scispace - formally typeset
Search or ask a question

Showing papers in "Optical Engineering in 1987"


Journal ArticleDOI
TL;DR: In this article, the morphological erosions or dilations of morphological filters are used to provide simple and systematic algorithms for image processing and analysis tasks as diverse as nonlinear image filtering, noise suppression, edge detection, region filling, skeletonization, coding, shape representation, smoothing, and recognition.
Abstract: This paper reviews some recent advances in the theory and applications of morphological image analysis. Regarding applications, we show how the morphological filters can be used to provide simple and systematic algorithms for image processing and analysis tasks as diverse as nonlinear image filtering, noise suppression, edge detection, region filling, skeletonization, coding, shape representation, smoothing, and recognition. Regarding theory, we summarize the representation of a large class of translation-invariant nonlinear filters (including morphological, median, order-statistic, and shape recognition filters) as a minimal combination of morphological erosions or dilations; these results provide new realizations of these filters and lead to a unified image algebra.

225 citations


Journal ArticleDOI
TL;DR: In this paper, a truncated series expansion of the inverse operator that maps object opacity function to hologram intensity was proposed, which is shown to be equivalent to conventional (optical) reconstruction, with successive terms increasingly supressing the twin image.
Abstract: Digitally sampled in-line holograms may be linearly filtered to reconstruct a representation of the original object distribution, thereby decoding the information contained in the hologram The decoding process is performed by digital computation rather than optically Substitution of digital for optical decoding has several advantages, including selective suppression of the twin-image artifact, elimination of the far-field requirement, and automation of the data reduction and analysis process The proposed filter is a truncated series expansion of the inverse of that operator that maps object opacity function to hologram intensity The first term of the expansion is shown to be equivalent to conventional (optical) reconstruction, with successive terms increasingly sup-pressing the twin image The algorithm is computationally efficient, requiring only a single fast Fourier transform pair

223 citations


Journal ArticleDOI
TL;DR: A survey of progressive image transmission techniques including spatial domain, transform domain, and pyramid-structured approaches, which indicates which approach is most appropriate depends upon the application.
Abstract: Progressive image transmission allows an approximate image to be built up quickly and the details to be transmitted progressively through several passes over the image. This technique appears very useful for picture communication over slow channels. This paper presents a survey of progressive image transmission techniques including spatial domain, transform domain, and pyramid-structured approaches. Image coding techniques that are not currently used for progressive transmission, but that have this capability or can be modified to provide progressive transmission, are also identified. The main features, computational complexity, and typical performance are discussed for each technique. Among various approaches, there are always trade-offs between system complexity and performance. Which approach is most appropriate depends upon the application.

210 citations


Journal ArticleDOI
TL;DR: The real-time imaging stereo matcher (PRISM) as mentioned in this paper was developed for use in robotics where noise tolerance, reliability, and speed are predominant issues, and it has been used successfully as a sensor in a path-planning system and a bin-picking system.
Abstract: A binocular-stereo-matching algorithm for making rapid visual range measurements in noisy images is described. This technique is developed for application to problems in robotics where noise tolerance, reliability, and speed are predominant issues. A high speed pipelined convolver for preprocessing images and an unstructured light technique for improving signal quality are introduced to help enhance performance to meet the demands of this task domain. These optimizations, however, are not sufficient. A closer examination of the problems encountered suggests that broader interpretations of both the objective of binocular stereo and of the zero-crossing theory of Marr and Poggio [Proc. R. Soc. Lond. B 204, 301 (1979)] are required. In this paper, we restrict ourselves to the problem of making a single primitive surface measurement for example, to determine whether or not a specified volume of space is occupied, to measure the range to a surface at an indicated image location, or to determine the elevation gradient at that position. In this framework we make a subtle but important shift from the explicit use of zero-crossing contours (in bandpass-filtered images) as the elements matched between left and right images, to the use of the signs between zero crossings. With this change, we obtain a simpler algorithm with a reduced sensitivity to noise and a more predictable behavior. The practical real-time imaging stereo matcher (PRISM) system incorporates this algorithm with the unstructured light technique and a high speed digital convolver. It has been used successfully by others as a sensor in a path-planning system and a bin-picking system.

