Briefly, OCT uses a low coherence source such as a superluminescent diode laser with a fiber optic based Michelson interferometer.
Custom-written MATLAB code (with simulated data) for computing global coherence (Source code 1), and multitaper spectra and bootstrap CIs (Source code 2) is given in the Supplemental Materials.
The low-coherence source (SLED, center wavelength 750 nm, bandwidth 23 nm) is collimated, made circularly polarized with the polarizer and the quarter wave plate, expanded to overfill the pupil of the objectives and split with a beam splitter cube (BS1).
Psychoacoustic also suggests that temporal and spectral coherence between sources can be used to discriminate between them [9].
The important point is that complete characterization of the origin of these reflectance changes will require the use of short and long coherence length sources.
OCT uses interferometric techniques, in either broadband low coherence light source configuration (time-domain OCT, TD-OCT and spectral-domain OCT, SD-OCT) or swept-source laser configuration (swept-source OCT, SS-OCT), to provide depth gating and a localized measurement of tissue reflectivity.
A low coherence light source is used in OCT systems to obtain a two dimensional image that could reveal optical characteristics of the specimen [ 22].
We have implemented a new CGWS scheme based on a Linnik interferometer with a SLED as low temporal but high spatial coherence light source.
We further want to point out that a short coherence light source is used for illumination, therefore the observed intensity fluctuations are distinct from intensity fluctuations that are observed with long coherence light sources (which were attributed to interferometric oscillations caused by sub micrometer outer segment length changes [ 15]).
As shown in Fig. 1, the system contains a broadband superluminescent diode (SLD, DenseLight, Singapore) with a central wavelength of 1310nm and a spectral bandwidth of 60nm which is used as a low coherence light source.
