I was speaking to my sister a few days ago and she would not believe the number of challenges that I have been through in the past few years. My recent ordeal (last month) involved my kids and I having dinner at my girlfriend’s house. She was cooking steaks on her grill and there were leaves in the grill that ignited. The grill caught fire on the porch and blew up, and it burned her house down. Everyone was safe (which is most important), but it will take four or five months to rebuild her house. She is now putting up with me and my kids in my condo and is being a real trooper about it. My sister tells me that, if God is trying to teach me something, he must think I am a slow learner.

Welding distortion is an important engineering topic for simulation and modeling, and there is a need for experimental verification of such models by experimental studies. High-speed pulsed digital holography is proposed as a measurement technique for out-of-plane welding distortion. To demonstrate the capability of this technique, measurements from a laser spot weld are presented. A complete two-dimensional deformation map with submicrometer accuracy was acquired at a rate of 1000 measurements per second. From this map, particular points of interest can be extracted for analysis of the temporal development of the final distortion geometry.

A fast coding unit (CU) decision method is proposed for high efficiency video coding (HEVC) by determining early the CU sizes based on coding tree pruning. One of the most effective, a newly introduced concept in HEVC, is variable CU size. In determining the best CU size, the reference encoder of the HEVC tests every possible CU size in order to estimate the coding performance of each CU defined by the CU size. This causes major computational complexity within the encoding process, which should be overcome for the implementation of a fast encoder. A simple tree-pruning algorithm is proposed that exploits the observation where the subtree computations can be skipped if the coding mode of the current node is sufficient (e.g., SKIP mode). The experimental results show that the proposed method was able to achieve a 40% reduction in encoding time compared to the HEVC test model 3.0 encoder with only a negligible loss in coding performance. The proposed method was adopted in HEVC test model 4.0 encoder at JCT-VC 6th meeting.

Two-wavelength holographic recording in thick phenanthrenequinone-doped poly(methyl methacrylate) photopolymer is demonstrated. By using 325 nm laser as a gating illumination during the holographic recording with 647 nm laser, a volume hologram with diffraction efficiency of ∼ 4% can be recorded in a 2 mm thick sample. In addition, the Bragg selectivity curve with clear sinc nulls is demonstrated. These results support further applications as recording media for volume holographic device with extended spectral response and selective recording property.

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Laser communication terminals with data rates far above 1 Gbps have been in operation in orbit since January 2008, and the links established between two low Earth orbit (LEO) satellites have demonstrated error-free communication. Bit error rates better than 10−11 have been achieved without data encoding. Signal acquisition can be reproducibly achieved within a few seconds. After adaptation to larger link separation distances these laser communication terminals will be used in the low earth orbit-geosynchronous satellite (LEO-GEO) link of European data relay satellite (EDRS), the GEO European data relay system. LEO-to-ground and ground-to-LEO links have examined the impact of the atmosphere on such optical links. In the future, high data rate GEO-to-ground links will require ground stations equipped with adaptive optics, which are currently under development.

The author describes the key design feature of a newly developed compact free-space optical terminal, which can achieve robust direct single-mode-fiber-coupling with advanced bidirectional beacon tracking system and excellent operational performance under various adverse weather conditions, such as strong atmospheric turbulences and rain/snow falls. The author found that there is a good correlation between the scintillation index of beacon/signal receiving intensities and the signal fading depth. Therefore, the signal link quality can be predicted from the beacon scintillation index using the classical Rytov theory. According to the outdoor experimental results, it can be concluded that the scintillation index of the beacon beam should be less than 0.1 for stable and reliable communication links.

We developed a new technology that does the acquisition, stable tracking, and fast handover for free space optical links to high-speed trains. Our prototype provided a stable communication link between a train and the ground at a data rate near 1  Gb/s with a handover time on the order of 100 ms.

