METHOD OF DETERMINING SHAPE ERROR OF FREE-FORM SURFACE

摘要

The principal curvatures in the corresponding positions of an object curved surface S' and a reference curved surface S are determined and the respective regions are classified into the following three categories in accordance with the difference between the principal curvatures; i.e. (a) regions where both of the principal curvatures increase, (b) regions where both of the principal curvatures decrease, and (c) regions where one principal curvature increases while the other decreases. The regions (a), (b) and (c) are judged to be mount, valleys and twists respectively and are displayed by different symbols or colors on a display screen. Thus it has become possible to recognize the different regions of the two three-dimensional shapes properly, to find the causes of errors such as partial bend, to express the extent of agreement between the two shapes by objective numerical values, and to discriminate shape errors even if the reference shape is complicated.