Compact in-line interferometer for low-coherence reflectometry

An interferometer with an efficient confocal layout is described. Similar in structure to a folded Linnik microscope, the interferometer employs broadband illumination to improve rejection of out-of-focus light. A prototype reflectometry system based on the new interferometer achieved an axial resolution of less than 10 μm within a probing depth of 1 mm in samples containing particulate scatterers and specularly reflecting objects. Options for mechanical and electronic scanning are discussed.