This PDF file contains the editorial “Aggravated Edison” for OE Vol. 49 Issue 04

A new intraprediction method is proposed to decrease coding complexity as well as improve coding efficiency of H.264/AVC. Whether the predicted values of different prediction modes are similar is determined according to the proposed rules. When the predicted values are similar, the average of such values is used to predict the current block without invoking the rate-distortion optimization process. Experimental results show that by integrating the proposed method in the H.264/AVC codec, 39.25% coding time can be saved; meanwhile, the average bit-rate reduction is 2.62% under the same peak signal-to-noise ratio of reconstructed videos.

A multiple color-filter aperture (MCA) can provide a single camera with depth information and multifocusing. However, the original version of the MCA system exhibits inherent limitations such as manual, empirical tuning parameters for the color channel registration and fusion (CRF) process. Furthermore, a CRF output image still contains undesired out-of-focus blur because of the finite-sized apertures and the lateral displacement of each color-filter aperture, which results in low exposure, color mixing, deviation of color convergence, and divergence of light rays. For overcoming these problems, we present a real-time image processing solution for digital multifocusing in a MCA system.

The spatial-spectral holographic imaging system (S²-VHIS) is a promising alternative to confocal microscopy due to its capabilities to simultaneously image several sample depths with high resolution. However, the field of view of previously presented S²-VHIS prototypes has been restricted to less than 200 µm. We present experimental results of an improved S²-VHIS design that has a field of view of ~1 mm while maintaining high resolution and dynamic range.

Several novel designs of wide-field-of-view polarization imaging spectrometers based on combined Savart polariscopes are presented. By numerical modeling and analysis, we show that the field of view can be extended when the polariscopes are made of the same uniaxial crystal or positive and negative uniaxial crystals are combined. The designs with increased fields of view enable the acquisition of undistorted interferogram and high etendue for the spectrometer systems.

On the basis of Sagnac interferometric structure, a simple novel ultrafast scheme of all-optical half-adder is proposed. The structure comprises two of the same balanced terahertz optical asymmetric demultiplexers (TOADs). One TOAD is utilized to achieve an all-optical XOR gate, which is logic SUM. The other is utilized to obtain an all-optical AND gate, which is logic CARRY. Logical SUM and CARRY are simultaneously realized at 80 Gbit/s. Through numerical analysis, the operating characteristics of the scheme are illustrated at 80 Gbit/s. Furthermore, the carrier recovery time of the semiconductor optical amplifier is no longer a crucial parameter to restrict the operation speed of this scheme.

A theoretical and experimental study is performed to eliminate the effect of retroreflection of a camera by using masks. Theoretically, different types of masks are studied in terms of their capability to reduce the strength of the retroreflected signal while maintaining good camera image quality. Experimentally, the strength of retroreflected signals and image quality have been measured for different alignments of different masks. The results of these experiments in combination with the presented theory can be used to design masks that can reduce or even completely eliminate the strength of retroreflected signals, while simultaneously maintaining good image quality.

A new technique for the measurement of centering error (CE) of a lens using a cyclic path optical configuration (CPOC) is presented. The test lens (TL) is placed in the CPOC, adjusted for zero lateral shear. The mechanical axis (MA) of the TL holder is prealigned along the direction of the central ray (CR) of the counterpropagating collimated beams of the CPOC. A pencil beam is also set along the CR outside the CPOC. If the TL is free from CE, then its optical axis (OA) would coincide with the MA and the CR. The focal points F1 and F2, formed by the TL, and the center of the Haidinger-type fringes, due to interference of the light from F1 and F2 (which is along the line joining F1 and F2), would also lie on the CR. In the presence of CE, F1 and F2 would be laterally displaced from the CR and the fringe center (FC) suffers a deviation from the CR. Adjustments in the angular and lateral positions of the TL necessary to align the OA along the CR, as can be ensured from the coincidence of the FC with the CR, give a measure of the CE.

