This PDF file contains the editorial “Editorial: The year 1992 in review” for OE Vol. 32 Issue 01

This PDF file contains the editorial “Guest Editorial: Optical Research in Asia” for OE Vol. 32 Issue 01

A speckle correlation method is described in which a liquid crystal television (LCTV) is used as a spatial filter to measure the paths of the lateral motion of rough objects. Two kinds of speckle patterns are generated simultaneously, consisting of speckles elongated in orthogonal directions to each other. The two-dimensional motion vector of the object can be measured in real time by correlating these patterns with static speckle patterns that are displayed on the LCTV as the references. Because these reference patterns can be renewed in real time, there is no limit for a measurable range of the present method. However, the spatial resolution and contrast of the LCTV limit the sensitivity and accuracy of the method.

A high-resolution laser Doppler velocimeter with small measurement volume is described. This instrument uses a novel frequency shifter incorporating a moving glass prism that gives stable frequency shifts up to 7 kHz and determines the velocity measurement range, which is 0.1 to 7 mm/s. The instrument has been used to measure blood flow velocities in microvessels and results are presented that demonstrate the capabilities of the system.

A novel optical signal processor has been developed for analyzing laser Doppler velocimeter output signals. Optical Fourier transform techniques are used to determine the spectrum of the laser Doppler signals, with a liquid crystal spatial light modulator used as the input device to the optical system. The optical Fourier transform is one dimensional, performed by an anamorphic lens system that performs a Fourier transform in the horizontal direction of the input plane while imaging in the vertical direction. The system is therefore capable of simultaneously analyzing multiple laser Doppler input signals. The capabilities of the system are demonstrated using both synthetic computer-generated input signals and "real" input data obtained from a laser Doppler velocimeter.

A hybrid pattern recognition system is described. It is based on a matched spatial filter (MSF) synthesized not by conventional template-matching patterns but by feature-extracted reference patterns. Some features are extracted from target objects used to recognize unknown objects. The optimum reference patterns for the filter are selected according to computer simulations. Through more than 30 simulations, four best patterns are chosen for recognition of 10 kinds of digits by the MSF. Recognition is performed not by conventional autocorrelation peaks but by cross-correlation signals because the reference patterns are not wholly the same as the input. The proposed system shows feasibility for feature-extracted pattern recognition using the multiplexed MSF.

Color is one of the most powerful and important types of visual information in various fields such as image processing, electronic imaging, and robot vision technologies. A new color character recognition system, composed of a camera, optical filters, an image board, a neuro board, and a micro computer was constructed. Using typewriter characters and backgrounds in five colors, two kinds of experiments were performed. The first consisted of preliminary experiments testing the effectiveness ofthe modified opponent-colortheory ofthe human eye for use in machine character recognition. The second was an experiment in color character recognition, in which the system recognized both characters and their colors.

Using a supersonic nozzle and a dc discharge, He^*n, and Ar^*n, clusters were formed, and their spectra radiated at VUV/XUV wavelengths. A theoretical analysis of stimulated radiation of clusters is given. The possible gain under our experimental conditions is 70% cm^-1.

A united energy model of free-electron lasers with different magnetic structures is established to calculate the energy transfer rate ofthe free-electron lasers underthe conditions of weak and strong signals, respectively. This model is simple in calculation and clear in physical meaning. It should be used to deal with various problems such as harmonic radiation, parameter variations, and so on. The model is also suitable for three-dimensional problems.

The effect of laser illumination conditions on the uniformity of the linear laser plasmas produced is investigated with time-integrated and time-resolved soft x-ray diagnostics. Evident nonuniformities along the line focus resulting from nonuniform laser intensity distributions have been observed with a conventional simple line-focusing technique. Specifically, the nonuniformity of higher charge-state ions is more remarkable than that of lower ones. A uniform linear plasma can be obtained with a new line-focusing technique that produces uniform laser illumination. Nonuniformities under uniform laser illumination are found to occur primarily in the laser heating period. Further development of time-matched and spatial uniform line-focused laser illumination will produce more uniform linear plasmas.

Three mathematical models for calculating and designing bistable optical devices (BODs) of nonlinear interference filters are compared and the necessity of using the accuracy matrix model based on the principle of thin-film optics to study optical bistabilities of nonlinear interference filters is confirmed. The relationships of important parameters, such as δl'₀, δl_t, and δl₀ with the initial detuning δ, which are very helpful in designing the BODs, are calculated and plotted. The dispersive relations of ZnSe thin-film are introduced into the method to make the theoretical method self-consistent. Finally, experimental results of a BOD of nonlinear interference filter whose construction is calculated using this method are given.

The laser induced fluorescence technique is used to investigate the influence of laser polarization on the Zeeman effect of the uranium atom. This method enables carrying out the measurement of Zeeman spectra in different directions of the magnetic field and laser polarization at uranium 591.5- and 639.5-nm lines, respectively. The obtained spectra are analyzed.