203 citations


Journal ArticleDOI
TL;DR: In this paper, the current status of the tungsten bronze crystals SBN and BSKNN for photorefractive applications in terms of their growth, electro-optic character, and the role of cerium dopants.
Abstract: The Sr1-xBaxNb2O6 (SBN) and Ba2-xSrxK1-yNayNb5O15 (BSKNN) tungsten bronze solid-solution systems are shown to be promising photo-refractive materials. Because of the versatility of the bronze structure, both the response time and spectral response can be controlled by altering the type of dopant and its crystallographic site preference. This paper reviews the current status of the tungsten bronze crystals SBN and BSKNN for photorefractive applications in terms of their growth, electro-optic character, and the role of cerium dopants. Ferroelectric morphotropic phase boundary (MPB) bronze materials are also discussed as potentially important for future development.

158 citations


Journal ArticleDOI
TL;DR: An experimental demonstration of a holographic associative memory that utilizes an array of classic VanderLugt correlators to implement in parallel the inner product between an input and a set of stored reference images.
Abstract: An experimental demonstration of a holographic associative memory is presented. The system utilizes an array of classic VanderLugt correlators to implement in parallel the inner product between an input and a set of stored reference images. Each inner product is used to read out an associated image. Theoretical analysis of the system is given, and experimental results are shown.

158 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a definition of CCE performance and introduce a standard test tool (the photon-transfer technique) for measuring and optimizing this important CCD parameter.
Abstract: The charge-coupled device has shown unprecedented performance as a photon detector in the areas of spectral response, charge transfer, and readout noise. Recent experience indicates, however, that the full potential for the CCD's charge-collection efficiency (CCE) lies well beyond that realized in currently available devices. In this paper we present a definition of CCE performance and introduce a standard test tool (the photon-transfer technique) for measuring and optimizing this important CCD parameter. We compare CCE characteristics for different types of CCDs, discuss the primary limitations in achieving high CCE performance, and outline the prospects for future improvement.

148 citations


Journal ArticleDOI
TL;DR: It is shown that color saturation, as well as luminance, can play an important role in achieving good image enhancement and limitations to luminance and saturation processing caused by poor quantization of the RGB tristimulus images are discussed.
Abstract: Much of the work done in digital image processing has been limited in application to black-and-white images, this being especially true of enhancement and restoration. The extension to color image processing is not trivial; a suitable color space must be selected for a given application, and then a good processing strategy must be devised. In fact, we doubt that any of the available color spaces will meet the needs of all types of image processing. Many color image processing strategies require that only a luminance component be actually processed. In image restoration, for example, good results are achievable by processing only the Y component of the popular NTSC transformation from RGB to YIQ components. In this paper we show that color saturation, as well as luminance, can play an important role in achieving good image enhancement. The technique proposed is simple to implement and is based on the observation that the saturation component often contains high frequency components that are not present in the luminance component. Contrast and sharpness enhancement techniques are discussed; the computer processing algorithms are restricted to those that preserve the natural appearance of the scene. We also discuss limitations to luminance and saturation processing caused by poor quantization of the RGB tristimulus images.

131 citations


Journal ArticleDOI
TL;DR: A novel for-mulation of the state and state-transition rule that uses a perceptually based edge classifier is introduced and significant gains to be obtained are obtained by enhancing the basic VQ approach with interblock memory.
Abstract: Image compression using memoryless vector quantization (VQ), in which small blocks (vectors) of pixels are independently encoded, has been demonstrated to be an effective technique for achieving bit rates above 0.6 bits per pixel (bpp). To maintain the same quality at lower rates, it is necessary to exploit spatial redundancy over a larger region of pixels than is possible with memoryless VQ. This can be achieved by incorporating memory of previously encoded blocks into the encoding of each successive input block. Finite-state vector quantization (FSVQ) employs a finite number of states, which summarize key information about previously encoded vectors, to select one of a family of codebooks to encode each input vector. In this paper, we review the basic ideas of VQ and extend the finite-state concept to image compression. We introduce a novel for-mulation of the state and state-transition rule that uses a perceptually based edge classifier. We also examine the use of interpolation in conjunction with VQ with finite memory. Coding results are presented for monochrome images in the bit-rate range of 0.24 to 0.32 bpp. The results achieved with finite memory are comparable to those of memoryless VQ at 0.6 bpp and show that there are significant gains to be obtained by enhancing the basic VQ approach with interblock memory.