We focus on two key problems in the calibration of multi-sensor visual measurement systems based on structured light: the calibration of the structured light vision sensor, and the global calibration of multiple vision sensors. In the calibration of the vision sensor, the light-plane equation is computed by combining the Plucker matrices of light stripes obtained at different target positions. Since the light-plane equation is optimized by using all the light-stripe center points, the robustness and accuracy of calibration are considerably improved. For the global calibration of multiple vision sensors, the relative positions of the two vision sensors with non-overlapping fields of view are calibrated by means of two planar targets (fixed together), using the constraint that the relative positions of the two targets are invariable. The mutual transformations between the two targets need not be known. Using one of the vision sensors as the base vision sensor, the global calibration of multiple vision sensors is achieved by calibrating each of the other vision sensors with the base vision sensor. The proposed method has already been successfully applied in practic.

Phase measuring profilometry based on structured illumination with a digital projector has great flexibility. However, the phase error introduced by the gamma nonlinearity of the projector and the presence of speckle noise inevitably decreases the accuracy and resolution of the measurement. This paper presents a new phase error correction algorithm by which the odd-step fringe projection is done twice with an initial phase shift of π between, and the two captured deformed fringe images are then digitally subtracted. The speckle noise is further suppressed by applying a sine-cosine median filter. Both theoretical analysis and experimental results showed that this algorithm is effective and fast.

The use of pearlescent paints has grown significantly for many industrial products, due to their special visual effect, which originates from optical interference between many small pearlescent platelets. This makes the visual appearance of pearlescent paints vary with the light and view direction. Since pearlescent paints are very sensitive to specific wavelength bands, multispectrum-based representation methods that use spectral distributions give us more accurate image synthesis of them than does the use of RGB-based ones. In this paper, we present a novel image-based goniospectrophotometer system and its characterization method to acquire the spectral bidirectional reflectance distribution functions (BRDFs) for realistic image synthesis of pearlescent paints by combining two promising technologies, namely, high-dynamic-range images and multispectral images. The capability of our system is demonstrated by generating rendering results from four different material samples and comparing them with the RGB-based results and fully measured BRDF data.

We present a mathematical model exemplifying the manufacture of microfiber coil resonators (MCRs) with rotational and translational stages controlled by a computer. The MCR profiles are related to the stage positions; the result is important for practical manufacturing and application of MCRs.

A high power flashlamp-pumped Nd:YAG laser at 1123 nm with a repetition rate of 40 Hz is investigated. Simple but specially coated resonator mirrors are adopted to suppress the parasitic oscillation at gain transition lines higher than 1123 nm. A maximum average output power of 40 W with an electrical pumping energy of 45.7 J and pumping pulse duration of 150 µs is achieved. To the best of our knowledge, the output power of 40 W at a wavelength of 1123 nm is the highest record up to now.

A method is developed to determine the propagation characteristics of a high power laser beam using only Plexiglas^TM burn patterns. Under the assumption of an embedded Gaussian in the laser beam and using ABCD ray analysis, the fundamental laser beam characteristics, independent of the optical array, are determined. The method can be used to approximate the beam irradiance profile, peak irradiance, and beam characteristic size along the beam path, the cavity induced curvature applied to the beam, and the laser beam Rayleigh range. Finally, the beam far-field spreading angle and beam quality relative to an ideal beam are calculated. The method developed defines gross characteristics of aberrated beams generated by both stable and unstable laser designs.

Efficient beam shaping with uniform illumination is required in laser active imaging and detecting systems. In this paper, a beam-shaping method by superposition of tilted fundamental-mode Gaussian beams to produce nearly uniform illumination is proposed. The analytical formula for the average intensity of propagating multitilted Gaussian beams (MTGBs) is derived and used to study the uniformity of the beam profile with Fourier analysis. It is found that the MTGB maintains its flat-topped shape as it propagates and its uniformity is controlled by the parameters of fundamental-mode beams and superposition. Numerical examples are given. The method is used to reconfigure the beams of a high-power laser diode stack to form a MTGB shape for illumination of a 9×11.6-deg angular field. The simulation results from ASAP software show a shaping efficiency of 75%, and the rms deviation of the irradiance distribution from a flat-top shape is approximately 8%.

