High-speed functional OCT with self-reconstructive Bessel illumination at 1300 nm

We present a Bessel beam illumination FDOCT setup with FDML buffered swept source at 1300nm. An extended focus is achieved due to the Bessel beam that preserves its lateral extend over a large depth range. Decoupling the illumination from the Gaussian detection improves the sensitivity as compared to double passing the ring filter and enables dark field imaging. Dark field imaging is useful to avoid strong reflexes from the sample's surface that adversely affect the sensitivity due to the limited dynamic range of high-speed 8bit acquisition cards. Furthermore, Bessel beams exhibit a self-reconstruction property that allows imaging even behind obstacles such as hairs on skin. Densely sampled volumes of skin in-vivo with high lateral resolution are acquired at up to 440kHz A-Scan rate. In addition the possibility of contrasting capillaries with high sensitivity is shown, using inter-B-scan speckle variance analysis. High-speed imaging is of crucial importance for imaging small details since sample motion artifacts are reduced and high sampling can be maintained while increasing the B-Scan rate.