This PDF file contains the editorial “Editorial: We are getting thicker!” for OE Vol. 32 Issue 11

This PDF file contains the editorial “Guest Editorial: Acquisition, Pointing, and Tracking” for OE Vol. 32 Issue 11

Spatial averaging techniques have been used to compare signal acquisition (i.e., detectivity performance) of hexagonally sampled equivalent-area rectangular, hexagonal, and rhombic pixel arrays. In the absence of noise, rhombic focal-plane arrays (FPA5) are found to be associated with a modulation transfer function, which is almost identical to that of the rectangular FPA. However, while detecting noisy signals, the probability density function of the detected signal of the rhombic FPA is found to be smaller than that of hexagonal FPA, but higher than that of the rectangular FPA. At large noise variances, all three staring arrays perform almost the same in acquisition of signal.

Liquid crystal writable grating technology is being developed for beam steering in laser radar systems. We consider the ability of writable gratings to steer broad-spectral-band radiation for use in passive sensors. We find that there is potential for these devices in microscan systems because there is little or no dispersion for the small scan angles required in microscanning. The dispersion that is present is less than the resolution of the sensor considered here. For large angle steering we find that dispersion correction or a narrowing of the spectral bandwidth is required. The degradation in sensitivity resulting from narrowing the spectral bandwidth is considered. We find that a high-quantum-efficiency step-stare sensor with a two-dimensional focal plane array responsive over a narrow spectral width can achieve the same sensitivity as current linear scanning sensors while being able to steer the field of view (FOV) over a larger field of regard with no moving parts. Approaches for dispersion correction and postdetection correction are discussed. A promising approach for steering a narrow FOV with broad spectral content and good resolution is described.

A cascade of microlens arrays that are decentered with respect to each other is one potential method for beam steering; the magnitude of the steering depends on the amount of decenter. A simple, heuristic geometric analysis is presented that suggests that the output of the arrays is analogous to a blazed grating. The periodic nature of the exiting wavefront restricts allowed steering angles to values determined by the element-to-element spacing of the microlens arrays. The efficiency of steering into a desired mode of the grating is determined both by the amount of decenter of the microlens arrays and the fill factor at the output of the arrays. It is shown that maximum fill factor is desired, which can be achieved through the addition of a microlens array that acts like a field lens. Assumptions are identified under which the grating nature of the output can be predicted using Fresnel diffraction theory. Future work in the area of microlens beam steering is suggested.

In an effort to increase the SNR of a continuous wave, 1-μm all solid state ladar system, a rare-earth-doped optical fiber amplifier is investigated as a preamplifier for ladar return signals. The experimental system is detailed and a theoretical analysis of the fiber amplifier's effect on both heterodyne and direct detection schemes is provided. Beginning with the optical powers incident on the detector, the signal and noises are analyzed, through the detector electronics, to predict the SNR. The SNR is then plotted as a function of the return signal power, and a SNR threshold is defined to determine a minimum detectable signal power. The return signals required to attain the SNR threshold are then compared for four cases: direct detection with and without the fiber amplifier and heterodyne detection with and without the fiber amplifier. For the direct detection scheme considered, our results predict a sensitivity increase of 20.6 dB with the addition of the fiber amplifier, yet for heterodyne detection the predicted sensitivity increase is only 3.1 dB.

A 2.09-μm ladar system is built to compare coherent to incoherent detection. The 2.09-μm wavelength is of interest because of its high atmospheric transmission and because it is eyesafe. The 2.09-μm system presented is capable of either a coherent or incoherent operational mode, is tunable in a small region around 2.09 μm, and is being used to look at the statistical nature of the ladar return pulses for typical glint and speckle targets. To compare coherent to incoherent detection the probability of detection is investigated as the primary performance criterion of interest. The probability of detection is dependent on both the probability of false alarm and the probability density function, representing the signal current output from the detector. These probability distributions are different for each detection technique and for each type of target. Furthermore, the probability of detection and the probability of false alarm are both functions of the dominating noise source(s) in the system. A description of the theoretical expectations of this system along with the setup of the ladar system and how it is being used to collect data for both coherent and incoherent detection is presented.

