The X-ray tube (open or sealed) produces a conic beam of electron that penetrates the object to be analyzed, and a digital signal is interpreted by the 2D detector as a Digital Radiograph image.
The object is positioned on a precision rotational stage and an image is acquired during the rotation at a constant step. The step is usually 0.25 degree to 1 degree (1440 to 360 images). The scan usually covers a rotation of 360 degrees, but for specific applications a limited angle scan can be performed.
From a series of 2D Radiographs and after calibration, the CT reconstruction software provides 3D volume results using Filtered Back-Projection algorithm (Feldkamp). 3D CT data are rendered as voxels (volume element) with three-dimensional resolution from a few micrometers (microCT) to hundreds of micrometers depending on X-ray detector pixel size.
3D volume results can then be exported as:
- 2D CT slices, for high resolution slice by slice inspection, measurements, density analysis, or
- 3D surface model (triangles, point clouds), for Reverse Engineering, Rapid Prototyping, CAD comparison, modeling.
CT brings more data than any other NDT technique available in the industry.
For more information see CT Applications