This PDF file contains the editorial “e-First, Publishing in Real Time” for OE Vol. 43 Issue 12

We propose a combined feature Fisher classifier method for face recognition (FR). Both facial holistic and local information are used for face representation. In addition, the enhanced Fisher linear discriminant model is employed for improving the generalization capability. Experiments show that the method is not only robust enough to moderate changes of illumination, pose, and facial expression but also superior to the traditional FR methods, such as eigenfaces and Fisherfaces.

A novel homodyne signal processing assisted phase-resolved optical system for the imaging of latent fingerprints is proposed. A multistep phase shifting method is introduced to remove the DC part of the fluorescence signals. Experiments are carried out with simulated fingerprint samples where their lifetime and emission wavelength are in close range to that of background fluorescence. The proposed phase-resolved technique can suppress the background fluorescence provided there is lifetime difference between two emissions.

We present the first implementation, results, and performance analysis of a vision system whose processing core is a prototype hardware neural network based on an optical broadcast architecture. The system captures an image by a CMOS image sensor, compares it with a set of sample patterns (classes), and provides an output that indicates the class which the input image corresponds to. Due to the optoelectronic neural processor characteristics, the number of classes can be enlarged without penalty on the operation speed of the system.

A dual optical detection scheme is proposed for optical code division multiple-access systems utilizing on-off-keying modulation technique. The proposed detector is developed by combining a correlation detector and a chip-level detector with the logical OR operation. In this way, the merits of two detectors can be fully exploited. Thus the dual detector can achieve the enhanced bit error rate performance in the presence of both multi-user interference and noise.

We propose a new tunable polarization-mode-dispersion compensator, which is substantially free from chromatic dispersion. The design uses a pair of high-birefringence linearly chirped fiber gratings. Each grating can adjust the differential group delay (DGD) nonlinearly by using a cantilever beam. The compensator can be tuned to operate over a range of wavelengths and can yield DGD values starting from 0 ps. Measured eye diagrams for a 10-Gbit/s system show that this compensator can greatly reduce the chromatic dispersion induced by a chirped grating.

This PDF file contains the editorial “Fusion Laser Engineering” for OE Vol. 43 Issue 12

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is a stadium-sized facility that, when completed in 2008, will contain a 192-beam, 1.8-megajoule, 500-terawatt, ultraviolet laser system together with a 10-m-diam target chamber and room for 100 diagnostics. NIF is the world's largest and most energetic laser experimental system and will provide a scientific center to study inertial confinement fusion and matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 10⁸ K and 10¹¹ bar, conditions that exist naturally only in the interior of stars and planets. NIF has completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kJ in 23-ns pulses of infrared light and over 16 kJ in 3.5-ns pulses at the third harmonic (351 nm). NIF's target experimental systems are being commissioned and experiments have begun. This work provides a detailed look at the NIF laser systems, laser and optical performance, and results from recent laser commissioning shots. We follow this with a discussion of NIF's high-energy-density and inertial fusion experimental capabilities, the first experiments on NIF, and plans for future capabilities of this unique facility.

With the first four of its eventual 192 beams now executing shots and generating more than 100 kJ of laser energy at its primary wavelength of 1.06 µm, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is already the world's largest and most energetic laser. The optical system performance requirements that are in place for NIF are derived from the goals of the missions it is designed to serve. These missions include inertial confinement fusion (ICF) research and the study of matter at extreme energy densities and pressures. These mission requirements have led to a design strategy for achieving high-quality focusable energy and power from the laser and to specifications on optics that are important for an ICF laser. The design of NIF utilizes a multipass architecture with a single large amplifier type that provides high gain, high extraction efficiency, and high packing density. We have taken a systems engineering approach to the practical implementation of this design that specifies the wavefront parameters of individual optics to achieve the desired cumulative performance of the laser beamline. This paper provides a detailed look at the causes and effects of performance degradation in large laser systems and how NIF has been designed to overcome these effects. We also present results of spot size performance measurements that have validated many of the early design decisions that have been incorporated in the NIF laser architecture.