To achieve robust and efficient object recognition, particularly from real outdoor images, we must develop methods to reduce clutter and extract salient information of objects. Toward this end, we present a technique to rank and extract salient contours from a 2-D image acquired by a passive sensor. The goal is to find important contours corresponding to possible objects. Our method starts with edge pixels, or edgels, from an edge detector and assigns a saliency measure to linked edgels (contours) based on length, smoothness, and contrast. For length we use the number of edgels in the contour, for smoothness we use average change of curvature, and for contrast we use the edge magnitude. Contours are ranked by saliency, and the more salient contours are selected. We test this method on several real outdoor images of objects in cluttered and occluded conditions and obtain excellent results. We evaluate the performance of this technique in the context of a recognition system that matches 2-D image corners with 3-D model vertices. We present graphs, using corners on the object of interest and clutter, to demonstrate the appropriateness of saliency ranking. We plot curves displaying the percentage of object corners to all image corners for the top few salient contours. We conclude by observing that extracting the more salient contours increases the ratio of image corners on the object to all image corners, reducing the search space for the corner matching step in recognition.

A number of acquisition, tracking, and classification algorithms have been developed to deal with various image processing problems in the laboratory. Typically, these algorithms are too complicated to implement in a low-cost, real-time processor. Using image data in many real-time applications requires a system with very high data rates, low power dissipation, and a small packaging volume. We developed a processor architecture suitable for these applications, and adapted and demonstrated a co-occurrence matrix target detection algorithm in computer simulation and real-time hardware. A histogram, or gray-level distribution, is often used to select a threshold for image segmentation. This technique is often inadequate because the histograms tend to be noisy and exhibit many small peaks. Co-occurrence matrix-based segmentation allows homogeneous regions of an image to be identified and separated from a cluttered background. Results are shown for target segmentation using representative infrared imagery and real-time hardware.

A software simulation of a multiaperture vision system (MAVS) that locates a point-source target by means of a neural network processor is presented. Models are developed and tested for one-, three-, and nine-eyelet systems. The advantages and limitations of each MAVS system are discussed. A back-propagation neural network is developed and trained as a target-location processor for each system. The accuracy of the neural network in determining the spatial position of a point-source target placed inside the field of view is then determined. The performance of each of the three systems is compared, and the accuracy of the system is shown to increase with the addition of more eyelets.

Correlation performance of a computer-simulated binary joint transform correlator is investigated when the input image has been degraded because of blurring. Both constant and adaptive thresholding were considered for comparison. In general, adaptive thresholding performed better in handling blurred input images both in the absence and presence of noise.

We describe a phase-difference prewhitening technique to improve the interclass discrimination capability for the case of one filter per multiobject. Conceptually, this is an extension of the magnitude- hitening operation in Yaroslavsky's optimal filter for the case of one filter per object. By introducing this technique into the filter synthesis procedure, the discrimination ability is increased significantly compared with previous methods. Computer simulation results by means of this technique are given.

Rotation and scale requirements imposed by the joint Fourier transform correlator (JFTC) are relaxed by means of a logarithmic-polar transformation of the input object. The resulting target recognition/tracking system utilizes the positional invariance of the Fourier image, whereas the logarithmic-polar mapping is performed on the Fourier plane instead of the intensity of the Fourier plane. The positional information is saved, and consequently, multiple input objects are processed simultaneously. Enhancements in the areas of input binarization and power spectrum enhancements to the liquid crystal television based JFTC are performed to improve its recognition and discrimination abilities.

In tracking maneuvering targets, ascertaining the start and the end of a maneuver time is a prerequisite to maintaining good track quality. Existing maneuver detection schemes based on point-mass tracking are either inadequate to reliably detect rapid maneuvers or computationally impractical. Maneuver detection based on images can be more accurate but is also very demanding on computational and storage resources. A new method of detecting maneuvers using information from an image sensor is presented. It involves the use of two detectors, one to detect linear acceleration and the other to detect orientation changes of the target. To detect target maneuvers, the detectors continuously monitor the position of three points extracted from the target image-the centroid, the front centroid, and the rear centroid. Contrary to existing image-based tracking methods, the approach put forth is very attractive from computational and storage points of view. The proposed method was tested using simulated tracks and the results confirm the benefits of its utilization for maneuver detection.

We introduce a biologically based method for motion detection and track initiation. The model consists of five hexagonally packed layers of single compartment neurons. The model mimics some of the processing in the retina and has localized interactions between cells in each layer. To evaluate the gain from using a biological model versus a more conventional approach we have compared the performance of three methods: simple intensity thresholding, the biologically inspired model, and an algorithm involving a truncated sequential probability ratio test. These methods were tested with a large number of real and simulated astronomical data and with a standard set of 50 images using targets at various SNRs. We discuss the importance of various aspects of the biological model for the overall performance on a target detection task.

