The use of a random object distribution for the characterization of x-ray focal spots for quality control purposes is described. This technique, utilizing a coherent optical processor, allows for the direct generation of the two-dimensional modulation transfer function (MTF). The distance betwep the first zeroes of the MTF, in the orientation of interest, are then measured to provide an estimation of the x-ray focal spot size. This technique is compared to the conventional pinhole image measurement technique and the failure of resolution (star measurement) technique and is found to produce similar variability and sensitivity to changes in the focal spot size.
J. E. Gray,
"Focal Spot Measurements for Quality Control Purposes Using a Random Object Distribution," Optical Engineering 15(4), 154353 (1 August 1976). https://doi.org/10.1117/12.7971992