This PDF file contains the editorial “2006 in Review” for OE Vol. 46 Issue 02

We proposed the multipolar inserting zeros (MIZ) code for direct-sequence optical code division multiple access (OCDMA) systems. This code is designed to correspond with the judgment based on linear convolution. Simulation results showed that it can provide a lower multiuser interference than the conventional Gold sequence. With the same number of users, the bit error rate in the OCDMA system coded by MIZ can be reduced by several decuples than that coded by Gold, and the source power needed to reach a BER of 1×10^-9 can also be reduced by several decibels. So the performance of OCDMA can be improved.

Recent studies show that wavelet-based image fusion methods provide a high spectral quality in fused satellite images. However, images fused by most wavelet-based methods have less spatial resolution because the critical downsampling is included in the wavelet transform. We propose a useful fusion method based on contourlet and local average gradient (LAG) for multispectral and panchromatic satellite images. Contourlet represents edges and texture better than wavelet. Because edges and texture are fundamental in image representation, enhancing them is an effective means of enhancing spatial resolution. Based on LAG, the proposed fusion method reduces the spectral distortion of the fused image further. Experimental results show that the proposed fusion method is able to increase the spatial resolution and reduce the spectral distortion of the fused image at the same time.

The visual-resolution characteristics of an array, comprising many elemental afocal optical units, for an optical viewer are investigated. First, it is confirmed by wave optics that lightwaves exiting the array will converge, forming a three-dimensional optical image. Next, it is shown that the convergence point and resolution characteristics depend on the angular magnification of the afocal unit. When the magnification is 1.0, the lightwaves focus on the convergence point, and the resolution characteristics depend only on the diffraction of the afocal units. At magnifications other than 1.0, the lightwaves do not focus on the convergence point, decreasing the resolution as a result. To clarify this result quantitatively, we determined the viewing distances at which the alignment of the afocal units is not perceptible when an optical image formed by the array is viewed by an observer, and we calculated the modulation transfer functions normalized by the viewing distance.

We present the design of an imaging fiber bundle lens that consists of an objective lens and a coupling lens. The objective lens has an operating wavelength of 0.4 to 0.7 μm, a field of view of 60 deg, and an outer diameter of 9.5 mm. The coupling lens has an operating wavelength of 0.4 to 0.7 μm, a field of view of 6 mm, and an outer diameter of 7.7 mm. The imaging quality of an imaging fiber bundle lens has been experimentally demonstrated.

Photosensitive ZrO₂/BzAc gel films on silicon and quartz substrates with chelate complexes as precursors are fabricated using the sol-gel method. The characteristics of UV and IR spectra of the photosensitive gel films, and their variations in the process of laser irradiation and heat treatment, are investigated. Given different incident angles, the gratings with different pitches are fabricated by interference of two coherent beams of a 325-nm He-Cd laser in ZrO₂/BzAc photosensitive gel films, which are exposed to the interference fringe after laser irradiation and leached in ethanol. Subsequently, the optical resolution is also investigated. The minimum pitch of the grating obtained from the experiment is 300 nm. After being heat treated at 600°C, the organism is volatilized and the gel film grating turns into an inorganic film grating, which can combine with the substrates firmly. The x-ray diffraction (XRD) result shows that inorganic films mainly consist of polycrystalline tetragonal ZrO₂.

Laser-induced damage threshold (LIDT) results on silica substrates and coatings are presented for near-infrared applications. Different polishing and cleaning processes are evaluated. In particular, we investigate the influence of polishing and cleaning on the LIDT of silica substrates and optical coatings deposited by dual-ion-beam sputtering. Laser damage tests were performed at 1064 nm with a 5-ns-pulse Nd:YAG laser, and experiments were made on surfaces of optical components using a 12-μm-diameter focused beam. Accurate damage probability curves are plotted thanks to a reliable statistical measurement of laser damage. Use of a statistical model permits us to deduce the densities of laser damage precursors. We find a significant improvement of the LIDT of our coatings on choosing the appropriate cleaning and polishing process.

