1. 1-24 of 89 1 2 3 4 »
    1. A model for simulating speckle-pattern evolution based on close to reality procedures used inspectral-domain OCT

      A model for simulating speckle-pattern evolution based on close to reality procedures used inspectral-domain OCT

      A robust model for simulating speckle-pattern evolution in optical coherence tomography (OCT) depending on the OCT system parameters and tissue deformation is reported. The model is based on the application of close to reality procedures used in spectral-domain OCT scanners. It naturally generates images reproducing properties of real images in spectral-domain OCT, including the pixelized structure and finite depth of unambiguous imaging, influence of the optical spectrum shape, dependence on the optical wave frequency and coherence length, influence of the tissue straining, etc. Good agreement with generally accepted speckle features and properties of real OCT images is demonstrated.

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    2. Achromatic registration of quadrature components of the optical spectrum in spectral domain opticalcoherence tomography

      Achromatic registration of quadrature components of the optical spectrum in spectral domain opticalcoherence tomography

      We have thoroughly investigated the method of simultaneous reception of spectral components with the achromatised quadrature phase shift between two portions of a reference wave, designed for the effective suppression of the 'mirror' artefact in the resulting image obtained by means of spectral domain optical coherence tomography (SD OCT). We have developed and experimentally tested a phase-shifting element consisting of a beam divider, which splits the reference optical beam into the two beams, and of delay lines being individual for each beam, which create a mutual phase difference of π/2 in the double pass of the reference beam. The phase ...

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    3. Nanosensitive optical coherence tomography for the study of changes in static and dynamic structures

      Nanosensitive optical coherence tomography for the study of changes in static and dynamic structures

      We briefly discuss the principle of image formation in Fourier domain optical coherence tomography (OCT). The theory of a new approach to improve dramatically the sensitivity of conventional OCT is described. The approach is based on spectral encoding of spatial frequency. Information about the spatial structure is directly translated from the Fourier domain to the image domain as different wavelengths, without compromising the accuracy. Axial spatial period profiles of the structure are reconstructed for any volume of interest within the 3D OCT image with nanoscale sensitivity. An example of application of the nanoscale OCT to probe the internal structure of ...

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    4. A method for obtaining scattering decomposed images in optical coherence tomography

      A method for obtaining scattering decomposed images in optical coherence tomography

      A method for obtaining scattering decomposed images in optical coherence tomography based on a multiple scattering model is proposed. Images of different scattering components can be obtained with this method. Employing the proposed method, scattering decomposed images of a biological sample are obtained. Then spatial mean filtering for denoising is performed on only the multiple scattering component, and the total signal is reconstructed. This method is useful for observing the images of different scattering components and has the potential to be applied to information extraction or signal processing on these components separately.

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    5. Effect of differently sized nanoparticles' accumulation on the optical properties of ex vivo normal and adenomatous human colon tissue with OCT imaging and diffuse reflectance spectra

      Effect of differently sized nanoparticles' accumulation on the optical properties of ex vivo normal and adenomatous human colon tissue with OCT imaging and diffuse reflectance spectra

      Using optical coherence tomography (OCT) and diffuse reflectance spectra, we investigated the dynamics of titanium dioxide (TiO 2 ) nanoparticles, of different sizes, when penetrating and accumulating in human normal colon tissue (NC) and adenomatous colon tissue (AC). The process of nanoparticle penetration and accumulation in biotissue is accompanied by changes in the optical properties of tissue. Continuous OCT monitoring showed that, after application of TiO 2 nanoparticles, the OCT signal intensities of NC and ac both increase with time, and the larger nanoparticles tend to produce a greater signal enhancement in the same type of tissue. The average attenuation coefficient ...

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    6. Microvascular imaging: techniques and opportunities for clinical physiological measurements

      Microvascular imaging: techniques and opportunities for clinical physiological measurements

      The microvasculature presents a particular challenge in physiological measurement because the vessel structure is spatially inhomogeneous and perfusion can exhibit high variability over time. This review describes, with a clinical focus, the wide variety of methods now available for imaging of the microvasculature and their key applications. Laser Doppler perfusion imaging and laser speckle contrast imaging are established, commercially-available techniques for determining microvascular perfusion, with proven clinical utility for applications such as burn-depth assessment. Nailfold capillaroscopy is also commercially available, with significant published literature that supports its use for detecting microangiopathy secondary to specific connective tissue diseases in patients with ...

