This PDF file contains the editorial “The Abstract as a Marketing Tool” for OE Vol. 49 Issue 07

The final optical design for a space-borne light detection and ranging (lidar) mission is presented, in response to the European Space Agency "Advanced lidar concepts" proposal for use of a differential absorption lidar system to measure water vapor distribution in atmosphere at 935.5 nm. The telescope adopts a double afocal concept (i.e., four reflections with two mirrors) using a lightweight and large aperture primary mirror. It is derived from a feasibility study that compares several different optical configurations, taking into account parameters such as cost, dimensions, complexity, and technological feasibility. The final telescope optical design is described in detail, highlighting a trade-off with other solutions and its optical tolerances.

A fiber-and-LED-based vehicle headlamp is presented in which light rays emitted from multiple high-power LEDs are gathered using a light collector and then guided into a projector lamp via an optical fiber. This proposed headlamp is intended to reduce the lamp size and the heat-dissipation problem simultaneously. Detailed geometric analysis of the headlamp is given, and the optical efficiency for each component part is also calculated using a TracePro program. The computer simulation results show that the headlamp can produce a legal Economic Commission for Europe low-beam pattern with a total optical efficiency up to 49.4%, and only eight 5-W LEDs (120 lm each) are required.

Even though odd-order aspherical surfaces have sometimes been used in optics, their meaning and effectiveness have not been discussed enough to be fully understood. However, we have already discussed and derived mathematically that odd-order aspherical surfaces cannot be represented in the form of a power series of even-order even when rotationally symmetric. We have also explained that this result does not contradict the fact that the set of Zernike's circle polynominals forms a complete system and that their rotational symmetric terms consist only of even-order terms of radial coordinates. First, we reconsider these mathematical discussions. Second, we reveal that the first- and third-order aspherical surfaces are valuable in practical lens designing for catoptoric projection optics of extreme ultraviolet lithography.

A technique is described for the continuous variation of the resultant retardance and effective privileged directions of a cascaded system of three optical retarders. The system consists of a rotatable retarder sandwiched between two fixed, identical, parallel retarders. The primary aim of the study was to develop a simple technique for a variable retarder for monochromatic light, but the robustness of the system for a narrow band on either side of the design wavelength was also studied. Simulated plots show that a linear variation of the effective retardance from 0 to 2Π is achievable, as is a linear variation of the effective azimuth from 0 to Π. It is also shown that these two parameters may be varied independently of each other.

In many control systems, the most effective method to improve the performance of the closed-loop system is by enhancing the gain of the control system, which results in a wide control bandwidth. However, in the control system of a charge-coupled-device-based tracking loop for a fast steering mirror, the bandwidth of the closed loop is greatly limited by the large time delay of the TV tracker. Additionally, the time delay leads to instability of the system when the closed-loop system has high gain. We propose a new feedforward control to compensate some errors related to the time delay of the tracker, meanwhile improving the performance of the closed-loop fast steering mirror system. The control structure we propose includes two closed loops; a tracking loop and a fast position loop. The fast position loop is produced using an eddy current sensor, and the tracking loop is the outer loop, enveloping the fast position loop. The feedforward signal is estimated from the signal of the eddy current sensor and the TV tracker, which is added to the input of the fast position loop. Experimental results show that our proposed feedforward system can effectively enhance trajectory tracking and pointing performance.