A novel calibration method for whole field three-dimensional shape measurement by means of fringe projection is presented. Standard calibration techniques, polynomial-and model-based, have practical limitations such as the difficulty of measuring large fields of view, the need to use precise z stages, and bad calibration results due to inaccurate calibration points. The proposed calibration procedure is a mixture of the two main standard techniques, sharing their benefits and avoiding their main problems. In the proposed method, an absolute phase is projected over marked planes placed at unknown positions. The corresponding absolute phase and marks positions are recovered for each plane location. Using Zhang's calibration method, internal camera parameters (also called intrinsic parameters) and the spatial position for each plane are computed. Later on, a polynomial fit of depth with respect to the phase is performed. To obtain the absolute position of an object point, the depth coordinate is obtained by means of the polynomial calibration and its absolute phase. Then the lateral coordinates are computed from the depth, the internal parameters, and the pixel coordinates of the imaged point. Experimental results comparing the proposed method with the standard polynomial-based calibration are shown, demonstrating the feasibility of the proposed technique.

Precise manufacturing of optical flats requires precise characterization of the surface. A scanning pentaprism system is ideal for use as an absolute and precise test for an optical flat. Such a system was built and used to test a 2-m diameter flat mirror. This system uses light from an autocollimator that is reflected from two pentaprisms to project reference beams of light onto the flat mirror. The light reflected from the mirror back through the pentaprisms provides information on low order optical aberrations in the flat mirror. We report results of the test on a 2-m flat, characterizing the errors and their sources. There is enormous potential for our system to be used to test larger flats and even curved surfaces, made of either a glass or a liquid.

Modern table-top laser systems are capable of generating ultrashort optical pulses with sufficiently high intensity to induce nonlinear optical effects in many of the materials that are used in the construction of optical components. We discuss the interaction of such pulses with three types of dielectric filters: (a) dielectric stacks composed of a sequence of two dielectric layers with quarterwave optical thickness, (b) idealized rugate filters, i.e., filters with a refractive index profile that is sinusoidally modulated on the length scale of an optical wavelength, and (c) a rugate filter composed of two materials. We present finite difference time-domain (FDTD) computer simulations of optical pulse propagation through dielectric filters for pulses with widths in the range 5 to 100 fs and with peak intensities up to 10 TW/cm². At low intensities the reflective properties of the dielectric filters determined using FDTD simulations are directly comparable to the results calculated using the characteristic matrix method, while at high intensities optical nonlinearity in the dielectric layers is responsible for a decrease in the reflectance of the filter and causes stretching and distortion of the reflected pulses.

Two complex multilayer thin-film filters have been produced by reactive e-beam evaporation. The filter specifications were challenging with respect to design and manufacturing. The optimized design configurations of 29- and 44-layer structures for the two filters, based on TiO₂ and SiO₂ as high- and low-index materials, have been finalized. The total thickness for the 29-layer filter is 2.1 μm and for the 44-layer filter is 4.1 μm. The deposition conditions and optical parameters of the material used were optimized and the films were characterized using spectrophotometry, atomic force microscopy, x-ray diffraction, and scanning electron microscopy, prior to manufacturing of multilayer structures. The multilayer structures are also characterized using the same techniques. Extremely good spectral performance, matching design specifications, has been achieved for the two filters, with compact and smooth film surfaces and dense structure. Both filters have been subjected to optical and structural characterization, and the results are discussed. The multilayer filters also passed the standard tape test to show good adhesion of the films to the substrate. The performance of the prepared filter samples are comparable with similar characteristic samples prepared by more energetic techniques like sputtering.