Using an 850-nanometer-wavelength free-space optical (FSO)communications system of our own design, we acquired field data for the transmitted and received signals in fog at Point Loma, CA for a range of optical depths within the multiple-scattering regime. Statistical estimators for the atmospheric channel transfer function and the related coherency function were computed directly from the experimental data. We interpret the resulting channel transfer function estimates in terms of the physics of the atmospheric propagation channel and fog aerosol particle distributions. We investigate the behavior of the estimators using both real field-test data and simulated propagation data. We compare the field-data channel transfer function estimates against the outputs from a computationally-intensive radiative-transfer theory model-based approach, which we also developed previously for the FSO multiple-scattering atmospheric channel. Our results show that the data-driven channel transfer function estimates are in close agreement with the radiative transfer modeling, and provide comparable receiver signal detection performance improvements while being significantly less time and computationally-intensive.

Attenuation of electromagnetic waves at 860 nm and 58 GHz due to scattering in rain is measured on the terrestrial paths simultaneously with rain intensity. The relationship between rain intensity and rain attenuation of light is analyzed using the Marshal-Palmer drop size distribution model and the Mie scattering theory. The pertinent power law model is derived from drop size distribution parameters. An empirical composite power law model is proposed and fitted to the dataset extracted from rain attenuation events recorded during a seven-year experiment in Prague. Observed average rain attenuation of light at intensities larger than about 5 mm/h is lower than attenuation predicted by standard models. Rain attenuation measured at 58 GHz is larger than attenuation at 860 nm for rain intensities in the range from 0.1 to 100 mm/h.

Recent measurement campaigns in Prague, Czech Republic have recorded the specific attenuation caused by fog in terrestrial free-space optical (FSO) links along with visibility, liquid water content (LWC), and integrated particle surface area for operational wavelengths of 1550 and 830 nm. Data recorded during 5 months of measurements has been analyzed in an attempt to validate and improve the empirical models for LWC and visibility-based attenuation and the probability density function (PDF) estimation of the received signal strength (RSS). The results strongly suggest that further attempts in refinement of the empirical modeling for visibility-based attenuation or LWC-based attenuation shall move towards the establishment of a global data bank of fog attenuation measurements in different climatic regions. This data bank can then help develop generic models which could lead to better system design of future terrestrial FSO links. The PDF estimation of RSS puts forth the Kumaraswamy distribution as the best fit for settled continental fog conditions.

The retardance of an achromatic retarder may vary in the working frequency range and therefore deviate from its nominal value. In a rotatable retarder and fixed polarizer (RRFP) Stokes polarimeter, the retardance deviation of the retarder will result in significant measurement errors of the Stokes vector. The relationship between the retardance error and the measurement errors is theoretically derived in a RRFP Stokes polarimeter. Theoretical results show that the resultant measurement errors of the Stokes vector are determined by the retardance of the retarder, the retardance error and the Stokes vector under test, but are independent of the angular orientations of the retarder and the intensity measurements. Such measurement errors can not be reduced by choosing a set of optimum angular orientations or increasing the measurement number. To suppress such measurement errors in a complete RRFP Stokes polarimeter, the retarder with retardance from 110-deg to 135-deg is recommended. Simulation results in two measurement scenarios confirm the validity of the theoretical findings.

An efficient and practical method for the design of an illumination system with a single plano-convex freeform lens for color filter liquid crystal on silicon (CF-LCoS) pico projectors is proposed. Based on Snell's law and the energy conservation law, the initial illumination system is derived and the freeform lens is numerically calculated from a first-order partial differential equation, which could be considered a good optimization start for further optimization. For an actual extended LED chip, a local optimization algorithm could efficiently achieve the design goals based on the specifically designed initial system. The design example shows that the illumination system employed a CF-LCOS panel with a diagonal of 0.38-in and an aspect ratio of 16∶9 meets the needs of the optical engine for a pico projector, which has a transmission efficiency of 50% and an ANSI nine-point uniformity over 95%, with the whole optical engine volume 28.4×18.5×8  mm³. Moreover, analysis indicates that the design method could obtain outstanding performance with compactness and low cost.

