1. Articles from adrian podoleanu

    1-24 of 74 1 2 3 »
    1. Apparatus and method for processing the signal in master slave interferometry and apparatus and method for master slave optical coherence tomography with any number of sampled depths

      Apparatus and method for processing the signal in master slave interferometry and apparatus and method for master slave optical coherence tomography with any number of sampled depths

      The present invention related to an apparatus and method for master slave interferometry, referred to as Complex Master Slave (CMS). The method and apparatus can be used to provide complex-valued measurements of a signal reflected from an axial position inside an object or of signals reflected from points at several axial positions inside an object.

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    2. Direct en-face, speckle-reduced images using angular-compounded Master–Slave optical coherence tomography

      Direct en-face, speckle-reduced images using angular-compounded Master–Slave optical coherence tomography

      In this paper, an angular compounding method to achieve speckle contrast reduction in optical coherence tomography (OCT) imaging is explored in detail. The angular compounding approach involves collecting multiple images at different angles of incidence, registering the images to correct for induced distortions, and then incoherently summing the images to reduce speckle. The method was experimentally demonstrated with a spectrometer-based Master–Slave enhanced OCT instrument capable of directly generating en-face images. We have investigated the impact of the angular range and number of averaged frames on the degree of speckle artefact reduction, as well as the effect on image resolution ...

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    3. Direct en-face, speckle-reduced images using angular-compounded Master-Slave optical coherence tomography

      Direct en-face, speckle-reduced images using angular-compounded Master-Slave optical coherence tomography

      In this paper, an angular compounding method to achieve speckle contrast reduction in optical coherence tomography (OCT) imaging is explored in detail. The angular compounding approach involves collecting multiple images at different angles of incidence, registering the images to correct for induced distortions, and then incoherently summing the images to reduce speckle. The method was experimentally demonstrated with a spectrometer-based Master-Slave enhanced OCT instrument capable of directly generating en-face images. We have investigated the impact of the angular range and number of averaged frames on the degree of speckle artefact reduction, as well as the effect on image resolution and ...

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    4. En-face optical coherence tomography/fluorescence endomicroscopy for minimally invasive imaging using a robotic scanner

      En-face optical coherence tomography/fluorescence endomicroscopy for minimally invasive imaging using a robotic scanner

      We report a compact rigid instrument capable of delivering en-face optical coherence tomography (OCT) images alongside (epi)-fluorescence endomicroscopy (FEM) images by means of a robotic scanning device. Two working imaging channels are included: one for a one-dimensional scanning, forward-viewing OCT probe and another for a fiber bundle used for the FEM system. The robotic scanning system provides the second axis of scanning for the OCT channel while allowing the field of view (FoV) of the FEM channel to be increased by mosaicking. The OCT channel has resolutions of 25  /  60  μm (axial/lateral) and can provide en-face images with ...

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    5. Progress in Multimodal En Face Imaging: feature introduction

      Progress in Multimodal En Face Imaging: feature introduction

      This feature issue contains papers that report on the most recent advances in the field of en face optical coherence tomography (OCT) and of combinations of modalities facilitated by the en face view. Hardware configurations for delivery of en face OCT images are described as well as specific signal and image processing techniques tailored to deliver relevant clinical diagnoses. The value of the en face perspective for enabling multimodality is illustrated by several combination modalities.

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    6. Feature Of The Week 04/28/2019: Real-Time High-Resolution Mid-Infrared OCT

      Feature Of The Week 04/28/2019: Real-Time High-ResolutionMid-Infrared OCT

      The potential for improving the penetration depth of optical coherence tomography systems by using light sources with longer wavelengths has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at a central wavelength of 4 µm and an axial resolution of 8.6 µm is demonstrated. The system produces two-dimensional cross-sectional images ...

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    7. Optical Coherence Tomography Investigations and Modeling of the Sintering of Ceramic Crowns

      Optical Coherence Tomography Investigations and Modeling of the Sintering of Ceramic Crowns

      Dental prostheses are sintered in ovens that sometimes suffer from a loss of calibration. This can lead to variations of the sintering temperature outside the range recommended by the manufacturer. Stress and even fractures in dental ceramics may occur, and this leads to the necessity to rebuild the dental construct. The aim of this work is to monitor the quality of sintering processes using an established biomedical imaging technique—optical coherence tomography (OCT). Conventional current procedures imply the fabrication of supplemental samples that add to the expenses and are only evaluated visually. To our knowledge, we were the first to ...

