Refocused Optical Profilometer With Telecentric Scanning for Reliable Height Measurements
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
The Refocused Optical Profilometer (ROP) is a device developed for noncontact measurement of magnetic tape pancake profiles. (A pancake is defined here as a large reel of tape.) It utilizes a focused HeNe laser beam which is telecentrically scanned across the pancake surface by a galvo mirror. The specularly reflected and divergent laser beam is refocused by two separated cylindrical lenses which provide imaging in two perpendicular planes. In the vertical plane (i.e., plane of incidence), the first cylindrical lens images the pancake laser spot onto the position sensor. This ROP arrangement is shown to be able to detect height variations at the pancake surface, independent of local gradient, curvature, or reflectivity. The schematic layout of ROP is indicated in Fig. 1, and the operation principle outlined in Fig. 2.