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We propose a stable scale-adaptive tracking method that uses the centroids of the target colors in the target localization and scale adaptation. Because of the spatial information inherent in the centroids, a direct relationship can be established between the centroids and the scale of the target region. After the zooming factors are calculated, the unreliable zooming factors are filtered out to produce a reliable zooming factor that determines the new scale of the target.

Particle probability hypothesis density (PHD) filter-based visual trackers have achieved considerable success in the visual tracking field. But position measurements based on detection may not have enough ability to discriminate an object from clutter, and accurate state extraction cannot be obtained in the original PHD filtering framework, especially when targets can appear, disappear, merge, or split at any time. To meet the limitations, the proposed algorithm combines a color histogram of a target and the temporal dynamics in a unifying framework and a Gaussian mixture model clustering method for efficient state extraction is designed. The proposed tracker can improve the accuracy of state estimation in tracking a variable number of objects.

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Hologram, as a type of diffractive optical element, is sensitive to wavelength in the process of optoelectronic reconstruction. Due to the different wavelengths of three prime colors used in full color holographic projections, there are chromatisms which badly spoil the reconstructed image. The chromatisms are composed of transverse and longitudinal chromatisms. For a computer generated hologram, transverse chromatism can be compensated by resampling the object information. However, it becomes more complex for longitudinal chromatism. This paper analyzes how the image is reconstructed from the phase-type hologram in a holographic projection system and the causations of longitudinal chromatism. To remove it, this paper proposes loading a specially designed phase distribution on a phase-type hologram. The advantage of this method is that it can be achieved by computer calculation and without adding any hardware such as achromatic optical element. A time-sharing system for a full-color hologram projection is developed in this paper. Comparisons have been made between the reconstructed images with and without chromatism. The experimental result shows that the method is effective in removing longitudinal chromatism and the quality of the reconstructed image is improved.

The three-dimensional (3D) display based on the holographic functional screen is theoretically and experimentally presented. By properly designing the subholograms on the holographic functional screen, the whole 3D light field distribution can be recovered with the recorded angular spectra through the pinhole CCD camera array. The holographic functional screen is fabricated by the laser speckle method. Experimental results show that the fully continuous, natural 3D display is achieved without the limitations of conventional holography. Further improvements could lead to applications in industry, medical operation, military affairs, architecture design, mapping, and entertainment.

We propose a portable parallel phase-shifting digital holography system. Parallel phase-shifting digital holography is a technique capable of instantaneous and three-dimensional measurement of objects. This technique has been verified by an experiment on anti-vibration optical tables, but had not been realized as a system for practical use yet. Then, we designed a portable system of parallel phase-shifting digital holography for the purpose of practical use. The size and weight of the system are 450 mm (L)×250 mm (W)×200 mm (H) and less than 7 kg, respectively. We designed the configuration of the system in a way which can be easily changed to implement two types of parallel phase-shifting digital holographies. The system was constructed by the use of ready-made optical components. To confirm the validity of the system, the capability of the three-dimensional imaging free from the superimposition of the unwanted images, which was the problem accompanied with conventional in-line digital holography, with a single-shot exposure was successfully demonstrated.

We present a new approach for accelerated computation of hologram patterns of a three-dimensional (3-D) image by taking into account of its interline redundant data. Interline redundant data of a 3-D image are extracted with the differential pulse code modulation (DPCM) algorithm, and then the CGH patterns for these compressed line images are generated with the novel lookup table (N-LUT) technique. To confirm the feasibility of the proposed method, experiments with four kinds of 3-D test objects are carried out, and the results are comparatively discussed with the conventional methods in terms of the number of object points and the computation time. Experimental results show that the number of calculated object points and the computation time for one object point have been reduced by 73.3 and 83.9%, on the average, for four test 3-D images in the proposed method employing a top-down scanning method, compared to the conventional method.

Using a two-dimensional fast Fourier transform is an efficient way to calculate a kinoform. High-speed processing of large amounts of data points (e.g., a 512×512 matrix) can be accomplished using a kinoform. Real-time computer-generated hologram calculation has been widely pursued. To this end, use of the graphics processing unit (GPU) or multiprocessing methods are becoming popular for high-speed processing. We used the GPU method coupled with multiprocessing to construct a kinoform and measured the efficiency of this method.

A one-step digital holographic printing system based on RGB pulsed-laser technology is described. The system is capable of writing full-color composite digital reflection holograms and composite digital holographic optical elements up to a size of 1.0 m×1.5 m at hogel sizes ranging from 0.4 to 2 mm. We also show how the same pulsed-laser technology may be used to generate fast high-quality copies of such holograms. Both silver halide and photopolymer materials are used.

We present a novel method of obtaining precision measurement using two binary phase diffractive optical elements, termed the hologram, and phase mask. By encoding multiple views into the hologram, each of which corresponds to a horizontal or vertical relative displacement of the phase mask, the system is able to provide a visual feedback of the measurement without the use of electronics. A probabilistic method for detection of the resultant images, matched to the statistical properties of holographic replay, shows promise for enabling a fully automated measurement system.