Parametric cost models are routinely used to plan missions, compare concepts, and justify technology investments. Unfortunately, there is no definitive space telescope cost model. For example, historical cost estimating relationships (CERs) based on primary mirror diameter vary by an order of magnitude. We present new single-variable cost models for space telescope optical telescope assembly (OTA). They are based on data collected from 30 different space telescope missions. Standard statistical methods are used to derive CERs for OTA cost versus aperture diameter and mass. The results are compared with previously published models

A high-resolution, real-time range imaging system based on a LED array phase-shift range finder was developed to measure three-dimensional surface profiles. The range image is captured by a time-division scanning LED array heterodyne phase-shift range finder. The phase measurement used for obtaining depth is implemented by using the fast "four-bucket" algorithm. The design of a fast automatic gain control circuit obviously reduces the feedback response time and improves system measurement speed. Experimental tests for evaluation of the imaging system performance are described. Based on the theoretical analysis, a simplified signal-to-noise ratio model is proposed for guiding the design of this imaging system. Last, some issues requiring attention on constructing a large-pixel version of the system are also discussed. It was found that the range images can be acquired at a rate of 10 frames per second with a depth resolution better than ±5 mm in the range of 50 to 1000 mm.

A new pyramid wavefront sensor (PWFS), which utilizes a reflective pyramid mirror instead of a refractive pyramid prism at the focus of a telescope, is presented. As a key optical component in this PWFS, the pyramid mirror requires accurate microfabrication for excellent quality of the tip, the turned edges, and the surfaces. The moving mask lithography process is proposed for its economic, simple, and precise control to make the cross-sectional shape of the structure. The completed pyramid mirror has a square base of 1-mm length and four side facets inclined to the base at 3.7 deg. The sizes of the pyramid tip and turned edges are both about 6 µm, which show excellent aspects of sharpening-tip and knife-edges. The root mean square of four facets is approximately 70 nm, and the maximum profile deviation is 0.2 µm.

An autonomous star tracker is an opto-electronic instrument used to provide the absolute three-axis attitude of a spacecraft utilizing star observations. The precise calibration of the measurement model is crucial, as the performance of the star tracker is highly dependent on the star camera parameters. We focus on proposing a simple and available calibration approach for a star tracker with wide field of view. The star tracker measurement model is described, and a novel approach for laboratory calibration is put forward. This approach is based on a collimator, a two-dimensional adjustable plane mirror, and other ordinary instruments. The calibration procedure consists of two steps: (1) the principal point is estimated using autocollimation adjustment; and (2) the other camera parameters, mainly the principal distance and distortions, are estimated via least-squares iteration, taking into account the extrinsic parameters. To validate this proposed calibration method, simulations with synthetic data are used to quantify its performance considering the errors of the distortion model and calibration data. The theoretical analysis and simulation results indicate that the uncertainties of the measured star direction vectors are less than 4.0×10−5 rad after calibration, and this can be further improved.

The application of laser Doppler velocimetry to microfluidic flows is usually prevented due the large size of the measurement volume of typically 100 µm. A significantly higher spatial resolution can be achieved with the concept of the laser Doppler velocity profile sensor. However, the resolution is limited by wavefront distortions caused by aberrations of the optical setup. In this work, optical simulation software was employed to investigate the aberrations caused by the profile sensor setup by going from ideal to real lenses step by step. As the main source for the aberrations, the aspheric lens for collimating the laser beams was identified. On the basis of this simulation the setup of the velocity profile sensor could be optimized. The sensor was employed to measure the velocity profile in a microchannel. A spatial resolution of 1.2 µm and a relative uncertainty of the velocity of 0.25% result, confirming the findings of the simulation. This demonstrates the potential of the optimized velocity profile sensor for flow measurements at the microscale.

A three dimensional (3-D) measurement method with orthogonal composite grating aided by fringe contrast and background calibration is proposed. Due to spectrum overlap, we find that the contrast and background of each deformed phase-shifting fringe demodulated from the captured composite fringe image is changed differently, which violates the principle that the contrast and background between any two deformed fringes must be uniform in the traditional 3-D measurement method with orthogonal composite grating, and therefore results in measurement error. We acquire the phase-shifting sinusoidal fringes from the composite fringe image captured on the reference plane, and the zero- and first-order spectra of the sinusoidal fringes can be obtained by filtering in the spatial frequency domain. Then the ratio contrast and background coefficients between the phase-shifting sinusoidal fringes can be calculated. When an object is measured, the contrast and background of the demodulated deformed fringes can be calibrated by these ratio coefficients. A new 3-D measurement mathematical model is set up to reconstruct the object. Experiments prove the new method can effectively restrain the effect of spectrum overlap, and can improve the measurement accuracy more than 1 time.

