I was appointed by the Board of Directors of SPIE in 1990 to be your editor and to start my responsibilities with Volume 30, to be published in 1991. The initial appointment was for three years with the option for three one-year extensions. I am completing my sixth year with this volume—1996.

Liquid crystal beam steering devices behave like blazed diffraction gratings: the design wavelength can be nicely diffracted into a single order. Unfortunately, the grating nature of these devices causes strong angular dispersion of the transmitted light when the incident beam contains a broad spectrum of wavelengths. We characterized the behavior of a liquid crystal beam steerer for broadband illumination. We report experimental measurements of the impulse response of the beam steering device as a function of illumination wavelength. We also compare our results to a theoretical analysis utilizing the beam-propagation method (BPM). We find that even a simple model of the phase profile gives good agreement with the experimental measurements.

We demonstrate optical code-division multiplexing (OCDM) systems using a new optical orthogonal code (OOC) to support multirate and variable-rate data communications. An important characteristic of the proposed codes is that their autocorrelation and cross-correlation operations are dependent only on each individual code word rather than a periodic pulse sequence at the input of OCDM receivers. Consequently, multirate and variable-rate data communications are offered without violating cross-correlation and autocorrelation constraints of 1. This is achieved without increasing any system complexity. Compared with conventional OOCs, our proposed codes not only can have shorter code-word lengths for multirate and variable-rate data communications, but also have high flexibility and performance. Experimental OCDM systems using the proposed code are also carried out.

Image acquisition proceeds in three phases, namely optical coupling, image sensing, and signal conversion, resulting in the perspective image, sensed image, and acquired image, respectively. The asynchronous signal conversion between video camera and image grabber elicits the phase drift, a limiting factor of the image resolution. We pioneer in experimentally verifying the existence of random phase drift, contribute to estimating the phase-drift-induced mensuration uncertainties, and explore a low-cost detection method that identifies the phase drift at the subpixel level. Experimental results are reported. A frame-by-frame compensation method for the phase drift of each scan line, which employs the proposed detection method, is suggested.

A joint transform correlator incorporating the coordinate transformation technique is proposed to perform invariant pattern recognition. Instead of an input image or its Fourier transform intensity being mapped, the Fourier transform of the input image is directly transformed from rectangular into logarithmic-polar coordinates. All information is saved, and as a result, multiple objects can be processed simultaneously. A binary optical component is designed and fabricated to perform coordinate transformation with high efficiency. Further, a Dammann grating is applied to generate a two-periodicity mapped reference image to overcome correlation peak dropping due to the cyclic shift of the mapped image along the ? axis when the target is rotated.

This work studied the effect of transition metal implantation on the dc photoresponsivity and frequency response of both n- and p-type InAlAs/InGaAs metal-semiconductor-metal photodetectors. A thin (500 Å) InAlAs layer was grown on 1 ?m thick InGaAs to raise the Schottky barrier height of the metal–semiconductor interface. Multiple energy Fe and Ti implantation was performed into n- and p-type layers, respectively, to obtain uniform implant concentrations over the entire depth of the InAlAs/InGaAs layers. The Fe implantation caused an increase in photoresponsivity and a decrease in bandwidth, whereas the Ti implantation resulted in a decrease in photoresponsivity and a slight increase in bandwidth compared with the no-implantation case.

We describe the design, construction, and performance of the first real-time autostereoscopic three-dimensional (3-D) display based on the partial pixel 3-D display architecture. The primary optical components of the 3-D display are an active-matrix liquid crystal display and a diffractive optical element (DOE). The display operates at video frame rates and is driven with a conventional VGA signal. Three-dimensional animations with horizontal motion parallax are readily viewable as sets of stereo images. Formation of the virtual viewing slits by diffraction from the partial pixel apertures is experimentally verified. The measured contrast and perceived brightness of the display are excellent, but there are minor flaws in image quality due to secondary images. The source of these images and how they may be eliminated is discussed. The effects of manufacturing-related systematic errors in the DOE are also analyzed.

