1. Articles from panomsak meemon

    1-26 of 26
    1. Comparative study of shear wave-based elastography techniques in optical coherence tomography

      Comparative study of shear wave-based elastography techniques in optical coherence tomography

      We compare five optical coherence elastography techniques able to estimate the shear speed of waves generated by one and two sources of excitation. The first two techniques make use of one piezoelectric actuator in order to produce a continuous shear wave propagation or a tone-burst propagation (TBP) of 400 Hz over a gelatin tissue-mimicking phantom. The remaining techniques utilize a second actuator located on the opposite side of the region of interest in order to create three types of interference patterns: crawling waves, swept crawling waves, and standing waves, depending on the selection of the frequency difference between the two ...

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    2. Spectral fusing Gabor domain optical coherence microscopy

      Spectral fusing Gabor domain optical coherence microscopy

      Gabor domain optical coherence microscopy (GD-OCM) is one of many variations of optical coherence tomography (OCT) techniques that aims for invariant high resolution across a 3D field of view by utilizing the ability to dynamically refocus the imaging optics in the sample arm. GD-OCM acquires multiple cross-sectional images at different focus positions of the objective lens, and then fuses them to obtain an invariant high-resolution 3D image of the sample, which comes with the intrinsic drawback of a longer processing time as compared to conventional Fourier domain OCT. Here, we report on an alternative Gabor fusing algorithm, the spectral-fusion technique ...

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    3. Crawling wave optical coherence elastography

      Crawling wave optical coherence elastography

      Elastography is a technique that measures and maps the local elastic property of biological tissues. Aiming for detection of micron-scale inclusions, various optical elastography, especially optical coherence elastography (OCE), techniques have been investigated over the past decade. The challenges of current optical elastography methods include the decrease in elastographic resolution as compared with its parent imaging resolution, the detection sensitivity and accuracy, and the cost of the overall system. Here we report for the first time, we believe, on an elastography technique—crawling wave optical coherence elastography (CRW-OCE)—which significantly lowers the requirements on the imaging speed and opens the ...

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    4. Simultaneous estimation of thickness and refractive index of layered gradient refractive index optics using a hybrid confocal-scan swept-source optical coherence tomography system

      Simultaneous estimation of thickness and refractive index of layered gradient refractive index optics using a hybrid confocal-scan swept-source optical coherence tomography system

      A hybrid confocal-scan swept-source optical coherence tomography metrology system was conceived for simultaneous measurements of the refractive index and thickness profiles of polymeric layered gradient refractive index (GRIN) optics. An uncertainty analysis predicts the metrology capability of the system and guides the selection of an optimum working numerical aperture. Experimental results on both a monolithic and a GRIN layered sheet are demonstrated to be in close agreement with theoretical predictions. Index measurement precision reached 0.0001 and 0.0008 for measuring 2.8 mm and ~300 µm thick layers, respectively. The thicknesses of these layers were simultaneously measured with a ...

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    5. Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms

      Angular scan optical coherence tomography imaging and metrology of spherical gradient refractive index preforms

      The fabrication of high-performance spherical gradient refractive index (S-GRIN) optics requires nondestructive metrology techniques to inspect the samples. We have developed an angular-scan, swept-source-based, Fourier-domain optical coherence tomography system centered at 1318 nm with 5 mm imaging depth capable of 180̊ polar scan and 360̊ azimuthal scan to investigate polymeric S-GRIN preforms. We demonstrate a method that enables simultaneous mapping of the group optical thickness, physical thickness, the radially-averaged group refractive index, and the transmitted wavefront of the S-GRIN preforms. The angular scan OCT imaging and metrology enables direct visualization, molding uniformity characterization, and optical property evaluations of the preforms ...

