Quote:
Originally Posted by kf4rca
Iconoscopes once used the offset gun design but it didn't last. Probably due to geometric distortion too.
FWIW I've got a manual for the Sylvania version of this set.
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The iconcoscope had to scan the image side of the mosaic target because the signal was taken capacitively from an opaque metal film on the back of the insulating target. The exception was a straight ultra miniature 2-inch diameter iconoscope, type 5527. I don't know the construction for sure, but I'm guessing it used a transparent or semi-transparent conductive coating so the light could enter through the back of the mosaic support (opposite side of the electron gun). This tube had even worse sensitivity than the studio iconoscopes (which were replaced by the much more sensitive image orthicon over a period of years after WWII).
Hams experimented with the 5527 in the late 1940s and early 1950s until Vidicons became common.