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IR monitoring is a basic tool for quality control and predictive maintenance in the paper industry. There are also other possible interests, e.g. measurements of temperature profiles of high speed production lines. The first possibility to use IR for the above mentioned use appears to be applications of glass heat treatment in on line production. At this time there is a lot of interest to be able to measure temperature profiles from a fast moving surface (e.g. in paper machines) with velocities like 10 - 20 m/s. Normal low speed line scanners typically give scanning speed of 50 Hz which in this case means 20 m/s/50 Hz equals 40 cm resolution. The obtained resolution is not normally high enough. To have more accurate vision from the studied surface IR camera line scanning was proposed to be a solution with line scanning frequencies of 8000 Hz which would provide resolution of 20 m/s/8000 Hz equals 0.25 cm between surface points. It is a well-known fact that all undesired frequencies in paper transfer systems disturb the uniform paper drying process which in some cases is the basic reason for low quality coating or even broken paper line. The possibility to detect these drying problems with IR frequency analysis will give a new way to control the paper drying process. With IR analysis it is possible to get information about temperature distributions along the paper track. Using a well established frequency analysis as a tool, the error estimations are obtained. In most cases an open-roll image from paper track is very desirable because there are no existing wide area measurement systems for this purpose. The careful analysis of this new method is given in the manuscript.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Strong demand exists for a non-contacting paper caliper measurement which can be used as an input to a paper thickness control system. Caliper sensors requiring sheet contact suffer from errors related to dirt or coating build up and from high maintenance costs related to wear. These sensors can also damage the product by picking holes and marking sheets. Details of an on-line measurement device which employs two opposed laser displacement sensors and an inductive displacement sensor are presented. The sheet is held perpendicularly to the sensors with a Coanda air clamp. Dust and temperature control features which enable the sensor to operate reliably in an industrial environment are discussed. Results of production trials of this sensor are presented. Sub-micron profile agreement to lab and contacting caliper measurements has been demonstrated on light sheets. Results are presented of measurements on a wide range of paper grades from coated and uncoated light sheets to coated board.

In this paper, we present schedulers that minimize the total transmit power in a multihop wireless network. The focus is on guaranteeing an end-to-end delay bound for a single variable bit rate flow on a multihop fading channel. We first compute an analytical approximation for the transmit power required to send a variable bit rate source over a finite state fading channel. We then use this approximation to derive schedulers that have low complexity and near optimal performance over multihop networks where the fading processes on the multiple hops are independent. Properties of the optimal delay allocation are also studied; in the special case of a Gaussian network, the optimal delay allocation strategy is completely characterized.

A procedure of inspection of femtosecond laser induced mass transfer processes has been suggested that is based on pump-probe Doppler tomography. In the experiments we used mode-locked Ti:sapphire laser with output power up to 150 mW.. In our experiments focused laser radiation induced on the surface of the target mass transfer processes (melting and convection). The Doppler shifted backscattered radiation was registered by heterodyne scheme based on Michelson interferometer. We have obtained information about depth and distribution of convection flows within melted paraffin bath with high spatial resolution (Dz~15mm). We propose optical heterodyning technique based on OCT for obtaining temporal distribution of backscattered photons from media irradiated by Cr:forsterite femtosecond laser. The temporal resolution is about 60 fs. The technique was used for sheet paper porosity diagnostics.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The paper formation is one of the most important properties of the paper but remains a difficult property to determine. A method for determining this property has been developed. This method based on light transmission image analysis uses the power spectra of the Fourier transform to analyze the floc distribution. The method has been tested for various furnishes and allows a well discrimination between different qualities of formation that does the standard formation number.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Numerous equally-spaced emission lines can be generated by stimulated Raman scattering and subsequent four-wave Raman mixing. The spectral domain extends from the near-infrared to the deep-ultraviolet, and then an ultimately-short optical pulse can be generated by phase locking in the process of four-wave Raman mixing. In fact, an intense 17-fs optical pulse has been generated using this technique. A comb of 1.6-fs optical pulses, i.e., the shortest optical pulses, has also been generated by other researchers. On the other hand, it is possible to generate highly-repetitive pulses using a continuous wave (CW) laser as a pump source and molecular hydrogen as a Raman medium in a high-finesse cavity. Coherent superposition of the two-color beam comprising of the fundamental beam and the Stokes beam provides a sinusoidal wave modulated at 17 THz. It is also possible to generate more than three emission lines simultaneously, which should generate an impulsive wave. It is noted that such Raman emission can be generated in a hollow-core fiber, making the device extremely simple. Such a device may have a potential for use in basic science and technology, e.g., the generation of a three-primary-color laser for display.

Sprays, aerosols as well as other industrially relevant turbid media can be characterized by light scattering techniques. However these techniques often fall into the intermediate scattering regime where the average number of times a photon is scattered is too great for single scattering to be assumed, but too few for the diffusion approximation to be applied. We present the results of theoretical study provided details of scattering of laser radiation in the intermediate single-tomultiple scattering regime. Crossed fiber optic source-detector geometry is considered to separate the intensity of single scattering from higher scattering orders. A quantitative analysis of scattering orders in the intermediate single-tomultiple scattering regime is presented. Agreement between the analytical and Monte Carlo techniques both used for the calculation of double light scattering intensity is demonstrated. Influence of detector numerical aperture on the scattering orders is shown for the intermediate single-to-multiple scattering regime. The method used can be applied to verify analytical results indirectly against experiment via Monte Carlo calculations that include the imperfections of the experiment.

