This PDF file contains the editorial “2009 in Review” for OE Vol. 49 Issue 02

A fast directional discrete cosine transform (FDDCT) is proposed for efficient representation of anisotropic edges in images. The transform is performed on the predefined direction lines similar to the intraprediction mode in H.264. Comparing to the directional discrete cosine transform (DDCT) now available, no interpolation is needed in FDDCT; thus, the amount of computation decreases by 80%. Simulation results indicate that the peak signal-to-noise ratios of images compressed using FDDCT are >1 db higher than those using DDCT.

An external-cavity laser diode that performs static wavelength scanning eliminates problems such as repeatability and tuning rate that arise due to mechanical movements induced in the external cavity of conventional systems, because it requires no mechanical elements. Experiments reveal that the scanning range and tuning rate are 1.1 nm and 1 kHz, respectively.

An object tracking algorithm using an adaptive Kalman filter (KF) combined with mean shift (MS) is proposed. First, the system model of KF is constructed, then the center of the object predicted by KF is used as the initial value of the MS algorithm. The searching result of MS is fed back as the measurement of the adaptive KF, and the estimate parameters of KF are adjusted by the Bhattacharyya coefficient adaptively. The proposed method has the robust ability to track a moving object in consecutive frames under certain real-world complex situations, such as a moving object disappearing partially or totally due to occlusion, fast moving objects, and sudden changes in velocity of a moving object. The experimental results demonstrate that the proposed tracking algorithm is robust and practical.

We propose a programmable apodizer using a digital micromirror device and the total-internal-reflection prism subsystem for incoherent imaging systems. It is shown that the proposed programmable apodizer can extend the depth of focus with the specific shaped aperture generated by the digital micromirror device. With a scale ratio of K0.05, one can achieve almost the same level of imaging quality as provided by the conventional annular apodizer, where K represents the ratio between the integer multiple of the micromirror's square pixel size and the diameter of the effective aperture stop.

The conventional scalar imaging theories that are represented in the Fresnel-Kirchhoff diffraction formula or the Rayleigh-Sommerfeld diffraction formulae involve contradictions. By introducing incoming inclination factors not only for the diffraction surface but also for the image plane, we propose a new equation that fulfills both the self-consistency and the reciprocity theorem. We also confirm the validity of this new equation by both theoretical discussions and numerical calculations.

We report a multispectral imaging microscope with dynamic spectral reconfiguration capability. It operates based on a spatial filtering principle. The objective lens images the test specimen onto a dispersive grating surface. A dynamic spatial filter located at the Fourier plane of the 4-f lens group is used to select the desired spectral channel and spectral width for each spectral image diffracted by the grating. The reconfiguration capability enables the optimal spectral band selection for a specific application without hardware component modification. Successful experimental results validate the microscopic multispectral imaging configuration for practical applications.

We demonstrate a method to solve the main problem involved in lattice design for subaperture stitching interferometry. That is calculation of the aspheric departure of a subaperture whose location is given arbitrarily. The simulated measurement data with unknown phase values are transformed into the global model frame, which satisfy the nominal surface equation. Then the phase values can be solved and used to calculate the aspheric departure with piston, tilts, and power removed. Accordingly, the subaperture lattice is determined with preferred interferometer parameters.

We propose a common-path two-wavelength interferometric system based on a single optical element, a Savart plate, that is able to obtain single-shot profile measurements with submicron precision from safe working distances (beyond 100 mm). These characteristics make this sensor ideal for surface inspection in on-line applications. For the illumination branch, two lasers with close wavelengths are combined and then passed through a rotating holographic diffuser for drastic speckle reduction. In the acquisition branch, the interferometric signals of both wavelengths are captured simultaneously by a camera, and their phase signals are combined to extend the measurement range.

