1. Articles from opticsinfobase.org

  2. 1-24 of 1133 1 2 3 4 ... 46 47 48 »
    1. Depth extension and sidelobe suppression in optical coherence tomography using pupil filters

      Depth extension and sidelobe suppression in optical coherence tomography using pupil filters

      We demonstrate a new focus engineering scheme to achieve both extended depth of focus (DOF) and sidelobe suppression in spectral-domain optical coherence tomography (SD-OCT) system. Each of the illumination pupil function and the detection pupil function is modulated using an annular pupil filter implemented by center obscuration. The two pupil filters are arranged in a dark-field configuration such that the first sidelobe of the illumination point-spread function (PSF) matches the first minimum of the detection PSF in the lateral focal plane. We tested the feasibility of the proposed scheme numerically, and then constructed a dark-field OCT (DF-OCT) system to further ...

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    2. Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

      Phase-sensitive optical coherence tomography using an Vernier-tuned distributed Bragg reflector swept laser in the mouse middle ear

      Phase-sensitive optical coherence tomography (PhOCT) offers exquisite sensitivity to mechanical vibration in biological tissues. There is growing interest in using PhOCT for imaging the nanometer scale vibrations of the ear in animal models of hearing disorders. Swept-source-based systems offer fast acquisition speeds, suppression of common mode noise via balanced detection, and good signal roll-off. However, achieving high phase stability is difficult due to nonlinear laser sweeps and trigger jitter in a typical swept laser source. Here, we report on the initial application of a Vernier-tuned distributed Bragg reflector (VT-DBR) swept laser as the source for a fiber-based PhOCT system. The ...

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    3. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging

      All-fiber wavelength swept ring laser based on  Fabry-Perot filter for optical frequency domain  imaging

      Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral ...

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    4. Noise characterization of broadband fiber Cherenkov radiation as a visible-wavelength source for optical coherence tomography and two-photon fluorescence microscopy

      Noise characterization of broadband fiber Cherenkov radiation as a visible-wavelength source for optical coherence tomography and two-photon fluorescence microscopy

      Optical sources in the visible region immediately adjacent to the near-infrared biological optical window are preferred in imaging techniques such as spectroscopic optical coherence tomography of endogenous absorptive molecules and two-photon fluorescence microscopy of intrinsic fluorophores. However, existing sources based on fiber supercontinuum generation are known to have high relative intensity noise and low spectral coherence, which may degrade imaging performance. Here we compare the optical noise and pulse compressibility of three high-power fiber Cherenkov radiation sources developed recently, and evaluate their potential to replace the existing supercontinuum sources in these imaging techniques.

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    5. Supercontinuum optimization for dual-soliton based light sources using genetic algorithms in a grid platform

      Supercontinuum optimization for dual-soliton based light sources using genetic algorithms in a grid platform

      We present a numerical strategy to design fiber based dual pulse light sources exhibiting two predefined spectral peaks in the anomalous group velocity dispersion regime. The frequency conversion is based on the soliton fission and soliton self-frequency shift occurring during supercontinuum generation. The optimization process is carried out by a genetic algorithm that provides the optimum input pulse parameters: wavelength, temporal width and peak power. This algorithm is implemented in a Grid platform in order to take advantage of distributed computing. These results are useful for optical coherence tomography applications where bell-shaped pulses located in the second near-infrared window are ...

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    6. Feasibility of ablative fractional laser-assisted drug delivery with optical coherence tomography

      Feasibility of ablative fractional laser-assisted drug delivery with optical coherence tomography

      Fractional resurfacing creates hundreds of microscopic wounds in the skin without injuring surrounding tissue. This technique allows rapid wound healing owing to small injury regions, and has been proven as an effective method for repairing photodamaged skin. Recently, ablative fractional laser (AFL) treatment has been demonstrated to facilitate topical drug delivery into skin. However, induced fractional photothermolysis depends on several parameters, such as incident angle, exposure energy, and spot size of the fractional laser. In this study, we used fractional CO 2 laser to induce microscopic ablation array on the nail for facilitating drug delivery through the nail. To ensure ...