Owing to the resolution of the recording device, digital holograms are generally fabricated with in-line configurations. However, holograms obtained in this way are plagued by the annoying problems of zero-order noise and the twin images. Here, we investigate methods to suppress the zero-order noise. We compare the suppression ability of each method with different ratio factors. The ratio factor is defined as the ratio between the reference light amplitude and the object light amplitude. We also introduce a new parameter, the normalized correlation peak value, to evaluate the fidelities of holograms obtained under various ratio factors. Results show that the suppression abilities and the hologram fidelities strongly depend on the ratio factor.

A hybrid phase retrieval approach is proposed to address the twin image problem in the reconstruction of in-line digital holograms. The approach is a variant iterative transform algorithm and exploits two mostly natural constraints of a sample, namely, the finite transmission and the finite support. Here, the initial sample support estimate is first refined by applying the finite transmission constraint with phase flipping. The approach provides better reconstruction than if only the finite transmission constraint is used and improve the convergence rate of Fienup's algorithm owing to a better estimate of support especially for strong samples with complex structures. Both simulation and experimental results are presented.

With recent advances in high-speed computer and video capture technology, holographic films used in classical holography can be replaced with charged-coupled devices (CCD) and complementary metal-oxide-semiconductor (CMOS) image sensors to record and numerically reconstruct a hologram, which is now known as digital holography. Digital holography introduces something new to optical science. Wet chemical processing and other time-consuming procedures can be removed, so numerical recording and reconstruction can be realized in almost real time. It allows us to characterize the phase of a light field as well the intensity, and so the whole wave field can be measured and stored in a computer. Digital holography is expanding applications of holography and becoming a scientific and technological tool. Its use has now increased for measuring amplitude and the phase of object waves, displacement and three dimensional shape, particle distributions and motions, characterization of the refractive index and biological tissues, and vibration analysis, etc. Here, basic principles of digital holography for optical measurement and characterization are described. Taking into consideration the rapid advance in CCD and CMOS sensors as the background, the state-of-the-art applications of digital holography to optical measurement and characterization are presented.

This article investigates the feasibility of real-time three-dimensional imaging of microscopic objects within various emulsions while being produced in specialized production vessels. The study is particularly relevant to on-line process monitoring and control in chemical, pharmaceutical, food, cleaning, and personal hygiene industries. Such processes are often dynamic and the materials cannot be measured once removed from the production vessel. The technique reported here is applicable to three-dimensional characterization analyses on stirred fluids in small reaction vessels. Relatively expensive pulsed lasers have been avoided through the careful control of the speed of the moving fluid in relation to the speed of the camera exposure and the wavelength of the continuous wave laser used. The ultimate aim of the project is to introduce a fully robust and compact digital holographic microscope as a process control tool in a full size specialized production vessel.

Digital holography has been growing in importance for application to environmental studies in the oceans and lakes of the world. With an imaging resolution using "classical" photoholography of a few micro-meters and recording volumes up to a cubic meter, several "holocameras" were developed and deployed for underwater imaging of plankton and other marine particles. For in-water deployment, however, the weight and size of these instruments restricted their use on advanced observation platforms such as remotely operated vehicles, and limited operational depth to a few hundred meters. Advances made in digital recording on electronic sensors, coupled with numerical reconstruction, led to the development of smaller, rugged holocameras. This freed holography from many of its constraints and allowed rapid capture and storage of images and holographic video recording of moving objects. Although holography is not the only optical method applicable underwater, its ability to record full-field, high-resolution, distortion free images in situ from which particle dimensions, distribution and dynamics can be extracted is hard to match. The current state-of-the-art in underwater holography is discussed, with an outline of some submersible holocameras. We describe one such system, eHoloCam, in more depth and present results from its deployment in the North Sea.

Color reflection multiplex holography is an obvious target for display applications. The aim of this project is to revisit the technique of multiplex holography using modern recording and developing methods and materials. In particular, exploiting techniques of color holography that have been developed in recent years and it should be possible to extend these to high resolution multiplex holography for small and creditcard sized holograms. The current generation of holographic laser printers is not suitable for such applications as they typically employ a pixel size of around 1 mm. This report outlines progress on the production of high- resolution small-sized holographic stereograms.

As a technique for displaying holographic three-dimensional (3D) images in the wide region with a wide viewing angle, spatial projecting technique onto the mist screen is well-known. For such purposes, other various techniques have been studied, however, it has been difficult to take a side view of 3D images. In order to overcome this problem, we have been challenged to improve a holographic 3D displaying system employing a mist screen. In this paper, we shall report a new display system which has an improved jetting mechanism compensating the characteristics of the mist screen and gives volumeful 3D images by combining the reconstructed waves from two ways. It is also shown that by the use of this system, we can better observe 3D images in the wider viewing region than before. From this, we confirmed the possibility of a holographic projecting process adopted mist screen displaying volumeful 3D holographic images.

