1. 1-24 of 139 1 2 3 4 5 6 »
    1. A 45° saw-dicing process applied to a glass substrate for wafer-level optical splitter fabrication for optical coherence tomography

      A 45° saw-dicing process applied to a glass substrate for wafer-level optical splitter fabrication for optical coherence tomography

      This paper reports on the development of a technology for the wafer-level fabrication of an optical Michelson interferometer, which is an essential component in a micro opto-electromechanical system (MOEMS) for a miniaturized optical coherence tomography (OCT) system. The MOEMS consists on a titanium dioxide/silicon dioxide dielectric beam splitter and chromium/gold micro-mirrors. These optical components are deposited on 45° tilted surfaces to allow the horizontal/vertical separation of the incident beam in the final micro-integrated system. The fabrication process consists of 45° saw dicing of a glass substrate and the subsequent deposition of dielectric multilayers and metal layers. The ...

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    2. High-resolution and nondestructive profile measurement by spectral-domain optical coherence tomography with a visible broadband light source for optical-device fabrication

      High-resolution and nondestructive profile measurement by spectral-domain optical coherence tomography with a visible broadband light source for optical-device fabrication

      We developed a spectral-domain optical coherence tomography (OCT) using a visible broadband light source (vis-OCT) for application to high-resolution and nondestructive profile measurement and imaging in semiconductor optical-device fabrication. By using visible broadband light centered at 625 nm and with spectral bandwidth of 260 nm, an axial resolution of 0.69 µm in air was obtained. This was effective for inspection of a transparent photoresist film with thickness of 1–2 µm coated on a semiconductor wafer; the interface between the photoresist film and its substrate and the interface between the photoresist and air were resolved, and the film thickness ...

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    3. Optical module to extend any Fourier-domain optical coherence tomography system into a polarisation-sensitive system

      Optical module to extend any Fourier-domain optical coherence tomography system into a polarisation-sensitive system

      This article presents a theoretical study on an optical module (OM) that can be inserted between an object under investigation and a Fourier-domain optical coherence tomography system, transforming the latter into a polarisation-sensitive optical coherence tomography optical coherence tomography (OCT) system. The module consists of two electro-optic modulators, a Faraday rotator, a linear polariser and a quarter-wave plate. A detailed description on how the module can be used to extract both the net retardance and the fast axis orientation of a linear birefringent sample is presented. This is achieved by taking two sequential measurements for different values of retardance produced ...

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    4. Microrheology of complex fluids

      Microrheology of complex fluids

      The field of microrheology is concerned with how materials store and dissipate mechanical energy as a function of length scale. Recent developments in the theory and instrumentation of the microrheology of complex fluids are reviewed. Equal emphasis is given to the physical phenomena probed, advances in instrumentation, and specific experimental systems in which this field has already had an impact. The inversion of the compliance data, measurement of sample heterogeneity, high frequency viscoelasticity, effects of shear flow, single molecule experiments, surface viscoelasticity and time evolution studies are considered. The techniques highlighted include particle tracking microrheology, diffusing wave spectroscopy, laser tracking ...

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    5. The diagnosis of nasopharyngeal carcinoma by optical coherence tomography (OCT)

      The diagnosis of nasopharyngeal carcinoma by optical coherence tomography (OCT)

      We have attempted to explore the intrinsic differences in the optical properties of the nasopharyngeal carcinoma (NPC) and normal tissue by optical coherence tomography (OCT). OCT imaging of normal tissue provided three layers of epithelium, lamina propria, and the brighter interface of basement membrane; while carcinomas disrupted the layered construction embedded in signal-poor images. The morphologies were consistent with histological findings. Sensitivity and specificity were 90% and 100%, respectively. This pilot study demonstrates that NPC could be diagnosed by visualization, which implies that OCT might be potentially used to differentiate normal from NPC tissue in the early stage as an ...

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    6. Optical coherence photoacoustic microscopy (OC-PAM) with an intensity-modulated continuous-wave broadband light source

      Optical coherence photoacoustic microscopy (OC-PAM) with an intensity-modulated continuous-wave broadband light source

      We developed an optical coherence photoacoustic microscopy system using an intensity-modulated continuous-wave superluminescent diode with a center wavelength of 840 nm. The system can accomplish optical coherence tomography (OCT) and photoacoustic microscopy (PAM) simultaneously. Compared to the system with a pulsed light source, this system is able to achieve OCT imaging with quality as high as conventional spectral-domain OCT. Since both of the OCT and PAM images are generated from the same group of photons, they are intrinsically registered in the lateral directions. The system was tested for multimodal imaging the vasculature of mouse ear in vivo by using gold ...