A mathematical model of a pointing, acquisition, and tracking (PAT) system intended for laser-based intersatellite communication is developed and implemented in software in the form of a simulator. It represents major dynamic channels of the system and complex interaction of operational conditions, disturbances, and design parameters thus facilitating the solution of various analysis, design, and control problems. Application of computer graphics and animated schematics, driven by the model, provides accurate display of the most intricate phenomena behind the PAT operation. Coupled with a working laboratory prototype of the PAT system through a data communication board, the simulator is capable of displaying both simulated and real variables serving as a diagnostic tool. The simulator has been applied for development and verification of a novel jitter compensation scheme.

A technique, resulting in the significant reduction of negative effects of satellite jitter on the accuracy of laser beam positioning in satellite communication systems, is presented. It implies application of vibration monitoring instrumentation for estimation of the motion components constituting jitter. A self-tuning feedforward jitter compensation scheme is introduced to the existing mirror-positioning control systems. The technique is verified by computer simulation and is in the process of experimental investigation.

The estimation of the angular position of an object and the evaluation of image quality are considered for an active tracking system consisting of an agile scanning transmitter and an imaging or nonimaging receiver. We estimate angular positions of point objects and derive bounds on tracking accuracy. We examine the effect of shot noise and illumination beam jitter on angular position estimation and define various quality measures in the context of position estimation. Examples of algorithms for position estimation with accuracies approaching theoretical bounds are presented.

A complex associative memory model based on a neural network architecture is proposed for tracking three-dimensional objects in a dynamic environment. The storage representation of the complex associative memory model is based on an efficient amplitude-modulated phase-only matched filter. The input to the memory is derived from the discrete Fourier transform of the edge coordinates of the to-be-recognized moving object, where the edges are obtained through motion-based segmentation of the image scene. An adaptive threshold is used during the decision-making process to indicate a match or identify a mismatch. Computer simulation on real-world data proves the effectiveness of the proposed model. The proposed scheme is readily amenable to optoelectronic implementation.

An economical refracting type laser beam scanning device, exhibiting a minimum across-scan error without corrective measures, is described. The main structural assembly of the device consists of a rotating prism, a fixed spherical lens, and a fixed convex spherical auxiliary reflector (SAR). Trigonometric equations are developed to determine the radius of curvature of the SAR and the size of the exit pupil. Resolution analyses are presented for a specific set of design parameters.

A tracking system has been developed with a compromise between complexity and cost and efficiency in mind. The tracking system consists of a PC fitted with a specific one-card processor designed in our laboratory that acquires the image and implements the recognition algorithm at video rate. We describe the recognition method, the hardware architecture, and some applications and results. The system can be extended to track targets in 3-D using two cameras and two processors. Finally we describe different applications already tested: A robot servo-positioning system in moving parts operation, a tracking system for vehicles for traffic supervision and control, and a tracking system for people for the study of their behavior.

Developing wideband stable platforms for tracking and pointing systems is often inhibited by plants containing high-order dynamics and nonlinearities. Control system stability and robustness are commonly achieved by using passive compensators to frequency shape the active state variables. In the presence of nonlinearities and high-order dynamics, fixed frequency, passive parameter compensators usually lead to overly complex solutions. In such systems, however, control stability can be achieved by manipulating the active state variables themselves. The general concepts of state equalization, a control system stabilization technique that utilizes the differing characteristics of the active state variables to achieve the desired stability in systems containing nonlinear resonant plants, is presented. The resonance phenomenon and state variable relationships in resonance are discussed and analytical models are presented. An existing application is used to illustrate the use of state equalization in extending rate loop bandwidth.

A cell manipulator capable of (1) trapping single living cells, (2) making a direct binary contact from a chosen direction, and (3) judging the formation of cell-to-cell adhesion is produced by means of optical trapping in combination with a fixed micropipette. The specificity of the cell adhesive capability is tested with isolated hydra cells, demonstrating a clear difference in adhesive properties between ectodermal and endodermal epithelial cells

By the examination of a simple three-level quantum system, the time-dependent rate-equation analysis of the two-step excitation of fluorescence is extended to include the effects of the intermediate state lifetime and of saturation pumping on the total number of fluorescent centers excited to the target state. Further, the results relevant to the implementation of such a process to a volumetric 3-D display device are emphasized, and the performance of a display medium is indicated with respect to brightness and data rate. Restrictions placed on the two-step system by the fact that they are no longer assumed to be pumped in isolation are discussed.

