This PDF file contains the editorial “Change in 2010” for OE Vol. 49 Issue 01

A highly stabilized dynamic displacement measurement system, which employs fiber Bragg gratings to interleave two fiber Michelson interferometers that share the common interferometric optical path, is presented. The phase change in the interferometric signals of the two fiber Michelson interferometers is tracked respectively by maintaining the phase difference in quadrature with two electronic feedback loops. One of the fiber interferometers is used to stabilize the system by the use of an electronic feedback loop to eliminate the influences that result from the environmental disturbances, while the other fiber interferometer is used for the measurement by employing another electronic feedback loop to track the phase change in the interferometric signal. The system is able to measure dynamic displacement and provide a sense of direction of the displacement at the same time. The dynamic displacement with frequencies ranging from 0.1 Hz to 200 Hz and with a maximum amplitude of 60 µm can be measured, and the measurement resolution can reach 10 nm.

A particle sizing algorithm is developed for nanoparticle sizing with laser Doppler anemometry/velocimetry systems. A model-based signal processing method is used to estimate the particle size from the autocorrelation curve corresponding to a single particle transit. Two kinds of figures of merit functions are combined to improve the sensitivity. The optimal setup parameters (refractive index, wavelength, and observation direction) and trajectory error are investigated in independent simulation studies. At 514-nm illumination wavelength, the most sensitive size region is found below 300 nm down to the sizing limit (20 photons on average from a single particle transit). The required laser power is searched for by the lower sizing limit based on the calibration measurement. The size estimation of a polystyrene sphere particle of 50 nm diameter requires at least 123-kW/cm2 laser power density at 350 nm, while 587 kW/cm2 at 514 nm is used in the studied system.

A microlens array optic was fabricated for laser surface microstructuring of polymer surfaces. The optic contains a hexagonal close-packed monolayer of SiO₂ microspheres, held together by an adhesive substance and supported on fused silica glass. The array is placed in direct contact with the target substrate and is exposed to UV light at a wavelength of 193 nm. During this exposure, the SiO₂ spheres act as microlenses, which focus the incoming laser light, but also enhance the optical near-field intensity underneath each microsphere. A large number of identical structures are produced simultaneously using this type of direct laser ablation, which leads to a highly efficient process. The ablated holes are approximately 1.8 μm in diameter, with a pitch of 8.4 μm and a depth of 80 nm. This microlens array has many advantages over other types of array, including the fact that it is inexpensive and easy to fabricate. An important feature is that it can transmit light at a wavelength less than 300 nm, which makes it suitable for laser surface patterning.

Ongoing tests involving the application of double optical feedback to a vertical-cavity surface-emitting laser (VCSEL) are resulting in demonstrable and significant improvements in oscillation linewidth and frequency stability. We look into the workings of a double optical feedback system for a Fabry-Pérot-type diode laser. We describe a single-mode VCSEL that is characterized by a narrow oscillation linewidth and a stable output intensity that shows no trace of the low-frequency fluctuation (LFF) that so often occurs in single optical feedback diode lasers. Initial tests use a beat note to do this. From there, we calculate the square root of the Allan variance to determine the level of frequency stability. We also evaluate the degree of LFF suppression achieved using its spectrum density and compare those results with what we obtained through single and double optical feedback and with no feedback whatsoever.

We present an efficient laser welding assembling sequence for minimizing the misalignment from the postweld shift in butterfly packages during fiber-to-semiconductor laser coupling. The misalignment from the postweld shift that arises during the welding of a nickel clip and metal ferrule can be compensated by an optimal initial shift prior to Nd:YAG laser welding and by a mechanical adjustment prior to the laser hammering process. As a result, the number of laser hammering sequences required to compensate for misalignment are significantly reduced.

An optical accelerometer with a bulk-micromachined silicon proof mass and a microfiber loop resonator (MLR) sensor was developed. The MLR was fixed on the surface of the cantilever beam. The proof mass and cantilever beam were fabricated with a two-mask process. An accelerometer with a range of ±20 g and output sensitivity 624.7 mV/g was fabricated. The design, simulation, fabrication, and preliminary results are presented.

The growing need for underwater observation and subsea monitoring systems has stimulated considerable interest in advancing the enabling technologies of underwater wireless communication and underwater sensor networks. This communication technology is expected to play an important role in investigating climate change, in monitoring biological, biogeochemical, evolutionary, and ecological changes in the sea, ocean, and lake environments, and in helping to control and maintain oil production facilities and harbors using unmanned underwater vehicles (UUVs), submarines, ships, buoys, and divers. However, the present technology of underwater acoustic communication cannot provide the high data rate required to investigate and monitor these environments and facilities. Optical wireless communication has been proposed as the best alternative to meet this challenge. Models are presented for three kinds of optical wireless communication links: (a) a line-of-sight link, (b) a modulating retroreflector link, and (c) a reflective link, all of which can provide the required data rate. We analyze the link performance based on these models. From the analysis, it is clear that as the water absorption increases, the communication performance decreases dramatically for the three link types. However, by using the scattered light it was possible to mitigate this decrease in some cases. It is concluded from the analysis that a high-data-rate underwater optical wireless network is a feasible solution for emerging applications such as UUV-to-UUV links and networks of sensors, and extended ranges in these applications could be achieved by applying a multi-hop concept.

