ROUGH-SURFACE PROFILE MEASUREMENT USING SPECKLE OPTICAL FREQUENCY-DOMAIN REFLECTOMETRY WITH AN EXTERNAL-CAVITY TUNABLE DIODE-LASER

We describe a speckle interferometer For measuring the two-dimensional surface profile of rough objects using Optical Frequency Domain Refle ctometry with an external cavity tunable diode laser. We show that the resolution available with this system is equal to the synthetic wavel ength that would be obtained with a two-wavelength interferometer, wit h the wavelengths set to the extremes of the laser scan range. We pres ent results obtained on several lest objects which show that with a wa velength scan from 672.4 to 678 nm the technique is capable of unambig uously measuring step heights of the order of several mm, with an accu racy of 40.7 microns.