This PDF file contains the editorial ““Try my image, please.”” for OE Vol. 45 Issue 08

We present a novel postprocessing algorithm for blocking artifact removal in the discrete Hadamard transform (DHT) domain, which does not require prior knowledge of quantization parameters and features low computational complexity. All block-based video coding methods suffer annoying blocking artifacts at low bit rates. We first acquire edge information for the frame, then calculate block activities from DHT coefficients so as to classify smooth and coarse regions adaptively. Blocking artifacts are adaptively filtered in the DHT domain according to block activities. Experimental results show that the proposed method is able to remove blocking artifacts effectively while preserving image details and object edges well, and that it achieves better visual quality compared with other methods.

We analyze the multicast capability of a multicast-capable optical add/drop multiplexer (MC-OADM) and investigate the dynamic network performance of the MC-OADM ring in comparison with that of the normal OADM ring without multicast capability. The simulation results show that the multicast scheme using MC-OADMs provides more multicast services and occupies fewer resources.

A novel all-optical logic NOR gate is presented that is composed of a semiconductor optical amplifier (SOA) and an optical bandpass filter. The NOR gate is successfully experimentally demonstrated at 40 Gbit/s. The experiment result shows good extinction ratio of larger than 12.0 dB with clear and open eye. The NOR gate has a simple configuration and allows photonic integration.

Practical aplanatic optics crafted from transparent dielectrics can approach the thermodynamic limit for radiative transfer in near-field systems. Designs are presented for the particularly challenging realm of high numerical aperture (NA) at the source and/or target. These light couplers can alleviate difficulties in aligning system components and can achieve the fundamental compactness limit for optical devices that satisfy Fermat's principle. Examples and performance estimates based on ray-trace simulations are presented.

A dual geometric active contour applied mainly in image segmentation is proposed. Two contours of the dual geometric active contour evolve from the interior and exterior of the segmented object, respectively, to the desired boundary. The inner and outer contours represented by level set functions interact with each other during the evolutions of the active contour to avoid getting in local minima traps of the functional optimizations. The experiments on image segmentation show that the proposed dual geometric active contour can relieve the problem in initialization.

We report the first demonstration of silica waveguide optical passive ring resonator gyro (OPRG) based on the phase modulation spectroscopy technique. The ring resonator is composed of a 6-cm-long silica waveguide. Observed from the resonance curve, the free spectral range (FSR) of the resonator, the full width at half maximum (FWHM) of the resonance curve, the finesse (F) of the resonator, and the resonance depth are 3.4 GHz, 62 MHz, 54.8, and 70%, respectively. The detection sensitivity of this OPRG will be 7.3×10^–5 rad/s. In the experiments, there is an acoustic-optical modulator (AOM) in each light loop. We lock the lasing frequency at the resonance frequency of the silica waveguide ring resonator for counterclockwise (CCW) lightwave; the frequency difference between the driving frequencies of the two AOMs is equivalent to the Sagnac frequency difference caused by gyro rotation. Thus, the gyro output is observed.

We present an all-fiber linear-phase equalizer for equalizing Gaussian-like spectra. The equalizer uses an optical lattice filter in a symmetric folded structure. Compared to existing solutions to linear phase equalization, the proposed equalizer has guaranteed linear phase responses and lower power attenuation. As an illustrative example, the effectiveness of the proposed equalizer is demonstrated with the flattening of the output spectrum of a superluminescent light emitting diode.

We describe an experimental procedure for the reconstruction of the geometrical parameters of a reflecting surface. The method is based on the projection of a luminous pattern constituted by colored points. The successive chromatic selection reduces the complexity of the acquired image. We show that the colors of the points comprising the pattern are modified by the combined effect of the CCD camera and the projection system. In some situations, the chromatic components of the pattern points can generate ambiguity. Consequently, the number of colors to be projected and their chromatic separation must be studied to enable the simultaneous projection of an elevated number of points and colors.