We use the paraxial geometric optics model of image formation to derive a set of camera focusing techniques. These techniques do not require calibration of cameras but involve a search of the camera parameter space. The techniques are proved to be theoretically sound under weak assumptions. They include energy maximization of unfiltered, low-pass-filtered, high-pass-filtered, and bandpass-filtered images. It is shown that in the presence of high spatial frequencies, noise, and aliasing, focusing techniques based on bandpass filters perform well. The focusing techniques are implemented on a prototype camera system called the Stonybrook passive autofocusing and ranging camera system (SPARCS). The architecture of SPARCS is described briefly. The performance of the different techniques are compared experimentally. All techniques are found to perform well. The energy of low-pass-filtered image gradient, which has better overall characteristics, is recommended for practical applications.

A half-aperture shearing interferometer for collimation testing is proposed. It consists of a wedge plate, two plane mirrors, and two baffles. Detailed analyses for three configurations of this system are presented.

An erbium-doped fiber laser utilizing a broadband mirror as the end reflector and an intracore Bragg grating as the output coupler is designed and developed. This arrangement is used as a laser sensor to improve interrogation efficiency of intracore Bragg gratings over broadband sensor interrogation methods. Wavelength tuning of the fiber laser has been achieved by varying the temperature and strain on the Bragg grating, demonstrating an improved SNR with respect to the previous techniques that use broadband interrogation of the Bragg grating sensor.

We report the measurements of the change of the spontaneous emission coefficients of Ar ion in the high-intensity laser field by means of a quasi-sidelight method and a spatial filter technique. The variances of A coefficients are found depending on the changes of orbital angular momentum ΔL and total angular momentum ΔJ of Ar ion and the intensity of the light field in the laser cavity.

Based on image theory under incoherent illumination, the requirements of focus and distance between two gratings are discussed for the Lau effect under incoherent illumination by means of a divergent beam. The relationship between the pitch of the Lau fringes and the geometric parameters of the optical system is also discussed. Our conclusion expands former achievements. The experimental results agree with those of the theory.

Filtering of noise-corrupted images is an important problem in image processing. We propose several iterative algorithms for image filtering that are based on the minimization of the penalty functional describing the properties of both image and noise data. Applications of the proposed approach to image estimation from the ensemble of the noisy estimates, incomplete noisy input data, and the impulse noise ensemble are described. The demonstrated simulation results indicate that the proposed approach is applicable to some important image-filtering probems.

A regularized coherent optical processor, exhibiting considerable immunity to phase noise, is designed and used to achieve resolution beyond the diffraction limit. Regularization is achieved by means of a piezoelectric displacement of one of the feedback mirrors. The optical processor is used for real-time object restoration from noisy, diffraction-limited images. A software implementation of the regularized algorithm, for the case of a two-slit object, shows good agreement with the results obtained from the optical processor.

Signal recovery from multiplicative complex noise is proposed and demonstrated. The recovery is achieved by using two phase conjugators in series to produce a photorefractive quadratic nonlinear processor.

Nonlinear optical thresholding in the Fourier plane produces optically adaptive noise-cleaning masks that reduce additive signal-dependent noise, such as scalar multiplicative noise. We demonstrate the two-beam coupling artifact noise-reduction technique and achieve performance comparable to the Wiener filter.

An adaptive joint transform correlator is used to process the speckle fields derived from a multimode optical fiber. The system is applied to evaluate changes in the speckle field when the fiber is used as a sensor element. We experimentally demonstrate that the sensitivity for temperature measurement and for submicrometer displacement measurement can be as high as 0.1°C and 0.2 μm, respectively. The duty cycle of the proposed fiber sensing system is about 2.5 s, which is limited by the microcomputer that we have used. To extend the dynamic range of sensing measurement, an updated algorithm can be used, by which the dynamic range of sensing capability can be further extended.

