Phase-resolved Doppler optical coherence tomography (PR-D-OCT) is a functional OCT imaging technique that can
provide high-speed and high-resolution depth-resolved measurement on flow in biological materials. However, a
common problem with conventional PR-D-OCT is that this technique often measures the flow motion projected onto the
OCT beam path. In other words, it needs the projection angle to extract the absolute velocity from PR-D-OCT
measurement. In this paper, we proposed a novel dual-beam PR-D-OCT method to measure absolute flow velocity
without separate measurement on the projection angle. Two parallel light beams are created in sample arm and focused
into the sample at two different incident angles. The images produced by these two beams are encoded to different depths
in single B-scan. Then the Doppler signals picked up by the two beams together with the incident angle difference can be
used to calculate the absolute velocity. We validated our approach in vitro on an artificial flow phantom with our
home-built 1060 nm swept source OCT. Experimental results demonstrated that our method can provide an accurate
measurement of absolute flow velocity with independency on the projection angle.
Optical coherence tomography (OCT), as a low-coherence interferometric imaging technique, inevitably suffers from
speckle noise, which can reduce image quality and signal-to-noise (SNR). In this paper, we present a dual-beam angular
compounding method to reduce speckle noise and improve SNR of OCT image. Two separated parallel light beams are
created on the sample arm using a 1x2 optical fiber coupler and are focused into samples at different angles. The
epi-detection scheme creates three different light path combinations of these two light beams above. The three
combinations produce three images in single B-scan, which are completely separated in depth. The three images show
uncorrelated speckle patterns and therefore can be averaged to create a new image with reduced speckle noise. Compared
to those reported angular and spatial compounding methods, our method retains their advantages, and moreover has a
faster imaging speed and keep the transverse resolution. This method was evaluated on human fingertips <i>in vivo</i>. The
results demonstrated a good improvement in speckle contrast.
Optical coherence tomography (OCT) is one of the successful inventions in medical imaging as a clinic routine in the past decades. This imaging technique is based on low coherence interferometer and consequently suffers from speckle noise inherently, which can degrade image quality and obscure micro-structures. Therefore, effective speckle reduction techniques have been always desired and researched since optical coherence tomography was invented. In this study, we proposed an angular compounding method to reduce speckle noise of OCT image. Two different angular light paths are created on the sample arm using two beam splitters. The epi-detection scheme creates three different combinations of the two angular light paths above, which produce three images in single B-scan. To compound these three images, these three images are separated in depth by delaying one light path relative to the other. Compared to those reported angular compounding methods, our method showed an advantage of faster imaging speed. This method was evaluated on an artificial eye model. The results demonstrated a 1.46-fold improvement in speckle contrast.