Optical Coherence Tomography

An Optical Coherence Tomography (OCT) system uses low coherence interference to measure reflectance versus distance into a material. Light from a semi-broadband source (like a Superluminescent LED) is split into a reference arm (with a fixed mirror) and a sample arm (towards the material to be scanned). The reflected beams from the reference and sample arms are recombined and input to a spectrometer that records the interference pattern vs. wavelength. The periodicity of fringes in the interference pattern is directly related to the depth into the sample material through the Fourier Transform.