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    6. Design, implementation, and characterization of spectrometer-based spectral domain optical coherence tomography

      Design, implementation, and characterization of spectrometer-based spectral domain optical coherence tomography

      We report the implementation of a high speed and high resolution spectrometer-based spectral domain optical coherence tomography (SD-OCT) system. A high speed near-infrared spectrometer was designed and built, utilizing a high speed line-array CMOS detector and all off-the-shelf optical components. The acquisition speed of more than 100,000 spectra per second was achieved, enabling a high speed 3D imaging of the implemented SD-OCT system. Here, we report the performance characterization, i.e. resolution, imaging depth, and sensitivity of the implemented system. The penetration depth and depth resolution of the system are currently 2 mm and 14.1 μm, respectively. The ...

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      Mentions: Panomsak Meemon
    7. Implementation and characterization of phase-resolved Doppler optical coherence tomography method for flow velocity measurement

      Implementation and characterization of phase-resolved Doppler optical coherence tomography method for flow velocity measurement

      In this work, the system implementation and characterization of a Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) is presented. The phase-resolved Doppler technique was implemented on a custom built Frequency Domain OCT (FD-OCT) that was recently developed at Suranaree University of Technology. Utilizing Doppler phase changed relation in a complex interference signal caused by moving samples, PR-DOCT can produce visualization and characterization of flow activity such as blood flow in biological samples. Here we report the performance of the implemented PR-DOCT system in term of the Velocity Dynamic Range (VDR), which is defined by the range from the minimum to the ...

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      Mentions: Panomsak Meemon
    8. Nondestructive metrology by optical coherence tomography empowering manufacturing iterations of layered polymeric optical materials

      Nondestructive metrology by optical coherence tomography empowering manufacturing iterations of layered polymeric optical materials

      In recent years, there has been an ever-growing interest in exploring different optical materials and components to develop compact and effective optical systems. The design and fabrication of high-performance optics require nondestructive metrology techniques to inspect the samples. We have investigated the capability of optical coherence tomography (OCT) to nondestructively characterize layered polymeric materials. Using a custom developed Gabor-domain optical coherence microscopy system centered at 800 nm with 120 nm full width at half maximum enabling unprecedented 2 μ m resolution both laterally and axially in an 8     mm 3 volume, we investigated the internal structure of 50 μ m thick films ...

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    9. Optical Coherence Tomography Enabling Non Destructive Metrology of Layered Polymeric GRIN Material

      Optical Coherence Tomography Enabling Non Destructive Metrology of Layered Polymeric GRIN Material

      Gradient Refractive INdex (GRIN) optical components have historically fallen short of theoretical expectations. A recent breakthrough is the manufacturing of nanolayered spherical GRIN (S-GRIN) polymer optical elements, where the construction method yields refractive index gradients that exceed 0.08. Here we report on the application of optical coherence tomography (OCT), including micron-class axial and lateral resolution advances, as effective, innovative methods for performing nondestructive diagnostic metrology on S-GRIN. We show that OCT can be used to visualize and quantify characteristics of the material throughout the manufacturing process. Specifically, internal film structure may be revealed and data are processed to extract ...

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    10. Optical coherence tomography (OCT) apparatus, methods, and applications

      Optical coherence tomography (OCT) apparatus, methods, and applications

      A free-space Michelson Interferometer-based Dual Detection Frequency Domain-Optical Coherency Tomography (DD-FD-OCT) apparatus includes a non-polarizing beam splitter that can be used to misalign sample and reference beam paths to provide a stable .pi./2 phase shift between simultaneously detected interfering sample and reference beams to eliminate the mirror image created by Fourier transformation during image reconstruction. A hybrid fiber system Mach Zehnder Interferometer- and free-space Michelson Interferometer-based Dual Detection Frequency Domain-Doppler Optical Coherency Tomography (DD-FD-DOCT) apparatus provides higher power efficiency and thus better sensitivity compared to the free-space DD-FD-OCT. Both DD-FD-OCT systems enable functional imaging with the contrasts of Doppler ...