A novel and extremely accurate near Gaussian approximation for the fundamental mode in single-mode fibers having arbitrary index profiles is proposed and verified by the variational method. The spot size calculated from our approximation matches closely the analytical and exact numerical results for step and parabolic index fibers over a large range of values of the normalized frequency V. For the low V region where the Gaussian approximation is not accurate, our results are suitable to accurately predict the propagation characteristics of devices such as directional couplers involving evanescent field coupling.

Analytic methods involving gravimetric analysis and titration have been developed for the determination of the coating thickness of thin films used in the preparation of IR-transmissive, hollow glass waveguides. These methods not only provide a highly accurate means of determining the film thickness but also, in the case of the dielectric layer, a method for controlling and monitoring the dielectric film during the fabrication process. That is, a correlation made between the AgI thickness and the iodination time using titration methods has led to more uniform coatings. A gold-coated hollow waveguide for applications in harsh environments has also been developed. Gold films are successfully deposited on the inner surface of the glass tubing with good adhesion when a silver layer is deposited between the glass and gold surfaces. The visible and near-IR spectrum measured shows that the surface of the Au film is very smooth.

Axially astigmatic surfaces have different curvatures in orthogonal diameters. Toroidal and spherocylindrical optical surfaces are two mathematically different special cases of axially astigmatic surfaces as noted by Menchaca and Malacara (1986), but they are almost identical in the vicinity of the optical axis. The difference between these two surfaces increases when the distance to the optical axis increases. We study the general properties of astigmatic surfaces and some special interesting cases.

It is shown that a roof Dove prism is a typical circular beam deflector used in a transmitted parallel beam. Apparently, the importance of this prism is for its multifunction. However, it is unfavorable because of its high value of length-aperture ratio, which imposes restrictions on extending its application to many cases. To overcome the difficulty, a new type of roof Dove, i.e., a square-sectional roof Dove prism and its arrays are developed to reduce greatly the length-aperture ratio. In addition, Dove prisms are used in a certain kind of series of two to form a circular beam deflector. Arrays in the same kind of series also greatly reduce the length-aperture ratio. The potential of these new types of reflecting prisms and prism arrays will rely on the development of fabrication techniques as well as on further research.

A technique for aligning doublet and triplet lenses is described. The first lens is fixed to the apparatus by means of a vacuum pump and aligned using an interferogram produced by the reflected beams from the front and back lens surfaces. To obtain a measurement of the residual decentering of the doublet or triplet lens, the present technique utilizes the displacement of a reference beam that is produced after passing twice through the lens. The precision of the measurements can be suitably modified by changing the setup parameters.

A technique for measuring the parallelism of the surfaces of transparent and nontransparent plates is presented. To obtain a measure of the wedge angle between the two surfaces of the transparent plate, the technique utilizes the displacement of a laser beam that is produced after passing through the sample twice. To measure the parallelism in nontransparent plates a Twyman-Green interferometer is used in conjunction with the apparatus described for measuring transparent plates. In this case, the displacement of the laser beam is produced after reflection off a single face of the plate. In both cases, the measurements can be made visually with the aid of an electronically generated circular scale stored on a personal computer, or automatically by the same computer. The precision of the measurements can be suitably modified by changing the setup parameters.

The goal of data compression is to find shorter representations for any given data. In a data storage application, this is done in order to save storage space on an auxiliary device or, in the case of a communication scenario, to increase channel throughput. Because remotely sensed data require tremendous amounts of transmission and storage space, it is essential to find good algorithms that utilize the spatial and spectral characteristics of these data to compress them. A new technique is presented that uses a spectral and spatial correlation to create orderly data for the compression of multispectral remote sensing data, such as those acquired by the Landsat Thematic Mapper (TM) sensor system. The method described simply compresses one of the bands using the standard Joint Photographic Expert Group (JPEG) compression, and then orders the next band’s data with respect to the previous sorting permutation. Then, the move-to-front coding technique is used to lower the source entropy before actually encoding the data. Owing to the correlation between visible bands of TM images, it was observed that this method yields tremendous gain on these bands (on an average 0.3 to 0.5 bits/pixel compared with lossless JPEG) and can be successfully used for multispectral images where the spectral distances between bands are close.