Glass with a low transition temperature (Tg) has the advantage of extending the service life of molding dies. However, low Tg glasses normally demonstrate poor chemical durability and scratch resistance. The molding of low Tg chalcogenide glasses is very challenging due to their fragile and unstable characteristics. This research tried to deposit a very thin layer of aluminum oxide on chalcogenide glass-preforms using a water-based sol-gel process. High temperature glass molding experiments were carried out to investigate the high temperature interfacial reaction between the coated glass gobs and the WC/Co substrate. It was found that surface defects appearing on the molded glass lenses were mainly due to the interfacial chemical reaction between the chalcogenide glass and molds, which leads to a low yield of molded glass lenses than expected. In the case of Al₂O₃ coated glass-preforms, no reaction products were detected on the surfaces of the molded lenses after the molding test. The surface qualities and yield were significantly improved.

In deterministic ion beam figuring (IBF) technology, the application of small ion beam enhances the corrective capability for mid-to-high spatial frequency errors on the optical surface, which directly determines the surface accuracy of the figuring process. But when the diameter of the ion beam becomes smaller, the machining errors will have a stronger influence on the final figuring result, so these errors must be controlled through corresponding methods. We investigate the corrective principle in IBF for surface errors of different spatial frequencies and establish the selection criterion for removal function in different figuring stages to realize the rapid convergence of surface accuracy. Then, through analyzing and controlling the machining errors in the figuring process, high-precision mirrors can be rapidly obtained. Finally, experiments on fused silica planar and spherical samples are conducted on our self-developed IBF system, and their final surface accuracy are both smaller than 1.1 nm RMS (root-mean-square) and 12.0 nm PV (Peak-to-Valley) after several iterations within 20 min.

A novel reconstruction scheme using ultraviolet (UV) structured point for transparent objects three-dimensional (3D) measurement was reported in our previous works. We address two main approaches behind a low-cost system within two suggested configurations (according to the structured light generation source: UV spot and UV line) in order to improve the results accuracy, which endows our system with its adaptability for industrial applications. The first approach consists of determining the optimal configuration of the practical setup while controlling the modeling error (related to the 3D reconstruction approach) with the implementation of an additional validation method in the reconstruction process. The second approach deals with a method which tracks the fluorescence points in the presence of noises inherent to our acquisition system. The specificity of the implemented tracking method relies on spectroscopic analysis. Indeed, experimental investigation has been also carried out to characterize the application. Some digitized objects are presented with an accuracy never reached by any previously reported works dealing with the digitization of transparent objects without any prior preparation.

Shearography is an interferometric technique suitable for detecting defects because they yield singular fringes and high phase values in wrapped and unwrapped phasemaps, respectively. We propose a methodology that leads to the defect size from unwrapped phasemap by extracting the size of the high phase values area. The area size is evaluated, thanks to a wavelet transform algorithm that enables the location of its borders. The performances of the methodology and of the algorithm have been tested by applying them on a defect where the size is known. An error less than 1.5% root mean square was reached. Our approach is independent of the shearing amount and of the phase profile, and it can be extended for other interferometric techniques.

Optical properties of an asymmetric Fabry-Perot (FP) cavity interferometer made up of a conventional metallic mirror and a polymer stabilized cholesteric liquid crystal (PSCLC) Bragg mirror have been investigated. The first FP cavity design comprises a gold mirror, an isotropic layer made up of the polymer glue, a quarter wave plate to convert the input linearly polarized modes into the circularly polarized modes inside the cavity, and the PSCLC Bragg mirror, all sandwiched between two indium tin oxide glass plates. The second FP cavity has a layer of conducting polymer deposited on the quarter-wave plate to apply the electric field only to the cholesteric stack. To have reflectivity above 95% in visible range we implement 30 layers of cholesteric liquid crystal in a planar Grandjean texture. The device compactness and the mirror parallelism due to the monolithic fabrication of FP are advantageous from the technical point of view. We test the FP tunability by shifting the resonance wavelength through an entire period; by applying electric field and/or by varying the temperature.

An intensity-based optical fiber sensor using single-mode-multimode-single-mode fiber sections concatenation is proposed and investigated for use as an intrusion detector. The sensor is composed with simple FC/PC connections between the fiber sections. It is found to be sensitive to intrusion disturbances applied to the multimode fiber section. The transmission spectra of the device under different conditions are measured and its operation as intrusion detector is demonstrated using a single-mode laser source. More than 1 dB variation in the detected power level was observed at a wavelength of 1543 nm. The device proposed is a simple intensity-based sensor, which can be used as a stand-alone device to detect intrusion events over its length or possibly interrogated in a quasidistributed intrusion detection system based on optical time domain reflectometry.