Practical vascular medicine get benefits from noninvasive, atraumatic, and monitoring-enabling nature of the optical methods that ensure analyzing arterial, venular, and microvessel blood flow; controlling chemical composition ofthe blood; and assessing the level of blood saturation with oxygen. Currently the most required methods are photoplethysrnography, laser Doppler flowmetry, and pulse oximetry. This report highlights the history ofthe method development, their physical grounds, technical realization, modern state, application fields, the measurement precision, and further prospects. The methods of studying the peripheral blood flow are grounded on the modern achievements of fundamental physics. The discoveries in physics and technologies (photoeffect, photodetecting, optical mixing, photoernission, lasers, etc.) resulted in development ofphotoplethysmography, laser Doppler flowrnetry, and pulse oximetry. Among the major research directions related to the application ofthese methods are the study oftranscapillary exchange, tomography ofrnicrocirculation system, and visualization ofthe microvessels. Further development ofthe conventional methods, first ofall, in direction of raising the precision ofthe measurement and development ofthe controlling instruments is ofa great importance as well.

Galileo Galilei once said in the 17th century that "anyone who understands geometry can understand everything in this world." But he had never heard of molecules, atoms or even smaller components. These days we would imitate Galileo by saying "anyone who understands the processes inside atoms and molecules understands the world." This nano world has its own unique appeal: something that is invisible to the naked eye, yet has dimensions that the mind still requires images/comparisons to understand, is a source of tremendous fascination. Even if we are a long way from understanding these processes, we now know one thing for certain: these days, decisive technological progress is made in the world of the minuscule. Specific examples of this come from the areas of gene technology, materials research and electronics on a daily basis. As a result, nanotechnologies have become the focal point of research and development - not only in industry but also in politics. For example, in March 2004, the German Federal Government launched the German innovation initiative for nanotechnology under the slogan “Nanotechnology Conquers Markets”. According to a press release by the German Federal Ministry of Education and Research (BMBF), euro 200 million in funding will be made available to four leading-edge innovations over the next four years. However, there is still some debate about how to define the term “nanotechnology”. While some see the essence of nanotechnology as the creation of a large entity from the minutest components by means of partly self-organizing processes, such as car paint consisting of nanoparticles, others simply regard the scale of particles or structures as the area of crucial significance. Scientists set a value of 100 nanometers as the "limit". A BMBF brochure argues: "It [nanotechnology] does not, therefore, represent a basic technology in the classical sense-one with clearly defined parameters. Instead, it describes a new interdisciplinary approach that will help us to make further progress in the fields of biotechnology, electronics, optics and new materials." There seems to be no end to the debate, with definitions continuing to clash and overlap. One thing is for sure, though, and that is the importance of nanotechnologies as a driving force for technological progress.

We report our direct observation of the Barkhausen avalanche in ferromagnetic thin film systems, where a collective spin behavior produces nontrivial fluctuations in magnetization change under an external magnetic field. For this study, we develop and use two direct full-field magnetic imaging techniques: magneto-optical microscope magnetometer (MOMM) and magnetic transmission X-ray microscopy (MTXM). From a direct visualization and a statistical analysis of the fluctuating domain images for Co thin films, we investigate the scaling behavior of the Barkhausen avalanche both on spatial and temporal scales using MOMM. We also investigate the reproducibility of the Barkhausen avalanche process. Interestingly, the partially stochastic nucleation behavior is observed for CoCrPt alloy films by means of MTXM on a nanometer scale comparable to the fundamental length scales such as the Barkhausen volume and the grain size of the polycrystalline films. Via these direct full-field observation techniques, dynamic details of Barkhausen avalanche are revealed.

We investigate the creation of squeezing via operations subject to noise and losses and ask for the optimal use of such devices when supplemented by noiseless passive operations. Both, single and repeated uses of the device are optimized and it is proven that in the latter case the squeezing converges exponentially fast to its asymptotic optimum, which we determine explicitly. For the case of multiple iterations we show that the optimum can be achieved with fixed intermediate passive operations. Finally, we relate the results to the generation of entanglement and derive the maximal two-mode entanglement achievable within the considered scenario.

We describe proof-of principle experiments demonstrating a novel approach for generating pulses of light with controllable photon numbers, propagation direction, timing, and pulse shapes. The approach is based on preparation of an atomic ensemble in a state with a desired number of atomic spin excitations, which is later converted into a photon pulse by exploiting long-lived coherent memory for photon states and electromagnetically induced transparency (EIT). We discuss our progress toward applying these techniques to transmit quantum states between atomic memory nodes connected by a photonic channel.

Chalcogenide glass fibers have been developed at NRL. Rare earth doped chalcogenide glass fibers emit strong IR emission and show potential for mid-IR and long-wave IR rare earth doped fiber lasers. In addition, undoped highly nonlinear chalcogenide glass fiber compositions have been developed with high Raman cross-sections and show potential for mid-IR and long-wave IR Raman fiber lasers.

