Image converter having cylindrical housing and photocathode separated by spacing element from luminescent screen on frustrum

摘要

An image converter is disclosed which can be operated by means of a relatively low voltage D.C. supply. In this invention, the luminescent screen of the image converter is brought closer to the photocathode by forming the exit window with a frustrum-shaped platform with a top surface that is parallel to the entrance window, and upon which top surface the luminescent screen is mounted. As a result of the closer spacing between the photocathode and the luminescent screen, lower D.C. supply voltages can be utilized. Moreover, the shape of the housing which supports the two windows at the image converter is so designed that the interior surface of the housing is non-perpendicular to the equipotential lines of the electric field which is established between the photocathode and the luminescent screen. As a result of this geometrical relationship, avalanche discharge is reduced or eliminated altogether, thereby reducing or eliminating the undesirable arcing which can occur as a result of such avalanche discharge. Embodiments are taught for amplification of projected images in the visible portion of the electromagnetic spectrum, along with embodiments which can be utilized to form images of radioactive radiation, X-ray radiation and ultraviolet radiation.