METHOD FOR DETERMINING DEFECTIVE FOCUS SIZE IN X-RAY INSPECTION APPARATUS

PROBLEM TO BE SOLVED: To provide a method for determining an effective focus size that readily and objectively enables measurement of the effective focus size in an X-ray inspection apparatus, using a microfocued X-ray tube and the like. SOLUTION: First, a sample 2b, which has at least a first pattern 20 of a first line width (S1), that is located along a first direction X and a second patter 22 of a second line width (S2), that is located along a second direction Y which is orthogonal to the first direction X and is different from the first line width, is set in the X-ray inspection apparatus. Then, an enlarged image of the sample 2b on an X-ray inspection face in an X-ray image sensor is detected, and the first line width of the enlarged first pattern is set as a first line width (L1) and the second line width of the enlarged second pattern as a second line width (L2) after their enlargement respectively. Subsequently, the effective focus size (F) in an X-ray source is found from the equation (8): F=(L1.S2-L2.S1)/(L2-L1)...(8).