When an optically guided hypersonic vehicle flies in the atmosphere, the scene is viewed through an optical dome. Because of hypersonic friction with the atmosphere, the optical dome is inevitably covered by a serious shock wave, which threatens to alter the dome's physical parameters and further induce wavefront distortion and degradation of images. By studying the physical phenomena occurring within the optical dome in such an adverse environment, this paper identifies the relationship between the variation of the dome's optical characteristics and the infrared image degradation. The research indicates that the image quality degrades sharply as the vehicle's Mach number increases. Simulations also show that while the thermo-optic effect, elastic-optic effect, thermal deformation, and variation of transmittance have little effect on the optical system, the thermal radiation severely degrades images when vehicles fly at hypersonic speeds

We apply noise suppression based on a feed-forward neural network (FFNN) onto hand vein images. A neural network is employed to classify corrupted and noncorrupted pixels. Filtering is only carried out on corrupted pixels, keeping the noncorrupted ones unchanged. The emphasis is on the selection of relevant inputs and training patterns. With appropriate choice of patterns, the assiduous task of FFNN training becomes effortless and noise detection in pixels becomes efficient. Comparative analysis on 20 sets of hand vein images using different filtering algorithms shows that filtering based on a FFNN scheme outperforms its counterparts.

The stability of phased-array optics is a crucial issue for far-field focal-spot quality. The tiled approach of phasing optical elements is a widely used technique. Here it is adopted to maintain the long-time stability of a tiled system by a proportional-integral-differential (PID) algorithm. Experimental data is taken with 2×1 tiled-flat square mirrors driven by 3-axis piezoelectric actuators. The feedback frequency is over 80 Hz and the displacement error is below 4 nm. The optical measurement results show that the state-locked operation is continuously maintained for hour-long periods in PID control mode.

A structured light system simplifies three-dimensional reconstruction by illuminating a specially designed pattern to the target object, thereby generating a distinct texture on it for imaging and further processing. Success of the system hinges upon what features are to be coded in the projected pattern, extracted in the captured image, and matched between the projector's display panel and the camera's image plane. The codes have to be such that they are largely preserved in the image data upon illumination from the projector, reflection from the target object, and projective distortion in the imaging process. The features also need to be reliably extracted in the image domain. In this article, a two-dimensional pseudorandom pattern consisting of rhombic color elements is proposed, and the grid points between the pattern elements are chosen as the feature points. We describe how a type classification of the grid points plus the pseudorandomness of the projected pattern can equip each grid point with a unique label that is preserved in the captured image. We also present a grid point detector that extracts the grid points without the need of segmenting the pattern elements, and that localizes the grid points in subpixel accuracy. Extensive experiments are presented to illustrate that, with the proposed pattern feature definition and feature detector, more features points in higher accuracy can be reconstructed in comparison with the existing pseudorandomly encoded structured light systems.

Polyethylene-based materials are used in many infrared products, including motion detectors. However, little data exists for their infrared optical properties, except at wavelengths longer than 22 μm. The refractive indices of two such materials were measured in the 9.25 to 10.6 μm spectral range, using refraction through thin prisms.

A modulation transfer function (MTF) calibration method based on binary pseudorandom (BPR) gratings and arrays has been proven to be an effective MTF calibration method for interferometric microscopes and a scatterometer. Here we report on a further expansion of the application range of the method. We describe the MTF calibration of a 6 in. phase shifting Fizeau interferometer. Beyond providing a direct measurement of the interferometer's MTF, tests with a BPR array surface have revealed an asymmetry in the instrument's data processing algorithm that fundamentally limits its bandwidth. Moreover, the tests have illustrated the effects of the instrument's detrending and filtering procedures on power spectral density measurements. The details of the development of a BPR test sample suitable for calibration of scanning and transmission electron microscopes are also presented. Such a test sample is realized as a multilayer structure with the layer thicknesses of two materials corresponding to the BPR sequence. The investigations confirm the universal character of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

We present a method of measure of the roughness of the paper based on the analysis of a speckle pattern on the surface. Images of speckle over the surface of paper are captured by means of a simple configuration using a laser, beam expander, and a camera charge-coupled device (CCD). Then we use the normalized covariance function of the fields, leaving the surface to find the roughness. We compare the results obtained with the results obtained with a confocal microscope and the Bendtsen method that is a standard of the paper industry. This method can be considered as a noncontact surface profiling method that can be used online.

We developed a high precision position decoding method for a positron emission tomography (PET) detector that consists of a thick slab scintillator coupled with a multichannel photomultiplier tube (PMT). The DETECT2000 simulation package was used to validate light response characteristics for a 48.8 mm×48.8 mm×10 mm slab of lutetium oxyorthosilicate coupled to a 64 channel PMT. The data are then combined to produce light collection histograms. We employed a Gaussian mixture model (GMM) to parameterize the composite light response with multiple Gaussian mixtures. In the training step, light photons acquired by N PMT channels was used as an N-dimensional feature vector and were fed into a GMM training model to generate optimal parameters for M mixtures. In the positioning step, we decoded the spatial locations of incident photons by evaluating a sample feature vector with respect to the trained mixture parameters. The average spatial resolutions after positioning with four mixtures were 1.1 mm full width at half maximum (FWHM) at the corner and 1.0 mm FWHM at the center section. This indicates that the proposed algorithm achieved high performance in both spatial resolution and positioning bias, especially at the corner section of the detector.

We incorporate Co thin layers into the quadrilayer structure of glass/Cu/SnO₂/Co/SnO₂ and investigate the effect of transparent semiconductor SnO₂ as cap and spacer layers on the magnitude of a magneto-optical Kerr signal. The theoretical calculations based on a 4 × 4 matrix method are exploited to find the best possible multilayer structure. Accordingly, we fabricate several samples and acquire large Kerr signals in both polar and longitudinal geometries. Furthermore, the effect of vacuum annealing on the magnetic response of the samples is investigated. It is revealed that annealing at high temperatures may reduce the Kerr response because of uncontrolled heat-induced interdiffusion of adjacent layers.

