GB897363A - Improvements in or relating to display devices - Google Patents

Abstract

897,363. Optical projection systems. HARRIES TELEVISION RESEARCH Ltd. Aug. 12, 1959 [Aug. 13, 1958], No. 26040/58. Class 97(1). In an optical projection system for projecting a two-dimensional image of an object on to the surface of a three-dimensional model of the same object, there is provided in the light path to the model a device having at least one surface which varies in slope and comprises several facets separated by lines of discontinuity of slope, the gradient of each facet being chosen to displace the points of arrival of the rays at the surface of the model by the amounts necessary to correct keystone distortion. This device which is described in the Specification 897,361 may also correct for pincushion and barrell distortions and, by giving each facet a lenticular surface, for defocusing. Focus may also be improved by providing for the mounting surface (e.g. film, transparency or television phosphor) or upon which the two-dimensional image is produced to be curved or tilted about the optical axis. As shown in Fig. 1, a cinematograph film 11 bearing coloured images of a person's face, is projected through a correcting element 15 on to the back projection screen 10 having part thereof in the form of a three dimensional model of the same person's face. In this way different combinations of, for example, cosmetics and hair colouring can be demonstrated. The film may have a synchronized sound track and there may be a loud-speaker 24 fed from a pick-up 23. In another form, several projectors, each with a keystone distortion correcting device, project images from different directions on to the single three dimensional model, the projectors operating synchronously (Fig. 3, not shown). Television projectors may be used instead of cinematograph projectors, in which case the video signals supplied to the projectors, the audio signal supplied to a loudspeaker and the synchronizing signals and scanning pulses may be provided by tape recorder. The model may also be moveable in synchronism with movements which appear successively in the two dimensional image which is projected thereon; alternatively, the projector may move in simulation of the camera movement during recording of the two dimensional image. The model and the two dimensional image may be produced from the same object, in which case the movements of the model may be made to follow those by the object as by servo mechanisms and recording tape.