The "schlieren PIV" technique combines schlieren or shadowgraph optics with particle image velocimetry (PIV) equipment to measure the velocities of turbulent eddies in flows with sufficiently strong changes of the refractive index without actual particle seeding. Prior work on this technique used direct laser illumination that produced inadequate schlieren image quality due to coherent artifact noise and other problems. By way of a simple equipment modification, we show the white-light emission of a laser-induced air or argon breakdown to be an improved light source for schlieren and shadowgraph PIV. The Nd:YAG illumination used in standard PIV is converted to a white-light pulse by this means. High-quality schlieren images are obtained and measurements in a helium jet using this new approach compare well with previous data. The method is especially applicable to high-speed flows requiring time delays of 5 µs or less between the images of a PIV pair.

A commutative watermarking and encryption scheme is proposed for media data protection. In the scheme, the partial encryption algorithm is adopted to encrypt the significant part of media data, while some other part is watermarked. The commutative property brings conveniences to practical applications in secure media transmission or distribution.

A low-cost, single camera model is introduced for the measurement of point coordinates in a 3-D space. By adding two groups of symmetrical reflectors, a single charge-coupled device (CCD) camera can be imaged as a pair of identical virtual cameras, from which a stereo pair of images of an object with parallax can be simultaneously obtained in one image plane and used to retrieve the 3-D coordinates of a point using triangulation. Doing so, the traditional dual-camera system is simplified as a single camera structure. The calibration method is also presented, which is simpler and easier to carry out than that for a dual-camera system. Experimental results show that the single camera method is efficient.

A new real-time implementation of the Boltzmann-plot technique for optical spectroscopic analysis of thermal plasmas is presented. Applications are found in the monitoring of industrial processes in which plasma emission naturally occurs, such as arc and laser welding. Experimental results show the feasibility of using the Boltzmann-plot technique for real-time calculation of the electronic temperature of the plasma, a parameter that has been correlated with common defects found in the weld seam. The foundations of the proposed technique, its implementation, and its capability for the on-line detection of defects in tungsten inert gas (TIG) welding of steel parts are discussed.

We present an optical data reconstruction method to be used for cancer diagnostics via cytological and histological images. The approach allows realizing extended depth of focus and data compression using wavelet transformation that is realized optically with very low computational complexity. The extended depth of focus and the compressed images are generated out of a set of optically defocused images realized due to axial translation of the diagnosed sample. The extended depth of focus image may be used for 3-D cytological information display without stereo projection. Note that the extended depth of focus actually means super-resolving imaging, since getting out of focus means filtering the high band spatial frequencies within the image.

We build a refractometer capable of measuring refractive indices at low temperatures from visible to near-infrared wavelength. Refractive indices of 20 optical materials (three fluorides, 15 glasses, fused silica, and KRS-5) are measured at wavelengths of 365.0, 435.8, 546.1, 1014.0, 1529.6, 2122, and 3298 nm at temperatures of ~80, 120, 180, 240, and 293 K. The temperature dependences of the refractive indices are shown in a table and figures.

System calibration, which usually involves complicated and time-consuming procedures, is crucial for any 3-D shape measurement system. In this work, a novel systematic method is proposed for accurate and quick calibration of a 3-D shape measurement system we developed based on a structured light technique. The key concept is to enable the projector to "capture" images like a camera, thus making the calibration of a projector the same as that of a camera. With this new concept, the calibration of structured light systems becomes essentially the same as the calibration of traditional stereovision systems, which is well established. The calibration method is fast, robust, and accurate. It significantly simplifies the calibration and recalibration procedures of structured light systems. This work describes the principle of the proposed method and presents some experimental results that demonstrate its performance.

A simple technique is devised for testing half an angle of any prism. A method is suggested to set up the autocollimator for half an angle of any master prism with any angle when a suitable angle gauge or gauge combination is not available.

A measurement method for birefringence dispersion is proposed using geometric phase. The optical arrangement consists of a white light source, polarizer, sample, quarter-wave plate, rotating analyzer, such as in a Senarmont setup, and a spectrometer for the visible spectrum from 450 to 750 nm. The experimental setup achieves a phase shift via the geometric phase produced by a cyclic change of polarization state on a Poincaré sphere. We can select four points of geometric phase when the analyzer is set at –45, 0, 45, and 90 deg. It is mathematically demonstrated that these points of geometric phase are independent of wavelength from the calculation of spherical trigonometry drawn on the Poincaré sphere. The phase shifting technique using these four geometric phases is applied to measure birefringence dispersion. Polymer films and optical crystals as samples are experimentally demonstrated, and it is shown that the experimental results agree well with the known quantities of retardation in the visible spectrum.