An improved virtual display is proposed by using a waveguide holographic configuration with two total internal reflection holographic gratings in conical mounting and two volume hologram in classical mounting recorded on a single transparent planar waveguide. Using this compact configuration, efficiency can be dramatically improved and assembly is easy to be realized. The main principle and the method of intensity uniformity control are present in the paper. The analysis and simulation results are also explained. The virtual display system design shows good optical performance with 25 deg. field of view, a large pupil about 43 mm, little distortion less than 1%, and low aberration. The configuration can be used to a portable or wearable display.

A generation algorithm is used to optimize a tunable optical wavelength selection switch (WSS) which is based on a cascaded silicon microring resonator. This method can help us find the optimal inter-ring coupling coefficients which can lead to smaller ripple and better wavelength selectivity over a predefined pass band range. In this paper, we validate this method by a real design and report the results of several, such GA-based WSS optimization. The results show that the GA method performs well even under the limit of physical properties of a silicon ring resonator.

We investigated a viewing angle control of a liquid crystal display (LCD) under optical compensation for the enhancement of viewing angle characteristics in a wide viewing angle mode. The viewing angle controllable (VAC) LCD was operated in the configuration of three terminal electrodes consisting of a fringe-field-switching electrode at a bottom substrate and a common electrode at a top substrate. Using Poincaré sphere analysis, the optical compensation for the VAC LCD was designed so that the viewing angle characteristics were much improved in the wide viewing mode while they were degraded in the narrow viewing mode.

The main objective of this paper is to evaluate the performance of quantum dot infrared photodetectors (QDIPs). The tools that we are used are the VisSim environment, along with the block diagram programming procedures. The benefits of using this modeling language are the simplicity of carrying out the performance's measurement through computer simulation instead of setting up a practical procedure which becomes expensive, as well as the difficulty of its management. The roles that the parameters of fabrication can play in the characteristics of QDIPs are discussed through developed models implemented by VisSim environment. VisSim can be a powerful supplement to model the Poisson equation. MAPLE software is used to devise this model. The theoretical result confirms that implicit solution of QDIPs governed by dynamic equations provides exact handling of the device performance. As an example, dark current, photocurrent, and detectivity are investigated. In order to confirm our models and their validity on the practical applications, we make a comparison between the results obtained by MAPLE, VisSim, and that experimentally published, and full agreement is observed. The implemented models can help designers and scientists optimize their devices to meet their requirements.

We propose a new simple structure-based color combiner with red, green, and blue (RGB) laser diodes (LDs) and a thermally expanded core (TEC) fiber waveguide. As the color combiner used the LDs as optical sources, the total volume of the color combiner could be minimized as 3.84 cc and the output powers of RGB optical sources in the color combiner could be obtained efficiently as 10.324, 13.290, and 10.150 mW, respectively. A TEC fiber waveguide was used as a medium for color combination of RGB in the color combiner. As the TEC fiber waveguide was used as a key component for color combination, we could observe the color combiner had the degree of uniformity and the matching accuracy was good. The measured degree of uniformity and matching accuracy of RGB beams were 121 µm (in large diameter), 56 µm (in small diameter), and 109 µm (on x-axis), 20 µm (on y-axis), respectively.

The optical bandgap and photoresponse characteristics of middle-wavelength infrared (MWIR) mercury-cadmium-telluride (HgCdTe) photodiodes have been performed based on a self-consistent solution of the Poisson's equation, the electron/hole continuity equations, and three-generation-recombination processes as Auger, Shockley-Read-Hall and optical generation recombination. Three different carrier-density approximations: (i) parabolic conduction-band approximation, (ii) Bebb's nonparabolic expression, and (iii) Harman's nonparabolic approximation, are proposed to calculate the optical bandgap and photoresponse of MWIR HgCdTe photovoltaic devices by considering the carrier degeneracy and the nonparabolic conduction band. It is found that omitting nonparabolic effect can lead to an enormous deviation in the simulation result, especially for heavily doped HgCdTe devices. On the basis of the calculated results of photoresponse, the parabolic conduction-band and Harman's nonparabolic approximations can lead to the response peak shift to short and long wavelengths, respectively.

We have adapted the point model for the study of an all-fiber laser doped with Nd³⁺ and Q-switched by a saturable fiber absorber doped with Cr⁴⁺. Calculations of the output power of the 1084 nm laser are considered as a function of the pump power supplied by a 790 nm laser diode. The analysis of the simulation results reveals the existence of pulsed, sinusoidal, and dc operating regimes.