A master-oscillator fiber power amplifier system with a 4.5-m-long Yb³⁺-doped homemade large-mode-area double-clad fiber is reported. Up to 156 W average power of 1064 nm amplified pulse, corresponding to a slope efficiency of 64.9%, has been demonstrated. The amplified pulse possesses a pulse duration of 24 ns and a repetition rate of 50 kHz and demonstrates a good beam quality (M=_x².81 and M_y²=2.66), although no special transverse-mode-controlling techniques were adopted.

Speckle, severely affecting the image quality in laser projection, would arise when coherent lights are scattered from a rough surface. Vibrating or rotating a diffuser or a diffractive optical element, the conventional method of speckle suppression (hereinafter refered to as "the conventional method"), does reduce the speckle, however, also causes energy loss. The incompatible relationship between speckle suppression and energy preservation, reflected by using the conventional method, is analyzed theoretically and practically. In order to achieve both speckle suppression and energy preservation, a novel method, rotating a light pipe, which is in principle by averaging independent speckle patterns (hereinafter refered to as "the novel method"), is proposed and demonstrated from theoretical and experimental aspects. Experimental results indicate that the novel method degenerates coherence of the source, keeps polarization of the source, brings the speckle contrast down to 3.45%, and preserves >90% energy.

A ridge waveguide Bragg grating pressure or touch sensor is proposed. The sensor consists of an open-top ridge waveguide Bragg grating with an overlaid pressure sensing polydimethylsiloxane film. The effective index of the guided mode of the waveguide is changed by stress-induced variations in the film refractive index that are caused by increases in pressure normal to the waveguide. Pressure is then measured by monitoring the shift of the Bragg resonance resulting from the changes to the effective index. By using the smaller core size ridge waveguide, and a polymer with smaller Young's modulus, the sensitivity of the sensor is enhanced. By utilizing the polarization dependence of the sensor response, a temperature-independent pressure sensor can be realized.

An improved demodulation method for the phase-generated carrier (PGC) system by eliminating laser-intensity modulation (LIM) is proposed. The influence of LIM is analyzed theoretically and experimentally. Two parameters are used to describe the effect of LIM: the LIM coefficient (LIMC) and the LIM phase delay (LIMPD). Good stability of the LIMC and LIMPD is confirmed by experimentation with an actual system. The demodulation signal using the traditional method has a much greater higher harmonic component than the improved method due to LIM. The increase of the signal-to-total-harmonic ratio (SHR) using the improved method is >23 dB, and there is a corresponding improvement of 19 dB to the signal to noise and distortion (SINAD) and signal-to-noise ratio (SNR). A new prototype system using the improved PGC method for marine seismic sensing capable of demodulating multiple channels in parallel, simultaneously, is demonstrated. The SHR is stable at 56 dB when the LIMC is <0.5. Similar results are obtained for the SINAD and SNR. The demodulated signal's upper limit is ~100 rad at 100 Hz and 12 rad at 1 kHz, giving a dynamic range reaching 130 dB at 100 Hz. The system's SINAD is stable within 1 dB, whereas the SHR is stable within 2 dB in field application.

We propose a novel multilevel wavelength-division multiplexing optical network based on the concept of self-similarity to simplify network structure and operation. Our approach lies on a simple network topology as well as an efficient wavelength management scheme being uniformly applied to all network levels. The proposed network is a compound packet-switched and wavelength-routed network with packet switching performed on the bottom level and wavelength routing on all upper levels. This network retains the efficiency of packet-switched networks and the simplicity of wavelength-routed networks. Switching operations are concentrated at some special nodes in the multilevel network, significantly simplifying the node configuration and wavelength routing. Moreover, the idea of bands is applied to unify wavelength management on all network levels. Network analysis is performed to assess the feasibility of our approach. A queueing model using the quality of service enhanced optical burst switching protocol is employed to analyze the blocking performance of the proposed network. Also, the numerical results based on the queueing model are provided.

