Editing Optical coherence tomography (section)

=== Full-field OCT ===
[[File:Full-field OCT.png|thumb|350px|Schematic view of a full-field OCT]]

An imaging approach to temporal OCT was developed by Claude Boccara's team in 1998,<ref>{{cite journal | vauthors = Beaurepaire E, Boccara AC, Lebec M, Blanchot L, Saint-Jalmes H | title = Full-field optical coherence microscopy | journal = Optics Letters | volume = 23 | issue = 4 | pages = 244–246 | date = February 1998 | pmid = 18084473 | doi = 10.1364/ol.23.000244 | bibcode = 1998OptL...23..244B }}</ref> with an acquisition of the images without beam scanning. In this technique called full-field OCT (FF-OCT), unlike other OCT techniques that acquire cross-sections of the sample, the images are here "en-face" i.e. like images of classical microscopy: orthogonal to the light beam of illumination.<ref>{{cite journal | vauthors = Dubois A, Boccara C | title = [Full-field OCT] | language = fr | journal = Médecine/Sciences | volume = 22 | issue = 10 | pages = 859–864 | date = October 2006 | pmid = 17026940 | doi = 10.1051/medsci/20062210859 | doi-access = free }}</ref>

More precisely, interferometric images are created by a Michelson interferometer where the path length difference is varied by a fast electric component (usually a piezo mirror in the reference arm). These images acquired by a CCD camera are combined in post-treatment (or online) by the phase shift interferometry method, where usually 2 or 4 images per modulation period are acquired, depending on the algorithm used.<ref>{{cite journal |vauthors=Dubois A, Moneron G, Boccara C |year=2006 |title=Thermal-light full-field optical coherence tomography in the 1.2 micron wavelength region |url=https://hal.archives-ouvertes.fr/hal-00520541/file/Dubois-text-original.pdf |journal=Optics Communications |language=en |volume=266 |issue=2 |pages=738–743 |bibcode=2006OptCo.266..738D |doi=10.1016/j.optcom.2006.05.016|s2cid=120323507 }}</ref><ref>{{cite journal |vauthors=Boccara AC, Harms F, Latrive A |year=2013 |title=Full-field OCT: a non-invasive tool for diagnosis and tissue selection |journal=SPIE Newsroom |language=en |doi=10.1117/2.1201306.004933 |s2cid=123478275}}</ref> More recently, approaches that allow rapid single-shot imaging were developed to simultaneously capture multiple phase-shifted images required for reconstruction, using single camera.<ref name="Zurauskas Iyer Boppart p.">{{cite journal | vauthors = Žurauskas M, Iyer RR, Boppart SA | title = Simultaneous 4-phase-shifted full-field optical coherence microscopy | journal = Biomedical Optics Express | volume = 12 | issue = 2 | pages = 981–992 | date = February 2021 | pmid = 33680554 | pmc = 7901320 | doi = 10.1364/boe.417183 | publisher = The Optical Society | doi-access = free }}</ref> Single-shot time-domain OCM is limited only by the camera frame rate and available illumination.

The "en-face" tomographic images are thus produced by a wide-field illumination, ensured by the Linnik configuration of the Michelson interferometer where a microscope objective is used in both arms. Furthermore, while the temporal coherence of the source must remain low as in classical OCT (i.e. a broad spectrum), the spatial coherence must also be low to avoid parasitical interferences (i.e. a source with a large size).<ref>{{cite book |title=Optics in Instruments |vauthors=Boccara AC, Dubois A |year=2013 |isbn=9781118574386 |pages=101–123 |language=en |chapter=Optical Coherence Tomography |doi=10.1002/9781118574386.ch3}}</ref>