Optical Engineering

Published by Society of Photo-optical Instrumentation Engineers
Online ISSN: 0091-3286
Publications
Article
Acoustically-induced vibrations of the Tympanic Membrane (TM) play a primary role in the hearing process, in that these motions are the initial mechanical response of the ear to airborne sound. Characterization of the shape and 3D displacement patterns of the TM is a crucial step to a better understanding of the complicated mechanics of sound reception by the ear. In this paper, shape and sound-induced 3D displacements of the TM in cadaveric chinchillas are measured by a lensless Dual-Wavelength Digital Holography system (DWDHS). The DWDHS consists of Laser Delivery (LD), Optical Head (OH), and Computing Platform (CP) subsystems. Shape measurements are performed in double-exposure mode and with the use of two wavelengths of a tunable laser while nanometer-scale displacements are measured along a single sensitivity direction and with a constant wavelength. In order to extract the three principal components of displacement in full-field-of-view, and taking into consideration the anatomical dimensions of the TM, we combine principles of thin-shell theory together with both, displacement measurements along the single sensitivity vector and TM surface shape. To computationally test this approach, Finite Element Methods (FEM) are applied to the study of artificial geometries.
 
Article
The snapshot advantage is a large increase in light collection efficiency available to high-dimensional measurement systems that avoid filtering and scanning. After discussing this advantage in the context of imaging spectrometry, where the greatest effort towards developing snapshot systems has been made, we describe the types of measurements where it is applicable. We then generalize it to the larger context of high-dimensional measurements, where the advantage increases geometrically with measurement dimensionality.
 
Article
Prism distortions and spurious reflections are not usually considered when prescribing prisms to compensate for visual field loss due to homonymous hemianopia. Distortions and reflections in the high power Fresnel prisms used in peripheral prism placement can be considerable, and the simplifying assumption that prism deflection power is independent of angle of incidence into the prisms results in substantial errors. We analyze the effects of high prism power and incidence angle on the field expansion, size of the apical scotomas, and image compression/expansion. We analyze and illustrate the effects of reflections within the Fresnel prisms, primarily due to reflections at the bases, and secondarily due to surface reflections. The strength and location of these effects differs materially depending on whether the serrated prismatic surface is placed toward or away from the eye, and this affects the contribution of the reflections to visual confusion, diplopia, false alarms, and loss of contrast. We conclude with suggestions for controlling and mitigating these effects in clinical practice.
 
The plot displays the output power density on a logarithmic scale: The black line is for the signal measured in the normal configuration, and the gray line is for the solid-immersion-lens configuration. 
Optical absorbance measurement of the optically tagged BSA protein using the single-mode IOW spectrometer (dark line) compared with the absorbance spectrum obtained by a standard UV-visible spectrophotometer (gray line). 
Time evolution of the surface coverage of the protein BSA being adsorbed on the Al 2 O 3 waveguide surface. 
scheme B 
Article
We report a technique to substantially boost the spectral bandwidth of a conventional waveguide grating coupler by using a solid immersion cylindrical lens at the aplanatic condition to create a highly anamorphic beam and reach a much larger numerical aperture, thus enhancing the spectral bandwidth of a free-space propagating optical beam coupled into a single-mode planar integrated optical waveguide (IOW). Our experimental results show that the broadband IOW spectrometer thus created almost doubles (94% enhancement) the coupled spectral bandwidth of a conventional configuration. To exemplify the benefits made possible by the developed approach, we applied the technique to the broadband spectroscopic characterization of a protein submonolayer; our experimental data confirm the enhanced spectral bandwidth (around 380–nm) and illustrate the potentials of the developed technology. Besides the enhanced bandwidth, the broadband coupler of the single-mode IOW spectrometer described here is more robust and user-friendly than those previously reported in the literature and is expected to have an important impact on spectroscopic studies of surface-adsorbed molecular layers and surface phenomena.
 
