Lately the SPIE journals editorial staff has been scanning additional pages of the manuscript so that I can get a better feel for the quality of writing beyond the abstract before I assign an Associate Editor to the paper. Based on my ability to understand and follow the initial exposition, I can decide whether to assign the paper or return it to the authors without review with an appropriate explanation. Although this may seem a bit severe, I believe the authors and the reviewers will gain in the long run because the reviews will be more timely and we do not place demands on our reviewers that make their evaluation more difficult.

Progress in the development of solid state lasers has come at an ever increasing rate in recent years. As improved solid state laser materials and higher quality nonlinear optical crystals have become available, advances in the range and scope of solid state lasers has continued to expand.

The behavior of an electrooptic Q-switch in a high-average- power laser is presented. Absorption of laser radiation produces heating of the electrooptic crystal which degrades laser performance. A large increase in output energy stability is achieved by employing a switching voltage pulse of the special temporal shape to the Pockels cell. The optimum pulse waveform has been calculated to reduce the Q-switching intracavity loss to zero at the instant a laser pulse occurs. We have compared the laser performance with the conventional rectangular pulse shape and the calculated one. The experiments have demonstrated that at the novel shape of pulse the permissible temperature range of the laser performance without adjustment of switching voltage was extended by a factor of 2-2.5.

By using GaAs as an output coupler as well as a saturable absorber, passive Q-switching of an arc-lamp pumped Nd:YAG laser has been demonstrated. The shortest pulse duration obtained was 77.6 ns, corresponding to a pulse energy of 34 ?J. The laser average output power was 2.1 Wwith a power density in GaAs at 1.5x 103 Wcm-2 No optical damage to GaAs was observed without any active cooling.

We present the properties of a tunable blue laser obtained from a laser-diode (LD)-pumped Cr:LiSAF solid state laser doubled by KNbO3 (KN) crystal. We show the calculations for KN crystal phase matching in the xy, yz, and xz planes, the effective nonlinear coefficient and the noncritical phase-matching (NCPM) temperature tuning. We analyze the practicality of a temperature-tuned and LD-pumped blue laser that uses KN and investigate the relation between the output wavelength of a KN-doubling Cr:LiSAF laser and the temperature variation. The temperature-tuned blue laser with continuous output from 423.5 to 446 nm is obtained with a temperature range of -5 to 100°C.

Continuous wave red, green, and blue laser light are generated under IR-pumping crystals of Nd3+:YAl3(BO3)4 by a Ti:sapphire laser. The red (669-nm) and green (532-nm) radiations are obtained by self-frequency doubling of the fundamental laser lines at 1338 nm (4F3/2?4/13/2 channel) and 1062 nm (4F3/2?4/11/2 channel), respectively. Blue laser radiation (458 nm) is achieved by self-sum-frequency mixing of the main laser line at 1062 nm and the pumping radiation at 807 nm. The main spectroscopic and nonlinear properties of this crystal are included. In addition, a simple model devoted to optimizing the blue radiation is provided.

The mathematical formulae of the optical path length and the negative group-velocity dispersion in a single-prism and wedge mirror system in a Ti:sapphire laser are given. Both the theoretical analyses and the experimental results show that the group-velocity dispersion is directly proportional to the distance between the prism and the Ti:sap- phire crystal, and the amount of the negative group-velocity dispersion generated by a single-prism and wedge mirror system may approach that generated by a pair of prisms.

A model for optimization of fiber-coupled diode-laser end- pumped solid-state lasers, which describes the pump beam by its M2 factor, is proposed. Using the mode-overlap integrals of a four-level laser, numerical investigations were carried out to obtain the pump beam optimum focusing conditions that ensure a minimum threshold pump power and a maximum mode-matching efficiency at a given laser beam spot size. For the purpose of design simplicity the numerical data were fitted with analytical functions of laser mode volume, pump beam M2 factor, and active medium absorption efficiency at the pump wavelength. With a simple output-to-input power relation, these formulas provide a straightforward procedure to design the optimum laser resonator and the coupling optics and to determine the expected output power. To show the model utility a Nd:YAG medium, end-pumped with fiber-coupled diode-laser systems of different M2 factors, was considered. A good agreement between experiments and theory was obtained.

