Journal of the Society of Motion Picture and Television Engineers (1950-1954)

have become thoroughly accustomed to going through such split-second tactics using only a single iconoscope film camera and multiplexing the information from two projectors, a Telop for opaques, and one or more transparency projectors, onto the iconoscope mosaic in the required sequence by means of mirror and douser techniques. They naturally expect that any improved device such as the vidicon camera will give them the same, or even more, operational flexibility. With the iconoscope, the multiplexing problem is quite easily solved, since the diagonal of the photosensitive mosaic is 5 in. and the projector lens throw for the required magnification from 16mm or 35mm film is about 50 in. This 50-in. working distance is utilized for suitable mirror and projector source locations so that any one of three or more projection devices can be selected at will for program continuity. The vidicon, on the other hand, has a picture diagonal of slightly less than ^ of an inch, giving practically a unity magnification ratio for 16mm film and a 2:1 demagnification for 35mm frames. This consequently gives a lens throw of the order of 7 to 10 in., which is far too small for conventional multiplexing techniques. This, however, works out very conveniently for mounting a camera directly on the projector and gives the possibility of electrically multiplexing the outputs as required by program needs. There seems to be a definite trend in this direction by network originating stations. This technique does not solve the problem for the small broadcaster who cannot afford the increased equipment, personnel and floor space required. A method of multiplexing has been devised and tested which appears to provide an excellent answer. The basis for operation is^the creation of a working distance for accommodation of the required multiple mirrors and projector sources. This is done by projecting a real image in space, whose diagonal is 5 in., and picking up this image with a lens on the vidicon camera itself. A suitable field lens in the 5-in. image plane is used to direct the peripheral rays into the vidicon lens aperture. This technique allows the use of standard high-quality 16mm motion-picture lenses which are available at reasonable cost. A similar application of relay lens techniques has been used in the RCA color camera and has given very good results from the viewpoint of resolution and detail contrast.6 A schematic diagram of the elements of this system is shown in Fig. 5. With a carefully designed optical multiplexing system, the degradations introduced in the television picture by the additional lens process are definitely of second order. If the camera is made as an integral part of the optical system, the effects of projector vibration on image quality are no different from those with the iconoscope and direct projection. These are quite small in commercial operation. Such an optical multiplexer is now in the product-design phase and is arranged to handle two film projectors, 16mm or 35mm, an opaque projector, and a remotely controlled preloaded projector for 2 X 2 in. transparencies. 16mm and 35mm Film Material The question of film quality for television reproduction has been the subject of much study. Even though it is realized that 16mm film has tremendous commercial advantages in first cost, projector cost, storage requirements, air express shipping charges, fire code restrictions, and many other factors, the fact still remains that the best 16mm prints are none too good for television. An equivalent limiting television resolution of over 400 lines with 16mm release prints is rare. This contributes nothing to overall quality. By comparison, 35mm prints on the average have much higher performance from the standpoint of resolution, gray 160 February 1954 Journal of the SMPTE Vol. 62