Article
Two lens arrays of 20 lenses (4×5) are fabricated in polystyrene (Rexolite 1422) using a 3-D, three-axis micromilling process. The lenses of one array are concave (R(curv) = -2 mm) and the lenses of the other array are convex (R(curv) = 2 mm). A method for correcting a 3-D micromilling program for a single lens is described and evaluated. The lens separation is 4 mm and Ø(diam) = 2.6 mm for all lenses. Based on a measurement of key optical parameters (radius error, wavefront error, and surface roughness), micromilled lenses are shown to be of high optical quality compared with the form error and surface roughness obtained with plastic injection molded lenses.
 
Article
The increasing prevalence of obesity suggests a need to develop a convenient, reliable, and economical tool for assessment of this condition. Three-dimensional (3-D) body surface imaging has emerged as an exciting technology for the estimation of body composition. We present a new 3-D body imaging system, which is designed for enhanced portability, affordability, and functionality. In this system, stereo vision technology is used to satisfy the requirement for a simple hardware setup and fast image acquisition. The portability of the system is created via a two-stand configuration, and the accuracy of body volume measurements is improved by customizing stereo matching and surface reconstruction algorithms that target specific problems in 3-D body imaging. Body measurement functions dedicated to body composition assessment also are developed. The overall performance of the system is evaluated in human subjects by comparison to other conventional anthropometric methods, as well as air displacement plethysmography, for body fat assessment.
 
Article
The optical cryptosystem based on phase-shifting interferometry (PSI) is one of the most interesting optical cryptographic schemes in recent years. However, we find that the PSI technique provides an attractive method to record the ciphertext, but contributes little to the security level of the cryptosystem. From the cryptanalysis point of view, in a certain simplified case, an attacker is only required to crack two equivalent decryption keys instead of the original random phase keys and geometric key. Moreover, a chosen-plaintext attack method is proposed, in which an impulse function is chosen as a known plaintext. By using this attack, the attacker can effectively recover any plaintext from the corresponding ciphertext. The validity of the attack is verified by computer simulations.
 
Article
In this article, a cone-beam computed tomography scanning mode is designed using four x-ray sources and a spherical sample. The x-ray sources are mounted at the vertices of a regular tetrahedron. On the circumsphere of the tetrahedron, four detection panels are mounted opposite of each vertex. To avoid x-ray interference, the largest half angle of each x-ray cone beam is 27°22', while the radius of the largest ball fully covered by all the cone beams is 0.460, when the radius of the circumsphere is 1. A proposed scanning scheme consists of two rotations about orthogonal axes, such that, each quarter turn provides sufficient data for theoretically exact and stable reconstruction. This design can be used in biomedical or industrial settings, such as when a sequence of reconstructions of an object is desired.
 
Article
Image mapping spectrometry (IMS) is a hyperspectral imaging technique that simultaneously captures spatial and spectral information about an object in real-time. We present a new calibration procedure for the IMS as well as the first detailed evaluation of system performance. We correlate optical components and device calibration to performance metrics such as light throughput, scattered light, distortion, spectral image coregistration, and spatial/spectral resolution. Spectral sensitivity and motion artifacts are also evaluated with a dynamic biological experiment. The presented methodology of evaluation is useful in assessment of a variety of hyperspectral and multi-spectral modalities. Results are important to any potential users/developers of an IMS instrument and to anyone who may wish to compare the IMS to other imaging spectrometers.
 
Numerical bound error Root-Mean-Square-Error in the eikonal reconstruction versus the maximum diameter of the mesh triangles. The slash curve represents the fit of the numerical data to a parabola to compare with predictions from the theory of finite elements.
Experimental decentration error effects, with and without correction, in the RMSE m and normalized RMSE of the eikonal reconstruction for different separation between planes.
͑ a ͒ Simulated Airy disk irradiance distribution in ADU units. ͑ b ͒ Simulated finite difference between two Airy irradiance patterns of two planes separated 0.2 mm. 
Simulated finite difference ͑ ADU units ͒ between two Airy irradiance patterns when CCD quantization effect is considered. The separation between the planes is 0.2 mm. 
͑ a ͒ Simulated noisy irradiance finite difference. ͑ b ͒ Simulated noisy irradiance finite difference after filtering. ͑ c ͒ Experimental irradiance finite difference. ͑ d ͒ Experimental irradiance finite difference after filtering. Note the different in scale ͑ in ADU units ͒ of the four images. The separation between the planes is 0.2 mm. 
Article
Wavefront reconstruction from the transport-of-intensity equation (TIE) is a well-posed inverse problem given smooth signals and appropriate boundary conditions. However, in practice experimental errors lead to an ill-condition problem. A quantitative analysis of the effects of experimental errors is presented in simulations and experimental tests. The relative importance of numerical, misalignment, quantization, and photodetection errors are shown. It is proved that reduction of photodetection noise by wavelet filtering significantly improves the accuracy of wavefront reconstruction from simulated and experimental data.
 