The current limitation in pixel count of a single spatial light modulator (SLM) is one of the technological hurdles that must be overcome to produce a holographic 3-D display with a large image size. A conventional approach is to tile subholograms that are predivided from a reconfigurable computer-generated hologram (CGH) with a high pixel count. We develop a new approach to achieve a 50 Mpixel display by tiling reconstructed subholograms computed from a predivided 3-D object. The tiling is done using a two-axis scanning mirror device with a new tiling sequence. A shutterless system design is also implemented to enable effective tiling of subholograms. A high-speed digital micromirror device (DMD) at 6 kHz with 1920×1080 pixels is utilized to reconstruct the subholograms. Our current system shows the potential to tile up to 120 subholograms, which corresponds to about 240 Mpixels. The approach we demonstrate gives a scalable solution to achieve a gigapixel-level display in the future.

Although optimal truncation of JPEG2000 compressed imagery provides an image of the highest quality per bit rate in terms of peak signal to noise ratio, the algorithm is highly computationally inefficient because of the removal of compressed image sections that have been previously calculated. The proposed idea utilizes a simple quantization technique prior to Tier I coding to remove many of the coding passes from the imagery that would not become a part of the final compressed bit stream. Two methods based on the this idea are discussed. The first method restricts the quantization value to be a power of 2, effectively eliminating the least significant bits of each code block through the quantization step. The second method relaxes the 2ⁿ restriction. Both methods give substantial reduction in computational complexity, a 39% and 46% reduction in overall complexity at 0.25 bits per pixel, respectively. The first method gives an equivalent rate distortion curve as traditional optimal truncation, and the second gives a similar rate distortion curve, only moderately underperforming traditional optimal truncation in a few images at few bit rates.

A multiview video-based three-dimensional (3-D) video system offers a realistic impression and a free view navigation to the user. The efficient compression and intermediate view synthesis are key technologies since 3-D video systems deal multiple views. We propose an intermediate view synthesis using a rectangular multiview camera system that is suitable to realize 3-D video systems. The rectangular multiview camera system not only can offer free view navigation both horizontally and vertically but also can employ three reference views such as left, right, and bottom for intermediate view synthesis. The proposed view synthesis method first represents the each reference view to meshes and then finds the best disparity for each mesh element by using the stereo matching between reference views. Before stereo matching, we separate the virtual image to be synthesized into several regions to enhance the accuracy of disparities. The mesh is classified into foreground and background groups by disparity values and then affine transformed. By experiments, we confirm that the proposed method synthesizes a high-quality image and is suitable for 3-D video systems.

A novel H.264 advanced video coding fragile watermarking method is proposed that enables the authenticity and integrity of the video streams to be verified. The effectiveness of the proposed scheme is demonstrated by way of experimental simulations. The results show that by embedding the watermark information in the last nonzero-quantized coefficient in each discrete cosine transform block, the proposed scheme induces no more than a minor distortion of the video content. In addition, we show that the proposed scheme is able to detect unauthorized changes in the watermarked video content without the original video. The experimental results demonstrate the feasibility of the proposed video authentication system.

The H.264/AVC (advanced video coding) is used in a wide variety of applications including digital broadcasting and mobile applications, because of its high compression efficiency. The variable block mode scheme in H.264/AVC contributes much to its high compression efficiency but causes a selection problem. In general, rate-distortion optimization (RDO) is the optimal mode selection strategy, but it is computationally intensive. For this reason, the H.264/AVC encoder requires a fast mode selection algorithm for use in applications that require low-power and real-time processing. A probable mode prediction algorithm for the H.264/AVC encoder is proposed. To reduce the computational complexity of RDO, the proposed method selects probable modes among all allowed block modes using removable SKIP mode distortion estimation. Removable SKIP mode distortion is used to estimate whether or not a further divided block mode is appropriate for a macroblock. It is calculated using a no-motion reference block with a few computations. Then the proposed method reduces complexity by performing the RDO process only for probable modes. Experimental results show that the proposed algorithm can reduce encoding time by an average of 55.22% without significant visual quality degradation and increased bit rate.