An instantaneous phase stepping and subsequent phase analysis method, using a charge-coupled device (CCD) camera with a pixelated form-birefringent microretarder array, is proposed for 2-D birefringence distribution measurement. A birefringent sample placed behind a polarizer and a quarter-wave plate is analyzed by the proposed method. Light emerging from the sample is recorded using a CCD camera that has a pixelated microretarder array on the CCD plane. This microretarder array has four different principal directions. That is, an image obtained by the CCD camera contains four data corresponding to four different optical axes of the retarder. The four images separated from the image recorded by the CCD camera are reconstructed using gray-level interpolation. Then, the distributions of the Stokes parameters that represent the state of polarization are calculated from the four images. The birefringence parameters, that is, the angle of the principal axis and the phase retardation, are then obtained from these Stokes parameters. This method is applicable to real-time inspection of optical elements as well as the study of the mechanics of time-dependent materials, because multiple exposures are unnecessary for sufficient data acquisition in the completion of data analysis.

The characteristics of lanthanum fluoride (LaF₃) thin films deposited with a resistive heating (RH) boat and by e-beam gun evaporation at different substrate temperatures have been studied. The characteristics of the deposited films, including optical properties, stress, and laser-induced damage threshold (LIDT), were related to the microstructure as well as the stoichiometry of the film. The films exhibit obvious different characteristics between these two processes at various substrate temperatures. It was found that optical properties, stress, and LIDT were affected by the microstructure and composition of the films. To obtain a high value of the LIDT and good optical properties, LaF₃ thin films should be deposited by the RH process at a substrate temperature of 300 °C.

The time and frequency response behavior of a new class of photodetectors based on a light-sensitive protein, known as bacteriorhodopsin (bR), is described. Each bR-based detector consists of an indium tin oxide (ITO) electrode/bR thin film/indium tin oxide (ITO) electrode structure. The response of the photodetector to square-wave and transient pulse illumination are both simulated using an equivalent resistor-capacitor (RC) circuit and experimentally observed. The investigative study demonstrates that the physical dimensions of the sensor surface, load resistance and capacitance, and the illumination conditions all have an impact on the transient response and gain-bandwidth characteristics. It is observed that changing the sensing area of the detector only affects the amplitude of the response, but not the bandwidth. Increasing the load resistance produces a higher gain, but reduces bandwidth. Increasing the load capacitance has the effect of dramatically reducing both gain and bandwidth. The observations and conclusions derived from this research provide design guidelines for developing hybrid photoelectric sensors and imaging arrays using bacteriorhodopsin thin films.

To reduce the cost of optoelectronic modules, powder metallurgy (PM) and metal injection molding (MIM) are employed to fabricate metal housings for optoelectronic packages. During the laser welding of PM steel, the rising gas pressure pushes the molten metal out of the welding regions, resulting in weak and unstable joints. Metal parts fabricated by the MIM method provide good weldability, shape complexity, low cost, and long-term reliability. By using the MIM method, defect-free welding joints and postwelding-shifts of less than 1 µm are achieved, and the optoelectronic packages are reliable. Employment of MIM not only gives optoelectronic module designers more design flexibility due to the advantage of shape complexity, but also makes low-cost triple-directional optoelectronic modules realizable.

Photomultipliers have a wide range of applications, from nuclear medicine to nuclear physics. In particular, they are commonly used in high energy physics and astrophysics. The Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescope is an example of their applications. This work presents a test system for the characterization of the transient response of the photomultipliers used as fast light detectors in the telescope. The bias of the photomultiplier is described, taking into account its effects in the response to fast light pulses. Two methods are used to generate these pulses: 1. a specifically designed pulse generator, and 2. a plastic scintillator. For the former case, we also calculate the anode charge we expect in this setup to cross-check it with the actual measurements.