108 citations


Journal ArticleDOI
TL;DR: It is shown that the Scheimpflug condition of focusing coupled with the low divergence of a laser beam provides an ideal arrangement for large depth of view.
Abstract: The design of a compact laser scanner for robot vision is presented. The design is based on synchronized scanners. It is shown that the Scheimpflug condition of focusing coupled with the low divergence of a laser beam provides an ideal arrangement for large depth of view. A geometrical analysis and a prototype description are presented.

100 citations


Journal ArticleDOI
Shin-Tson Wu1
TL;DR: In this paper, the authors reviewed the properties and electro-optic effects of nematic liquid crystals and discussed the advantages and disadvantages of three device configurations (parallel, twisted, and perpendicular alignment) for long-wavelength applications.
Abstract: Infrared properties and electro-optic effects of nematic liquid crystals are reviewed. Physical origins and characterization techniques of infrared birefringence and rotatory power are described. Advantages and disadvantages of three device configurations--parallel, twisted, and perpendicular alignments--are analyzed. Among them, parallel alignment shows the best potential for long-wavelength applications. Several methods for improving the response times of nematic liquid crystals with emphasis in the infrared region are briefly discussed.

Journal ArticleDOI
TL;DR: In glasses, the largest observed value of nonlinear refractive index n2 is currently about 0.1 X10-11 esu as mentioned in this paper, which is dependent on the third-order electronic polarization, which can be estimated from the linear electronic polarizability or from the refractive indices and Abbe number.
Abstract: In glasses, the largest observed value of nonlinear refractive index n2 is currently about 0.1 X10-11 esu. Changes in n2 are dependent on the third-order electronic polarization, which can be estimated from the linear electronic polarizability or from the refractive index and Abbe number. Theoretical calculations of n2 have been made for some glasses with potentially high nonlinear refractive indexes. Glasses are likewise useful for the matrix of some organic compounds and semiconductors with high optical nonlinearity.

Journal ArticleDOI
TL;DR: In this article, the authors described the optical and phase equilibrium studies as well as details of the crystal growth technology that led to this advance in materials technology and described how to obtain high optical quality, oriented single crystals of AgGaS2 1 cm in cross section and more than 2 cm in length.
Abstract: Improvements in crystal growth technology have made it possible to grow crack- and twin-free boules of AgGaS2 and AgGaSe2 in comparatively large dimensions, AgGaS2 to 28 mm diameter by 100 mm length and AgGaSe2 to 37 mm diameter by 100 mm length. Although the crystals grow with optical defects (micrometer-size scattering centers), postgrowth heat treatment procedures have been used to successfully eliminate the defects and produce material of near-theoretical transparency. High optical quality, oriented single crystals of AgGaS2 1 cm in cross section and more than 2 cm in length and of AgGaSe, 1 cm in cross section and more than 3.5 cm in length have been produced and are leading to new advances in IR frequency generation. The optical and phase equilibrium studies as well as details of the crystal growth technology that led to this advance in materials technology are described.

Journal ArticleDOI
TL;DR: The role of the phenomena of "daydream-ing" in the real-time programmable optical resonator is very much akin to the role of "unlearning" in neural network memories.
Abstract: Optical resonators having holographic elements are potential candidates for storing information that can be accessed through content-addressable or associative recall. Closely related to the resonator memory is the optical novelty filter, which can detect the differences between a test object and a set of reference objects. We discuss implementations of these devices using continuous optical media such as photorefractive ma-terials. The discussion is framed in the context of neural network models. There are both formal and qualitative similarities between the resonator memory and optical novelty filter and network models. Mode competition arises in the theory of the resonator memory, much as it does in some network models. We show that the role of the phenomena of "daydream-ing" in the real-time programmable optical resonator is very much akin to the role of "unlearning" in neural network memories. The theory of programming the real-time memory for a single mode is given in detail. This leads to a discussion of the optical novelty filter. Experimental results for the resonator memory, the real-time programmable memory, and the optical tracking novelty filter are reviewed. We also point to several issues that need to be addressed in order to implement more formal models of neural networks.