An idea of using a multipoint layer-type laser Doppler self-velocimeter (LDV) to offer velocity for the vehicle navigation system was proposed because the accelerometer had the error term generated by overload. The principle of measuring its own velocity with laser Doppler was expounded while a multipoint layer-type LDV was designed, and the Doppler signal was processed by the technique of tracking filter and digital autocorrelation. The result of theory and experiment showed that the multipoint layer-type dual-beam LDV system was suitable for measuring on rough road surfaces when the individual dual-beam LDV was in the status of out of focus. Low-frequency disturbance and some noises were eliminated by the tracking filter, and the residual noise was removed by digital autocorrelator so that the signal-to-noise ratio and the detection sensibility of the system was greatly improved. Comparing to the global position system, the relative accuracy of LDV is ~1.95%.

The potential well in back-illuminated charge-coupled devices (CCDs) does not reach all the way to the back surface. Hence, light that is absorbed in the field-free region generates electrons that can diffuse into neighboring pixels and thus decreases the spatial resolution of the sensor. We present data for the charge diffusion from a near point source by measuring the response of a back-illuminated CCD to light emitted from a submicron diameter glass fiber tip. The diffusion of electrons into neighboring pixels is analyzed for different wavelengths of light ranging from 430 to 780 nm. To find out how the charge spreading into other pixels depends on the location of the light spot; the fiber tip could be moved with a piezoelectric translation stage. The experimental data are compared to Monte Carlo simulations and an analytical model of electron diffusion in the field-free region. The presented analysis can be used to predict the charge diffusion in other back-illuminated sensors, and the experiment is universally applicable to measure any type of sensors.

A simple fiber optic temperature sensor with a micro Fabry-Perot cavity constructed with a thin film coated on a fiber end is presented. Its operation principle is based on the temperature-dependent wavelength shift of the interference fringes formed by Fresnel reflections from both interfaces of the thin film. An analytical formula is derived from the theory of two-beam interference. Experimental temperature data agree with the theoretical result. A temperature resolution of 0.1 K within the range from 20 to 100 °C with good stability can be achieved. The proposed temperature sensor has a simple, solid, and compact structure.

A direct UV written single-mode planar Bragg grating element is demonstrated, with >300 GHz of applied strain tuning. The degree of tuning that the fabricated device has leads to a potential application in dynamic optical networks as an optical add-drop multiplexer. The filter bandwidth is 23±5 GHz and can be tuned over a 308-GHz range by applying transverse strain across the device's composite silica-on-silicon structure.

We propose new blur and blocking metrics and then present a no-reference image-quality assessment method using these blur and blocking metrics. To compute the blur metric, we first estimated a blur radius from a given image and its reblurred version by using edge differences and edge amplitudes. Because blurring in edge regions is generally more sensitive to human perception, the blur metric was estimated from the edge blocks. We also used kurtosis and structural similarity to better estimate the blur metric. To compute the blocking metric, the blocking artifact was modeled as a 2-D step function and the blockiness visibility was estimated by the brightness difference between adjacent blocks. After the blocky position was determined, the blocking metric was computed from the six differences between four adjacent blocks. Experimental results show that the objective quality scores correlated highly with the subjective quality scores.