A quarter of a century ago, the lightwave envelope in an optical fiber was shown to be described by the nonlinear Schrodinger Equation. A localized stationary and stable optical pulse (optical soliton) found as its solution was suggested as a carrier of ultra-high speed data transmission. Now the soliton based ultra-high speed communication is vigorously pursued around the world. Furthermore, the nonlinear Schrodinger equation model is widely used as the simulator of information transmission in fibers in general not limited to solitons. Looking back the historical development of optical soliton research is an interesting case study of how an abstract mathematical concept is put into practical use. This development is a consequence of combined efforts of prominent scientists and engineers around the world. However the most significant factor that has contributed to this success is the appropriateness of the god given physical parameters in fibers. Thus it is a sin not to take advantage of this rear opportunity. History of application of optical solitons for high speed signal transmission in fibers may be divided into five stages, (1) historical background and the discovery of the optical soliton, (2) idea and demonstration of all optical soliton transmission systems, (3) identification of possible problems, (4) demonstration of soliton control and (5) Discovery of Dispersion Managed Optical Solitons. In addition, other application of solitons such as modulational instability, dark solitons, spatial solitons are currently vigorously pursued.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Techniques for absolute interferometric measurement of surface figure are often used for qualification of spherical surfaces specified as (lambda) /20 PV or better. As the radius of curvature increases, these techniques become impractical due to the length of cavity required, and environmental effects. Our approach has been to certify a reference surface with a shorter, i.e., manageable radius of curvature, and then to proceed through a series of measurements with surfaces of increasing radius, while maintaining a manageable cavity length. At each stage, the `reference' data from the previous stage is subtracted from the new measurement in order to better approximate the actual surface. The requirements of spatial registration and image magnification are stringent if one is to use the phase measured data directly. This process can be simplified if one uses a polynomial fit to the surface, e.g., Zernikes. The technique is described for the qualification of a surface with an 8 meter radius of curvature and is examined for sources of error.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The quantitative analysis of human corneal endothelial cell patterns is analyzed with Fourier transform methods. The optical or digital Fourier transform of the pattern of endothelial cell borders is analyzed to yield the average cell area and the coefficient of variation of the average cell area. The more difficult problem of cell shape characterization is still under investigation. The advantage of the Fourier transform analysis is the parallel processing of the optical Fourier transform and the potential development of a hybrid digital-optical device for the rapid analysis of large numbers of endothelial specular photomicrographs

We review the nonlinearjoint transform correlator (JTC) including the kth law nonlinear JTC, andthe binary nonlinear JTC. The implementation of the nonlinear JTC using an optically addressedSLM in the Fourier plane is described. I. Introduction The nonlinear JTC uses nonlinearity in the Fourier plane to nonlinearly transform the jointpower spectrum. It has been shown that compared with the classic JTC 1 1 12, the nonlinearjoint transform correlator provides higher peak intensity, larger peak to sidelobe ratio, narrower correlation width, and better discrimination for similar ta1 10, 13 16 We review the nonlinear JTC1, the kth law nonlinear JTC , and the binary nonlinear JTC'3 ,9. We provide an analytical expression for a threshold function in the Fourier plane that provides the highest correlation peak intensity for the first order correlation term of the binaryJTC. 2 It turns out that this threshold function also eliminates the even order correlation terms atthe output plane. Thus, a higher correlation peak to sidelobe ratio is achieved in the output plane.The implementation of the nonlinear JTC using an optically addressed SLM in the Fourier plane isdescribed.

The purpose of this paper is to present GaAs photodetectors which are suitable for Raman Spectroscopy. After a description of the devices and their technology, a complete analysis of their electrical and optical properties is presented. The results obtained are reviewed briefly in terms of static and dynamic responsivities or gains and noise figures. An example of the application of these devices in a conventionnal Raman detection system and the performances of the photodetector array in image detection are given. Furthermore, the use of the Schottky photodiode associated with an FET in Raman spectroscopic systems is discussed.

Rotation-invariant pattern recognition is shown to have intrinsic limitations determined by the set of patterns to be recognized and by the specific optical setup. Within these limitations, a general procedure is proposed for the generation of bipolar filters that do not require the sensitive alignment procedures involved in holographic filters and are suitable for superposition synthesis to achieve rotation invariance.

Material cutting techniques with a focussed c/w CO 2 laser beam use a gas jet from a nozzle to assist ejection of material from the cut kerf. Traditional techniques use a circular tipped nozzle mounted coaxial with the focussing beam. It is usual for these nozzles to be operated at low pressures (

High frequency excitation is increasingly substituting d.c. discharge excitation of CO 2 lasers mainly because of the capability of higher power density and the superior modulation properties. There exist two different modes of high frequency discharges depending on the processes taking place in the boundary layers. The conditions for the existence of both modes will be determined by means of the stationary current density voltage characteristic. Thermal instabilities in high frequency discharges proof to depend on the excitation frequency. The stability limits will be evaluated by a linear stability analysis of a discharge model including gaseous electronics, gasdynamics and Maxwell equations.