We consider M-ary signaling in page-oriented holographic storage systems that multiplex pages using three methods: conventional angular multiplexing throughout the volume, localized recording, and a combination of angular multiplexing within localized recording. We study the mutual information transfer, which is increasingly easy to achieve in practice, between the recorded and recovered data, and use it to assess the storage density in these systems. We use the existing holographic channel model for the dominant Rician noise case for deriving the mutual information bound on the capacity and examine the interplay between the storage density and the number of recorded pages within the medium. We quantify through information-theoretical analysis that it is possible to obtain considerably higher storage capacities using gated localized holography than what can be achieved in conventional volume holography with angular multiplexing by appropriately optimizing the number of intensity levels for a given material constant and signal-to-noise ratio.

We propose a novel method for monitoring the drying process of a painted surface by using phase-shifting digital holography. In comparison with previous methods using speckle patterns, the proposed method can afford an intensity image for directly monitoring and local variations of drying without an imaging lens. It can also be used for surfaces of complex shapes. In addition, quantitative analysis utilizing a cross-correlation function and phase change derived from the reconstructed complex amplitude is performed and the drying time of paint for different areas and temperature is evaluated. The technique is also applied to monitoring the drying process of a complex surface of a lightbulb.

Colorization is the process of adding colors to monochrome images. In this paper we present a scribble-based colorization, which uses nearest neighborhood propagation and mixed weighing. The major assumption of our method is that chrominance is similar if luminance is similar in a natural image. We introduce the definition of the nearest neighborhood and mixed weighting. Non-local-mean-based patch weight and point weight are used in the mixed weighting. Experimental results show the benefits of our method.

This paper presents an adaptive image retargeting approach using saliency-based continuous seam carving to efficiently display images on small screens. A multiscale contrast-based saliency map is first generated and used as the energy map for conventional discrete seam carving, and a reasonable number of seams are adaptively extracted. Then the reduced dimensions allocated to continuous seam carving (CSC) and possible scaling are determined by the analysis of the energy curve of the extracted seams. The proposed CSC assigns to each extracted seam a reserving ratio in accordance with the corresponding seam energy and the reduced dimension, and the retargeted image is generated using an efficient scheme of mapping and resampling based on the reserving ratio map. Experimental results demonstrate better retargeting performance of the proposed approach under different reduction ratios.

By considering edge similarity of images sensed in different wave bands of the same landform, a novel image registration method using edge correlation as the similarity measure is proposed. Edge correlation involves spatial information of images, which reflects well their structures. We employ significant edge curves with long length, instead of isolated edge points, to calculate the correlation which makes the proposed method more robust to noise. Experimental results prove that, for images corresponding to the same landform, edge correlation nearly always yields a single sharp peak at the correct alignment parameters, and the proposed method has more accurate registration results than mutual-information-based methods, especially under noisy conditions.

We present a new impulsive noise removal method, which combines a switching mechanism and adaptive weighted median filtering techniques. By utilizing four Laplacian operators and median-based comparison techniques to classify the image pixels into thin-line pixels, noise-free pixels, and noisy ones, the developed solution applies adaptive weighted median filtering operations only in the detected noisy locations to suppress impulsive noise, and keeps the other pixels unchanged. The simulation results exhibit the excellent performance gains of the proposed solution in suppressing impulsive noise with different contamination ratios over other prior-art methods in terms of both objective measurements and visual image quality.

We focus on the automatic detection and classification of players in a football match. Our approach is not based on any a priori knowledge of the outfits, but on the assumption that the two main uniforms detected correspond to the two football teams. The algorithm is designed to be able to operate in real time, once it has been trained, and is able to detect partially occluded players and update the color of the kits to cope with some gradual illumination changes through time. Our method, evaluated from real sequences, gave better detection and classification results than those obtained by a system using a manual selection of samples to compute a Gaussian mixture model.

