Every February, we provide a report to the Optical Engineering constituency on the health of the journal. The report reviews the performance of the journal as well as provides a description of major changes that have happened over the past year. The report also describes important issues that must be addressed along with proposed efforts to keep the journal healthy and relevant.

Human motion capture has a wide variety of applications, and in vision-based motion capture systems a major issue is the human body model and its initialization. We present a computer vision algorithm for building a human body model skeleton in an automatic way. The algorithm is based on the analysis of the human shape. We decompose the body into its main parts by computing the curvature of a B-spline parameterization of the human contour. This algorithm has been applied in a context where the user is standing in front of a camera stereo pair. The process is completed after the user assumes a predefined initial posture so as to identify the main joints and construct the human model. Using this model, the initialization problem of a vision-based markerless motion capture system of the human body is solved.

Abstract unavailable.

This paper reviews three-dimensional (3-D) and four-dimensional (4-D) imaging technology, from Wheatstone through today, with some prognostications for near future applications. This field is rich in variety, subject specialty, and applications. A major trend, multi-view stereoscopy, is moving the field forward to real-time wide-angle 3-D reconstruction as breakthroughs in parallel processing and multi-processor computers enable very fast processing. Real-time holography meets 4-D imaging reconstruction at the goal of achieving real-time, interactive, 3-D imaging. Applications to telesurgery and telemedicine as well as to the needs of the defense and intelligence communities are also discussed.

A brief history of recent developments in electronic stereoscopic displays is given concentrating on products that have succeeded in the market place and hence have had a significant influence on future implementations. The concentration is on plano-stereoscopic (two-view) technology because it is now the dominant display modality in the marketplace. Stereoscopic displays were created for the motion picture industry a century ago, and this technology influenced the development of products for science and industry, which in turn influenced product development for entertainment.

The encoding of three-dimensional image pairs by polarization was proposed as early as the 1890s, perhaps stimulated by the popularity of stereoscopic photography, the proliferation of devices for viewing side-by-side stereoscopic images, and the invention of the anaglyph. The introduction of inexpensive sheet polarizing material gave rise to new three-dimensional technologies, starting in the 1930s with 16-mm black-and-white motion pictures projected by paired projectors equipped with orthogonally oriented polarizing filters. Further advances included the introduction of color, the concept of printing left- and right-eye images on a common carrier, and most recently the development of digital photography and the utilization of polarizers in both two- and three-dimensional digital color display.

Despite rapid advances in technology, 3-D movies are impractical for general movie viewing. A new approach that opens all content for casual 3-D viewing is needed. 3Deeps-advanced microprocessor controlled optoelectronic spectacles-provides such a new approach to 3-D. 3Deeps works on a different principle than other methods for 3-D. 3-D movies typically use the asymmetry of dual images to produce stereopsis, necessitating costly dual-image content, complex formatting and transmission standards, and viewing via a corresponding selection device. In contrast, all 3Deeps requires to view movies in realistic depth is an illumination asymmetry-a controlled difference in optical density between the lenses. When a 2-D movie has been projected for viewing, 3Deeps converts every scene containing lateral motion into realistic 3-D. Put on 3Deeps spectacles for 3-D viewing, or remove them for viewing in 2-D. 3Deeps works for all analogue and digital 2-D content, by any mode of transmission, and for projection screens, digital or analogue monitors. An example using aerial photography is presented. A movie consisting of successive monoscopic aerial photographs appears in realistic 3-D when viewed through 3Deeps spectacles.

We present a technique for imaging full-color 3-D images with a single camera in this paper. Unlike a typical 3-D-imaging system comprising two independent cameras each contributing one viewpoint, the technique presented here creates two viewpoints using a single-lens camera with a bipartite filter whose bandpass characteristics are complementary to each other. The bipartite filter divides the camera's limiting aperture into two spatially separated apertures or viewpoints that alternately image an object field using filter-passband matched, time-sequenced illumination. This technique was applied to construct a 3-D camera to image scenes at a working distance of 10 mm. We evaluated the effectiveness of the 3-D camera in generating stereo images using statistical comparison of the depth resolutions achieved by the 3-D camera and a similar 2D camera arrangement. The comparison showed that the complementary filters produce effective stereopsis at prescribed working distances.

We describe a high-performance stereo camera system to capture image sequences with high temporal and spatial resolution for the evaluation of various image processing tasks. The system was primarily designed for complex outdoor and traffic scenes that frequently occur in the automotive industry, but is also suited for other applications. For this task the system is equipped with a very accurate inertial measurement unit and global positioning system, which provides exact camera movement and position data. The system is already in active use and has produced several terabytes of challenging image sequences which are partly available for download.

