FLUORESCENT X-RAYS FILM THICKNESS MEASURING METHOD

PURPOSE:To allow high speed automatic determination of the measuring position of sample by observing variation of the intensity of fluorescent X-ray accumulated at respective positions while scanning a fine sample by means of primary X-ray and then comparing the observed value with a predicted value. CONSTITUTION:X-shift mechanism in a table shift mechanism functions not to irradiate a sample 7 with a primary X-ray beam 16 but to irradiate the periphery thereof. Entire system is then operated to perform scanning with the beam 16 and the intensity I0 of fluorescent X-ray at an irradiation starting position X0 on the material per unit time is measured in order to calculate a statistic error IE. The mechanism 10 then moves the sample 7 to the right and left and begins to accumulate the intensity of fluorescent X-ray due to irradiation of the beam 16. A position where the accumulated intensity Ix does not match with a previously calculated current predicted accumulated intensity ICx is determined as the position of the sample 7. This method allows high speed and positive search of the position of a sample 7 even when the speed of the beam 16 is increased.