Within the 192 National Ignition Facility (NIF) beamlines, there are more than 7000 large (40×40 cm) optical components, including laser glass, mirrors, lenses, and polarizers. These optics are held in large optomechanical assemblies called line-replaceable units (LRUs). Each LRU has strict specifications with respect to cleanliness, alignment, and wavefront so that once activated, each NIF beamline will meet its performance requirements. NIF LRUs are assembled, tested, and refurbished in on-site cleanroom facilities. The assembled LRUs weigh up to 1800 kg, and are about the size of a phone booth. They are transported in portable clean "canisters" and inserted into the NIF beampath using robotic transporters. This plug-and-play design allows LRUs to be easily removed from the beampath for maintenance or upgrades. Commissioning of the first NIF quad, an activity known as NIF Early Light (NEL), has validated LRU designs and architecture, as well as demonstrated that LRUs can be assembled and installed as designed. Furthermore, it has served to develop key processes and tools forming the foundation for NIF's long-term LRU production and maintenance strategy. As we look forward to building out the rest of NIF, the challenge lies in scaling up the production rate while maintaining quality, implementing process improvements, and fully leveraging the learning and experience gained from NEL. This work provides an overview of the facilities, equipment, and processes used to assemble and install LRUs in NIF.

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is a stadium-sized facility containing a 192-beam Nd glass laser. Its 1.053-µm output is frequency converted to produce 1.8-MJ, 500-TW pulses in the ultraviolet. Refer to the companion overview articles in this issue for more information. High-energy-density and inertial confinement fusion physics experiments require the ability to precisely align and focus pulses with single-beam energy up to 20 KJ and durations of a few nanoseconds onto millimeter-sized targets. NIF's alignment control system now regularly provides automatic alignment of the four commissioned beams prior to every NIF shot in approximately 45 min, and speed improvements are being implemented. NIF utilizes adaptive optics for wavefront control, which significantly improves the ability to tightly focus each laser beam onto a target. Multiple sources of both static and dynamic aberration are corrected. This article provides an overview of the NIF automatic alignment and wavefront control systems, and provides data to show that the facility is expected to meet its primary requirements to position beams on the target with an accuracy of 50-µm rms over the 192 beams and to focus the pulses into a 600-µm spot.

The laser performance operations model (LPOM) is developed to provide real-time predictive capabilities for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. LPOM uses diagnostic feedback from previous NIF shots to maintain accurate energetics models for each of the 192 NIF beamlines (utilizing one CPU per laser beamline). This model is used to determine the system setpoints (initial power, waveplate attenuations, laser diagnostic settings) required for all requested NIF shots. In addition, LPOM employs optical damage models to minimize the probability that a proposed shot may damage the system. LPOM provides postshot diagnostic reporting to support the NIF community. LPOM was deployed prior to the first main laser shots in NIF, and has since been used to set up every shot in NIF's first quad (four beamlines). Real-time adjustments of the code energetics parameters allow the LPOM to predict total energies within 5%, and provide energy balance within the four beamlines to within 2% for shots varying from 0.5 to 26 kJ (1.053 µm) per beamline. The LPOM has been a crucial tool in the commissioning of the first quad of NIF.

The National Ignition Facility performs fusion experiments using ultraviolet (351 nm) light. High-bandwidth, low-attenuation optical fibers are required to transport subnanosecond, UV laser diagnostic signals from the target chamber area to recording instruments located in adjacent rooms, with some fiber runs approximately 65 m in length. Special optical fibers are developed and fabricated to perform this task, since no existing commercially available fibers possess all of the required characteristics. These large-core (435 µm) fibers have optical dispersions less than 0.9 psec/m and attenuations less than 150 dB/km at 351 nm.

Prior to the recent commissioning of the first National Ignition Facility (NIF) beamline, full-scale laser-amplifier-glass cleanliness experiments are performed. Aerosol measurements and obscuration data acquired using a modified flatbed scanner compare favorably to historical large-scale lasers and indicate that NIF is the cleanest large-scale laser built to date.

