One-Dimensional Surface Profilometer Based on the Heterodyne Angle Deviation Interferometry

We propose heterodyne angle deviation interferometry (HADI) to measurethe surface profile in real time. A beam incident into a lens’ marginaland reflected from a sample and then finally passing through to the lens isparallel to the optic axis when the sample is just located on the focal plane.When the sample’s surface departs from the focal plane, the reflectionbeam deviates a small angle from the optic axis which is proportional to thedefocus length. We use the common-path heterodyne interferometer (CPHI)with a surface plasmon resonance (SPR) angular sensor to measure the deviationangle by the phase presentation. From the phase difference to surfaceheight transformation and scanning the surface, the one-dimensionalsurface profile is plotted. The measurable range is of 2.5 mm with thelateral resolution of 10 m and the best vertical resolution is of 12 nm.