The Joint Photographic Expert Group standard provides a block smoothing method, that can be used to improve the visual quality of images reproduced from the dc coefficients alone. The method predicts ac coefficients of a block in terms of the dc values of the surrounding blocks. This note presents a new set of prediction equations. Experiments show that the proposed equations produce noticeable improvements in the visual quality of the reconstructed images.

A method for characterizing tumoral masses in mammograms is described. It is based on two significant features of breast cancer, namely the degree of spiculation and the presence of fuzzy areas in the boundary of the tumor. The quantization of these features is performed by means of polar and pseudopolar representations of the neighborhood of the tumor to take advantage of its symmetry . The degree of spiculation is deduced from a shape parameter that characterizes the irregularity of the boundary after enhancing divergent structures. The radial component of the gradient on the boundary provides a measurement of fuzzy appearance. In the next step, the identification of malignant and benign tumors is achieved with a two-level hierarchical classification using a Bayesian classifier. A set of 19 masses are processed and results are presented and discussed.

If a point on an object passes over two or more photoreceptors during image acquisition, a blur will occur. Under these conditions, an object or scene is said to move fast relative to the camera’s ability to capture the motion. This work considers the iterative restoration of images blurred by distinct, fast-moving objects in the frames of a (video) image sequence. Even in the simplest case of fast object motion, the degradation is spatially variant with respect to the image scene. Unlike previous work, the blur is allowed to vary at each pixel. A robust (edgepreserving) iterative approach is used that requires complete knowledge of the blur point spread function to restore the scene. The blur of a moving object in a single frame is often underspecified. An estimate is obtained of the blur point spread function (PSF) to within a constant scaling factor using motion information from the displacement vector field for that frame. The iterative restoration approach used allows for the incorporation of prior knowledge of the scene structure to facilitate the restoration of difficult scenes. A bilinear approximation to the continuous PSF derived from the motion estimate to restore noisy (MPEG degraded) motion-blurred image sequences is proposed. The results of this work reinforced the well-known flexibility of iterative restoration approaches. The proposed approach is shown to be an important processing tool for the enhancement of motion-degraded frames in a digital video sequence.

Our aim is twofold: to present our temperature measurement system based on CCD technology, which gives a linear response versus temperature, and to display two industrial applications in which our system has been involved to optimize and characterize the process. We present a short summary dealing with temperature evaluations from radiation measurements. We consider especially the problems of the surroundings, the atmosphere, and the emissivity assumption. After selecting a value for the emissivity, we show that the use of the CCD technology enables us to obtain high spatial and temporal resolution temperature imaging, and provides further information, mainly a linear response versus temperature, which will enable real-time implementation. Our measurement system based on CCD technology is particulary dedicated to process control in the steel industry. CCD technology does not require a substantial cost and provides a lot of paramount information, enabling us to optimize some industrial applications based on accurate relative temperature measurements. We show, through two industrial examples, the results provided by our system and how it enables us to optimize the process involving knowledge and the control of temperature.

The conventional method of applying the arctangent operation at every picture element in an interferogram slows down the phaseshift technique. A method that precalculates and dynamically stores the phase combinations in the computer’s random-access memory is introduced. The appropriate value is then mapped out based on input phaseshifted intensities. Performance tests on different types of processors reveal a two to seven times increase in computational speed using the method.

A leather inspection system based on visual textural properties of the material surface is presented. Defects are isolated from the complex and nonhomogeneous background, analyzing their oriented structure. The patterns to be analyzed are represented in an appropriate parameter space using a neural network, in this way, a parameter vector is associated to each different textured region in the original image. Finally a filter process, based on knowledge about the parameter vectors representing the leather without defects, detects and classifies any abnormality. The resulting system is flexible and does not depend on dimensions, structure, and color of defects.

