Phase-Based Optical Flow Method with Optimized Parameter Settings for Enhancing Displacement Measurement Adaptability

To enhance the applicability and measurement accuracy of phase-based optical flow method using complex steerable pyramids in structural displacement measurement engineering applications, an improved method of optimizing parameter settings is proposed. The optimized parameters include the best measurement points of the Region of Interest (ROI) and the levels of pyramid filters. Additionally, to address the issue of updating reference frames in practical applications due to the difficulty in estimating the maximum effective measurement value, a mechanism for dynamically updating reference frames is introduced. Experimental results demonstrate that compared to representative image gradient-based displacement measurement methods, the proposed method exhibits higher measurement accuracy in engineering applications. This provides reliable data support for structural damage identification research based on vibration signals and is expected to broaden the engineering application prospects for structural health monitoring.

Laser shaping and optical power limiting of pulsed Laguerre–Gaussian laser beams of high-order radial modes in fullerene C60

We study the strong nonlinear optical dynamics of nanosecond pulsed Laguerre–Gaussian laser beams of high-order radial modes with zero orbital angular momentum propagating in the fullerene C60molecular medium. It is found that the spatiotemporal profile of the incident pulsed Laguerre–Gaussian laser beam is strongly reshaped during its propagation in the C60molecular medium. The centrosymmetric temporal profile of the incident pulse gradually evolves into a noncentrosymmetric meniscus shape, and the on-axis pulse duration is clearly depressed. Furthermore, the field intensity is distinctly attenuated due to the field-intensity-dependent reverse saturable absorption, and clear optical power limiting behavior is observed for different orders of the input pulsed Laguerre–Gaussian laser beams before the takeover of the saturation effect;the lower the order of the Laguerre–Gaussian beam, the lower the energy transmittance.

Measurement of Optical Fiber Geometry Parameters with Bessel Function Fitting Method

Geometry parameters of optical fiber are crucial in evaluating the quality of the optical fiber.Near⁃field light distribution method is recommended in GB15972.20-2008 for the measurement of geometry parameters.To distinguish the boundary between fiber core and cladding,it is necessary to illuminate the fiber.The end face of the core is a bright spot with unclear edge,so the true edge of the core and the cladding cannot be accurately judged.A method is proposed in this paper to measure the geometry parameters of optical fiber by Bessel function fitting.Theoretically,the solution to the electromagnetic vector of mode field satisfies Bessel function,and the boundary between the core and the cladding can be precisely extracted by Bessel function fitting.Edges of the fiber were fitted by elliptical curves,and the geometry parameters of the fibers could be calculated.Results show that the maximum deviations of the diameters and the average differences of the fibers were decreased under normal and abnormal conditions respectively.The proposed method is an efficient way to obtain edge data and can improve the accuracy and stability of geometry parameters of optical fibers.

Comparison of Anterior Segment Optical Coherence Tomography and Ultrasound Biomicroscopy for Iris Parameter Measurements in Patients with Primary Angle Closure Glaucoma

Purpose: To compare the repeatability and consistency of anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) in measuring iris parameters in patients with primary angle closure glaucoma. Methods: Twenty-two patients (38 eyes) with primary angle closure glaucoma,including 5 eyes with acute angle closure glaucoma,10 fellow eyes of acute angle closure glaucoma, and 23 eyes with chronic angle closure glaucoma, were recruited consecutively in our hospital. All subjects underwent anterior scanning by AS-OCT and UBM. Peripheral iris thickness (PIT) and iris curvature (IC) in the anterior segment image obtained by AS-OCT and UBM were measured twice. The reproducibility of these two scans was evaluated by the intraclass correlation coefficient (ICC). A paired t-test was used to compare the difference between the two scans and the 95% limits of agreement (LoA) were calculated. Results:The ICCs of PIT and IC measured by UBM were 0.892 and 0.936 respectively, while for AS-OCT these values were 0.629 and 0.859, respectively. UBM had a higher reproducibility in both PIT and IC measurements as compared with AS-OCT.Differences in PIT measurement between AS-OCT and UBM(P=0.331).were not statistically significant, the 95% LoA (-0.178～0.156) mm was 36.1～41.2% of the mean. The IC was 0.053 mm smaller when measured by UBM than by AS-OCT (P=0.017), with the 95% LoA (-0.100～0.206) mm, or 36.2～74.6% of the mean.Conclusion:UBM had a higher reproducibility in measuring iris parameters than AS-OCT. The consistency between AS- OCT and UBM in measuring iris parameters was low in primary angle closure glaucoma patients. (Eye Science 2013; 28:1-6)

Stokes parameters of optical singularities of random electromagnetic beams

In this paper, the relation between the spectral degree of coherence and degree of polarization of random electromagnetic beams is derived by the Stokes parameters. And the concept of polarization singularity is extended from spatially fully coherent beams to partially coherent electromagnetic beams. Theoretical analysis shows that correlation vortices are linearly polarized singularities. The results are illustrated by numerical examples.

