Noncontact surface profiling using optical interferometric microscopy

We report the use of noncontact optical interferometric microscopy for surface topographic profiling. A Linnik optical configuration is used to create interferograms of an object's surface. When the coherence condition between the two beams is met, the phase information of the object's surface can be extracted to establish its topographic contour image. Using four π/4 phase-shifted images, with the synchronization of a piezoelectric actuator reference mirror positioning, the present single camera optical interferometric microscope can reconstruct a surface topography with a field of view of 312 μm×234 μm, axial resolution of 3.31 nm, lateral resolution of 488 nm, and maximum topography height of 270 nm.