Photoconductor-electroluminescent type image intensifiers in sandwich construction

From both theoretical and technical considerations, the construction of a photoconductor-electroluminescent (PC-EL) type image intensifier in a layer-on-layer or sandwich mode is the most ideal. However, due to the high capacitance and the insufficient sensitivity of the PC layer, it was difficult to achieve acceptable characteristics, and therefore solid state image intensifiers were fabricated only in more complicated structures. Recently, two developments helped to considerably improve the characteristics of the sandwich type image intensifiers. One development was that of plastic materials with dielectric constants as high as 25, which could be used for the embedment of the EL phosphor, and offered high capacitance with higher brightness. The other improvement was the increasing of the volume-sensitivity of CdSe sintered layers. Thus image intensifiers were made in the simple construction with maximum "standard luminous gains" of 100 ft-L per ft-c, resolution of 100 to 200 TV lines per inch, and maximum output of 30 ft-L at 200 volts and 2000 cps. The size of the panels was 6" × 6", but larger sizes probably could be constructed without facing new problems. These panels can be used also as infra-red to visible image converters, and x-ray image intensifiers. Details of the fabrication and characteristics will be presented and discussed.