A simple equation for peak wavelength detection of fiber Bragg grating (FBG) with three spectral data is proposed, which has almost the same order of computing load as the conventional maximum search algorithm and uncertainty as the least-squares fit algorithm. The factors effecting performance of the new technique was investigated by simulation. For FBG with spectral bandwidth 0.2 nm, simulation results show that sample resolution lying between 0.07 and 0.16 nm have small measure standard deviation, which is less than 1 pm for SNR greater than 20.75 dB. Experiments were carried out with FBG and interrogator based on InGaAs linear array, and the results verified the effectiveness of the new technique.

We propose a method for designing the filters of one-dimensional photonic crystals (1DPCs) that is based on the traditional transfer matrix method and some fundamental functions. By increasing some design parameters, our method, which can be easily used to design the spectrum shapes of 1DPCs and other types of multilayer structures, can offer designers more choices in selecting the structure forms of 1DPCs. We use our method to design two types of narrow-band reflecting filters based on the high-order band gaps of 1DPCs. These filters, with their peak wavelengths near 1555 nm and filter bandwidths about several nanometers, include a single- and a two-channel filter by adjusting structure parameters. In order to prove our design method effective, we fabricate these filters by lithography and measure their insertion loss spectrums. The experiment and theory results accord very well and prove our method effective.

A scheme of photonic orthogonal frequency division multiplexing (OFDM) signal generation and distribution employing copolarized pumps generated by a dual driver Mach-Zehnder modulator and four-wave mixing inside an optical semiconductor amplifier (SOA) is proposed and evaluated by theoretical analysis and simulations. In this proposal, 12 times optical frequency multiplication is utilized to up-convert the intermediate frequency band OFDM signal to the millimeter wave (mm-wave) band. The system performance under various key parameters of the SOA and the input optical signal is evaluated and discussed. The results present useful insight for the practicality of photonic mm-wave signal generation and distribution in the next-generation optical-wireless access network.

A dual-wavelength optical subassembly (OSA) using a typical glass-sealed transistor outline-can (TO-CAN) package is presented. The proposed OSA has a simple structure and is sufficiently compact to integrate two optical channels in a single TO-CAN package. And the proposed OSA realizes the reduction in cost by reducing the number of parts and the laser welding process. The measurement results of 3 dB of bandwidth of the proposed dual-wavelength OSA are more than 4.5 GHz for transmitter module and more than 4.0 GHz for receiver module. The clear eye diagrams with more than 8.6 dB of the extinction ratio and less than −24.5  dBm of receiver minimum sensitivity at a bit error rate of 10−10 are obtained under 2.5  Gbit/s operations.

An unconventional photonic crystal fiber (PCF) is designed in order to obtain supercontinuum (SC) generation. The distance of the air hole rings is not constant, but it follows the Thue-Morse (ThMo) aperiodic sequence. The spectral broadening of high power femtosecond (fs) input pulses in anomalous dispersion regime is investigated by means of a homemade computer code, based on the generalized nonlinear Schrödinger equation (GNLSE) and implemented via the symmetrized split-step Fourier method (S-SSF). A lot of ThMo PCF transversal sections are simulated, and the one providing the flattest and the widest spectrum is identified and further refined by varying the operating conditions. Three different peak powers (5, 10, 15 kW) and three different pulse durations (40, 50, 100 fs) are investigated at the pump wavelength λP = 1064  nm. The novel ThMo PCF proposed in this paper exhibits a SC figure of merit Φ = 16, very high with respect to the state of the art pertaining to fs input pulses.

