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Mr. Ramsay: Also, could you explain what causes the good signal-to-noise ratio of this tube?
Mr. Neuhauser: The good signal-to-noise ratio is produced merely by the fact that you can get a high signal out of the tube. It produces about three to four times the signal that you get out of an iconoscope operated at 0.1 -jua beam current, which is the value we recommend for the iconoscope.
Mr. Ramsay: Would not the signal-tonoise ratio of the iconoscope be equally as good if operated at the same illumination as is recommended for the vidicon?
Mr. Neuhauser: Not unless the beam current of the iconoscope were increased above the recommended value of 0.1 jua. Such an increase in beam current unfortunately produces uncontrollable flare or background variations as the result of excess secondary electrons falling back on the mosaic of the iconoscope.
Frank N. Gillette (General Precision Labora
tory): You mentioned that the vidicon performed recently with shutter impulses of as little as 30% illumination duty cycle. Other workers in that field have reported the necessity of a taper on the rise and fall of the light beam when the duty cycle is as low as 30%. Do you confirm that result?
Mr. Neuhauser: I have a projector that has about a 25% application time square application pulse and I have not been aware of any application bar. As viewing gets more critical you may find that there has to be a tapered-light application. At present I would say it does not require a tapered shutter or a graded shutter.
Mr. Ramsay: You gave a figure on the number of seconds for storage time on this tube. Would that figure also hold for the 6198?
Mr. Neuhauser: I think it would, yes.
Mr. Ramsay: And that is storage time for an unscanned tube?
Mr. Neuhauser: Yes.
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February 1954 Journal of the SMPTE Vol. 62