We describe the design and operation of a high-speed adaptive optics system using a robust H_∞ controller. The system is also general purpose—it can be used in almost any application with minimal modifications and can be set up and operated by a minimally trained operator. The demonstrated system uses a wavefront sensor camera operating at 955 frames/s, a Xinetics 37-channel deformable mirror, and a dual processor computer to perform computations. The system exhibits control of up to 5 waves of focus, a closed-loop bandwidth of ~50 Hz, with a residual error of λ/75 rms.

The simplex fitting method makes use of a geometrical figure that finds the minimum variance value in successive steps. It was developed from the idea of finding the minimum value of a function. A set of vertices are assigned at first with associated coefficients and variances. The vertex with the highest variance value moves by one of the four mechanisms of reflection, expansion, contraction, or shrinkage. By repeating this process, the vertices proceed toward the minimum value of variance. Finally, the best fit to the basis function is achieved, and appropriate coefficients can be derived. When the algorithm of the simplex fitting method was examined, it was found that one of the four mechanisms, shrinkage, may not be used normally for continuous functions. This was also confirmed by examining the usage of the mechanism in the fitting of several equations. A revised flowchart of the simplex fitting method is presented.

The receiver operating characteristic (ROC) curve is a standard method for quantifying the performance of a detection task where the signal of interest is embedded in noise. ROC analysis has been applied to a variety of signal detection problems including medical imaging, acoustics, and automated target detection (ATD). The free response operating characteristic (FROC) curve generalizes the ROC model for search problems. The FROC model is appropriate when multiple detections are possible and the number of false alarms is unconstrained. The shape of the FROC curve depends on the underlying probability distributions for the signal and noise. The general FROC model is presented and parameter estimation is discussed. An example illustrates the approach.

We introduce a new approach to aircraft cargo compartment surveillance. The originality of the approach is in the use of a single sensor type, a CCD camera, to detect fire events and freight movement in aircraft cargo holds (multiphenomenom/monosensor approach). The CCD camera evaluation and the radiometric and geometric models are provided in (Sentenac et al., 2002). We go on to discuss the image analysis algorithms used in the detection of fire signatures (hot spots, flame, and smoke) and load displacement. For each phenomenon, the discriminant parameters are established and the algorithm is explained. The crucial factor is the validation procedure according to aeronautical standards. The experimental trials were carried out in a test chamber providing the fire and smoke test facilities [TF1 to TF6 following EN 54 (Afnor, 1997) requirements].

Dim target detection and tracking is a key technique for imaging tracking systems and is a challenging and leading-edge subject. A new strategy for dim target detection is presented. Various nonlinear features that are representative of dim targets are extracted from image sequences. Then, an information fusion algorithm by Karhunen-Loeve (K-L) transform is used to obtain an integrated feature. As a correlation degree, using an integrated feature calculates a target's position coordinates. Experimental results demonstrate the proposed method is feasible and effective.

We demonstrate a fully phase encryption system that uses digital holography. The input amplitude image to be encrypted is phase encoded, and either its Fourier or Fresnel transform is obtained. Using interference with a wave from a random phase mask, a Fourier or Fresnel hologram (encrypted data) is recorded digitally. The decryption key is also recorded as a digital hologram, called the key hologram. An electronic key is generated and multiplied with the encrypted hologram. A Fourier transform (encrypted image) is then obtained. The decryption key hologram, the electronic key, and the encrypted image can be transmitted through communication channels. The retrieval is carried out by all-digital means.

The control of transmittance and its use in glazing have powered the research on electrochromic devices in the last decade. The search for new materials to be used in different applications is a goal today. We characterize new electrochromic devices following an all-plastic construction. Poly(ethylendioxy-tiophene) (PEDOT) is used between plastic substrates and sandwiched symmetrically with a poly(ethylene oxide)-based polymer electrolyte. This multilayer acts as an electrochromic device without the necessity for an ITO layer. Several devices are tested to determine their electro-optical characteristics using cyclic voltammetry and complex impedance spectroscopy techniques, among others. Additionally, a protocol of electrical and optical characterization is proposed. The devices switch between 0 and 3 V with no dependence on the electric field direction, due to their layer construction symmetry. Impedance and voltammetry measurements show a hysteretic behavior from which charge injection can be derived. Finally, transmittance changes above 14% are measured at a 600-nm wavelength, so that further research must be done in materials and sticking process to improve the contrast. Bleaching and coloring times of 20 to 30 s make these devices potential candidates for applications in domotics, environment control or vision, and color filters.