The quantum statistical properties of two field modes are studied for a three-level atom with multiphoton transition interacting with two cavity fields. By numerical calculations it is shown that, in the continual absorbing and emitting photons of the interacting system a "photon submergence," the bunching and antibunching effects of two modes, exists. In addition, the impact of the atom's one transition photon numbers and the initial mean photon number of two modes on these effects are discussed in detail.

A 4f-type optical system for performing matrix multiplication is presented. The system consists of a holographic mask and two Fourier lenses. With this system, the inner products of 4 x 8 and 8 x 4 matrices are calculated, yielding results that are in agreement with theoretical values.

Fully programmable higher order optical interconnections are described using holographic lenslet arrays and spatial light modulators. Adaptive neural net models can be implemented with this interconnection scheme. To demonstrate its feasibility, basic experiments conducted for adaptive neural network models are reported.

A method of spectroellipsometric analysis to calculate the effects of inhomogeneous layers with arbitrary refractive index profiles along the surtace normal is proposed. The expressions presented by Charmet and de Gennes in 1983 are extended to include the effects of local perturbations around the interface inside both the substrate region and the ambient medium region. The first-order perturbation is considered and the solutions are given in terms of definite integrals. Computer calculations show that deviations of the Δ and ψ spectra increase in proportion to the total amount of local perturbations. The results are compared with those of the differential program and the conventional technique of simulation and the practicality of this method is discussed.

Self-referencing collimation testing techniques are briefly reviewed. New self-referencing configurations using Talbot and doublewedge plate shear interferometric techniques are described. Setting sensitivities of various arrangements are compared.

A systematic study of the fabrication and characterization of planar optical waveguides in Z-LiNbO₃, fabricated by the proton exchange technique using orthophosphoric acid is reported. The guides are fabricated by immersing lithium niobate substrates in orthophosphoric acid for different durations. The results are compared with those for guides fabricated using benzoic acid under similar conditions. The data are analyzed to calculate the value of the diffusion coefficients. The surface index and the depth produced using the orthophosphoric acid proton exchange process is marginally higher.

Computer-generated gratings have the ability to be quickly and rapidly changed. In moiré methods, this versatility enables the election of the right grating pitch for a particular problem. Also, the ability to shift these computer gratings allows phase shifting to be applicable with no moving parts. The use of computer-generated gratings for qualitative visualization and quantitative analysis of virtually all moiré methods is described.

A method of performing shift- and rotational-invariant associative memory is proposed. The method can be implemented both optically and digitally with computers. The method is detailed and some results of the digital implementation are presented. The experimental results show that the original reference pattern is recovered by partial inputs in any orientation. If the input is not the original reference pattern or a partial version of it, the results produced by this method are unidentifiable.

The recovery of an optical beam, distorted by a turbulent medium with random gain (loss), using phase conjugation is investigated. Turbulence broadens the beamwidth and the random gain enhances the broadening effect. Meanwhile, the backscattering enhancement effect occurs because there is a coherent addition of the forward incident beam and the backscattered beam by a phase conjugate mirror (PCM). For comparison, the beam reflected by a conventional mirror is also considered. The enhancement backscattering effect is stronger for a PCM than for the conventional mirror. It is found that when the random gain exists, the enhancement effect is enhanced and becomes stronger when either the characteristic length or fluctuation strength of active molecule number density of the turbulent medium is increased. The average reflected beam intensity is evaluated using the path integral technique.

An equivalent circuit is developed for a single well resonant tunneling diode (RTD). Based on this equivalent circuit, the current-voltage (I-V) characteristics of vertically integrated resonant tunneling diodes (VID) are analyzed, assuming each RTD is quantum mechanically isolated from the others. By using a piecewise linear technique, the I-V curve of the multipeaked VID is divided into several regions, and the model of each region is developed and simplified individually. By incorporating the switch model of SPICE circuit simulator, the individual models are combined to form a complete VID model so that the VID model can be used with the SPICE circuit simulator. The simulated result of a four-bit VID-based A/D converter using this model is shown.

A new technique for calibrating a camera with high accuracy and low computational cost is proposed. The geometric camera parameters considered include camera position, orientation, focal length, radial lens distortion, pixel size, and optical axis piercing point. With this method, the camera parameters to be estimated are divided into two parts: the radial lens distortion coefficient κ and a composite parameter vector c composed of all the above-mentioned geometric camera parameters other than κ. Instead of using nonlinear optimization techniques, the estimation of κ is transformed into an eigenvalue problem of an 8 x 8 matrix. The method is fast because it requires only linear computation; it is accurate because the effect of the lens distortion is considered and because all the information contained in the calibration points is used. Computer simulations and real experiments show that the calibration method can achieve an accuracy of 1 part in 10,000 in 3-D measurement, which is better than that of the well-known method proposed by R. Y. Tsai.