In wavelength-division-multiplexing networks, the fault-tolerance is very important since failures may lead to a significant amount of data loss. At the same time, the waveband switching technique is very interesting since it can save switching ports in optical cross-connections. In addition, the hierarchical routing in multidomain optical networks is very challenging since the interdomain routing is based on aggregative virtual topology. However, previous works did not jointly consider the three issues. We propose two schemes, segment-based protection (SBP) and path-based protection (PBP), to provide the fault-tolerance and waveband grooming in multidomain optical networks. In SBP, for each connection we first compute an interdomain loose route based on virtual topology, and then we compute the intradomain exact path-pairs in each single domain traversed by the loose route based on physical topology. In PBP, for each connection we first compute an interdomain loose primary path and an interdomain loose backup path based on virtual topology, and then we compute the intradomain exact paths in each single domain traversed by the loose primary path and backup path based on the physical topology. To support multidomain waveband grooming, we present the layered auxiliary graph. Simulation results show that PBP performs better than SBP.

This study demonstrates the gain variation of a distributed Raman amplifier (DRA) for wavelength-division-multiplexing (WDM) system. Experiments on a six-channel WDM system with DRA show a gain variation of less than 0.02 dB under the situation of dropping channels. Results show that the DRA system significantly improved gain variation arising from adding or dropping channels and changes in input signal power compared to an erbium-doped fiber amplifier (EDFA) system. Therefore, without employing any gain stabilization methods adopted, the DRA system can support more stable gain than an EDFA system when the input signal power changes and channels are added or dropped.

Coupling efficiency of coherent plane waves into single-mode fibers is degraded by the localized deformation of the optics antenna used for reception of optical beams. For transmission-type and reflection-type antennas, the evolution of coupling efficiency with the change of characteristic parameters of the localized distortion are investigated. It is found that the coupling efficiency varies regularly as the increase of the normalized center deepness h/R, the normalized radius a/R, and the normalized center distance d/R. The key principles for selecting optics are determined. The results obtained will be useful in estimation and design of fiber-coupled optical systems in free-space communications.

We systematically investigate the capabilities of a commercial intrusion detection system for a gigabit optical Ethernet network. It is found that the location of the tap and the amount of light tapped out are key factors in being able to successfully intercept the data. It is also shown, for the first time, that there is a region within the plane of distance from the transmitter versus power penalty where the link can be tapped and the data can be extracted successfully without the intrusion being detected.

We consider the design of a metal-oxide semiconductor field effect transistor-based transimpedance amplifier that represents the front end of an optical receiver for optimum noise performance in a lensless, free-space optical interconnects system. The optical diffraction noise and the electrical front-end circuitry noise are considered as the two main noise sources for the design optimization. We show that the capacitance of the photodetector diode as well as the input capacitance of the transimpedance amplifier can be used as design parameters to minimize the total noise.

Anomaly detection in hyperspectral images has proven valuable in many applications, such as hazardous material and mine detection. The benchmark anomaly detector is the Reed-Xiaoli (RX) detector, which is based on the local multivariate normality of background. The RX algorithm, along with its many modified versions, has been widely explored, and the main concerns identified are related to local background covariance matrix estimation. The small sample size, local background nonhomogeneity, and the presence of target pixels within the estimation window are factors that can deeply affect local background covariance matrix estimation. These critical aspects may occur together in the same operational scenario, and they may strongly impair the detection performance. However, due to their intrinsic difference, these aspects have been typically discussed within different frameworks, disregarding the possible existing connections while developing different approaches to solution. We investigate these critical aspects, along with their impact on the detection process, from an operational detection perspective. The approaches to solution are critically analyzed, discussing possible links and connections. Real hyperspectral data are employed for assessing if the algorithms, designed ad hoc to solve a specific problem, can either handle more complex situations, or bring about further complications.

The signal from a laser range finder is greatly enhanced by attaching a retroreflector to the target. Low-cost, lightweight retroreflectors can be fabricated from conspicuity tape. This work reports the near-infrared retroreflection characteristics of conspicuity tape from bidirectional reflectance distribution function (BRDF) measurements at 904 nm. BRDF values approach 500 sr^-1 at near normal incidence. The BRDF test results are applied to predict the performance of alternate lightweight retroreflector designs suitable for tracking small helium balloons. The combination of a range finder and retroreflecting balloon enable a low-cost, high-performance method for wind profiling.

