image tube

image tube

(image intensifier) An evacuated electronic device that is used to intensify a faint optical image. The beam of light (or near-ultraviolet radiation) falls on a photocathode so that electrons are liberated by the photoelectric effect. The electrons are accelerated by an electric field and may be detected and recorded by a variety of methods. They can be focused on a positively charged phosphor screen so that an optical image is produced, many times brighter than that of the original beam. This image can be directed onto a CCD detector. Alternatively, it can be made to fall on the photocathode of a second image tube and the intensification process repeated. Several image tubes can be linked in this way to form a multistage image tube but the coupling between phosphor screen and subsequent photocathode must be very efficient. The image on the final phosphor screen may then be photographed. The electronographic camera and the IPCS (image photon counting system) use slightly different techniques.

In image converters a beam of infrared or ultraviolet radiation or X-rays is incident on the photosensitive surface. The liberated electrons can then produce a pictorial representation of a ‘nonvisible’ image.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

image tube

[′im·ij ‚tüb]

(electronics)

An electron tube that reproduces on its fluorescent screen an image of the optical image or other irradiation pattern incident on its photosensitive surface. Also known as electron image tube; image converter.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.