GB779308A - Improvements in and relating to the projection of mosaic pictures - Google Patents

Abstract

779,308. Optical projection apparatus. VITARAMA CORPORATION. June 22, 1955 [July 21, 1954], No. 18122/55. Class 97(1) [Also in Group XL(b)] Apparatus comprising at least two projectors for projecting separate images so that they meet or overlap on a screen, includes means for maintaining the amount of light in the marginal portions of each light beam and responding to a change in said amount of light so as automatically to vary the amount of light means passing from the light source of at least one projector to the marginal portions of the image projected thereby so as to obtain a predetermined illumination intensity in the adjacent or overlapping portions of the separate images. The apparatus shown comprises projectors 9, 10 and 11 which form overlapping images on a screen 12 and include pairs of photo-cells 13, 19; 21, 22; and 24, 25 on to which light passing to the opposite sides of the respective film gates is reflected. Each photo-cell is connected through an amplifier 41 and one end of a differential relay 42 to servomotors 27, 28; 31. 32; and 34, 35. The other end of each relay 42 is connected to a reference signal source such as a signal generator 45. These servomotors serve to operate reflectors in each projection so as to vary the amount of light passing through one or other or both sides of the film gate or the associated projector when the light received by the respective cell differs from the reference intensity as determined by the signal from generator 45 Thus, in Fig. 4, the servomotors 27, 28 associated with the cells 18, 19 of one projector 9 serve to move axially two spheroidal reflectors 103, 104 which combine with a main reflector 98 and parabolic side reflectors 111, 112 to project light from a carbon arc 96 on to the film in gate 102. Alternatively, the motors may move angularly two pivoted reflectors as in Fig. 5 (not shown). The light may be reflected on to the photo-cells by reflectors disposed at opposite sides of the film gate or by reflecting strips or discs on the shutter of the projector as in Fig. 6 (not shown). In another form, Fig. 2 (not shown) the signal determining the reference intensity is provided by the output of the cells associated with reflector 10.