ABSTRACT
The history of photoconductive camera tubes using the internal photoelectric effect began in 1950 with
the Vidicon camera tube [1]. A photoconductive camera tube performs both photoelectric conversion
and signal storage on a photoconductive target, which is a vapour-deposited film of Sb
S
in Vidicon
tubes. Although the Vidicon tube boasts a simple, small and lightweight structure compared with the
Image Orthicon tube that used the external photoelectric effect, it also suffers from several weak points
such as large lag and dark current. The Vidicon, as a result, has not found much use in broadcasting-type
television cameras that require high levels of picture quality. These weak points stem from the fact that
excited carriers are easily trapped in Sb
S
deposited film and that charge is injected into the target from
an external electrode (injection-type target). On the other hand, the Plumbicon camera tube announced
in 1963 features a target formed by a PbO film with a p-i-n structure that blocks the injection of charge
from an external electrode (blocking-type target) [2]. With this type of target, the Plumbicon became the
first photoconductive camera tube to feature low lag and low dark current among other superior
features. In the 1970s, the Plumbicon rode the wave of change to colour television broadcast facilities
and became the leading tube for broadcast-class colour television cameras replacing the Image Orthicon
tube that used the external photoelectric effect. The research and development of photoconductive
camera tubes had been quite active. The 1970s, for example, saw the back-to-back development and
commercialization of various blocking-type photoconductive camera tubes including the Chalnicon
using CdSe, CdSeO
and As
S
as targets [3], the Saticon using Se-As-Te [4, 5].