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    7. Measurement of elastic wave propagation velocity near tissue surface by optical coherence tomographyand laser Doppler velocimetry

      Measurement of elastic wave propagation velocity near tissue surface by optical coherence tomographyand laser Doppler velocimetry

      We demonstrate a new technique for measuring the velocity of elastic waves propagating near a tissue surface by swept-source optical coherence tomography (OCT). We establish a theory for estimating the elastic wave velocity from the OCT images taken with a slow mechanical scanning, which is experimentally verified using agar and tissue samples. The elastic wave velocity measured by this technique agrees well with previous results and that measured with a laser Doppler velocimeter. We also carry out some trial measurements of the elastic wave velocities of several tissue samples by this method.

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    8. Experimental research and observation of the skin response of mice with a second-degree scald duringirradiation by a CO 2 laser

      Experimental research and observation of the skin response of mice with a second-degree scald duringirradiation by a CO 2 laser

      Second-degree scalding is a common dermatological injury. Inappropriate treatment methods in clinical practice always produce scarring, and can lead to skin cancer and other complications in the longer term. In this study optical coherence tomography (OCT) combined with a skin detector was used to monitor the response of second-degree scalded skin tissue irradiated by a CO2 laser. The process of treatment of second-degree scalding was systematically studied from the perspective of tissue optics. The OCT signal intensity was stronger within the whole recovery period in the experimental group undergoing CO2 laser treatment, and the attenuation coefficient (μt) returned ...

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    9. Two-dimensional optical scanner with monolithically integrated glass microlens

      Two-dimensional optical scanner with monolithically integrated glass microlens

      A miniaturized two-dimensional forward optical scanner with a monolithically integrated glass microlens was developed for microendoscopic imaging applications. The fabricated device measures 2.26 × 1.97 × 0.62 mm 3 in size and a through-silicon microlens with a diameter of 400 µm and numerical aperture of 0.37 has been successfully integrated within the silicon layer. An XY stage structure with lens shuttle and comb actuators was designed, and proprietary glass isolation blocks were utilized in mechanical and electric isolation of X- and Y -axis actuators. Resonant frequencies of the stage in X and Y directions were 3.238 and ...

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    10. Low coherence interferometric second harmonic generation microscopy for non-destructive material testing using a broadband 1550 nm fs-fiber laser

      Low coherence interferometric second harmonic generation microscopy for non-destructive material testing using a broadband 1550 nm fs-fiber laser

      In this paper low coherence interferometric second harmonic generation (SHG) imaging is successfully demonstrated using a compact broadband fs-fiber laser operating around 1550 nm. In combination with linear optical coherence microscopy, this SHG technique is tailored for structural and functional investigations of surfaces and subsurface regions of non-biological samples, like corrosion sites formed on metals below organic coatings.

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    11. Simultaneous detection of optical retardation and axis orientation by polarization-sensitive full-field optical coherence microscopy for material testing

      Simultaneous detection of optical retardation and axis orientation by polarization-sensitive full-field optical coherence microscopy for material testing

      We present a polarization-sensitive full-field optical coherence microscopy modality which is capable of simultaneously delivering depth resolved information on the reflectivity, optical retardation and optical axis orientation. In this way local birefringence, inherent stress–strain fields and optical anisotropies can be visualized with high resolution, as exemplified for various technical material applications.

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    12. 800-nm-centered swept laser for spectroscopic optical coherence tomography

      800-nm-centered swept laser for spectroscopic optical coherence tomography

      The isosbestic point of oxy- and deoxy-hemoglobin at 800 nm is an important point in biomedical optical spectroscopic imaging. We have developed a novel swept laser centered at 800 nm and demonstrated its performance for spectroscopic optical coherence tomography. The measured −10 dB spectral bandwidth of the swept laser was 40 nm and averaged laser output power per sweep was 4 mW. This swept laser was incorporated into our OCT system and used to measure non-scattering liquid phantoms and blood samples. The measured maximum sensitivity and roll-off rate over a range of image depths were 112 dB and − 1.45 ...

