1. Articles from sucbei moon

    1-11 of 11
    1. Ultrahigh-sensitive optical coherence elastography

      Ultrahigh-sensitive optical coherence elastography

      The phase stability of an optical coherence elastography (OCE) system is the key determining factor for achieving a precise elasticity measurement, and it can be affected by the signal-to-noise ratio (SNR), timing jitters in the signal acquisition process, and fluctuations in the optical path difference (OPD) between the sample and reference arms. In this study, we developed an OCE system based on swept-source optical coherence tomography (SS-OCT) with a common-path configuration (SS-OCECP). Our system has a phase stability of 4.2 mrad without external stabilization or extensive post-processing, such as averaging. This phase stability allows us to detect a ...

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    2. Fiber-based polarization-sensitive optical coherence tomography of a minimalistic system configuration

      Fiber-based polarization-sensitive optical coherence tomography of a minimalistic system configuration

      We present a very simple method of constructing a polarization-sensitive optical coherence tomography (PS-OCT) system. An ordinary fiber-based swept-source OCT system was reconfigured for PS-OCT by adding a long section of polarization-maintaining fiber in the sample arm. Two polarization modes of a large group-delay difference formed spatially distinguished polarization channels. The depth-encoded information on the polarization states was retrieved by an amplitude-based analysis. We found that our method provides an economic scheme of PS-OCT. It demonstrates that an ordinary OCT system can be easily reconfigured for PS-OCT imaging if it has sufficient margins in the imaging range.

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    3. Phase-stability optimization of swept-source optical coherence tomography

      Phase-stability optimization of swept-source optical coherence tomography

      Phase-resolved imaging of swept-source optical coherence tomography (SS-OCT) is subject to phase measurement instabilities involved with the sweep variation of a frequency-swept source. In general, optically generated timing references are utilized to track the variations imposed on OCT signals. But they might not be accurately synchronized due to relative time delays. In this research, we investigated the impact of the signal delays on the timing instabilities and the consequent deviations of the measured phases. We considered two types of timing signals utilized in a popular digitizer operation mode: a sweep trigger from a fiber Bragg grating (FBG) that initiates a ...

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    4. Lamellar keratoplasty using position-guided surgical needle and M-mode optical coherence tomography

      Lamellar keratoplasty using position-guided surgical needle and M-mode optical coherence tomography

      Deep anterior lamellar keratoplasty (DALK) is an emerging surgical technique for the restoration of corneal clarity and vision acuity. The big-bubble technique in DALK surgery is the most essential procedure that includes the air injection through a thin syringe needle to separate the dysfunctional region of the cornea. Even though DALK is a well-known transplant method, it is still challenged to manipulate the needle inside the cornea under the surgical microscope, which varies its surgical yield. Here, we introduce the DALK protocol based on the position-guided needle and M-mode optical coherence tomography (OCT). Depth-resolved 26-gage needle was specially designed, fabricated ...

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    5. VCSEL-based swept source for low-cost optical coherence tomography

      VCSEL-based swept source for low-cost optical coherence tomography

      We present a novel wavelength-swept laser source for optical coherence tomography (OCT) which is based on the conventional laser diode technology of the verticalcavity surface-emitting laser (VCSEL). In our self-heating sweep VCSEL (SS-VCSEL), a VCSEL device is simply driven by ramped pulses of currents in direct intensity modulation. The intrinsic property of VCSEL produces a frequency-swept output through the self-heating effect. By the injected current, the temperature of the active region is gradually increased in this effect. Consequently, it changes the wavelength of the laser output by itself. In this study, various characteristics of our SS-VCSEL were experimentally investigated for ...

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    6. Ultra-thin and flexible endoscopy probe for optical coherence tomography based on stepwise transitional core fiber

      Ultra-thin and flexible endoscopy probe for optical coherence tomography based on stepwise transitional core fiber

      We present an ultra-thin fiber-body endoscopy probe for optical coherence tomography (OCT) which is based on a stepwise transitional core (STC) fiber. In a minimalistic design, our probe was made of spliced specialty fibers that could be directly used for beam probing optics without using a lens. In our probe, the OCT light delivered through a single-mode fiber was efficiently expanded to a large mode field of 24 μm diameter for a low beam divergence. The size of our probe was 85 μm in the probe’s diameter while operated in a 160-μm thick protective tubing. Through theoretical and ...

