Abstract
Joint-aperture optical coherence tomography (JA-OCT) is an angle-resolved OCT method, in which illumination from an active channel is simultaneously probed by several passive channels. JA-OCT increases the collection efficiency and effective sensitivity of the OCT system without increasing the power on the sample. Additionally, JA-OCT provides angular scattering information about the sample in a single acquisition, so the OCT imaging speed is not reduced. Thus, JA-OCT is especially suitable for ultra high speed in-vivo imaging. JA-OCT is compared to other angle-resolved techniques, and the relation between joint aperture imaging, adaptive optics, coherent and incoherent compounding is discussed. We present angle-resolved imaging of the human retina at an axial scan rate of 1.68 MHz, and demonstrate the benefits of JA-OCT: Speckle reduction, signal increase and suppression of specular and parasitic reflections. Moreover, in the future JA-OCT may allow for the reconstruction of the full Doppler vector and tissue discrimination by analysis of the angular scattering dependence.
Highlights
Optical coherence tomography (OCT) is an interferometric imaging technique [1], which allows for cross-sectional imaging of a large variety of samples
We describe Joint-aperture optical coherence tomography (JA-OCT) and discuss how it relates to other speckle reduction techniques as well as to OCT systems with large numerical aperture (NA), e.g. adaptive optics OCT (AO-OCT)
JA-OCT offers numerous benefits, which are especially relevant for ultrahigh-speed systems: The increased collection efficiency of JA-OCT can partially compensate for lower exposure time per line
Summary
Optical coherence tomography (OCT) is an interferometric imaging technique [1], which allows for cross-sectional imaging of a large variety of samples. Image quality and speed are closely interlinked by both sensitivity and averaging based speckle noise reduction, while resolution and roll-off are in principle speed-independent in FD-OCT. Many functional OCT techniques profit from very high imaging speeds, since the resulting short acquisition times “freeze” the contrast-degrading motion of the sample. Functional imaging techniques do usually slow down the acquisition process, since many times multiple scans have to be acquired at the same position to evaluate the changing speckle or phase pattern. Averaging of multiple scans can improve image quality considerably, for example in polarization sensitive OCT [38] This is equivalent to standard OCT frame averaging, and again, high speed systems facilitate averaging but do decrease sensitivity due to their smaller exposure time per axial scan. JA-OCT offers new possibilities for functional imaging such as angle-resolved Doppler OCT
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