Article
The spatial-spectral holographic imaging system (S(2)-VHIS) is a promising alternative to confocal microscopy due to its capabilities to simultaneously image several sample depths with high resolution. However, the field of view of previously presented S(2)-VHIS prototypes has been restricted to less than 200 mu m. We present experimental results of an improved S(2)-VHIS design that has a field of view of similar to 1 mm while maintaining high resolution and dynamic range. (c) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3378025]
 
Conference Paper
In this paper, the measurement error in a gap larger than 0.3 mm of a quadrilateral hole sample, using the optical non-contact measuring machine, is discussed theoretically and experimentally. By projecting spot image onto the sample's inside wall and detects the reflected image by CCD camera, the position of inside wall of sample can be measured. The inner diameter of the sample can be measured from distance between the positions of each inside walls. Experimental results showed that the measurement error of the gap varies with the gap size of sample. Comparison with theoretical simulation results, it was verified that the spherical aberrations of the lens in the measuring machine is the cause of this error. With the maximum spherical aberration of the lens of 50μm, the maximum measurement error of the gap is +1.0μm for a 0.3 × 0.3 mm square hole, and is -0.30 - -0.35μm for the quadrilateral hole with the gap larger than 0.6 mm. These theoretical results are in good agreement with the experimental results. The measurement error is always negative when the spherical aberration is assumed to be 0.
 
Conference Paper
A fringe-adjusted joint-transform correlator (JTC) based technique for improved color pattern recognition is introduced. In the proposed technique, a real-valued filter, called the fringe-adjusted filter is used to reshape the joint power spectrum in order to yield better correlation output. A color image is processed through three channels, and the fringe-adjusted filtering is applied to each of these channels to obtain excellent correlation discrimination. The correlation outputs from these channels are then fused together to achieve a decision on the detection of a given color pattern. It is also shown that the fringe-adjusted filtering can be applied to a multichannel single-output JTC to obtain excellent correlation output that represents the coherence level between the input target image and the reference image for all color channels. These two techniques can be easily implemented in real time as for practical color pattern recognition applications. Two architectures for all-optical implementation of the proposed techniques are presented
 
Conference Paper
In this paper, we will introduce and analyze techniques for the reduction of aliased power in a staring infrared imaging system. A standard staring system uses a fixed two dimensional detector array which implies a fixed spatial sampling frequency corresponding to the detector to detector spacing. Aliasing will occur when sampling a scene containing spatial frequencies exceeding half of this sampling frequency. Most natural scenes are not band limited and aliasing can significantly degrade the quality and utility of the resulting image. The alias reduction schemes presented here are based upon microscanning, which is an optical technique utilizing subpixel shifts between multiple time frames in an image sequence. These multiple images are used to reconstruct a single frame with reduced aliasing, The microscanning techniques presented here are divided into the categories of controlled and uncontrolled techniques. If the microscanning is controlled, using a microscan mirror or beam steerer for example, one can obtain a uniformly sampled microscanned image. The reconstruction in this case is a relatively simple task. In an uncontrolled case, the sampling may be nonuniform and the reconstruction becomes more complicated. Experimental results are presented which illustrate that the quality of a microscanned image can be dramatically improved over a non-microscanned image as well as demonstrate the utility of the applied algorithms
 
Conference Paper
Total internal reflection holography permits high-resolution, noncontact lithography over very large fields. A production lithographic system has been constructed employing specially developed illumination, focus, and alignment subsystems integrated onto a 6-in. substrate-handling mechanism. The system achieves an imaging resolution of 0.25 mum with a present overlay capability of +/-0.5 mum. A fine alignment system under development has demonstrated a 50-nm measurement accuracy. The technology is well suited to many applications, including the manufacture of flat panel displays, surface acoustic wave devices, integrated optics, and optical storage disks.
 
