This PDF file contains the editorial “Editorial: Page Charges” for OE Vol. 44 Issue 03

A directly modulated AM-VSB cable-television transport system using negative dispersion fiber (NDF) as the transmission medium is proposed and successfully demonstrated. Good performances of carrier-to-noise radio, composite second order, and composite triple beat were obtained over a 70-km NDF transport without optical amplification. The directly modulated laser has a positive chirp, while NDF has a negative dispersion property in the transmission fiber. This negative dispersion property compensates for the laser chirp and results in a system with better transmission performance.

A new idea for a D-type optical fiber sensor based on Kretschmann's configuration is proposed. The sensing device is a D-type single mode fiber with a half-polished core, and a thin film layer of gold deposited on the flat side of the sensor. In order to achieve the best sensitivity of the D-type optical fiber sensor, we must choose suitable parameters, e.g., the thickness of the thin film layer of gold and the length of the sensor. We found that the experimental results are in good correspondence with theoretical results. The sensor's sensitivity can reach 2×10^–4 refractive index unit (RIU) at least. Because the sensor has some merits, e.g., small size, less costly, smaller sample volume, easy measurement, and suitability for in vivo testing, etc., the D-type optical fiber sensor is valuable for chemical, biological, and biochemical sensing.

A new method of developing fiber temperature sensors using a fiber Bragg grating-loop ringdown scheme is introduced. With this new technique, temperature measurements are converted to measuring time constants. Temperature sensing up to 593°C has been demonstrated using a proof-of-concept device. The sensor's stability, repeatability, sensitivity, and dynamic range are also explored.

A spatial integrator is an optical array characterized by a ray transfer matrix having a zero determinant. The design of a spatial integrator is explained using the relations among the geometric parameters of the array and the optical characteristics of its components. We focus our attention on spatial integrators constructed by using units composed of two thin lenses. The spatial integration does not depend on the focal length of the first lens. Although that focal length can be arbitrarily selected, we have found a range of its values that increases the amount of energy falling on the synthetic image and improves its uniformity. This analysis has been done for spatial integrator arrays having a spherical dome configuration and having a planar configuration. The study has been done both in the paraxial range and by using real ray-tracing tools. This optimization procedure is of interest in the design of spatial integrator arrays for illumination and natural lighting applications.

Progress in microelectronics has allowed the fabrication of optical gratings with small period-to-wavelength ratios, which are very useful in several applications, such as telecommunication and optical sensors. A rapid and nondestructive characterization process is essential to check the agreement of the produced with the expected structure. The main difficulty is in assuring sufficient homogeneity all along the grating surface. We show that neural characterization coupled with neural selection can be efficiently applied to this quality measurement. Depicted results concern a 1-µm-period grating fabricated by reactive ion etching on a silicon substrate.

The profile of the point spread function (PSF) in superresolution microscopy is studied theoretically. The fluorescence spot profile (i.e., the PSF) is determined by the focused beam patterns of the applied two-color lasers and the optical properties of the fluorescence-depletion process induced by the lasers (the pump and erase beams). In this study, the fluorescence-depletion process for the sample molecule is analyzed using a rate equation for a three-state model. Based on this result, we calculate the PSF for the case where the erase beam is modeled by a first-order Bessel function. In the case of an erase beam with a large photon flux, the obtained PSF has a Lorentzian-like shape, which seldom appears in traditional microscopy. In this work, we also investigated a possible relationship between the PSF and other parameters in the fluorescence-depletion process.

This paper presents a novel calibration approach for determining the mapping relationship between the depth map and the phase difference in fringe projection profilometry. This approach is based on a simple nonlinear function, which is deduced by analyzing the geometry of measurement system and hence perfectly describes the mapping between the depth map and the phase-difference distribution. The calibration is implemented by translating a target plane to a sequence of given positions with known depths, and measuring its phase distributions. A least-squares estimation algorithm with linear computation is deduced to retrieve the related parameters and to reconstruct the mapping function. Both computer simulation and experiment are carried out to demonstrate the validity of this technique.