Strain level measurement on a periodically actuated and instrumented structure can provide information about the health of that structure. A simple demodulation system employing artificial neural networks (ANNs) is analyzed for an extrinsic Fabry-Pérot interferometric (EFPI) strain sensor. The harmonic content of the nonlinear sensor output for the sinusoidal strain case is used to predict the maximum strain level. Implementations of the demodulation system are demonstrated for both simulated and experimental data using back-propagation neural networks. The simulation uses the theoretical response of the EFPI sensor and the experiment uses an EFPI-instrumented smart composite beam to obtain training and testing data. Excitation is provided by a piezoelectric actuator operating from 50 Hz to 1 kHz. System performance is compared for two-stage and single-stage networks and for differing types of data preprocessing. The ANN systems successfully extract the signal harmonics and predict the peak strain levels. Data preprocessing using principal component analysis produces the best accuracy. The architecture of an EFPI-based health monitoring system is proposed.

We describe a strategy for the content-based compression of mammograms. In this two-step strategy, the clinically important structures are first identified via a fractal-based segmentation method. Then, a modified version of JPEG2000 is applied in such a way that lossless compression is applied to the extracted structures from the first step, while a lossy compression is applied to the remaining regions. Preliminary results demonstrate that this strategy can achieve high compression ratios (up to 50:1) without compromising the diagnostic quality of the mammograms.

The effect of temporal synchronization between the chirped signal pulse and the pumping pulse in an optical parametric chirped pulse amplification laser system is researched theoretically and experimentally. The results show that the gain of optical parametric amplification is sensitive to the temporal synchronization. Therefore, accurate temporal synchronization between the chirped signal pulse and the pumping pulse is essential to obtain high optical parametric amplification gain and stable output from an optical parametric chirped pulse amplification laser. Based on our 16.7-TW/120-fs optical parametric chirped pulse amplification laser system with ~1-ns pumping pulse duration and <10-ps time jitter between the signal and pumping pulse, the effect of the temporal synchronization on optical parametric chirped pulse amplification is demonstrated. The experimental results agree with the calculation.

A simple method is proposed to calibrate phase shift modulators used in phase-shifting interferometry for algorithms requiring π/2 phase shifts. The method provides a convenient in situ calibration without any change in experimental setup for a wide range of phase shift modulators such as piezoelectric translators (PZTs), Pockels cells, etc. The calibration by the proposed method is fast, efficient, and accurate. The performance of the new method is demonstrated by calibration of a Pockels cell in a phase-stepped speckle interferometer. The results obtained from the new calibration method are found to agree to within 2% of those from a previously described method for the calibration of nonlinear phase modulators.

We have improved the conventional polarization method used to separate and simultaneously capture the moiré interferometry fringe patterns of the U and V fields. The beamsplitter grating and integrated analyzers in the conventional method are substituted for with a Wollaston prism. The operation of this method is thus simplified and quality of the fringe patterns can be improved. Furthermore, it is easy to implement this technique in compact moiré interferometry system with a minimum of additional components. The key points of operation are stressed and an application of this improved method is presented to show its feasibility. Also, the system error due to the use of this technique is analyzed.

We propose a sinusoidal phase-modulating laser diode interferometer for measuring small angular displacement. The interferometer is based on a Fabry-Perot plate. It has a simple structure and is insensitive to external disturbance. Sinusoidal phase-modulating interferometry is used for improving the measurement accuracy. A charge-coupled device (CCD) image sensor is used for measuring the distance between the reflected beams from two faces of the Fabry-Perot plate. From the distance, the initial angle of incidence is calculated. Compared with Michelson interferometers and autocollimators, this interferometer has the advantage of compact size and simple structure. The numerical calculation and experimental results verify the usefulness of this novel interferometer.

