ABSTRACT
A big step towards spreading the use of computed tomography (CT) in industry was achieved by using a two-dimensional charge-coupled device camera as detector at the output screen of an image intensifier. CT inspections are often too costly or too time consuming in comparison to other non-destructive testing techniques like ultrasound or thermography, which are much easier to use because they are mobile. The surface determined from CT measurements, however, is always close to the average gray-value between the two materials, defining a position between peaks and valleys. A magnified projection can be achieved by different means: zone plates and X-ray lenses in refraction, or single crystal mirrors in small angle reflection. For X-rays, the absolute values of the refraction angles are very small compared to those for visual light. Therefore, the effect can only be seen by high-resolution detectors together with low X-ray energy or large object–detector distance.