Varying the heating rate of rapid thermal annealing (RTA) reveals a broadband shift of room-temperature photoluminescence (PL) in 3×1016 cm−2 Si+-implanted 400-nm-thick SiO2 films after RTA at 1150°C in dry nitrogen. At a heating rate of 100°C/s, the PL peaks shift from 2.6 eV to 1.7 eV for isothermal RTA durations from 1 to 20 s. Additionally, decreasing the heating rate to 25°C/s does not significantly shift the PL peak in the films after the isothermal RTA for durations ≥1 s. The attractive features of RTA provide a valuable reference for manufacturing of optoelectronic devices.

A novel and simple method is presented to generate a tunable high-repetition-rate pulse train based on dual-mode self-injection locking of a Fabry-Perot laser diode (FP-LD). Two fiber Bragg gratings (FBGs) are used in the experiment as feedback components. The two self-injection-locked modes evolve into a high-power, high-repetition-rate pulse train through the interplay between self-phase modulation and anomalous dispersion in a highly nonlinear fiber. A 139.6-GHz transform-limited pulse train with a peak power of 120 mW is generated. The pulsewidth is 1.7 ps, and the time-bandwidth product is 0.31. The repetition rate can be tuned by tuning the Bragg wavelengths of one of the two or both FBGs to coincide with other FP-LD modes. The output pulse is stable.

A room-temperature multiwavelength erbium-doped fiber laser (EDFL) based on a nonlinear high-birefringence fiber loop mirror (HiBi-FLM) is proposed and demonstrated. The nonlinear HiBi-FLM can induce not only wavelength-dependent loss (WDL) but also intensity-dependent loss (IDL). WDL and IDL can effectively suppress the mode competition caused by homogeneous gain broadening of the erbium-doped fiber (EDF), and ensure stable and uniform power distribution over wavelengths. As a result, up to 50-wavelength lasing operations with wavelength spacing of 0.8 nm, and more than 100-wavelength operations with wavelength spacing of 0.14 nm are achieved. The power distribution over the wavelengths is uniform, and the power fluctuation in each wavelength is smaller than 0.2 dB.

A novel optical ridge waveguide using calcium barium niobate (CBN) with a high electro-optic coefficient on silicon substrate is proposed for the design and realization of the next-generation hybrid modulators with short length and low driving voltage. To overcome the etching difficulty of CBN, the design of a waveguide, including an elevated CBN layer based on etched silicon dioxide, is presented. Fabrication of a thick 2.5-µm CBN layer is performed using pulsed laser deposition. Deposited silicon dioxide on the sides and top of the CBN reduces the waveguide loss as low as 3.44 dB/cm, measured using a cutback method. Good agreement between the mode profiles of the simulation and measurement is obtained.

An improved method for recovering the refractive index profile of an isotropic graded-index waveguide is presented on the basis of the cubic spline interpolation method. The surface refractive index of the waveguide can be obtained by using a polynomial function that is related with the parameters of all modes. The simulation results of several typical index distributions show that this method can be employed to recover a graded-index profile well.

We propose a new one-way resource reservation protocol for optical burst switching (OBS) networks, called Enhanced Just-in-Time Plus (E-JIT+). The protocol is described in detail, and its formal specification is presented, following an extended finite state machine approach. The performance evaluation of E-JIT+ is analyzed in comparison with other proposed OBS protocols (JIT+ and E-JIT) for the following network topologies: rings; degree-two, degree-three, and degree-four chordal rings; mesh-torus; NSFNET; ARPANET; FCCN-NET; and the European Optical Network. We evaluate and compare the performance of the different protocols in terms of burst loss probability, taking into account the most important OBS network parameters. It was shown that E-JIT+ performs better than available one-way resource reservation protocols for all the evaluated network topologies. Moreover, the scalability of E-JIT+ was observed, and when the network traffic increases, the burst loss probability also increases, leading to a worse network performance.

