OPTICAL FIBER DISPLACEMENT SENSORS FOR PROCESS AND MANUFACTURING APPLICATIONS

We describe three novel optical fiber probes, all based on the focused-beam reflective principle, to measure displacement, form, and surface topography, respectively. Each depends on deriving twin displacement/optical output characteristics that may be resolved by difference/sum referencing. The displacement sensor adopts two-wavelength operation using a zone plate to give opposing displacement/output characteristics. The device is noncontacting, and a resolution of better than 0.1% of span is anticipated. A 3-D optical touchprobe has been built for use with coordinate measuring machines. A mathematical model has been generated that relates output to stylus movement, and the model has been verified experimentally. A resolution of 0.1-mu-m in the x-y plane and 1.0-mu-m in the z direction is achievable. A further noncontacting probe has been developed for the measurement of surface topography whose output shows low dependency on surface reflectance. A mathematical model has shown good correspondence against a wide range of surface compositions and textures; a resolution of better than 1-mu-m is foreseen. Proposals are made for industrial implementation of all three probes.