Meaning
Technical thresholds define the smallest distance between two distinct objects that an imaging system can reliably detect as separate entities. The spatial resolution limit is determined by a combination of the source size and the detector pixel pitch. It sets the boundary for the level of detail that can be extracted from a three-dimensional scan.
In industrial metrology, knowing this limit is essential for ensuring that the system is capable of detecting the smallest flaws required by the quality specification.
Feature Discernment
Visibility of a defect depends on it being larger than the spatial resolution limit of the scanner. If a crack is smaller than this threshold, it will appear as a faint blur or may not be seen at all. Engineers must select an imaging system with a resolution that is at least twice as fine as the smallest feature they need to measure.
Hardware Constraint
Improvements in resolution are often limited by the physical properties of the X-ray source. A smaller focal spot allows for a finer spatial resolution limit but also reduces the intensity of the beam, leading to longer scan times. Modern systems use nanofocus tubes to achieve sub-micron resolution for the inspection of microchips and precision electronics.
Sampling Interval
Distance between the pixels on the detector also plays a role in defining the final image quality. According to the nyquist theorem, the spatial resolution limit cannot be better than twice the effective pixel size. Increasing the magnification can help overcome detector limits but reduces the overall size of the part that can be scanned in a single pass.
