Optical image coding with a circular Dammann grating
نویسندگان
چکیده
منابع مشابه
Optical image coding with a circular Dammann grating.
A circular Dammann grating in the front focal plane of a lens is used to generate an annular beam in the back focal plane to code an object by two-dimensional scanning. The coded image of the object is decoded digitally by convolving it with the same annular beam used to code the object. Simple inverse filtering is subsequently used to improve the contrast of the decoded image.
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The term “diffraction” has been defined by Sommerfeld as follows (E. Hecht, 2002): any deviation of light rays from rectilinear paths which cannot be interpreted as reflection or refraction. Diffraction is caused by the confinement of the lateral extent of a wave and is most importantly when that confinement is comparable in size to the wavelength of the radiation being used. The first accurate...
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A polarization-dependent circular Dammann grating (CDG) was generated from an azo-dye-doped liquid crystal (LC) cell. A simple multiexposure photo-alignment process was used to fabricate a binary phase LC CDG zone plane, which was composed of an odd zone with a twisted nematic LC structure and an even zone with a homogenous LC structure. A two-order CDG with equal-intensity rings was produced t...
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A quasi-Dammann grating is proposed to generate array spots with proportional-intensity orders in the far field. To describe the performance of the grating, the uniformities of the array spots are redefined. A two-dimensional even-sampling encode scheme is adopted to design the quasi-Dammann grating. Numerical solutions of the binary-phase quasi-Dammann grating with proportional-intensity order...
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A Dammann grating is used as a spatial filter for a passive coherent beam combination (CBC) of three Yb-doped fiber amplifiers with an all-optical feedback loop. Using this diffractive-optics-based spatial filtering technique, we demonstrate CBC with 20 W output power, and the visibility of the far-field interference pattern is up to 88.7%. Measurements suggest that this approach is robust with...
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ژورنال
عنوان ژورنال: Applied Optics
سال: 2008
ISSN: 0003-6935,1539-4522
DOI: 10.1364/ao.48.000134