A novel three-dimensional (3-D) photorealistic texturing process is presented that applies a view-planning and view-sequencing algorithm to the 3-D coarse model to determine a set of best viewing angles for capturing the individual real-world objects/building's images. The best sequence of views will generate sets of visible edges in each view to serve as a guide for camera field shots by either manual adjustment or equipment alignment. The best view tries to cover as many objects/building surfaces as possible in one shot. This will lead to a smaller total number of shots taken for a complete model reconstruction requiring texturing with photo-realistic effects. The direct linear transformation method (DLT) is used for reprojection of 3-D model vertices onto a two-dimensional (2-D) images plane for actual texture mapping. Given this method, the actual camera orientations do not have to be unique and can be set arbitrarily without heavy and expensive positioning equipment. We also present results of a study on the texture-mapping precision as a function of the level of visible mesh subdivision. In addition, the control points selection for the DLT method used for reprojection of 3-D model vertices onto 2-D textured images is also investigated for its effects on mapping precision. By using DLT and perspective projection theories on a coarse model feature points, this technique will allow accurate 3-D texture mapping of refined model meshes of real-world buildings. The novel integration flow of this research not only greatly reduces the human labor and intensive equipment requirements of traditional methods, but also generates a more appealing photo-realistic appearance of reconstructed models, which is useful in many multimedia applications.

A novel method is presented to simultaneously measure shape and color information of artifacts containing color features. The technique operates by projecting composite red, green, and blue fringe patterns onto the surface of colorful objects. Theoretical analysis proves that there is no crosstalk between color channels during phase calculation by phase-shifting algorithm when three fringe patterns with the same fringe number are coded into red, green, and blue channels to form a composite RGB fringe pattern image. The color channel giving the maximum modulation depth at each pixel is used to measure shape information. Since three color channels are used, color information of the object surface can be extracted with high dynamic range from the same fringe pattern images. Using the recently developed color fringe projection system, composite RGB fringe patterns are projected onto colorful objects to test the proposed method. The experimental results show that the range of colors that can be measured and that shape and color information of colorful objects can be reliably obtained.

The authors propose a new algorithm for 3-D construction from a sequence of images based on a new corollary that the projective depth can be comprehended as a scalar factor between two 3-D points when reconstructed from three images. This algorithm constructs the partial models of an object using two consecutive images in the image sequence and integrates the obtained partial models to a complete one on the basis of this new corollary. In order to avoid accumulation of errors in the integration process, this algorithm modifies the reconstruction results based on a simplified Iterative Closest Point (ICP) algorithm. We have carried out two groups of experiments based on images captured from a library environment. In one group of experiments, sparse points are used to reconstruct regular objects; in the other group of experiments, dense points are employed. We compared experimental results of the proposed algorithm with the optimization method using the fundamental matrix, which demonstrated that the proposed algorithm yielded better efficiency and accuracy of the 3-D reconstruction. Experiments also showed that the reconstruction errors of the proposed method were within 5%.

Lateral resolution is a particularly challenging concept to quantify in triangulation-based three-dimensional (3-D) imaging systems. We present these challenges, then describe an artifact-based methodology for evaluating the lateral resolution of a triangulation-based 3-D imaging system that uses laser spots or laser lines. In particular, the response of a 3-D imaging system to a spatial discontinuity (step edge) has traditionally been modeled as a first-order linear system. We model the response of a triangulation-based laser imaging system to a spatial step edge from first principles and demonstrate that the response should be modeled as a non linear system. This model is then used as a basis for evaluating the lateral (structural) resolution of a triangulation-based laser imaging system.

As a type of optical measuring apparatus, the charge-coupled diode (CCD) camera provides the capability of increasing the speed of measurement by inspecting an area with only one shot. However, the CCD camera's high-variation range of reflectivity presents an exceptional challenge for the optical measurement established on the surface. We present a method that could enable one to acquire an image with a high-dynamic range in one shot without any reduction in spatial resolution. Because of the sufficient signal-to-noise ratio, the method presented could perform the robustness of the phase-retrieving algorithm, and the surface topography could be measured more accurately.

We present a simple and fast integration method, which can fuse registered multiple, overlapping range images effectively while preserving the detailed features. First, normal vectors of the nodes in each range image are estimated and the registered multiple overlapping range images are combined into one point set. Due to registration errors, the normal vectors of homogeneous nodes in the overlapping areas would differ from each other. Thus, the normal vectors of the nodes are corrected iteratively by weighted averaging their neighboring normal vectors. Second, the combined point set is partitioned into a number of small clusters using the k-means clustering algorithm based on user-defined space interval. The clusters subsequently are subdivided into smaller subclusters by using the standard normal vector deviation as a measure of cluster scatter. Finally, in the cluster, the local maxima model, obtained using the mean shift clustering algorithm, is employed to represent the cluster. The proposed method is fast because it does not need to detect iteratively the overlapping areas, which is usually time consuming. In addition, because of the noisy filtering property of the mean shift clustering algorithm, the novel method can produce a smooth and watertight point surface while preserving the detailed features.

