Phototimer for automatic control of x-ray exposure, PT-20A

The phototimer as an exposure control device is now required to have higher accuracy and wider range of control to comply with the recent trends of X-ray diagnosis, such as toward short-time exposure due to increased output power of X-ray apparatus and toward one-man operation. In order to meet the requirement, the X-ray characteristics of the components of the phototimer have been examined, and computer simulation of X-ray spectra and dynamic characteristics of every component have been investigated, in pursuit of the essential characters of phototimers. On the basis of these analytical investigations, the phototimer PT-20A is so designed as to compensate for density deviation under various kVp and object thickness: uniform density has been obtained under practical radiographic conditions. (author)