Quantum wells (QWs), which can be made from alternate thin layers of two semiconductor materials, show a large electroabsorption called the quantum-confined Stark effect (QCSE). This made possible the realization of electrically controlled optical modulators, and optically controlled self electro-optic effect devices (SEED), that can operate at high speed and low energy density. We will review the various materials systems that have shown QCSE and some of the different devices that have already been fabricated, the latest among them being an optically controlled spatial light modulator, an optically addressed dynamical memory, and an optical S-R latch.

A real-time method to enhance defects in periodic objects is described. Using four-wave mixing techniques, a hologram is nonlinearly recorded in photorefractive BSO so that read-out results in suppression of the periodic structure and enhancement of defects. Experimental results are presented, illustrating detection of defects of size 10 μm x 100 μm. Limitations on the size of defects that can be detected are discussed.

In his 1917 "On Quantum Theory of Radiation" paper Albert Einstein introduced the concept of amplification of radiation through stimulated emission with coherence. This concept had not been applied in practice until 1952 when Joseph Weber, followed by Townes, Basov and Prokhorov, developed the theory and started working on the construction of masers. The first maser was demonstrated by Townes' team in 1953. Many researchers began thinking about making an "optical maser", but the transition from centimeter to nanometer waves posed a problem. Well funded researchers in the USA and Soviet Union put their efforts into making an "optical maser". In May 16, 1960 an unknown and underfunded researcher, Theodore Harold Maiman, won the race and demonstrated a fully functional ruby laser. The scientific world was astonished by its simplicity and elegance. Maiman's short paper describing the invention appeared immediately in Nature magazine. This invention caused an avalanche of new laser developments followed by the growing number of applications in almost all fields of our lives. Ted Maiman died in 2007 in Vancouver, just 13 days before the 47th anniversary of the invention of the laser. The intention of this paper is to focus on the life of the scientific maverick and great man.

A Gibbs Sampler based topic model for image annotation, which takes into account the interaction between visual geometric context and related topic, is presented. Most of the existing topic models for scene annotation use segmentation-based algorithm. However, topic models using segmentation algorithm alone sometimes can produce erroneous results when used to annotate real-life scene pictures. Therefore, our algorithm makes use of peaks of image surface instead of segmentation regions. Existing approaches use SIFT algorithm and treat the peaks as round blob features. In this paper, the peaks are treated as anisotropic blob features, which models low level visual elements more precisely. In order to better utilize visual features, our model not only takes into consideration visual codeword, but also considers influence of visual properties to topic formation, such as orientation, width, length and color. The basic idea is based on the assumption that different topics will produce distinct visual appearance, and different visual appearance is helpful to distinguish topics. During the learning stage, each topic will be associated with a set of distributions of visual properties, which depicts appearance of the topic. This paper considers more geometric properties, which will reduce topic uncertainty and learn the images better. Tested with Corel5K, SAIAPR-TC12 and Espgame100k Datasets, our method performs moderately better than some state of the arts methods.

Due to its capability of capturing the kinematic properties of a target object, radar micro-Doppler signatures (m-DS) play an important role in radar target classification. This is particularly evident from the remarkable number of research papers published every year on m-DS for various applications. However, most of these works rely on the support vector machine (SVM) for target classification. It is well known that training an SVM is computationally expensive due to its nature of search to locate the supporting vectors. In this paper, the classifier learning problem is addressed by a total error rate (TER) minimization where an analytic solution is available. This largely reduces the search time in the learning phase. The analytically obtained TER solution is globally optimal with respect to the classification total error count rate. Moreover, our empirical results show that TER outperforms SVM in terms of classification accuracy and computational efficiency on a five-category radar classification problem.

Self-focusing is observed in nonlinear materials owing to the interaction between laser and matter when laser beam propagates. Some of numerical simulation strategies such as the beam propagation method (BPM) based on nonlinear Schrodinger equation and ray tracing method based on Fermat’s principle have applied to simulate the self-focusing process. In this paper we present an iteration nonlinear ray tracing method in that the nonlinear material is also cut into massive slices just like the existing approaches, but instead of paraxial approximation and split-step Fourier transform, a large quantity of sampled real rays are traced step by step through the system with changing refractive index and laser intensity by iteration. In this process a smooth treatment is employed to generate a laser density distribution at each slice to decrease the error caused by the under-sampling. The characteristics of this method is that the nonlinear refractive indices of the points on current slice are calculated by iteration so as to solve the problem of unknown parameters in the material caused by the causal relationship between laser intensity and nonlinear refractive index. Compared with the beam propagation method, this algorithm is more suitable for engineering application with lower time complexity, and has the calculation capacity for numerical simulation of self-focusing process in the systems including both of linear and nonlinear optical media. If the sampled rays are traced with their complex amplitudes and light paths or phases, it will be possible to simulate the superposition effects of different beam. At the end of the paper, the advantages and disadvantages of this algorithm are discussed.

This paper presents a fast calculation method for spherical computer-generated hologram by using a spherical harmonic transform. A three-dimensional (3D) object defined in the 3D Cartesian coordinate system is numerically Fourier transformed with fast Fourier transforms (FFTs). Fourier components on the spherical surface of the radius 1/λ are extracted. The wavefronts on the spherical surface can be calculated from the single spherical Fourier components. This paper reveals the analytical diffraction integral between the spherical Fourier components and the wavefront on the spherical surface. This diffraction integral is expressed in the form of convolution integral on the sphere and can be calculated very fast based on the spherical harmonic transform. By the numerical simulation, the validity and the effectiveness of our proposal has been verified.