The study presents a method for registration of terrestrial light detection and ranging point clouds based on geometric features (GFs) without using targets. It aims to solve the rotation and translation between two data sets using geometric features, including points, lines, planes, and cylinders. Conjugate planes are used to solve the rotation and the intersected points of the axes of the cylinders and planes are used as conjugate points to solve the translation. Based on the result from an experiment, it has been demonstrated that the proposed approach is capable of giving a reliable and satisfactory registration solution.

To create faithful reproduction of a cultural heritage object, it is crucial to gather information on intrinsic optical properties of the object's surface, as well as its geometry. An integrated device has been developed that performs a three-dimensional measurement using structured light projection, followed by multispectral imaging for precise color retrieval and directional illumination for estimating bidirectional reflectance distribution function (BRDF) parameters. The main advantage shown in this work is the use of only one detector during the whole acquisition process to assure ideal correspondence of multimodal surface data in the image space. A method is shown for performing the measurement using an integrated device. Methods of data organization and processing are described facilitating robust operation of the developed software. A prototype setup for the integrated system is presented together with measurement parameters and sample measurement.

Modeling the three-dimensional (3-D) shape of plant stems is important in the study of plant growth in precision agriculture. To construct a 3-D model of real plant stems from images quickly, a novel volumetric method based on line-based models is proposed. Line-based models are constructed on the coarse 3-D skeleton of the plant stems, then carved with respect to silhouette consistency. The surface points on the plant stems are calculated from line-based models. Finally, a mesh surface model can be extracted from the surface points. The proposed method can give precise results together with low time complexity and space complexity. Experiments based on both synthetic and real data are presented to evaluate the speed and preciseness of the proposed method.

The location-aware Internet is inspiring intensive work addressing the automated assembly of three-dimensional models of urban spaces with their buildings, circulation spaces, vegetation, signs, even their above-ground and underground utility lines. Two-dimensional geographic information systems (GISs) and municipal utility information exist and can serve to guide the creation of models being built with aerial, sometimes satellite imagery, streetside images, indoor imaging, and alternatively with light detection and ranging systems (LiDARs) carried on airplanes, cars, or mounted on tripods. We review the results of current research to automate the information extraction from sensor data. We show that aerial photography at ground sampling distances (GSD) of 1 to 10 cm is well suited to provide geometry data about building facades and roofs, that streetside imagery at 0.5 to 2 cm is particularly interesting when it is collected within community photo collections (CPCs) by the general public, and that the transition to digital imaging has opened the no-cost option of highly overlapping images in support of a more complete and thus more economical automation. LiDAR-systems are a widely used source of three-dimensional data, but they deliver information not really superior to digital photography.

Dimensional measurement of hot heavy forgings is desirable to permit real-time process control, but usually it is inconvenient because of the difficulty in working with very hot workpieces. We present a new three dimensional (3D) measuring approach based on a two-dimensional laser range sensor (TLRS). First, the measurement system is obtained by assembling a TLRS, an axis of rotation, and a servo motor, which rotates the scan plane of the laser ranger sensor and lets the TLRS scan forgings in different planes. Therefore, the coordinates of forging surface points can be obtained in a sensor coordinate system (SCS). According to the transformation matrix between the SCS and measurement coordinate system (MCS), coordinates of points in different SCSs can be transferred into one fixed MCS. Hence the actual 3D models of hot heavy forgings can be reconstructed by using a triangulated irregular network and be optimized by employing improved Delaunay rules. Different parameters of forgings, such as lengths and diameters, can be measured based on the 3D model. The new method is verified by experiments in both the laboratory and the forging workshop. The experimental results indicate that it is much more practical and convenient for the real-time, onsite measurement of hot heavy forgings.

The focusing evaluation method based on wavelet transform and adaptive genetic algorithm (AGA) is developed in this paper. First, db7 wavelet transform is performed and the corresponding images are evaluated. Afterward, the optimal evaluation region is searched automatically in 2D wavelet coefficients by AGA. Finally, the criteria function based on the weighted MWT² operator is used to evaluate the focusing condition. The wavelet base, order number of vanishing moments, and wavelet decomposition level are the key factors in constructing the operator. The parameters of new focus measure operator are analyzed and verified through experimental methods. The comparative experiments with other methods show that the AGA method not only could find the approximate optimal evaluation window quickly and accurately, but it has better generality as well. The weighted evaluation function of the MWT² operator based on the db7 wavelet has higher sensitivity and better real-time performance.

We have characterized a photoresist used for the fabrication of gray-scale diffractive optic elements in terms of Dill's and Mack's model parameters. The resist model parameters were employed for the simulations of developed resist profiles for sawtooth patterns executed by solving the Eikonal equation with the fast-marching method. The simulated results were shown to be in good agreement with empirical data.