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    7. Three-dimensional image reconstruction of macula from stratus optical coherence tomography (OCT) fordiagnosis of macular degeneration

      Three-dimensional image reconstruction of macula from stratus optical coherence tomography (OCT) fordiagnosis of macular degeneration

      Diagnosis of macular degeneration using a Stratus OCT with a fast macular thickness map (FMTM) method produced six B-scan images of macula from different angles. The images were converted into a retinal thickness chart to be evaluated by normal distribution percentile of data so that it can be classified as normal thickness of macula or as experiencing abnormality (e.g. thickening and thinning). Unfortunately, the diagnostic images only represent the retinal thickness in several areas of the macular region. Thus, this study is aims to obtain the entire retinal thickness in the macula area from Status OCT's output images ...

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    8. Optical coherence tomography: an experimental validation for vascular imaging of saphenous vein bypass grafts

      Optical coherence tomography: an experimental validation for vascular imaging of saphenous vein bypass grafts

      Purpose. Optical coherence tomography (OCT) is a novel light-based intravascular imaging method with potential utility for quantifying vascular disease and the effect of therapy. OCT has been used to image vein grafts and neointima in clinical research studies but validity of OCT for vein graft imaging is limited by depth of field and tissue penetration. Experiments were carried out to validate the in-house developed new software (Medipass-iScan) and OCT vendor software comparing with a gold standard, photomicroscopy. Methods. Seven synthetic phantom tubes with varying inner diameters and eight saphenous veins were imaged with OCT. Imaging was performed five times on ...

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    9. Correction of aberrations in digital holography using the phase gradient autofocus technique

      Correction of aberrations in digital holography using the phase gradient autofocus technique

      We propose a method for correcting aberrations in digital holography based on the principles of computational adaptive optics using the phase gradient autofocus technique that demands no reference measurements. The method requires a priori information on the relative positions of the elements of the optical setup. It is applicable for sufficiently smooth optical aberrations. This technique does not impose any restrictions on the magnitude of the scattered optical field phase distortions caused by the object structure. The efficacy of the proposed method is demonstrated through numerical simulation and experimental verification.

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    10. Volumetric monitoring of aqueous two phase system droplets using time-lapse optical coherence tomography

      Volumetric monitoring of aqueous two phase system droplets using time-lapse optical coherence tomography

      We present a volumetric monitoring method to observe the morphological changes of aqueous two phase system (ATPS) droplets in a microfluidic system. Our method is based on time-lapse optical coherence tomography (OCT) which allows the study of the dynamics of ATPS droplets while visualizing their 3D structures and providing quantitative information on the droplets. In this study, we monitored the process of rehydration and deformation of an ATPS droplet in a microfluidic system and quantified the changes of its volume and velocity under both static and dynamic fluid conditions. Our results indicate that time-lapse OCT is a very promising tool ...

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    11. Imaging colon cancer development in mice: IL-6 deficiency prevents adenoma in azoxymethane-treated Smad3 knockouts

      Imaging colon cancer development in mice: IL-6 deficiency prevents adenoma in azoxymethane-treated Smad3 knockouts

      The development of colorectal cancer in the azoxymethane-induced mouse model can be observed by using a miniaturized optical coherence tomography (OCT) imaging system. This system is uniquely capable of tracking disease development over time, allowing for the monitoring of morphological changes in the distal colon due to tumor development and the presence of lymphoid aggregates. By using genetically engineered mouse models deficient in Interleukin 6 (IL-6) and Smad family member 3 (Smad3), the role of inflammation on tumor development and the immune system can be elucidated. Smad3 knockout mice develop inflammatory response, wasting, and colitis associated cancer while deficiency of ...

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    12. High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band

      High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band

      We describe the generation of a high-power, spectrally smooth supercontinuum (SC) in the 1600 nm spectral band for ultrahigh-resolution optical coherence tomography (UHR-OCT). A clean SC was achieved by using a highly nonlinear fiber with normal dispersion properties and a high-quality pedestal-free pulse obtained from a passively mode-locked erbium-doped fiber laser operating at 182 MHz. The center wavelength and spectral width were 1578 and 172 nm, respectively. The output power of the SC was 51 mW. Using the developed SC source, we demonstrated UHR-OCT imaging of biological samples with a sensitivity of 109 dB and an axial resolution of 4 ...