A real-time lateral shearing interferometry that uses a pair of Ronchi gratings to perform wavefront shearing operations is described for measuring slope and curvature fringes simultaneously in thin structures. It involves simultaneous imaging of diffracted wavefronts using Fourier filtering. Two sets of fringe patterns, one representing slopes and the other curvatures, occur simultaneously at spatially distinct locations on the image plane, thereby eliminating the need for additional postprocessing of the recordings. In this work, the principles involved in the measurement of slopes and curvatures using this technique are explained. The method is then demonstrated on thin structures subjected to well-defined loading conditions, such as a clamped circular silicon wafer subjected to central displacement. Measurements have been successfully compared with analytical solutions.

A simple method of applying mechanical pressure to vary the cell thickness of a liquid crystal cell in a controlled, repeatable manner is presented. Experimental evaluation of several cells subjected to a controlled, mechanical point pressure show the capability of attaining a liquid crystal cell thickness range of 3 to 12 µm, at an accuracy of 5%, within a 2- to 6-mm radius around the pressure point, for the 22×25-mm cells studied. Temporal stability tests show no measurable drift in the cell thickness for more than 120 h. The method offers the advantages of simplicity (avoiding the need of multiple liquid crystal cells), accuracy, repeatability, and temporal stability, as well as speedy change of the cell thickness.

We measured the tunability of a Nd:YAG, 946-nm microchip laser as the function of the laser crystal length and the reflectivity of the output mirror. A decrease in the tunable range is observed with the decrease in the reflectivity of the output mirror and the crystal length. The center oscillation wavelength is estimated to be ~946.1 nm. The oscillation wavelength varies between ~945.8 and ~946.4 nm for our experiments.

Both IKONOS and QuickBird offer 11-bit panchromatic and multispectral data in which more details can be extracted from scenes that are very dark under shadows or very washed out due to excessive sun reflectance. In this work, a discrete cosine transform (DCT)-based single-scale Retinex (SSR) technique is presented to extract the highest possible spatial details from the panchromatic image, and a minimum/maximum percent cutoff approach is used to preserve the most spectral information in the multispectral imagery. By fusing those two images, the typical bright target recovery (BTR) response can be avoided. Furthermore, to address the color distortion problem by the fusion process, a fast intensity hue saturation (IHS) image fusion technique with direct saturation stretching in RGB space is also proposed. To verify the efficacy of the proposed techniques, experiments are conducted using real IKONOS and QuickBird imagery covering different areas. Experimental results have shown that the perfect performance, maximizing increased details and minimizing color distortion, is achieved.

We present a generalized random field model in a random environment to classify hyperspectral textures. The model generalizes traditional random field models by allowing the spatial interaction parameters of the field to be random variables. Principal component analysis is used to reduce the dimensionality of the data set to a small number of spectral bands that capture almost all of the energy in the original hyperspectral textures. Using the model we obtain a compact feature vector that efficiently computes within- and between-band information. Using a set of hyperspectral samples, we evaluate the performance of this model for classifying textures and compare the results with other approaches that consider different kinds of spatial, spectral, and intensity distribution information.

A new approach is described for obtaining spectral imagery over a broad range of infrared wavelengths, with high efficiency, and with a single grating element and focal plane array. The approach represents a simplification and mass reduction over the traditional approach involving multiple focal plane arrays, dispersing elements, and optical beamsplitters. The new approach has significant advantages for space-based hyperspectral imagers operating in the infrared over a broad range of wavelengths (e.g., MWIR and LWIR), where the reduction in cryocooled mass relative to the multichannel approach translates into noteworthy savings in cryocooling requirements and launch costs. Overlapping grating orders are focused onto a multiwaveband focal plane array to create spectral images of a scene simultaneously in multiple wavelength regions. The blaze of the grating is chosen so that all spectral orders are dispersed with high grating efficiency. Such an approach extends the spectral range of dispersive spectrometers to several octaves of wavelength, while preserving the compact packaging and cryogenic requirements of conventional (one octave) instruments. We conclude with a description of a ground-based demonstration of an MWIR and LWIR embodiment of the concept.