We present a step height measurement technique using a lateral shearing cyclic path optical configuration (CPOC) setup and polarization phase shifting interferometry (PPSI). In the technique, the CPOC setup generates two orthogonally polarized, laterally sheared, converging beams that get focused at the back focal plane of a positive lens placed at the input beam of the CPOC setup. These focusing beams are reflected back into the CPOC setup by the step optics, positioned in such a way that one of the surfaces of the step optics coincides exactly with the focus point of one of the laterally sheared focusing beams. The CPOC recombines the beams reflected from the step surfaces and the beams re-pass through the lens, which produces collimated and spherical interfering wave fronts for the respective beams. Using PPSI, the radius of the spherical wavefront emerging from the lens, which is related to the focal shift introduced between the reflected beams due to the step height, is determined. The novelty of the technique is the introduction of the CPOC setup and the use of a single wavelength light source to determine the large step height. Results obtained for a step height of 1.340 mm are presented.

2-D digital image correlation (DIC) is traditionally used with the camera's axis perpendicular to the object surface. The nonperpendicular camera alignment will inevitably introduce measurement error. An oblique-axis 2-D DIC method based on photogrammetry compensation is proposed in this paper. Not less than three reference points are pasted on the specimen surface. The photogrammetry technique is first used to get the 3-D coordinates of these reference points. A reference plane is obtained by fitting these reference points. Then the oblique-axis camera is oriented by using the space resection method. During deformation measurement, for each image points matched by DIC, its 3-D point can be acquired by simply intersecting the point ray with the reference plane. Using this method, not only is the measurement error caused by oblique-axis compensated, but also the displacement in millimeters rather than in pixels can be determined directly. Experiments results indicate that, for in-plane deformation in oblique-axis measurement situation, our method has comparable accuracy with 3-D DIC.

The frequency response of photo-thermal deflection spectroscopy, caused by infrared resonant absorption in analyte gases in open air using a common collinear pump-probe beam configuration, is studied using experiment and theory. The heat diffusion simulation and the experiment showed a roll-off of 50 to 60 Hz. This is in agreement with work performed by other authors. It was found, that the frequency response curve shapes for the numerical simulations of the deflection angle and the experimental deflection voltage signal disagreed by less than 20 percent over the range of 10 Hz to 1 kHz. A frequency dependent turbulence model is used to determine a noise floor as a function of modulation frequency, between 5 and 5000 Hz, for a probe beam at several different standoff distances from the analyte using parameter scaling. From both experiments, the turbulence equivalent concentration is extracted from the extrapolated curves. The best extrapolations give absorbances of 2·10−5 and 3.2·10−5 for 50°C and 75°C thermal sources, respectively. The most sensitive parameters, which the equivalent concentration depends on, are pump power, pump radius, standoff distance, and absorption length of the gas sample. Lens focusing at the detector allows a smaller detector to be used for probe beams which diverge from the source.

Our study shows that the phase error caused by improperly defocused binary structured patterns correlates to the depth z. This finding leads to a novel uniaxial three-dimensional shape measurement technique without triangulation. Since the measurement can be performed from the same viewing angle, this proposed method overcomes some limitations of the triangulation-based techniques, such as the problem of measuring deep holes. Our study explains the principle of the technique and presents some experimental results to verify its feasibility.

Salinity and turbidity are two important seawater properties in oceanography. We have studied the use of a high resolution refractometer to measure the salinity of seawater. The requirement of a multifunctional sensor makes the turbidity measurement based on our refractometer valuable. We measure turbidity according to the attenuation of the laser beam caused by the scattering. With the configuration of our refractometer, several issues impact the laser beam attenuation measurement, while the measurement of salinity is impacted by the scattering as well. All these issues make light distribution nonsensitive sensors such as position sensitive devices unsuitable for building the refracto-turbidimeters. To overcome these issues, a charge-coupled device combined with a new location algorithm is used to measure both the refractive index and the attenuation. Several simulations and experiments are carried out to evaluate this new method. According to the results, the way to improve the resolution is discussed as well. The validation of our method is proved by comparison to the nephelometer specified by the nephelometric turbidity unit standard.

Mg/SiC multilayers have been selected to coat the primary and secondary mirrors of the SCORE (Sounding-rocket CORonagraphic Experiment) telescope, a part of the NASA HERSCHEL program. Their experimental reflectance at the He II 30.4 nm wavelength is twice as much that of standard Mo/Si multilayer coatings, with a large improvement of the instrument effective area. Nevertheless, their long-term stability still needs to be evaluated in order to consider them as a valuable candidate for instrumentation of a long term space mission. A study is carried out on different Mg/SiC samples designed and fabricated varying the structural parameters and/or the capping layer material and thickness, which have been monitored for four years after deposition.