Journal ArticleDOI
TL;DR: In this article, the use of lowvoltage, low power, and bistable devices to perform a variety of functions including polarization and intensity-based logic gates, input/output displays, optical crossbars, and spatial filtering masks is described.
Abstract: High-contrast, submicrosecond switching ferroelectric liquid crystal spatial light modulators have many applications to optical computing and image processing. In this paper we describe the use of these low-voltage, low-power, and bistable devices to perform a variety of functions including polarization- and intensity-based logic gates, input/output displays, optical crossbars, and spatial filtering masks.

Journal ArticleDOI
TL;DR: High resolution airborne or vehicular imaging systems are often limited in performance by mechanical vibrations, so data can be used to statistically define expected performance of high resolution systems and to aid accordingly in sensor selection.
Abstract: High resolution airborne or vehicular imaging systems are often limited in performance by mechanical vibrations. High vibration frequency MTF is known. Low vibration frequency MTF is a random process analyzed here. Average and ideal maximum spatial frequency limitations are calculated. Plots are presented to describe the number of independent images of the same object required so that at least one "lucky shot" with a given spatial frequency requirement is obtained with a given probability. Examples for short and long relative exposures are included. These data can be used to statistically define expected performance of high resolution systems and to aid accordingly in sensor selection. The probability of achieving higher resolution improves noticeably as relative exposure time is decreased.

Journal ArticleDOI
David A. B. Miller1
TL;DR: The quantum-confined Stark effect (QCSE) as mentioned in this paper is a well-known phenomenon in semiconductor devices that enables electrically controlled optical modulators and optically controlled self-electro-optic effect devices that can operate at high speed and low energy density.
Abstract: Quantum wells, alternate thin layers of two different semiconductor materials, show an exceptional electric field dependence of the optical absorption, called the quantum-confined Stark effect (QCSE), for electric fields perpendicular to the layers. This enables electrically controlled optical modulators and optically controlled self-electro-optic-effect devices that can operate at high speed and low energy density. Recent developments in these QCSE devices are summarized, including new device materials and novel device structures. The variety of sophisticated devices now demonstrated is promising for applications to information processing.

Journal ArticleDOI
J. S. Patel1
TL;DR: In this paper, the symmetry arguments that predict the existence of ferroelectricity in chiral smectic liquid crystals are presented and the structures of the ferro-electric liquid crystals in the thin and the thick cell configurations are reviewed.
Abstract: The symmetry arguments that predict the existence of ferroelectricity in chiral smectic liquid crystals are presented. The structures of the ferroelectric liquid crystals in the thin and the thick cell configurations are reviewed. The techniques to align these liquid crystals are briefly described. Finally, the effect of electric fields on these liquid crystals is discussed.

Journal ArticleDOI
TL;DR: In this paper, it is shown that the charge cloud profiles resulting from field free diffusion have broad wings that can lead to significant charge splitting between adjacent pixels, even for field-free region thicknesses ≥ 1 um.
Abstract: Depending on the device structure and hence the electric field present within a CCD, there is often a considerable time for charge clouds generated within the silicon to diffuse and spread outward before being collected at the buried channel. This charge spreading has an important effect on the spatial and energy resolution of CCDs used for soft x-ray, optical, and high energy particle imaging. Further theory on this is presented with regard to the performance of CCDs currently under development, to broaden their spectral response while minimizing the thickness of the field-free region below the depletion layer. It is shown that the charge cloud profiles resulting from field-free diffusion have broad wings that can lead to significant charge splitting between adjacent pixels, even for field-free region thicknesses ~1 um. Formulas are also presented for diffusion in the field region and the substrate.