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    11. Systems and methods for performing Gabor-domain optical coherence microscopy

      Systems and methods for performing Gabor-domain optical coherence microscopy

      In one embodiment, imaging a medium under evaluation includes generating acquired images of the medium, each acquired image comprising a cross-sectional image along a lateral and a depth direction of the medium that results from scanning the medium at a different depths, filtering each acquired image to remove out-of-focus portions of the images and generate filtered images, and merging the filtered images to form a high-resolution fused image.

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    12. Nondestructive metrology of layered polymeric optical materials using optical coherence tomography

      Nondestructive metrology of layered polymeric optical materials using optical coherence tomography

      In recent years, there has been an ever-growing interest in exploring novel, highly efficient optical materials to develop compact and effective optical components. The design and fabrication of high-performance optics require nondestructive metrology techniques to inspect the samples. We have investigated the capability of optical coherence tomography (OCT) to nondestructively characterize layered polymeric materials. Using a swept-source OCT system with a wavelength range of 1.25 - 1.41 μm, we achieved micron-scale three-dimensional visualization of the interior structures and details of the layered polymers. The 3D OCT imaging also enabled accurate identification of the locations of defects within the samples ...

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    13. Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT

      Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT

      We analyze the three most common profiles of scanning functions for galvanometer-based scanners (GSs): the sawtooth, triangular and sinusoidal functions. They are determined experimentally with regard to the scan parameters of the input signal (i.e., frequency and amplitude). We study the differences of the output function of the GS measured as the positional error of the oscillatory mirror from the ideal function given by the input signal of the device. The limits in achieving the different types of scanning functions in terms of duty cycle and linearity are determined experimentally for the possible range of scan parameters. Of particular ...

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    14. Systems and methods for generating a tunable laser beam

      Systems and methods for generating a tunable laser beam
      Systems and methods of generating a tunable laser beam are disclosed. An example method includes: generating coherent optical beams from a plurality of semiconductor optical amplifiers (SOAs); combining the coherent optical beams into a combined coherent optical beam; and tuning the combined beam to a selected frequency range to output a coherent optical beam having only the selected frequency range. In some embodiments, the SOAs are arranged in parallel within a resonant cavity, and each coherent optical beam has a different center wavelength that overlaps in bandwidth with another one of the coherent optical beams.
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    15. Broadband Fourier-domain mode-locked lasers

      Broadband Fourier-domain mode-locked lasers
      Abstract  Broadband, high-speed wavelength-swept lasers can substantially enhance applications in optical coherence tomography, chemical spectroscopy, and fiber-optic sensing. We report the demonstration of Fourier-domain mode-lock lasers operating at about 90 kHz effective sweep rate over a 158 nm sweep range using a single-band design and over a 284 nm sweep range across the 1.3 μm to 1.5 μm wavelength spectrum using a unique broadband design. A novel dual-detection full-range Fourier-domain optical coherence tomography system is developed which provides 7 μm axial resolution (in air) at about 90 kHz axial scan rate for mirror-image resolved Doppler imaging in a ...
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    16. Swept-source based, single-shot, multi-detectable velocity range Doppler optical coherence tomography

      Swept-source based, single-shot, multi-detectable velocity range Doppler optical coherence tomography
      Phase-Resolved Doppler Optical Coherence Tomography (PR-DOCT) allows visualization and characterization of the location, direction, velocity, and profile of flow activity embedded in a static sample structure. The detectable Velocity Dynamic Range (VDR) of each particular PR-DOCT system is governed by a detectable Doppler phase shift, a flow angle, and an acquisition time interval used to determine the Doppler phase shift. In general, the lower boundary of the detectable Doppler phase shift is limited by the phase stability of the system, while the upper boundary is limited by the π phase ambiguity. For a given range of detectable Doppler phase shift ...
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    17. Liquid lens enabled optical coherence microscope with Gabor fusion