The analysis of motion information is one of the main tools for the understanding of complex behaviors in video. However, due to the quality of the optical flow of low-cost surveillance camera systems and the complexity of motion, new robust image-processing methods are required to generate reliable higher-level information. In our novel approach there is no need for tracking objects (vehicles, pedestrians) in order to recognize anomalous motion, but dense optical flow information is used to construct mixtures of Gaussians, which are analyzed temporally. We create a multilevel model, where low-level states of non-overlapping image regions are modeled by continuous hidden Markov models (HMMs). From low-level HMMs we compose high-level HMMs to analyze the occurrence of the low-level states. The processing of large numbers of data in traditional HMMs can result in a precision problem due to the multiplication of low probability values. Thus, besides introducing new motion models, we incorporate a scaling technique into the mathematical model of HMMs to avoid precision problems and to get an effective tool for the analysis of large numbers of motion vectors. We illustrate the use of our models with real-life traffic videos.

Defective rollers in rolling plants often create spatially periodic defects on the product surface. It is essential for operators to receive early warnings of such periodic defects and take appropriate action to avoid a large quantity of defective products. We present a robust and efficient real-time method for inspecting periodic defects in continuous steel wire rods. The proposed inspection method consists of two parts: (1) an algorithm for detecting all defect candidates and (2) an algorithm to detect periodicities in the detected defect candidates and to determine their periods. The first algorithm exploits the translation-invariant property of the Haar undecimated discrete wavelet transform to improve the signal-to-noise ratio of the surface image. The second algorithm is based on analysis of the frequency spectrum of defect candidate positions. It identifies periodicities of the defect candidates by finding repeating impulse-like spectra. The inspection system using the proposed method is applied to a real production line and detects periodic defects in real time and identifies their periodicities with high accuracy.

In multicamera surveillance systems, tracking the same person across multiple cameras is an important technique. It is also desirable to recognize the individuals who have been previously observed with a single-camera monitor. This paper addresses this problem by recognizing the same individual in different tracks. The method that represents an object image using a bag of features has been commonly used in image retrieval and classification. In this paper, that approach is adapted for people image description, and support vector machines are employed for high classification performance. To get more reliable matches and support supervised learning in online operation, we propose a decision scheme to distinguish previously unseen individuals from recurrences so that the new classes can be automatically labeled. On this basis, an online recognition framework that applies incremental learning is also presented. We get promising results from the evaluation with more than 200 tracks of 70 different people.

Three-dimensional articulated human motion tracking is challenging due to the high-dimensional parameter space and poor image observations. When particle swarm optimization (PSO) is used for human motion tracking, due to unreliable image likelihood, particles may be misled and be unable to find the most plausible pose space. This paper proposes a new PSO-based algorithm for human motion tracking, annealed PSO-based particle filter (APSOPF). The sampling covariance and annealing factor are incorporated into the velocity-updating equation of PSO; they are initialized with appropriate values at the beginning of the PSO iteration, and decreased (annealed) in reasonable steps. Through the sampling covariance, the motion prior is introduced into APSOPF, constraining particles to the most likely region of pose space and reducing the generation of invalid particles. By adopting decreasing coefficients in the updating principle, the leading effects of the local and global best on particles decrease with generations, making particles preserve their own divergence and self-exploration capabilities before convergence. Hence the problem of insufficiently reliable image likelihood can be mitigated in some degree. We compare APSOPF quantitatively with an annealed particle filter and a standard particle filter on the challenging HumanEvaI data set. Experimental results show that the proposed algorithm achieves lower estimation error in tracking real-world 3-D human motion.

With modern lithographic technology, a compact spectrometer is designed to include a blazed micro-grating with cylindrical concave grating profile. In order to restrict the sagittal beam divergence and to reduce the size of the spectrometer, the micro-grating is embedded inside a pair of planar mirrors used as a slab waveguide. In the simulations for the effect of the waveguide, we discover that the focal pattern distortion introduced by the waveguide causes a blunted and side-tailed peak in the spectrum. The distortion can be managed by allowing some gap between the edge of the waveguide and the image sensor. Such a configuration has greatly improved the resolving power of the micro-grating in this compact system.

Proposed is silicon-photonics-based phased array antenna beamforming for high-resolution long-range radars with wide instantaneous radio frequency (rf) bandwidth. Specifically, the proposed silicon-photonics beamformer platform offers the potential for cost-effective monolithic chip-scale integration of photonic delay lines, 2×2 optical switches, variable optical attenuators, and optical amplifiers that form the base unit of a rf transmit/receive array signal processor. In effect, the proposed silicon-photonics devices empower the design of a powerful proposed photonic beamformer with one time-delay unit per antenna element. Device-level designs studies are shown that promise meeting the high-resolution radar mission-critical requirements via time delays of up to 2.5 ns, switching times of less than 100 ns, optical isolations as good as 50 dB, and optical gains of up to 6 dB. Longer delays are achieved off chip using optical fibers.

This PDF file contains the errata for “OE Vol. 49 Issue 01 Paper OE ERR-JAN2010-1” for OE Vol. 49 Issue 01