Double phase conjugation (DPC) of two nearly opposite light waves has been theoretically and experimentally studied in a nematic liquid crystal with thermal optical nonlinearity. A model for wave coupling in the material with thermal nonlinearity has been analyzed for the DPC threshold conditions. DPC of two mutually incoherent laser beams has been demonstrated in a nematic liquid crystal (NLC) multilayer structure in good agreement with the model. An all-optical beam tracker consisting of such a structure has been built and demonstrated to compensate for beam/reflector jitter.

A variable-focus liquid-filled optical lens comprises a membrane and a support frame (which consists of a chamber and a liquid channel). The optical properties of different variable-focus liquid-filled optical lenses are studied to obtain the best membrane shape. The non linear finite element method is employed to shed light on the deformation of membranes under different liquid pressures. With the information thus obtained, the optical properties (such as the focal length and image diagram) of the lens are examined. The focal length of a lens with a flat membrane shape is studied by both simulation and experimental analyses, and the two results obtained are in good agreement. The deformations of membranes show that the bending moment and the boundary conditions of the membrane are two important parameters. Finally, several membranes of different shapes are examined to obtain the membrane shape with the best optical performance.

We describe a technique for the adjustment and control of repetition rates in continuous-wave-pumped, passively Q-switched solid-state lasers. The method uses a movable intracavity lens to modify the mode matching and hence the gain of the laser beam per pass. The technique was applied to a diode-pumped Nd3+:YVO4 laser passively Q-switched with a Cr4+:YAG saturable absorber at 1064 nm. At a fixed pump power of 5.4 W, we were able to continuously adjust the repetition rate between 13.8 and 25 kHz by translating an intracavity converging lens. We also demonstrate that by adjusting the lens position, the repetition rate can be kept at a desired value as the pump power varies. In particular, as the pump power was increased from 3.95 to 5.9 W, the lens position was varied by 0.91 cm to keep the repetition rate constant at 13.8 kHz. Rate-equation formalism was used to investigate the variation of the repetition rate as a function of lens position, and very good agreement was obtained between experiment and theory.

This study develops a scanning laser Doppler microscope (LDM) to measure the velocity flow profile within a capillary. The flow velocity is established by detecting the periodic fluctuation in the scattered light as the microspheres pass through a measurement volume with a diameter of 15 μm. Using a programmable positioning stage, the position of the capillary relative to the focal point is shifted incrementally in the x- and y-axis directions, respectively, such that the velocity flow profiles in the X-X′ and Y-Y′ directions can be obtained. During scanning, the required stage displacements in the x- and y-axis directions are calculated using an analytical model that compensates for deviations in the focal point position caused by the mismatched refractive index effect. The velocity–flow rate relationship within a capillary with an internal diameter of 75 μm is characterized and is found to be in good agreement with the theoretical prediction [correlation coefficient (R2): 0.998]. Additionally, the measured velocity flow profiles in the X-X′ and Y-Y′ directions are in good agreement with the analytical results obtained from the Navier-Stokes equation. The scanning LDM provides a powerful technique for characterizing microfluidic flow fields in the cross section of micro-electro-mechanical systems–based biochips and similar advanced applications.

Based on beam deflection technique, an air-coupled laser acoustic detector was developed to investigate the Scholte waves excited thermoelastically by Nd:YAG laser pulse action on the air-solid interfaces. By experimental measurements, we obtained the waveforms of Scholte waves at the air-aluminum, air-copper, and air-steel interfaces. According to the waveforms detected at different positions, the velocity of Scholte waves was calculated, which is a little slower than sound velocity in air. The results are then compared with theoretical prediction and are well matched with each other. Moreover, the attenuations of Scholte waves were also measured while propagating along the three interfaces. The results show that the attenuations could be negligible. Last, the interactions of laser-induced Scholte waves and surface defect are also discussed.

