Optical Heterodyne Profilometer

An optical heterodyne profilometer breadboard as been developed and demonstrated with surface roughness measurement sensitivity to 0.1 A. Optical and electronic common-mode rejection techniques were employed in the optical heterodyne precision phase measurement scheme to resolve the optical phase to one part in thirty thousand. Vibration-induced optical phase jitter in the system was nearly eliminated by these common-mode rejection techniques. This non-contact profilometer is capable of characterizing mirror surfaces not limited only to flat and/or highly reflective surfaces. Concaved surfaces such as the x-ray mirrors for the Advanced X-ray Astrophysical Facility (AXAF) may be characterized as well. Several mirror samples have been characterized with the optical heterodyne profil-ometer which include two x-ray mirror samples. Roughness measurement results on the x-ray mirror samples have been compared with those measured by other methods.