This PDF file contains the editorial “Refraction by Time and Technology” for OE Vol. 48 Issue 09

We propose a new multimodal biometric recognition based on the fusion of finger vein and finger geometry. This research shows three novelties compared to previous works. First, this is the first approach to combine the finger vein and finger geometry information at the same time. Second, the proposed method includes a new finger geometry recognition based on the sequential deviation values of finger thickness extracted from a single finger. Third, we integrate finger vein and finger geometry by a score-level fusion method based on a support vector machine. Results show that recognition accuracy is significantly enhanced using the proposed method.

We propose a motion vector memory reduction scheme for the H.264 spatial scalable motion estimation. The spatial scalable prediction of H.264 scalable video coding requires a significant amount of motion vector bits from the previous layer motion prediction. This motion vector causes the Internal memory size to increase, which may result in increasing hardware cost and power consumption. To reduce the memory size of the motion vector, we propose a motion vector bit-compression scheme of the interlayer motion estimation. The proposed compression scheme uses the difference value of current motion vector and previous motion vector to get a probability for entropy coding. In addition, the proposed scheme modifies a variable length coding table of the H.264 system as a simple entropy coding table. The proposed scheme reduces the motion vector-storing bit by ~66.5% with less changes in hardware size.

We present a novel high-dynamic-range (HDR) camera-based bidirectional reflectance distribution function (BRDF) measurement system that can measure the reflectance property of isotropic materials. Our developed system can measure the BRDF of highly specular materials much faster than previous systems. It measures highly dense BRDF samples for a wider reflection angle with less noise so that it provides accuracy that is necessary for computer graphics application. To estimate the reflectance of a given material, we perform an absolute photometric calibration for the HDR camera. Our system is verified by checking the Helmholtz reciprocity and comparing the performance with that of previous image-based systems. The capability and efficiency of the developed system is demonstrated by comparing the images generated by measure-and-fit and direct-rendering methods using the measured data of four different isotropic materials.

Two new types of semiconductor image position sensitive device (PSD) are proposed. One is a separate photoelectric device type of PSD that reduces image position sensing errors caused by the influence of noise light, such as background light, which cannot be removed by conventional signal light modulating methods. The other is a semiconductor dark image PSD that can detect the position of dark target image against a bright background. These new types of PSD can be realized with configurations similar to the conventional PSD. Simulation results demonstrated that the new types of PSD are effective for accurate spot image position sensing.

The effect of buffer gas pressure on the intensity and the spectral width of the 510.6-nm line of an atomic copper vapor laser (CVL) is reported. A self-discharge heated CVL tube of internal diameter 47 mm and length 1500 mm was used. The buffer gas pressure was varied from 5.0 to 470.0 mbar. A Fabry-Pérot etalon-based setup was used to measure and analyze the spectral width of 510.6-nm lines of CVL. The relative intensity and spectral width of the hyperfine components changes with operating buffer gas pressure. The buffer gas pressure reduces the number of hyperfine components (and hence overall linewidth).

A new method to achieve wideband continuously tunable delays in an all-fiber system is proposed, which uses dispersion in the optical fiber and spectrum filtering of supercontinuum generation of the ultra-short signal pulse in highly nonlinear fiber. A delay of 3.175 ns is experimentally demonstrated, and the potential delay up to 800 ns can be achieved using large dispersion fiber and wideband supercontinuum (SC) generation up to several hundreds of nanometers.

We have investigated and experimentally demonstrated high-power and stable C-band and L-band erbium-doped fiber amplified spontaneous emission (ASE) sources using a multipumping configuration, which can provide an output power of 27.16 dBm (519.99 mW) and 27.34 dBm (542.01 mW) with a power ripple of 5.9 and 1.1 dB for C-band and L-band without adding any external spectra-flattening components. Moreover, the averaged power stability of C-band and L-band erbium-doped fiber ASE source with ±0.005 and ±0.003 dB during an 8-h interval measurements at the room temperature 25 °C can be achieved, allowing high pumping efficiency of 38.5 and 36.9%.