Curvature of a multimode optical fiber reduces the numerical aperture and induces radiation losses. We study this phenomenon and we present the "model disadaptation" method to calculate the local numerical aperture and the power attenuation. We exploit the bending effect on the local numerical aperture to propose a new intrinsic optical fiber temperature sensor. The modeling results are experimentally validated for two kinds of optical fibers: a silica-silicone optical fiber and a silica-polymer optical fiber. The simulation and the experimental results are in good accordance and show that the silica-silicone optical fiber sensor can operate between −60 and 152°C with a good response. The silica-polymer optical fiber temperature sensor can sense the temperatures between −249 and 83°C with a good response.

An integrated-optic wavelength demultiplexer produced by double proton exchange on z-cut lithium niobate is demonstrated. The mode sorting effect and waveguide dispersion characteristics are utilized to demultiplex the optical fields at the wavelengths 980 nm and 1550 nm. The opposite waveguide dispersion in the two output waveguides can be obtained by designing the aspect ratio of the waveguide structure and the refractive index profile of the waveguide. The design parameters include the waveguide width, the proton-exchange time, the annealing time, and the depth of the second proton-exchanged layer. The semivectorial finite difference method is utilized to calculate the effective index of the guided mode in the output waveguide in order to obtain the required waveguide dispersion for wavelength demultiplexing. In the experiment, the effects of waveguide width, branching angle, and depth of the second proton-exchanged layer on the device performance are discussed.

To produce long and flexible hollow optical fibers for mid-infrared lasers at a low cost, hollow fibers are fabricated by using a glass drawing technique. When the wall thickness of the glass tube is properly designed and controlled, the fiber shows a low loss at a desired wavelength. By applying pressure into the tube preform, the glass capillary with a thin glass wall is drawn, and this effectively reduces the absorption loss in the glass material. The measured loss of 40-cm long fiber with an inner diameter of 320 μm is 1.7 dB for an erbium: yttrium aluminum garnet laser light with a wavelength of 2.94 μm.

Priority-based alternate routing (PAR) and dynamic priority-based alternate routing (DPAR) are introduced for multiple classes of traffic in intelligent optical networks. A discrete event simulation platform was implemented to compare the performance of different priority schemes. As usual, the call interarrival and holding time for each class of traffic were assumed to be exponentially distributed in the simulation. The results show that PAR can significantly decrease the blocking probability of optical networks, especially for traffic with low priority. Because the weights of links of the network in DPAR increase with the increment of wavelength occupation, links with more idle wavelengths are more easily chosen as part of the shortest path. This mechanism benefits to the load balance of the network and as a result, DPAR has better performance than PAR. In order to utilize the advantage of the wavelength reservation-based priority scheme (RES), which provides low blocking for traffic with high priority, the combination of DPAR and RES was also investigated. The simulation results show that DPAR with the proper RES provides the lowest blocking probability for every class of service compared to the corresponding class of other priority schemes.

In optical communications through the atmosphere, the evaluation of a link feasibility often requires the quantification of the scintillation penalty in terms of power loss. To find how much additional optical power is needed to reach the bit-error-rate (BER) requirements, the optical-power fluctuations must be characterized as well as the response of the receiver to those fluctuations. In the present analysis, the direct-detected optical power is assumed to be either lognormal or gamma-gamma distributed. To account for the dynamics of the atmospheric channel, a distinction is made between short-term and long-term BERs. For a simple On-Off Keying (OOK) modulation, expressions of scintillation losses are given for different system requirements. Specifically, an upper bound is set to any of the three following quantities: the long-term BER, the probability of having a too-high short-term BER, or the mean time during which the short-term BER is too high. Results show that, without any fade mitigation, losses under moderate scintillation are considerable. Finally, a simple code-word approach shows how scintillation losses can be reduced by channel coding.

Optical layer multicast refers to the support of point-to-multipoint connections directly at the physical layer by employing passive devices known as power splitters. Since the bandwidth requirement of an individual user is only a fraction of optical channel capacity, traffic grooming problems are becoming a crucial constituent in designing wavelength-division-multiplexing (WDM) networks. This work proposes a new efficient multicast traffic grooming algorithm (EMGA) in the dynamic scenario based on an auxiliary grooming graph. The layered auxiliary graph represents the current network resource state and is modified adaptively, based on which multicast routing and wavelength assignment can be realized at the same time. Simulation results show that, under different network loads, the EMGA has lower traffic blocking probability and good network resource utilization with the constraints of wavelength continuity, and limited wavelengths and transceivers.