An analytical method was investigated to design the gradient-index (GRIN) fiber probe based on characteristic parameters of a Gaussian beam propagating through the probe. First, a typical model of the GRIN fiber probe was presented, consisting of a single mode fiber, a no-core fiber (NCF), and a GRIN fiber lens. Second, a complex beam parameter matrix transformation method was adopted to derive the mathematical expressions of characteristic parameters, such as beam waist location, beam waist radius, and Rayleigh range. Then, MATLAB software was used to analyze the impact of the length of NCF and the length of the GRIN fiber lens on the characteristic parameters. Finally, performance comparison was performed between the calculation results and the experimental data published previously. The calculation results are in agreement with the experimental data and thus validate the presented analytical method for designing GRIN fiber probes. In addition, the characteristic parameters of a Gaussian beam going through the GRIN fiber probe will stay the same when the length of the GRIN fiber lens increases every 1/2 pitch length, which could be used to decrease the fabrication complication of GRIN fiber probes by increasing the length of GRIN fiber lens periodically.

A detailed analysis of the efficiency of four-wave mixing (FWM) is performed for a closely spaced energy state quantum dash semiconductor optical amplifier (SOA). The analysis takes into account the effect of all discrete energy states, the gain dispersion of the quantum dash, and the effect of doping on the FWM characteristics. Our analysis reveals that large FWM efficiency can be obtained when the energy of the pump signal is equal to the first excited state. We find that at low-applied current doping the dashes by p-type concentration enhances the FWM efficiency. While at high applied current, we find that doping the SOA with p-type concentration slightly enhances the FWM efficiency of the ground state and the first excited state and lowers the FWM efficiency of the higher excited states. Also we find that doping the dashes by n-type concentration slightly modifies the FWM efficiency spectrum.

A positive branch unstable-waveguide hybrid resonator has been designed for a RF-excited slab CO₂ laser of 100 W level. The output beam mode and the propagation characteristics in the two directions of unstable and waveguide were investigated by numerical and experimental methods. The results show that the output beam was collimated in the unstable direction, and was an approximate fundamental mode in the waveguide direction with a divergence angle of 12 mrad. The output power decreased by 50% with the misaligned angle of the tail mirror of 1.5 mrad, and was close to 0 with the misaligned angle more than 3 mrad.

This paper presents a demodulation scheme using phase-generated carrier (PGC) for a fiber Fabry-Pérot interferometric (FFPI) sensor with high finesse. The FFPI is constructed by a polarization maintaining fiber ring resonator with dual-coupler (PMDC-FRR), which can eliminate the polarization induced fading phenomenon. Compared with the former phase demodulation methods, the PGC scheme in this paper does not assume a two-beam interferometric approximation for the Fabry-Pérot cavity, and can work at arbitrary value of finesse in theory. Two PMDC-FRRs with reflective coefficients of 0.5 and 0.9 are made in experiments for demodulation. Both the single-frequency and the wideband signals are successfully demodulated from the transmission intensities using the PGC demodulation scheme. The experimental results demonstrate that the PGC demodulation scheme is feasible for the FFPI sensor with high finesse. The effects of the reflective coefficient and the intensity loss to the finesse are also discussed.

The plane-wave expansion method and coupled-mode theory were used to calculate the reflection spectra of photonic crystal fiber (PCF) Bragg gratings (BGs) filled with liquids (PCF-BGs-liquids). The simulated reflection spectra of the PCF-BGs-liquids agree well with the reported experimental results. The simulated Bragg wavelength shift of the PCF-BGs filled with optical index matched liquid is 100 pm/ °C as the temperature changes from 25 °C to 65 °C. Therefore, PCF-BGs-liquids can be used as high sensitivity temperature sensors.

In this paper, we report a novel method of free-space passive optical coupling to completely embedded, transmission-based fiber Bragg grating (FBG) sensors. Fiber optic sensors (FOS's) have attracted intense research and commercial interest. A major challenge in implementing embedded FOS's, however, is improving upon the cumbersome and fragile ingress/egress techniques commonly used for bringing the sensing light into and out of the structures. In this paper, we successfully couple free-space light into and out of an embedded FBG sensor, without the use of physical connectorization. This coupling is enabled by splicing a multimode fiber (MMF) to a single mode fiber Bragg grating (SMFBG), and using hand polishing to integrate 45° mirrors onto the ingress and egress points of the MMF and SMFBG, respectively. We determine the total loss of the system to be 23 dB, which is considerably better than previous studies that did not use this hand polishing technique. We also demonstrate the application of this free-space coupling technique to strain measurement with a maximum strain of about 2000 µ&Vegr;. With this approach, no "pigtailing" of optical fibers is needed, and the FBG sensors can be completely embedded inside the structures, greatly increasing system simplicity and robustness.

Serrodyne phase modulation is one of the most widely used frequency shifting techniques in a resonator micro-optic gyro (RMOG). However, to achieve high gyro performance, extraordinary linearity of the serrodyne waveform is critically required. In this paper, compact RMOG with an ultrashort micro-optic resonator using analog triangle phase modulation is proposed. Theoretical analysis on the effects of second and third order nonlinearity of the modulation waveform, along with quantitative calculation of errors induced by the modulating nonlinearity, is presented. Performances of the established RMOG system are experimentally demonstrated, with nonlinearity measurement of the generated and applied triangle waveform. The proposed scheme shows great capability in near-linear waveform generation with quite simple electrical elements.