We describe a real-time automatic target recognition (ATR) system that employs a state-of-the-art optical correlator. The system's ability to acquire and track a moving vehicle target against a densely cluttered natural background is investigated using six test image sequences obtained from a scanning IR sensor array mounted on an airborne platform. The approach adopted for the evaluation is to first optimize a number of system parameters, using what we considered to be one of the better test sequences, and then to test the system with the optimum configuration on the remaining sequences. The system performance is quantified by measuring its receiver-operating-characteristic curves against each test image sequence. Although successful acquisition and tracking of the target is demonstrated for some test sequences, there are numerous occasions on which the system acquired and tracked false alarms. This is primarily because edge features alone are an insufficient discriminator. We therefore conclude that the system evaluated does not exhibit the desired robustness for the acquisition and tracking of vehicles in densely cluttered natural scenes. Finally, these results are compared with those produced using a digital simulation of the ATR system's algorithmic processing chain. Comparison shows that for all practical purposes the performances are equivalent.

In this paper, modeling of contours by a time-varying autoregressive (TVAR) model is considered. In general, a contour function is not a stationary process, and stationary models are often unsatisfactory in representing local features. Recently, there have been advances in time-series modeling of nonstationary processes. In a typical TVAR modeling approach, autoregressive coefficients are expanded as a linear combination of deterministic functions. In this paper, a low-order discrete Fourier transform (DFT) is used to expand autoregressive coefficients. It is based on the fact that a contour is represented by a complex function, and the model coefficients need to be expanded by a set of complex functions. The parameter estimation and order selection in TVAR models are also considered. A least squares estimator of the TVAR model parameters is presented, and the maximum likelihood approach for determining the model order is also presented. The efficacy of the TVAR modeling approach in modeling a closed contour is demonstrated by estimating the time-varying spectrum of a synthetic contour by different approaches, and is tested by detecting curvature extrema points of synthesized contours. For the classification of contours of planar shapes, the estimated TVAR model parameters are used as features. A neural network is used to classify TVAR features extracted from complex contour functions. In the classification experiment with contours of various planar shapes, about 97% of samples are correctly classified.

Flexible micro-endoscopes produce images having a 'honeycomb' pattern ('noise' component) due to the spaces between the individual optical collection fibers of the imaging conduit. Upon Fourier analysis, this pattern was found to exhibit a definable spatial frequency discrete from that of the actual image of interest. A simple band-reject frequency filter was defined to allow removal of this 'noise' component of the image. By applying the filter and by sharpening the contrast between adjacent pixels, it was possible to remove the honeycomb pattern without significant degradation to the quality of the image. The advantages and limitations of the image processing technique are discussed in light of implementing this image processing technique for real-time elimination of this objectionable honeycomb pattern emanating from endoscopes made with fiber optic conduit.

The performance of a multichannel optical heterodyne continuous-phase frequency shift keying (CPFSK) system is analyzed under the combined influence of receiver shot and thermal noises, interference from adjacent channels and fiber chromatic dispersion. The bit error rate characteristics of the system are evaluated using the frequency domain analysis assuming a Gaussian crosstalk probability density function. The sensitivity penalty due to crosstalk interference is observed to increase when the effect of fiber chromatic dispersion is present. It thus requires a larger channel separation to overcome the performance degradation due to dispersion. The channel separation requirements with various values of intermediate frequency (IF), IF bandwidth and modulation index are determined so that the transmission capacity of the multichannel system can be depicted.

We propose and demonstrate a most important all-optical address recognition scheme for the optical asynchronous transfer mode (OATM). The control signal appears in an assigned time slot corresponding to the address information. Compared with conventional schemes, the proposed circuit consists of a simple structure. The proposed recognition circuit enables fast all-optical self-routing and contributes to a reduction of buffer size for temporary data storage in input ports.

This work studies the performance of a proposed high-speed optical fiber local area network based on wavelength division multiplexing (WDM) and asynchronous transfer mode (ATM). The design optimizes the usage of resources by assigning different types of traffic to two overlapping sub-networks. The WDM segment is a circuit-oriented network for high-speed traffic. The ATM sub-network handles control, low speed traffic and overflows of the WDM network. Each network is supported by one of two types of channels. The ATM channel employs conventional ATM cells for all stations using a 1300-nm wavelength carrier. The WDM channel which is assigned dynamically for very high-speed applications operates at 1500 nm band. The application of an ATM network to handle the overflow traffic reduces blocking in the system by approximately 13% for a 32 WDM system. However, depending on the load, it may increase the delay between 5% to 30%. In addition, employing an adequate queuing policy, we may reduce the blocking by 30% while increasing the delay by 5%. We may conclude that the network is more efficient handling the traffic load compared to a simple circuit switched WDM network.