All-optical 40-Gbit/s tunable wavelength down- and up-conversions are simultaneously observed by exploiting cascaded sum- and difference-frequency generation (cSFG/DFG) in a periodically poled LiNbO₃ (PPLN) waveguide. With signal and pump-1 wavelengths kept at 1549.7 and 1536.6 nm, the converted idler wavelength can be tuned from 1531.9 to 1556.8 nm as the pump-2 wavelength is changed from 1554.5 to 1529.8 nm, covering a total 24.9-nm conversion span. It is interesting to find that the single-to-dual channel wavelength conversion can be potentially implemented by setting the pump-2 wavelength close to the signal or pump-1 wavelength.

A loadable and erasable fiber loop optical buffer based on a semiconductor optical amplifier (SOA) is presented. Two SOAs in our configuration not only provide nonlinear phase shift to implement buffer function, but also compensate for the propagation attenuation during long time storage. In particular, we present a simplified model to investigate the influence of background noise to the optical buffer performance. Both theoretical and experimental results reveal that the background noise can be suppressed by intentionally increasing the fiber loop loss. We also demonstrate that the packet pattern is well maintained after a storage time of 145 μs without self-oscillation.

Based on wavelet transformation and adaptive Wiener filtering, a new method was presented by the authors to perform synchronization and detection of binary data from a free-space optical (FSO) signal. It was shown prevlously that the Haar wavelet with a fixed scale is an excellent choice for this purpose. The output of the filter was zero mean and was closely related to the derivative of the binary data. In this effort, an analysis of the prior work is presented to obtain the probability of bit error using a Bayesian ternary hypotheses testing. The analysis also results in determining optimum thresholds for the detection of binary data. Simulation experiments are performed and presented to validate the results of the theoretical analysis.

We report what to our knowledge is the first theoretical prediction of the efficiency of coupling of a laser diode to an elliptic-core single-mode step-index fiber via a hyperbolic lens on the tip of the fiber. Based on the formulated ABCD matrix for refraction under paraxial approximation, we present analytical expressions for such coupling efficiencies and evaluate them, involving very little computation. Elliptic-core single-mode fibers have already attracted a great deal of attention for their applications in the conservation of polarizations, and so this analysis will be extremely important in coherent optical communications, fiber optic sensors, etc. In addition, if due to constructional problems there is noncircularity in a circular core fiber, such analysis will take care of the resulting noncircularity in the process of designing optimum launch optics.

In wavelength-division-multiplexing optical networks, the fiber links may share some common physical resources (e.g., cables, conduits), and the consequence is that they have a correlated link failure probability (CLFP), which means that the probability that link l will fail depends on whether link f has failed. Based on CLFP, we propose a new heuristic survivable algorithm, called differentiated path-shared protection (DPSP), to protect against double-link failures in WDM optical networks. In DPSP, each connection request can be assigned one working path and additional backup paths according to the differentiated reliability requirements of users. Compared to previous work, DPSP can obtain better performances in resource utilization ratio and blocking probability.

Despite the presence of finite differential group delay leading to polarization mode dispersion (PMD), pulse narrowing occurs in fibers when polarization-dependent loss (PDL) is also present. PMD and PDL in fiber may lead to interference during pulse propagation, in turn reducing the width of propagating pulses. This reduction depends in addition on the state of polarization in which the input light is launched. Equations representing the output power of the pulse are derived for different cases of input states of polarization in terms of PMD and PDL. The effective pulse width difference calculated from these equations indicates that the pulse narrowing is prominent for a PMD of 30 ps, a PDL of 3.5, and an input pulse width of 100 ps in different states of polarization for a PDL element sandwiched between two PMD elements.

