In general, X-ray inspection systems consist of a radiation safe enclosure, the radiation protection cabinet, containing, in linear alignment, the X-ray tube, and the X-ray detector. A remotely controllable manipulating unit allows the user to position the sample within the beam. The final X-ray image is displayed on a monitor for computerized image processing. In addition, the X-ray system may be outfitted with an electronic program control allowing automated sample inspection. The X-ray image shows object features based on differences in material density.
Part of the X-ray spectrum is absorbed when passing through an object. The thicker or higher in density the object, the more X-rays are absorbed and do not pass through. Those X-rays that pass through the object strike a detector where an X-ray image is created. This image is made up of different shades of gray depending upon the intensity of the incident rays: Parts of the object that are thicker or materials that are higher in density, such as iron, copper, and lead, appear darker than less dense materials such as plastics, paper, or even air.
This film is then processed in a darkroom - much like typical photographic film - and the various degrees of radiation captured by the film are represented as different values of white and black. X-rays not absorbed by the target sample will cause exposure of the radiographic detector. These areas will appear dark. Areas that absorbed higher levels due to higher absorbing or more dense material will appear light.
In this way, regions of your target sample where uniform density has been changed by imperfections, such as porosity, cracks, or misalignment will appear as dark lines, thus making it easier for a skilled technician to detect.