The pairwise nearest neighbor (PNN) algorithm is a well- known method for the codebook construction in vector quantization and for the clustering of data sets. The algorithm has a simple structure and it provides high quality solutions. A drawback of the method is the large running time of the original (exact) implementation. We prove the monotony of the merge costs of the pNn. The monotony property is utilized to speed up an existing PNN variant. The idea is to postpone a number of distance calculations. In this way, we can reduce the computation by about 35% while preserving the exactness of the PNN.

Phase Doppler methods that measure the diameter of moving spherical particles are sensitive to particle trajectory effects that cause a phase error under Gaussian beam illumination. This error results from the interference between reflected and refracted rays from the particle. We first numerically estimate the particle trajectory effect using the geometrical optics approximation and the generalized Lorenz-Mie theory (GLMT) and, then, discuss the optimum measurement conditions that minimize the phase error. We next theoretically and experimentally investigate a method for reducing the trajectory effect using the separation of reflected and refracted rays on the basis of the polarization change. Experimental results show the usefulness of this method.

To reproduce the natural color of an object through color imaging systems, the range of the reproducible color, i.e., the color gamut, of the color display devices must be expanded, because the color gamut of current display devices such as cathode ray tubes (CRTs) and liquid crystal displays (LCDs) is insufficient. We present a new method to enlarge the color gamut for the LCD device using more than three primaries, i.e., multiprimaries, generated by a diffraction grating and a liquid crystal panel. The optical system for the multiprimary color display is introduced, and its capability of increasing the gamut is discussed. The experimental result displayed by seven primary colors is also demonstrated.

Atmospheric turbulence severely degrades the performance of ground-to-satellite optical links. Employment of adaptive optics to enhance ground-to-space optical communication systems has recently been considered and possible benefits have been shown. Uplink scintillation reduction using multiple transmitters is also being considered. What appears to be currently missing in such work is the realization that transmitter beam size is a crucial design parameter and its optimum value changes continuously according to changing turbulence conditions along the propagation path. We emphasize this point and propose a configuration in which the uplink transmitter beam size is controlled in real time in response to measured turbulence parameters to maximize mean intensity and minimize fluctuations on the satellite receiver. The full analytical evaluation is not tractable, but semianalytic simulations can be run to explore the improvement for different scenarios and site conditions. Some preliminary simulation results are presented and the difficulties hindering the achievement of more meaningful results through simulation are discussed. Controlling the beam size, especially by a factor of 2 or so, in relatively long time scales should not be a problem. The technology is sufficient to design an experiment to prove its feasibility.

A method to obtain the electromagnetic scattering properties of step discontinuities between integrated optical waveguides is presented. The method involves a new generalized scattering-matrix concept, together with the generalized telegraph-equation formalism and the modal matching technique. Our model encloses the optical waveguides with perfectly conducting walls. Reflection, transmission, and radiation coefficients can be obtained for step discontinuities in monomode or multimode optical waveguides with arbitrary refractive index profile functions. Furthermore, the method can be applied to any cascaded set of multiple discontinuities between planar or channel optical waveguides. In this way, segmented optical waveguides, optical waveguide gratings, transitions, and tapers can be analyzed by modelization as multiple abrupt discontinuities. Excellent convergence and accuracy were observed finding the optical waveguide modes. Results on convergence and accuracy for effective indices, as well as for radiation losses for step discontinuities, are given and compared with those presented by other authors.

Correlation using binary images is suited to efficient digital realization or convenient optical implementation. Binarization algorithms are required in order to match grayscale imagery to these binary correlation architectures. We present several novel point-wise and block-wise binarization techniques all of which outperform the grayscale matched filter for large values of input signal-to-noise ratio (SNR=0dB). We discuss direct binarization methods based on global thresholds, local thresholds, histogram equalization, edge-enhancement, and statistical binarization, as well as indirect methods based on auto- and crosscorrelation techniques. These point-wise methods are shown to offer poor noise tolerance and a new block-wise binarization method is introduced to enhance recognition at low values of SNR. This block-wise technique is motivated by vector quantization-based image compression and offers performance superior to the grayscale matched filter for an input SNR as low as -12 dB.

Phase-stepped interferometry is a well known technique for the measurement of surface deformation. Since in this technique phase characteristics of a linear system is computed using the arctangent function, in some points the raw phase data exceeds the value 2?. Moreover the surface roughness, phase unwrapping, and extra noise imposed from the environment makes the surface look like an original surface with huge impulsive noise and simply using PSI technique does not produce an accurately reconstructed surface. In this paper, a filtering technique is proposed that suppresses the noise and enhances the image quality. It is shown that the raw phase data prefiltered by a mean filter eliminates Gaussian noise. Then, after proper unwrapping treatment, the data should be filtered with a rank conditioned median (RCM) filter. The RCM filter is very effective at treating impulsive type noise while preserving step edges without blurring.