Based on silicon-on-insulator (SOI) technology, a Mach-Zehnder interferometer (MZI) is fabricated, in which two directional couplers serve as power splitter and combiner. The free carrier plasma dispersion effect of Si is adopted to achieve the phase modulation and the consequent intensity modulation of optical fields. The device presents an insertion loss of 2.61 dB and an extinction ratio of 19.6 dB. The rise time and fall time are 676 ns and 552 ns, respectively. Detailed analysis and explanation of the performance behaviors are also presented.

A technique for deformation measurement by carrier is presented, which is based on large image-shearing shearography. A reference object is fixed on the side of a test object. They are all illuminated by one expanded laser beam. When a large image-shearing Wollaston crystal is used in front of a charge-coupled device (CCD) camera, one image of the object is superposed by one image of the reference surface. The carrier can be introduced by tilting the reference surface at a small angle. When Fourier transform is used to demodulate the modulated fringe pattern, the phase of deformation can be calculated and the deformation can be measured accurately. The principle of spatial carrier frequency modulation in large-shearing electronic speckle pattern interferometry (ESPI) is discussed. A typical experiment using a centrally loaded clamped circular plate is completed. Some experimental results are presented. The experimental results prove that the method can modulate a speckle pattern very well and the displacement fields can be measured effectively.

In phase-shifting digital holographic interferometry for measuring the displacement distribution of an object, holograms and reconstructed images have speckle noise, and they cause large errors in the calculation of the displacement analysis. In order to reduce the effect of speckle noise and hence to increase the sensitivity of the measurement of the displacement, we previously proposed a method using windowed holograms. In this paper, we propose a new method for averaging the obtained phase-difference values. Many phase-difference values at a point of the reconstructed image obtained with different windows for a hologram are averaged with weights. In order to check the effect on accuracy, the number n of windows used for averaging is varied. The weight, which is the m'th power of the absolute value of the complex amplitude of the reconstructed object, is also varied. As a result, when n becomes larger, the standard deviation of the errors becomes smaller. When the power m is 2, the error becomes a minimum. The standard deviation of the errors in the case of a flat plate with 316-nm out-of-plane displacement is 88 pm when n=1024 and m=2.

Dot-matrix holograms created by two-beam writers usually contain grating-dot position errors. The position errors may result from lens aberrations, rotation mechanisms, or beam direction inaccuracy, so they are not controllable. When the components of a two-beam writer are not reinstalled, the position errors of the grating dots created by the writer can be reproduced. Hence, position-error curves derived from the regression of the data points on position-error diagrams have some high-end applications. Two applications of position-error curves of dot-matrix holograms are proposed. The first application is to determine whether a dot-matrix hologram was created by a specified two-beam writer or not. The second application is to determine if two dot-matrix holograms were created by the same two-beam writer with the same component installation.

A method of encoding computer-generated holograms, which is matched to the recently developed one-step phase retrieval (OSPR) algorithm, is described. Continuous amplitude and binary phase modulators are coupled to enable the encoding of the entire Fourier plane real axis, and an implementation using commonly available reflective and transmissive devices is described. It is shown that, if a binary phase spatial light modulator (SLM), employing high switching angle liquid crystal (LC) material, is deployed in such a coupled modulator arrangement, the resultant reconstructed images exhibit signal-to-noise ratios some 3.5 and 15 times greater than those currently achievable with continuous and binary phase modulation, respectively.

This paper describes the realization of the wind lidar data acquisition system, and a method of denoising signal based on empirical mode decomposition (EMD). The paper proposes a method for raveling out the edge problem that comes with EMD. It has been proved to be a good method for solving the edge problem in analyzing lidar data. We can improve the ratio of signal to noise by using the EMD method three times more than the original's. It has been proved to be better than adjacent averaging in data processing.

