1,721,017 research outputs found
Demonstration of Triband Multi-Focal Imaging with Optical Coherence Tomography
No full textWe demonstrate an extended depth of focus optical coherence tomography (OCT) system based on the use of chromatic aberration to create displaced focal planes in the sample. The system uses a wavelength-swept source tuning over three spectral bands and three separate interferometers, each of which interfaces to a single illumination/collection fiber. The resulting three imaged volumes are merged in post-processing to generate an image with a larger depth of focus than is obtained from each band individually. The improvements are demonstrated in structural imaging of a porous phantom and a lipid-cleared murine brain, and by angiographic imaging of human skin. By using a coaxial approach with Gaussian beams, this approach enables an extended focus with relatively simple microscope optics and data-merging algorithms. Keywords: optical coherence tomography; multi-focal imaging; chromatic focal shiftNational Institutes of Health (U.S.) (Grant R01CA163528)United States. Department of Energy (Grant FA9550-11-1-0331
Retinal Blood Vessel Caliber Estimation for Optical Coherence Tomography Angiography Images Based on 3D Superellipsoid Modeling
No full textChanges of retinal blood vessel calibers may reflect various retinal diseases and even several nonretinal diseases. We propose a new method to estimate retinal vessel calibers from 3D optical coherence tomography angiography (OCTA) images based on 3D modeling using superellipsoids. Taking advantage of 3D visualization of the retinal tissue microstructures in vivo provided by OCTA, our method can detect retinal blood vessels precisely, estimate their calibers reliably, and show the relative flow speed visually.
Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging
No full textFourier-domain mode locking has been a popular laser design for high-speed optical-frequency-domain imaging (OFDI), but achieving long coherence lengths, and therefore imaging range, has been challenging. The narrow linewidth of a Fourier-domain mode-locked (FDML) frequency-comb (FC) laser could provide an attractive platform for high-speed as well as long-range OFDI. Unfortunately, aliasing artifacts arising from signals beyond the principal measurement depth of the free spectral range have prohibited the use of an FDML FC laser for imaging so far. To make the increased coherence length of an FDML FC laser available, methods to manage such artifacts are required. Recently, coherent circular ranging that uses frequency combs for imaging in much-reduced rf bandwidths has been demonstrated. Here we revisit circular ranging as a tool for making the long coherence length of an FDML FC laser and its use for tissue imaging accessible. Using an acousto-optic frequency shifter (AOFS), we describe an active method to mitigate signal aliasing that is both stable and wavelength independent. We show that an FDML FC laser increases the coherence length by an order of magnitude compared with traditional FDML-laser designs without requiring precise dispersion engineering. We discuss design parameters of a frequency-stepping laser resonator as well as aliasing from a frequency comb and AOFS in OFDI with numerical simulations. The use of circular ranging additionally reduces acquisition bandwidths 15-fold compared with traditional OFDI methods. The FDML FC–AOFS design offers a convenient platform for long-range and high-speed imaging as well as for exploring signal- and image-processing methods in circular ranging.National Institutes of Health (U.S.) (Grant P41EB-015903
Feature issue introduction: ultrafast optical imaging
Get PDFThis feature issue of Optics Express collects 20 articles that report the most recent progress of ultrafast optical imaging. This review provides a summary of these articles that cover the spectrum of ultrafast optical imaging, from new technologies to applications
Sub-diffusion flow velocimetry with number fluctuation optical coherence tomography
No full textWe show number fluctuations dynamic light scattering optical coherence tomography (OCT) for measuring extremely slow, sub-diffusion flows of dilute particle suspensions. Our method removes the minimum measurable velocity limitation of conventional correlation-based or phase-resolved Doppler OCT, set by flowing particles’ Brownian motion. Our technique works for any Doppler angle, is applicable to 2D flow imaging with scanning OCT systems and can be used to determine concentration of particles under flow.ImPhys/Kalkman groupImPhys/Computational Imagin
Robust and easy-to-operate stretched-pulse mode-locked wavelength-swept laser with an all-polarization-maintaining fiber cavity for 10 MHz A-line rate optical coherence tomography
No full textWe demonstrate robust and easy-to-operate stretched-pulse mode-locked laser (SPML) architectures using all-polarization-maintaining fiber laser cavities. Because of the polarization-maintaining construction, the laser performance is unaffected by mechanical perturbation on the cavity fibers. The lasers automatically initiate linear-in-wavenumber sweeps across 100 nm centered at 1290 nm with a 10 MHz repetition rate. OCT imaging with a sensitivity of 98 dB and a single-sided 6 dB coherence length of 2.5 mm is demonstrated. OCT angiography of a mouse brain that visualized three-dimensional cerebral microvasculature over a field of 1.5 mm × 1.5 mm (398 A-lines × 380 B-scans) at a rate of 5.26 volumes per second is also presented. The robust all-PMF SPML lasers are a turnkey, high-performance source for ultrahigh-speed OCT imaging
Computational 3D resolution enhancement for optical coherence tomography with a narrowband visible light source
No full textPhase-preserving spectral estimation optical coherence tomography (SE-OCT) enables combining axial resolution improvement with computational depth of focus (DOF) extension. We combine SE-OCT with interferometric synthetic aperture microscopy (ISAM) to obtain a high 3D resolution over a large depth range with a narrow bandwidth visible light super-luminescent diode (SLD). SE-OCT gives a five times axial resolution improvement to 1.5 micrometer. The combination with ISAM gives a sub-micron lateral resolution over a 300 micrometer axial range, 12 times the conventional DOF. The results show that phase-preserving SE-OCT is sufficiently accurate for coherent post-processing, enabling the use of cost-effective SLDs in the visible light range for high spatial resolution OCT.ImPhys/Computational ImagingImPhys/Kalkman grou
Wide-field computational cellular-resolution imaging of the human retina using multi-MHz phase-stable SS-OCT
No full textThree-dimensional (3D) cellular-resolution imaging of the living human retina over a large field of view would bring a great impact in clinical ophthalmology, potentially finding new biomarkers for early diagnosis and improving the pathophysiological understanding of ocular diseases. While hardware-based and computational adaptive optics (AO) optical coherence tomography (OCT) have been developed to achieve cellular-resolution retinal imaging, these approaches support limited 3D imaging fields and their high cost and their intrinsic hardware complexity limit their practical utility. Here, we demonstrate 3D depth-invariant cellular-resolution imaging of the living human retina over a 3-mm × 3-mm field of view using the intrinsically phase-stable multi-MHz retinal swept-source OCT and tailored computational defocus and aberration correction methods. Single-acquisition imaging of photoreceptor cells, retinal nerve fiber layer, and retinal capillaries is presented across unprecedented imaging fields. By providing wide-field 3D cellular-resolution imaging in the human retina using a standard point-scan architecture routinely used in the clinic, this platform proposes a strategy for expanded utilization of high-resolution retinal imaging in both research and clinical settings
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