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Email Address
Atomic, Molecular and Optical Physics
Neuroscience and Neurobiology
Research Projects
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Associate Professor
Dept. of Bioengineering, School of Engineering and Applied Sciences Dept. of Neuroscience, Perelman School of Medicine University of Pennsylvania Philadelphia, PA, USA
Research Interests

Search Results

Now showing 1 - 3 of 3
  • Publication
    Overcoming the Diffraction Limit Using Multiple Light Scattering in a Highly Disordered Medium
    (2011-07-06) Choi, Youngwoon; Fang-Yen, Christopher; Yang, Taeseok Daniel; Kang, Pilsung; Lee, Kyoung Jin; Dasari, Ramachandra R.; Feld, Michael S.; Choi, Wonshik
    We report that disordered media made of randomly distributed nanoparticles can be used to overcome the diffraction limit of a conventional imaging system. By developing a method to extract the original image information from the multiple scattering induced by the turbid media, we dramatically increase a numerical aperture of the imaging system. As a result, the resolution is enhanced by more than 5 times over the diffraction limit, and the field of view is extended over the physical area of the camera. Our technique lays the foundation to use a turbid medium as a far-field superlens.
  • Publication
    Scanner-Free and Wide-Field Endoscopic Imaging by Using a Single Multimode Optical Fiber
    (2012-11-12) Choi, Youngwoon; Fang-Yen, Christopher; Yoon, Changhyeong; Kim, Moonseok; Yang, Taeseok Daniel; Dasari, Ramchandra R; Lee, Kyoung Jin; Choi, Wonshik
    A single multimode fiber is considered an ideal optical element for endoscopic imaging due to the possibility of direct image transmission via multiple spatial modes. However, the wave distortion induced by the mode dispersion has been a fundamental limitation. In this Letter, we propose a method for eliminating the effect of mode dispersion and therefore realize wide-field endoscopic imaging by using only a single multimode fiber with no scanner attached to the fiber. Our method will potentially revolutionize endoscopy in various fields encompassing medicine and industry.
  • Publication
    Three-dimensional differential interference contrast microscopy using synthetic aperture imaging
    (2012-02-23) Kim, Moonseok; Fang-Yen, Christopher; Choi, Youngwoon; Sung, Yongjin; Kim, Kwanhyung; Dasari, Ramachandra R; Feld, Michael S; Choi, Wonshik
    We implement differential interference contrast (DIC) microscopy using high-speed synthetic aperture imaging that expands the passband of coherent imaging by a factor of 2.2. For an aperture synthesized coherent image, we apply for the numerical post-processing and obtain a high-contrast DIC image for arbitrary shearing direction and bias retardation. In addition, we obtain images at different depths without a scanning objective lens by numerically propagating the acquired coherent images. Our method achieves high-resolution and high-contrast 3-D DIC imaging of live biological cells. The proposed method will be useful for monitoring 3-D dynamics of intracellular particles.