The objective of profilometry is to obtain the topography of a surface. Some methods are based on the measurement of the slope of the test surface. Then, by integration the profile of a surface can be determined. The slope is measured in a given set of points and from these data it is necessary to obtain the profile with the highest possible accuracy. Most frequently, the integration is carried out by numerical integration methods that assume different kinds of polynomial approximation of data between sampling points. We propose the integration of the function by means of processing in the Fourier domain. The analysis of the different integration methods in the Fourier domain enables us to easily study and compare their performance.

Increasing resolution and lower costs of off-the-shelf digital cameras are giving rise to their utilization in traditional and new photogrammetric activities, such as transportation, surveillance, archeological, industrial, and medical applications. This progress is enabling amateur users to generate high-quality photogrammetric products using such cameras. For most, if not all photogrammetric applications, the internal metric characteristics, usually known as the interior orientation parameters (IOP), of the implemented camera must be determined and analyzed. The derivation of these parameters is usually achieved by implementing a bundle adjustment with a self-calibration procedure. The issue of camera stability has been rarely addressed when dealing with analog metric cameras, since they have been carefully designed and built to ensure the utmost stability of their internal characteristics. However, the stability of digital cameras must be investigated, since these cameras are not built with photogrammetric applications in mind. We introduce two quantitative methods for testing camera stability, where the degree of similarity between reconstructed bundles from two sets of IOP is evaluated. The stability of nine amateur and professional digital cameras are checked over 8 months. The experimental result depicts the stability of the majority of these cameras.

Polypeptide material layers can be used for different optical applications as diffractive optical elements or diffractive storage memory. The optical parameters of the polypeptide layers must be precisely known before implementing these applications. These optical parameters are the layer thickness, layer refractive index, and layer substrate refractive index. Thin film resonance (TFR) is one of the most adapted methods to evaluate the refractive index and the thickness of a homogenous photosensitive polypeptide layer. We restrict our method to transparent films layered on a transparent substrate. The proposed method is more convenient for layers having thicknesses greater than a few microns. The photosensitive material we consider is a polypeptide layer with thickness greater than 10 µm. The measurement of these optical parameters are provided separately. A low absorption of this layer is considered. We validate the possibility of easily measuring these parameters. The excellent agreement between the calculated and measured data confirms the practical efficiency of this method. This method is applied as an example to two standard holographic emulsions PFG-04 and PFG-03M for validation. After these tests, the method is applied to characterize the coated polypeptide layer elaborated in our laboratory. We analyze the measurements performed with our proposed method on four polypeptide layers prepared with different added quantities of doping agents. The main interest of our method is to allow the measurement of the layer and substrate refractive indexes (even when they are close) jointly with the layer thickness measurement just by using a simple setup based on monochromatic light as a source and an angular scanning.

This study presents a novel high-efficiency electro-optic (EO) light modulator whose operation is based on the attenuated total reflection effect, in which the surface plasmon wave is excited by an incident waveguide light wave. The EO light modulator is fabricated using a nonlinear optical polymer material that is a side-chain EO polyimide with 2-[N-ethyl-4-(tricyanovinyl)anilino]ethanol chromophore. The modulator is characterized, and its performance tested, in terms of the thickness and dielectric constant of the polymer thin film, the EO coefficient, the insertion loss, and the modulation index. Additionally, the dynamic response of the EO light modulator is fully investigated and discussed.

In stereoscopic or multiview 3-D display systems, the synthesis of intermediate sequences is essential to assure lookaround capability and continuous motion parallax so that it can enhance comfortable 3-D perception. The quadtree-based disparity estimation is one of the most popular methods for the synthesis of intermediate sequences, due to the simplicity of its algorithm and hardware implementation. We propose two solutions in order to reduce annoying flicker at object boundaries of synthesized intermediate sequences using quadtree-based disparity estimation. The first requires a new splitting scheme, providing more consistent quadtree splitting strategies during the disparity estimation. The second involves adaptive temporal smoothing, using the dissimilarity between the present frame and the previous one to reduce the error of disparity estimation. These two proposals are tested by using several stereoscopic sequences, and the results show that flicker is remarkably reduced by them.