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    7. Volumetric (3D) compressive sensing spectral domain optical coherence tomography

      Volumetric (3D) compressive sensing spectral domain optical coherence tomography

      In this work, we proposed a novel three-dimensional compressive sensing (CS) approach for spectral domain optical coherence tomography (SD OCT) volumetric image acquisition and reconstruction. Instead of taking a spectral volume whose size is the same as that of the volumetric image, our method uses a sub set of the original spectral volume that is under-sampled in all three dimensions, which reduces the amount of spectral measurements to less than 20% of that required by the Shan-non/Nyquist theory. The 3D image is recovered from the under-sampled spectral data dimension-by-dimension using the proposed three-step CS reconstruction strategy. Experimental results show ...

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    8. Two electric field Monte Carlo models of coherent backscattering of polarized light

      Two electric field Monte Carlo models of coherent backscattering of polarized light

      Modeling of coherent polarized light propagation in turbid scattering medium by the Monte Carlo method provides an ultimate understanding of coherent effects of multiple scattering, such as enhancement of coherent backscattering and peculiarities of laser speckle formation in dynamic light scattering (DLS) and optical coherence tomography (OCT) diagnostic modalities. In this report, we consider two major ways of modeling the coherent polarized light propagation in scattering tissue-like turbid media. The first approach is based on tracking transformations of the electric field along the ray propagation. The second one is developed in analogy to the iterative procedure of the solution of ...

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    9. Broadband fiber-optical parametric amplification for ultrafast time-stretch imaging at 1.0 um

      Broadband fiber-optical parametric amplification for ultrafast time-stretch imaging at 1.0 um

      We demonstrate a broadband all-fiber-optical parametric amplifier for ultrafast time-stretch imaging at 1.0 μm, featured by its compact design, alignment-free, high efficiency, and flexible gain spectrum through fiber nonlinearity- and dispersion-engineering: specifically on a dispersion-stabilized photonic-crystal fiber (PCF) to achieve a net gain over 20 THz (75 nm) and a highest gain of ∼ 6000 (37.5 dB). Another unique feature of the parametric amplifier, over other optical amplifiers, is the coherent generation of a synchronized signal replica (called idler) that can be exploited to offer an extra 3-dB gain by optically superposing the signal and idler. It further enhances ...

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    10. Correction of rotational distortion for catheter-based en face OCT and OCT angiography

      Correction of rotational distortion for catheter-based en face OCT and OCT angiography

      We demonstrate a computationally efficient method for correcting the nonuniform rotational distortion (NURD) in catheter-based imaging systems to improve endoscopic en face optical coherence tomography (OCT) and OCT angiography. The method performs nonrigid registration using fiducial markers on the catheter to correct rotational speed variations. Algorithm performance is investigated with an ultrahigh-speed endoscopic OCT system and micromotor catheter. Scan nonuniformity is quantitatively characterized, and artifacts from rotational speed variations are significantly reduced. Furthermore, we present endoscopic en face OCT and OCT angiography images of human gastrointestinal tract in vivo to demonstrate the image quality improvement using the correction algorithm.

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    11. Motion analysis and removal in intensity variation based OCT angiography

      Motion analysis and removal in intensity variation based OCT angiography

      In this work, we investigated how bulk motion degraded the quality of optical coherence tomography (OCT) angiography that was obtained through calculating interframe signal variation, i.e., interframe signal variation based optical coherence angiography (isvOCA). We demonstrated theoretically and experimentally that the spatial average of isvOCA signal had an explicit functional dependency on bulk motion. Our result suggested that the bulk motion could lead to an increased background in angiography image. Based on our motion analysis, we proposed to reduce image artifact induced by transient bulk motion in isvOCA through adaptive thresholding. The motion artifact reduced angiography was demonstrated in ...

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      Mentions: Xuan Liu
    12. Complex differential variance algorithm for optical coherence tomography angiography

      Complex differential variance algorithm for optical coherence tomography angiography

      We describe a complex differential variance (CDV) algorithm for optical coherence tomography based angiography. The algorithm exploits both the intensity and phase changes of optical coherence tomography (OCT) signals from flowing blood to achieve high vascular contrast, and also intrinsically reject undesirable phase signals originating from small displacement axial bulk tissue motion and instrument synchronization errors. We present this algorithm within a broader discussion of the properties of OCT signal dynamics. The performance of the algorithm is compared against two other existing algorithms using both phantom measurements and in vivo data. We show that the algorithm provides better contrast for ...