Light transmission and reflection characteristics of metallic prism sheets are investigated based on a geometric optics approach. An analytic method is presented for finding the radiant intensity profiles of light transmitted through and reflected by a single metallic prism sheet for an incident light with arbitrary radiant intensity profile. With a simple interaction model between adjacent prism sheets, the analysis method for a single prism sheet is generalized for analyzing prism sheet layers composed of several prism sheets. Light transmission and reflection characteristics of a single prism sheet and prism sheet layers are compared. It is seen that the metallic prism sheet can be appropriately applicable to transflective devices or brightness enhancement film for liquid crystal displays.

By numerical simulations, it has been shown that a conventional cylindrical rod can be used as a hollow conic beam generator by illuminating a parallel laser beam inclined to the axis of the rod. Half of the conic beam is formed by the reflection at the surface of the cylindrical rod, and the opposite side of the conic beam by its transmission. We discuss the parameters to determine the size of the conic beam and the effect of the dielectric multilayer coating on the intensity distribution of the conic beam. The line beams of the shapes such as circle, ellipse, parabola, or hyperbola can be generated by this hollow conic beam generator, depending on the position and orientation of the observing plane.

Fiber Bragg grating (FBG) sensors show superior potential for structural health monitoring of civil structures to ensure their structural integrity, durability, and reliability. In this work, FBG sensors, including strain and temperature sensors, are applied for health monitoring of the oil production offshore platform number CB271, which is located in the Bohai Sea, East China. The procedure of FBG sensor installation during platform construction, as well as model validation in a laboratory under a variety of loading conditions on a seismic simulation shaking table, is also presented. In the tests, FBG strain sensors are placed as a strain rosette on the surface of the platform central pillar, and an FBG temperature sensor is installed close to those strain sensors for temperature compensation. The FBG sensors have been in operation for one year without any significant reduction of working performance. Strain responses induced by the impacts of ocean waves and the ship's hundred tons of weight are monitored on site successfully. The fundamental frequency of the platform identified by the results of the FBG sensors agrees well with that obtained by theoretical analysis. In the monitoring, FBG sensors exhibit excellent performance and higher tolerance to harsh environments in the long-term real-time health monitoring of ocean offshore platforms.

A displacement sensor enabling us to perform measurements under moderate feedback has been designed with a resolution up to 40 nm. Its performance can be optimized by using the wavelet transform when the signal is disturbed by electromagnetic fields, mechanical coupling, or speckle effect. By determining the repeatability and the reproducibility of this sensor, we have also demonstrated that this measuring device is suitable for statistical process control when an interval of tolerance of ±300 nm is required.

A simple and practical method to measure rotation axis two-dimensional displacements using a reflective intensity modulated optical fiber sensor is presented, in which a diffuse reflective pattern etched on the end face of the rotator is used to modulate the reflective optical intensity. In this manner, the amount and direction of the rotation axis transverse displacements (RATD) is determined by calculating the amplitude and the phase of the modulated intensity signal. Theoretical analysis and model design are presented, and an experimental system with precision motion control device and high accuracy air bearing rotator is established. The experimental results indicate that the resolution and the sensitivity of this sensor can respectively achieve 0.1 µm and 31.6 mV/µm. The direction measurement inaccuracy of the sensor is within ±2 deg. In addition, when adjusting the reflective distance, the sensitivity and linear measuring range of this sensor is adaptable.

A new type of fiber Bragg grating (FBG) sensor–based seismic geophone is presented. The major application of this FBG geophone is in the seismic reflection survey of oilfield exploration to detect the seismic waves from the Earth. The customized FBG geophone prototype that is demonstrated consists of two FBG sensor/demodulation grating pairs attached on a spring-mass mechanical system. The sensor performance is characterized in the laboratory in comparison with the conventional geophone. The FBG sensor is resistant to electromagnetic interference and has higher frequency response bandwidth and sensitivity than a conventional moving-coil electromagnetic geophone. The field tests results taken in the oil field show the sensor system frequency response bandwidth at 10 to 100 Hz in Shallow layer and 10 to 140 Hz in medium and deep layer separately.

We propose an one-dimensional (1-D) resonant hexagonal holes photonic bandgap (PBG) filter waveguide based on a silicon-on-insulator (SOI) substrate. In the 1-D resonant PBG filter waveguide, we use the technique of PBG and λ/4 phase shift to design our resonant PBG filter waveguide. According to the beam propagation method (BPM) simulation, the maximum transmission of the guided light is 89.91%, the quality factor is approximately 612.10, and the transmittance power uniformity over the 32 phase-shift wavelengths is about 1.3343 dB. The insertion loss is 0.4617 dB and reduces the size to 2.1 µm×57 µm on our designed resonant hexagonal holes PBG filter waveguide.

