Profilometry of toroidal surfaces with an improved Ronchi test

An implementation of the well-known Ronchi test technique, which allows for the profilometric measurement of nonrotationally symmetrical surfaces, is presented and applied to the measurement of toroidal surfaces. Both the exp erimental setup and the data-processing procedures are described, and param eters such as the radius of curvature of the sample surface, the orientatio n of its principal meridians, and the position of its vertex are measured b y means of the values of the local normal to the surface obtained at a set of sampling points. Integration of these local normal values allows for the reconstruction of the three-dimensional profile of the toroidal surface co nsidered with micrometric accuracy, and submicrometric surface details may be calculated by use of surface-fitting procedures. The density of sampling points on the surface may be tailored to fit test requirements, within cer tain limits that depend on selection of experimental setup. (C) 2000 Optica l Society of America. OCIS codes: 120.6650, 120.4630, 120.4800, 120.3930, 1 20.4290.