10 - Pickup Tubes and Solid-state Cameras

Abstract

This chapter discusses pickup tubes and solid-state cameras. In the 1930s, work started on the development of target materials with photoconductive properties in which the electrical resistance changes with exposure to light. This means that a current flowing through the target from an external source is controlled by incident illumination so that very high photo- efficiencies can be obtained. Tubes are manufactured for different applications to various specifications and mainly in the sizes. They are available in basic forms or with combined features such as act and bias lighting, dbc with loc and bias lighting, and with different resolution characteristics. They are also graded for optimum performance in any of the luminance, red, green, or blue camera channels. A plumbicon target consists of the optically flat tube faceplate with a transparent conducting film of stannic oxide on the inside, connected to an external signal electrode. Next is a photoconductive layer of lead monoxide deposited on the conductive film. The inner or scanned surface of the lead monoxide is doped to form a p-type semiconductor and that close to the faceplate is doped to form an n-type semiconductor. A particular method often used by tube manufacturers for specifying the sensitivity of tubes refers to luminance for a monochrome camera or red, green, and blue for the separate channels of a color camera.