Technikatörténeti szemle 20. (1993)

TANULMÁNYOK - Tihanyi Glass, Katalin: The Iconoscope: Kalman Tihanyi and the Development of Modern Television

For the increase of the local capacity of individual photoelectric cells he proposes an image carrier — either bar bundle type or a composite screen — which is a triode, consisting, at the transmitter, of a positively charged control grid mounted on a glass or lacquer insulation layer; photosensitive layer, and platinum collector electrode. At the receiving side, the luminescent screen is also connected to a control grid and is applied onto a micanite insulating layer. Both the grid electrode and the partially conducting mica layer serve to increase electron emission, while both allow continuous electron flow and resulting storage of accumulated charges continuing during the scansion period between discharge by the cathode ray beam. This storage action, then, occurs both at the transmitting and the receiving side (30). As mentioned above, single-sided operation was introduced In the inventor's 1928-1929 applications. In addition to this, in these applications, particularly in his second patent specification, British patent No. 315, 362, (and U.S. patent application, serial no. 377. 261) frequently omitted from the literature, the inventor describes various proposals for mosaic screens (targets) utilizing the photoconductive and photovoltaic effects. Most likely, these proposals constitute the basis of further improved iconoscopes Including the vidikon, the transmitting tube representing photoconductive and photovoltaic technology. On page 7 of the British patent specification here is how the inventor introduces the description of these devices: „ln Fig. 34 to 40 various transmitting tubes with photo-ohmic image carriers are shown. In a photo-ohmic image carrier substances are used which change their electric conductivity when acted on by light. The reaction inertia of these substances is not detrimental as the whole picture is projected onto them at the same time and the Individual points of the projected picture act on the photo-ohmic layer for a relatively long time, for instance 1/30 of second". Characteristic for the wealth of the material, i.e. the number of innovations included in this application, is the request from the U.S. Patent Office for its division into six patents (31). Aside from the many different constructional forms of photoelectric, photo-ohmic, photo-ohmic grid, transparent and light-sensitive crystal image carriers for both single-sided and two-sided operation, it describes at least seven means for picture intensification, including self-increasing, multi-stage and secondary picture intensification. In light of this — and, as we will see, Zworykin's knowledge of Tihanyi's