Optical Dispersion Parameters with Different Orientations for SrLaAlO_4 Single Crystals

The different optical dispersion parameters of SrLaAIO4 single crystals have been studied by the transmission andreflection measurements at normal incidence for the three orientations 001, 100 and 101 in the spectral range400 nm^2500 nm.The optical absorption data revealed the existance of allowed indirect and direct transition. Therefractive index has abnormal behaviour in the spectral region 400~900 nm, but has a normal one in the higherwavelength region. The optical dispersion parameters, the single oscillator energy Eo and the dispersion energy Edwere determined and indicated the ionic structure of the material. The high-frequency dielectric constant, the latticedielectric constant and the electronic polarizability were determined by the free carriers and the lattice vibrationmodes. The real dielectric constant (?)1, the dielectric loss tangent (tanδ), the volume (VELF) and the surface energyloss function (SELF) have also been discussed.

Bio-inspired optimization algorithms for optical parameter extraction of dielectric materials: A comparative study

Particle swarm optimization(PSO) and invasive weed optimization(IWO) algorithms are used for extracting the modeling parameters of materials useful for optics and photonics research community. These two bio-inspired algorithms are used here for the first time in this particular field to the best of our knowledge. The algorithms are used for modeling graphene oxide and the performances of the two are compared. Two objective functions are used for different boundary values. Root mean square(RMS) deviation is determined and compared.

Terahertz Time-Domain Spectroscopy method for optical parameter extraction of plastic materials

A method for extracting optical parameters of plastics materials based on terahertz time domain spectroscopy is presented. The transmission-type Terahertz Time-Domain Spectroscopy(THz TDS) system is adopted to detect the refractive index and extinction coefficient on different plastic materials. Then the corresponding spectral information is obtained by Fourier transform of the terahertz time domain waveform of the sampling points, including the corresponding amplitude and phase information of the waveform. The optical parameter extraction model is built. By using the simplex optimization method, the curves of the refractive index and extinction coefficient for the plastic material are obtained. The experimental samples are made of different plastic parallel plate materials. The experimental results show that the optimization of optical parameters can improve their extraction accuracy, and the error of refractive index is ±0.005. Extraction technology with the simplex optimization method of optical parameter based on THz TDS can help to extract the optical parameters of engineering plastics. It is of great significance for the research of terahertz nondestructive testing.

Cross-phase modulation instability in optical fibres with exponential saturable nonlinearity and high-order dispersion

Utilizing the linear-stability analysis, this paper analytically investigates and calculates the condition and gain spectra of cross-phase modulation instability in optical fibres in the ease of exponential saturable nonlinearity and high-order dispersion. The results show that, the modulation instability characteristics here are similar to those of conventional saturable nonlinearity and Kerr nonlinearity. That is to say, when the fourth-order dispersion has the same sign as that of the second-order one, a new gain spectral region called the second one which is far away from the zero point may appear. The existence of the exponential saturable nonlinearity will make the spectral width as well as the peak gain of every spectral region increase with the input powers before decrease. Namely, for every spectral regime, this may lead to a unique value of peak gain and spectral width for two different input powers. In comparison with the case of conventional saturable nonlinearity, however, when the other parameters are the same, the variations of the spectral width and the peak gain with the input powers will be faster in case of exponential saturable nonlinearity.

OPTICAL STORAGE MECHANISM AND HIGH-ORDER DIFFRACTION PROPERTIES OF NITROAZOBENZENE-CONTAINING POLYESTER FILMS

Using Nd:YAG second harmonic pulse (100 ps), the optical storage properties of two novel polyesters, poly [4'-bis (N, N-oxyethylene) imino-4-nitroazobenzene succinyl] and poly [2'-chloro-4'-bis (N, N-oxyethylene) imino-4-nitroazobenzene succinyl] have been studied by multiwave mixing. The high-order diffractions of the orientation gratings induced by anisotropy via the reorientation of nitroazobenzene groups and optical information storage with long-term stability have been realized by multiwave mixing in their films. Up to 3rd order forward diffraction was detected in two wave mixing, while up to 4th order backward diffraction was observed in degenerated four wave mixing. The recording mechanism was explained by the trans-cis-trans isomerization cycles of azobenzene groups. The isomerization of these azobenzene groups probably undergoes with inversion mechanism under the experimental conditions. The information recorded in these films has been kept for more than 6 months.