We propose a novel system of dynamic potential well generation and control using light pulse control within an add/drop optical filter. The multiplexing signals of the dark solition with bright/Gaussian pulses are controlled, tuned, and amplified within the system. The optical storage rings are embedded within the add/drop optical filter system, whereas the generated optical signals can be stored and amplified within the design system. In application, the storage signals can be configured to be an optical trapping tool, which is known as an optical tweezer, where the high field peak or well can be formed. The advantages are that the dynamic well can be stored and the array of wells can be generated for multiple wells applications. The different in time of the first two dynamic wells of 1 ns is noted.

The instantaneous frequency deviation of the pulses switched from a semiconductor optical amplifier (SOA)-assisted Sagnac interferometer is theoretically studied and analyzed. By using explicit expressions for the phase response and its temporal derivative and applying a numerical model, a set of curves is obtained that allows us to investigate and assess the dependence of the function of interest on the critical operational parameters. From their interpretation, the basic design rules that must govern them in order for its profile to acquire a form suitable for practical exploitation are extracted. These suggest that the combination of the energy of the driving control pulses and the small signal gain of the SOA must be such that the latter is biased to operate up to the medium saturation regime. Moreover, the width of these pulses must not exceed 10% of their allocated time slot, while the role of the loop asymmetry and the SOA carrier lifetime is found to be less significant. If these conditions are satisfied, then it is feasible to make out of most of the considered interferometric configuration's phase response variation per time increment while being employed as a switching module.

Due to its inherent parallelism and tremendous operational speed, optical signal is the most suitable for data processing and digital communication in various fields. Conventional electronic and opto-electronic systems are unable to fulfill this arena, because of their low speed and time delay. In the case of pure electronic flip-flop, when a switch is turned ON, there is notable propagation delay on the order of nanoseconds. For an opto-electronic flip-flop although the propagation delay time is much less than that of an electronic flip-flop (about 10 to 100 times less), there are many disadvantages. Some of these disadvantages are delay of response time due to the use of spatial light modulators, an O/E converter that does not operate at all frequencies or wavelengths, and the unavailability of such materials. An optical input encoding methodology is proposed for the performance of all-optical flip-flop operations possible for two inputs. These operations were conducted in all-optical mode and are parallel in nature. All the operations are treated with proper exploitation of some nonlinear materials.

We propose a steganalysis defeating the steganographic method using pixel-value differencing and modulus function, which is a recent method with high security and capacity for secret communication. The presented steganalysis is designed to reveal the existence of the message and uses three steganalytic measures that remarkably increase their values in the stego images. Hence, the stego images are statistically separated with the cover images. Detection of the hidden message is possible by modeling the changes generated by the embedding process and comparing the values of the steganalytic measures. To increase the performance of the steganalytic measures, a novel histogram estimation scheme is used to estimate the histogram value of the cover image and the embedding ratio. A support vector machine classifier is adopted to discriminate between cover and stego images. The experimental results verify that the proposed steganalysis can detect the stego images with 97.1% accuracy, even though the embedding ratio is just 10% of the maximum hiding capacity. Also, the length of the hidden message can be successfully estimated without the cover image.

The nonlocal (NL) means filter proposed by Buades, Coll, and Morel (SIAM Multiscale Model. Simul. 4(2), 490-530, 2005), which makes full use of the redundancy information in images, has shown to be very efficient for image denoising with Gauss noise added. On the basis of the NL method and a striver to minimize the conditional mean-square error, we design a NL means filter to remove multiplicative noise, and combining the NL filter to regularity method, we propose a NL total variational (TV) model and present a fast iterated algorithm for it. Experiments demonstrate that our algorithm is better than TV method; it is superior in preserving small structures and textures and can obtain an improvement in peak signal-to-noise ratio.