The current research demonstrates the effectiveness of silicon as a transmissive material for use within the far infrared wavelength range of 20 to 160 microns. This study involves samples with a wide range of resistivities and temperatures including: n-type Si of 4000, 2000, 160, 65, 12, and 2.6 ohm-cm and p-type Si of 500 and 60 ohm-cm within a temperature range of -100°C to 250°C, as well as n-type Ge of 39, 25, 14.5, 5.0, 2.5, and 0.5 ohm-cm within a temperature range of -100°C to 100°C. Far infrared absorption mechanisms are briefly discussed. The experimental transmission data are used to discuss the interaction between absorption by lattice resonance and free carrier mechanisms. The effect of room temperature resistivity on silicon's far infrared transmission characteristics is shown. The primary free carrier scattering mechanism, at elevated temperature, is shown to be acoustic phonons. Highly resistive silicon is found to be an excellent transmissive material in the far infrared. These results may be used to develop silicon and germanium optical systems in the far infrared range.

The optical method coherent gradient sensing, a real-time lateral shearing interferometry, is proposed for measuring contact stress fields under static and dynamic loading conditions. Feasibility of the method is first established under quasi-static conditions. Under dynamic conditions, the method has been used in conjunction with high-speed photography. The interference patterns representing stress gradients are used for extracting impact load history. Loading rates of approximately 14 MN/sec have been observed. The optical measurements are compared with the computed values obtained using finite element simulations.

A novel sine transform based preconditioned conjugate gradient (PCG) method for signal restoration is presented. If the bandwidth 2? +1 in the model matrix is a constant, then the asymptotic complexity for the new algorithm is O(N) per iterative step, where Nis the order of the model. This complexity is reduced by an order of magnitude in comparison with the known fast Fourier transform (FFT) technique proposed recently in the literature. Moreover, if ? has a size similar to N, then the new PCG method is accomplished by the fast sine transform (FST) and the fast Hartley transform (FHT). The computational and storage cost per preconditioning step for the new PCG method is reduced by 50% as compared to the FFT approach. To stabilize the computation, a special Tikhonov regularization is introduced. Numerical experimentations show that the new PCG method is of a speedy convergence rate. The new PCG methods maintain less computational complexity per iterative step and have a better convergence rate than the other known PCG methods.

Single-stripe structured light (SSSL) sensors are widely used in conjunction with arc welding robots for seam-tracking purposes. The interaction of the projected light with the weld joint and component surfaces produces characteristic line shapes with feature points that can be recognized at high speed by an underlying vision system. Unfortunately they are suitable only for the major classes of weld joint typically encountered within industry long, straight, or gently curving fillet or butt joints. We present a multistripe structured light (MSSL) sensor that detects and measures the position of the saddle type weld joint formed by two small (<50-mm)-diameter intersecting tubes. The underlying image processing algorithms detect the weld feature points from each stripe along with four calibration points to generate the entire weld path in the robot workcell base coordinate system before welding commences. The system is validated within an existing welding application: detecting 93% of the weld feature points within ±0.4 mm when used on 30-mm-diam tubes.

Image texture is analyzed to provide a series of features for the classification of several sets of images. Images of meat slices are processed to classify various samples of bovine muscle as a function of three factors: animal age, muscle and castration. The different images present a particular texture that is a global representation of the connective tissue. The aim of texture analysis is to extract specific features for each kind of meat. The meat slices available for this study came from 19 animals, including 10 castrated animals. Their ages were 4 months (10 animals), 12 months (5 animals) and 16 months (4 animals). The same three muscles were studied for each animal. The texture analysis was carried out on digitized images using the first- and second-order statistics of the gray levels and morphological parameters, for the characterization of the marbling. Two classification methods were implemented: the method of the k-nearest neighbors and a method based on neural networks. Both methods give comparable results and lead to satisfactory classification of the samples in relation to the three variation factors. The correlation of the textural features with chemical and mechanical parameters measured on the meat samples is also examined. Regression experiments show that textural features have potential to indicate meat characteristics.

Wavefront reconstruction from its intensity distribution in the focal plane has been studied as an inverse source problem in optics.1 Since the intensity distribution in the focal plane is related to the squared modulus of the Fourier transform of a wavefront, this problem is equivalent to reconstructing a wavefront from the modulus of its Fourier transform.

This PDF contains the communication section which includes "Measurement of in-plane displacement with twofold sensitivity using phase reversal technique".