Self-triggering pulsed laser ranging, a novel pulsed laser ranging method, can ease the trade-off between ranging precision and measurement speed in the traditional laser ranging technique. Theoretical analysis and system design for time-of-flight measurement, which determines both the ranging precision and the measuring speed of self-triggering pulsed laser ranging, is performed. An experiment on self-triggering pulsed laser ranging is reported, in which submillimeter (better than 0.5 mm) precision is achieved over a 20-m range.

We present a comprehensive review of work on the Er³⁺-doped tellurite glass microsphere laser. We discuss the optical properties of Er³⁺-doped tellurite glass, including the emission cross section, the absorption cross section, and the lifetime analysis. Whispering-gallery modes in microspheres and fiber-taper coupling schemes are described, and theoretical analysis is performed for optimization. Finally, lasing characteristics such as the threshold, the lasing wavelength, and the temperature dependence of the microsphere laser are analyzed. Microsphere lasers with different Er₂O₃ doping concentrations have been fabricated and examined. A state-of-the-art L-band microsphere laser with 124.5-µW maximum output power is demonstrated. These miniature microsphere lasers have great potential and have attracted considerable attention because of their versatility for signal processing, fiber communication, and photon computation, as well as laser stabilization and sensing applications.

We report on a computer-controlled pulse-shaper setup with high-efficiency throughput, based on dispersive prisms, as an alternative to the conventional grating ultrafast pulse-shaping apparatus. A detailed description of the experimental apparatus and operation of this system is given. The advantages and disadvantages of this configuration are discussed. Experimental implementation of the prism pulse shaper in recovering nearly bandwidth-limited laser pulses from chirped ultrafast laser pulses is demonstrated using both closed-loop and open-loop operation.

By considering the Gaussian spatial distribution of the intracavity photon density, we introduce the rate equations of a diode-pumped Nd:YVO₄ laser doubly Q-switched by an acousto-optic modulator and a Cr⁴⁺:YAG saturable absorber. These rate equations are solved numerically, and the dependences of pulse width on incident pump power at different pulse repetition rates are obtained. It is shown that the pulse width is obviously compressed in contrast to a diode-pumped actively Q-switched laser with an acousto-optic modulator and the numerical solutions are in agreement with the experimental results performed by a diode-pumped doubly Q-switched Nd:YVO₄ laser with acousto-optic Cr⁴⁺:YAG.

A comprehensive experimental study of a fiber optic relative humidity (RH) sensor is carried out in terms of characterization and performance optimization against various parameters that affect the sensor response and sensitivity e.g., film composition, film thickness, fiber core diameter, and the sensor geometry. The sensor is based on evanescent wave absorption spectroscopy and utilizes a specific reagent immobilized permeable polymer membrane cladding on a declad U-bend optical fiber. An optimum film thickness and an optimum film composition exist. In addition, a fiber with a smaller core diameter was observed to be more sensitive, unlike the previously reported results. The sensitivity further increases with a decrease in the bending radius. The sensor is found to be sensitive to RH ranging from ~1.6 to ~92%, exhibiting a very fast response time, an extremely good degree of reversibility, repeatability, and a large dynamic range.

A simple and practical method to simultaneously measure pressure and temperature using a double fiber Bragg grating (FBG) sensor is presented in which a double FBG is coated in a particular metal tube by a special polymer. In this manner, the inaccuracy induced by the mismatch of pressure and temperature sensitivity can be overcome effectively. The experimental results indicate that this scheme can measure pressure and temperature simultaneously. The temperature and pressure inaccuracy of sensors is about 0.5°C and 0.5 MPa, respectively, within the measuring range of 20 to 100°C and 0 to 20 MPa.

An application of mechanically created long-period fiber gratings as sensitive bend sensors in structures and other areas is suggested. A resonance splitting of about 10 nm is observed under a maximum bend curvature of 0.4 m^–1, producing a bend sensitivity of 25 nm/m^–1. The design features of the experimental setup developed for the realization of mechanically created long-period fiber gratings and measurement of their output spectrum under different bend curvatures are discussed.