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    13. In vivo enhancement of imaging depth for optical coherence tomography by eudermic agents on ridgedand meshed human skin

      In vivo enhancement of imaging depth for optical coherence tomography by eudermic agents on ridgedand meshed human skin

      Non-invasive skin analysis by optical coherence tomography (OCT) is limited because of the absorption and scattering properties of the tissue. There are several possibilities for enhancing OCT images. The purpose of this study was to demonstrate that image quality can be improved using the hyperosmolar agents glucose and glycerol while investigating human ridged and meshed skin areas, without causing damage to the tissue. The experiments were carried out on the palm and the forearm of ten volunteers. After application of the substances in the test area, the penetration depth and image contrast were measured at intervals of 5 min for ...

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    14. Doppler mapping of an alternating-sign flow with complex geometry using optical coherence tomography

      Doppler mapping of an alternating-sign flow with complex geometry using optical coherence tomography

      The method of sign-sensitive mapping of the given range of velocities in a flow with complex geometry based on the principles of optical coherence tomography is described. To produce an alternating-sign flow, the 1% aqueous intralipid solution and the tilted capillary entry with the contraction coefficient 4:1 are used. The mapping is controlled using two parameters, the value of one specific velocity (OSV) for mapping and the accuracy of its determination. The structure image and two OSV images (for positive and negative direction of motion) are obtained as a result of selecting and processing the relevant parts of the ...

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    15. Monitoring of glucose levels in mouse blood with noninvasive optical methods

      Monitoring of glucose levels in mouse blood with noninvasive optical methods

      We report the quantification/monitoring of glucose levels in a blood sample using optical diffuse reflectance (ODR) underlying variations in optical parameters with a white light source (at peak wavelength ~600 nm and range 450–850 nm) and in blood in vivo using M-mode optical coherence tomography (OCT) in terms of the translational diffusion coefficient ( D T ). In the ODR experiments, we have investigated two types of mono-dispersive particles, i.e. polystyrene microspheres (PMSs) with diameters of 1.4 μ m (variable concentrations) and 2.6 μ m (fixed concentration) in a water phantom by observing changes in the reduced scattering coefficient ...

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    16. A large-scan-angle piezoelectric MEMS optical scanner actuated by a Nb-doped PZT thin film

      A large-scan-angle piezoelectric MEMS optical scanner actuated by a Nb-doped PZT thin film

      Resonant 1D microelectromechanical systems (MEMS) optical scanners actuated by piezoelectric unimorph actuators with a Nb-doped lead zirconate titanate (PNZT) thin film were developed for endoscopic optical coherence tomography (OCT) application. The MEMS scanners were designed as the resonance frequency was less than 125 Hz to obtain enough pixels per frame in OCT images. The device size was within 3.4 mm × 2.5 mm, which is compact enough to be installed in a side-imaging probe with 4 mm inner diameter. The fabrication process started with a silicon-on-insulator wafer, followed by PNZT deposition by the Rf sputtering and Si bulk micromachining ...

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    17. Ultrahigh-Resolution Optical Coherence Tomography with LED-Phosphor-Based Broadband Light Source

      Ultrahigh-Resolution Optical Coherence Tomography with LED-Phosphor-Based Broadband Light Source

      This study proposed and demonstrated the potential use of LED phosphors as a simple light source for ultrahigh-resolution spectral-domain optical coherence tomography (SD-OCT) in the visible regime. Excited by a 405 nm diode laser, broadband spontaneous emission from three different LED phosphors was generated. The best axial resolution was 1.7 µm in air, and finally, corresponding three-dimensional (3D) ultrahigh-resolution SD-OCT imaging was performed with the proposed broadband light source.

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    18. Noniterative method of reconstruction optical coherence tomography images with improved lateralresolution in semitransparent media

      Noniterative method of reconstruction optical coherence tomography images with improved lateralresolution in semitransparent media

      A method of OCT imaging with a resolution throughout the investigated volume equal to the resolution in the best-focused region is described. It is based on summation of three-dimensional scattered field distributions at the wavelengths determined by OCT source spectral decomposition. A method of finding parameters needed for algorithmic realization of the summation is also proposed. The proposed approaches are tested on several model media, including biological ones.