A preliminary study of the application of speckle shearographic methods in the nondestructive inspection of the curved surfaces of soft tissue phantoms is presented. An extended theoretical formulation dealing with the slope fringe formation in the curved surface of the phantom tissue specimen is derived and compared with the experimentally obtained fringe patterns. Abnormalities are introduced in different layers of the half-cylindrical shaped tissue phantom that resembles abnormal growths in body cavities such as polyps in different parts of the gastrointestinal path, especially in the large intestine. A qualitative comparison of the shear fringe patterns for specimens with and without abnormalities is presented and the fringe patterns are compared with the slope contours generated numerically using finite element modeling.

A new method for chromatic dispersion compensation based on a real-time chirp feedback is presented. The method makes use of an optical channel modulated at 10 Gbits/s by an external modulated transmitter using a nonreturn to zero (NRZ) in the nonlinear regime. The signal undergoes self-phase modulation (SPM) effect. An optical filter, which is used as an optical frequency discriminator, is located at the end of the link and serves for measuring the time-resolved frequency chirp in the transmitter. We show that by measuring the chirp in real time and controlling the SPM effect, we can manage the amount of chromatic dispersion to be compensated. This control process enables us to reduce the system path penalty to a value close to 0 dB and thus achieve a dramatic improvement in the system bit error rate (BER).

We discuss an estimation method of production tolerance of an aspherical mirror located near an image plane of imaging optics. Local corrugation error having a period smaller than the footprint width of the illuminated area is considered. A simple periodic corrugation model using a radial trigonometric function is made. Related equations for ray-tracing calculations are derived. Also, analytical equations for calculating ray aberrations on the image plane are derived for the verification of ray tracing. Ray tracing simulations are made using optical parameters of example projection optics, which have a large aspherical mirror near the image plane and attain extraordinary large projection angles of 136 deg. The simulation result teaches that an increase of the rms spot radius on the image plane, as well as MTF degradation, depend on the maximum tilt angle of corrugation. This result is valid at the corrugation frequency higher than the reciprocal of half the meridional footprint width on the aspherical mirror as long as the scattering effect is ignored. In addition, minimum MTF against the maximum tilt angle of corrugation is calculated using the projection optics. If an admissible MTF degradation is assumed to be 10% at the Nyquist frequency (0.42 lp/mm) of the projected pixels having a pitch of 1.2 mm, the tolerance of the maximum tilt angle of corrugation is found to be 0.035 mrad at a relative field of 1.0, and the tolerance is increased to be 0.075 mrad at a relative field of 0.75.

A new Kirkpatrick-Baez-type focusing mirror system for use in synchrotron radiation IR beamlines is designed and fabricated. This mirror system, which contains two fifth-order-polynomial-corrected cylindrical mirrors, can collect and focus the long arc shape IR source from the bending magnet into a nearly perfect point image. To fabricate these two uncommon mirrors, 17-4 PH type stainless steel substrates are chosen and mechanically bent from planar to the desired fifth-order-polynomial-corrected cylindrical shapes with central radii of 3.74 and 5.43 m. The root mean square (rms) roughness and the slope error of these two mirrors are measured to be 0.3 nm and less than 6.3 µrad, respectively. The method for calculating the polynomial coefficients of both mirrors as well as the mirror fabrication process, mechanical design, and the method for adjusting the mirror shape using a long trace profiler are presented.

A simple method for fabricating fiber-embedded boards using a grooving technique is described that is quite cost effective and fully compatible with conventional printed circuit board (PCB) processes with no necessity for a specially designed wiring machine. FR-4 plates are grooved using a dicing saw machine and followed by placing optical fibers into the grooves. The fiber-embedded PCBs are laminated by conventional PCB processes at a temperature of 180°C for 1 h under 47 kg/cm² of pressure. The 50/125-µm glass fibers, and the polyimide-coated glass fibers are laminated successfully. In the fiber-embedded boards with a length of 10 cm, the variation of center positions of the embedded glass fibers is about ±5 µm. The transmitted optical power through the fiber-embedded boards shows a good uniformity of less than ±0.5 dB variation from the average value for the 12 fiber channels. Data transmission through the board at data rates of 2.5 Gbits/s is achieved. After confirming the successful laminations and the data transmission with the small-scale fiber-embedded boards, a large-scale prototype of the fiber-embedded board for a backplane application is successfully fabricated.

