Browsing by Author "Варищук, В. І."

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    Дослідження оптичних волокон методом цифрової голографічної інтерферометрії
    (Видавництво Львівської політехніки, 2014) Петровська, Г. А.; Варищук, В. І.; Фітьо, В. М.
    Запропоновано метод цифрової голографічної інтерферометрії для дослідження фазових мікрооб’єктів. Створено макет голографічного інтерференційного мікроскопа з цифровою реєстрацією голограм. Розроблено методику дослідження оптичних волокон, подано експериментальні результати визначення розподілу показника заломлення у поперечному перерізі оптичного волокна. The purpose of this paper is investigation the possibilities of applying methods of digital holographic interferometry to study the internal structure of the optical fiber, including the distribution of the refractive index in the cross -section. Modern development of micro-and nanotechnology requires the development of new approaches and methods for the diagnosis properties of mediums and objects, and research processes and structural changes that are taking place under the influence of external factors. In particular, diagnosis and metrology are important in the field of fiber technique since it is known that increasing the density of information that is transmitted through the optical fiber requires their micro- and nanostructuring. Optical microscopy is the classical method studying of the micro- and nanoscale mediums, phenomena and processes. However, main disadvantages are limitation of the spatial resolution due to diffraction effects, and the inability (or technical complexity) 3D imaging of phase microscopic objects. The coherent-optical methods including methods of holographic interferometry received the high actuality with the appearance of the coherent radiation sources which are the most promising tools for experimental investigation of the materials characteristics and properties of the phase and diffuse macro- and micro objects. At the same time, application of the holographic interferometry to study microscopic objects is only possible at combining it with classical microscopy. This combination allows produce the qualitative and quantitative diagnosis with a high sensitivity and precision as well as achieving image magnification. Indicated disadvantages will be disappeared when holographic interferometry and classical microscopy will be combined. This combination allows produce the qualitative and quantitative diagnosis with a high sensitivity and precision as well as achieving image magnification. In this work method of digital holographic interferometry to research the phase microobject are presented. Model of holographic interference microscope with a digital recording of holograms and receiving interferogram by subtracting two video signals has been developed. Technique investigation the distribution of refractive index in optical fibers has been developed. Experimental results of the distribution of the refractive index in the optical fiber are presented. It is shown that the sensitivity of the developed digital interference microscope depends on the characteristics of CCD and microscope zoom.
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    Контроль малих деформацій багатомодового полімерного волокна шляхом аналізу спекл-картин на його виході
    (Видавництво Львівської політехніки, 2014) Варищук, В. І.; Бобицький, Я. В.
    Запропоновано та розглянуто метод контролю малих деформації полімерного оптичного волокна вимірюванням коефіцієнта кореляції спекл-картин. Досліджено схему та принцип роботи волоконно-оптичного давача деформації на основі багатомодового полімерного оптичного волокна. Проаналізовано залежності коефіцієнта кореляції спекл-картин від параметрів оптичного волокна та довжини хвилі випромінювання. Запропонований метод може бути ефективно використаний для контролю механічних напружень будівель та інженерних споруд. In this paper an optical scheme and the operation principle of strain monitoring based on the interference between guided modes in multimode polymer optical fiber is investigated. The possibility of measuring of the relative strain by processing of speckle patterns at the exit face of multimode fiber is studied theoretically and experimentally. The algorithm of correlation processing of speckle pattern is developed too. The recent progress of polymer technology allowed the application of plastic optical fiber in sensor design. Polymer optical fibers (POFs) have many advantages for sensing applications, including high elastic strain limits, high fracture toughness, high flexibility in bending, high sensitivity to strain. Polymers also have excellent compatibility with organic materials, giving them great potential for structural health monitoring. The most schemes of POF sensors were constructed using single-mode fiber, because it has high technical parameters. But, optical schemes of single-mode POF sensors are very complex. Multimode POF sensor can be constructed using only one fiber and digital camera. This simple scheme is based on the phenomenon of interference between modes in multimode optical fiber. The features of the low cost sensing technique for small strain measuring with using multimode POF were considered. This investigation shows that relative strain of conventional polymer optical fiber can be measured with high accuracy by correlation processing of speckle patterns formed at the exit face of fiber. The correlation method considered in the paper allows one to measure an axial elongation of the fiber within 0 to 50·10-7 m for typical multimode polymer optical fiber with the core diameter 980 μm. The interval between measurements is a few seconds, are needed to stabilize of speckle pattern. The measuring range of such strain sensor depends on properties of fiber used as sensitive element of sensor and using wavelength. The sensitive of sensor is determined by the changes of refractive index and temperature variations due to fiber deformation. Device sensitivity may easily be modified to coincide with required measurement sensitivity through careful choice of the active sensing fiber parameters. The sensing technique presented in this paper is simple, effective and inexpensive solutions to the problem of small strain measurements.