A method that combines amplitude modulation and dispersive transmission for producing high-repetition periodic pulse trains in multiple wavelengths is proposed. The conditions satisfied by the several involved parameters for obtaining well-conformed high-contrast pulse trains are based in a generalization of the temporal Talbot effect. The basic scheme is designed to consider dense wavelength-division multiplexing pulse sequence as the input signal. In this case, periodic pulse trains with different repetition rates and a multispectra content can be obtained. Numerical results are shown to corroborate this approach, illustrating how the involved approximations affect the irradiance distribution of the output pulses.

During high bit rate information transmission through optical fiber, polarization mode dispersion (PMD) can cause several problems. PMD has been investigated with respect to birefringence, which is its major origin. The possibilities of high bit rate soliton transmission using various control mechanisms even under the presence of PMD have been reported. Such techniques will enable us to design high bit rate optical communication systems based on solitons. A mathematical model of conventional fibers with PMD is presented with a coupled nonlinear Schrodinger equation. Different soliton transmission control mechanisms such as frequency-domain control, time-domain control, and control using nonlinear gain devices have been modeled and their effects on stability of soliton pulse are studied using numerical simulations. Third-order dispersion (TOD) as a small perturbation has been introduced, and we have investigated the effects of TOD, such as soliton fission, which contributes to supercontinuum generation in a major way.

We report on a new N×N nonblocking integrated photonic switching architecture based on the novel method of nested rings. In comparison with other architectures, this new architecture shows various advantages such as reduction of the number of switching elements, maintenance of constant low-path difference loss, application of optical feedback, multidirectional port extension for monolithic integration, reduction of waveguide crossovers, and efficient use of the device area for ultracompact integrated switching networks.

We examine some fundamental theoretical limits on the ability of practical digital holography (DH) systems to resolve detail in an image. Unlike conventional diffraction-limited imaging systems, where a projected image of the limiting aperture is used to define the system performance, there are at least three major effects that determine the performance of a DH system: (i) The spacing between adjacent pixels on the CCD, (ii) an averaging effect introduced by the finite size of these pixels, and (iii) the finite extent of the camera face itself. Using a theoretical model, we define a single expression that accounts for all these physical effects. With this model, we explore several different DH recording techniques: off-axis and inline, considering both the dc terms, as well as the real and twin images that are features of the holographic recording process. Our analysis shows that the imaging operation is shift variant and we demonstrate this using a simple example. We examine how our theoretical model can be used to optimize CCD design for lensless DH capture. We present a series of experimental results to confirm the validity of our theoretical model, demonstrating recovery of super-Nyquist frequencies for the first time.

We describe one setup employed for the recording of two types of holographic screens that can be used in white-light applications. We show how to obtain holographic screens with areas up to 1370 cm2 and diffraction efficiency of 17%. We analyze the holographic screens in their relevant aspects as to focal lengths, theoretical approach, sizes, and diffraction efficiencies, specifying when each type is appropriate for particular applications.

There is an increasing need for on-site measurements in the manufacturing industry. In several cases, the shape of a work piece needs to be optically measured in high-temperature atmospheres up to 500 °C. Measurement errors caused by a lump of high-temperature air in an optical path were theoretically investigated using a model of a cylindrical lens made of air. Errors predicted by the model qualitatively explained the experimental results well. Quantitatively, the predicted errors were always larger than the experimental ones. The model was found to be useful for estimating the maximum values of the errors, which has important practical uses.

We propose a new dynamic range compression technique for infrared (IR) imaging systems that enhances details visibility and allows the control and adjustment of the image appearance by setting a number of tunable parameters. This technique adopts a bilateral filter to extract a details component and a coarse component. The two components are processed independently and then recombined to obtain the output-enhanced image that fits the display dynamic range. The contribution made is threefold. We propose a new technique for the visualization of high dynamic range (HDR) images that is specifically tailored to IR images. We show the effectiveness of the method by analyzing experimental IR images that represent typical area surveillance and object recognition applications. Last, we quantitatively assess the performance of the proposed technique, comparing the quality of the enhanced image with that obtained through two well-established visualization methods.