Spectral image complexity is an ill-defined term that has been addressed previously in terms of dimensionality, multivariate normality, and other approaches. Here, we apply the concept of the linear mixture model to the question of spectral image complexity at spatially local scales. Essentially, the "complexity" of an image region is related to the volume of a convex set enclosing the data in the spectral space. The volume is estimated as a function of increasing dimensionality (through the use of a set of endmembers describing the data cloud) using the Gram Matrix approach. It is hypothesized that more complex regions of the image are composed of multiple, diverse materials and will thus occupy a larger volume in the hyperspace. The ultimate application here is large area image search without a priori information regarding the target signature. Instead, image cues will be provided based on local, relative estimates of the image complexity. The technique used to estimate the spectral image complexity is described and results are shown for representative image chips and a large area flightline of reflective hyperspectral imagery. The extension to the problem of large area search will then be described and results are shown for a 4-band multispectral image.

We report on the temperature-dependent extension of n-type inversion regions in mercury cadmium telluride (HgCdTe) photodiodes at low temperatures (87 K) compared to inversion regions at room temperature (300 K). Laser-beam-induced-current (LBIC) measurement techniques are used to obtain the photosensitive area extensions of n-type inversion in HgCdTe photodiodes for typical n+-on-p HgCdTe photovoltaic IR detectors. The effect of temperature on the extension of n-type conversion region is investigated by considering the sign of the LBIC signal. Theoretical results show that the hole concentration decreases in multidoped HgCdTe due to the freeze-out effect as the temperature decreases. Consequently, hole concentration is much lower than electron concentration at 87 K. The n-type inversion region extension is shown to be caused with the p-to-n type conversion.

Detecting the vanishing point from a single road image is a challenging problem because there is very limited information in the input image that can help the computer to deduce the genuine location of vanishing point. Besides, the cluttered ambient environment in a real road image sometimes will hinder rather than assist the detection. Learning both the advantages and the limitations of current edge-based and texture-based approaches motivates us to propose a new vanishing point detection method that exploits the intrinsic geometric line structures and color texture properties of general roads. Our approach integrates the efficiency of line segments of edge-based methods, and the orientation coherence concept that is frequently applied in texture-based methods, which can be of great help to improve the accuracy of selecting the right line segments for vanishing point detection. The proposed method has been implemented and tested on over 1000 various road images. These road images exhibit large variations in color, texture, illumination condition, and ambient environment. The experimental results demonstrate that this new method is both efficient and effective in detecting vanishing point when compared to the state-of-the-art edge-based and texture-based methods.

We present an enhanced motion estimation and compensation algorithm by prefiltering reference frames before motion estimation. The conventional block based motion estimation algorithm gives poor performance when abrupt motion change occurs. The proposed algorithm constructs prefilters based on motion vector distribution analysis and compensates temporal sampling artifacts, such as blur or deblur, between adjacent frames. Compared to H.264/AVC, the proposed algorithm achieves significant bit-rate reduction up to 14.59%.

An effectual method is proposed to remove impulse noise from corrupted color images. The spiking cortical model (SCM) is adopted as a noise detector to identify noisy pixels in each channel of color images, and detected noise pixels are saved in three marking matrices. According to the three marking matrices, the detected noisy pixels are divided into two types (type I and type II). They are filtered differently: an adaptive median filter is used for type I and an adaptive vector median for type II. Noise-free pixels are left unchanged. Extensive experiments show that the proposed method outperforms most of the other well-known filters in the aspects of both visual and objective quality measures, and this method can also reduce the possibility of generating color artifacts while preserving image details.

The inter-frame information for analyzing human face movement manifold is modeled by the statistical shape theory. Using the Riemannian geometry principles, we map a sequence of face shapes to a unified tangent space and obtain a curve corresponding to the face movement. The experimental results show that the face movement sequence forms a trajectory in a complex tangent space. Furthermore, the extent and type of face expression could be depicted as the range and direction of the curve. This represents a novel approach for face movement classification using shape-based analysis.

We propose a novel data hiding method for halftone images with homogeneous distribution of embedding positions . The embedding positions are selected randomly. Then a void-and-cluster algorithm is applied to manipulate the positions to form homogeneous distribution. As a result, pleasing visual quality of the halftone image can be obtained. The proposed method is suitable for high payload data-hiding with fantastic image quality. Furthermore, the proposed method can be extended to watermarking mode. Robustness against tampering, cropping, noise addition, filtering, and print-and-scan attacks can be achieved as well.

