| 摘要 |
1,141,857. Image tubes. COMPAGNIE FRANCAISE THOMSON HOUSTON-HOTCHKISS BRANDT. 23 June, 1967 [24 June, 1966], No. 29129/67. Heading H1D. A secondary emission conductivity (SEC) structure serving, for example, as a target in an image-orthicon or as a dynode in an image converter comprises a plurality of layers of porous secondary emissive materials which have, proceeding from the face of the structure receiving the primary electrons, decreasing maximum secondary emission ratios matched to the decreasing residual energies of the transmitted secondary electrons. A two-layer structure may comprise on an alumina-aluminium support a first layer of potassium chloride, potassium bromide, sodium bromide or barium fluoride (high maximum secondary emission ratio and high corresponding accelerating voltage) and a second layer of sodium chloride, lithium fluoride or magnesium oxide (relatively low maximum secondary emission ratio and relatively low corresponding accelerating voltage). A further layer of e.g. silicon monoxide, silicon dioxide or calcium fluoride, may be provided to prevent or retard the emission of secondary electrons by an incident scanning beam when the structure is used in an image orthicon. Suitable dimensions and densities are given for the various layers. |