Light propagation through optical fibers consisting of a glass core coated with a high refractive index uniaxial dielectric thin film, in turn surrounded by a glass cladding, is presented. The dispersion equations are derived, and mode classifications are established for transverse and hybrid modes. Simulation results of lithium niobate thin film with bulk material dispersion are given as an example of uniaxial film. It is shown that modes are guided mainly in the film and the structure is capable of strong light confinement. Investigation of power flow along the propagation direction shows that the higher the film thickness, the higher the power density in the film.

A hybrid grism lens, which integrates an off-axis diffractive grating and an on-axis refractive lens onto a prism structure, is developed. The proposed grism lens can simplify the setup of grating-based wavelength-division multiplexing (WDM) device owing to the dual-functional characters combined within only one element. The 100-GHz dense WDM (DWDM) device based on the grism lens is designed with an insertion loss of 2.91±0.53 dB and a crosstalk of 58.02 dB. The tolerance analysis, the allowable grating tilt angle of ±0.5 deg and fiber displacement of ±1 µm, shows that the proposed structure could be practically applied to the grating-based demultiplexers.

In wavelength-division-multiplexing (WDM) mesh networks, previous routing algorithms are commonly used under the specific future traffic demand; however, it is difficult to predict the future traffic demand accurately in a practical sense. We propose a novel robust routing scheme based on Valiant load balancing in WDM mesh networks for the model of polyhedral uncertainty (i.e., hose model) and apply the scheme to low-speed connections with a traffic grooming approach. Our objective is to minimize total network cost. A mathematic formulation of the Valiant load-balancing robust routing scheme is presented and two fast heuristics are also proposed. When implementing the robust routing scheme to WDM mesh networks, a new traffic grooming algorithm called MHF (minimizing hop first) is proposed. We evaluate the MHF with the Valiant load-balancing robust routing scheme compared with traditional traffic-grooming algorithms.

In this paper, the refractive-index profile (RIP) of single-mode fiber is reconstructed from the measured transmitted near-field (NF) intensity combined with an inverse algorithm method, which can improve the conventional NF method to avoid the troubles introduced by multiple measurements and iteration smoothing in the processing of measuring the RIP without influencing the accuracy of the results. The method used here has the advantages of convenient operation and accurate results for the characterization of single-mode optical fiber; it can also be applied to the RIP measurement of graded index fibers, single-mode planar waveguides, and channel waveguides.

The system performance of data- and telecommunication equipment must keep up with the increasing network speed. Optical interconnections technology is a promising alternative for high-throughput systems. We demonstrate the optical backplane system using a waveguide-embedded optical backplane and two processing boards. The transmitter and receiver modules were prepared for optical printed circuit boards (PCBs), which consists of the metal optical bench, the driver chips, vertical-cavity surface-emitting lasers (VCSELs), photodiodes, and a tapered polymeric waveguide. We report high-speed transmission of 2⁷–1 pseudorandom bit sequence (PRBS) nonreturn to zero (NRZ) data up to 10 Gbits/s through the optical backplane system. The results demonstrate that the optical backplane system can be practical and valuable for the future high-throughput systems by using metal optical bench and precisely machined optical plug-adaptor structure to achieve stable board-to-board interconnection.

Free-space optical interconnects (FSOIs) are widely seen as a potential solution to present and future bandwidth bottlenecks for parallel processors. We study different topologies that can be implemented using an FSOI system called optical highway (OH). We propose also the use of the rapid prototyping technique as a fast and low-cost tool to implement experimentally different topologies and study their properties. Finally, the rapid prototype designed is used to calculate the maximum number of stages that an optical signal can go through in the OH without the necessity of being regenerated.

We propose an algorithm for recovering the overlapped harmonic components of a multiplex Fabry-Pérot interferometer (MFPI) spectrum. A potential solution that utilizes the multiresolution properties of the MFPI spectrum is presented. The corrupted harmonic components are detected by comparing consecutive harmonic pairs at the same sampling rate and window length. The overlapped spectral components are adjusted with correction terms that have been determined from the detection stage.