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    7. Lens-free endoscopy probe for optical coherence tomography

      Lens-free endoscopy probe for optical coherence tomography

      We present an ultrathin fiber-optic endoscopy probe for optical coherence tomography (OCT), which is made of a series of fused optical fibers instead of the conventional scheme based on an objective lens. The large-core fiber with a core diameter of 20 μm was utilized for the probe, while a single-mode fiber of core diameter 8.2 μm mainly delivered the OCT light. Those fibers were spliced with a bridge fiber of an intermediate core size. The guided light was stepwise converted to a beam of a large mode-field diameter to be radiated with a larger depth of focus. We obtained ...

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    8. Mode-filtered large-core fiber for optical coherence tomography

      Mode-filtered large-core fiber for optical coherence tomography

      We have investigated the use of multimode fiber in optical coherence tomography (OCT) with a mode filter that selectively suppresses the power of the high-order modes (HOMs). A large-core fiber (LCF) that has a moderate number of guiding modes was found to be an attractive alternative to the conventional single-mode fiber for its large mode area and the consequentially wide Rayleigh range of the output beam if the HOMs of the LCF were efficiently filtered out by a mode filter installed in the middle. For this, a simple mode filtering scheme of a fiber-coil mode filter was developed in this ...

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    9. Reference spectrum extraction and fixed-pattern noise removal in optical coherence tomography

      Reference spectrum extraction and fixed-pattern noise removal in optical coherence tomography
      We present a new signal processing method that extracts the reference spectrum information from an acquired optical coherence tomography (OCT) image without a separate calibration step of reference spectrum measurement. The reference spectrum is used to remove the fixed-pattern noise that is a characteristic artifact of Fourier-domain OCT schemes. It was found that the conventional approach based on an averaged spectrum, or mean spectrum, is prone to be influenced by the high-amplitude data points whose statistical distribution is hardly randomized. Thus, the conventional mean-spectrum subtraction method cannot completely eliminate the artifact but may leave residual horizontal lines in the final ...
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    10. Semi-resonant operation of a fiber-cantilever piezotube scanner for stable optical coherence tomography endoscope imaging

      Semi-resonant operation of a fiber-cantilever piezotube scanner for stable optical coherence tomography endoscope imaging
      A forward-view optical coherence tomography (OCT) scanning catheter has been developed based on a fiber-cantilever piezotube scanner by using a semi-resonant scan strategy for a better scan performance. A compact endoscope catheter was fabricated by using a tubular piezoelectric actuator with quartered electrodes in combination with a resonant fiber cantilever. A cantilever weight was attached to the fiber cantilever to reduce the resonance frequency down to 63 Hz, well in the desirable range for Fourier-domain OCT. The resonant-cantilever scanner was driven at semi-resonance frequencies that were well out of the resonance peak but within a range of partial resonance. This ...
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    11. Normalization detection scheme for high-speed optical frequency-domain imaging and reflectometry

      We introduce a new signal detection method that can effectively suppress the effect of relative intensity noise (RIN) in optical frequency-domain reflectometry or imaging (OFDR/OFDI) schemes to enhance the sensitivity and dynamic range. In this method, spectral interferogram signal is normalized digitally by a spectral reference signal that contains the real-time spectrum and the RIN information of the frequency-swept source. Unlike the conventional balanced detection method that suppresses only additive intensity noises, we found that our proposed scheme removes both the additive and convolutional contributions of the RINs in the final interferogram signals. Experimental demonstrations were performed using a ...
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    1-11 of 11
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    1. (7 articles) UC Irvine
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    Semi-resonant operation of a fiber-cantilever piezotube scanner for stable optical coherence tomography endoscope imaging Reference spectrum extraction and fixed-pattern noise removal in optical coherence tomography Mode-filtered large-core fiber for optical coherence tomography Lens-free endoscopy probe for optical coherence tomography Ultra-thin and flexible endoscopy probe for optical coherence tomography based on stepwise transitional core fiber VCSEL-based swept source for low-cost optical coherence tomography Lamellar keratoplasty using position-guided surgical needle and M-mode optical coherence tomography Phase-stability optimization of swept-source optical coherence tomography Fiber-based polarization-sensitive optical coherence tomography of a minimalistic system configuration Evaluating Retinal and Choroidal Perfusion Changes After Ocular Massage of Healthy Eyes Using Optical Coherence Tomography Angiography Dermal Epidermal Junction Detection for Full-Field Optical Coherence Tomography Data of Human Skin by Deep Learning OctNET: A Lightweight CNN for Retinal Disease Classification from Optical Coherence Tomography Images