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    19. Metrological reliability of optical coherence tomography in biomedical applications

      Metrological reliability of optical coherence tomography in biomedical applications

      Optical coherence tomography (OCT) has been proving to be an efficient diagnostics technique for imaging in vivo tissues, an optical biopsy with important perspectives as a diagnostic tool for quantitative characterization of tissue structures. Despite its established clinical use, there is no international standard to address the specific requirements for basic safety and essential performance of OCT devices for biomedical imaging. The present work studies the parameters necessary for conformity assessment of optoelectronics equipment used in biomedical applications like Laser, Intense Pulsed Light (IPL), and OCT, targeting to identify the potential requirements to be considered in the case of a ...

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    20. Broadband superluminescent diodes with bell-shaped spectra emitting in the range from 800 to 900 nm

      Broadband superluminescent diodes with bell-shaped spectra emitting in the range from 800 to 900 nm

      Quantum-well superluminescent diodes (SLD) with extremely thin active (AlGa)As and (InGa)As layers and centre wavelengths about 810, 840, 860 and 880 nm are experimentally studied. Their emission spectrum possesses the shape close to Gaussian, its FWHM being 30 – 60 nm depending on the length of the active channel and the level of pumping. Under cw injection, the output power of light-emitting modules based on such SLDs can amount to 1.0 – 25 mW at the output of a single-mode fibre. It is demonstrated that the operation lifetime of these devices exceeds 30000 hours. Based on the light-emitting modules ...

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      Mentions: Superlum
    21. Enhancement of the resolution of full-field optical coherence tomography by using a colour image sensor

      Enhancement of the resolution of full-field optical coherence tomography by using a colour image sensor

      The influence of white balance in a colour image detector on the resolution of a full-field optical coherence tomograph (FFOCT) is studied. The change in the interference pulse width depending on the white balance tuning is estimated in the cases of a thermal radiation source (incandescent lamp) and a white light emitting diode. It is shown that by tuning white balance of the detector in a certain range, the FFOCT resolution can be increased by 20 % as compared to the resolution, attained with the use of a monochrome detector.

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    22. Generation of a low divergent supercontinuum for mid-IR high power delivery through a large mode area photonic bandgap fiber

      Generation of a low divergent supercontinuum for mid-IR high power delivery through a large mode area photonic bandgap fiber

      We numerically report the feasibility of generating broadband low divergent supercontinuum covering the entire wavelength window of 1.5–3.5 μm from a 2.25 m long effectively single mode all solid, soft glass based, photonic bandgap fiber with mode area as large as 1100 μm 2 . Owing to its chosen fabrication, friendly geometry, and the chosen material composition, the proposed fiber-based light source should be useful as a mid-wave IR pulsed broadband light source for applications such as high power delivery, optical coherence tomography and mid-IR spectroscopy.

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    23. Kinetics of varnish long-term drying process monitored by a heterogeneous optical sensor system

      Kinetics of varnish long-term drying process monitored by a heterogeneous optical sensor system

      The drying process of an acrylic varnish film was monitored over 24 h by a heterogeneous optical sensor system. The system employs a fibre optic transducer based on Bragg gratings and optical coherence tomography, operating respectively around 1.55 and 1.3 µm. The sensor is able to provide information about the temporal evolution of temperature, mechanical deformation, thickness and average refractive index of the coating during the drying process. Resolutions for these optically measured parameters are 0.05 °C (temperature), 0.5 µε (strain), 1.5 µm (thickness) and 0.004 (refractive index). Besides, the sensor can detect the growth ...

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    24. Passive OCT probe head for 3D duct inspection

      Passive OCT probe head for 3D duct inspection

      A passive, endoscopic optical coherence tomography (OCT) probe has been demonstrated, incorporating an imaging fibre bundle and 45° conical mirror, and with no electromechanical components at the probe tip. Circular scanning, of the beam projected onto the proximal face of the imaging bundle, produces a corresponding circular scan at the distal end of the bundle. The beam is turned through 90° by the conical mirror and converted into a radially-scanned sample beam, permitting circumferential OCT scanning in quasi-cylindrical ducts. OCT images, displayed as polar plots and as 3D reconstructions, are presented, showing the internal profile of a metallic test sample ...

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    1-24 of 89 1 2 3 4 »
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