The phase shifting method is an effective tool to determine the intensity modulation distribution of a two-beam interferogram. We present numerical studies of the influence of two experimental errors on the results obtained using temporal phase stepping, i.e., the phase step miscalibration and average intensity changes between the component interferograms. Experimental studies of vibration mode patterns by time-average interferometry provide excellent verification of numerical findings. Comparative analysis of interferogram contrast and intensity modulation determination is included.

The holographic recording on the photosensitive medium with Weigert's effect in the general case of linear polarization of the object wave is investigated theoretically and experimentally. A simple analysis shows that it is possible to record and reconstruct the plane lightwave with all possible linear polarization in this case. The experiment conducted confirms rather well the analysis results. For the first time, an investigation is carried out in the case where the linear polarization changes continuously along the cross section of the object wave, which is important for some practical applications in the problems of optical memory and optical information processing.

Atmospheric weather conditions adversely affect the performance of free-space optical communications systems. Fog present in the atmosphere has the largest impact on free-space optical systems. We use simulation techniques to investigate the performance of a slant-path, wavelength-diversified free-space optical link between a ground station and an unmanned aerial vehicle in the presence of radiation fog. The free-space optical link is configured to operate using the simultaneous transmission of three wavelengths, 0.85, 1.55, and 10 µm, connecting a ground station to an unmanned aerial vehicle operating at either a 4- or 8-km altitude. The link is further analyzed by combining the multiple carrier wavelengths into either an equal-gain diversity scheme or a selective diversity scheme. The simulation results are obtained using ALTM and PcModWin simulation software from Ontar Corporation. The results obtained demonstrate that the use of either an equal-gain diversity scheme or a selective diversity scheme enables the deployment of a ground-to-air free-space optical communications link. Furthermore, a selective diversity scheme demonstrates a received power approximately three times greater than an equal-gain diversity scheme.

Recent developments in staring focal plane technology have spawned significant interest in the application of gated laser radar systems to battlefield remote sensing. Such environments are characterized by rapidly changing atmospheric seeing conditions and significant image distortion caused by long slant-range paths through the most dense regions of the atmosphere. Limited weight, space, and computational resources tend to prohibit the application of adaptive optic systems to mitigate atmospheric image distortion. We demonstrate and validate the use of a fast, iterative, maximum a posteriori (MAP) estimator to estimate both the original target scene and the ensemble-averaged atmospheric optical transfer function parameterized by Fried's seeing parameter. Wide-field-of-view sensor data is simulated to emulate images collected on an experimental test range. Simulated and experimental multiframe motion-compensated average images are deconvolved by the MAP estimator to produce most likely estimates of the truth image as well as the atmospheric seeing condition. For comparison, Fried's seeing parameter is estimated from experimentally collected images using a knife-edge response technique. The MAP estimator is found to yield seeing condition estimates within approximately 6% using simulated speckle images, and within approximately 8% of knife-edge derived truth for a limited set of experimentally collected image data.

We present a modified nonlinear correlation, called the morphological fringe-adjusted joint transform correlation (MFJTC), which is based on fringe-adjusted joint transform correlation (FJTC) and morphological correlation (MC). In MFJTC, the classical joint transform correlation (JTC) to implement the sublinear correlations (sub-LC) of MC is replaced with FJTC. The computer simulation results and an optoelectronic setup for MFJTC are given and compared with those of MC and FJTC. Simulations show that the MFJTC provides better stability against salt-and-pepper noise in the input scene, while maintaining high and sharp correlation signal. Although MFJTC loses the illumination-invariant recognition of MC when the input scene is brighter than the reference, it still ensures considerable discriminability.

We analyze the connection between viewer-perceived quality and encoding schemes. The encoding schemes depend on transmission bit-rate, MPEG compression depth, frame size and frame rate in a constant bit-rate (CBR) video transmission of a MPEG-2 video sequence. The compressed video sequence is transmitted over a lossy communication network with quality of service (QoS) and a certain Internet (IP) loss model. On the end-user side, viewer-perceived quality depends on changes in the network conditions, the video compression, and the video content complexity. We demonstrate that, when jointly considering the impact of coding bit rate, packet loss, and video complexity, there is an optimal encoding scheme, which also depends on the video content. We use a set of subjective tests to demonstrate that this optimal encoding scheme maximizes the viewer-perceived quality.

