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Erich Gotzinger, Michael Pircher, Bernhard Baumann, Tilman Schmoll, Harald Sattmann, Rainer Leitgeb, Christoph Hitzenberger; Ultra High Speed Fiber Based Polarization Sensitive Spectral Domain Optical Coherence Tomography of the Human Retina. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1708.
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© ARVO (1962-2015); The Authors (2016-present)
To measure the polarization properties of the human retina with an ultra high speed fiber based polarization sensitive OCT (PS-OCT) system.
We demonstrate an ultra high speed fiber based polarization sensitive spectral domain optical coherence tomography system, using two ultra high speed CMOS line scan cameras. With this system an A-scan rate of up to 128 kHz was achieved. The system is based on polarization maintaining fibers and retrieves the backscattered intensity, retardation, optic axis orientation and Stokes vectors with a single A-scan per measurement location. This high speed data acquisition enables averaging (without the use of an eye tracker) of several acquired B-scans of intensity and polarization data to reduce speckle noise. We discuss different averaging techniques and compare the results.
We measured the fovea and the nerve head of healthy volunteers. Up to 60 successively recorded and motion corrected B-scan data sets are averaged. Speckle reduced PS-OCT images of intensity, retardation, and optic axis orientation are demonstrated. Different averaging schemes are compared, the best ones providing a ~5 fold noise reduction in the polarization sensitive images. Furthermore, a novel scheme of calculating the degree of polarization uniformity (DOPU) is presented. Instead of spatial averaging of Stokes vector data, temporal averaging over successive images is used, which provides a considerably improved spatial resolution of DOPU images.
The high imaging speed strongly reduces motion artifacts and therefore averaging of several B-scans is possible. This averaging strongly improves image quality and also reduces speckle noise. The reduced speckle noise improves the accuracy of birefringence calculation. The new DOPU calculation algorithm strongly improves the resolution of DOPU images, which might be useful for the detection of small depolarizing structures in diseases like AMD.
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