LIGHT SECTIONING WITH IMPROVED DEPTH RESOLUTION

Light sectioning of an object surface uses the line deformation imaged by a CCD camera to compute the object profile. Because of the low optical magnification between the object and the CCD image plane, the measured CCD line deformation is small and leads to low resolution in profile measurements. To obtain larger CCD line deformation without decreasing the field of view, we propose to use an additional cylindrical lens to magnify only the horizontal deformation (which contains the profile information) without modifying the vertical field of view. The limitations of this anamorphic system, such as maximum object depth and magnification, are theoretically determined. The improvements given by the cylindrical lens are calculated, and experimental profiles (pyramid, cylinder) show a gain in depth resolution of approximately 2 to 3 over an earlier light sectioning system. The depth resolution, which was 0.36 mm with the previous system, is now improved to 0.15 mm for an average object distance of 350 mm.