The temporal contrast is an important factor affecting the application of ultra-intense and ultra-short lasers. In this paper, we develop a double chirped-pulse-amplification (CPA) front-end system with an intermediate nonlinear temporal pulse filter to improve the temporal contrast at a sub-petawatt Ti:sapphire laser facility, i.e. the super intense laser for experiment on the extremes (SILEX-I). The temporal pulse filter employs cross-polarized wave (XPW) generation to suppress the amplified spontaneous emission (ASE). The design output energy is 320 mJ for the front-end system. The experimental results show that the output energy of the double CPA system is 360 mJ. The ASE pedestal is suppressed significantly and the temporal contrast is improved by around three orders of magnitude.

We present an analytical model to analyze the influence of carrier dynamics on the static and dynamic responses of transistor laser (TL). Our analysis is based on solving the continuity equation and the rate equations which incorporate the virtual states as a conversion mechanism. We show that the details of the dc and small signal behavior of transistor lasers are strongly affected by the escape and capture times of carriers in quantum well (QW). Also, the effects of carrier recombination lifetime in the quantum well and base regions on the TL static and dynamic performances are investigated.

Autonomous mobile robots have been widely studied not only as advanced facilities for industrial and daily life automation, but also as a testbed in robotics competitions for extending the frontier of current artificial intelligence. In many of such contests, the robot is supposed to navigate on the ground with a grid layout. Based on this observation, we present a localization error correction method by exploring the geometric feature of the tile patterns. On top of the classical inertia-based positioning, our approach employs three fiber-optic sensors that are assembled under the bottom of the robot, presenting an equilateral triangle layout. The sensor apparatus, together with the proposed supporting algorithm, are designed to detect a line's direction (vertical or horizontal) by monitoring the grid crossing events. As a result, the line coordinate information can be fused to rectify the cumulative localization deviation from inertia positioning. The proposed method is analyzed theoretically in terms of its error bound and also has been implemented and tested on a customary developed two-wheel autonomous mobile robot.

We present a new method to generate broadband cascaded four-wave mixing (FWM) products in the silicon-on-insulator (SOI) waveguide. A simulation model of the nonlinear Schrödinger equation is used to describe the cascaded FWM in the SOI waveguide, which consists of launching two strong pump waves near the zero-dispersion wavelength of the very short (just a few millimeters) SOI waveguide. The numerical results based on the split step Fourier method have demonstrated that the output cascaded FWM products represent bandwidth of more than 1000 nm (range from C-band to IR-band). We also analyze the remarkable influences of parameters of the waveguide length, the pump power, and the dispersion slope on the cascaded FWM products in the SOI waveguide.

Dielectric-coated metallic hollow fiber (DMHF) is an increasingly popular fiber for the delivery of terahertz (THz) wave. There is a need for small-diameter fibers in a variety of THz wave applications. Transmission characteristics of DMHF with subwavelength diameter in the THz region are numerically investigated. The effective refractive indices, attenuation constants, and power distributions are presented. The effect of the metal layer on enhancing the modal field confinement is demonstrated by comparing the power distribution of the fiber to that of the polymer tube. Attenuation dependence on the dielectric layer is studied concerning the layer thickness and the refractive index. Both the optimal thickness and the optimal refractive index for the dielectric layer are dependent on the core size. Fiber with a smaller core requires a thicker dielectric layer and lower dielectric refractive index to achieve low attenuation. The results are important to the design of subwavelength diameter DMHF for the transmission of THz waves.

Epoxy acrylate has been widely used as optical resin for applications such as cladding, the core of a waveguide, and other photonic devices. In this study, sustainable resin from edible oil was used as an alternative to epoxy acrylate. Structural features and the transmission of planar thin-film resin from an ultraviolet-visible spectroscopy (UV-VIS) spectrometer were investigated upon UV exposure. It was found that high transmission still persists for all samples with and without an UV absorber for exposed and unexposed samples. The film was found to absorb strongly below 400 nm. A change in the cut-off wavelength was observed upon exposure. Thin-film hardness and its dynamic indentation in the load-unload mode with different test forces were evaluated. Vickers hardness and the elastic modulus were determined for unacrylated epoxidized soybean oil (ESO) and acrylated epoxidized soybean oil (AESO). It was found that the AESO has a higher Vickers hardness and elastic modulus than those of unacrylated thin film. The Vickers hardness and elastic modulus were found to increase as the applied test force increased. The refractive index, thickness, and modes present were characterized from a spin-coated planar thin film. The refractive index in the transverse electric mode (TE) and transverse magnetic mode (TM) were determined and compared for unacrylated and acrylated epoxidized oil.

This report is a detailed study on the application of digital back-propagation technique for wavelength-division multiplexing (WDM) transmission of amplitude and differential phase shift keying (ADPSK)-modulated signal. We find that the precompensation using digital back-propagation increases the transmission distance by more than a factor of two. We find that the performance improvement from digital precompensation strongly depends on the dispersion map of the transmission link and the optimum performance was obtained when about 3% to 5% of the span dispersion is under-compensated by in-line dispersion compensators and later compensated for at the end of the entire transmission link. We also find that the precompensation is robust enough to the variation of various link parameters which can occur in the deployment or operation of transmission systems.

