1. Articles from Changhuei Yang

    1-18 of 18
    1. Acoustic assisted phase conjugate optical tomography

      Acoustic assisted phase conjugate optical tomography

      A light microscope for imaging a sample containing one or more fluorescent agents, comprising a source for generating acoustic waves that are focused at a focus in the sample, wherein the acoustic waves frequency shift a frequency of light passing through the focus, thereby creating a frequency shifted light beam; at least one spatial light modulator (SLM) positioned to illuminate the sample with an output beam that is an optical phase conjugate of the frequency shifted light beam, wherein the output beam is a reflection of a first reference beam off one or more pixels of the SLM, and the ...

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    2. Image reconstruction by position and motion tracking

      Image reconstruction by position and motion tracking

      A system, method, and apparatus provide the ability to reconstruct an image from an object. A hand-held image acquisition device is configured to acquire local image information from a physical object. A tracking system obtains displacement information for the hand-held acquisition device while the device is acquiring the local image information. An image reconstruction system computes the inverse of the displacement information and combines the inverse with the local image information to transform the local image information into a reconstructed local image information. A display device displays the reconstructed local image information.

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    3. Congratulations to Jian Ren from Caltech a Winner of a 2012 Student Travel Grant Award

      Congratulations to Jian Ren from  Caltech a Winner of a 2012 Student Travel Grant Award
      Jian Ren from the California Institute of Technology is one of four winners of the OCT News 2012 student travel grant awards (see prior announcement Here). Below is a summary of his work. Glaucoma is one type of ophthalmic diseases, where ocular hypertension damages optical nerve, making it the second leading cause of blindness worldwide. One major cause of Open Angle Glaucoma is the poor outflow of aqueous humor through the Trabecular Meshwork (TM). Potential treatments include the micro-bypass stents, which are implanted in the TM and shunt fluid directly to the Schlemm’s Canal (SC) to reduce intraocular pressure ...
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    4. Quantitative differential interference contrast (DIC) microscopy and photography based on wavefront sensors

      Quantitative differential interference contrast (DIC) microscopy and photography based on wavefront sensors
      A wavefront microscope or camera utilizes a wavefront sensor to measure the local intensity and phase gradient of the wavefront and output image maps based on the intensity and phase gradient. A wavefront sensor provides a metal film having patterned structured two dimensional (2D) apertures that convert a phase gradient of a wavefront into a measurable form onto a photodetector array. A computer is used to analyze the data by separating signals projected and recorded on the array from the different apertures, predict a center of each projection, and sum signals for each projection to display the intensity while determining ...
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    5. Feature Of The Week 5/1/11: Caltech Researchers Develop an OCT Needle Probe for Investigating Open Angle Glaucoma

      Feature Of The Week 5/1/11: Caltech Researchers Develop an OCT Needle Probe for Investigating Open Angle Glaucoma
      Feature Of The Week 5/1/11: One major cause of Open Angle Glaucoma is the poor outflow of aqueous humor through the Trabecular Meshwork (TM). Potential treatments include the micro-bypass stents, which are implanted in the TM and shunt fluid directly to the Schlemm’s Canal (SC) to reduce intraocular pressure. Implanting the stent with the appropriate orientation near a major collector channel (CC) might maximize outflow of aqueous humor.As scleral tissue and the TM are not transparent to visible light, OCT using infrared light may be useful in visualizing and locating collector channels, hence could assist the ...
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    6. Ex vivo Optical Coherence Tomography Imaging of Collector Channels with a Scanning Endoscopic Probe

      Ex vivo Optical Coherence Tomography Imaging of Collector Channels with a Scanning Endoscopic Probe
      Abstract Purpose: To achieve high-fidelity optical coherence tomography (OCT) imaging of ex vivo collector channels (CCs) exiting Schlemm's canal (SC) using a paired angled rotating scanning endoscopic probe. Methods: An endoscopic probe was developed to guide an OCT laser beam onto human cadaver eye tissue samples to detect CCs. The prototype probe consisted of two gradient-index (GRIN) lenses, which were housed in two stainless steel needles respectively. The probe scanned the laser beam across a fan shape area by rotating the two GRIN lenses. We built a swept source based OCT system to provide the depth scans. Human cadaver ...
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    7. Manual-scanning optical coherence tomography probe based on position tracking

