JEOS:RP - Journal of the European Optical Society Rapid publications
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Simulated validation and quantitative analysis of the blur of an integral image related to the pickup sampling effects
Full text linkIn an integral imaging (II) system, the pickup sampling effects play an important role in affecting the blur of an integral image. In this paper, the blur property of an integral image due to the pickup sampling artifacts is first analyzed. Then, a figure of merit-the edge blur width (EBW) of a white and black bar object is proposed to characterize the blur of the reconstructed image, and its theoretical model is derived in detail based on a continuous/discrete (C/D) sampling mechanism by considering both the pickup sampling and the reconstruction process. Further, the quantitative relationships of the blur with the pickup sampling parameters (the pixel number of each elemental image, the number of elemental images) are calculated by the EBW model and measured by C/D sampling II simulation experiments, respectively. We find out that the theoretical results have a good agreement with the estimated ones, and the minimum values of the EBW occurred periodically when the pixel number of an elemental image is an integral multiple of the magnification ratio
Temperature effect on the optical emission intensity in laser induced breakdown spectroscopy of super alloys
Full text linkIn this paper, the influence of heating and cooling samples on the optical emission spectra and plasma parameters of laser-induced breakdown spectroscopy for Titanium 64, Inconel 718 super alloys, and Aluminum 6061 alloy is investigated. Samples are uniformly heated up to approximately 200°C and cooled down to -78°C by an external heater and liquid nitrogen, respectively. Variations of plasma parameters like electron temperature and electron density with sample temperature are determined by using Boltzmann plot and Stark broadening methods, respectively. Heating the samples improves LIBS signal strength and broadens the width of the spectrum. On the other hand, cooling alloys causes fluctuations in the LIBS signal and decrease it to some extent, and some of the spectral peaks diminish. In addition, our results show that electron temperature and electron density depend on the sample temperature variations
Study on the temperature field loaded by a shaped laser beam on the top surface of a cylinder head for thermal fatigue test
Full text linkIn thermal fatigue test, the key point is whether the temperature field on the top surface of cylinder head induced by the heat source can well match it in real service. In order to produce the target temperature field in service which is measured by thermocouples, shaped laser beam generated by diffractive optics element (DOE) is chosen as the heat source to irradiate on the top surface of cylinder head. The DOE is designed based on the Gerchberg-Saxton (GS) algorithm and the simulated temperature field is calculated by finite element model (FEM). The results show that the simulated and experimental temperature field can well match the target one which demonstrates that this method is feasible to produce the target temperature field and can be used in thermal fatigue test
Linear and nonlinear tunable optical properties of intersubband transitions in GaN/AlN quantum dots in presence and absence of wetting layer
Full text linkIn this study we have performed a numerical approach to investigate the optical properties of GaN/AlN quantum dots (QDs). We have used nice homemade finite element method (FEM) codes to solve the Schrödinger equation, in presence and absence of wetting layer. The optical properties of both well-known, truncated pyramids–shaped, wurtize (WZ) and zinc blande (ZB) QDs have been investigated. It is demonstrated, there is slight amount of difference between all orders of absorption coefficients and relative refractive index changes (RRIC) for both structures. The effect of relaxation rate studied as well. Overlay it is shown that the optical properties ZB/WZ QDs could be engineered in well-manner
Computation of dioptric and magnification matrices in ophthalmic lenses
Full text linkThe diopter power and magnification matrices characterize the first-order properties of ophthalmic lenses for different gaze directions. Therefore an efficient method to compute them is highly valuable in ophthalmic lens design and optical performance simulations. I present a novel method to numerically compute these matrices in ophthalmic lenses comprising any set of arbitrary surfaces. The method is based on computing one base ray, along the gaze direction, and two rays close to it. These two rays are obtained varying a small parameter that indicates their separation from the base ray. The method was validated comparing the results with a single refractive surface where exact solutions are directly obtained
Polarimetric approach for man-made impurities detection in isotropic materials