Response of multi-step compound pre-equilibrium reaction cross sections for the(p,n)reactions to forms of optical model parameters

In furtherance to improving agreement between calculated and experimental nuclear data, the nuclear reaction code GAMME was used to calculate the multistep compound(MSC) nucleus double differential cross sections(DDCs) for proton-induced neutron emission reactions using the Feshbach-Kerman-Koonin(FKK) formalism. The cross sections were obtained for reactor structural materials involving ^(52)Cr(p, n)^(52)Mn,^(56)Fe(p,n)^(56)Co, and ^(60)Ni(p, n)^(60)Cu reactions at 22.2 MeV incident energy using the zero-range reaction mechanism. Effective residual interaction strength was 28 MeV, and different optical potential parameters were used for the entrance and exit channels of the proton-neutron interactions. The calculated DDCs were fitted to experimental data at the same backward angle of 150°, where the MSC processes dominate. The calculated and experimental data agree well in the region of pre-equilibrium(MSC) reaction dominance against a weaker fit at the lower emission energies. We attribute underestimations to contributions from the other reaction channels and disagreement at higher outgoing energies to reactions to collectively excited states. Contrary to the FKK multi-step direct calculations, contributions from the higher stages to the DDCs are significant. Different sets of parameters resulted in varying levels of agreement of calculated and experimental data for the considered nuclei.

Experimental Study of Multi Optical Parameter Imaging Technology under the Fog Condition

A multi optical parametric imaging system is introduced and established in order to improve the contrast of object in the fog. A few targets are observed in the fog weather based on the system level radiation model of multi optical parametric imaging and the calibrated model parameters. The results show that the building’s windows can be distinguished clear in the linear polariza-tion, circular polarization and angle of polarization images because of the strong reflected polarization light of the glass;The vehicles in intersection can hardly be seen in the intensity image, and it is fuzzy in degree of linear polarization and angle of polarization image because of the doped polarization information of trees near in fog;The circular polarization image raises the contrast of the vehicles by 20% because the circle polarization of the trees is less in the fog.

Diagnostics of Optical Characteristics and Parameters of Gas-Discharge Plasma Based on Mercury Diiodide and Helium Mixture

The results of diagnostics of spectral, temporal and energy characteristics of the radiation of gas-discharge plasma in a mixture of mercury diiodide vapor with helium in the spectral range of 350 - 900 nm, and the plasma parameters in the range of reduced electric field E/N = 1 - 100 Td are presented. The plasma is created in the barrier discharge device with a cylindrical aperture. The electrodes are placed 0.2 m in length at a distance of 0.015 m. The amplitude of the pump pulse, the duration and frequency were 20 - 30 kV, 150 ns and 1 - 20 kHz, respectively. Radiation in the visible region of the spectrum of mercury monoiodide exciplex molecule is revealed. Regu larities in the optical characteristics of the plasma, depending on the partial pressures of the components of the mixture, the electron energy distribution function, mean electron energy, specific losses of discharge power on the process of dissociative excitation of mercury monoiodide (state B2Σ+1/2) molecules as well as the rate constant of dissociative excitation of mercury monoiodide molecules in working mixture depending on the given reduced electric field are established.

Effect of technological parameters on optical performance of fiber coupler

To find out the influence of technological parameters on optical performance of fused optical fiber device, the fiber coupler was served as subject investigated by using the fused biconical taper machining as experimental setup. Fused fiber coupler's optical performances such as insertion loss, excess loss, directivity and uniformity were tested with the optical test system that was constituted of tunable laser and optical spectrum analyzer. Especially the relationship between optical performance and drawing speed was investigated. The experimental results show that the optical performance is closely related to process conditions. At fused temperature of 1 200 ℃, there exists a drawing speed of 150 μms, which makes the device's performance optimum. Out of this speed region, the optical performance drops quickly. At drawing speed of 200 μms, the excess loss is relatively small when the fused temperature is above 1 200 ℃. So the technological parameters have close relationship with optical performance of the coupler, and the good performance coupler can't get until the drawing speed and fused temperature match accurately.