      Manual-scanning optical coherence tomography probe based on position tracking
      A method based on position tracking to reconstruct images for a manual-scanning optical coherence tomography (OCT) probe is proposed and implemented. The method employs several feature points on a hand-held probe and a camera to track the device’s pose. The continuous device poses tracking, and the collected OCT depth scans can then be combined to render OCT images. The tracking accuracy of the system was characterized to be about 6 um along two axes and 19 um along the third. A phantom target was used to validate the method. In addition, we report OCT images of a 54-stage Xenopus ...
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    8. Harmonically matched diffraction grating pair

      A method and device realize shallow gratings-based planar beam splitter/combiner. Non-trivial phase shifts between different ports of resulting interferometers are used to acquire full-field phase measurements. The non-trivial phase shifts between different ports of the planar beam splitter/combiner can be adjusted by simply shearing one grating with respect to the second grating. The two shallow diffraction gratings are harmonically-related and can be recorded on a single substrate for compact interferometric based schemes. During the recording process, the two gratings are aligned such that the grating planes and the grating vectors are parallel to that of each other. The ...
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    9. Systems and methods for phase measurements

      Preferred embodiments of the present invention are directed to systems for phase measurement which address the problem of phase noise using combinations of a number of strategies including, but not limited to, common-path interferometry, phase referencing, active stabilization and differential measurement. Embodiment are directed to optical devices for imaging small biological objects with light. These embodiments can be applied to the fields of, for example, cellular physiology and neuroscience. These preferred embodiments are based on principles of phase measurements and imaging technologies. The scientific motivation for using phase measurements and imaging technologies is derived from, for example, cellular biology at ...

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    10. Paired angled rotation scanning probes and methods of use

      Probes, and systems and methods for optically scanning a conical volume in front of a probe, for use with an imaging modality, such as Optical Coherence Tomography (OCT). A probe includes an optical fiber having a proximal end and a distal end and defining an axis, with the proximal end of the optical fiber being proximate a light source, and the distal end having a first angled surface. A refractive lens element is positioned proximate the distal end of the optical fiber. The lens element and the fiber end are both configured to separately rotate about the axis so as ...
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    11. Handheld forward-imaging needle endoscope for ophthalmic optical coherence tomography inspection

      Shuo Han, Marinko V. Sarunic, Jigang Wu et al. We report the narrowest to-date (21 gauge, 820-[mu]m-diam) handheld forward-imaging optical coherence tomography (OCT) needle endoscope and demonstrate its feasibility for ophthalmic OCT inspection. The probe design is based on paired-angle-rotation scanning (PARS), which enables a linear B-scan pat ... [J. Biomed. Opt. 13, 020505 (2008)] published Mon Apr 21, 2008.
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    12. 2-D PSTD Simulation of optical phase conjugation for turbidity suppression

      Turbidity Suppression via Optical Phase Conjugation (TS-OPC) is an optical phenomenon that uses the back propagation nature of optical phase conjugate light field to undo the effect of tissue scattering. We use the computationally efficient and accurate pseudospectral time-domain (PSTD) simulation ... [Opt. Express 15, 16005-16016 (2007)]
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    13. Forward scanning imaging optical fiber probe

      Forward scanning imaging optical fiber probe
      Probes, and systems and methods for optically scanning a conical volume in front of a probe, for use with an imaging modality, such as Optical Coherence Tomography (OCT). A probe includes an optical fiber having a proximal end and a distal end and defining an axis, with the proximal end of the optical fiber being proximate a light source, and the distal end having a first angled surface. A refractive lens element is positioned proximate the distal end of the optical fiber. The lens element and the fiber end are both configured to separately rotate about the axis so as ...
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    14. Method for optical coherence tomography imaging with molecular contrast