In null computed generated hologram (CGH) test of optical elements, fitting method is needed in null CGH design to generate continuous phase function from the ray-traced discrete phase data. The null CGH for freeform testing usually has a deformed aperture and a high order phase function, because of the aberrations introduced by freeform wavefront propagation. With traditional Zernike polynomial fitting method, selection of an orthogonal basis set and choosing number of terms are needed before fitting. Zernike polynomial fitting method is not suitable in null CGH design for freeform testing; a novel CGH design method with cubic B-spline interpolation is developed. For a freeform surface with 18×18  mm² rectangular aperture and 630 μm peak-to-valley undulation, the null CGH with a curved rectangular aperture is designed by using the method proposed. Simulation and experimental results proved the feasibility of the novel CGH design method.

We extend the theory of beam wander for propagation through atmospheric turbulence to the case of a focused partially coherent beam (PCB). In addition to investigating the beam wander expression, we restate expressions for the beam size, long- and short-time average beam intensity profile, and the on-axis scintillation index of tracked and untracked beams. A wave optics simulation is implemented and the numerical results are compared with corresponding analytic results. The cases examined involve turbulence strengths ranging from C_n² = 10−16 to 10−14  m−2/3 and for various horizontal paths ranging from 1 to 10 km. Although the extended analytic theory stems from a study of coherent beams, the simulation results show good agreement with the analytical results for PCBs in fluctuation regimes ranging from weak to intermediate.

To extract circular array targets from high-spatial resolution optical satellite images, we propose an efficient two-step detection framework. In the first stage, we propose a multiscale histogram contrast (MHC) saliency evaluation model to detect salient objects. This saliency model is able to highlight all salient areas with well-defined boundaries and effectively suppress the obvious background textures. Moreover, the generated saliency map can be used to find the locations of potential targets most likely causing visual attention, which greatly decreases the computation cost in later processes. In the second stage, we extract task-related targets from these salient objects by removing the irrelevant salient areas according to the special properties of the targets. In this paper, we present a circular array targets-detection method based on the saliency map produced by the proposed saliency detector. First we extract the circular objects from the saliency map using simple shape features, which are then clustered through a graph-based approach to locate the target areas. To evaluate the performance of our saliency model and targets extraction scheme, we carried out many experiments on large-field, high-spatial resolution remote-sensing images and achieved promising results both in efficiency and precision.

To improve the mechanical characteristics of actively controlled continuous faceplate deformable mirrors in adaptive optics, a strategy for reducing crosstalk between adjacent actuators and for suppressing low-order eigenmodes is proposed. The strategy can be seen as extending Saint-Venant's principle beyond the static case, for small local families of actuators. An analytic model is presented, from which we show the feasibility of the local control. Also, we demonstrate how eigenmodes and eigenfrequencies are affected by mirror parameters, such as thickness, diameter, Young's modulus, Poisson's ratio, and density. This analysis is used to evaluate the design strategy for a large deformable mirror, and how many actuators are needed within a family.

We introduce a multifractal analysis for detecting the small-size pest (e.g., whitefly) images from a sticky trap in situ. An automatic attraction system is utilized for collecting pests from greenhouse plants. We applied multifractal analysis to segment action of whitefly images based on the local singularity and global image characteristics. According to the theory of multifractal dimension, the candidate blobs of whiteflies are initially defined from the sticky-trap image. Two schemes, fixed thresholding and regional minima obtainment, were utilized for feature extraction of candidate whitefly image areas. The experiment was conducted with the field images in a greenhouse. Detection results were compared with other adaptive segmentation algorithms. Values of F measuring precision and recall score were higher for the proposed multifractal analysis (96.5%) compared with conventional methods such as Watershed (92.2%) and Otsu (73.1%). The true positive rate of multifractal analysis was 94.3% and the false positive rate minimal level at 1.3%. Detection performance was further tested via human observation. The degree of scattering between manual and automatic counting was remarkably higher with multifractal analysis (R² = 0.992) compared with Watershed (R² = 0.895) and Otsu (R² = 0.353), ensuring overall detection of the small-size pests is most feasible with multifractal analysis in field conditions.

Optical imaging systems often suffer from distortion artifacts which impose important limitations on the direct interpretation of the images. It is possible to correct for these aberrations through image processing, but due to their calculation-intensive nature, the required corrections are typically performed offline. However, with image-based applications that operate interactively, real-time correction of geometric distortion artifacts can be vital. We propose a new method to generate undistorted images by implementing the required distortion correction algorithm on a commercial graphics processing unit (GPU), distributing the necessary calculations to many stream processors that operate in parallel. The proposed technique is not limited to affine lens distortions but allows for the correction of arbitrary geometric image distortion artifacts through individual pixel resampling at display rates of more than 30 frames per second for fully processed images (1024×768  pixels). Our method enables real-time GPU-based geometric lens distortion correction without the need for additional digital image processing hardware.