No full textIn this paper, a new kind of approach to reveal the presence of well-defined impurities in isotropic materials is proposed and verified against actual measurements over real samples. The rationale lies in the different polarimetric symmetry properties of inhomogeneous and isotropic materials within well-defined impurities from homogeneous ones. The underpinning physical idea is to inspect the Mueller matrix of the material sample, obtained from an ellipsometric measure: its form, in terms of symmetry, can reveal whether or not if in there are well-defined impurities in the sample
Half-linear cavity multiwavelength Brillouin-erbium fiber laser
Full text linkMultiwavelength half-linear cavity Brillouin erbium fiber laser (BEFL) has been demonstrated. The half-linear cavity BEFL is formed by utilizing only two circulators: one circulator acts as input and output ports and the other circulator is used to form a physical mirror. This design exhibits low peak power difference between the adjacent channels, which is about 0.8 dB. At Brillouin pump (BP) power of 5 dBm and erbium doped fiber (EDF) pump power of 90 mW, up to 19 channels over a wide range of 40 nm (1529 nm to 1569 nm) have been obtained. These channels are free from self lasing cavity modes and for the first twelve Stokes lines, the optical signal to noise ratio (OSNR) is approximately higher than 20 dB
Surface characterization by structure function analysis
Full text linkThe structure function is a tool for characterizing technical surfaces which exhibits a number of advantages over Fourier-based analysis methods. So it is optimally suited for analyzing the height distributions of surfaces measured by full-field non-contacting methods. After the definition of line- and area-structure function and offering effective procedures for their calculation this tutorial paper presents examples using simulated and measured data of machined surfaces as well as optical components. Comparisons with the results of Fourier-based evaluations clearly prove the advantages of structure function analysis
Improving the Generic Camera Calibration technique by an extended model of calibration display
Full text linkGeneric camera calibration is a method to characterize vision sensors by describing a line of sight for every single pixel. This procedure frees the calibration process from the restriction to pinhole-like optics that arises in the common photogrammetric camera models. Generic camera calibration also enables the calibration of high-frequency distortions, which is beneficial for high-precision measurement systems. The calibration process is as follows: To collect sufficient data for calculating a line of sight for each pixel, active grids are used as calibration reference rather than static markers such as corners of chessboard patterns. A common implementation of active grids are sinusoidal fringes presented on a flat TFT display. So far, the displays have always been treated as ideally flat. In this work we propose new and more sophisticated models to account for additional properties of the active grid display: The refraction of light in the glass cover is taken into account as well as a possible deviation of the top surface from absolute flatness. To examine the effectiveness of the new models, an example fringe projection measurement system is characterized with the resulting calibration methods and with the original generic camera calibration. Evaluating measurements using the different calibration methods shows that the extended display model substantially improves the uncertainty of the measurement system
Numerical calculation of temperature sensing in seawater based on microfibre resonator by intensity-variation scheme
Full text linkA seawater temperature sensing and detection method based on microfibre resonator (MR) by intensity-variation scheme is proposed, which has the advantages of high sensitivity and low detection limit. The dependences of sensitivity on probing wavelength, fibre diametre and ring diametre are studied. Results show that probing wavelength influences the sensitivity by the absorption loss predominantly. Larger absorption loss results in lower sensitivity, which is much different with resonant-wavelength-shift scheme. And sensitivity increases with the increasing ring diametre due to the decreasing bending loss and increasing Q-factor. In addition, there may exist an optimal fibre diametre, with which the sensitivity is maximized. By tuning the parameters of system, sensitivity can be tuned from 0.0784NI/ºC to 13.79 NI/ºC (NI is the abbreviation of normalized intensity). Correspondingly, dynamic range changes from 11.77ºC to 0.08ºC. Additionally, the dependences of detection limit on wavelength, fibre diametre, and ring diametre are also investigated, which are opposite to that of sensitivity. For different temperatures, the dependences of sensitivity and detection limit at some typical temperatures are studied, which shows that high sensitivity and low detection limit are related to high temperature, and the optimal fibre diametres for high sensitivity and low detection limit are the same at different temperatures. The lowest detection limit is estimated to be 10^-7ºC level, which is four orders of magnitude smaller than that of the traditional method. Results shown here are beneficial to find the optimal parameters for the temperature sensors, and offer helpful references for assembling micro-photonics device used in seawater sensing and detection