Condenser optics in extreme ultraviolet lithography (EUVL) systems are subjected to frequent replacement as they are positioned close to the illumination source, where increased heating and contamination occur. In the case of aspherical condenser elements made by optical figuring/finishing, their replacement can be very expensive (several hundred thousand dollars). One approach to this problem would be to manufacture inexpensive illuminator optics that meet all required specifications and could be replaced at no substantial cost. Diamond-turned metal substrates are a factor of 100 less expensive than conventional aspherical substrates but have insufficient finish, leading to unacceptably low EUV reflectance after multilayer coating. We show that by applying a smoothing film prior to multilayer coating, the high-spatial-frequency roughness of a diamond-turned metal substrate is reduced from 1.76 to 0.27 nm root mean square (rms), while the figure slope error is maintained at acceptable levels. Metrology tests performed at various stages of the fabrication of the element demonstrate that it satisfies all critical figure and finish specifications as an illuminator. Initial experimental results on the stability and performance of the optic in a real EUVL plasma source environment show no accelerated degradation when compared to conventional substrates.

We present a novel out-of-plane polymer refractive microlens that can be prealigned with other optical components in a free-space micro-optical bench. This out-of-plane microlens is designed and optimized through simulation, and then successfully microfabricated using a unique UV lithography technology. In this fabrication technology, the desired surface profile is obtained by a controlled SU-8 development after two tilted exposures. The microlens backside focal length, diameter of the focal pad, and the surface curve were measured, analyzed, and compared with the simulation results. The microlenses obtained are perpendicular to the substrate. This out-of-plane prealigned microlens can be used to eliminate the alignment and assembly steps and obtain integrated optical benches. It helps to reduce the running cost, save time, and improve the quality and performance of the integrated optical systems.

We propose a new algorithm that generates intermediate scenes from the near and the far views. Assuming that two cameras can be approximated with the affine model, we align the optical axes of the near and the far views on the transition baseline using the Fourier method. Then we determine the scale of the desired novel scene, zoom in the far view, and zoom out the near view. The zoom-in far view is theoretically the same as the zoom-out near view, but disparities exist that cause the synthesized image to present the double-blurring effect. Therefore, we remove the disparities of the zoom-out near view and then synthesize it with the zoom-in far view. For the panorama-based navigation system, the proposed algorithm can also generate images having smooth and realistic transitions as the viewer walks from the current panoramic image to the next panoramic image.

An open-cell configuration of the photoacoustic (PA) technique is employed to determine the thermal and transport properties of intrinsic Si and Si doped with B (p-type) and P (n-type). The experimentally obtained phase of the PA signal under heat transmission configuration is fitted to that of theoretical model by taking thermal and transport properties, namely, thermal diffusivity, diffusion coefficient, and surface recombination velocity, as adjustable parameters. It is seen from the analysis that doping and also the nature of dopant have a strong influence on the thermal and transport properties of semiconductors. The results are interpreted in terms of the carrier-assisted and phonon-assisted heat transfer mechanisms in semiconductors as well as the various scattering processes occurring in the propagation of heat carriers.

