Sampling moiré is introduced as white light-color moiré. The experimental results show that the red and blue color images of the sampling moiré fringes have phase difference π relative to each other. The principle of color sampling moiré is derived assuming that the Bayer pattern-CCD array can be considered a combination of a bicolor red–blue grating and a green smooth plate. The moiré fringes created by the superimposition of the red–blue and a binary grating are simulated under the circumstances, where the binary grating is illuminated by red, blue, and white sources. The results of the simulation confirm that the red and blue sources moiré fringes have a phase shift relative to each other and that the gray-scale moiré fringes of the white source have smaller contrast than those of color sources. Simulation of the color sampling moiré shows results similar to the experiments except that the phase difference of π differs close to the image edges in the latter, due to the color aberration of the lens. It is indicated that sampling moiré can be used as color moiré without a color source or a color grating, with low cost setup.
In this work, a multilayer nanocomposite based fiber optic SPR sensor is considered and especially designed for CO2
gas detection. This proposed fiber sensor consists of fiber core, gold-silver alloy and the absorber layers. The
investigation is based on the evaluation of the transmitted-power derived under the transfer matrix method and the
multiple-reflection in the sensing area. In terms of sensitivity, the sensor performance is studied theoretically under
various conditions related to the metal layer and its gold and silver nanoparticles to form a single alloy film. Effect of
additional parameters such as the ratio of the alloy composition and the thickness of the alloy film on the performance of
the SPR sensor is studied, as well. Finally, a four-layer structure is introduced to detect carbon dioxide gas. It contains
core fiber, gold-silver alloy layer, an absorbent layer of carbon dioxide gas (KOH) and measurement environment.
Lower price and size are the main advantages of using such a sensor in compare with commercial (NDIR) gas sensor.
Theoretical results show by increasing the metal layer thickness the sensitivity of sensor is increased, and by increasing
the ratio of the gold in alloy the sensitivity is decreased.
In this work, a simple method is introduced for estimating the number of the nanoparticles in an active sample based on
random laser theory. The sample includes nanoparticles which are distributed randomly. Because of multiple scattering
random laser action can occurs when the sample is pumped optically. Here, one-dimensional random laser system is
considered and the sample changes are added to the system by changing the number or size of layer. The spectral
emission of the sample is calculated by transfer matrix method. The statistical behavior of output emission spectrum is
achieved by calculating the averaged spectrum from many random realizations. The results of simulation shows that
changes in the number of nanoparticles (or in the averaged size) can be estimated from the statistical random laser output
emission and averaged lasing wavelength. This proposed method is fast, non-contact, and needs to a simple setup. Also,
it can be used for biological and chemical medium for analysis of different parameters which effect on the spectral
random emission.
Aberration correction was one of the most important and challenging parts of optical trapping systems. Many works try to overcome aberration which is due to trapping setup itself or refractive index mismatch of glass slab and nanoparticles solutions. In this article, we investigate a new method for aberration correction based on a nonlinear refractive index of materials. With the emitting laser to the trapped particle, the refractive index of the trapping site increases and as a result, its aberration reduce. In accordance, this method offers a simple and low-cost way for increasing trapping stiffness.
Nanoparticles with second-order optical nonlinearities have been widely studied because of their applications in clinical and industrial applications. The nonlinear absorption coefficient is an important parameter which should be determined in order to fully grasp the implications of these materials. In this work Moire deflectometry method is used to measure the nonlinear absorption coefficient of nanoparticles. In the proposed method the divergence of beam is measured instead of measuring the intensity of divergent ray. Two beams are used; one is a comparatively high intensity laser beam which is used as the interacting beam and the other is used as probe, wide beam with low intensity that is radiated to the first beam vertically. By analyzing the probe beam using Moiré deflectometry, the nonlinear absorption coefficient is measured.
In this work it is shown that the refractive index and temperature distribution of atmospheric Dielectric Barrier Discharge (DBD) plasmas are measured by Moiré deflectometry. Fringe analysis is used to calculate Moiré deflection and to evaluate refractive index in different points of plasma. By Sa-Ha equation and considering the first ionization, the dependence of refractive index and temperature, electrons, ions and molecules number densities of DBD plasma is obtained. By knowing this relation between plasma parameters, the spatial distributions of the plasma refractive index and temperature are evaluated. The advantages of this method are: simplicity, non-contact, non-destructive measurement, low cost, high accuracy and direct measurement of refractive index gradient.
Nanoparticles exhibit many unique and interesting optical properties which make them very useful in biomedical applications. In order to employ NPs for disease treatment, comprehensive knowledge of their important properties is crucial. One of these parameters is absorption coefficient. In this work, absorption coefficient of a nanofluid (Au nanoparticles in water) is measured by using Moiré deflectometry technique. Two laser beams are used: a comparatively high intensity laser beam as interacting beam and a low intensity as a probe beam. This method is fast, easy and nonscanning, also insensitive to vibrations.
An optical method for in- plane rotation angle measurement based on hardware sampling moiré is presented. This method is investigated and introduced as a new technique for in- plane rotation angle measurement. Equations are derived and theoretical calculation and experiment are done base on these. Experimental results confirms that measurement accuracy in order of 0.1 degree conform to expectance results. Advantages of this technique are simplicity, high sensitivity and measurement and direction determination of rotation angle in the same time.
Determination of refractive index is an important characteristic of material which is crucial parameter for physicists and engineers. Moiré deflectometry technique is convenient, easy-aligning, nondestructive, non-contact and fairly accurate method for refractive index measurement of gas, liquid, solid. In this paper we investigate the theory of the technique and simulate some relations then finally measure refractive index of a glassy lamella, n=1.536.