This paper introduces a new way of two-dimensional wavefront reconstruction based on the Fourier modal method. Expending the target wavefront by using Fourier series, calculating the expansion coefficient based on the differential phase measured from the experiment, and fitting the coefficients at the missing points by averaging adjacent values, the target wavefront could be reconstructed eventually by using inverse Fourier transform on the expansion coefficients. The paper also introduces our numerical simulation study on the precisions of both the wavefront reconstruction under ideal situation and under the situation with simulated noise respectively. Corresponding verification experiment for the two-dimensional wavefront reconstruction based on the Fourier modal method is also done by using a two-grating lateral shearing interferometry system, with the 3D profile of the sample obtained.

In this paper, we propose an airport surface surveillance solution combined with Multilateration (MLAT) and Automatic Dependent Surveillance Broadcast (ADS-B). The moving target to be monitored is regarded as a linear stochastic hybrid system moving freely and each surveillance technology is simplified as a sensor with white Gaussian noise. The dynamic model of target and the observation model of sensor are established in this paper. The measurements of sensors are filtered properly by estimators to get the estimation results for current time. Then, we analysis the characteristics of two fusion solutions proposed, and decide to use the scheme based on sensor estimation fusion for our surveillance solution. In the proposed fusion algorithm, according to the output of estimators, the estimation error is quantified, and the fusion weight of each sensor is calculated. The two estimation results are fused with weights, and the position estimation of target is computed accurately. Finally the proposed solution and algorithm are validated by an illustrative target tracking simulation.

This paper proposes an analysis, especially in time domain, of the electrical noise existent on the power distribution lines. This study is important for the use of powerlines as a channel of information transmissions. This information may refer to analog signals and as well to digital signals. The main problem addressed in this paper consists in the characterization of the background noise and to establish his statistical proprieties. It is very important to know if the noise induced in the transmission channel is a stationary one, or even an ergodic one. The main parameters like the mean value, the mean square value were determined in this paper. The approximation of the probability density function of each statistical parameter was studied. The pulses induced in the transmission channel by the transient phenomena of the power electrical systems were considered deterministic signals and their contributions were not included in this study.

In this paper we propose an analysis of the possibilities of spikes detection which appears on the power lines of electrical distribution. The importance of this problem consists in the possibility of surveillance at distance the regimes of power electrical motors. This regime was studied in an industrial network which supplies the power pumps necessary to assures a city water consumption. We consider the industrial electrical networks as a linear, time invariant and causal system which has a certain response to the electrical spikes, assimilates with Dirac impulses. For that reason the output signal represents the impulse response of the system. The main problem is to detect this signal and to establish the moments of its presence. To detect and extract the useful signal linear methods like fourier transform or Short Time Fourier Analysis are not very relevant. A more efficient method to detect the spikes presence consists in using quadratic detectors in timefrequency domain, like detectors based on Wigner-Ville transform or detectors based on Ambiguity Function. In this paper we tried to present the advantages of these last detectors.

During the reconstruction of a digital hologram, the reconstructed image is usually degraded by speckle noise, which makes it hard to observe the original object pattern. In this paper, a new reconstructed image enhancement method is proposed, which first reduces the speckle noise using an adaptive Gaussian filter, then calculates the high frequencies that belong to the object pattern based on a frequency extrapolation strategy. The proposed frequency extrapolation first calculates the frequency spectrum of the Fourier-filtered image, which is originally reconstructed from the +1 order of the hologram, and then gives the initial parameters for an iterative solution. The analytic iteration is implemented by continuous gradient threshold convergence to estimate the image level and vertical gradient information. The predicted spectrum is acquired through the analytical iteration of the original spectrum and gradient spectrum analysis. Finally, the reconstructed spectrum of the restoration image is acquired from the synthetic correction of the original spectrum using the predicted gradient spectrum. We conducted our experiment very close to the diffraction limit and used low quality equipment to prove the feasibility of our method. Detailed analysis and figure demonstrations are presented in the paper.

The paper presents investigation of physical properties of wide bandgap oxide semiconductor – titanium dioxide for applications in integrated photonics as well as for future applications in gas sensors structures. The investigation presented in the paper was focused on: surface topography of TiO 2 layer measured by AFM method, as well as investigation of Raman shift obtained by Raman spectroscopy. Finally the integrated photonics in the form of planar waveguide is also presented.

An analytical formula model which is used to describe laser beam’s depolarization characteristics is solved based on multiple Rayleigh scattering model. Firstly, by using Stokes vector to characterize intensity and polarization, while at the same time using Mueller matrix and rotation matrix to characterize polarization changing in scattering procedure, a single scattering model is built. Then, a multiple scattering model is built considering the effects of atmospheric absorbing and scattering attenuation. The received light’s Stokes vectors through multiple scattering procedure are separately solved. At last, on the basis of multiple scattering vectors, the depolarization characteristics of laser beam propagation through atmosphere are estimated though calculating ratio of depolarization and polarized angle shifting. The numerical analysis based on analytical conclusion of this paper shows that for a horizontal polarized laser beam, its ratio of depolarization is about 1% and polarized angle shifting is about 0.3。 when propagates through atmosphere and arrives into the receiver on the ground, and both the above characteristics have only a small change compared with the change of cloud’s depth. The findings of these research show that Rayleigh scattering from atmosphere has a weak effect on the laser beam’s polarization status. The multiple scattering model and Stokes vector analytical formulas raised in the paper could also be used to study the depolarization characteristics of ellipse polarized laser beam and partially polarized laser beam propagating through atmosphere. The research findings of this paper will have theoretical guiding significances in the domain of laser communication, laser detection and laser imaging.