Conference Paper
Free space optical communication between satellites networked together can make possible high speed communication between different places on Earth. We derive mathematical models of signal, noise, and approximate bit-error-rates of optical communication satellite networks as functions of the system parameters. The optical inter-satellite network model considered includes transmitter satellite, repeater satellites, and receiver satellite all networked together. From the analysis it is clear that even a low vibration amplitude of the satellite pointing systems decreases dramatically the network performance
 
Conference Paper
This paper describes the development of an information-theoretic image measure for sensor evaluation under the contract to the United States Air Force. While current approaches are based on human perception models, a need exists for evaluation of sensors for ATC/ATR systems. Such an evaluation should be performed in terms of the probabilities of detection/identification and false alarms independent of the idiosyncrasies of the specific ATC/ATR algorithms. Such an approach based on the information-theoretic content of images for the target vs. background separability is being developed and applied to evaluating sensors using the Tower Test data collected at the Wright Laboratories
 
Conference Paper
Stereo correspondence could be formulated as an optimization problem. Most of the existing solutions, however, adopt the gradient-based approaches, requiring an initialization close to the correct solution. This paper presents an alternative approach, which is genetic algorithm based, that has larger tolerance toward the quality of the initialization. Each candidate for the three-dimensional description of the imaged scene is encoded as an individual that embraces thousands or even millions of chromosomes, and a population of such individuals are allowed to evolve to reach a globally optimal or near-optimal solution. Our solution framework also includes a coarse-to-fine matching strategy to reduce the matching ambiguity and the computations needed. Experimental results on synthetic and real images are shown to illustrate the performance of the approach.
 
Conference Paper
The calibration of a laser stripe profiler consisting of a laser stripe projector, camera, and linear motion table is considered. A nonlinear system model is used, which accommodates radial distortion in the camera lens. The way in which stripe data is extracted from the camera images leads to a natural formulation of the calibration problem as a nonlinear least squares problem. This can then be solved using standard techniques. The use of this nonlinear model reduces the error in the generated 3-D data by over an order of magnitude.
 
Conference Paper
Ion diffusion of rubidium (Rb) in potassium titanyl phosphate (KTP) creates areas of high Rb concentration. The areas of high Rb concentration have an index of refraction of n(Rb)=1.846 as compared to the index of refraction for the KTP of n(K)=1.842. The small change in the index of refraction is enough to create waveguide structures and integrated optics such as Bragg gratings in the KTP substrate. A tunable external-cavity diode laser is constructed using waveguide structures and integrated optics created by this ion diffusion. The resulting Bragg grating is used to provide optical feedback to control the operating wavelength of an external-cavity laser. Tuning is accomplished using the electro-optic properties of KTP to control the effective period of the Bragg grating. A tuning response of R=19.5 MHz/N was measured. (C) 2003 Society of Photo-Optical Instrumentation Engineers.
 
Conference Paper
We present a generalized random field model in a random environment to classify hyperspectral textures. The model generalizes traditional random field models by allowing the spatial interaction parameters of the field to be random variables. Principal component analysis is used to reduce the dimensionality of the data set to a small number of spectral bands that capture almost all of the energy in the original hyperspectral textures. Using the model we obtain a compact feature vector that efficiently computes within and between band information. Using a set of hyperspectral samples, we evaluate the performance of this model for classifying textures and compare the results with other approaches.
 
Conference Paper
This paper presents the generalized explicit schemes (GES) for the coherence enhancing diffusion (CED) filtering, which is one of a wide variety of nonlinear diffusion filtering. Unlike the traditional standard explicit scheme which updates the diffusion coefficients in each iteration, the generalized ones use several new updating types, including the fixed diffusion coefficients, the uniform interval update (UIU) and the optimized interval update (OIU) of diffusion coefficients. The GES significantly improve efficiency by reducing the computational amount of updating the diffusion coefficients, compared with the existing acceleration methods by enlarging the time step, such as implicit or semi-implicit schemes, or a scheme with larger mask of spatial discretization. Also the OIU may allow the GES to achieve high accuracy by using only two to four updating of the diffusion coefficients during the whole process. Experiments demonstrate the efficiency of the GES is comparable to those existing acceleration methods, meanwhile, the GES with the OIU outperform the other methods in the tradeoff between efficiency and accuracy.
 