Journal ArticleDOI
TL;DR: In this article, the authors present results of a program to enhance the ultraviolet and extreme ultraviolet response of charge-coupled devices, which can be used as a windowless imaging detector in a space environment.
Abstract: We present results of a program to enhance the ultraviolet and extreme ultraviolet response of charge-coupled devices. The ultimate goal of our program is to develop a large format device with both high and stable quantum efficiency from 100 to 3000 A that can be used as a windowless imaging detector in a space environment. Ultraviolet quantum efficiency measurements have been made for several ion-implanted and laser-annealed test CCDs specially fabricated by Tektronix for this program. Quantum efficiencies as high as 22% at 2500 A , where the absorption depth in silicon is -55 A, have been observed in one such test CCD. Quantum efficiency measurements of standard back-illuminated RCA and Tektronix CCDs are also presented.

Journal ArticleDOI
TL;DR: In this article, a buffered direct-injection (BDI) current readout for infrared detectors is described and analyzed and compared with the common direct injection (DI) circuit with respect to injection efficiency, noise, and tolerance of low RoA product photovoltaic detectors.
Abstract: A buffered direct-injection (BDI) current readout for infrared detectors is described and analyzed. It is compared with the common direct-injection (DI) circuit with respect to injection efficiency, noise, and tolerance of low RoA product photovoltaic detectors. Power requirements and threshold control are also discussed. Throughout the analysis it is clear that much advantage is gained at relatively little cost by the use of a BDI structure for an integrated circuit focal plane.

Journal ArticleDOI
TL;DR: In this paper, the fabrication of IR optical fibers for the 2-to 14-µm region is described, and cylindrical and square fibers fabricated from rods and tubes are discussed.
Abstract: The fabrication of IR optical fibers for the 2- to 14-µm region is described. Both cylindrical and square fibers fabricated from rods and tubes are discussed. The physical properties of the GeSbSe glasses and optical fibers are reviewed. Fabrication of different fiber bundles is also reported. The applications of IR optical fibers and bundles are described, and system performance and parametric analyses are developed for some applications, including thermal imaging, IR sensors, CO2 laser power guide, and low-loss optical fibers.

Journal ArticleDOI
TL;DR: In this paper, it was shown that if a monocentric system existed for which an incident collimated beam emerged as exactly collimated, then the system would give geometrically perfect imaging of any point in space.
Abstract: The general properties of telescopic optical systems consisting of a set of concentric surfaces are discussed. It is shown that if a monocentric system existed for which an incident collimated beam emerged as exactly collimated, then the system would give geometrically perfect imaging of any point in space. It is further shown that a real image of a real object is possible only for monocentric systems containing an odd number of reflecting surfaces. Such perfect collimation is not attainable, but it can be approached, yielding very highly corrected unit-magnification systems. Two such systems, one with a single reflection and one with three, have come into general use for microlithography. Their structure and properties are discussed.

Journal ArticleDOI
TL;DR: In this article, a TV system was developed for detecting and displaying a two-dimensional hologram image that permits concomitant (real-time) hologram interferometry, where a uniform reference field interferes at zero offset angle with a speckled image of an object.
Abstract: A TV system has been developed for detecting and displaying a two-dimensional hologram image that permits concomitant (real-time) hologram interferometry The optics employed are the same as for electronic speckle pattern interferometry (ESPI), wherein a uniform reference field interferes at zero offset angle with a speckled image of an object Rather than detecting spatial modulation to indicate interference, as in ESPI, this system modulates the phase of the reference beam by 120° between picture frames to vary speckle irradiance Each incoming frame is compared with the two previous frames, and only pixels that vary in brightness are passed as white pixels in the video output The use of binary-valued pixels allows inexpensive data processing at standard video rates

Journal ArticleDOI
TL;DR: The self-routing of optical information through a photonic switch using optically processed control is reported and extension of this Technique to a self- routing N x N switch is discussed.
Abstract: The self-routing of optical information through a photonic switch using optically processed control is reported. Routing decisions are made on a bit-by-bit basis. Destination information is encoded in each data bit using optical spread spectrum techniques. Switching of 3.125 Mbits/s data is experimentally demonstrated. Extension of this Technique to a self-routing N x N switch is discussed.