A robust property of transform encryption coding for channel and quantization noise is presented. In transform encryption coding, the signal is prefiltered before transform coding. Therefore, a postfiltering process is necessary to reconstruct the signal from the transform coding. It is shown thatthe prefiltered signal is unrecognized and, thus, that signal encryption is achieved. Owing to the requisite postfiltering process, the channel and quantization noise spread all over the reconstructed signal from transform encryption coding, and become less visible. In addition, transform encryption coding not only increases the compression ratio, quality, noise insensitivity, and security level of the coded signal but also removes the blocking effect. It can be considered, therefore, as a combined source-channel coding scheme and is suitable for the applications related to noisy channel communications.

This paper describes aging and thermal degradation influences on the performance of multiple-stripe and broad-area GaAlAs semiconductor diode lasers operating continuously at high power. Multiple-stripe and broad-area lasers emit large output powers (4 and 5 W) and large efficiencies (39 and 50%) at currents of 4 and 7.2 x I_th. At high currents of 4 x I_th multiple-stripe lasers emit beams containing multiple modes. These beams can have small consistent θ_pd divergences (13 deg) making it easy to couple into optical fibers for applications. Current increases in multiple-stripe lasers have little effect on their performance. Broad-area lasers can emit a single ν = 8 mode at currents up to 4.3 x I_th but have large divergences (60 deg) making it difficult to couple into optical fibers. During burn-in, aging lasers can emit erratic optical beams. After aging, the output power and efficiency of a multiple-stripe laser decrease (3 and 6%), while that of a modified multiple-stripe laser increase (3.5 and 5%). Thermoelectric cooling instead of heat-fin cooling increases the output power and efficiency of a multiple-stripe laser (7.4 and 6%), and longer shot intervals increases the output power (5.4%). Modified multiple-stripe and broad-area lasers emit similar broad beams centered on their optical axes, and the beams get broader as current increases.

The problem of removing degradation and blur is common in signal and image processing. While Gaussian convolution is often the model for the blur, no exact deblurring techniques for the Gaussian kernel have been given. Previously, a Gaussian deblurring kernel in the continuous domain has been presented. We present an exact deblurring method for the discrete domain where linear convolution is replaced by matrix multiplication, the Gaussian kernel is replaced by a highly structured Toeplitz matrix, and the deblurring kernel is replaced by the inverse of this blur matrix. To bypass numerical errors, the inverse is derived analytically and a closed-form solution is presented. In particular, the matrix is decomposed into the product of triangular matrices and a diagonal matrix, where numerically ill-conditioned elements are gathered and that allows for a direct accurate handling of numerical errors. This exact inverse is effective in degradation problems characterized by low noise and high representational accuracy and has potential application in the many areas where a Gaussian point spread function is relevant.

The use of a (CCD) with an interferometer, such as a Fabry-Pérot, poses some problems because of the circular symmetry with the interferometer and the rectangular arrangement of the CCD. Integrating the fringe pattern along a row or column results in a signature that can be inverted to recover the fringe. The methods of constrained linear inversion are used to significantly improve the quality of the inversion.

We present guidelines for the performance of multilayer mirrors and filters for imaging the earth's inner magnetosphere by isolating the 304-Å He⁺ emission. Our analysis shows that the combination of filters and multilayer mirrors for an inner magnetosphere imager must attenuate the 1216-Å Lyman α emission by six orders of magnitude and the 584-, 834-, and 1026-Å background emissions by three orders of magnitude relative to the 304-Å signal. Multilayer mirrors with the highest possible reflectance at 304 Å are needed to preserve as much of the low-intensity 304-Å signal as possible. The design of multilayer mirrors is discussed, and the results of an exhaustive computer search for the best multilayer mirror design for 304-Å radiation are presented and analyzed. The theoretical performance of these new multilayer mirror designs is significantly better than that of designs currently used for imaging the solar 304-Å emission. Promising materials for normal-incidence multilayer mirrors for 304-Å radiation are B₄C, Be, Si, or SiC used with Al, Mg, or Mg2Si. Promising materials for a filter for this application are Te passivated with Si, or a combination of Al or Si with B or C.

The PDF contains the communications for the paper, "Modification of the Carre phase-stepping method to suit four-wave holographic interferometry."

This PDF file contains the editorial “Book Rvw: Modern Lens Design, A Resource Manual," by Warren J. Smith and Genesee Optics Software, Inc for OE Vol. 32 Issue 01

This PDF file contains the editorial “Book Rvw: Industrial Lasers and Their Applications," by James T. Luxon and David E. Parker for OE Vol. 32 Issue 01