We present fabrication of optical waveguides in a photosensitive polymer. The process to fabricate monomode polymeric channel waveguides using simple direct ultraviolet (UV) photolithography is optimized. Channel waveguides of width ~2 to 2.4 µm and height ~1.8 to 2.2 µm are obtained on development after a crosslinkable negative tone epoxy SU-8 2002 polymer is exposed to UV through a photomask. Norland Optical Adhesive 61 (NOA 61) was used as under- and overclad. The average insertion loss obtained at chip-level is ~11 dB (TE₀₀) and ~12 dB (TM₀₀) for 2-cm waveguide at 1550 nm.

A model based on the charge-density flux (CDF) is proposed for the electric-field-assisted (EFA) ion-exchange, which is suitable for various EFA ion exchanging processes. Theoretical analysis shows that the CDF model is equivalent to the voltage model when the local temperature change around the glass wafer is negligible when a constant voltage is applied to the ion exchanging process. However, our experiments show that the CDF model is more applicable than the voltage model because the constant-voltage scheme shows a positive feedback process and the local temperature rising is unavoidable in the ion exchanging process. Our further experiments also show that the EFA ion exchanging process can be conveniently characterized by the proposed CDF model with the monitored electrical current, no matter the EFA ion exchanging process is with a constant-voltage/current scheme, a mixed scheme, or even a scheme with random voltage change, while additional complicated measures will be required to characterize the EFA ion exchanging process with the traditional voltage model.

The paper studies an all fiber high-speed magneto-optic switch which includes an optical route, a nanosecond pulse generator, and a magnetic field module in order to reduce the switching time of the optical switch in the all optical network. A compact nanosecond pulse generator can be designed based on the special character of the avalanche transistor. The output current pulse of the nanosecond pulse generator is less than 5 ns, while the pulse amplitude is more than 100 V and the pulse width is about 10 to 20 ns, which is able to drive a high-speed magnetic field. A solenoid is used as the magnetic field module, and a bismuth-substituted rare-earth iron garnet single crystal is chosen as the Faraday rotator. By changing the direction of current in the solenoid quickly, the magnetization of the magneto-optic material is reversed, and the optical beam can be rapidly switched. The experimental results indicate that the switching time of the device is about 100 to 400 ns, which can partially meet the demand of the rapid development of the all optical network.

The bound state solitons have been observed in the passively mode-locked fiber laser. The spectra are modulated due to interaction of the pulses per round trip. Two bound states have an equal shoulder as seen from the autocorrelation trace and three bound states have the two pairs of shoulder in the autocorrelation trace. The numerical results confirm the experimental results. The unstable soliton pairs can also be observed in the experiments. The pulse pairs with strong strength in the cavity can be potentially applied in the optical communication systems.

Multiple optical orthogonal codes sequences (MOOCS)-based optical labels for optical packet switching (MOOCS-OPS) were proposed and studied in our previous works. In order to evaluate the performances of the MOOCS-OPS networks resulting from interference of the MOOCS-based optical labels, we utilize a new study method that applies the independent case of multiple optical orthogonal codes to derive the probability function of the MOOCS-OPS networks for the first time. Additionally, the optical label processing time, the utilization efficiency, and the packet loss rate in the MOOCS-OPS networks are also considered. We discuss the performance and efficiency characteristics with a variety of parameters, and compare some characteristics of the system employed by a single optical orthogonal code or MOOCS-based optical labels. The performances of the system are also calculated, and our results verify that the method and the networks are effective. Moreover, it is found that performances of the MOOCS-OPS networks would, negatively, be worsened, compared with the single optical orthogonal code-based optical label for optical packet switching; however, the MOOCS-OPS networks can greatly enlarge the scalability of the optical packet switching networks.

In a wavelength division multiplexed-passive optical network (WDM-PON), different fiber lengths and optical components would introduce different power budgets to different optical networking units (ONUs). Besides, the power decay of the distributed optical carrier from the optical line terminal owing to aging of the optical transmitter could also reduce the injected power into the ONU. In this work, we propose and demonstrate a carrier distributed WDM-PON using a reflective semiconductor optical amplifier-based ONU that can adjust its upstream data rate to accommodate different injected optical powers. The WDM-PON is evaluated at standard-reach (25 km) and long-reach (100 km). Bit-error rate measurements at different injected optical powers and transmission lengths show that by adjusting the upstream data rate of the system (622 Mb/s, 1.25 and 2.5 Gb/s), error-free (<10⁻⁹) operation can still be achieved when the power budget drops.

A simple positioning method is proposed to easily implement a circular subaperture stitching test when the tested optics can be covered by one circle subapertures. In this situation, the border of the phase data image is used to locate the position of the subapertures. The simulation results show that it can provide pixel-level positioning accuracy when the quality of the data image is good. Furthermore, an optimization algorithm is introduced to reduce the positioning error and minimize the mismatch in the overlapping area. Finally, we study the applicability of this method to a subaperture stitching test of a parabolic surface. The stitching results are consistent with the full-aperture test results.

Segmenting the valid measuring region from an interferogram is an important step in the grazing incidence interferometry, which is related to the accuracy of the measurement result. For the spurious fringes which are generated by the diffuse reflection of the chamfering in the edge of the object surface, we propose a method-spin segment to correct the result of the image segment. First, a phase schematic diagram whose stripe feature is clearer than the original interference fringe patterns is generated. Next, the difference of the gray gradient between the fringe's local normal direction and local tangent direction is calculated to judge the valid measurement region. The principles of selecting some parameters are summarized and the calculation steps are shown. To examine the correction method, the results of an experimental application of spin segment are given to verify the feasibility and accuracy.