Journal ArticleDOI
TL;DR: In this article, the authors considered the extraction of precise positional information from CCD images of point-source and extended optical targets, and three examples of CCD optical trackers for space-based operation were described.
Abstract: The extraction of precise positional information from CCD images of point-source and extended optical targets is considered, and three examples of CCD optical trackers for space-based operation are described. For ideal point sources, a centerfinding accuracy of 1/100 pixel and a measuremet jitter of less than 1/250 pixel have been obtained using thinned, backside-illuminated devices. Tracker accuracy is shown to be limited by small variation in the optical image shape. Techniques for tracking, and methods for searching the entire field for the desired targets, are also discussed.

Journal ArticleDOI
TL;DR: Turbulence, atmospheric background, and aerosol forward scattering modulation transfer functions (MTFs) are analyzed with regard to both low elevation remotely piloted vehicles and high elevation reconnaissance applications as discussed by the authors.
Abstract: Turbulence, atmospheric background, and aerosol forward scattering modulation transfer functions (MTFs) are analyzed with regard to both low elevation remotely piloted vehicles and high elevation reconnaissance applications. Turbulence is seen to limit image quality only at very high spatial frequencies, where degradation is likely to take place anyway as a result of vibration and diffraction. Background and aerosol MTFs limit low spatial frequency contrast as well. However, this can be overcome somewhat by proper selection of the imaging wavelength and of operation timing. This analysis can aid in sensor selection for system design from the standpoints of both wavelength selection and sensor resolution. Because this analysis includes the effects of weather changes on image propagation through the atmosphere, it also can aid in selecting operation timing on the basis of weather forecasts, with a view toward optimizing expected resolution.

Journal ArticleDOI
TL;DR: In this article, a comparison of backside-illuminated scientifc CCD imagers to an electron flux varying from 1 to 100 pA and beam energy ranging from less than 1 keV up to 20 keV is presented.
Abstract: Recent developments of backside treatment for the backside-illuminated scientifc CCD imagers have shown near-theoretical efficiency even at the short wavelength region of the spectrum. By using SEM performance comparisons of backside-treated and untreated CCDs to an electron flux varying from 1 to 100 pA and beam energy ranging from less than 1 keV up to 20 keV are obtained. The theoretical analysis, the SEM testing procedure, and the quantum efficiency measurement results are presented. It is shown, for example, that the average quantum efficiency increases from less than 1 percent for an untreated CCD to nearly 40 percent for a backside-treated CCD at a beam energy of 1 kev.

Journal ArticleDOI
TL;DR: In this article, a hybrid infrared array using photovoltaic indium antimonide detector material bump-bonded to a silicon substrate that contains the MOS direct readout multiplexer is described, its operation, and preliminary results on quantum efficiency, dark current, noise, linearity, cosmic ray response, and imaging characteristics.
Abstract: A new hybrid infrared array sensitive in the 1 to 5µm spectral region has recently become generally available to the astronomy community. It is a composite (hybrid) array using photovoltaic indium antimonide detector material bump-bonded to a silicon substrate that contains the MOS direct readout multiplexer. This paper describes the array, its operation, and preliminary results on quantum efficiency, dark cur-rent, noise, linearity, cosmic ray response, and imaging characteristics as they apply to ground-based astronomy. The tests were performed on an engineering device since scientific devices are not yet available. Based on our results, we believe that this array and others like it will affect infrared astronomy to an even greater extent than CCDs affected optical astronomy in the mid-1970s.

Journal ArticleDOI
TL;DR: The development of laser glass is reviewed in this paper, where the fluorescence and laser effect of numerous glass compositions have been investigated over the past 20 years, but the industrial applications are few compared to the volume of research: only 20 to 30 glass types are available commercially today.
Abstract: The development of laser glass is reviewed. The fluorescence and laser effect of numerous glass compositions have been investigated over the past 20 years, but the industrial applications are few compared to the volume of research: only 20 to 30 glass types are available commercially today. Phosphate glasses are in the foreground because they exhibit a large laser effect and because it is possible to produce them in large volume and with high damage threshold. They are used in both high power lasers and lasers for machining and measurement.