Zrenjanin Technical College

Zrenjanin, Serbia

Zrenjanin Technical College

Zrenjanin, Serbia
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Manojlovic L.M.,Zrenjanin Technical College
IEEE Journal of Quantum Electronics | Year: 2011

A novel method for optical coherence tomography (OCT) resolution enhancement is presented. A simple mathematical analysis is given where, as a final result, the high-resolution image of an object axial structure is obtained. The object axial structure has been found to be proportional to the inverse Fourier transform of the ratio of two optical power spectra, i.e., the high-frequency part of the channeled spectrum at the interferometer output and the white-light source spectrum, respectively. An experimental setup, based on a very simple fiber-optic interferometric sensing unit, has been built in order to verify the result of the given mathematical model. Compared to the standard Fourier domain OCT, a sevenfold enhancement of the axial resolution is obtained. By using inexpensive and commercially available equipment, the resolution of about 1.3 μm is obtained. © 2006 IEEE.


Manojlovic L.M.,Zrenjanin Technical College
IEEE Sensors Journal | Year: 2011

A novel common path demodulation technique for low-coherence fiber-optic sensors for vibration measurement based on two serially connected fused silica fiber-optic directional couplers is presented. A 2 × 2 coupler is used in the sensor arm and a 3 × 3 coupler serves as a receiving interferometer, providing at the same time two quadrature signals for the interferometric demodulation. A very stable output signal is obtained after the differentiate-and-cross-multiply procedure with the minimal detectable amplitude of the vibration of about 70 pm/√Hz. © 2010 IEEE.


Manojlovic L.M.,Zrenjanin Technical College
Applied Optics | Year: 2014

A novel high-resolution wide-dynamic range electronically scanned white-light interferometry-based interrogation technique is presented. By using off-the-shelf optical components, this technique is capable of reaching a subnanometer resolution. The technique relies on a simple optical setup in which the wedge and camera axes are mutually inclined for a very small angle in the horizontal plane and two-dimensional fringe pattern analysis. Resolution below 0.3 nm and dynamic range of 106 dB have been achieved with a signal-to-noise ratio lower than 25 dB. © 2014 Optical Society of America.


Manojlovic L.M.,Zrenjanin Technical College
Applied Optics | Year: 2014

A robust white-light interferometric sensing system for fast displacement measurement is presented. In order to increase the speed of the sensing system in comparison with the standard realization based on the postprocessing of the captured interferometric signal, a real-time algorithm based on the modified centroid algorithm has been implemented. The modified centroid algorithm generates the error signal that is proportional to the interferometer optical path difference (OPD) during every scan of the used white-light source coherence zone. In order to keep zero OPD, an amplified version of the error signal has been brought to the input of the piezo bimorph actuator (PBA) that on the other side serves for the fast coherence zone scan. In this way the PBA tracks the position of the object whose displacement is to be measured. Therefore, the voltage signal at the PBA input is proportional to the measured displacement. The realized sensing system has an overall bandwidth of almost 10 Hz, where the sensor full scale range of 200 μm has been measured with a resolution of 3 nm. © 2014 Optical Society of America.


Manojlovic L.M.,Zrenjanin Technical College
Applied Optics | Year: 2011

A quantitative theoretical analysis of the quadrant photodetector (QPD) sensitivity in position measurement is presented. The Gaussian light spot irradiance distribution on the QPD surface was assumed to meet most of the real-life applications of this sensor. As the result of the mathematical treatment of the problem, we obtained, in a closed form, the sensitivity function versus the ratio of the light spot 1/e radius and the QPD radius. The obtained result is valid for the full range of the ratios. To check the influence of the finite light spot radius on the interaxis cross talk and linearity, we also performed a mathematical analysis to quantitatively measure these types of errors. An optimal range of the ratio of light spot radius and QPD radius has been found to simultaneously achieve low interaxis cross talk and high linearity of the sensor. © 2011 Optical Society of America.


Manojlovic L.M.,Zrenjanin Technical College
Optical Fiber Technology | Year: 2016

A crosstalk analysis of the in-line quasi-distributed low-coherence low-finesse Fabry-Pérot fiber-optic interferometric sensors is presented in this paper. The appropriate selection of the sensor cavity lengths eliminates the presence of the second-order intermodulations. Therefore, the intermodulations that can significantly influence the sensors crosstalk are the third-order intermodulations. For a typical sensor configuration by choosing the in-fiber mirror reflection coefficient lower than 0.5%, the minimum achievable signal-to-intermodulation ratio is higher than 26 dB for a maximal possible number of sensor placed along the fiber that satisfies broad range of requirements for most of the quasi-distributed measurements of typical parameters such as strain and temperature. © 2016 Elsevier Inc. All rights reserved.


Manojlovic L.M.,Zrenjanin Technical College
Applied Optics | Year: 2015

A novel photometry-based estimation of the total number of stars in the Universe is presented. The estimation method is based on the energy conservation law and actual measurements of the extragalactic background light levels. By assuming that every radiated photon is kept within the Universe volume, i.e., by approximating the Universe as an integrating cavity without losses, the total number of stars in the Universe of about 6 × 1022 has been obtained. © 2015 Optical Society of America.


Manojlovic L.M.,Zrenjanin Technical College
Optik | Year: 2016

A theoretical analysis of the resolution limit of the light spot position measurement with the quadrant photodetectors has been presented in this paper. In order to reduce the interquadrant crosstalk each quadrant is separated from the adjacent quadrants with a narrow light-insensitive gap. However, it was found that these gaps limit the measurement resolution. Nevertheless, the estimated resolution is still just an order of magnitude lower than the resolution in position measurement with the standard quantum limited interferometer based on the He-Ne laser. © 2016 Elsevier GmbH.


Manojlovic L.M.,Zrenjanin Technical College | Marinic A.S.,Serbian Academy of Science and Arts
Measurement Science and Technology | Year: 2011

A novel method for deriving the integrating cavity transfer function, where the average electromagnetic radiation intensity decay time in the cavity has been found as the final result, is presented, and where a uniform photon distribution inside the cavity was assumed. Instead of the beam reflection analysis, the method is based on employing the energy conservation law inside the integrating cavity. The obtained result for the decay time is slightly different from other results obtained elsewhere but still in relatively good agreement with them. In order to verify the obtained result, we performed a similar analysis based on the photon number conservation law. This analysis gives the same result for the decay time as the first one. Finally, in order to confirm the obtained result, we statistically analyzed the average lifetime of a photon inside the cavity after the radiation source switch-off, i.e. the average time between the radiation source switch-off and its absorption by the cavity inner walls. The result for the decay time obtained in this way is identical to the results obtained using the above-presented methods. At the end, the transfer function of the integrating cavity filled with a weak absorbing material is derived. Based on the obtained result, a novel method for the absorption coefficient measurement is proposed. © 2011 IOP Publishing Ltd.


Bajic J.S.,University of Novi Sad | Stupar D.Z.,University of Novi Sad | Manojlovic L.M.,Zrenjanin Technical College | Slankamenac M.P.,University of Novi Sad | Zivanov M.B.,University of Novi Sad
Sensors and Actuators, A: Physical | Year: 2012

The paper presents a simple, low-cost and high-sensitivity fiber-optic tilt sensor. The sensor consists of two optical fibers and a container filled with transparent liquid to the half of the total volume of the container. The sensor principle is based on the change in angle of the liquid surface with respect to the fibers with the tilt angle. The achieved sensor sensitivity and resolution are 1 V/°and 0.02°, respectively. © 2012 Elsevier B.V.

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