and violet. Examples are shown from scans of models and from our 17 000 clinical colour scan library, demonstrating enhanced contrast, extended dynamic range, and quantitative information at a glance. II. More recently, the authors have designed an instrument for recording scan data in colour from a ten detector moving scanner system. As usually employed, the Dynapix presents scan data on the screen of a cathode-ray tube as flashes of varying intensity appearing sequentially in rows and columns at a repetition frequency up to 200/sec, and too rapid for our system previously described. In the new colour version of the instrument, colour filters mounted in a wheel between the lens elements of the camera are driven at a continuous 9 400 rev/min. The electron beam is pulsed by intensity modulated time delay so that an input signal of maximum amplitude delays the flash until red filter is traversing the lens opening. Signals of lesser amplitude are converted to decreasing time delays, resulting in flashes photographing as corresponding hues of orange, through violet. The recording may be either live or played back from magnetic tape. Scans are shown comparing this colour system to the usual grey scale. (author)