Conference Paper
Thresholding color video images is challenging because of the low spatial resolution and the complex backgrounds. This paper investigates the issue of thresholding these images by reducing the number of colors in order to improve automated text detection and recognition. An unsupervised thresholding approach is presented which reduces the background complexity while retaining the important text character pixels. The experiments show that our proposed thresholding approach performs significantly better than simple image histogram-based methods which generally do not produce satisfactory results.
 
Conference Paper
Thresholding color video images is challenging because of the low spatial resolution and the complex backgrounds. This paper investigates the issue of thresholding these images by reducing the number of colors in order to improve automated text detection and recognition. An unsupervised thresholding approach is presented which reduces the background complexity while retaining the important text character pixels. The experiments show that our proposed thresholding approach performs significantly better than simple image histogram-based methods, which generally do not produce satisfactory results.
 
Conference Paper
We present a flexible hybrid decision scheme for decentralized detection under communication constraints. In this scheme, local sensors send a binary (hard) decision to the fusion center when the local sensors have a relatively high confidence in the decision, otherwise a perfect version of the local likelihood ratio (LLR) is sent. In practice, a finely quantized version of the LLR is sent. The degree of confidence at which this switch is made is determined by the specified communication constraint. The fusion center makes a final decision based on the information received from local sensors. By employing the person-by-person optimization methodology, we develop the local decision rules and the fusion rule. Owing to the associated computational difficulty, we propose a simpler procedure based on the class of Ali-Silvey distance measures to obtain the local decision rules. A numerical example is also presented for illustration.
 
Conference Paper
A technique, resulting in the significant reduction of negative effects of satellite jitter on the accuracy of laser beam positioning in communication systems, is presented. It implies application of vibration monitoring instrumentation for estimation of the motion components constituting jitter. A self-tuning feedforward jitter compensation scheme is introduced to the existing mirror positioning control systems. The technique is verified by computer simulation and is in the process of experimental investigation
 
Conference Paper
In this paper, the special design of a Hopfield neural network, called contextual Hopfield neural network (CHNN), is presented for finding the edges of CT and MRI images. Different from conventional 2D Hopfield neural networks, the CHNN maps the 2D Hopfield network at the original image plane. With this direct mapping, the network is capable of incorporating pixel contextual information into a pixel's labeling procedure. As a result, the effect of tiny details or noises will be effectively removed by the CHNN and the drawback of disconnected fractions can be overcome. Furthermore, the problem of satisfying strong constraints can be alleviated and results in a fast converge. Our experimental results show that the CHNN can obtain more appropriate, more continued edge points than Laplacian-based, Marr-Hildreth's, Canny's, and wavelet-based methods
 
Conference Paper
Earth observation missions have recently attracted a growing interest, mainly due to the large number of possible applications capable of exploiting remotely sensed data and images. Along with the increase of market potential, the need arises for the protection of the image products. Such a need is a very crucial one, because the Internet and other public/private networks have become preferred means of data exchange. A critical issue arising when dealing with digital image distribution is copyright protection. Such a problem has been largely addressed by resorting to watermarking technology. A question that obviously arises is whether the requirements imposed by remote sensing imagery are compatible with existing watermarking techniques. On the basis of these motivations, the contribution of this work is twofold: assessment of the requirements imposed by remote sensing applications on watermark-based copyright protection, and modification of two well-established digital watermarking techniques to meet such constraints. More specifically, the concept of near-lossless watermarking is introduced and two possible algorithms matching such a requirement are presented. Experimental results are shown to measure the impact of watermark introduction on a typical remote sensing application, i.e., unsupervised image classification. (C) 2002 Society of Photo-Optical Instrumentation Engineers.
 