We present details of the design and laboratory evaluation of the fiber Bragg grating (FBG) interrogation system developed specifically for condition monitoring of electrical submersible pumps (ESPs). The system, based on the microelectromechanical systems (MEMS) Fabry-Pérot tunable filter, is capable of interrogating several FBG sensors placed around an ESP unit and configured to measure static and dynamic parameters, e.g., temperature, vibration signature and/or instantaneous voltage, and current. Sensor interrogation over the extended step-out length distance of 24 km is demonstrated in the laboratory in a simple experiment of multipoint dynamic strain monitoring in a vibrated cantilever beam.

The intensity-voltage output characteristics of thin-film linear electro-optic Mach-Zehnder interferometer modulators can be nonperiodic for configurations where the optic axis is perpendicular to the applied electric field. As a result, the electro-optic coefficient for the material can not be determined assuming a periodic half-wave voltage. From the Jones matrix calculation, an analytic expression of the output intensity is derived in terms of the phase retardation. A method of determining the linear electro-optic coefficient is proposed based on the determination of the first intensity minimum in intensity-voltage characteristics. This method provides a simple expression for determining the electro-optic coefficient given values for the ordinary and extraordinary refractive indices, the modulator geometry, and the first half-period voltage. The first half-period voltage is found to be approximately inversely proportional to the square root of the electrode length. The method shows close agreement to the exact Jones matrix method for the case where the sum of the principal refractive indices in one arm of Mach-Zehnder interferometer is close to that of the other arm under an electric field.

Based on the Dormand-Prince (DP) formula, a fast and effective method is proposed, which can implement automatic step-size adjustment to solve the model equations of fiber Raman amplifiers and erbium-doped fiber amplifiers (EDFAs). Numerical results show that (1) the CPU time of the proposed method is about 4.2 times smaller than that of the DP method when the Raman amplifier propagation equations are solved; (2) our method reduces the running time by more than two orders of magnitude in comparison with the classical fourth-order Runge-Kutta method; (3) in comparison with the DP method, the proposed method can increase the computational speed by about 2.5 times in solving the model equations of EDFAs.

In a polarization-division multiplexing soliton system, the multiple soliton interactions are studied numerically, the effects of soliton interactions on timing jitter are analyzed, and a countermeasure using nonlinear gain to suppress the soliton interactions is developed with the help of computer modeling. It is found that the mutual interactions between neighboring solitons cause soliton transmission instability and lead to timing jitter. The interactions of more than two solitons are stronger than that of two solitons. Therefore, the maximum transmission distance limited by the soliton interactions should be inferred from the collision distance of multiple soliton interactions, not the mutual interactions of two solitons. Nonlinear gain combined with a filter is suggested to effectively suppress the soliton interactions and stabilize soliton propagation.

We report an all-optical module that performs simultaneous header separation and reinsertion in 10-Gbit/s short optical packets of variable payload length and that consists of two subunits. The first uses a Fabry-Perot filter and an ultrafast nonlinear interferometer (UNI) to perform packet clock recovery. The second is a UNI gate configured as a 2×2 exchange bypass switch that is optically controlled by the recovered clock packets. Using fixed delays, the data packets and the locally generated headers are fed into the 2×2 switch, where header replacement is achieved.

Optics is a candidate for digital communication and data processing where tremendous operational speed is the basic requirement. Conventional electronic systems cannot compete in this arena. Nonlinear optical materials may find important uses in optical switches. In this paper, a new idea for all-optical time-domain multiplexing and demultiplexing with the massive use of nonlinear optical materials is reported. The scheme exploits some special characteristics of such materials.

