METHOD OF MEASURING SECTIONAL SHAPE AND A SYSTEM THEREFOR

A method and system for measuring sectional shape to system the sectional shape of a subject on a plane that includes a direction that couples light sources or detectors, relying upon intensities of the same subject taken or irradiated from one direction wherein a calculation is carried out using a function that is not affected by the change of surface material of the subject in order to find a gradient component of a surface element in the direction which couples the light sources or the detectors, and the sectional shape of the subject on a plane that includes the direction coupling the light sources and the surface element, is determined relying upon the gradient component, making it possible to correctly obtain the sectional shape even when there exist different materials on the subject. Distortion in the measured result caused by the shadow of the surface topography is corrected by repeating the procedure; i.e., (1) estimating the shadow produced by the calculated sectional shape, (2) estimating the signals of when the shadow is removed, and (3) calculating the sectional shape from the signals from which effect of the shadow has been removed. Therefore, the sectional shape is obtained correctly even when there exists great unevenness on the surface of the subject.