We report an algorithm for searching and tracking the center of the circular interference fringes. The algorithm was programmed by VB.NET for processing the interference images captured by CCD camera. Images were changed into binary gray-level format by the Otsu method. The circular scanning method was used to extract the outline of circular interference fringes, and then the coordinates of the perpendicular subtenses were used to remove noise pixels. Finally, the coordinate of the center was calculated by statistical method. The experimental results are in good agreement with the simulation images. The algorithm had subpixel accuracy and anti-noise ability. Thus, the algorithm can be used in accurate measurement for its automatic processing ability.

We propose an innovative and efficient approach to improve K-view-template (K-view-T) and K-view-datagram (K-view-D) algorithms for image texture classification. The proposed approach, called the weighted K-view-voting algorithm (K-view-V), uses a novel voting method for texture classification and an accelerating method based on the efficient summed square image (SSI) scheme as well as fast Fourier transform (FFT) to enable overall faster processing. Decision making, which assigns a pixel to a texture class, occurs by using our weighted voting method among the "promising" members in the neighborhood of a classified pixel. In other words, this neighborhood consists of all the views, and each view has a classified pixel in its territory. Experimental results on benchmark images, which are randomly taken from Brodatz Gallery and natural and medical images, show that this new classification algorithm gives higher classification accuracy than existing K-view algorithms. In particular, it improves the accurate classification of pixels near the texture boundary. In addition, the proposed acceleration method improves the processing speed of K-view-V as it requires much less computation time than other K-view algorithms. Compared with the results of earlier developed K-view algorithms and the gray level co-occurrence matrix (GLCM), the proposed algorithm is more robust, faster, and more accurate.

Active contour models based on a level set function, which is a useful and implicit image representation tool, can be conveniently implemented. These level set-based active contour models optimized by a gradient decent flow method commonly lead to the problems of the active curves evoluting slowly and the segmentation results becoming highly dependent on initial locations. We develop a method using normalized graph cut to minimize the energy of the coupled-curve evolution model, which is based on the idea of maximizing the separation of the mean intensities of the two regions inside and outside the active curves. Using the minimum cut method, experiments demonstrate the computation time of the proposed method is much less than the level set-based method.

Precise image alignment is considered a critical issue in industrial visual inspection, since it performs an accurate pose to the object in inspected images. Recently, image alignment based on neural networks has become very popular due to its performance at speed. However, such a method has difficulty when applied to the alignment of images on a large range of affine transformation. To address this, a cooperative neural-fuzzy network (CNFN) with association rule mining-based evolutionary learning algorithm (ARMELA) is proposed. Unlike traditional neural network-based approaches, the proposed CNFN utilizes a coarse-to-fine alignment procedure to adapt image alignment to a larger range of affine transformation. The proposed ARMELA combines the self-adaptive method and association rules selection method to self-adjust the structure and parameters of the neural-fuzzy network. Furthermore, L2 regularization is adopted to control ARMELA such that the convergence speed increases. Experimental results show that the performance of the proposed scheme is superior to the traditional neural network methods in terms of accuracy and robustness.

Skin detection plays an important role in many applications, including face detection, human motion analysis, and objectionable image filtering. We propose a novel skin detection approach named multiple Gaussian models (MGMs). This approach combines multiple single Gaussian models and determines each model in order to maximize the true positive rate (TPR) of skin detection subject to a fixed predefined false positive rate (FPR). We derive the discrete and continuous forms of MGM approaches in the paper. The proposed approach has almost optimal performance for a broad range of FPRs in the Gaussian framework. Moreover, it has low computational costs in skin detection for new image instances. Experimental results show that the MGM approach has better skin detection performance than previous methods within the Gaussian framework.

Automatic assessment of condition in ductwork is very desirable in applications. Presented is a visual condition diagnosis approach, which is capable of processing images rapidly and achieving high accuracy rates. A hierarchical coarse-to-fine image segmentation method is employed. False alarms could thus be progressively eliminated, which is robust in strongly noisy conditions. The simple classifiers combined in a cascade quickly classify the detected images and discard the uninterested (non-object) images, leaving more computation power on promising object-like regions. The features of each simple classifier are selected based on the Bhattacharyya distance. The cascade can be viewed as an object-specific focus-of-attention mechanism. Experimental results validate the effectiveness and rapidity of the proposed assessment method.

Video foreground object detection faces the problems of moving backgrounds, illumination changes, chaotic motion in real word applications. This paper presents a hybrid pixel-based background (HPB) model, which is constructed by single stable record and multi-layer astable records after initial learning. This HPB model can be used for background subtraction to extract objects precisely in various complex scenes. Using the multi-layer astable records, we also propose a homogeneous background subtraction that can detect the foreground object with less memory load. Based on the benchmark videos, the experimental results show that single stable and 3-layer multi-layer astable records can be enough for background model construction and are updated quickly to overcome the background variation. The proposed approach can improve the average error rates of foreground object detection up to 86% when comparing with the latest works. Furthermore, our method can achieve real-time analysis for complex scenes on personal computers and embedded platforms.