      Liquid lens enabled optical coherence microscope with Gabor fusion
      A custom optical microscope with an integrated liquid lens to enable an extended depth imaging in biological tissue has been fabricated and shown to provide subcellular resolution using Gabor image fusion in an optical coherence tomography setup. In this paper, we report on the development and assessment path of this technology over the last few years. Specifically, we report on the optical design as well as the MTF prediction and experimental measurements of the new optical microscope head. The microscope head was integrated in a custom optical coherence microscopy setup that is presented. Images of an African frog tadpole, ex ...
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    18. Doppler imaging with dual-detection full-range frequency domain optical coherence tomography

      Doppler imaging with dual-detection full-range frequency domain optical coherence tomography
      Most of full-range techniques for Frequency Domain Optical Coherence Tomography (FD-OCT) reported to date utilize the phase relation between consecutive axial lines to reconstruct a complex interference signal and hence may exhibit degradation in either mirror image suppression performance or detectable velocity dynamic range or both when monitoring a moving sample such as flow activity. We have previously reported a technique of mirror image removal by simultaneous detection of the quadrature components of a complex spectral interference called a Dual-Detection Frequency Domain OCT (DD-FD-OCT) [Opt. Lett. 35, 1058-1060 (2010)]. The technique enables full range imaging without any loss of acquisition ...
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    19. Assessment of a liquid lens enabled in vivo optical coherence microscope

      Assessment of a liquid lens enabled in vivo optical coherence microscope
      The optical aberrations induced by imaging through skin can be predicted using formulas for Seidel aberrations of a plane-parallel plate. Knowledge of these aberrations helps to guide the choice of numerical aperture (NA) of the optics we can use in an implementation of Gabor domain optical coherence microscopy (GD-OCM), where the focus is the only aberration adjustment made through depth. On this basis, a custom-designed, liquid-lens enabled dynamic focusing optical coherence microscope operating at 0.2 NA is analyzed and validated experimentally. As part of the analysis, we show that the full width at half-maximum metric, as a characteristic descriptor ...
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    20. Dual detection full range frequency domain optical coherence tomography

      Dual detection full range frequency domain optical coherence tomography
      It has been shown that frequency domain optical coherence tomography (FD-OCT) systems achieve higher sensitivities compared to time domain optical coherence tomography (OCT) systems. However, the obscure object structure due to the mirror image generated by the Fourier transform is one of the remaining issues in the FD-OCT. We designed and developed what we believe to be a novel full range FD-OCT system that we refer to as the dual detection full range frequency domain optical coherence tomography (DD-FDOCT) that enables the instantaneous retrieval of quadrature components of the complex interferometric signal. The DD-FDOCT system enables full range imaging without ...
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    21. Gabor-based fusion technique for Optical Coherence Microscopy

      Gabor-based fusion technique for Optical Coherence Microscopy
      We recently reported on an Optical Coherence Microscopy technique, whose innovation intrinsically builds on a recently reported - 2 μm invariant lateral resolution by design throughout a 2 mm cubic full-field of view - liquid-lens-based dynamic focusing optical probe [Murali et al.,Optics Letters 34, 145-147, 2009]. We shall report in this paper on the image acquisition enabled by this optical probe when combined with an automatic data fusion method developed and described here to produce an in-focus high resolution image throughout the imaging depth of the sample. An African frog tadpole (Xenopus laevis) was imaged with the novel probe and the ...
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    22. Gabor domain optical coherence microscopy

      Gabor domain optical coherence microscopy
      In this paper, we present a developing technology targeted at clinical imaging, Gabor Domain Optical Coherence Microscopy (GD-OCM), which combines the high resolution imaging of optical coherence microscopy (OCM), high imaging speed of Fourier domain optical coherence tomography (FD-OCT), and invariant lateral resolution of our custom designed dynamic focusing objective. A high lateral resolution optical design of a dynamic-focusing optical probe with no moving parts, which provides an invariant resolution of currently < 3 µm across a 2mm full-field of view and 2mm imaging depth, is presented. Furthermore, an acquisition scheme (using the probe) that is capable of performing automatic real ...
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    23. Dual-reference full-range frequency domain optical coherence tomography

