Meaning
Computational techniques in industrial computed tomography compensate for the preferential absorption of lower-energy photons as a polychromatic X-ray beam traverses an object. Without beam hardening corrections, reconstructed images exhibit artifacts such as cupping, where the center of a uniform cylinder appears less dense than its periphery, and streaks between high-density regions. These mathematical adjustments recalibrate the transmission data based on material thickness and density to restore the true linear attenuation coefficients across the scan plane.
The correction is limited to materials whose elemental composition and density profile can be approximated by known attenuation curves.
Calibration Process
Linearization methods represent a common implementation that utilizes physical reference measurements. Operators acquire transmission profiles through varying thicknesses of a known material to establish a non-linear relationship between material path length and measured attenuation. This empirical calibration transforms the polychromatic intensity values into monochromatic equivalents, resolving density distortion before 3D reconstruction begins.
The cost of failing to perform this calibration correctly is the propagation of structural dimensioning errors during parts inspection.
Algorithm Execution
Iterative reconstruction algorithms integrate the correction directly into the projection-backprojection loop rather than relying on pre-calculated lookup tables. The software models the polychromatic source spectrum and the material’s energy-dependent attenuation characteristics to simulate projections of the current volume estimate. Discrepancies between these simulated projections and the actual measured data are minimized across successive iterations, which reduces edge streaking around high-attenuation components.
This approach demands substantial computational time, representing a critical trade-off against throughput.
Result Assessment
Quality control protocols measure the success of the adjustment by scanning reference cylinders and checking for flat density profiles across the diameters.
