where Bb is the background brightness and Bf
is the brightness of the flaw indicator pattern.
Formulas (3) and (4) determine the brightness contrast of the flaw indicator pattern. The maximal
value of Ko approaches unity, while the coefficient of the method sensitivity Km approaches two.
The difference in formulas (3) and (4) is due to the fact that the direct brightness contrast of the flaw
pattern (the pattern brightness is higher than that of the background) is observed during luminescence
inspection, while the opposite contrast (the pattern brightness is higher than that of the background) is
observed during penetrant inspection. Following the proposal of A.S. Borovikov, the concepts of the “geo
metric parameter of an indicator pattern” and the “optical parameter of an indicator pattern” were
entered into the state standard