Xeroradiography - Principles And Practice

Xeroradiography is the technology for recording radiographic images without the need for any chemical processing whatsoever. To make an image a selenium photoreceptor, or plate, is charged to a uniform surface potential on the order of 1000 volts. When this photoreceptor is exposed to x-rays, its surface charge is depleted by photoconduction in amounts proportional to the radiation intensity striking it. A residual potential pattern which is a shadow graph of the object being x-rayed is then formed. After exposure, the electrostatic image on the plate is developed by a powder cloud technique in which charged, pigmented particles are blown over the plate and adhere to it in the pattern of the image. This powder or toner is the ink which defines the image. Following development, the toner is transferred to paper and fixed into a permanent image by low temperature heat fusing. The purpose of this paper is to present the principles of zero radiography, to describe practical equipment utilizing these principles for x-ray imaging in the medical and industrial fields, and to show some examples of the types of images produced by the system.