The high resolution is what the synthetic aperture technique quests for. In this paper, we propose an approach of coherent synthetic imaging with sparse aperture systems using multi-aperture scanning Fourier ptychography algorithm, which can further improve the resolution of sparse aperture systems. The reported technique first acquires a series of raw images by scanning a sparse aperture system and then the captured images are used to synthesize a larger spectrum in the frequency domain using aperture-scanning Fourier ptychography algorithm. The system’s traveling circumvent its diffraction limit so that a super-resolution image can be obtained. Numerical simulation demonstrates the validity. The technique proposed in this paper may find wide applications in synthetic aperture imaging and astronomy.

Because of go-stop mode not applying to FMCW CSAR (frequency modulated continuous wave circular synthetic aperture radar), received signal include Doppler shifting result from the radar fly in one period, which have a bad effect on the quality of imaging in wide-field FMCW CSAR. However the compensation functions of liner SAR are not suitable for CSAR. To solve the problem, the paper rebuild a received mode and elicit the Doppler shifting. At the same time, based on the model, the paper analysis the layover phenomenon while obtaining two-dimensional (2D) representations of 3D large scenes due to the wide-field FMCW CSAR and simulate the phenomenon. By the simulation, the effect of the layover can be expressed clearly.

In this paper, a method is introduced to test wavefront aberration of parallel optical plate wavefront, which based on Fourier transform. When testing the wavefront aberration of parallel optical plate, there is multiple-surface interference which phase-shifting interferometry cannot handle with. With the help of wavelength-modulation phase-shifting interferometry and Fourier transform, this method can isolate the multiple-surface interference fringes in frequency domain. This paper expound the principle of the method, and analyze the key parameter of the testing method: the suitable cavity/thickness ratio and sampling frame number. A simulation experiment is set up to verify the accuracy of this method, then the comparison test with traditional method shows that the relative deviation between the two methods is ≤5%.

In this paper a new detection algorithm is proposed and developed for detecting space objects from images obtained using a ground-based telescope with the goal to improve space situational awareness. Most current space object detection algorithms rely on developing a likelihood ratio test (LRT) for the observed data based on a binary hypothesis test. These algorithms are based on the assumption that the observed data is Gaussian or Poisson distributed under both the hypothesis that a low signal-to-noise ratio (SNR) space object is present in the data and the hypothesis that an object is absent from the data. The LRT algorithm in this paper was developed based on the assumption that the distribution of the Fourier transform of the observed data will be different when a low SNR object is present in the data compared to when the data only contains background noise and known space objects. When an object is present the probability distribution of the real component of the Fourier transform of the intensity was found to follow a Gaussian distribution with a mean significantly different than in the data that doesn’t contain an object even at low SNR levels. As the separation of these two probability distribution functions increases, it becomes more likely that an object can be detected. In this paper, simulated data are used to demonstrate the effectiveness and to highlight the benefits gained from this algorithm.

This article presents results of research on an optical fiber current sensor with external conversion (OFCS-EC). The sensor setup presented in the scope of this paper was developed from the optical fiber magnetic field sensor. The OFCSEC works on the principle of Faraday effect. Therefore, the active element of the sensor was made of the reliable glass showing high Verdet constant. The sensor was characterized by its sensitivity in a optoelectronic current transformer setup for static magnetic field. Investigations presented in this paper are focused on checking, whether parameters of the OFCS-EC are stable during long term measurements. The results of those investigations have proven excellent stability of the proposed OFCS-EC.

Infrared small-target detection plays an important role in image processing for infrared remote sensing. In this paper, we formulate this problem as salient region detection, which is inspired by the fact that a small target can often attract attention of human eyes in infrared images. We show that the convolution of the image amplitude spectrum with a low pass Gaussian kernel of an appropriate scale is equivalent to an image saliency detector. In this paper, we present a quaternion representation of an image which is composed of its intensity after denoising, the horizontal gradient and the vertical gradient. Therefore, a new method for infrared small target based on hyper complex Fourier transform (HFT) is proposed. The saliency map is obtained by reconstructing the 2D signal using the original phase and the amplitude spectrum, filtered at an appropriate scale. Experimental results demonstrate that the proposed algorithm is able to predict salient regions on which people focus their attention.