A redundant picture is one of the H.264/AVC tools for increasing error resiliency when video is delivered over error prone environments. We present a loss-aware redundant picture allocation method that determines whether the redundant picture is inserted for each primary coded picture or not. The determination is based on an error rate of transmission network and the distortion of decoded picture caused by the error. Simulation results showed that the proposed method alleviates the distortion and, thereby, it achieves higher quality of the decoded picture than the conventional methods, including the hierarchical redundant picture. In particular, the proposed method produces outstanding results at low bit rates; thus, the method is highly applicable to low bit-rate wireless video transmission.

Detecting foreground objects from image sequences has played an important role in many machine vision applications. Background modeling, which is a preliminary processing step for foreground detection, is a challenging task due to the complexity and variety of background regions, unexpected situations, and image artifacts such as noise factors, impairments, etc. In this work, we propose a pixel-based background modeling method that uses nonparametric kernel density estimation and foreground/background classification based on the Bayesian decision rule. To reduce the complexity of the kernel density estimation technique, we estimate the probability density function for the background regions using histograms. Hue, saturation, and value (HSV) color and gradient information is also used to represent the background features. After the background statistics are estimated, we detect the foreground regions by using a background subtracting method based on the Bayesian decision rule, which eliminates the need to select and tune the threshold value for foreground/background region classification. The proposed algorithm is validated using datasets acquired in indoor and outdoor environments with a fixed camera. The proposed algorithm is quantitatively compared with two existing background modeling methods. The experimental results show that the proposed algorithm produces more accurate and stable results.

We present an abandoned luggage detection architecture that consists of an intelligent surveillance system for public places. Detection of abandoned luggage is necessary because unattended or abandoned luggage can be used as a means of terrorist attack, especially for bombs. Our proposed system relies on three modules: moving object detection, object tracking and classification, and event recognition. We focus on abandoned luggage detection. To recognize an abandoned luggage event, we constructed the finite state automaton (FSA), in which each FSA state represents a certain luggage status. The proposed algorithm shows good performance in a real-world environment and also works at real-time speed.

Stereoscopic technologies continue to accelerate the adoption of 3-D in both professional and consumer applications. Stereo 3-D displays have the potential to benefit geospatial intelligence, complex visualization, pharmaceutical development, petroleum exploration, medicine, entertainment, architecture, simulation, and other difficult tasks. A single-mirror dual monitor stereoscope system that can offer the full resolution of the current LCD display for 3-D viewing is proposed. This new approach utilizes an isosceles trapezoid mirror and two monitors to provide a cost-effective approach for stereoscopic viewing. Mathematical formulas for the design of the compact mirror were derived based on a novel scheme, and an implementation of the system was conducted to verify the practicability of the proposed method. We believe its compactness, low cost, and high image quality can become a very competitive choice among various display techniques currently available.

Page-oriented volume holographic memories (POVHM) is a quadratically nonlinear channel because of the intensity detection at its output. To combat the two-dimensional intersymbol interference in a high-capacity POVHM, equalization of the output intensity array requires identification of the quadratic and possibly spatially varying impulse response of the channel. Although conventional adaptive filtering schemes are devised for identification of linear channels, they also require the length of the impulse response to be known in advance. In this work, we develop multistage quadratic normalized least mean square (LMS) (MS-QNLMS) adaptive filtering and multistage Volterra normalized LMS (MS-VNLMS) filtering to estimate the channel under quadratic nonlinearity, which do not require the support or length of the impulse response to be known a priori. By employing extensive numerical experiments, we provide performance and convergence comparisons of the proposed schemes with respect to a true-order quadratic estimator. We also show that MS-QNLMS filtering has less computational complexity and converges faster and more robust to various channel parameters as compared to MS-VNLMS.

This PDF file contains the errata for “OE Vol. 49 Issue 02 Paper OE ERR-FEB2010-1” for OE Vol. 49 Issue 02