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    13. Noncontact depth-resolved micro-scale optical coherence elastography of the cornea

      Noncontact depth-resolved micro-scale optical coherence elastography of the cornea

      High-resolution elastographic assessment of the cornea can greatly assist clinical diagnosis and treatment of various ocular diseases. Here, we report on the first noncontact depth-resolved micro-scale optical coherence elastography of the cornea achieved using shear wave imaging optical coherence tomography (SWI-OCT) combined with the spectral analysis of the corneal Lamb wave propagation. This imaging method relies on a focused air-puff device to load the cornea with highly-localized low-pressure short-duration air stream and applies phase-resolved OCT detection to capture the low-amplitude deformation with nano-scale sensitivity. The SWI-OCT system is used here to image the corneal Lamb wave propagation with the frame ...

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    14. Dispersion compensation in Fourier domain optical coherence tomography

      Dispersion compensation in Fourier domain optical coherence tomography

      In this work, we propose a numerical technique to compensate for errors due to dispersion effects in Fourier domain optical coherence tomography. The proposed technique corrects for errors in depth measurements and resolution loss due to dispersion. The results show that, by using this technique, errors in thickness measurement are reduced from about 5% to less than 0.1% depending on the sample length and the amount of dispersion. Also, an improvement in the resolution from about 50 μm to less than 10 μm is demonstrated.

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    15. Quantitative technique for robust and noise-tolerant speed measurements based on speckle decorrelation in optical coherence tomography

      Quantitative technique for robust and noise-tolerant speed measurements based on speckle decorrelation in optical coherence tomography

      Intensity-based techniques in optical coherence tomography (OCT), such as those based on speckle decorrelation, have attracted great interest for biomedical and industrial applications requiring speed or flow information. In this work we present a rigorous analysis of the effects of noise on speckle decorrelation, demonstrate that these effects frustrate accurate speed quantitation, and propose new techniques that achieve quantitative and repeatable measurements. First, we derive the effect of background noise on the speckle autocorrelation function, finding two detrimental effects of noise. We propose a new autocorrelation function that is immune to the main effect of background noise and permits quantitative ...

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    16. Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography

      Hybrid single-source online Fourier transform coherent anti-Stokes Raman scattering/optical coherence tomography

      We demonstrate a multimodal optical coherence tomography (OCT) and online Fourier transform coherent anti-Stokes Raman scattering (FTCARS) platform using a single sub-12 femtosecond (fs) Ti:sapphire laser enabling simultaneous extraction of structural and chemical (“morphomolecular”) information of biological samples. Spectral domain OCT prescreens the specimen providing a fast ultrahigh ( 4 × 12     μ m axial and transverse) resolution wide field morphologic overview. Additional complementary intrinsic molecular information is obtained by zooming into regions of interest for fast label-free chemical mapping with online FTCARS spectroscopy. Background-free CARS is based on a Michelson interferometer in combination with a highly linear piezo stage, which allows ...

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    17. Automated identification of basal cell carcinoma by polarization-sensitive optical coherence tomography

      Automated identification of basal cell carcinoma by polarization-sensitive optical coherence tomography

      We report an automated classifier to detect the presence of basal cell carcinoma in images of mouse skin tissue samples acquired by polarization-sensitive optical coherence tomography (PS-OCT). The sensitivity and specificity of the classifier based on combined information of the scattering intensity and birefringence properties of the samples are significantly higher than when intensity or birefringence information are used alone. The combined information offers a sensitivity of 94.4% and specificity of 92.5%, compared to 78.2% and 82.2% for intensity-only information and 85.5% and 87.9% for birefringence-only information. These results demonstrate that analysis of the ...

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    18. Relation of joint spectral and time domain optical coherence tomography (jSTdOCT) and phase-resolved Doppler OCT

      Relation of joint spectral and time domain optical coherence tomography (jSTdOCT) and phase-resolved Doppler OCT

      A variety of promising approaches for quantitative flow velocity measurement in OCT have been proposed in recent years. The question is: Which method gets the most precise flow velocity out of the interference signals detected. We have compared the promising joint spectral and time domain optical coherence tomography (jSTdOCT) and the commonly used phase-resolved Doppler OCT (DOCT) and describe the link between these two proven methods for OCT in the Fourier domain (FD OCT). First, we show that jSTdOCT can be significantly improved by calculating the center of gravity via an unbiased complex algorithm instead of detecting the maximum intensity ...