A new local segmentation model based on binary level set for images with intensity inhomogeneity is proposed. The local segmentation property is guaranteed with the gradient function of the binary level set function (LSF), and the curve evolution precision can be accurate to one-pixel width. Due to utilizing more statistical information which contains local interior, local exterior, and global interior information, the new segmentation energy is more adaptable for local segmentation in the case of intensity inhomogeneity. Since the contour is initialized as a small shape inside the desired object and inflated afterwards in local segmentation, a morphological closing operation is used to regularize the binary LSF, which not only can promote curve inflating, but also can maintain the binary property of the LSF. Experiments on medical images show that the proposed model is more effective and robust than the Chan-Vese (CV), local binary fitting (LBF), localizing region-based active contours (LR-AC), and selective binary and Gaussian filtering regularized level set method (SB-GFRLS) models in local segmentation for images with intensity inhomogeneity.

In super-resolution (SR), a set of degraded low-resolution (LR) images are used to reconstruct a higher-resolution image that suffers from acquisition degradations. One way to boost SR images visual quality is to use restoration filters to remove reconstructed images artifacts. We propose an efficient method to optimally allocate the LR pixels on the high-resolution grid and introduce a mathematical derivation of a stochastic Wiener filter. It relies on the continuous-discrete-continuous model and is constrained by the periodic and nonperiodic interrelationships between the different frequency components of the proposed SR system. We analyze an end-to-end model and formulate the Wiener filter as a function of the parameters associated with the proposed SR system such as image gathering and display response indices, system average signal-to-noise ratio, and inter-subpixel shifts between the LR images. Simulation and experimental results demonstrate that the derived Wiener filter with the optimal allocation of LR images results in sharper reconstruction. When compared with other SR techniques, our approach outperforms them in both quality and computational time.

Optical zoom lenses mounted on a stereo color camera magnify each left and right two-dimensional (2-D) image increasing focal length. However, without adjusting the baseline distance, the optical zoom distorts three-dimensional (3-D) perception because the optical zoom magnifies projected 2-D images not an original 3-D object. We propose a computational approach to stereoscopic zoom that magnifies stereo images without 3-D distortion. We computationally manipulate the baseline distance and convergence angle between left and right images by synthesizing novel view stereo images based on the depth information. We suggest a volume-predicted bidirectional occlusion inpainting method for novel view synthesis. Original color image is warped to the novel view determined by the adjusted baseline and convergence angle. Rear volume of each foreground object is predicted, and the foreground portion of each occlusion region is identified. Then we apply our inpainting method to fill in the foreground and background respectively. Experimental results show that the proposed inpainting method removes the cardboard effect that significantly decreases the perceptual quality of synthesized novel view image but has never been addressed in the literature. Finally, 3-D object presented by stereo images is magnified by the proposed stereoscopic zoom method without 3-D distortion.

Neutrosophy studies the origin, nature, scope of neutralities, and their interactions with different ideational spectra. It is an alternative to the existing logics and represents mathematical uncertainty, vagueness, contradiction, and imprecision. Neutrosophy introduces a new concept to represent indeterminacy, which is a new philosophy to extend fuzzy logic. We introduce neutrosophy to color image segmentation and develop a novel unsupervised algorithm. We determine the centers of image clusters by using color information in red, green, and blue (RGB) color space and define neutrosophic indeterminacy by using spatial information in CIE (L*u*v*) color space. By applying neutrosophy, we integrate color and spatial information, as well as global and local information in two color spaces: RGB and CIE, respectively. Most existing segmentation algorithms have the over-segmentation problem, which causes segmentation accuracy to be lower, especially when noisy images are processed. Neutrosophy has noise-tolerant ability. In the experiment section, USC-SIPI image database is used to compare the proposed algorithm with several fuzzy and non-fuzzy color segmentation algorithms. The experiments demonstrate that the proposed algorithm can handle the segmentation tasks well and can even process noisy images with better accuracy. They also show its noise-tolerant ability. The proposed approach is more effective and powerful for color image segmentation, which can find wide applications in related areas.

