VIBRATION-RESISTANT DIRECT-PHASE-DETECTING OPTICAL INTERFEROMETERS

Two dual-beam differential direct-phase-detecting optical interferomet ers for scanning moving surfaces are described. Two beams from these i nterferometers are focused similar to 42 mu m apart on moving surfaces , and the difference in their reflected path lengths is measured to pr ovide the surface roughness measurement. These interferometers are exc eptionally insensitive to environmental vibrations and to surface phys ical and chemical factors. Applications discussed include the measurem ent of the surface roughness of a rotating cylinder and a moving web. (C) 1997 Optical Society of America.