Infrared satellite sensors must be recalibrated in orbit using blackbodies small and light enough to fit on spacecraft. Emissivities very close to one can be achieved by observing closed interiors along rays making multiple reflections off surfaces that are both highly absorbing and specularly reflective. We analyze the effect of slightly nonideal specularly reflective surfaces having a small but finite diffuse reflectivity, showing how it limits the performance of a three-reflection specular blackbody.

The retardation change versus temperature was measured for deep UV multiorder crystal quartz wave plates. The influence of temperature on the wave-plate performance is even more significant for the deep UV region due to the shorter wavelength and increased number of wave periods in the retarder for the given thickness and sharp changes of refractive indices versus temperature and wavelength? Precise control of temperature is needed for accurate analysis of the wave-plate optical parameters. The wave plate should be designed for a certain temperature and used within a tightly controlled temperature range; otherwise its performance will be degraded, affecting the entire optical system. A simple laser-based method was exploited and developed for wave-plate performance evaluation versus temperature for the half and quarter wave retardation. All this information needs to be taken into account for deep UV wave-plate design to ensure the best possible performance of the retarder.

In a flash x-ray generator, a 150-nF condenser is charged up to 80 kV by a power supply, and flash x-rays are produced by the discharge. The x-ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. Because bremsstrahlung rays are not emitted in the opposite direction of that of electron trajectory, clean molybdenum K-series characteristic x-rays can be produced without using a filter. When the charging voltage is increased, the K-series characteristic x-ray intensities of molybdenum increase. The K lines are clean and intense, and hardly any bremsstrahlung rays are detected. The x-ray pulse widths are approximately 100 ns, and the time-integrated x-ray intensity has a value of approximately 500 µGy per pulse at 1.0 m from the x-ray source, with a charging voltage of 80 kV.

A microfocus x-ray tube is useful to perform magnification digital radiography, including phase-contrast effects. The 100-m-focus x-ray generator consists of a main controller for regulating the tube voltage and current, and a tube unit with a high-voltage circuit and a fixed anode x-ray tube. The maximum tube voltage, current, and electric power are 105 kV, 0.5 mA, and 50 W, respectively. Using a 3-mm-thick aluminum filter, the x-ray intensity is 26.0 Gy/s at 1.0 m from the source, with a tube voltage of 60 kV and a current of 0.50 mA. Because the peak photon energy is approximately 35 keV using the filter with a tube voltage of 60 kV, the bremsstrahlung x-rays are absorbed effectively by iodine-based contrast media with an iodine K-edge of 33.2 keV. Magnification angiography is performed by three-fold magnification imaging with a computed radiography sys-tem using iodine-based microspheres 15 m in diameter. In angiography of nonliving animals, we observe fine blood vessels approximately 100 m with high contrasts.

A new false color image fusion method is proposed on the basis of Land's experiment on color constancy of human vision, through idealized hypothesis of the red filter and green filter, through equienergy distribution hypothesis of the light source, and by relating the infrared and visual images to the black-and-white transparencies obtained through the red and green filters of Land's experiment, respectively. The normalization of each color channel conforms with the von Kries chromatic adaptation model and the maximum red-green-blue method, which has been popularly adopted in some video systems and color theories to estimate the illumination color and which, to a certain extent, agrees with the color constancy of human vision. The method has been proven effective after it was compared with Toet et al.'s fusion method. Its colorfulness is enhanced by the strategy of assigning the difference between the source images to the blue channel, which is used in Toet et al.'s algorithm to underscore the characteristic components of the individual images. The additional opponent processing neurodynamic equation of the center-surround receptive field can improve the output contrast significantly and is believed to be more suitable for revealing details by human observers. Some perceptual evaluation results are also given at the end.

