A plug-type image orthicon target

The conventional image-orthicon glass target, because of the ionic nature of its conduction, has a limited useful life and very restricted range of operating temperature. In addition, its resolution at low light levels suffers due to its insufficient lateral resistance. A new structure-type target has been developed which is essentially free of these limitations. It consists of an array of metal plugs embedded in an insulating film of aluminum oxide. Several image-orthicons containing such targets, in a 750- or 1000-mesh pattern, have been made. These tubes show very little or no image retention ("sticking"), initially or after extended operation, and operate in a wide range of target temperatures so that no warm-up period is required. Due to the high resistance between elements, the plug-type target can store a high-resolution picture for a longer time than is the case with-glass targets. Camera tubes containing plug-type targets are expected to have greatly extended life, operate ina wide temperature range and are particularly useful for viewing low-light level scenes, possibly at reduced scanning rates.