In site-specific management for precision farming there is a demand for sensors that can easily monitor crop nitrogen requirements throughout the growing season with a high resolution. Currently used optical measurement platforms such as satellites, airplanes, and hand-held sensors do not meet the requirements for good site-specific nitrogen management possibilities. An automated sensor system mounted on a tractor is developed and used to detect crop nitrogen status optically. A line spectrograph is used to detect the amount of nitrogen (kg N/ha) and chlorophyll (kg/ha) in a wheat crop (Triticum aestivum L.). By calculating the red edge inflection point of the plant spectra in the images, wheat crop nitrogen stress within small areas in the field can be detected. The spectrograph red edge is highly correlated with nitrogen applied to the wheat crop (in kilograms of N per hectare) (0.90), with the crop nitrogen amount (in kilograms of N per hectare) (0.89), and with the chlorophyll amount in the crop (in kilograms per hectare) (0.86). The average errors when estimating these variables with the red edge inflection point are 0.4% (24.15 kg N/ha), 3% (17.31 kg N/ha), and 8% (14.72 kg/ha), respectively. The average standard deviation of the calculated crop nitrogen inside a plot is 7.78 kg N/ha (6%) and for a nitrogen application rate of 9.22 kg N/ha (6%). The average standard deviation of the calculated chlorophyll inside a plot was 5.87 kg/ha (8%) and for a nitrogen application rate of 6.79 kg/ha (9%). This means that spectrograph red edge measurements of the wheat crop during the growing season are good estimators of crop nitrogen uptake. In this way, it can be an indirect predictor of topdress nitrogen needs.

We present the development of a parallel-axis stereoscopic imaging camera (PASIC) for teleoperation and depth measurement. To reduce the vergence focus decoupling problem, which could cause cybersickness, we design a mechanism to control the vergence and the focus of the camera simultaneously. We analyze the relationship between parallel and orthogonal motions of the camera lens system with respect to the image plane. Under the condition that the lateral disparity in stereo images remains constant, the parallel motion causing vergence and the vertical motion causing focus show linear relationship. The camera is calibrated to a reference distance, and the depth to an object is computed by a triangulation technique and a calibration lookup table. We analyze the accuracy of depth measurement with the consideration of radial distortion. Then the calibration table is refined accordingly.

We investigate the bandwidth limitations and the analog modulation characteristics at microwave frequencies (0.1 to 10 GHz) of a low-capacitance oxide-confined 670-nm InGaAlP vertical-cavity surface-emitting laser (VCSEL). A maximum modulation bandwidth of 6.3 GHz, limited by thermal effects, is achieved. From measurements of distortion and noise, a spurious free dynamic range (SFDR) of 100 dB Hz^2/3 is obtained at frequencies up to 2 GHz, rendering such VCSELs useful for transmission of analog signals. At higher frequencies, the SFDR drops due to the thermally limited resonance frequency.

We propose a new efficient discrete cosine transform (DCT) and quantization algorithm for the H.264 encoder. We theoretically analyze integer DCT and quantization of the H.264 encoder. A theoretical analysis shows that there are redundant calculations for DCT and quantization. In the proposed algorithm, one of four methods—1. DCT skip; 2. reduced DCT1; 3. reduced DCT2; 4. original DCT—is selected by using the minimum SAD information obtained in the motion estimation. The reduced DCT1 and reduced DCT2 eliminate the redundant calculations required for DCT and quantization. The simulation results show that the proposed algorithm achieves an approximately 15 to 25% computational saving without video-quality degradation, compared to the conventional method.

We present a novel method of measuring the depth of a mode for a buried ion-exchanged channel waveguide in glass while simultaneously measuring its near-field mode profile. The method is simple to implement and can be used without removing the sample from a standard waveguide characterization system. Experimental results for surface and buried Ag⁺/Na⁺ exchanged waveguides are presented. It is demonstrated that the depth of a mode can be determined with an uncertainty of ±0.2 µm.

In wavelength division multiplexing (WDM) ring networks, subwavelength traffic streams can be elaborately arranged in wavelength channels to minimize the total cost due to the implemented wavelengths, electronic terminals, and so on. In this work, a genetic algorithm is proposed with a permutation-based chromosome representation and a selection method of the roulette wheel model to solve these traffic grooming problems, which can minimize the number of required electronic terminals, and keep high utilization of wavelengths. Some features of the algorithm are modified for high performance. To improve the algorithm further, different strategies are proposed to enhance the chromosomes in the decoding procedure. Computer simulations are performed with randomly generated traffic patterns to compare their effects and the results are analyzed.