1. Articles from Changho Chong

    1-16 of 16
    1. Optical coherence tomography with a fizeau-type interferometer

      Optical coherence tomography with a fizeau-type interferometer

      An OCT system includes a light source configured to generate an optical beam, a Fizeau-type interferometer configured to receive the optical beam and produce an interference pattern, a detector configured to receive the interference pattern and produce an image signal, and a processing circuit including a processor and a memory, the memory being structured to store instructions that are executable by the processor to cause the processor to receive the image signal from the detector and generate an OCT image based on the image signal. The Fizeau-type interferometer includes a scanning element configured to receive the optical beam and direct ...

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    2. Dual wavelength resampling system and method

      Dual wavelength resampling system and method

      An optical coherence tomography (OCT) system combining multiple wavelengths is generally described. In an example, the OCT system includes multiple wavelength swept light sources. The system further includes an interferometer into which light from the light sources is directed and a detector configured to produce an imaging sample signal based on light received from the interferometer. The system also includes a splitter configured to split light from at least one of light sources before the light reaches the interferometer. The system also includes a wavelength reference filter having an equal interval frequency comb and a signal processing circuit. The wavelength ...

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    3. Biometry measurements using a new large-coherence–length swept-source optical coherence tomographer

      Biometry measurements using a new large-coherence–length swept-source optical coherence tomographer

      Purpose To evaluate the repeatability and reproducibility of the measurements obtained with the Argos, a new biometer with swept-source optical coherence tomography (SS-OCT), and to compare them with the results obtained with the IOLMaster 500 (partial-coherence interferometry [PCI]) and the Lenstar LS 900 (optical low-coherence reflectometry [OLCR]) biometers. Setting Private practice, Lynwood, California, USA. Design Prospective observational study. Methods All measurements were performed with the SS-OCT tomographer, the PCI biometer, and the OLCR biometer. Results Eyes (n = 107) were measured to evaluate the axial length (AL), central corneal thickness (CCT), aqueous depth, anterior chamber depth (ACD), lens thickness, pupil size ...

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    4. Optical Coherence Tomography System With Multiple Sample Paths

      Optical Coherence Tomography System With Multiple Sample Paths

      Improved optical coherence tomography (OCT) imaging systems are generally described. In an example, an OCT imaging system includes a tunable laser source, an interferometer, a splitter, and a detector. The tunable laser source is configured to provide a wavelength-scanned beam. The interferometer is configured to split the wavelength-scanned beam into a reference beam and an object beam. The splitter is configured to split the object beam into a first path corresponding to an anterior chamber imaging component and a second path corresponding to a retinal imaging component. The detector is configured to detect a signal caused by interference between the ...

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    5. Optical coherence tomography system and optical coherence tomography method

      Optical coherence tomography system and optical coherence tomography method
      A tunable light source 10 for varying emission wavelength periodically and an optical interferometer are used. A reflector is disposed at a measurement position, a light interference signal is A/D converted at a regular time interval, and data numbers at timing giving peak and bottom are calculated according to a least-squares method. Based on this, an approximate equation is calculated according to polynomial approximation and a sequence including the number of exponentiation of 2 and converting the data number at a regular frequency interval is calculated. Then, by disposing a measured target at the measurement position, calculating the necessary ...
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    6. Swept source type optical coherent tomography system

      Swept source type optical coherent tomography system
      A surface emission laser light source is used as a tunable laser light source. Since the surface emission laser light source can realize a broad frequency scanning range at a high speed and in the single mode, a coherent length is longer than that of a multi mode light source. For this reason, when a tomography image is calculated by executing the Fourier transform for an output obtained from an interference optical device, measuring depth can be deepened.
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    7. MEMS scanner based swept source laser for optical coherence tomography

      MEMS scanner based swept source laser for optical coherence tomography
      We developed a swept source laser using a micro electro mechanical systems (MEMS) scanner mirror, and demonstrated optical coherence tomography. To enable both the wide tuning wavelength range and high scanning frequency, we introduced 2-degree-of-freedom(2-DOF) MEMS scanner mirror. A tunable optical filter is composed of a MEMS scanner mirror and a diffraction grating which is arranged in Littrow configuration. We built a swept source laser which has a wavelength range of 143 nm, center wavelength of 1304 nm, and a peak power of 16 mW. OCT measurements are performed at a rate of 17.9 kHz and doubled 35 ...
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    8. Optical coherence tomography imaging based on non-harmonic analysis

      A new processing technique called Non-Harmonic Analysis (NHA) is proposed for OCT imaging. Conventional Fourier-Domain OCT relies on the FFT calculation which depends on the window function and length. Axial resolution is counter proportional to the frame length of FFT that is limited by the swept range of the swept source in SS-OCT, or the pixel counts of CCD in SD-OCT degraded in FD-OCT. However, NHA process is intrinsically free from this trade-offs; NHA can resolve high frequency without being influenced by window function or frame length of sampled data. In this study, NHA process is explained and applied to ...
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    9. In vivo imaging of human labial glands using advanced optical coherence tomography

      Objective Optical coherence tomography (OCT) has emerged as a high-resolution noninvasive clinical imaging application. The purpose of this study was to show OCT images of human labial glands obtained using a swept-source (SS) OCT system. Study design Labial gland OCT imaging was carried out using our new SS-OCT system for 5 healthy volunteers using a hand-held in vivo OCT scanning probe. The labial tissue was scanned in a superior to inferior direction in 2 and 3 dimensions. Results The resulting 2- and 3-dimensional ultrahigh-resolution images of in vivo OCT human labial minor salivary glands revealed the epithelium, connective tissue, lobes ...
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    10. Evaluation of oral vascular anomalies using optical coherence tomography