Matching points between two or multiple images of a scene is a vital component in many computer vision and pattern recognition tasks. The key step of point matching is how to construct a distinctive and robust descriptor. A state-of-the-art scale-invariant feature transform (SIFT) descriptor has proven that it outperforms other local descriptors on the distinctiveness and robustness. However, the SIFT descriptor neglects the global context of the feature points, as thus it fails to resolve the ambiguities that occur in local similar regions in an image. In this paper, a spatial distribution (SD) descriptor is constructed for each feature point detected by the SIFT method. It uses a log-polar histogram to build the global component according to the difference-of-Gaussian convolution image information. The spatial distribution descriptor has rotation, zoom invariance and partial skewness invariance due to that it integrates the local and global information of feature points. Points matching are performed on various images by the proposed framework. Experimental results show that the SD method outperforms the method using only SIFT.

The acquisition of a three-dimensional (3-D) model in a real-world environment by scanning only sparsely can save us a great ammount range-sensing time. We address a new method for inferring missing range data based on the given intensity image and sparse range data. It is assumed that the known range data are given on a number of scan lines with 1 pixel width. This assumption is natural for a range sensor to acquire range data in a 3-D real-world environment. Both edge information of the intensity image and linear interpolation of the range data are used. Experiments show that this method gives very good results in inferring missing range data. It outperforms both the previous method and bilinear interpolation when a very small percentage of range data are known.

In this paper, a hierarchical encrypted image watermarking technique based on a fractional domain random phase encoding method is proposed. Multiple watermarks encrypted at multiple levels are multiplexed in the fractional Fourier domain and added into a host image. The watermarks are encrypted by the conventional fractional Fourier domain double random phase encoding scheme. The proposed method offers extra security. The invisible watermark is recovered by applying correct random phase masks along with the correct fractional orders. The metric peak signal-to-noise ratio is used to evaluate the visual quality of the watermarked image. To check the robustness of the proposed technique, the effects of image processing operations, such as cropping, mean filtering, median filtering, and noise, are also studied. For watermark authentication, the correlation value is calculated between the original and retrieved watermarks. Simulation results are presented in support of the proposed idea.

An optimization scheme based on a genetic algorithm (GA) is proposed for kinoform synthesis. Unlike conventional optimization schemes, the initial kinoforms here are obtained by Fourier transform of the original image with random phase masks. The phase masks are then optimized by GA in order to reduce the reconstruction noise caused by amplitude negligence and phase quantization. Compared with the conventional methods of the genetic algorithm, in which optimization is directly performed to the kinoforms, the scheme can significantly improve the convergence and reduce the computation cost.

Many pan-sharpening techniques have been developed to synthesize a multispectral (MS) image at high resolution by fusing MS images and panchromatic (Pan) images. Most existing pan-sharpening methods can achieve results with high spatial resolution, but the spectral distortion in the fused results is still a problem that needs to be solved. In this paper, an adaptive linear model is proposed to reduce the spectral distortion by weakening the dependence on the correlation between Pan and MS. The difference between a Pan image and the combination of MS images is estimated by least square optimization, and embedded into the proposed model as a virtual band. According to the adaptive model, an iterative pan-sharpening algorithm is proposed based on the steepest descent method, in which the virtual band is used as a local adaptive constraint to the optimized solution. The proposed method is tested on datasets acquired by IKONOS, QuickBird, and Landsat 7 ETM+ and compared with the existing methods. The quality measures and the visual impressions show that the proposed method is an efficient approach to preserving spectral information and represents strong robustness against various scenes and sensors.

When the object is similar to the background, it is difficult to segment the completed human body object from video images. To solve the problem, this paper proposes an object segmentation algorithm based on guided layering from video images. This algorithm adopts the structure of advance by degrees, including three parts altogether. Each part constructs the different energy function in terms of the spatiotemporal information to maximize the posterior probability of segmentation label. In part one, the energy functions are established, respectively, with the frame difference information in the first layer and second layer. By optimization, the initial segmentation is solved in the first layer, and then the amended segmentation is obtained in the second layer. In part two, the energy function is built in the interframe with the shape feature as the prior guiding to eliminate the interframe difference of the segmentation result. In art three, the segmentation results in the previous two parts are fused to suppress or inhibit the over-repairing segmentation and the object shape variations in the adjacent two-frame. The results from the compared experiment indicate that this algorithm can obtain the completed human body object in the case of the video image with similarity between object and background.

A new method for removing salt-and-pepper noise from corrupted images is presented. We employ an efficient impulse noise detector based on the image sparse representation to detect the noisy pixels, and a local median filter to estimate the intensity values of noisy pixels. Experimental results demonstrate that the proposed method obtains better performance in terms of both qualitative and quantitative evaluations than those de-noising techniques such as the median filter, the peak-and-valley filter, the detail preserving filter, and the boundary discriminative noise detection filter, etc. Especially, the proposed method provides high detection rate and preserves the detail very well.