The Kepler mission highlighted that precision radial velocity (PRV) follow-up is a real bottleneck in supporting transiting exoplanet surveys. The limited availability of PRV instruments, and the desire to break the “1 m/s” precision barrier, prompted the formation of a NASA-NSF collaboration ‘NN-EXPLORE’ to call for proposals designing a new Extreme Precision Doppler Spectrograph (EPDS). By securing a significant fraction of telescope time on the 3.5m WIYN at Kitt Peak, and aiming for unprecedented long-term precision, the EPDS instrument will provide a unique tool for U.S. astronomers in characterizing exoplanet candidates identified by TESS. One of the two funded instrument concept studies is led by the Massachusetts Institute of Technology, in consortium with Lincoln Laboratories, Harvard-Smithsonian Center for Astrophysics and the Carnegie Observatories. This paper describes the instrument concept WISDOM (WIYN Spectrograph for DOppler Monitoring) prepared by this team. WISDOM is a fiber fed, environmentally controlled, high resolution (R=110k), asymmetric white-pupil echelle spectrograph, covering a wide 380-1300nm wavelength region. Its R4 and R6 echelle gratings provide the main dispersion, symmetrically mounted on either side of a vertically aligned, vacuum-enclosed carbon fiber optical bench. Each grating feeds two cameras and thus the resulting wavelength range per camera is narrow enough that the VPHG cross-dispersers and employed anti-reflection coatings are highly efficient. The instrument operates near room temperature, and so thermal background for the near-infrared arm is mitigated by thermal blocking filters and a short (1.7μm) cutoff HgCdTe detector. To achieve high resolution while maintaining small overall instrument size (100/125mm beam diameter), imposed by the limited available space within the observatory building, we chose to slice the telescope pupil 6 ways before coupling light into fibers. An atmospheric dispersion corrector and fast tip-tilt system assures maximal light gathering within the 1.2″ entrance aperture. The six octagonal fibers corresponding to each slice of the pupil employ ball-lens double scramblers to stabilize the near- and far-fields. Three apiece are coupled into each of two rectangular fibers, to mitigate modal nose and present a rectilinear illumination pattern at the spectrograph's slit plane. Wavelength solutions are derived from ThAr lamps and an extremely wide coverage dual-channel laser frequency comb. Data is reduced on the fly for evaluation by a custom pipeline, while daily archives and extended scope data reduction products are stored on NExScI servers, also managing archives and access privileges for GTO and GO programs. Note: individual papers, submitted along this main paper, describe the details of subsystems such as the optical design (Barnes et al., 9908-247), the fiber link design (Fűresz et al., 9908-281), and the pupil slicer (Egan et al., 9912-183).

Radar target identification using probabilistic vector machines is investigated and tested using real radar data collected in a compact range for commercial aircraft models. Unlike relevance vector machines (RVM) that utilize zero-mean Gaussian prior for every weight for both negative and positive classes and are thus vulnerable to questionable (deceptive) vectors, probabilistic vector machines [2], alternatively, use nonnegative priors for the positive class and vice versa. This paper compares the performance of these machines with other target identification tools, and highlights scenarios where classification via a probabilistic vector machine is more plausible. The problem addressed in this paper is a M-ary target classification problem and is implemented as a set of pairwise comparisons between all competing hypotheses.

The polarized hyperspectral images (PHSI) include polarization, spectral, spatial and radiant features, which provide more information about objects and scenes than traditional intensity or spectrum ones. And polarization can suppress the background and highlight the object, leading to the high potential to improve camouflaged target detection. So polarized hyperspectral imaging technique has aroused extensive concern in the last few years. Nowadays, the detection methods are still not very mature, most of which are rooted in the detection of hyperspectral image. And before using these algorithms, Stokes vector is used to process the original four-dimensional polarized hyperspectral data firstly. However, when the data is large and complex, the amount of calculation and error will increase. In this paper, tensor is applied to reconstruct the original four-dimensional data into new three-dimensional data, then, the constraint energy minimization (CEM) is used to process the new data, which adds the polarization information to construct the polarized spectral filter operator and takes full advantages of spectral and polarized information. This way deals with the original data without extracting the Stokes vector, so as to reduce the computation and error greatly. The experimental results also show that the proposed method in this paper is more suitable for the target detection of the PHSI.

In developing sensitive optical sensors, issues associated with optical crosstalk, dark count, and dark current persist. While designs have been created to mitigate the effects of these optical noises on the performance of the sensors, they are never fully addressed. This is mainly due to the highly probabilistic nature of the interaction of light and matter. This paper theoretically explores possible solutions that could lead to the significant reduction of these optical noises by presenting the problem in both the Markovian and Bayesian quantum feedback schemes and identifying the parameters that can be controlled and/or regulated. This paper then attempts to translate the quantum processes into realizable materials and/or systems suitable for fabrication or integration to existing system.

