"Extended focus high-speed swept source OCT with self-reconstructive illumination"Cedric Blatter, Branislav Grajciar, Christoph M. Eigenwillig, Wolfgang Wieser, Benjamin R. Biedermann, Robert Huber, and Rainer A. Leitgeb
Optics Express, Vol. 19, Issue 13, pp. 12141-12155 (2011)
We present a Bessel beam illumination FDOCT setup using a FDML Swept Source at 1300nm with up to 440kHz A-scan rate, and discuss its advantages for structural and functional imaging of highly scattering samples. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Decoupling the illumination from the Gaussian detection increases the global sensitivity and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the sample surface that adversely affect the sensitivity due to the limited dynamic range of high speed 8bit acquisition cards. In addition the possibility of contrasting capillaries with high sensitivity is shown, using inter-B-scan speckle variance analysis. We demonstrate intrinsic advantages of the extended focus configuration, in particular the reduction of the phase decorrelation effect below vessels leading to improved axial vessel definition.
BMO authors (in alphabetic order):
Fourier Domain Mode Locking (FDML): Spectral mode locking in optics and applications
Optical Coherent Ranging and Optical Coherence Tomography (OCT): Imaging and profilometry with rapidly frequency swept laser sources