Conference Paper
Summary form only given. The efficient generation of sub-picosecond hard-x-ray pulses in the keV energy range is of great scientific and practical importance. A promising indirect way to generate ultrashort hard-x-rays is to use low-intensity femtosecond laser pulses, These pulses induce photoemission of electrons from a metal cathode which then are accelerated towards a high-Z target material by applying an external high voltage. Hard-x-rays are produced via Bremsstrahlung of energetic electrons.We report on our progress in the development and investigations of a femtosecond laser-driven x-ray tube
 
Conference Paper
Two-photon absorption of photosensitive media can produce interference fringes with double spatial frequency. This requires the employment of multiple-frequency beams, which interfere with one another to produce a stationary image with double spatial resolution. The required beams were produced by frequency filtering of broadband radiation from a cw mode-locked femtosecond Ti:sapphire laser (λ = 790 nm) in a dispersion-free pulse shaper. Then the two multifrequency rays converged from opposite edges of a lens, focusing on Kodak commercial film. The laser intensity was high enough to produce a two-photon exposure. The doubling of the spatial frequency of the interference pattern has been observed, but the contrast ratio of the pattern was limited by competition from the more usual one-photon absorption. Laser pulse parameters for a single-pulse two-photon exposure have been estimated.
 
Architecture of the fusion system.
Figure 1. Architecture of the fusion system.  
Conference Paper
In a system of N sensors, the sensor S<sub>j</sub>, j=1,2...,N, outputs Y<sup>j∈</sup>[0, 1], according to an unknown probability density p<sub>j</sub>(Y<sup>j|</sup>X), corresponding to input X∈[0, 1]. A training n-sample (X<sub>1</sub>,Y<sub>1</sub>), (X<sub>2</sub>,Y<sub>2</sub>), ..., (X<sub>n</sub>,Y<sub>n</sub>) is given where Y<sub>i</sub>=(Y<sub>i</sub><sup>1,</sup>Y<sub>i</sub><sup>2,</sup>...,Y <sub>i</sub><sup>N</sup>) such that Y<sub>i</sub><sup>j </sup>is the output of S<sub>j</sub> in response to input X<sub>i</sub>. The problem is to estimate a fusion rule f:[0,1]<sup>N</sup>→[0,1], based on the sample, such that the expected square error, I(f), is minimized over a family of functions &Fscr; with uniformly bounded modulus of smoothness. Let f* minimize I(.) over &Fscr;; f* cannot be computed since the underlying densities are unknown. We estimate the sample size sufficient to ensure that Nadaraya-Watson estimator fˆ satisfies P[I(fˆ)-I(f*)>ε]<δ for ε>0 and δ, 0<δ<1. We apply this method to the problem of detecting a door by a mobile robot equipped with arrays of ultrasonic and infrared sensors
 
Conference Paper
In recent years, with the advent of femtosecond pulse technology, two-photon absorption has commenced to be used for exposing photo-resists. It is natural to ask then, what is the spatial resolution of two-photon lithography? There has already been some discussion of resolution limits in two-photon, scanning confocal fluorescence microscopy. We will find that ordinary two-photon exposure of photo-resist merely enhances the photographic contrast, or gamma. While this improves the spatial resolution somewhat, it does so at the expense of a requirement for tighter control over the incident light intensity. Instead, we introduce a new type of exposure system employing a multiplicity of 2-photon excitation frequencies which interfere with one another to produce a super-resolution stationary image, exhibiting a true doubling of the spatial resolution
 
Conference Paper
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Conference Paper
In hyperspectral imaging applications, the detection performance of the matched filter is typically evaluated or predicted based on Gaussian (or normal) probability density models. However, it is well known that hyperspectral imaging data exhibit nonGaussian behavior. In this paper, we propose modeling the distribution of hyperspectral backgrounds using a more accurate model based on the elliptically contoured multivariate t-distributions. Then, using a Gaussian distribution model for the target class and an elliptical t-distribution for the background class, we show that detection performance predictions based on solely Gaussian models can be inaccurate and overly optimistic. Therefore, conclusions based on such models should be used with extreme care.
 