The effect of reducing the resolution of a phase-only filter (POF) with respect to the target Fourier transform, while maintaining a constant filter bandwidth, is investigated. An existing procedure for the optimal design of filters with constrained complex amplitude values is modified by imposing an additional constraint on the filter resolution, and is used to design an optimal POF under such restrictions. A simple analysis is performed for an idealized target, which shows that the correlation peak magnitude significantly decreases when the filter resolution, in terms of number of subregions (pixels), falls below the target size, measured in terms of the number of smallest resolvable elements (pixels), in the input. The applicability of this analysis for real IR imagery is verified by simulation. The dependence of the correlation peak degradation, with filter resolution, on the nature of the imagery is also investigated, and it is shown that, for a given image size, high-pass filtered images are marginally more robust to filter resolution reduction than normal imagery. Finally, the effectiveness of the optimizing procedure is demonstrated by comparing the amount of filter resolution reduction that can be achieved by this procedure with that achieved by an existing nonoptimal technique.

The spectrally agile staring sensor (SASS) is an instrument system that is able to acquire image and spectrum information simultaneously. We analyze the expression of SNR and overall perlormance of the SASS system consisting of an acousto-optic tunable filter and point out improvement methods and limiting factors of the system performance. The complete SASS system setup is constructed. By means of this setup, the theoretical analysis is verified and the image and spectrum information of the simulated target is obtained. These results demonstrate the ability of the SASS to acquire image and spectrum information.

A novel method is developed to study the relation between scatterometer scattering and surface scattering, which shows that they can be expressed by an equivalent image formation process with the convolution law. Based on the physical concepts, a scatterometer is constructed and a polished silicon wafer is measured. The power spectrum density function and the autocorrelation function of the surface roughness are calculated from the measured data by the application of the theoretical analysis.

The quantum phenomena of parametric down conversion have been used for absolute measurement of the photodetector quantum efficiency of ultra-low-light radiation ranging from 10^-12 to 10^-15 W, which is equivalent to photon fluxes of 10⁷ to 10⁴ s^-1. The process of parametric down conversion gives rise to highly correlated (in time and space) photon flux pairs. We describe the method, experimental investigation, and a new device involving the measurement of the coincidence rate of photodetection of these two correlated beams of light. The coincidence is lowered by a nonunit quantum efficiency of either detection. This fact was used for the definition of the absolute value of both photodetector's quantum efficiencies.

A ray trace analysis of the spinning prism 0-switch is presented that demonstrates that a ray may be trapped between two mirrors, one of which is rotating, for a period consistent with the pulse evolution time for a 0-switched laser. The spinning prism 0-switch therefore acts as a fast gate. The laser must be pumped hard enough for a pulse to develop within the time the gate is open. The model matches the observed spatial burn patterns of the output well and allows for prediction of the temporal pulse separation of the pulses when the laser is pumped hard. The model also implies that optimization of the configuration may be possible to match the pulse development time (evolution plus pulse width) to the total time the rays are trapped and the pulse width, which should be one-quarter of the development time. The optimization would be done by varying the rotation rate and the cavity length to achieve the match.

The main thrust of our research is to prepare a low-cost solar-selective absorber from an indigenous semiconducting mineral, galena (galena aggregate and galena concentrate), for a solar thermoelectric generator. We report the results of preparation and characterization of solar-selective coatings made from galena aggregate and galena concentrate collected from the Zawar mines in Rajasthan, India. The coatings of galena are prepared by a thermal evaporation technique and exhibit high absorptivity (α~0.95 and 0.97) in the solar spectral range and low emissivity (ε 375~0.21 and 0.27) in the thermal range. Finally, these coatings were compared with synthesized PbS coating prepared in our laboratory and found to be quite comparable. The structure and composition of the coatings were studied by x-ray diffraction and electron spectroscopy for chemical analysis. Reflectance and absorption studies were made in the 0.3- to 3.1-μm spectral range.

Spectrometer calibrations have been performed at the National Institute of Standards and Technology (formerly the National Bureau of Standards) for over 10 yr using the calculable synchrotron radiation from the SURF II electron storage ring. SURF II is now a high-performance storage ring that can operate at electron energies up to 300 MeV and with over 250 mA of stored current. One beam line, operationally supported by the National Aeronautics and Space Administration (NASA), is dedicated for use as a radiometric instrumentation calibration facility for outside users.