In this paper, we compare the theoretical performance of two design methods that allow simultaneous phase matching of two arbitrary X(2) processes along with the capability of adjusting their relative strength. The crystal of these 1-D aperiodic gratings is chosen to be the orientation-patterned gallium arsenide (OP-GaAs), which has been recently used in several devices for high power infrared beam generation. These single gratings placed in an optical parametric oscillator (OPO) or an optical parametric generator (OPG) can simultaneously phase match two optical parametric amplification (OPA) processes, OPA-1 and OPA-2, for converting the 2.1-μm pump laser radiation into the long-wave infrared (8-12 μm) in an idler-efficiency enhanced scheme. The first aperiodic grating design method (Method-1) relies on generating an aperiodic grating structure that has domain walls located at the zeros of the summation of two cosine functions each of which has a spatial frequency that equals one of the phase-mismatches of the two processes. In this method some of the domain walls are discarded considering the minimum domain length (Dmin) that is achievable in the production process. The second design method (Method-2) relies on discretizing the crystal length with samples with a length that is much smaller than Dmin and testing each sample’s contribution in such a way that the sign of the nonlinearity maximizes the magnitude sum of the real and imaginary parts of the Fourier Transform of the grating function at the relevant phase-mismatch spatial frequencies. Also, during the procedure, the smallest domain length is imposed to be Dmin. In this paper, we present the results of Method-2 which we find that it produces a similar performance as Method-1 in terms of the maximization of the magnitudes of the Fourier peaks located at the phase-mismatches of the nonlinear processes while adjusting their relative strength. To our knowledge, we are the first to propose such aperiodic OP-GaAs gratings for efficient long-wave infrared beam generation based on simultaneous phase matching.

This paper deals with analysis of guided waves mode conversion phenomenon in fiber reinforced composite materials. Mode conversion phenomenon may take place when propagating elastic guided waves interact with discontinuities in the composite waveguide. The examples of such discontinuities are sudden thickness change or delamination between layers in composite material. In this paper, analysis of mode conversion phenomenon is based on full wave-field signals. In the full wave-field approach signals representing propagation of elastic waves are gathered from dense mesh of points that span over investigated area of composite part. This allow to animate the guided wave propagation. The reported analysis is based on signals resulting from numerical calculations and experimental measurements. In both cases defect in the form of delamination is considered. In the case of numerical research, Spectral Element Method (SEM) is utilized, in which a mesh is composed of 3D elements. Numerical model includes also piezoelectric transducer. Full wave-field experimental measurements are conducted by using piezoelectric transducer for guided wave excitation and Scanning Laser Doppler Vibrometer (SLDV) for sensing.

This work addresses the severe lack of literature in the area of modal analysis for multi-metric sensing. The paper aims at providing a step by step tutorial for performance of modal analysis using Fiber Bragg Grating (FBG) strain sensors and Laser Doppler Vibrometer (LDV) for displacement measurements. The paper discusses in detail the different parameters which affect the accuracy of the experimental results. It highlights the often implied, and un-mentioned problems, that researchers face while performing experiments. The paper tries to bridge the gap between the theoretical idea of the experiment and its actual execution by discussing each aspect including the choice of specimen, boundary conditions, sensors, sensor position, excitation mechanism and its location as well as the post processing of the data. The paper may be viewed as a checklist for performing modal analysis in order to ensure high quality measurements by avoiding the systematic errors to creep in.

Magnetic Resonance Imaging (MRI) offers noninvasive high resolution, high contrast cross-sectional anatomic images through the body. The data of the conventional MRI is collected in spatial frequency (Fourier) domain, also known as k space. Because there is still a great need to improve temporal resolution of MRI, Compressed Sensing (CS) in MR imaging is proposed to exploit the sparsity of MR images showing great potential to reduce the scan time significantly, however, it poses its own unique problems. This paper revisits wavelet-encoded MR imaging which replaces phase encoding in conventional MRI data acquisition with wavelet encoding by applying wavelet-shaped spatially selective radiofrequency (RF) excitation, and keeps the readout direction as frequency encoding. The practicality of wavelet encoded MRI by itself is limited due to the SNR penalties and poor time resolution compared to conventional Fourier-based MRI. To compensate for those disadvantages, this paper first introduces an undersampling scheme named significance map for sparse wavelet-encoded k -space to speed up data acquisition as well as allowing for various adaptive imaging strategies. The proposed adaptive wavelet-encoded undersampling scheme does not require prior knowledge of the subject to be scanned. Multiband (MB) parallel imaging is also incorporated with wavelet-encoded MRI by exciting multiple regions simultaneously for further reduction in scan time desirable for medical applications. The simulation and experimental results are presented showing the feasibility of the proposed approach in further reduction of the redundancy of the wavelet k -space data while maintaining relatively high quality.

Flat panel displays have been used in a wide range of electronic devices. The defects on their surfaces are an important factor affecting the product quality. Automated optical inspection (AOI) method is an important and effective means to perform the surface defection inspection. In this paper, a kind of defect extraction algorithm based on one dimensional (1D) Fourier theory for the surface defect extraction with periodic texture background is introduced. In the algorithm, the scanned surface images are firstly transformed from time domain to frequency domain by 1D Fourier transform. The periodic texture background on the surface is then removed by using filtering methods in the frequency domain. Then, a dual-threshold statistical control method is applied to separate the defects from the surface background. Traditional 1D Fourier transform scheme for detecting ordinary defects is very effective; however, the method is not where the defect direction is close to horizontal in periodic texture background. In order to tackle the problem, a mean threshold method based on faultless image is put forward. It firstly calculates the upper and lower control limits of the every reconstructed line scanned image with faultless and then computes the averages of the upper and lower limits. The averages then act as the constant double thresholds to extract the defects. The experimental results of different defects show that the method developed in the paper is very effective for TFT-LCD panel surface defect inspection even in the circumstance that the defect directions are close to horizontal.