Spectroscopic spectral domain interferometry and spectroscopic optical coherence tomography combine depth information with spectrally-resolved localised absorption data. These additional data can improve diagnostics by giving access to functional information of the investigated sample. One possible application is measuring oxygenation levels at the retina for earlier detection of several eye diseases. Here measurements with different hollow glass tube phantoms are shown to measure the impact of a superficial absorbing layer on the precision of reconstructed attenuation spectra of a deeper layer. Measurements show that a superficial absorber has no impact on the reconstructed absorption spectrum of the deeper absorber. Even when diluting the concentration of the deeper absorber so far that an incorrect absorption maximum is obtained, still no influence of the superficially placed absorber is identified.
Spectroscopic optical coherence tomography (SOCT) combines the imaging capability of optical coherence tomography
with spectroscopic absorption information. SOCT requires a large bandwidth combined with a broadband spectrometer,
due to the processing of the measured data, which includes dividing the spectrum in spectral bands. Both, spectral and
axial resolution of SOCT depend on the spectral width of each window. A supercontinuum source with its broad
spectrum allows a sufficient number of windows combined with a reasonable axial resolution, which depends on the
application.
Here a SOCT system is used in the visible spectral range from 480 to 730 nm by combining a supercontinuum light
source, a Michelson interferometer and a commercial available broadband spectrometer. This wavelength range is
chosen because it covers a range of useful absorbers, including that of human proteins. The system is tested with a laser
dye rhodamine B for calibration and verification. Rhodamine B has an absorption peak at around 542 nm, which
resembles the absorption spectrum of several proteins in the globin group. The results show that the absorption spectrum
of rhodamine B can be reconstructed with sufficient accuracy and demonstrate that varying spectroscopic information
can be retrieved from different depths.
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