      Dual-reference full-range frequency domain optical coherence tomography
      It has been shown that frequency domain optical coherence tomography (FD-OCT) systems achieve higher sensitivities compared to time domain OCT systems. However, the obscure object structure due to the mirror image generated by the Fourier transform is one of the main problems in FD-OCT. We designed and developed a novel full range FD-OCT system that we refer to as the dual-reference full-range FD-OCT (DR-FDOCT) that enables doubling the imaging depth by removing mirror images generated from the Fourier transform of the detected real-valued spectra. The DR-FDOCT system enables full-range imaging without any loss of speed and is less sensitive to ...
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    24. Gabor domain optical coherence microscopy

      Gabor domain optical coherence microscopy
      Optical Coherence Microscopy (OCM) is an emerging technology capable of depth sectioning of biological tissue at the micrometer scale. In this paper, we propose a developing technology we call Gabor Domain Optical Coherence Microscopy (GD-OCM), whose innovation is two folds: (1) A high lateral resolution optical design of a dynamic-focusing optical probe with no moving parts, which provides an invariant resolution of currently 3 µm across a 2mm full-field of view and 2mm imaging depth by design; (2) An acquisition scheme (using the probe) that is capable of performing automatic data fusion to render an in-focus high resolution image throughout ...
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    25. Determination of the coherency matrix of a broadband stochastic electromagnetic light beam

      Determination of the coherency matrix of a broadband stochastic electromagnetic light beam

      The statistical ensemble of a fluctuating, statistically-stationary electromagnetic light beam is presented in terms of a 2 2 matrix, so-called coherency matrix. The method to determine such matrix for a quasi-monochromatic light beam has been proposed for many years. In this paper, we demonstrate that the method needs to be only slightly modified to determine the matrix elements of a broadband stochastic electromagnetic light beam, if one uses the representation of statistical wave fields in the space-frequency domain. The implementation of the method is demonstrated, and the coherency matrix measurement is validated using a well-defined elliptically polarized beam.

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    26. Optical design of a dynamic focus catheter for high-resolution endoscopic optical coherence tomography

      Optical design of a dynamic focus catheter for high-resolution endoscopic optical coherence tomography
      The optical system design of a dynamic focus endoscopic probe for optical coherence tomography is reported. The dynamic focus capability is based on a liquid lens technology that provides variable focus by changing its curvatures in response to an electric field variation. The effects of a cylindrical exit window present, in practice, for a catheter were accounted for. Degradation in image quality caused by this window was corrected to get diffraction limited imaging performance. As a result, the dynamically focusing catheter with a lateral resolution ranging from 4 to 6 μm through an ∼5mm imaging distance was designed without mechanically ...
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    1-26 of 26
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    1. (26 articles) Panomsak Meemon
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    3. (18 articles) University of Rochester
    4. (17 articles) Kye-Sung Lee
    5. (14 articles) University of Central Florida
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    Optical design of a dynamic focus catheter for high-resolution endoscopic optical coherence tomography Dual-reference full-range frequency domain optical coherence tomography Gabor domain optical coherence microscopy Gabor-based fusion technique for Optical Coherence Microscopy Dual detection full range frequency domain optical coherence tomography Assessment of a liquid lens enabled in vivo optical coherence microscope Gabor domain optical coherence microscopy Doppler imaging with dual-detection full-range frequency domain optical coherence tomography Liquid lens enabled optical coherence microscope with Gabor fusion Broadband Fourier-domain mode-locked lasers Feature Of The Week 07/22/2019: Tsinghua University Demonstrates A “Sparse Sampled” Smart CCD Camera for Compressed Sensing Optical Coherence Tomography. An Unknown Tubular Structure on Optical Coherence Tomography After Revascularization in Chronic Totally Occluded Lesion