The reconstruction of three dimensional objects is an increasingly important topic in many fields. Many methods are
used to achieve this but among them optical full field methods are used widely due to their advantages of non contact
measurement operation, fast measurement speed and automatic processing. In the measurement process, a video
projector projects a lines pattern on a test surface, and a digital camera capture the image of lines pattern on it. The
height distribution of surface deforms the projected line pattern and modulates them in phase domain. By applying
Fourier transform analysis and phase unwrapping algorithms, the 3D profile of test surface can be reconstructed. The
purposes of this paper are digital reconstruction of complex object like human face and comparison of execution time
among three different phase unwrapping algorithms applied to FTP method. In addition the accuracy of measurement
based on this method is compared with rightful measurement.
When two similar gratings are superimposed, the transmission function of them varies with the displacement of one
grating with respect to the other. The transmitted light intensity versus displacement is proportional to the autocorrelation
of the transmission function of the gratings. In this paper, it is shown by measuring the latter function for gratings of
pitches in order of a fraction of millimeter, submicron displacements can be measured. More precision is easily available
by increasing the area of gratings and the detector gain. The presented technique is not expensive, complicated and
sensitive to environmental vibrations.
The experimental investigation of thermodynamic properties such heat and mass transfer of plasmas has many
applications in different industries. Laboratory atmospheric arc plasma is studied in this work. The refractive index of
the air around the plasma is changed because of convection phenomena. When the convection creates the air flowing
around the plasma, the density and consequently, the refractive index of air are distributed symmetrically.
Moiré deflectometry is a technique of wave front analysis which in both Talbot effect and moiré technique is applied
for measuring phase objects. Deflection of light beam passing through the inhomogeneous medium is utilized to obtain
the refractive index distribution. In experimental set-up, an expanded collimated He-Ne laser propagate through the arc
plasma and the around air. The temperature distribution is obtained by use of thermo-optic coefficient of air. To
calculate the thermo- optic coefficient and the refractive index of air for a given wavelength of light and given
atmospheric conditions (air temperature, pressure, and humidity), the Edlén equation is used. The convective heat
transfer coefficient is obtained by calculating the temperature gradient on the plasma border. This method is not
expensive, complicated and sensitive to environmental vibrations.
We report the fabrication of nanoparticle gold thin films by DC magnetron sputtering and characterization of their
nonlinear optical properties. Nonlinear optical response was investigated by moiré deflectometery technique using
5mW He- Ne laser (632.8 nm) illumination. All prepared films were characterized by XRD and UV-VIS-NIR
spectrophotometry. The measured thermal Nonlinear refractive index (n2=-2.2×10-5 cm2 W-1) makes it promising for
applications in all-optical switching devices and optical data storage systems.
In this paper, it is shown theoretically and verified experimentally that the modulation transfer function (MTF) and phase
transfer function (PTF) of a printer can be evaluated simultaneously by measuring convolution of transmission function
of a couple of printed Ronchi gratings. In practice, two similar printed Ronchi gratings are superimposed inversely to
create the Moiré fringes. By measuring the transmittance of moiré fringes, the convolution function can be obtained.
Using the latter function, the PTF can be evaluated in addition to MTF, but the measurement of the autocorrelation
function of the gratings results in the MTF only. In fact, as superiority this technique does not require a high sensitive
detector and a very narrow slit.
In this paper it is shown that temperature, refractive index and density and also convective heat transfer coefficient
around a vertical axisymmetric cylindrical wire can be measured by the Michelson Interferometer. In experimental setup,
a vertical wire has been put in one of the arms of the Michelson Interferometer. By applying voltage to the wire,
temperature gradient is created around the wire. These phenomena curved the linear Michelson fringes. By measuring
the fringes shift and applying the Abel transform, the distribution of refractive index can be evaluated. This distribution
gives the density distribution. Minimum value for refractive index and density is found on the surface of the wire. For the
far distance from the wire, density and refractive index approaches to the room values. Air density was evaluated
experimentally, which is compatible with its reported value at definite weather conditions. Considering high reflectance
of the wire, its thermal radiation is low and heat mostly transfers by convection. Convective heat transfer coefficient is
measured experimentally which agrees with last results.
The turbulence of the atmosphere puts an upper limit on the quality of the image of a ground object obtained by long-exposure photography from low or high altitudes in the atmosphere or in the space. By using good optics and high resolution film or CCD and a stable platform, this limit could be approached but not exceeded. A useful quantity for indicating the magnitude of this limit is the integral of the modulation transfer function (MTF) associated with the turbulence. In this work, we introduce a new method for measuring the MTF of the atmosphere in the surface layer, based on moire technique. In this technique, from a low frequency Ronchi grating, installed at a certain distance from a digital camera equipped with a tele lens, successive images are recorded and then transferred to a PC. By rotating each image by θ/2 and -θ/2, say ±3°, and superimposing them, a large number moire patterns are produced. The average transmittance function of the superimposed image gratings is measured in a moire fringe interval. The latter function is measured by scanning the moire pattern by a slit parallel to moire fringes. It is shown theoretically that from the Fourier transform of the latter function the MTF of the atmosphere can be deduced, if the MTFs of the imaging system and the grating are given or their effects are negligible. The atmospheric MTFs have been measured at different turbulence conditions. Also, we have studied the behavior of the atmospheric MTF respect to exposure time.
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