      Spatial information, such as concentration and displacement, about a specific molecular contrast agent, may be determined by stimulating a sample containing the agent, thereby altering an optical property of the agent. A plurality of optical coherence tomography (OCT) images may be acquired, at least some of which are acquired at different stimulus intensities. The acquired images are used to profile the molecular contrast agent concentration distribution of the sample.
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    15. System and method for low coherence broadband quadrature interferometry

      A quadrature broadband interferometry system and method obtains a complete complex interferometric signal instantaneously in both homodyne and heterodyne systems in a simple, compact, and inexpensive setup. This is accomplished by separating interferometric components from non-interferometric components in each of at least two detector signals of an interferometer having a number of N.times.N couplers, scaling the interferometric components, and generating real and imaginary parts of a complex interferometric signal from the scaled interferometric components. The detector signals preferably derive from a broadband light source coupled to the interferometer, and the number of N.times.N couplers may be ...
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    16. Theoretical comparison of the sensitivity of molecular contrast optical coherence tomography techniques

      Theoretical comparison of the sensitivity of molecular contrast optical coherence tomography techniques
      Molecular contrast optical coherence tomography (MCOCT) is an extension of OCT in which contrast resulting from the interaction of light with a contrast agent, leads to the enhanced visualization of a specific morphology or biochemical process in a target specimen. In order to improve the sensitivity and specificity of MCOCT, several spectroscopic techniques have recently been introduced which depend upon coherent detection of scattered light which has been modified by interaction with the molecules of interest in a sample. These techniques include harmonic generation, coherent anti-Stokes Raman scattering, linear absorption, and several different forms of pump-probe spectroscopy. We have developed ...
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    17. Methods and systems using field-based light scattering spectroscopy

      The present invention relates to systems and methods of field-based light scattering spectroscopy. These systems and methods provide for the diagnosis of tissue by measuring the size and distribution of cellular characteristics. Field based measurements provide phase information resulting from the interaction of scatterers within the material and the incident wavefront. These measurements can be used to provide three dimensional images of tissue.
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    1-18 of 18
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  2. Topics in the News

    1. (17 articles) Changhuei Yang
    2. (14 articles) California Institute of Technology
    3. (7 articles) Jigang Wu
    4. (5 articles) Jian Ren
    5. (3 articles) Henrick K. Gille
    6. (3 articles) Joseph A. Izatt
    7. (2 articles) Duke University
    8. (2 articles) Case Western Reserve University
    9. (2 articles) Michael A. Choma
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    12. (1 articles) Johns Hopkins University
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    15. (1 articles) University of São Paulo
    16. (1 articles) Massachusetts Institute of Technology
    17. (1 articles) L V Prasad Eye Institute
    18. (1 articles) Gong Je Seong
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    20. (1 articles) James G. Fujimoto
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    Manual-scanning optical coherence tomography probe based on position tracking Ex vivo Optical Coherence Tomography Imaging of Collector Channels with a Scanning Endoscopic Probe Feature Of The Week 5/1/11: Caltech Researchers Develop an OCT Needle Probe for Investigating Open Angle Glaucoma Congratulations to Jian Ren from  Caltech a Winner of a 2012 Student Travel Grant Award Factors Associated with Changes in Retinal Layers Following Acute Optic Neuritis: A Longitudinal Study Using Optical Coherence Tomography Relationship between N95 Amplitude of Pattern Electroretinogram and Optical Coherence Tomography Angiography in Open-Angle Glaucoma Historic Effort to 'End Blindness" Marks a Major Milestone with Leading Scientist Recognized for Pioneering Work at VIP Ceremony Featuring Tribute to Ruth Bader Ginsburg Healing and early stent coverage after ultrathin strut biodegradable polymer‐coated sirolimus‐eluting stent implantation: SiBi optical coherence tomography study Influences of hypomagnesemia on optic nerve and retinal vascular structure determined using optical coherence tomography angiography Repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography in myopic and postphotorefractive keratectomy eyes Vessel Density around Foveal Avascular Zone as a Potential Imaging Biomarker for Detecting Preclinical Diabetic Retinopathy: An Optical Coherence Tomography Angiography Study Vascular risk factors for optical coherence tomography-detected macular cysts: The Maastricht Study