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    8. Akinetic swept laser apparatus and method for fast sweeping of the same

      Akinetic swept laser apparatus and method for fast sweeping of the same

      A detuned resonant mechanism is employed in a laser cavity to modulate in frequency the mode-locking mechanism to achieve high frequency tuning rates, exceeding MHz. The configuration of the laser is compatible with working at sweeping rates close to multiples of the cavity resonance frequency as well as with buffering for increased tuning speeds.

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    9. Down-conversion en-face optical coherence tomography

      Down-conversion en-face optical coherence tomography

      We present an optical coherence tomography (OCT) method that can deliver an en-face OCT image from a sample in real-time, irrespective of the tuning speed of the swept source. The method, based on the master slave interferometry technique, implements a coherence gate principle by requiring that the optical path difference (OPD) between the arms of an imaging interferometer is the same with the OPD in an interrogating interferometer. In this way, a real-time en-face OCT image can originate from a depth in the sample placed in the imaging interferometer, selected by actuating on the OPD in the interrogating interferometer, while ...

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    10. Noise of supercontinuum sources in spectral domain optical coherence tomography

      Noise of supercontinuum sources in spectral domain optical coherence tomography

      In this paper, we investigate the effect of pulse-to-pulse fluctuations of supercontinuum sources on the noise in spectral domain optical coherence tomography (OCT) images. The commonly quoted theoretical expression for the OCT noise is derived for a thermal light source, which is not suitable if a supercontinuum light source is used. We therefore propose a new, measurement-based OCT noise model that predicts the noise without any assumptions on the type of light source. We show that the predicted noise values are in excellent agreement with the measured values. The spectral correlation evaluated for the photodetected signal when using a supercontinuum ...

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    11. Real-time high-resolution mid-infrared optical coherence tomography

      Real-time high-resolution mid-infrared optical coherence tomography

      The potential for improving the penetration depth of optical coherence tomography systems by using light sources with longer wavelengths has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at a central wavelength of 4 µm and an axial resolution of 8.6 µm is demonstrated. The system produces two-dimensional cross-sectional images ...

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    12. Complex master-slave for long axial range swept-source optical coherence tomography

      Complex master-slave for long axial range swept-source optical coherence tomography

      Using complex master-slave interferometry, we demonstrate extended axial range optical coherence tomography for two commercially available swept sources, well beyond the limit imposed by their k -clocks. This is achieved without k -domain re-sampling and without engaging any additional Mach-Zehnder interferometer providing a k -clock signal to the digitizer. An axial imaging range exceeding 17 mm with an attenuation of less than 30 dB is reported using two commercially available swept sources operating at 1050 nm and a 100 kHz repetition rate. This procedure has more than trebled the range achievable using the k -clock signal provided by the manufacturers ...

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    13. Recovering distance information in spectral domain interferometry

      Recovering distance information in spectral domain interferometry

      This work evaluates the performance of the Complex Master Slave (CMS) method, that processes the spectra at the interferometer output of a spectral domain interferometry device without involving Fourier transforms (FT) after data acquisition. Reliability and performance of CMS are compared side by side with the conventional method based on FT, phase calibration with dispersion compensation (PCDC). We demonstrate that both methods provide similar results in terms of resolution and sensitivity drop-off. The mathematical operations required to produce CMS results are highly parallelizable, allowing real-time, simultaneous delivery of data from several points of different optical path differences in the interferometer ...

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    14. Real‐time High‐Resolution Mid‐infrared Optical Coherence Tomography

      Real‐time High‐Resolution Mid‐infrared Optical Coherence Tomography

      The potential for improving the penetration depth of optical coherence tomography systems by using increasingly longer wavelength light sources has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid‐infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid‐infrared spectral‐domain optical coherence tomography system operating at 4 µm central wavelength with an axial resolution of 8.6 µm is demonstrated. The system produces 2D cross ...