Rather than design an optimal filter over a large window, which may be computationally impossible or require unacceptable computation time, one can design an iterative filter, each stage of which is designed over a small window with acceptable design time. If a twostage iterative filter is designed with each stage optimally designed over a window, then the iterative filter is a suboptimal approximation to the optimal filter over the larger window formed as the dilation of the small window with itself. Using image-noise models, three basic questions regarding optimal increasing iterative filters are statistically addressed: How many iterations are required before there is only a negligible increase in filter performance? As the number of iterations increases, how good is filter performance in comparison with large-window noniterative filters? What are the logical and probabilistic relations between noniterative and approximating interative filters? Iterative-filter performance is seen to be only slightly suboptimal, in return for tractable design. A key conclusion is that, while in terms of logic there may be a significant difference between a noniterative and approximating iterative filter, their probabilistic difference as operators on random sets can be neglible. This fundamental point is discussed in the context of application to digital document processes, which form a key area of application.

The concept and algorithmic details of a new corrupted-pixelidentification- (CPI)-based estimation filter are presented. The approach is by transforming a noisy subimage centered on a corrupted pixel into its discrete cosine transform (DCT) domain, and approximating the transformed subimage by its DC (average) coefficient only, an estimation of the noise distribution is made by combining the knowledge of the number of corrupted pixels in the subimage and the pixel intensity of the noise term. This enables the DC coefficient of the restored image in the DCT domain to be determined, and from this, the restored pixel intensity can be calculated by an inverse DCT. The whole restored image can be obtained after all the corrupted pixels are exhausted. From an extensive performance evaluation, it was found that the new algorithm has a number of desirable characteristics. First, the CPI-based estimation algorithm performs extremely well when heavily degraded images are concerned. Second, the CPI-based estimation algorithm has acceptable featurepreserving properties, far better than the conventional median filter. Third, the new algorithm can be applied iteratively to the same noisy image. Fourth, the computing speed of the CPI-based estimation algorithm is almost three times faster than the conventional median filter, and 1.6 times faster than the original CPI algorithm, making it the fastest algorithm in this class so far.

The proposed approach to the detection of diffuse edges is based on three ordered operations: noise reduction, gradient generation, and edge formalization. In the first stage, an efficient two-stage median filtering scheme is introduced for noise reduction. Next, a generalized second-order gradient generation algorithm based on an efficient averaging algorithm is applied. Finally, an edge strength normalization and thresholding scheme is introduced for the edge formalization stage to eliminate the breaking up of edge contours. Simulation results demonstrating the superior performance of the proposed approach are included.

Automatic detection of time-critical mobile targets using nonimaging, spectral infrared radiometric target signatures is explored. A novel set of classification features is developed for the spectral data and utilized in a Bayesian classifier. The processing results are presented, and sensitivity of the class separability to target set, target configuration, diurnal variations, mean contrast, and ambient temperature estimation errors is explored. This work introduces the concept of atmospheric normalization of classification features, in which feature values are normalized using an estimate of the ambient temperature in the vicinity of the target. The probability of detection, false alarm rate, and total error rate associated with this detection process is presented. Testing on an array of U.S. and foreign military assets reveals a total error rate near 5% with a 95% probability of detection and a concurrent false alarm rate of 4% when a single classification feature is employed. Sensitivity analysis indicates that the probability of detection is reduced to 70 to 75% in the hours preceding daylight, and that for the total error rate to be less than 10%, the target-to-background mean contrast must be greater than 0.025. Analysis of the atmospheric normalization technique reveals that to keep the total error rate less than 10%, the ambient temperature must be estimated with less than 3 K absolute accuracy.

Processing of correlation fringes obtained from electronic speckle pattern interferometry (ESPI) requires the use of a digital filter to reduce the speckle noise. Even though smoothing algorithms based on the Fourier transform significantly suppress speckle noise, they do not preserve the image characteristics. The application of a scale-space filter to reduce speckle noise in ESPI fringes is reported. Results obtained using both computer-simulated and experimental fringe patterns are used to test the scale-space filter and they are also compared with those obtained by Fourier, convolution, and median filtering.

Photothermal phase shift spectroscopy measures the changes of the refractive index, induced by a modulated excitation light beam, by a double microinterferometer, consisting of a 7.5 × 7.5 mm integrated optics silica chip. A laser diode that is integrated at the chip is used as the probe laser. The flowthrough cell containing the analyte is mounted in one of the two arms of the Michelson interferometer between the microchip and the reflecting mirror. The great potential of this photothermal microinterferometer as a routine method for process control or environmental surveillance lies in the miniaturization of the system for the following reasons. No adjustment is needed because only fixed components are used. The quality of the light beams is significantly improved by shortening the light paths and very small sample cell volumes in the range of nano- or microliters are needed. This has at least two distinct advantages. On the one hand, a small, compact analytical apparatus enables direct real time and on site measurements. On the other hand, it is possible to build a robust and reliable device, without any movable parts, that is unaffected by external influences.

