Photo-element with light guide exploiting photoelectric effect - has vacuum space between alkali metal coated rod and anode formed by outer tube

摘要

The photo element which may incorporate a light guide (1) consisting of a glass rod, can be shaped as a quarter of a circle. This is coated with e.g. an alkali metal (3) forming an electron emitter surface, and housed inside a tube (4) which can be connected to a voltage source (6) so as to act as an anode. Between the anode tube and the rod is an evacuated space (2) forming a vacuum chamber which is closed by a seal (5) at each end, of non-conductive material. When a light beam (15) enters the rod, electrons are released from the coating (3) which are totally reflected through the rod, giving a voltage across the positive (6) and negative (7) connections at the outer end. An alternative design uses one or more wave shaped light guides.