Laminography and tomosynthesis
Laminography is well suited for flat objects
In the case of laminopgraphy the investigation and reconstruction is performed in layers predominantly on flat objects which are not accessible from all sides. The process can be divided into:
- Translational laminography: Here the object between the X-ray source and detector is slide through. Due to the lateral displacement, the interior can be reconstructed in three dimensions.
- Rotary laminography: In this case X-Ray source and / or detector rotate above and below the object. With the information obtained from the different angles of incidence, the object can be reconstructed in three dimensions.
What are the advantages of laminography?
- Generating of depth information without generally access
- Possibility of a section-CT
How laminography and computed tomography differ from each other ?
Computed tomography (CT) acquires between 200 and 2000 projection images while rotating the object about 360 °. The object is X-Rayed perpendicular to the axis of rotation. The subsequent reconstruction of the projection images provides a three-dimensional volume.This volume can be viewed from any direction and any virtual section can be applied.In laminography X-ray source and detector move 180 degrees dephased on circular paths around the same axis. On the detector a tilted image (eg, 45 °) of the object is always visible. In this way, for example, 8 to 30 images are taken at regular angular intervals. By this inclined porjections with the same angel but different views of the object are optained. When these images are suitable superimposed, one obtains disk images of the object perpendicular to the axis of rotation. A common method of calculation for this is called tomosynthesis. It is also possible to obtain three-dimensional images, but in the vertical direction they may have very strong artifacts (distortions / spurious pseudo structures). Thus appear, for example, spheres as a kind of double cone and are often details (eg searched defects) of the investigated sample exceeded or hidden.In direct comparison computed tomography provides significantly better results than the laminography. This is causally related to the fact be attributed to the complex mathematical method of computed tomography. CT have the aim to provide an exact reconstruction of the object, whereas the laminography based on the method of blurring tomography.