Profile Method for Measuring Apparent Optical Parameters (AOP) Ⅱin Class- Waters

The profile method is the principal method first to be chosen to measure the apparent optical parameters of waters. This paper first introduces the profile method briefly, then modifies Ⅱthe applied algorithm in the light of the properties of the class- waters and lastly, analyses the effect of application.

An Optical Disdrometer for Measuring Present Weather Parameters

A new present weather identifier(PWI) based on occlusion and scattering techniques is presented in the study. The present weather parameters are detectable by the meteorological optical range(MOR) approximately up to 50 km and by droplets with diameters ranging from 0.125 mm to 22 mm with velocities up to 16 m s-1. The MOR error is less than 8% for the MOR within 10 km and less than 15% for farther distances. Moreover, the size errors derived from various positions of the light sheet by the particles were checked within ± 0.1 mm ± 5%. The comparison shows that the MOR, in a sudden shower event, is surprisingly consistent with those of the sentry visibility sensors(SVS) with a correlation coefficient up to 98%. For the rain amounts derived from the size and velocity of the droplets, the daily sums by the PWI agree within 10% of those by the Total Rain Weighing Sensor(TRwS205) and the rain gauge. Combined with other sensors such as temperature, humidity, and wind, the PWI can serve as a present weather sensor to distinguish several weather types such as fog, haze, mist, rain, hail, and drizzle.

Effects of preparation parameters on growth and properties of β-Ga_(2)O_(3) film

The Ga_(2)O_(3) films are deposited on the Si and quartz substrates by magnetron sputtering, and annealing. The effects of preparation parameters(such as argon–oxygen flow ratio, sputtering power, sputtering time and annealing temperature)on the growth and properties(e.g., surface morphology, crystal structure, optical and electrical properties of the films) are studied by x-ray diffractometer(XRD), scanning electron microscope(SEM), and ultraviolet-visible spectrophotometer(UV-Vis). The results show that the thickness, crystallization quality and surface roughness of the β-Ga_(2)O_(3) film are influenced by those parameters. All β-Ga_(2)O_(3) films show good optical properties. Moreover, the value of bandgap increases with the enlarge of the percentage of oxygen increasing, and decreases with the increase of sputtering power and annealing temperature, indicating that the bandgap is related to the quality of the film and affected by the number of oxygen vacancy defects. The I–V curves show that the Ohmic behavior between metal and β-Ga_(2)O_(3) films is obtained at 900℃. Those results will be helpful for the further research of β-Ga_(2)O_(3) photoelectric semiconductor.

Optical remote sensing image characteristics of large amplitude convex mode-2 internal solitary waves:an experimental study

A series of experiments are designed to propose a new method to study the characteristics of convex mode-2internal solitary waves(ISWs)in optical remote sensing images using a laboratory-based optical remote sensing simulation platform.The corresponding wave parameters of large-amplitude convex mode-2 ISWs under smooth surfaces are investigated along with the optical remote sensing characteristic parameters.The mode-2 ISWs in the experimentally obtained optical remote sensing image are produced by their overall modulation effect on the water surface,and the extreme points of the gray value of the profile curve of bright-dark stripes appear at the same location as the real optical remote sensing image.The present data extend to a larger range than previous studies,and for the characteristics of large amplitude convex mode-2 ISWs,the experimental results show a second-order dependence of wavelength on amplitude.There is a close relationship between optical remote sensing characteristic parameters and wave parameters of mode-2 ISWs,in which there is a positive linear relationship between the bright-dark spacing and wavelength and a nonlinear relationship with the amplitude,especially when the amplitude is very large,there is a significant increase in bright-dark spacing.

Perfect photon absorption based on the optical parametric process

The perfect photon absorption is studied in a cavity quantum electrodynamics(CQED) system, in which an optical parameter amplifier(OPA) is coupled to the cavity mode. This makes it possible to control the optical phase to realize the perfect photon absorption. It is found that in the presence of one and two injected fields, the perfect photon absorption is present in these two cases and can be controlled by adjusting the parametric phase. Moreover, different from the previous predictions of perfect photon absorption in atomic CQED systems, the perfect photon absorption can be changed significantly by the relative phase. Our work provides a new platform to use the parametric processes to make an available way to control the behaviors of photons and to take advantage of the optical phase to achieve the perfect photon absorption.

Theoretical investigation of light generated by optical parametric down-conversion and its application in the demonstration of the EPR paradox

Parametric down-conversion is a useful method to obtain non-classical state in quantum optics. (1)An analytical solution to the Fokker-Planck equation of non-degenerate optical parametric ampli- fication(NOPA)for generation of squeezed light