In color television broadcasting standards, such as National Television System Committee (NTSC) and phase alteration line (PAL), the bandwidth of the chrominance signals are even narrower than those of the luminance signals. Also in digital video standards, the chrominance signals are usually low-pass filtered and subsampled to reduce the amount of data. Because of these reasons, the chrominance signals have poor transition characteristics and the slow transition causes blurred color edges. A color transient improvement algorithm is proposed by exploiting the high-frequency information of the luminance signal. The high-frequency component extracted from the luminance signal is modified by adaptive gains and added to the low-resolution chrominance signals in the proposed algorithm. The gain is estimated to minimize the l2 norm of the error between the original and the estimated pixel values in a local window. The proposed algorithm naturally improves the transient of the chrominance signal as much as that of the luminance signal without overshoots and undershoots. The experimental results show that the proposed method produces steep and natural color edge transition and reconstructs narrow line edges that are not restored by the conventional algorithms.

We propose a fast method for linearizing the edge-preserving regularization. The regularization operator is decomposed to the sum of some linear operators. The phase-only image is used in place of the estimated image. Those linear operators are computed from the phase-only image. They are the approximation of the true regularization operator. The new discontinuity maps do not need to be computed from the last image estimate at every step of the algorithm. This fast method can reduce much algorithm processing time.

A critical problem of maximum a posteriori (MAP) super-resolution (SR) image reconstructed algorithms is the choice of an appropriate prior model. Instead of modeling an original image directly, this work proposes an edge-image-based approach for stable SR reconstruction of the Lorentzian distribution. Through analyzing the convex and derivative properties of the Lorentzian distribution, we demonstrate the validity and stability of the proposed method for MAP SR reconstruction. The Lorentzwidth parameter is calculated iteratively to control the general sharpness degree of the image in the SR reconstruction process. Experiments confirm the effectiveness and robustness of the proposed method, and yield both objective and subjective qualities of the reconstructed SR images significantly better than conventional methods.

We present a new boundary extraction model, called the quantum contour model. First, we discuss the well known and widely used deformable models from a point of view of classic mechanics. Then, boundary extraction is further considered as the motion of a particle described by quantum mechanics, which is in contrast to determining the minimum kernel energy associated with the boundary in an energy field of the deformable model. The principle and approach of boundary extraction based on particle motion in quantum mechanics are developed by estimating the probability that a particle moves from one point to another iteratively. Finally, experiments with simulated and real images demonstrate that the quantum-contour-based approach could extract a close boundary quickly, accurately, and robustly, with a single initial point close to the boundary of the object of interest.

Object detection in image sequences has a very important role in many applications, such as surveillance systems, tracking and recognition systems, and coding systems. We are interested in background subtraction, which is very popular algorithm for object detection in image sequences, and also concerned to use the result of detection in selective video coding. Especially when the camera moves and zooms in on something to track the target under drastic illumination change, it is very hard to detect the object properly, and the coding efficiency is reduced. So we generate a multiple background mosaic system, called the background mosaic plane, and use it for object detection and video coding. Some experimental results for both object detection and video coding in various environments show that the average performance of the proposed algorithm is good.

We have developed a mapping algorithm for correcting sinusoidally scanned images from their distortions. Our algorithm is based on the close relationship between linear and sinusoidal scanning. Straightforward implementation of this algorithm showed that the mapped image has either missing lines or redundant lines. The missing lines were filled by fusing the mapped image with its median-filtered or interpolated version. The implementation of this algorithm shows that it is possible to retrieve up to 98% of the original image (depending on the algorithm used for data fusion) as measured by the recovered energy. Excellent correction was obtained for both simulated scanned images and actual images from a scanning laser radar system.

We present a practical numerical method for processing the fringes obtained when two waves, with a quadratic phase difference function, interfere. This kind of fringe includes straight equispaced fringes and Newton's rings as particular cases. The numerical method we present is based on the discrete Fresnel (Fourier) transform of the data and has the same precision as least square fitting (LSF). Compared to the LSF method, this new method is better, as it is more efficient and does not require initial approximations for the fringe parameters to be determined.