Conference Paper
No one algorithm is felt to be appropriate for detection. Thus to achieve this, first and most important, and most computationally intensive operation in image processing, we consider the use of several detection algorithms and fusion of their outputs to reduce false alarms PFA while retaining high detection rates P<sub>D</sub>. The detection algorithms must be shift-invariant, since multiple objects can be present and since object location is not known. Thus, correlation filters are attractive (they are shift-invariant and provide processing gain)
 
Conference Paper
The Hough transform has been suggested in literature as an effective technique for track initiation. However, most literature to date has focused on simplistic applications of this technique based on one sensor, one target, and no clutter scenarios. This paper presents a detailed methodology applying the Hough transform to the multiple target, multiple sensor data association and track initiation problem. Using a two tiered methodology, bearing and range tracks are detected in separate Hough spaces. The measurements defining these tracks are subsequently associated for the purpose of track detection and initiation. The effectiveness of this technique is demonstrated through several comprehensive simulation scenarios
 
Conference Paper
In order to enable optical systems to operate with a high degree of compactness and reliability it is necessary to combine large number of optical functions in small monolithic structures. A development, somewhat reminiscent of that that took place in Integrated Electronics, is now beginning to take place in optics. The initial challenge in this emerging field, known appropriately as "Integrated Optics", is to demonstrate the possibility of performing basic optical functions such as light generation, coupling, modulation, and guiding in Integrated Optical configurations. The talk will review the main theoretical and experimental developments to date in Integrated Optics. Specific topics to be discussed include: Material considerations, guiding mechanisms, modulation, coupling and mode losses. The fabrication and applications of periodic thin film structures will be discussed.
 
Article
An electrooptical characterization encompassing linearity, blooming, dark-count rate, charge-transfer efficiency (CTE), and quantum efficiency, is presented for a front/side-illuminated CCD with 512x512 format and 27x27-micron pixels. The detailed noise characteristics of the CCD-output FET are reported. While very good low light level CTE is obtained in the parallel-shift direction, CTE problems arise in the serial direction. The output FET noise is equivalent to 5-12 electrons, depending on FET operating conditions and system bandwidth.
 
Article
A pulsed infrared lidar system designed for application to the remote sensing of atmospheric trace gases from an airborne platform is described. The system is also capable of measuring the infrared backscatter characteristics of the ocean surface, terrain, cloud, and aerosol targets. The lidar employed is based on dual wavelength pulse energy measurements in the 9-11 micrometer wavelength region.
 
Article
The Center for Astrophysics-University of Arizona balloon-borne, inertially-guided, 102 cm telescope was designed to perform photometry and high resolution mapping of far-infrared (40-250 micron) celestial sources. To date the telescope has now been flown and successfully recovered a total of ten times. Six of the flights have produced useful astronomical data, resulting in more than 40 hours of observations of numerous objects, such as HII regions, dark clouds, molecular clouds, galaxies, the galactic center, planets, and an asteroid. Maps with a resolution of 1 arcmin FWHM have been achieved with absolute position accuracies of plus or minus 10 arcsec. The rms noise equivalent flux density of the system is approximately 70 Jy/(Hz) to the 1/2. From the launch site in Texas, sources as far south as - 50 degrees declination have been observed.
 
Article
A polarization photometer has been developed for rapidly determining the bidirectional, polarized, and diffuse light-scattering properties of individual leavs illuminated and measured 'in vivo' at an angle of 55 deg (approximately Brewster's angle) in six wavelength bands in the visible and near-IR wavelength regions. The optical performance and data quality of the system are evaluated to estimate the magnitude of the variation in the data attributable to the instrument system and to measurement procedures. The potential to discriminate between three species of oak is demonstrated using data acquired by the polarization photometer. The instrument is being used to increase understanding of the radiation transfer process in plant canopies and specifically to determine how agronomic information of the physical and chemical processes in leaves, plants, and plant canopies is expressed in these light-scattering properties.
 
