Determination of Probability Distribution Function of Optical Density in Industrial Radiographic Films by X-Ray

In this paper, the optical density distribution function obtained from the radiographic films at the voltages of 80-150 kV was investigated. Steel plates of 30×30 mm2 with thicknesses of 2 and 8 mm were irradiated according to the European standards with different currents at various times. The information of the radiographic films was converted into 8-bit numeric data by using a laser scanner with a resolution of 3200 dpi. The histograms obtained from these scans were compared with all applicable probability functions. Due to the large number of the employed probability functions, their compatibility was first assessed on the best and simplest histogram. Afterwards, the selected functions were used for the remaining films. In this way, the best probability distribution function was determined. The same steps were taken for radiographic defects. Furthermore, the degree of adaptation of the probability distribution functions applied to the base metal and the defects regions was also evaluated.