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    19. In vivo analysis of burns in a mouse model using spectroscopic optical coherence tomography

      In vivo analysis of burns in a mouse model using spectroscopic optical coherence tomography

      Spectroscopic analysis of biological tissues can provide insight into changes in structure and function due to disease or injury. Depth-resolved spectroscopic measurements can be implemented for tissue imaging using optical coherence tomography (OCT). Here, spectroscopic OCT is applied to in vivo measurement of burn injury in a mouse model. Data processing and analysis methods are compared for their accuracy. Overall accuracy in classifying burned tissue was found to be as high as 91%, producing an area under the curve of a receiver operating characteristic curve of 0.97. The origins of the spectral changes are identified by correlation with histopathology.

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    20. Detection of plasmonic nanoparticles with full field-OCT: optical and photothermal detection

      Detection of plasmonic nanoparticles with full field-OCT: optical and photothermal detection

      Detecting the signal backscattered by nanoparticles immersed in highly scattering media such as biological tissue remains a challenge. In this article we report on the use of Full Field OCT (FF-OCT) to slice in depth in phantoms and in tissues in order a) to selectively observe the particles through the backscattered light at suitable wavelengths, and b) to detect the effects of the time-dependent response to full field optical heating through the strong absorption cross-section of these plasmonic nanoparticles. The analysis of the thermal wave behavior leads to the localization of the heat sources even when FF-OCT signals cannot reach ...

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    21. Quantitative measurements of strain and birefringence with common-path polarization-sensitive optical coherence tomography

      Quantitative measurements of strain and birefringence with common-path polarization-sensitive optical coherence tomography

      We demonstrate the first system for optical coherence tomography (OCT) that enables simultaneous measurement of quantitative birefringence and strain in biological samples using a common-path configuration. Owing to its superior phase stability, common-path polarization sensitive optical coherence tomography (CoPPSe-OCT) achieves a sub-nanometer displacement sensitivity of 0.52 nm at an SNR of 48 dB. We utilize CoPPSe-OCT to measure reflectance, birefringence, and strain for distinguishing burnt regions in a birefringent biological sample (chicken breast muscle).

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    22. Optical microcavity scanning 3D tomography

      Optical microcavity scanning 3D tomography

      A scanning optical microcavity is exploited to achieve lens-free 3D tomography of microfluidic channels. The microcavity, powered by a low-coherence source, is realized by approaching a cleaved fiber to few tens of micrometers over the sample. The interference of scattered waves inside the cavity shapes the transverse field distribution by focusing the beam and overcoming the diffraction limit due to the optical-fiber numerical aperture. The focusing effect is also preserved in the inner layers of the sample, allowing optical 3D tomography. Analysis of microfluidic channels was demonstrated through this noninvasive technique. Although the experimental setup recalls the well-known fiber-optic Fourier-domain ...

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    23. In vivo functional microangiography by visible-light optical coherence tomography

      In vivo functional microangiography by visible-light optical coherence tomography

      Although hemoglobin oxygen saturation (sO 2 ) in the microvasculature is an essential physiological parameter of local tissue functions, non-invasive measurement of microvascular sO 2 is still challenging. Here, we demonstrated that visible-light optical coherence tomography (vis-OCT) can simultaneously provide three-dimensional anatomical tissue morphology, visualize microvasculature at the capillary level, and measure sO 2 from the microvasculature in vivo . We utilized speckle contrast caused by the moving blood cells to enhance microvascular imaging. We applied a series of short-time inverse Fourier transforms to obtain the spectroscopic profile of blood optical attenuation, from which we quantified sO 2 . We validated the sO ...

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    24. Fully automated detection of diabetic macular edema and dry age-related macular degeneration from optical coherence tomography images

      Fully automated detection of diabetic macular edema and dry age-related macular degeneration from optical coherence tomography images

      We present a novel fully automated algorithm for the detection of retinal diseases via optical coherence tomography (OCT) imaging. Our algorithm utilizes multiscale histograms of oriented gradient descriptors as feature vectors of a support vector machine based classifier. The spectral domain OCT data sets used for cross-validation consisted of volumetric scans acquired from 45 subjects: 15 normal subjects, 15 patients with dry age-related macular degeneration (AMD), and 15 patients with diabetic macular edema (DME). Our classifier correctly identified 100% of cases with AMD, 100% cases with DME, and 86.67% cases of normal subjects. This algorithm is a potentially impactful ...

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    1-24 of 1133 1 2 3 4 ... 46 47 48 »
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