Image reading: Conversion to digital signals

Abstract

An X-ray image stored on the IP is spatially continuous analog information, and the laser scanner, shown in Fig. 3.1, is used to read the information and convert it into digital signals. By scanning the converged laser light with a vibrating or polyhedral rotating mirror in a direction perpendicular to that of the scanning light, while precisely transferring the IP, it is possible to scan two-dimensionally all side of the IP one after another with a laser light spot. The photostimulated light excited by the laser light spots is directed to the photomultiplier tube by the high-efficiency light guides located along the scanning line of the laser light to be converted to electric signals. The electric signals thus converted are analog signals proportional to the amount of photostimulated light emission. They are properly amplified and logarithmically converted to pass through the A/D converter to become digital signals.