A new interference method for measuring the refractive index distribution in gradient-index (GRIN) blanks with shapes deviating from the plane-parallel is described. It uses a standard double-pass interference scheme modified to provide single passing of the beam through the investigated GRIN sample. Four interferograms recorded with one preliminary adjustment of the sample enable the restoration of the refractive index distribution in the sample, eliminating errors introduced by imperfectness of the interferometer and of sample surfaces, and the wedge shape of the sample. The method does not require information concerning the thickness and the wedge angle of a blank. The 2-D dependence of the refractive index in transverse dimensions along the sample surface can be measured with the accuracy better than 1×10-4

Nd:Sr5(VO4)3F, known as Nd:S-VAP, is a new material for efficient and miniature diode-pumped solid state lasers. By using a laserdiode pump operating at 809 nm, Nd:S-VAP is successfully lased at 1.065 ?m. A slope efficiency of 43.5% and a laser threshold of only 11 mW are measured. The theoretical formulas for threshold power and slope efficiency are written and the theoretical calculations are in agreement with the experimental results. In addition, by using KTP as an intracavity-doubling crystal, the intracavity frequency of the Nd:S-VAP laser at 0.5325 ?m is also realized. The threshold power is 13.2 mW and the TEM00 mode green laser output power is 25.6 mW at 200 mW incident pump power, corresponding to an optical efficiency of 12.8%. In addition a way to improve efficiency is discussed.

The thermal guiding effect plays a dominant role in beam formation of diode end-pumped lasers. Thermally induced aberrations occur for high pump density resulting in beam quality degradation. Thermal distortions in such lasers are investigated both theoretically and experimentally. It is found that severe wavefront distortions are generated outside the pump volume, whereas for a beam confined to pump volume the aberration effects are negligible. For high pump density these distortions result in an atypical caustics shape. This effect is examined for two cases: a fundamental mode laser pumped by a 2-W cw diode and a multimode laser pumped by a 10-W fiber-coupled bar. Two crystals— Nd:YAG and Nd:YVO4—are used as active media. The caustics shape observations and an interferometric inspection of wavefront distortion are performed. Satisfactory agreement between theory and experiments is achieved.

A high-pressure laminar flow, methane-filled Raman cell has been used for nonlinear conversion of a 100-Hz Nd-YAG laser operating at 1.06?m to eye-safe radiation at 1.54 ?m. The laminar flow is obtained between two concentric cylinders rotating at the same angular velocity. Using a noncritically phase-matched optical parametric oscillator, the same laser source was also converted to 1.57 ?m eye-safe radiation. Pump recirculation was used in both cases. Good conversion efficiencies, almost independent of the pulse repetition rate, were obtained with both conversion techniques.

A laser soldering of tape-automated bonding (TAB) leads is tried with a diode-pumped Nd:YAG laser. A 15-W laser diode bar, a multistripe monolithic laser diode array, is used to end-pump Nd:YAG. Twelve beams emitted from 12 stripes, center-to-center spaced 800 ?m, of a 1-cm linear diode array were collimated by a lens array of width 1 cm, consisting of 12 gradient-index (GRIN) lenses with 800-?m width, to pump the Nd:YAG facet. The maximum Nd:YAG output power at 1064 nm of 6.3 W is obtained in cw operation. The Nd:YAG laser beam is focused to a spot with a FWHM diameter of 112337 ?m. A TAB device with 215-?m-width leads, center-to-center spaced 430 ?m, is successfully soldered by 98-ms irradiation of the laser power of 5.8 W/lead. Soldering is tried with a fiber-coupled Nd:YAG output as well.