The classic template matching directly uses images as templates and correlation coefficients as the measure of matching degree. A novel template matching method for eye localization based on projection coefficient templates and nonlinear correlation is proposed. Unlike classic template matching, the projection coefficients on the basis function of the Karhunen-Loeve transform are used as templates, and the nonlinear correlation is proposed to measure the matching degree. The reduction of computation costs is achieved by taking advantage of the eye symmetry.

Most conventional fingerprint verifications use minutiae information as features. However, some fingerprints have many scratches that can make minutiae extraction quite difficult to capture with enough accuracy. This paper presents a new fingerprint verification system that can cover normal and scratched fingerprints and can be implemented on personal portable devices such as smartphones. The system separates those fingerprints with serious scratches and extracts the scratches as an additional matching feature, thereby expanding the number and type of fingerprints accepted by the application. A simplified gabor filtering technique enables embedded systems to provide real-time verification for scratched fingerprints. In an evaluation of a fingerprint test database, in which 25% of the fingerprints have scratches, the new verification system reduced the zero false acceptance rate (FARzero) by approximately 71% compared with the simple minutiae method. Furthermore, the new system expanded coverage and increased performance.

Here, we describe a novel approach for small surface object detection with an onboard infrared (IR) camera working in maritime scenes. First, we propose a simple but effective tool called the local minimum patterns (LMP), which are theoretically the approximated coefficients of some stationary wavelet transforms, for single image background estimation. Second, potential objects are segmented by an adaptive threshold estimated from the saliency map, which is obtained by background subtraction. Using the LMP based wavelet transforms and the histogram of the saliency map, the threshold can be automatically determined by singularity analysis. Next, we localize potential objects by our proposed fast clustering algorithm, which, compared with popular K-Means, is much faster and less sensitive to noises. To make the surveillance system more reliable, we finally discuss how to integrate multiple cues, such as scene geometry constraints and spatio-temporal context, into detections by Bayesian inference. The proposed method has shown to be both effective and efficient by our extensive experiments on some challenging data sets with a competitive performance over some state-of-the-art techniques.

We present a no-reference peak signal to noise ratio (PSNR) estimation algorithm based on discrete cosine transform (DCT) coefficient distributions from H.264/MPEG-4 part 10 advanced video codec (H.264/AVC) bitstreams. To estimate the PSNR of a compressed picture without the original picture on the decoder side, it is important to model the distribution of transform coefficients obtained from quantized coefficients accurately. Whereas several conventional algorithms use the Laplacian or Cauchy distribution to model the DCT coefficient distribution, the proposed algorithm uses a generalized Gaussian distribution. Pearson's χ² (chi-square) test was applied to show that the generalized Gaussian distribution is more appropriate than the other models for modeling the transform coefficients. The χ² test was also used to find optimum parameters for the generalized Gaussian model. It was found that the generalized Gaussian model improves the accuracy of the DCT coefficient distribution, thus reducing the mean squared error between the real and the estimated PSNR.

We propose a system that displays a three-dimensional (3D) scene on a 3D display device, consisting of a flat-panel display and a slanted parallax barrier, which can directly manipulate virtual 3D objects in real time. The proposed system consists of a 3D scene display part and a user interaction part. First, we propose a multi-view image interleaving method that considers the distance between a user and a display device for a slanted parallax barrier-based 3D display. Second, we define hand motion parameters for convenient hand motion analysis, and we propose a hand gesture recognition method that uses dynamic time warping (DTW) with specified hand motion parameters for user interaction. Thus, the proposed system makes it possible to see in any position, and viewers can perform event actions without regard to the shape or timing of hand motions.

When a transverse magnetic-polarized beam illuminates normally on an Ag grating mask with sub-wavelength slits, the surface plasmon (SP) interference patterns are formed on the Ag surface. According to the dispersion relationship of SPs, the wavelength of SPs (λsp) is tunable by altering the refractive index of the photoresist or the illumination wavelength. Various λsp form interference patterns with different size. The interference patterns are tunable using the same mask with period microns in size, which can save the cost of fabricating a different mask. This method will have potential applications to nanolithography.

We describe a method for controlling the spatial correlation width of a propagating Gaussian-Schell model (GSM) beam in an unknown turbulent atmosphere to optimize the scintillation index (SI). In our approach we slowly change a simulated GSM beam from incoherent to coherent by controlling the coherence through the spatial correlation width. The goal is to use statistics to determine the point just before a GSM beam becomes too coherent and starts to exhibit the statistics of a fully coherent source. We define this value of the spatial correlation width as the upper-coherence limit. We show that there is a straightforward method of calculating the upper-coherence limit in a closed channel regardless of turbulence strength or aperture size.

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