Since rock fractures have a strong impact on radionuclide transport and retention, fracture edge detection is very important for rock engineering. A number of rock specimens were sampled, and then the rock images were acquired for detecting the fracture edges. Edge detection in color images could be seen as detecting changes in a vector field. The quaternion convolution at different scales is applied. In addition, to suppress image noise, the dot product was computed at adjacent scales. At the same time, the gray-level difference was applied to obtain the monochromatic edges. To merge the merits of the quaternion convolution and the gray-level difference, the two results are combined. In this way, the thinned edges can be obtained by using modulus maximum suppression. Experimental results show that the proposed algorithm is efficient and robust for rock fracture edge detection.

Scalable video coding is the current standard as an extension of H.264/AVC to provide stable multimedia services for different service environments and end systems. Block motion estimation has been used to determine the best coding mode for each block type. This achieves a high coding efficiency but also creates a computationally complex encoding system. To reduce this complexity, we propose a novel algorithm for interframe coding based on a dynamic search-range control mechanism to provide a coarse-grain signal-to-noise ratio and spatial scalability. An efficient adaptation method is applied to control the search ranges of the motion estimation process according to block modes from the base layer, where the full motion vector search is used. We use an adaptive scheme based on the adaptive adjustment with mode information from the base layer. This scheme is also extended to the adaptive search range in the base layer. We verify that the overall encoding time can be reduced ~84% based on a comparative analysis of experimental results using JSVM 9.12 reference software.

A novel switching-based filter is proposed to suppress the impulse noise and preserve the fine details in the color image. The filtering method is divided into two stages, the noise detection and the noise cancellation. In the first stage of noise detection, pixels with similar color components in many neighboring positions are counted to see whether the current pixel is corrupted by impulse noise. In the second stage of noise cancellation, the previous outputs and the detected noise-free pixels are chosen as the samples of the vector median filter operation to improve the performance on suppressing impulse noise. Several experimental results have demonstrated that the proposed filter outperforms many filters in terms of both noise suppression and detail preservation.

Watermarking is a very important technique for protecting the authorization of digital content, such as still images, video streams, audio streams, and 3-D models. Most fragile watermarking schemes for 3-D models are not reversible. Published reversible or irreversible fragile watermarking schemes for 3-D models have many drawbacks, such as the causality problem, not being blind, or being unable to locate changed regions. To overcome these drawbacks, a reversible fragile watermarking scheme for 3-D models in spatial domain is proposed. Principal component analysis (PCA) is employed to produce the PCA coordinate system and make the system robust against similarity transformation attacks. PCA, together with a novel interval embedding technique, provide the blind reversibility of the proposed scheme. Intervals larger than a threshold and smaller than another threshold are adopted as legitimate to avoid large distortion. Moreover, experimental results show that the proposed scheme can overcome the causality, convergence, and confusion problems; provide both tampering detection and better embedding rate and requiring a small key size.

Broadband optical modulators, especially the LiNbO3 interferometric types, are currently important in the generation of advanced modulation formats for operating bit rate in the 100 Gb/s range for 100-Gb/s optical Ethernet networks. In these devices the effectiveness of generation of the traveling electric field for electro-optic interaction is very critical. This work presents the modeling of the tilted wall of traveling wave electrodes and their impacts on the operating bandwidth over interferometric optical waveguide structures and modulators. The effects of the tilt of thick electroplated electrodes on the device bandwidth are significant. The electro-optic overlap integral can be evaluated with tilt electrodes. Key features for optimization of the electro-optic overlap integral are studied to realize modulators of low half-wave driving voltage and fabrication of optical modulators under limited etching facility. Experimental demonstration of the effects of tilted electrodes on the performance of a Mach-Zehnder interferometric modulator is given to confirm simulation results.