In recent years, an unparalleled volume of textual information has been transported over the Internet via email, chatting, blogging, tweeting, digital libraries, and information retrieval systems. As the volume of text data has now exceeded 40% of the total volume of traffic on the Internet, compressing textual data becomes imperative. Many sophisticated algorithms were introduced and employed for this purpose including Huffman encoding, arithmetic encoding, the Ziv-Lempel family, Dynamic Markov Compression, and Burrow-Wheeler Transform. My research presents novel universal algorithm for compressing textual images. The algorithm comprises two parts: 1. a universal fixed-to-variable codebook; and 2. our row and column elimination coding scheme. Simulation results on a large number of Arabic, Persian, and Hebrew textual images show that this algorithm has a compression ratio of nearly 87%, which exceeds published results including JBIG2.

We present a novel algorithm based on nonnegative least square (LS) estimation for visual object tracking. Most existing algorithms, such as template matching, only consider each candidate separately. We offer another, new perspective. The template model is approximated by the linear combination of candidates in the space spanned by the feature vectors associated with particles. The coefficient of the linear combination is achieved through solving a nonnegative LS problem, and then it is used to evaluate the similarity between the template and candidates. Experimental results demonstrate that the proposed algorithm has better tracking accuracy than the compared algorithms and strong robustness against noise.

Variational methods are the most widely used approaches for optical flow computation. Many complicated algorithms have been proposed to improve their performance, yet little work has focused on how to select the optimal smoothness parameter λ of the variational optical flow algorithm itself. We present a weighted root mean square error method to automatically select the optimal smoothness parameter λ. Furthermore, we detail a scientific method for selecting the reference λ0 based on the quality of the frame, and propose an efficient brute-force approach to assign a group of λ, that will reduce the number of λ candidates to be tested by cutting down the search range. Experimental results validate the effectiveness of our methods.

An efficient method for reliable multiclass pattern recognition using a bank of adaptive correlation filters is proposed. The method can recognize and classify multiple targets from an input scene by using both the intensity and phase distributions of the output complex correlation plane. The adaptive filters are synthesized with the help of an iterative algorithm based on synthetic discriminant functions with complex constraints. The algorithm optimizes the discrimination capability of the adaptive filters and determines the minimum number of filters in a bank to guarantee a desired classification efficiency. As a result, the computational complexity of the proposed system is low. Computer simulation results obtained with the proposed approach in cluttered and noisy scenes are discussed and compared with those obtained through existing methods in terms of recognition performance, classification efficiency, and computational complexity.

A modal technique is used for modeling the problem of light propagation through masks with subwavelength features. Different approaches for the proper treatment of the excitation and the finite window are discussed. Results obtained using the technique are compared to those obtained by the volume integral equation method and the finite difference time domain method. The proposed technique shows very good agreement with both methods as well as significant reduction in the simulation time compared to the finite difference time domain method.

Potassium titanyl phosphate (KTP) is mostly used in all-solid-state lasers as a good nonlinear optical crystal. Knowledge of variations in the weak absorption of different types of KTP crystals is important for the application. In this study, the flux-grown KTP crystals with titanium from TiO₂, TiCl₄, and Ti(OC₄H₉)4, respectively, and the hydrothermal-grown KTP crystal were investigated. The weak absorption values of the KTP crystals were measured at 1064 nm and 532 nm by photothermal common-path interferometer. The weak absorption values of four samples were 100  ppm·cm−1, 800  ppm·cm−1, 45  ppm·cm−1, 1064  ppm·cm−1 at 1064 nm, and 2.6×104  ppm·cm−1, 1.6×105  ppm·cm−1, 1.2×104  ppm·cm−1, 2.25×102  ppm·cm−1 at 532 nm, respectively. The results showed that the weak absorption values of the flux-grown KTP with titanium from Ti(OC4H9)4 and the hydrothermal-grown KTP were low values at 1064 nm. In addition, the weak absorption value of the hydrothermal-grown KTP was at least two orders of magnitude lower than that of the flux-grown KTP at 532 nm. From the results, we concluded that the KTP grown by titanium from Ti(OC₄H₉)4 represented a better quality than the other two flux-grown KTP crystals. The quality of the hydrothermal-grown KTP was obviously better than the flux-grown KTP.

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