Evaluation of a Computer Aided X-Ray Fluorographic System. Part 1: System Analysis

摘要

A computer aided, X-ray fluorographic (CAF) system has been assembled for application in non-destructive testing. The fluorographic hardware comprises a rare earth phosphor viewed with a low-light level SIT (silicon intensifier target) TV camera. This is a robust, adaptable and relatively low cost combination, suitable for real time imaging in an industrial environment. The important addition of the digital image processor allows integration to reduce noise and hence increase the thickness sensitivity of the system. Measurements of the resolution of the system and the noise on the fluorographic images are presented. The modulation transfer function (MTF), which gives a comprehensive description of resolution, has been measured for the complete system and for the optical imaging components alone. These data show that for the highest resolution phosphor used a 10% MTF at 4 cycles/mm can be achieved when a specimen area of width less than 50 mm is imaged. For larger areas the TV camera limits the resolution so that lower resolution, but more sensitive, phosphors can be used without loss of image quality. Higher resolution for the larger areas would be available with a larger format TV camera tube.