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    13. Monte Carlo simulation of optical coherence tomography signal of the skin nevus

      Monte Carlo simulation of optical coherence tomography signal of the skin nevus

      Monte Carlo (MC) numerical simulation of light propagation in living tissue is widely used for characterization of optical coherence tomography (OCT) signals. Using MC simulation we obtained OCT images of skin with dysplastic nevus. Two various positions of skin nevus in depth were considered. Comparing these OCT simulation results with image of skin without nevus, we showed that OCT medical approach allows to detect dysplastic nevus at different stages of its life.

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    14. Improved motion contrast and processing efficiency in OCT angiography using complex-correlation algorithm

      Improved motion contrast and processing efficiency in OCT angiography using complex-correlation algorithm

      The complex-based OCT angiography (Angio-OCT) offers high motion contrast by combining both the intensity and phase information. However, due to involuntary bulk tissue motions, complex-valued OCT raw data are processed sequentially with different algorithms for correcting bulk image shifts (BISs), compensating global phase fluctuations (GPFs) and extracting flow signals. Such a complicated procedure results in massive computational load. To mitigate such a problem, in this work, we present an inter-frame complex-correlation (CC) algorithm. The CC algorithm is suitable for parallel processing of both flow signal extraction and BIS correction, and it does not need GPF compensation. This method provides high ...

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    15. Ultrahigh-resolution optical coherence tomography at 1.3 μm central wavelength by using a supercontinuum source pumped by noise-like pulses

      Ultrahigh-resolution optical coherence tomography at 1.3 μm central wavelength by using a supercontinuum source pumped by noise-like pulses

      We report on the ultrahigh-resolution optical coherence tomography (OCT) with a novel high-power supercontinuum (SC) light source generated by noise-like pulses from an Yb-doped fiber laser. The SC spectrum is flat with a bandwidth of 420 nm centered around ~1.3 μ m. The light source is successfully employed in a time-domain OCT (TD-OCT), achieving an axial resolution of 2.3 μ m. High resolution fiber-based spectral-domain OCT (SD-OCT) imaging of bio-tissue was also demonstrated.

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    16. One step geometrical calibration method for optical coherence tomography

      One step geometrical calibration method for optical coherence tomography

      We present a novel one-step calibration methodology for geometrical distortion correction for optical coherence tomography (OCT). A calibration standard especially designed for OCT is introduced, which consists of an array of inverse pyramidal structures. The use of multiple landmarks situated on four different height levels on the pyramids allow performing a 3D geometrical calibration. The calibration procedure itself is based on a parametric model of the OCT beam propagation. It is validated by experimental results and enables the reduction of systematic errors by more than one order of magnitude. In future, our results can improve OCT image reconstruction and interpretation ...

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    17. Real Time Signal Processing and Data Handling with dedicated hardware in handheld OCT Device

      Real Time Signal Processing and Data Handling with dedicated hardware in handheld OCT Device

      The manuscript presents the topics on real time signal processing with dedicated hardware presented at the INFIERI Summer School 2014. The focus of this work is on real-time signal processing, filtering and massive parallel computing. In general, medical devices have stringed demands on energy consumption as well as on data processing and handling. In fact, the development of novel medical devices has led to significant advances in fields such as instrumentation, algorithm development and image processing. In this manuscript, two aspects of the design are brought into consideration: the transformation of a conventional signal processing algorithm into an equivalent version ...

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    18. New variational image decomposition model for simultaneously denoising and segmenting optical coherence tomography images

      New variational image decomposition model for simultaneously denoising and segmenting optical coherence tomography images

      Optical coherence tomography (OCT) imaging plays an important role in clinical diagnosis and monitoring of diseases of the human retina. Automated analysis of optical coherence tomography images is a challenging task as the images are inherently noisy. In this paper, a novel variational image decomposition model is proposed to decompose an OCT image into three components: the first component is the original image but with the noise completely removed; the second contains the set of edges representing the retinal layer boundaries present in the image; and the third is an image of noise, or in image decomposition terms, the texture ...

