Verfahren zur Bestimmung einer vorgegebenen Eigenschaft einer Probe eines Materials

Measurements are made on a sample (1) to obtain an experimental profile (2) having structural features (3, 4) determined at least in part by the given characteristic and an expected profile (5) calculated for the sample using selected parameters. A degree of smoothing is applied to the experimental profile (2) to reduce the structural features (3,4) thereby producing a smoothed experimental profile (21a) and the same degree of smoothing is applied to the calculated profile (5) to produce a smoothed calculated profile 51a. The smoothed calculated profile (51a) is compared with the smoothed experimental profile (21a) to determine the difference between the smoothed profiles. The calculated profile is then modified by varying at least one of the parameters until the smoothed modified profile fits the smoothed experimental profile. The above steps are then repeated with the modified calculated profile using each time a degree of smoothing less than the previous time so that the structural features return and the final modified calculated profile (5b) provides a desired fit to the experimental profile (2) thereby enabling the given characteristic to be determined from the parameters used for the final modified profile.