We have demonstrated three-dimensional optical data storage in a novel photochromic material with two-photon excitation. The data are read out with a homemade confocal fluorescence microscope combined with the three-dimensional writing system. Since the degree of destruction is closely related with the total dwell time of the readout laser, we try to read out the data through an optimization among the doped concentration of photochromic material of the PMMA film, the readout power, and the dwell time of the laser at each data bit. Using the optimized readout condition, it is possible to achieve 10⁷ readout cycles with very little erasure of the data at the scanning speed of a 50× CD driver.

The Hilger & Watts gauge-block interferometer was designed and manufactured commercially in the 1950s. The instrument uses isotope lamps as wavelength standards to perform absolute length calibration of gauge blocks (slip gauges) up to 100 mm in length, to an accuracy of approximately 1 ppm. It is entirely manually operated. In order to make the instrument more suitable for the modern laboratory, new hardware has been added, and a customized software package developed to automate the measurement process. This paper shows how interferograms may be imaged successfully at each of the eight available wavelengths, and the critical fringe fraction measurement automated, ensuring an accuracy better than ±0.05 fringe. To demonstrate the validity of the new system, representative data are presented alongside data obtained using the traditional method and from an external accredited laboratory.

We present a multiscale edge detection algorithm whose aim is to detect edges whatever their slope. Our work is based on a generalization of the Canny-Deriche filter, characterized by a more realistic edge than the traditional step shape edge. The filter impulse response is used to generate a multiscale edge detection scheme. For the merging of the edge information, we use a geometrical classifier developed in our laboratory. The segmentation system thus set up, after the training phase, does not require any adjustment or depend on any parameter. The main original property of this algorithm is that it leads to a binary edge image without any threshold setting. The quality of the results is inferior to that for classical multiscale merging approaches; nevertheless, this system, studied for real-time functioning, presents satisfactory performance for well-contrasted images and excellent performance for noisy images.

One of the most important problems to address when applying interferometric techniques to industrial applications is the prevalence of noise, which results in poor fringe patterns and thus poor measurements. One of the techniques that suffers most from this problem is conoscopic holography. Though this interferometric technique is ideal for industrial inspection, the poor quality of fringe patterns obtained in adverse environments may make measurement impossible. Classical filtering techniques based on one-dimensional filters or general speckle removal filters, such as the Frost or the gamma, may not suffice in adverse conditions. Therefore, a new approach, based on the nature of the fringe pattern information itself, is worth looking into. In this paper we propose the use of orientational filters to develop a filtering method that not only removes noise of any nature, but also enhances the fringe-pattern information. Several approaches to these algorithms are implemented and evaluated using synthetic conoscopic fringe patterns under different noise conditions, showing how they clearly outperform classical filters with negligible distortion even in the worst conditions. Examples with real data acquired with the latest prototype of a conoscopic long-standoff profilometer are also provided.

The effects of probe beam residual power in interferometry are investigated. It is seen that residual power produces an asymmetry between the forward and backward beams that is scaled with f²_#, i.e., the effect can be easily seen in very slow optical systems. Common methods to detect residual power are discussed, showing the effectiveness of lateral shear interferometry to carefully set the collimation of the probe beam. A device approaching the order of magnitude established by Rayleigh's quarter wavelength rule is demonstrated.

In general, inherent susceptibility to environmental noise has tended to retard adoption of interference methods by industry. Phase shifting is a key step in optical interference techniques of measurement. An improved max-min scanning (IMMS) method for phase determination was reported in 2004, but the environmental noise tolerance of this approach relative to other methods has been an open question. We discuss the noise tolerance of the IMMS method. Numerical simulations and simple experiments show that the method has good tolerance to some specific environmental vibration inputs, including high-frequency noise and small-amplitude low-frequency noise. The simplified data acquisition and improved noise tolerance of IMMS broadens potential applications of interferometry, particularly digital speckle pattern interferometry in the factory and the field. Another benefit of the IMMS method is an online technique to calibrate and test the phase shifter in real time. This idea is described and demonstrated.