We study the nonlocal total variation (NL-TV) regularization technique for image zooming, which exploits the spatial interactions in images. To solve the nonlinear Euler-Lagrange equation associated with the NL-TV regularization framework, we propose a split Bregman NL-TV image-zooming method. Furthermore, we give the convergence analysis of the proposed algorithm. Experimental results illustrate the effectiveness and reliability of our method by comparing it to some previous methods.

The gradient based feature, such as histograms of oriented gradients, focuses on the spatial distribution of edge orientations, but disregards the color information. Color-based features are very popular in image classification but rarely used in human detection. In this paper we propose a new human detection method by combining texture-based features with color information. Basically, local binary pattern (LBP) is used as a texture feature, and a new color feature, relational color similarity (RCS), is introduced to enrich the descriptor set. By combining RCS and LBP as the feature set, adopting linear support vector machine (SVM) as the classifier, carefully designed experiments demonstrate the superiority of RCS-LBP over other traditional features for human detection on INRIA human database.

The saliency toolbox (STB)/Itti model is an outstanding computational selective visual attention model. In this paper, we propose an improved STB/Itti model to overcome the drawback of STB/Itti-its output "saliency map" is not large enough for region of interest (ROI) extraction. First, we employ a simplified pulse coupled neural network (PCNN) with a special input image, and more importantly, the PCNN does not require iterations. Subsequently, the PCNN takes the place of the winner-take-all network in STB/Itti. Experimental results show that the improved STB/Itti model works well for ROI extraction, with the mean area under the curve value of 0.8306 and robustness against noise and geometric attacks. The proposed model can greatly enhance the performances of both STB/Itti and PCNN model in image processing.

This paper describes a tracking method to trace the movements of fluorescently labeled mitochondria in time-lapse image sequences. It is based on particle filtering, which is a state-of-the-art tracking method, and is enhanced with a spatial constraint to improve robustness. Since mitochondria move only through axons, the spatial constraint is generated by axon segmentation on a single frame, which is the average of all the frames. The spatial constraint limits the search space of the state vector and, consequently, lowers the chance for the tracking to get lost. Using a background subtraction algorithm, the proposed method is also equipped with automatic detection of starting points, thus minimizing the requirement for user input. Implementation of the proposed method for tracking of fluorescently labeled mitochondria in time-lapse images showed substantially improved robustness and speed compared to a conventional method. With these improvements, this new particle tracking method is expected to increase the throughput of fluorescently labeled mitochondrial transport experiments, which are required for neuroscience research.

Recently, as effective demand for high-quality, large-capacity content such as three-dimensional (3D), multiangle, and gigabit-web has increased, a network infrastructure capable of satisfying future broadcast and communication service requirements is required. In this paper, we introduce a convergence service based on a gigabit network and then propose a technique for delivering gigabit 3D content. Here, the term 3D content delivery technique refers to an overlay-multicast-based distributed service platform that is comprised of a media relay agent and a management server. The service platform is designed to back up both live video and file-based video streaming. Using this platform, we can provide 3D remote education and 3D multiangle services via 3D-based video streaming between a service provider and service consumers dispersed at different locations. To evaluate our 3D content delivery technique, we run a series of trials of gigabit network-based 3D trial services to service subscribers. Then, we conduct a survey to measure user satisfaction with the 3D delivery service and simulated network and service quality. From experimental results, we confirm that this type of distributed service platform can be used as the delivery framework for applications such as realistic 3D-based seminars or 3D video conferences.

In this paper, a fast watermarking algorithm for the H.264/AVC compressed video using Exponential-Golomb (Exp-Golomb) code words mapping is proposed. During the embedding process, the eligible Exp-Golomb code words of reference frames are first identified, and then the mapping rules between these code words and the watermark bits are established. Watermark embedding is performed by modulating the corresponding Exp-Golomb code words, which is based on the established mapping rules. The watermark information can be extracted directly from the encoded stream without resorting to the original video, and merely requires parsing the Exp-Golomb code from bit stream rather than decoding the video. Experimental results show that the proposed watermarking scheme can effectively embed information with no bit rate increase and almost no quality degradation. The algorithm, however, is fragile and re-encoding at alternate bit rates or transcoding removes the watermark.

We propose new method for the reduction of blocking artifacts present in low bit-rate coded images. This algorithm performs the deblocking operation in two modes that are determined by the number of edge pixels around the block boundary. The number of edge pixels is calculated by applying the Roberts edge filter. An appropriate filtering operation is performed for each mode in both the horizontal and vertical directions. First, when the mode is associated with a smooth region, a strong filtering operation is applied because flat regions are more sensitive to the human visual system. In the second mode, an adaptive low-pass filter that is based on pixel behavior around the block boundaries is applied. This filter reduces the blocking artifact without introducing undesired blurring effects, while the original image edge is preserved. Although the proposed approach is simple and operates in the spatial domain, experimental results show that it improves both the subjective and objective qualities of the coded image with various features.

Retina recognition by using joint transform correlator (JTC) with JPEG-compressed target and reference images is proposed. Recognition performance is studied by using retina images with different contrasts employed as test scenes. The simulation results show that regardless of the reference contrast, the compression-based JTC offers better recognition performance for a high-contrast target. The compression of target images has advantages in that recognition degradation caused by noise can be reduced and image transfer time delay can be accelerated.

Changes have been made to this article. See the full text for a description of the changes.

Changes have been made to this article. See the full text for a description of the changes.