A novel non-motion-compensated method is proposed for dirt detection in archived film sequences. A confidence measurement extracted from raw differences between current frame and each of the previous and next frames is used to exploit the temporally impulsive nature of dirt impairments. Further evolution of the confidence signal enables the minimization of false alarms and the fine-tuning of detector sensitivity. After morphological filtering and consistency checks candidate regions of dirt emerge, enabling the computation of binary detection masks. Our experiments show that our method compares favorably with extended spike detection index (SDIp), rank order detector (ROD), and lower-upper-middle (LUM) approaches and provides efficient and robust detection performance for a wide range of archived film material.

Degraded printed character recognition is a hard and ever-present problem in optical character recognition. Previous work has explored serial combination of multilayer perceptron (MLP) and autoassociators networks for printed character recognition. The MLP is used as a first step classifier for its discrimination capability and is not very well suited for rejection. On the other hand, the autoassociator used as a second step classifier is more appropriate when a very small error and rejection are required. Unfortunately, this better behavior with respect to rejection is either paid in terms of rejection error or in terms of computational complexity, particularly when the number of classes is high. In this paper, we propose a serial combination of the Hopfield and MLP networks in order to achieve accurate recognition of degraded printed characters. We introduce a relative distance and use it as a quality measurement of the degraded character, which makes the Hopfield-based classifier very powerful and very well-suited for rejection. This relative distance is compared to a rejection threshold in order to accept or reject the incoming degraded character by the Hopfield model used as a first classifier. Due to its discrimination capability, the MLP network is used as a second classifier to avoid rejection error and to diminish computational complexity. The proposed method is devoted to solving the problem of recognition of single font characters collected from poor quality bank checks. We report experimental results from a comparison of three neural architectures: the Hopfield network, the MLP-based classifier, and the proposed combined architecture. The proposed method is also compared to five other recognition systems. It is shown that the proposed architecture exhibits the best performance, with no significant increase in the computational burden. In this paper, we propose also a bank check processing procedure for account check number (ACN) detection, localization, and character retrieval...

This paper introduces a new application of Bollinger bands for defect detection of patterned fabric. A literature review on previous designed methods for patterned fabric defect detection will be depicted. For data analysis, Bollinger bands are calculated based on standard deviation and are originally used in the financial market as an oversold or overbought indicator for stock. The Bollinger bands method is an efficient, fast and shift-invariant approach, that can segment out the defective regions on the patterned fabric with clear and crystal clean images. The new approach is immune of the alignment problem that often happens in previous methods. In this paper, the upper band and lower band of Bollinger bands, which are sensitive to any subtle change in the input data, have been developed for use to indicate the defective areas in patterned fabric. The number of standard deviation and length of time of Bollinger bands can be easily determined to obtain excellent detection results. The proposed method has been evaluated on three different patterned fabrics. In total, 165 defect-free and 171 defective images have been used in the evaluation, where 98.59% accuracy on inspection has been achieved.

The numerical calculation of the Fresnel transform (FST) presents significant challenges due to the high sampling rate associated with the chirp function in the kernel. The development of an efficient algorithm is further complicated by the fact that the output extent of the FST is dependent on the propagation distance. In this paper, we implement a recently proposed technique for efficiently calculating the FST in which we apply the Wigner distribution function and the space bandwidth product to identify suitable sampling rates. This method is shown to be suitable for all propagation distances. Our method can also be applied to describe the effect of a thin lens modeled as a chirp modulation transform (CMT). Combining our results for the FST and the CMT, we numerically calculate the light distribution at the output of both Cai-Wang and Lohmann Type-I optical fractional Fourier transform (OFRT) systems. Analytic solutions for the OFRT of rectangular window and circular apertures are presented. The analytical solutions are compared to experimental data and to numerical results for equivalent cases. Finally the numerical method is applied to examine the effect that apertured lenses, in the OFRT system, have on the output distribution.