We propose a fusion method for multiple patch-based depth image completion via local stereo warping, in order to refine the disparity map. The false disparities are often extracted from occluded areas and textureless areas in stereo matching due to their ambiguities. Our fusion method iteratively performs the following three steps in order to reconstruct the areas with false disparities. First, we generate a reliability map from the initial disparity map. Second, we extract multiple patch candidates by using the proposed depth image completion. Finally, we verify each patch candidate by using local stereo warping in order to update the reliability map. Experimental results show that the proposed method is very robust for large textureless areas and occluded areas as well because our method yields superior results in comparison to many state-of-the-art methods using stereo matching.

We present a new scheme based on multiple-cue integration for visual tracking within a Gaussian particle filter framework. The proposed method integrates the color, shape, and texture cues of an object to construct a hybrid likelihood model. During the measurement step, the likelihood model can be switched adaptively according to environmental changes, which improves the object representation to deal with the complex disturbances, such as appearance changes, partial occlusions, and significant clutter. Moreover, the confidence weights of the cues are adjusted online through the estimation using a particle filter, which ensures the tracking accuracy and reliability. Experiments are conducted on several real video sequences, and the results demonstrate that the proposed method can effectively track objects in complex scenarios. Compared with previous similar approaches through some quantitative and qualitative evaluations, the proposed method performs better in terms of tracking robustness and precision.

An integer-based, post-compression rate-distortion optimization (PCRD-Opt) algorithm for JPEG2000 rate control is presented. The distortion estimation, described in the JPEG2000 standard, requires noninteger processing, and the overwhelming computational burden on JPEG2000 is the distortion calculation, which is calculated for every bit of the uncompressed image. An integer-based approach for distortion calculation is proposed. The proposed method reduces the computational requirements for PCRD-Opt within the Tier I encoder, as well as provides a more straightforward algorithm for embedded processing, requiring no distortion lookup tables (LUTs) for proper distortion computation. The proposed integer-based method improves upon the PCRD-Opt method described in the standard. Specifically, the proposed method reduces the Tier I processing time from a direct implementation of PCRD-Opt by approximately 39% on average and reduces the overall JPEG2000 processing by 34%. The proposed method reduces the Tier I processing time from an offline implementation of PDRD-Opt utilizing LUTs by approximately 21% on average, and reduces the overall JPEG2000 processing by 19%. The proposed integer-based distortion estimation provides a rate-distortion curve equivalent to both the direct and offline PCRD methods described in the standard.

We propose a highly precise digital image stabilization (DIS) scheme for a hybrid stabilizing system. The stabilizing system adopts a hybrid method of using both optical image stabilization (OIS) and DIS. In the stabilizing system, OIS prestabilizes the original unstable image using gyro-sensors, and the resultant image obtained from OIS is post-stabilized using DIS to remove the residual jitters less than one pixel. The proposed DIS, which is newly designed using control-grid interpolation, can remove not only translational jitters but also rotational ones simultaneously. Experimental results show that the proposed hybrid image stabilizer achieves considerable performance improvement against conventional stabilization techniques.

A locality projection discriminant analysis (LPDA) method by using local structure-based projection techniques is proposed to extract discriminative features in high-dimensional sample space. Two locality metric matrices are defined to make the discriminative projections preserve the intrinsic neighborhood geometry of the within-class samples while enlarging the margins of extra-class samples near to the class boundaries. LPDA efficiently addresses the nonlinear property of data and the small sample size problem in face recognition scenario; moreover, it can reduce the dimensionality of the original data (such as the role of principle component analysis) as well as extract complete discriminative features in dual subspaces. Experiments on synthetic data sets and ORL, PIE, and FERET low-resolution face databases are performed to evaluate LPDA-based methods and some known methods. The results demonstrate the effectiveness of LPDA and reveal some characteristics of this pure local structure-based method.