Adaptive methods are defined and experimentally studied for a two-scale edge detection process that mimics human visual perception of edges and is inspired by the parvocellular (P) and magnocellular (M) physiological subsystems of natural vision. This two-channel processing consists of a high spatial acuity/coarse contrast channel (P) and a coarse acuity/fine contrast (M) channel. We perform edge detection after a very strong nonlinear image enhancement that uses smart Retinex image processing. Two conditions that arise from this enhancement demand adaptiveness in edge detection. These conditions are the presence of random noise further exacerbated by the enhancement process and the equally random occurrence of dense textural visual information. We examine how to best deal with both phenomena with an automatic adaptive computation that treats both high noise and dense textures as too much information and gracefully shifts from small-scale to medium-scale edge pattern priorities. This shift is accomplished by using different edge-enhancement schemes that correspond with the P- and M-channels of the human visual system. We also examine the case of adapting to a third image condition-namely, too little visual information-and automatically adjust edge-detection sensitivities when sparse feature information is encountered. When this methodology is applied to a sequence of images of the same scene but with varying exposures and lighting conditions, this edge-detection process produces pattern constancy that is very useful for several imaging applications that rely on image classification in variable imaging conditions.

As a global feature of fingerprints, the orientation field plays an important role in automatic fingerprint identification systems. Although many algorithms have been proposed for orientation field estimation, the results are not so satisfactory and the computational cost is expensive. In this work, a novel algorithm based on a straight-line model of ridge is proposed for the orientation field estimation. The algorithm comprises four steps: preprocessing the original fingerprint image, determining the primary and secondary ridges of the fingerprint foreground block using the top semineighbor searching algorithm, estimating the block direction based on a straight-line model of such a primary ridge, and correcting the spurious block directions. The proposed algorithm is suitable for all types of fingerprints. Experimental results show that it achieves satisfying estimation accuracy with high computational efficiency. A further experiment shows that it is more accurate and robust to noise compared with previous works, and can improve the performance of a fingerprint recognition system.

Purely rotation-based self-calibration receives the most attention among various self-calibration methods, owing to its algorithmic simplicity. However, it is actually impossible to ensure that the camera motion for this kind of self-calibration is a pure rotation, since the rotation center should-but unfortunately may never-completely coincide with the optical center with an unknown position. Almost all conventional pure rotation methods tend to ignore any translation, so the significant errors of calibration results could be inevitably introduced. We propose a practical and effective approach to improve the purely rotation-based self-calibration approach. The proposed approach accounts for translational offsets. According to the fact that the rotational angles between camera orientations have a very strong impact on the calibration errors from the translations, we compute the relative camera orientations prior to calibrating, then use different and very appropriate strategies for self-calibration in different angle circumstances, to achieve better calibration results. Both synthetic data and real data are used to test the proposed approach and very good results are obtained. Comparing the experimental results with those of conventional methods, the proposed approach significantly yields higher accuracy, and therefore reduces the calibration errors by the translations.

A phase-only encryption/decryption scheme with the readout based on the zeroth-order phase-contrast technique (ZOPCT), without the use of a phase-changing plate on the Fourier plane of an optical system based on the 4f optical correlator, is proposed. The encryption of a gray-level image is achieved by multiplying the phase distribution obtained directly from the gray-level image by a random phase distribution. The robustness of the encoding is assured by the nonlinearity intrinsic to the proposed phase-contrast method and the random phase distribution used in the encryption process. The experimental system has been implemented with liquid-crystal spatial modulators to generate phase-encrypted masks and a decrypting key. The advantage of this method is the easy scheme to recover the gray-level information from the decrypted phase-only mask applying the ZOPCT. An analysis of this decryption method was performed against brute force attacks.

This PDF file contains the errata for “OE Vol. 48 Issue 09 Paper OE ERR-SEP2009-1” for OE Vol. 48 Issue 09