Current focusing systems for hard x rays produced by laser-based sources provide focal spots of the order of 30 µm or larger. We propose a diffractive system that can improve this resolution. This system consists of a hollow cylinder perforated in a metal sheet, with the aperture size and length dependent on the desired focusing properties. Various configurations of this diffractive lens are analyzed and compared using numerical algorithms for beam propagation. Nanometric transverse resolutions (FWHM=550λ, which corresponds to 39 nm at λ=0.071 nm) and intensity gains larger than 14 are predicted for a configuration with a working distance of 1 mm on each side of the lens.

We propose to fuse an image's local and global information for scene classification. First, the image's local information is represented by context information exploited using spatial pyramid matching. Images are segmented to patches by a regular grid, and scale invariant feature transform (SIFT) features are extracted. All the patch features are clustered and quantified to get visual words. The visual word pair and visual word triplet are neighboring and different visual words. By an analogy between image pixel space and patch space, we also get visual word groups, which are the continuous occurrence of the same visual words. The spatial envelope is employed for extracting an image's global information. The spatial envelope is a holistic description of the scene, where local information is not taken into account. Finally, a stacked-support vector machine (SVM) fusion method is used to get the scene classification results. Experimented with three benchmark data sets, the results demonstrated that our methods could get better results than most popular scene classification methods presented in recent years.

We describe an optical imaging system based on random phase modulation and sparse sampling. The system is also an application of compressive sensing in the field of imaging. Different from the Rice compressing imaging system, the imaging system needs only a signal exposure. Meanwhile, the space-bandwidth product of the system is extended, which means the pixels of imaging sensor can be reduced without a loss of image's resolution. A random phase modulation is employed to make the energy of optical field spread out across the entire modulated image, which can facilitate the sampling process. A random sparse sampling scheme is designed to effectively reduce the pixels of imaging sensor, and the sensing matrix is uncorrelated with arbitrary sparse representation matrix. The feasibility of the proposed system is validated by numerical experiments.

Video transmission over error-prone channels often suffers from inevitable transmission errors, which necessitates proper error concealment (EC) for acceptable image quality. Furthermore, the region of interest (ROI) in images usually draws much attention, and so the EC of the ROI receives special treatment during encoding and decoding. We explore a data hiding-based scheme to effectively improve the EC of the ROI in the case of erasures of large continuous regions, which becomes impractical for conventional EC methods. At the encoder side, motion vectors of the ROI are adaptively embedded in the background based on original quantized coefficients of background macroblocks. Considering the limited embedding capacity of the background, we further propose to assign priorities to each ROI macroblock based on a predefined metric of error propagation. Our scheme is applied with the state-of-the-art H.264/AVC standard in a packet loss scenario, and better video quality can be obtained. Experimental results show that the scheme can improve the EC of the ROI significantly without much loss of coding efficiency.

Using quantitative evaluation, we show that constrained least-square (CLS)-based image restoration extends depth of capture volume (DCV) significantly, and suggest that performance degradation characteristics of a feature extractor by defocus blurring should be considered while developing unconstrained iris recognition systems. When developing an unconstrained iris recognition system (assuming a relatively cooperative user) the extension of the DCV clearly stands out as one of the most important problems. Although it has already been reported that CSL-based image restoration can improve recognition performance by mitigating the effect of defocus blurring, until now there have been no reports as to how much the DCV could be extended. This work inspects the Hamming distance (HD) distribution and error rate while changing the strength of defocus blurring with iris images of CASIA-IrisV3-Interval. It is derived that the ratio of the maximum blurring parameters satisfying a certain acceptable error rate is the ratio of the DCV. Using this fact, experimental results show that CLS-based image restoration extends the DCV by more than 70%. Additionally, it is observed that a log-Gabor filter is superior to a Gabor filter as the feature extractor. It should be noted that although these two feature extractors show a relatively small performance gap when a focused image set is used, the gap becomes significantly larger as the blurring becomes more severe. This is thought to suggest an important principle that performance characteristics should be considered with respect to defocus blurring when selecting or developing the feature extractor of an unconstrained iris recognition system.

