Three-dimensional cathode-ray tube displays

The display of three-dimensional information is considered with particular reference to a radar system in which a narrow pulsed beam of radio-frequency energy is used to explore automatically a volume of space. The three-dimensional displays are used to display the positions of the reflected ¿signals¿ with respect to the three co-ordinates of the volume, in order that the radar can be used as an object-detecting and -locating system in three dimensions. In the past, ¿configurational¿ methods have been used, wherein the shape of the intensity-modulated echo-trace on the cathode-ray tube is altered to add a third variable to the two already provided by the c.r.t. deflections. These types are not discussed, attention being concentrated on other methods. The ¿truly three-dimensional displays¿ utilize a mechanical motion to add a third dimension to the screen of the cathode-ray tube, the picture appearing as an actual volume. The ¿perspective displays¿ simulate the same picture as in the previous display without any moving mechanisms, rotation of the volume and/or stereoscopy being used to give the impression of three dimensions. The ¿oblique displays¿ obtain the required three co-ordinates by combinations of two or more two-co-ordinate pictures on the same cathode-ray tube. The ¿polychromatic displays¿ use colour to represent a spatial co-ordinate. The physiological and psychological problems of the human operator peculiar to three-dimensional displays are discussed, and a Section is included on the relative advantages of ¿true¿ and ¿relative¿ displays. Another Section on ¿display sensitivity¿ leads to the general theoretical considerations involved in three-dimensional displays. The application of three-dimensional displays to other fields, for example X-ray photography, is briefly discussed. The revised form of the radar equation for use with three-dimensional displays is given in an Appendix.