The use of fingerprints as a biometric is both the oldest mode of computer-aided personal identification and the most-relied-on technology in use today. However, current acquisition methods have some challenging and peculiar difficulties. For higher performance fingerprint data acquisition and verification, a novel noncontact 3-D fingerprint scanner is investigated, where both the detailed 3-D and albedo information of the finger is obtained. The obtained high-resolution 3-D prints are further converted into 3-D unraveled prints, to be compatible with traditional 2-D automatic fingerprint identification systems. As a result, many limitations imposed on conventional fingerprint capture and processing can be reduced by the unobtrusiveness of this approach and the extra depth information acquired. To compare the quality and matching performances of 3-D unraveled with traditional 2-D plain fingerprints, we collect both 3-D prints and their 2-D plain counterparts. The print quality and matching performances are evaluated and analyzed by using National Institute of Standard Technology fingerprint software. Experimental results show that the 3-D unraveled print outperforms the 2-D print in both quality and matching performances.

We present a novel feature extraction method for face recognition called neighborhood discriminant embedding (NDE), which incorporates graph embedding and Fisher's criterion and includes an individual discriminative factor (IDF). Graph embedding is able to reveal the representative and discriminative features from the underlying nonlinear face data structure. Fisher's criterion is recognized as an effective technique for discriminative feature extraction. IDF is proposed as an individual property of each sample to describe the contribution to classification. NDE can remain the local structure of the nearest neighbors of each data point during the dimensionality reduction as well as gather the within-class points and separate the between-class points in the low-dimensional projected space. Utilizing Fisher's criterion and taking into account IDF, the discriminative capability of NDE is further enhanced. Comprehensive experiments are conducted using the Olivetti Research Laboratory (ORL) and Facial Recognition Technology (FERET) face databases to demonstrate the effectiveness of our methods.

Video quality suffers significant degradation when transmitted over error-prone channels. We propose a novel error-resilient coding scheme based on the H.264/advanced video coding (AVC) standard to tackle this challenge. Compared to the traditional schemes that often employ a single and fixed tool, both intra refresh and reference selection refresh tools are dynamically used. The refresh locations, modes, and reference distances are determined according to the channel's state, the bit rate, and the expected distortion. A refresh allocation optimization mechanism for temporal and spatial terms is further developed under the approach, and the information from the distortion calculations is utilized to save computation time. Results indicate that the proposed scheme outperforms traditional refresh schemes in a loss-rate-varying transmission environment, and improves both subjective and objective qualities.

Programmable diffractive optical elements (DOEs) with axial response have many interesting applications, including diffractive lenses, axicons, and optical tweezers. In all these cases, it is essential to properly select the modulation configuration of the spatial light modulator (SLM) where the DOE is displayed, in order to avoid the undiffracted zero order component that appears on axis and overlaps the desired axial response. However, in general, the chromatic dispersion in liquid crystal SLMs prevents the cancellation of the zero order for a broadband light source, thus limiting the possibilities for polychromatic programmable axial DOEs. We operate a ferroelectric liquid crystal on silicon display with polychromatic illumination and with a specific polarization configuration that provides binary -phase modulation for all wavelengths. Since this type of modulation cancels the undiffracted zero order, we use this SLM to display DOEs with axial response. Moreover, chromatic control is achieved by time-multiplexing sequences of properly scaled DOEs with the corresponding selection of the input wavelength by means of an electronically controlled color-filter wheel. The presented experimental results include wavelength-controlled diffraction gratings, axicons, and vortex-producing lenses.

This PDF file contains the errata for “OE Vol. 49 Issue 07 Paper OE ERR-JUL2010-1” for OE Vol. 49 Issue 07