Theory and performance of the iconoscope

Field tests have shown the present standard iconoscope to be a very satisfactory television pick-up device. However, from a theoretical point of view the efficiency of the iconoscope as a storage system is rather low. The principal factors responsible for the low efficiency are lack of collecting field for photo-electrons, and losses caused by the redistribution of secondary electrons produced by the beam. Limits to the sensitivity of the standard iconoscope are set by the ratio of picture signal to amplifier and couplingresistor ¿noise.¿ Experimental and theoretical determinations indicate that an excellent picture can be transmitted with from 2¿ to 6 millilumens per cm? on the mosaic. Two methods are considered by which the sensitivity may be increased. The first is by the use of secondary-emission signal-multipliers and a low-capacitance mosaic, while the second makes use of secondary-emission image intensification. The sensitivity limits for the two cases are calculated.