We report and explain anomalous results obtained when using small core optical fibers to probe the distance to some scattering surfaces, such as machined metal surfaces. Large intensity variations occur when different sections of the surface are probed at constant distance. This is explained using a model which includes ray tracing and reflection from a surface structure exhibiting a variable surface normal vector. When the collection fiber size is increased, a larger portion of the reflected light field is sampled, and the signal intensity variations weaken.
© 2012 Optical Society of AmericaPDF Article