We present a computer simulation of the analysis of an "infocus" two-dimensional (2-D) Airy disk. Two competing methods are used to calculate the coordinates of the center of this point spread function image. The first one is the classical technique that relies on the 2-D "centroid" of the image, and the second one is a more original method that uses the frequency dependence of the argument of the Fourier transform. Comparative simulations show that the latter technique [Fourier phase shift (FPS)] allows us to obtain a very good precision of better than 1% of a pixel spacing after quantization. Perturbations such as dc offset reduction, quantization noise, and additive Gaussian noise are introduced in the simulation. The results show that there is an improved perturbation immunity for the FPS method

We present new data analysis of photothermal measurements to extract the extinction coefficient k of thin films or bare substrates at 10.6 μm. We show how to obtain k by means of analytical formulation, with substrate absorption taken into account, and how to minimize experimental errors. Then, we discuss accuracy and reliability for substrates, thin films, and mirrors. Results are given for k values as low as 10^-4 for thin films and 10^-8 for substrates. Mirror reflectivities higher than 99.8% were measured

The optical properties of differently deposited amorphous carbon layers have been investigated by spectrophotometric means from the middle infrared up to the visible spectral region. The optical constants of the layers could be calculated by a numerical procedure that combines features of single-wavelength methods and multiwavelength methods. Depending on the deposition technique applied, the optical constants of the layers have been found to vary over a wide range. Thus, refractive index values could be established between 1.6 and 2.9, while IR-absorption coefficients vary between 20/cm and 40,000/cm. The optical performance of the layers is thus nonuniform and may be influenced by the selection of suitable deposition parameters. Due to the potentially wide range of optical constants of amorphous carbon, various possibilities exist for the application as an optical thin film material. Applications such as selective absorber coatings for solar physical purposes are discussed as well as mechanically and chemically resistant antireflection coatings on high-refractive index semiconducting materials (silicon, germanium).

Optical interference filters were fabricated using multilayer stacks derived from sol-gel SiO₂ and SiO₂-TiO₂ coatings. Laser processing was then used to modify the spectral properties (color) of local regions of these stacks. Changes in color were analyzed with respect to changes in the individual film thicknesses and refractive indices. Design considerations and some basic limitations of laser firing for tuning interference filter colors are also discussed.

A hybrid three-axis laser Doppler velocimeter system has been demonstrated in our laboratory. The system can monitor the motion of microorganisms in an unconstrained environment. During measurement, a computer system collects and processes time series data from the transit of a microorganism through the measurement volume. The fast Fourier transform of these data contains the motion signature of this microorganism. Because individual microorganisms can be selected from the field, ambiguity caused by multiscattering among two or more microorganisms can be avoided. With this new system, we can obtain a feature vector that relates to features of the microorganism, such as size, average translational velocity, rotation or wobbling, and flagellum beat frequency. Such a vector appears to be a useful criterion for distinguishing the species using statistical pattern recognition. Successful experiments demonstrate that the new system and technique has some unique advantages. It is possible to search for and characterize specific microorganisms, even at low concentration, in the presence of detritus. Realtime identification of many significant microorganisms should result from further study and improvement.

A new algorithm for the estimation of the minimum cost path between a pair of points in the 3-D space and it's VLSI implementation by means of a new multistate conditional 3-D cellular automata (CA) architecture are presented. The proposed algorithm establishes the minimum cost path between the source and target points along the maximum allowable change of direction on the 3-D grid in the presence of obstacles. Lines at arbitrary angles on this grid are piecewise approximated with elementary line segments along the principle axes of the grid, as well as along the diagonals of the 3-D elementary Cartesian cube and along the diagonals of the faces of this cube. The proposed algorithm guarantees to find the minimum cost path in 3-D space, if such a path exists. The VLSI implementation presented is realized by mapping the 3-D CA architecture onto a 2-D chip surface, resulting in a very high speed of operation, while the storage requirements are kept low. The die dimensions for the chip are 9.57 x 9.47 mm = 90.59 mm², and the frequency of operation under nominal operating conditions is 42 MHz. Thus, the chip is especially suitable for real-time 3-D applications, such as 3-D automated navigation, target tracking in 3-D, 3-D path planning, 3-D VLSI routing, etc.

This PDF file contains the errata for “OE Vol. 32 Issue 11 Paper CM-1113” for OE Vol. 32 Issue 11

This PDF file contains the editorial “Book Rvw: Interferogram Analysis: Digital Fringe Pattern Measurement Techniques," by David W. Robinson and Graeme T. Reid for OE Vol. 32 Issue 11