      Optical coherence tomography (OCT) is a new method of biomedical imaging that can generate high-resolution, cross-sectional images of microstructures. The purpose of this study was to present the first OCT images of oral vascular anomalies using a new advanced OCT scanner that we have developed, and to discuss the application of our system for oral soft tissues. Knowledge of the size and area of the vascular structures can be useful for the diagnosis and choice of the best treatment. Before excision, oral vascular malformations were assessed by OCT in vivo. Histopathological sections were taken and compared with the OCT images ...
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    11. Large coherence length swept source for axial length measurement of the eye

      We present and demonstrate a swept source with a large coherence length using a quasi-phase continuous tuning (QPCT) technique. QPCT is a method of minimizing the phase shift per round trip with respect to the tunable filter so that the resonance of lasing becomes high, resulting in high finesse of ... [Appl. Opt. 48, D144-D150 (2009)]
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    12. Spectral narrowing effect by quasi-phase continuous tuning in high-speed wavelength-swept light source

      Spectral narrowing effect by quasi-phase continuous tuning in high-speed wavelength-swept light source
      This paper reports on a technique to improve the coherence length of a high-speed wavelength swept laser. The wavelength swept laser comprises a pigtailed semiconductor optical amplifier and a wavelength-scanning filter in a fiber extended cavity configuration. The laser operates in the 1310 nm wavelength region. The tunable filter consists of a diffraction grating and polygon mirror scanner. Littrow arrangement of external cavity in a specific geometry realizes the quasi-phase continuous tuning over wavelength range emphasizing coherent amplification of cavity modes resulting in spectral narrowing of the instantaneous linewidth to about 0.06nm. Improvement by a factor of two is ...
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    13. Tunable fiber laser light source

      An optical fiber loop has a gain medium having a gain at an oscillation wavelength and optical circulators 13 and 14. Collimate lenses 22 and 24 enlarge light bean taken from the optical circulators 13 and 14. A polygon mirror 25 is provided on the light axis, and is rotated. A diffraction grating 27 is provided at the receiving position of the light reflected by the polygon mirror 25, and is of a Littrow configuration which reflects the light in the same direction as the incident light. A selected wavelength changes according to an incident angle to the diffraction grating ...
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    14. High-Speed Wavelength-Swept Laser Source With High-Linearity Sweep for Optical Coherence Tomography

      High-Speed Wavelength-Swept Laser Source With High-Linearity Sweep for Optical Coherence Tomography
      Summary:This paper reports on a high-speed, wide-range, wavelength-swept laser operating at 1310 nm with highly linear sweep performance for optical coherence tomography (OCT) applications. The simple and robust laser comprises a pigtailed semiconductor optical amplifier and a wavelength-scanning filter in an extended fiber cavity configuration. The tunable filter consists of a diffraction grating and polygon mirror scanner. A photodiode is used to generate a start trigger signal synchronized to start of each frequency sweep. Intracavity prism beam expanders are aligned to provide constant laser linewidth and linear frequency sweep. The laser exhibits a peak power of 15 mW. The ...
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    15. Optical deflection probe and optical deflection probe device

      An optical fiber transmits signal light and the excitation light for driving an actuator each having a different wavelength to a probe. In the probe, the signal light and excitation light are separated from each other by an optical filter and the excitation light is irradiated to a photo diode. The signal light is supplied to a MEMS mirror unit. Then, the MEMS mirror unit is driven by an electromotive force obtained by the photo diode. In this manner, by modulating intensity of the excitation light, the signal light can be deflected
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    1-16 of 16
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  2. Topics in the News

    1. (16 articles) Changho Chong
    2. (16 articles) Santec
    3. (6 articles) Atsushi Morosawa
    4. (5 articles) Tooru Sakai
    5. (3 articles) Takuya Suzuki
    6. (3 articles) Kouki Totsuka
    7. (3 articles) National Institutes of Health
    8. (2 articles) Tokyo Medical & Dental University
    9. (2 articles) Yasunori Sumi
    10. (2 articles) Tohru Kurabayashi
    11. (2 articles) Nobuyoshi Ozawa
    12. (1 articles) University of Pennsylvania
    13. (1 articles) National Eye Institute
    14. (1 articles) Columbia University
    15. (1 articles) University of Iowa
    16. (1 articles) University of Rochester
    17. (1 articles) Mona K. Garvin
    18. (1 articles) Bo Yu
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    High-Speed Wavelength-Swept Laser Source With High-Linearity Sweep for Optical Coherence Tomography Spectral narrowing effect by quasi-phase continuous tuning in high-speed wavelength-swept light source MEMS scanner based swept source laser for optical coherence tomography Swept source type optical coherent tomography system Vitreous Seeding in Retinocytoma: Importance of Optical Coherence Tomography Utility of Spectral-Domain Optical Coherence Tomography in Differentiating Papilledema From Pseudopapilledema: A Prospective Longitudinal Study Visualizing and quantifying cutaneous microvascular reactivity in humans using optical coherence tomography: Impaired dilator function in diabetes Optical Coherence Tomography of Outer Retinal Hyper-Reflectivity, Neovascularization and Pigment in Type 2 Macular Telangiectasia Early Detection of Incipient Retinal Pigment Epithelium Atrophy Overlying Drusen with Fundus Autofluorescence vs. Spectral Domain Optical Coherence Tomography Association of ABO blood groups and non-culprit plaque characteristics in acute coronary syndrome: an optical coherence tomography study Don't be afraid of the dark - OCT angiography through a black intraocular lens Postdoc Opening at The Department of Health Technology at the Technical University of Denmark (DTU)