Low-contrast profile images are frequently encountered in medical practice, and the correct interpretation of these images is of vital importance. This study introduces a contrast enhancement technique based on singular value decomposition (SVD) to enhance low-contrast fracture x-ray images. We propose a development of the traditional singular value solution by applying a feature selection process on the extracted singular values. The proposal calls for the establishment of a feature space in which the interpretability or perception of information in images for human viewers is enhanced, while noise and blurring are reduced. In this approach, the area of interest is manually cropped, and histogram equalization (HE) and singular value selection procedures are then conducted for comparative study. This approach exploits the spectral property of SVD, and the singular value selection algorithm is developed based on the corresponding Fourier domain technique for high frequency enhancement. The proposed method can generate more enhanced views of the target images than HE processing. Ten physicians confirm the performance of the proposed model using the visual analog scale (VAS). The average VAS score improves from 2.5 with HE to 8.3 using the proposed method. Experimental results indicate that the proposed method is helpful in fracture x-ray image processing.

The criterion of an evaluation method for fused images is critical to the performance of different image fusion algorithms. We present novel metrics for evaluation of fused images, based on the similarity of corresponding regions in images. The new metrics are computed on a region-by-region basis that is more suitable for evaluation, because human eyes are more sensitive to regions. The region information is represented by a feature matrix of the region, which consists of multifeature vectors including spatial information, texture, and gray value, which can adequately reflect the regional content. These make evaluation methods from the pixel level to the feature level. Research indicates that the proposed metrics are more consistent with the nature of human perception, as it considers the local image variations and the saliency of region. Experimental results show the effectiveness of the proposed metrics for the evaluation of fused images.

Secret image sharing is a popular technology to secure digital images in storage and transmission. Traditionally, the technology transforms one secret image into several images called shadows or shares. Later, when the number of collected shadows reaches a specified threshold value, the decomposed image can be reconstructed. We propose a new sharing approach to transform n secret images into n shadows. Later, after gathering all the n shadows, all the n secret images can be retrieved error-free. No information in any secret image is revealed if one shadow is absent. The total size of n generated shadows is identical to the total size of n input secret images; hence, this approach does not waste storage space. Each pixel in each secret image is reconstructed using only one Boolean, one modulus, and two mathematical operations, so it is also a fast approach for reconstructing many secret images. Comparisons are included.

In visual surveillance, robust foreground object detection is an essential step for further processing such as segmentation, tracking, and extraction of a scene's contextual information. Typical approaches continuously update background images and use then for detecting foreground objects. They involve many parameters that should be adjusted according to the situation where surveillance cameras are operating. We propose an algorithm for the robust detection of foreground objects using multiple difference images that requires only one parameter to adjust. We show that the proposed algorithm gives comparable results with less computation time through experimental results using test images with groundtruths.

A novel multiresolution analysis-based stereo matching method using curvelets, support weights, and disparity calibration is proposed. By introducing curvelet decomposition, we obtain the curvelet coefficients in different scales and orientations, and the image points can be better described and represented by these coefficients. By using support weights, the fattening effect suffered by previous methods is reduced. As a result, false matches are reduced greatly and overall accuracy is increased. Disparity calibration smoothes the disparity map and removes the remaining outliers to further improve accuracy. The proposed method is verified and compared extensively with state of the art methods, and good results and improvements are achieved.

High-sensitivity and a high-speed nanoscale measurement is an important subject in modern industry, especially when analysis of high-speed moving nanoscale objects on a surface is required. Several objectives in this direction can be achieved by using singular beam microscopy, which we investigate experimentally for the examination of small phase steps. We discuss the challenges of rigorous modeling of experiments employing high-numerical-aperture illumination and describe experimental results performed with a medium numerical aperture of 0.55. The investigated equivalent phase step heights reached as low as 10 nm (about 1/15 rad).