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ENGSTROM, BEERS, AND' BEDFORD [J. S. M. P. E.
is projected upon the photoemissive mosaic either continuously or during the entire scanning period. It is natural, therefore, that investigations of the latter type of system should have been made. So far, the results obtained have not been wholly satisfactory and certainly have not been as excellent as those produced by the storage method described in the previous section. However, refinement of certain projection methods may at some time in the future make other systems of greater interest. It is, therefore, of value to digress and
review some of the various schemes that have been investigated.
For obtaining a continuous and constant light image on the Iconoscope photoemissive mosaic, a commercial type of theater projector was used, hi which the film passed the picture gate at constant speed and a stationary projected image was obtained by means of an "optical intermittent." This projector employed several rocking mirrors on a rotating wheel. The lens system was properly proportioned for the projection of the small image required for the Iconoscope mosaic plate. In testing this system it was noted that the television performance was limited by various types of movement in the projected optical image and by low resolution. Motion of the optical image, hi addition to causing objectionable motion in the received television picture, also contributed to loss of resolution in the picture. This is due to the storage action of the Iconoscope whereby the signal derived from each element of the mosaic in scanning is due to the summation of all the light that has fallen on that element since the preceding contact of the scanning beam. The effect is similar to that obtained when the optical image on a sensitized photographic plate moves during exposure.
FIG. 5. RCA 35-mm sound motion picture projector; 30 frames per second, interlaced scanning.