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    19. Autocorrelation optical coherence tomography for glucose quantification in blood

      Autocorrelation optical coherence tomography for glucose quantification in blood

      We report a new method for glucose monitoring in blood tissue based on the autocorrelation function (ACF) analysis in Fourier domain optical coherence tomography (FD-OCT). We have determined the changes in OCT monitoring signals' depth to characterize the modulations in ACFs for quantitative measurements of glucose concentrations in blood. We found that an increase in the concentration of glucose in blood results in decreased OCT monitoring signal due to the increase in the refractive index of the media.

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    20. Simple and versatile long range swept source for optical coherence tomography applications

      Simple and versatile long range swept source for optical coherence tomography applications

      We present a versatile long coherence length swept-source laser design for optical coherence tomography applications. This design consists of a polygonal spinning mirror and an optical gain chip in a modified Littman–Metcalf cavity. A narrowband intra-cavity filter is implemented through multiple passes off a diffraction grating set at grazing incidence. The key advantage of this design is that it can be readily adapted to any wavelength regions for which broadband gain chips are available. We demonstrate this by implementing sources at 1650 nm, 1550 nm, 1310 nm and 1050 nm. In particular, we present a 1310 nm swept source ...

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    21. 3D Human cartilage surface characterization by optical coherence tomography

      3D Human cartilage surface characterization by optical coherence tomography

      Early diagnosis and treatment of cartilage degeneration is of high clinical interest. Loss of surface integrity is considered one of the earliest and most reliable signs of degeneration, but cannot currently be evaluated objectively. Optical Coherence Tomography (OCT) is an arthroscopically available light-based non-destructive real-time imaging technology that allows imaging at micrometre resolutions to millimetre depths. As OCT-based surface evaluation standards remain to be defined, the present study investigated the diagnostic potential of 3D surface profile parameters in the comprehensive evaluation of cartilage degeneration. To this end, 45 cartilage samples of different degenerative grades were obtained from total knee replacements ...

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    22. Optical absorption spectra of human articular cartilage correlate with biomechanical properties, histological score and biochemical composition

      Optical absorption spectra of human articular cartilage correlate with biomechanical properties, histological score and biochemical composition

      This study investigates the relationship between the optical response of human articular cartilage in the visible (VIS) and near infrared (NIR) spectral range and its matrix properties. Full-thickness osteochondral cores (dia. = 16?mm, n = 50) were extracted from human cadaver knees ( N = 13) at four anatomical locations and divided into quadrants. Absorption spectra were acquired in the spectral range 400?1100?nm from one quadrant. Reference biomechanical, biochemical composition, histological, and cartilage thickness measurements were obtained from two other quadrants. A multivariate statistical technique based on partial least squares (PLS) regression was then employed to investigate the correlation between the ...

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    23. High-speed ultrahigh-resolution spectral domain optical coherence tomography using high-powersupercontinuum at 0.8 µm wavelength

      High-speed ultrahigh-resolution spectral domain optical coherence tomography using high-powersupercontinuum at 0.8 µm wavelength

      We demonstrated high-speed ultrahigh-resolution (UHR) optical coherence tomography (OCT) in the 800 nm wavelength region. A high-power coherent supercontinuum (SC) and a high-speed line scan camera were used to construct a spectral domain OCT. The axial resolution was 3.1 µm in air and 2.3 µm in tissue. The dependence of sensitivity on the SC power and A-scan rate was examined. For the A-scan rate of 70 kHz, the sensitivity of 104 dB was achieved for the SC power higher than 60 mW. High-speed in vivo UHR-OCT imaging was demonstrated for zebrafish embryo and swimming medaka.

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    24. Chromatic dispersion effects in ultra-low coherence interferometry

      Chromatic dispersion effects in ultra-low coherence interferometry

      We consider the properties of an interference signal shift from zero-path-difference position in the presence of an uncompensated dispersive layer in one of the interferometer arms. It is experimentally shown that in using an ultra-low coherence light source, the formation of the interference signal is also determined by the group velocity dispersion, which results in a nonlinear dependence of the position of the interference signal on the geometrical thickness of the dispersive layer. The discrepancy in the dispersive layer and compensator refractive indices in the third decimal place is experimentally shown to lead to an interference signal shift that is ...

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    1-24 of 139 1 2 3 4 5 6 »
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