In February 2000, the Shuttle Radar Topography Mission (SRTM) mapped large areas of the global landmass using two radar systems operating simultaneously in X and C band. The radar mapping instrument consisted of modified versions of the SIR-C C-band and X-band radars flown on the shuttle in 1994. Modifications included a 60-m retractable boom, with C-band and X-band receive-only antennas attached to the boom's end. High-accuracy metrology systems were added to measure position and attitude of the shuttle and the positions of the boom antennas. The dual apertures at each band form radar interferometers suitable for making high-accuracy topographic maps of the Earth. The C-band data set is being processed by JPL for the archives of the National Imagery and Mapping Agency and the National Aeronautics and Space Administration. The X-band data set is processed and distributed at DLR, Germany. This paper deals with the accuracy assessments of the interferometric DEMs derived from the X- and C-band synthetic aperture radar systems over a testfield with rolling topography and moderate forest cover using the reference DEM digitized from the topographic maps of 1:25,000 scale. Obtained results for the two interferometric DEMs are similar and lie in the range of 10–11 m. The accuracy of SRTM X- and C-band DEMs was also checked against ground control points measured by differential GPS, and the rms height errors were found to be about 9 m, which confirms the results based on the reference DEM.

Experimental data are presented on the bidirectional reflectance distribution function and 8-deg directional-hemispherical reflectance measurements of a Martian regolith simulant, JSC Mars-1. The scatterometer located in the National Aeronautics and Space Administration's Goddard Space Flight Center Diffuser Calibration Facility was used for the measurements reported. The data were obtained with a monochromator-based light source in the ultraviolet, visible, and near infrared spectral regions. The measurements were performed at different angles of incidence and over a range of in-plane and out-of-plane scattered geometries. The results presented are traceable to the National Institute of Standards and Technology. The hemispherical and diffuse scattering data obtained from these studies are important for current and future Mars space- and ground-based observations.

This paper presents a new automatic target detection (ATD) algorithm to detect targets such as battle tanks and armored personal carriers in ground-to-ground scenarios. Whereas most ATD algorithms were developed for forward-looking infrared (FLIR) images, we have developed an ATD algorithm for charge-coupled device (CCD) images, which have superior quality to FLIR images in daylight. The proposed algorithm uses fast binary template matching with an adaptive binarization, which is robust to various light conditions in CCD images and saves computation time. Experimental results show that the proposed method has good detection performance.

Wavelength tuning is demonstrated in an antenna-coupled infrared microbolometer. With a 300-mV control voltage, we observed a tuning range of 0.5 µm near 10 µm. A metal-oxide-semiconductor capacitor underneath the antenna arms causes the shift of resonance wavelength with applied voltage. We develop a device model that agrees well with measured results.

Quantum-well infrared photodetectors (QWIPs) are trapping-mode photodetectors, and it is trapping that leads to an inherent problem: QWIPs' responsivity can be background-dependent under low-background conditions. We have determined that the source of the dependence is a relaxation process due solely to dielectric effects (dielectric relaxation), which results in a long time constant for recovery to steady state after a pulse of radiation is detected. We have analyzed responsivity-versus-frequency measurements on QWIPs published separately by Arrington et al. We have determined the value of the background flux for which significant background dependence occurs. For a given sensor integration time τ_i (frame time for a staring sensor, dwell time for a scanning sensor), we calculated the response as a function of an exponential time constant. Fitting the calculated response to the measured data, we extracted values for the exponential time constant. We then determined the lower bound of background flux, Φ_BL, above which the total responsivity will be less than 1% background-dependent. The value of Φ_BL for a typical QWIP detector is such that Φ_BLτ_i lies between 10¹² and 10¹³ photons cm^–2. Practically, when significant background dependence occurs, it is essentially impossible to calibrate a QWIP-based focal plane array. And this, together with their the inherently low sensitivity and low required operating temperature (compared with HgCdTe detectors), makes QWIPs a poor choice for many low-background spaceborne sensors.