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    15. Feature Issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging Manuscript Deadline September 15, 2018

      Feature Issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging Manuscript Deadline September 15, 2018

      Biomedical Optics Express welcomes submissions to a feature issue on "Progress in Multimodal En-Face Imaging". Multimodal optical imaging certainly enriches the amount of information that can be retrieved from biological tissue. For this purpose, many different approaches have been combined, including optical coherence tomography (OCT), microscopy, scanning laser ophthalmoscopy (SLO), fluorescence imaging, multi-photon imaging, Raman spectroscopy, photoacoustics, and many more. This year marks 20 years from the publication of a first report on a combination of the old SLO, dating back from 1980, and of OCT, at that time a rather novel imaging technique as it was just invented in ...

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    16. Group refractive index and group velocity dispersion measurement by complex master slave interferometry

      Group refractive index and group velocity dispersion measurement by complex master slave interferometry

      This paper demonstrates that the complex master slave interferometry ( CMSI ) method used in spectral domain interferometry ( SDI ) can efficiently be used for accurate refractive index and group velocity dispersion measurements of optically transparent samples. For the first time, we demonstrate the relevance of the phase information delivered by CMSI for dispersion evaluations with no need to linearize data. The technique proposed here has been used to accurately measure the group refractive index and the group velocity dispersion of a strong dispersive sample (SF6 glass), and a weak dispersive one (distilled water). The robustness of the technique is demonstrated through the ...

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    17. Feature issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging

      Feature issue of Biomedical Optics Express: Progress in Multimodal En-Face Imaging

      Biomedical Optics Express welcomes submissions to a feature issue on "Progress in Multimodal En-Face Imaging". Multimodal optical imaging certainly enriches the amount of information that can be retrieved from biological tissue. For this purpose, many different approaches have been combined, including optical coherence tomography (OCT), microscopy, scanning laser ophthalmoscopy (SLO), fluorescence imaging, multi-photon imaging, Raman spectroscopy, photoacoustics, and many more. This year marks 20 years from the publication of a first report on a combination of the old SLO, dating back from 1980, and of OCT, at that time a rather novel imaging technique as it was just invented in ...

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    18. Q-switched based supercontinuum source towards low-cost ultra-high resolution optical coherence tomography

      Q-switched based supercontinuum source towards low-cost ultra-high resolution optical coherence tomography

      Supercontinuum (SC) light source is certainly one of the best option for ultra-high resolution optical coherence tomography (UHR-OCT). Over the last few years several demonstrations have been done for each commonly used wavelength range [1-2-3]. Nowadays, SC dedicated to UHR-OCT is a mature technology with turn-key commercially available system [4]. The new challenge to answer for SC source is the cost reduction one. In this study, we demonstrate that a Q-switched based SC (QS-SC) could be an alternative to the current state of the art SC based on a Mode-Locked laser (ML-SC). This QS-SC, whose cost is less than 15 ...

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    19. Two optical coherence tomography systems detect topical gold nanoshells in hair follicles, sweat ducts and measure epidermis

      Two optical coherence tomography systems detect topical gold nanoshells in hair follicles, sweat ducts and measure epidermis

      Optical coherence tomography (OCT) is an optical imaging technology that enables real time, high‐resolution, cross‐sectional and en face investigation of skin by detecting reflected broad‐spectrum near‐infrared light from tissue. OCT provides micron‐scale spatial resolution and millimeter‐scale depth of penetration [1]. Several commercial OCT systems with handheld probes targeted for Dermatology are now available [2].

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    20. In-vivo detection of the skin dermo-epidermal junction by ultrahigh resolution optical coherence tomography

      In-vivo detection of the skin dermo-epidermal junction by ultrahigh resolution optical coherence tomography

      The human skin is comprised by two layers; epidermis and dermis, separated by the dermo-epidermal junction (DEJ). The relevance of depicting DEJ and measurement of the epidermal thickness (ET) is e.g. seen for superficial skin cancers where delineation of DEJ is of prime prognostic importance. Another example is diagnosis of psoriasis where a thickened epidermis and a ridged DEJ is a hallmark. Histopathological examination of biopsied tissue is traditionally performed to trace DEJ and measure ET. An efficient and precise method to locate DEJ and measure ET is optical coherence tomography (OCT) which is an in vivo and non-invasive ...

