Coherence scanning interferometry

Coherence scanning interferometry (CSI) is any of a class of optical surface measurement methods wherein the localization of interference fringes during a scan of optical path length provides a means to determine surface characteristics such as topography, transparent film structure, and optical properties. CSI is currently the most common interference microscopy technique for areal surface topography measurement.^[1] The term "CSI" was adopted by the International Organization for Standardization (ISO).^[2]

Characteristic CSI signal

The technique encompasses but is not limited to instruments that use spectrally broadband, visible sources (white light) to achieve interference fringe localization. CSI uses either fringe localization alone or in combination with interference fringe phase, depending on the surface type, desired surface topography repeatability and software capabilities. The table below compiles alternative terms that conform at least in part to the above definition.

Acronym	Term	Reference
CSI	Coherence scanning interferometry	[3]
CPM	Coherence probe microscope	[4]
CSM	Coherence scanning microscope	[5]
CR	Coherence radar	[6]
CCI	Coherence correlation interferometry	[7]
MCM	Mirau correlation microscope	[8]
WLI	White light interferometry	[9]
WLSI	White light scanning interferometry	[10]
SWLI	Scanning white light interferometry	[11]
WLS	White Light Scanner
WLPSI	White light phase shifting interferometry	[12]
VSI	Vertical scanning interferometry	[13]
RSP	Rough surface profiler	[14]
IRS	Infrared scanning	[15]
OCT	Full-field optical coherence tomography	[16]