A model-based texture recognition system that classifies image textures seen from different distances and under different illumination directions is presented. The system works on the basis of a surface model obtained by means of four-source color photometric stereo (CPS), used to generate 2-D image textures as they would have appeared if imaged under different imaging geometries. The proposed recognition system combines cooccurrence matrices for feature extraction with a nearest neighbor classifier. The use of the cooccurrence matrices instead of filtering methods for feature extraction allows us to utilize only pixels for which valid information has been extracted by CPS. The validity of the method is demonstrated by classifying texture images captured under different imaging geometries than the reference images in the database. Moreover, the process of recognition allows one to guess the approximate direction of the illumination used to capture the test image.

A parallelized random iteration algorithm that is explicit in the iterated function system (IFS) code is proposed to speed up the decoding of fractal images. In a conventional random iteration algorithm, the fractal image is serially decoded and may generate undesirable transient points. The proposed intrinsic parallel random iteration (IPRI) algorithm determines only one initial point and can avoid the transient points. Moreover, the contractive affine transformations (CATs) denoted by the IFS code can operate in parallel and simultaneously generate subimages. The parallel capability is basically proportional to the number of CATs. Two generalized methods of the proposed IPRI algorithm are provided to solve the nonuniformity problem due to the unequal probabilities among CATs. Finally, the proposed IPRI algorithm can cooperate with a previous parallel decoding algorithm to obtain higher parallel capability. Simulation results demonstrate the validity of the proposed IPRI algorithm.

Of the many image fusion methods, the discrete wavelet transform (DWT) and various pyramids (e.g., the Laplacian pyramid) are among the most common and effective. For quantitative evaluation of the quality of fused imagery, the root mean square error (RMSE) is the most reasonable measure of quality if a "ground truth" image is available; otherwise, the entropy, spatial frequency, or image quality index (IQI) can be calculated and evaluated. Here, an advanced discrete wavelet transform (aDWT) method that incorporates principal component analysis (PCA) and morphological processing into a regular DWT fusion algorithm is presented. Specifically, a principle vector is derived from two input images and then applied to two of the images' approximation coefficients at the highest DWT transform scale. For the detail coefficients at each transform scale, the larger absolute values are chosen and subjected to a neighborhood morphological processing procedure that serves to verify the selected pixels by using a "filling" and "cleaning" operation. Furthermore, the aDWT has two adjustable parameters—the number of DWT decomposition levels and the length of the selected wavelet that determinately affect the fusion result. An iterative fusion process that was optimized with the established metric—IQI—is then implemented. Experimental results tested on four types of inhomogeneous imagery show that the iterative aDWT achieves the best fusion compared to the pyramid or the DWT methods judged on both the IQI metric and visual inspection.

We present a novel, computationally efficient and robust scheme for multiple-initial-point predictors used in fast searches in the MPEG-2 standard. Extensive testing in a variety of video sequences with different motion characteristics clearly shows that it outperforms the center- and median-based predictors currently used by mean square error (MSE) reduction of 1.51, 5.25, and 3.62% for the diamond, the three-step, and the four-step searches and for the same bit rates as the standard.

Superresolution image reconstruction produces a high-resolution image from a set of shifted, blurred, and decimated versions thereof. Previously published techniques perform well only for small magnifications but get worse either in computational complexity or ringing artifacts for large magnifications. We propose a hybrid algorithm to reduce both ringing artifacts and computational complexity of maximum a posteriori (MAP)-based superresolution algorithms. The proposed algorithm magnifies the low-resolution image in stages, and applies a new edge-adaptive postprocessing algorithm at early stages. Experiment results show that the new approach is more efficient and can provide much better reconstruction quality in comparison with normal MAP algorithms.

One of the most important challenges of fingerprint identification is the extraction of relevant details against distributed complex features. The parallel processing capability and learnable filtering features of cellular neural networks offer highly efficient feature extraction and enhancement capability for fingerprint images. In this paper, we propose to utilize the Widrow learning algorithm with a cellular neural network to efficiently enhance fingerprint details during the enrollment part. To evaluate the performance of the verification-identification part, enhanced fingerprint images are introduced into the fringe-adjusted joint transform correlator architecture for verification of an unknown fingerprint from a database. Comparison between the original and enhanced fingerprint identification and verification results is provided through computer simulation.