Positioning System For Multiple-Slit Array In Digital Radiography

In order to reduce the effects of scatter from the object and those of veiling glare from the image intensifier (I.I.)-T.V. system in digital radiographic images, we have employed a multiple-slit x-ray beam imaging technique. For reconstruction of a final image, a multiple-slit assembly (MSA) was moved under the x-ray tube by a microprocessor-driven stepper motor. The accuracy of the movement was to be kept within ±10 μm with the aid of a shaft encoder. The MSA was moved over the required distance (0.1 mm to 2.0 mm) in 100 msec, corresponding to the time between x-ray exposures. Positional errors as well as construc-tion errors in the MSA contributed to artifacts in the image. We determined that positional errors were kept below the ±10 μm limit; this was confirmed by the size of the artifacts observed in the reconstructed images and by direct measurements of the MSA position with a dial indicator.