An optical system for analysis of diesel spray penetration and atomization has been developed. The basic system is based on a microscope with a long working distance (230 mm) and a modest resolution. The magnification is variable between 1:1 and 50:1 on the camera plane. This enables the study of individual droplets with a diameter of 5 ?m. A number of different techniques have been used together with the basic system to study different parts of the spray. They include the darkground technique, double exposure, and ordinary magnification. The size, speed, and direction of propagation of the individual droplets have been calculated using the elongation of the droplet image caused by the duration time of the flash.

We analyze the use of glancing angle Fresnel mirrors for the determination of the mutual intensity function of a partially coherent x-ray beam in both vertical and horizontal directions with variable glancing angle and by tilting one of the mirrors around the propagation direction. Analytical results are discussed in the limit of narrow mirrors and Gaussian coherence.

Six samples of phase-change optical disks made by several different manufacturers are evaluated using the developed tester. It is observed that the dependence of recording and erase characteristics on the linear velocity of laser beam scanning on the track and frequency of recording signal were very much affected by laser power. The phase jitter is measured by a proposed test method and the effects of disk tilt and mark distortion on the measured values are indicated by a computer simulation. Common testing methods are discussed and some results of common tests are presented.

We explore the possibility of enhancing very large scale integration (VLSI) electronic switch structures using reconfigurable freespace optical chip-to-chip interconnects. We present a novel technological approach to the realization of an output queued asynchronous transfer mode (ATM) switching fabric within a low-blocking, three-stage network configuration by employing both electronic and optical switching stages with reduced cross-office transfer rates. The first and third stages are implemented by the selective reading/writing from/to a sectorized optically accessible random access memory (known as opto-RAM) currently under development in our laboratory. The second (central) stage uses holographic fan-out/selective fan-in optics to implement a freespace photonic crossbar switch. We assess the performance of the ATM switch fabric using computer simulation as well as analytic techniques.

The enhancement of a laser speckle photography technique by means of a modification of the film development procedure is presented. Using a holographic film, an amplitude specklegram can be changed to a phase specklegram. This conversion is achieved during the film development procedure by a controlled bleaching of the exposed film. The contrast and visibility of Young’s fringes reconstructed from a phase specklegram are better than those from an amplitude specklegram. The diffraction efficiency of a phase specklegram is greater than that of an amplitude specklegram. The experimental arrangement and the method to get a phase specklegram are described. The phase specklegram characteristics are presented in detail and experimental results are discussed.

A tremendous number of fuzzy system-based applications are currently available. A new application of fuzzy systems theory is presented to compute the probability of target detection in cluttered infrared images. Both the Mamdani and Assilian and Sugeno’s fuzzybased models have been investigated. A data set for one vehicle has been used to model the relationships between three input parameters, the Der clutter metric, the probability of edge (POE) metric, the Schmieder variance-based clutter metric, and the experimental probability of detection value. Both fuzzy models have given excellent predictive probability of detection values that are highly correlated to the observed probability of detection values. The preliminary results obtained suggest the adequacy of fuzzy-based modeling techniques to model the perception of targets in infrared and visual scenes.

Recently the authors of this paper dealt with computergenerated holograms (CGHs) for the optical inspection of the surface roughness and waviness of relatively smooth surface roughness standards.1 The idea was to exploit two separate sensors to provide information on one hand about the surface roughness by measuring the contrast parameter as defined in Ref. 1, and on the other hand to inspect the surface curvature. Later, we improved the operational function of the surface sensor.

Recently the authors of this paper dealt with computergenerated holograms (CGHs) for the optical inspection of the surface roughness and waviness of relatively smooth surface roughness standards.1 The idea was to exploit two separate sensors to provide information on one hand about the surface roughness by measuring the contrast parameter as defined in Ref. 1, and on the other hand to inspect the surface curvature. Later, we improved the operational function of the surface sensor.

This PDF file contains the editorial “Book Rvw: Laser-Molecule Interaction," by Jean Rene Lalanne for OE Vol. 35 Issue 12

This text is billed as integrating coverage of the fundamentals of laser science with an introduction to nonlinear optics on the molecular level. From the standpoint of traditional course synopses, it may, with some charity, be more properly viewed as extending a solid introduction to laser science to give an excellent background for a later course in nonlinear optics.