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    21. Two Optical Coherence Tomography Systems detect Topical Gold Nanoparticles in Hair follicles, Sweat Ducts and Measure Epidermis

      Two Optical Coherence Tomography Systems detect Topical Gold Nanoparticles in Hair follicles, Sweat Ducts and Measure Epidermis

      Optical coherence tomography (OCT) is an optical imaging technology that enables real time, highresolution, cross-sectional and en face investigation of skin by detecting reflected broad-spectrum near-infrared light from tissue. OCT provides micron-scale spatial resolution and millimeter-scale depth of penetration [1]. Several commercial OCT systems with handheld probes targeted for Dermatology are now available [2]. The ability of OCT to achieve high diagnostic accuracy in skin diseases is hampered by the fact that not all diseases show sufficient contrast to be discriminated from normal skin. The challenge in realizing contrast enhancement in OCT imaging is to achieve signal from exogenous contrast ...

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    22. All-depth dispersion cancellation in spectral domain optical coherence tomography using numerical intensity correlations

      All-depth dispersion cancellation in spectral domain optical coherence tomography using numerical intensity correlations

      In ultra-high resolution (UHR-) optical coherence tomography (OCT) group velocity dispersion (GVD) must be corrected for in order to approach the theoretical resolution limit. One approach promises not only compensation, but complete annihilation of even order dispersion effects, and that at all sample depths. This approach has hitherto been demonstrated with an experimentally demanding ’balanced detection’ configuration based on using two detectors. We demonstrate intensity correlation (IC) OCT using a conventional spectral domain (SD) UHR-OCT system with a single detector. IC-SD-OCT configurations exhibit cross term ghost images and a reduced axial range, half of that of conventional SD-OCT. We demonstrate ...

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    23. Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography

      Assessment of Ductile, Brittle, and Fatigue Fractures of Metals Using Optical Coherence Tomography

      ome forensic in situ investigations, such as those needed in transportation (for aviation, maritime, road, or rail accidents) or for parts working under harsh conditions (e.g., pipes or turbines) would benefit from a method/technique that distinguishes ductile from brittle fractures of metals—as material defects are one of the potential causes of incidents. Nowadays, the gold standard in material studies is represented by scanning electron microscopy (SEM). However, SEM instruments are large, expensive, time-consuming, and lab-based; hence, in situ measurements are impossible. To tackle these issues, we propose as an alternative, lower-cost, sufficiently high-resolution technique, Optical Coherence Tomography ...

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    24. An overview of methods to mitigate artifacts in optical coherence tomography imaging of the skin

      An overview of methods to mitigate artifacts in optical coherence tomography imaging of the skin

      Background Optical coherence tomography (OCT) of skin delivers three-dimensional images of tissue microstructures. Although OCT imaging offers a promising high-resolution modality, OCT images suffer from some artifacts that lead to misinterpretation of tissue structures. Therefore, an overview of methods to mitigate artifacts in OCT imaging of the skin is of paramount importance. Speckle, intensity decay, and blurring are three major artifacts in OCT images. Speckle is due to the low coherent light source used in the configuration of OCT. Intensity decay is a deterioration of light with respect to depth, and blurring is the consequence of deficiencies of optical components ...

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    1-24 of 74 1 2 3 »
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    1. (74 articles) Adrian G. Podoleanu
    2. (73 articles) University of Kent
    3. (40 articles) Adrian Bradu
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    Optical mapping apparatus Extra long imaging range swept source optical coherence tomography using re-circulation loops Research Associate in Photonics/Optical Coherence Tomography/Nonlinear Microscopy/Wavefront Sensing at University of Kent Feature of the Week 03/20/2016: Closed Loop Tracked Doppler OCT Based Heart Monitor for the Drosophila Melanogaster Larvae Feature of the Week 05/08/2016: Complex Master Slave Interferometry Research Assistant/Associate in Biophotonics and Endoscopic Imaging at Imperial College London 7th International Conference on Lasers in Medicine: Advanced Laser Technologies in the Hands of Medicine July 2017 Timisoara, Romania Optical Coherence Tomography: Critical Tool to Manage Expectations after Cataract Extraction Improving the characterization of ex vivo human brain optical properties using high numerical aperture optical coherence tomography by spatially constraining the confocal parameters Choroidal, macular and ganglion cell layer thickness assessment in Caucasian children measured with spectral domain optical coherence tomography Examination of retinal vascular density changes via optical coherence tomography angiography in patients with glaucoma 3D reconstruction of coronary artery bifurcations from coronary angiography and optical coherence tomography: feasibility, validation, and reproducibility