Article
The design and performance of a multispectral scanner are described. The optical system of Skylab Multispectral Scanner (S-192) consists of an image plane scanner (telescope), a spectrometer for separation of the radiation into 13 spectra bands, and a 13-element (Hg,Cd)Te detector array. The image plane scanner is a new system based on three interrelated main features: (1) a reflective adaptation of the Schmidt principle; (2) a conical line scan in which all field elements are brought to and corrected on axis; and (3) a scanning arrangement in which the aperture stop of the system, located in a relay unit, is imaged at the center of curvature of the spherical primary mirror. Replacing the physical stop used in the classical Schmidt configuration with a virtual one makes te system much more compact. As a consequence of the image plane scanning and the Schmidt symmetry, the system scans at a large radial angle (11-degree diameter) and at a high rate (6000 rpm) with relatively small scanning mirrors and a large entrance pupil diameter (43 cm). The spectrometer divides the radiation into 13 spectral bands, 12 of which are located between 0. 4 and 2. 35 micrometers and the other, 10. 2-12. 5 micrometers. A dichroic beamspli separates the far IR band from the 12 lower wavelength bands, which are dispersed byprisms. Photographic reproductions of the actual flight recordings show 80-meter resolution at an altitude of 440 km.
 
Article
The history and background of the Large Deployable Reflector (LDR) are reviewed. The results of the June 1982 Asilomar (CA) workshop are incorporated into the LDR science objectives and telescope concept. The areas where the LDR may have the greatest scientific impact are in the study of star formation and planetary systems in the own and nearby galaxies and in cosmological studies of the structure and evolution of the early universe. The observational requirements for these and other scientific studies give rise to a set of telescope functional requirements. These, in turn, are satisfied by an LDR configuration which is a Cassegrain design with a 20 m diameter, actively controlled, segmented, primary reflector, diffraction limited at a wavelength of 30 to 50 microns. Technical challenges in the LDR development include construction of high tolerance mirror segments, surface figure measurement, figure control, vibration control, pointing, cryogenics, and coherent detectors. Project status and future plans for the LDR are discussed.
 
Article
This paper presents an updated version of a previous paper describing a three-phase 800 x 800 charge-coupled-device image sensor. Although this device was originally designed to be used as the sensor for the Wide Field/Planetary Camera on the Hubble Space Telescope, it is now being used as the detector of choice on many ground-based telescopes. The performance of the device is reviewed, and the important contributions it has made to the understanding of general CCD performance is indicated.
 
Article
We propose the segmented Large Millimeter Telescope (LMT/GTM),as the largest spatial light modulator capable of producing vortex beams of integer topological charge. This observing mode could be applied for direct exoplanet searches in the millimeter or submillimeter regimes. We studied the stability of the vortex structure against aberrations and diffraction effects inherent to the size and segmented nature of the collector mirror. In the presence of low order aberrations the focal distribution of the system remains stable. Our results show that these effects depend on the topological charge of the vortex and the relative orientation of the aberration with respect to the antenna axis. Coma and defocus show no large effects in the image at the focal plane, nevertheless the system is very sensitive to astigmatism. Heat turbulence, simulated by random aberrations, shows that the system behaves in a similar way as astigmatism dissociating the vortices. We propose the Segmented Vortex Telescope as a novel approach for the detection of giant planets outside circumstellar disks around nearby stars. Since our results are applicable to other facilities with segmented surfaces, we suggest that this idea should be considered as a regular observation mode complementary to interferometric methods.
 
Article
An optical design and polarization analysis of the Air Force/NASA Solar Activity Measurements Experiments solar vector magnetograph optical system is performed. Polarization aberration theory demonstrates that conventional telescope coating designs introduce unacceptably high levels of polarization aberrations into the optical system. Several ultralow polarization mirror and lens coatings designs for this instrument are discussed. Balancing of polarization aberrations at different surfaces is demonstrated.
 
Article
A technique to measure the size and velocity of particles is discussed, and results are presented. In this technique two small laser beams of one color identify the center of a laser beam of a different color. This defines a region of almost uniform intensity where the light scattered by the individual particles can be related to their sizes. A variation of this technique that uses two polarizations of the same color of laser beam is also presented. Results are presented for monodisperse, bimodal, trimodal, and polydisperse sprays produced by the Berglund-Liu droplet generator and a pressure nozzle. Size distributions obtained at three different ranges for the same spray show excellent self-consistency in the overlapping regions. Measurements of a spray of known characteristics exhibit errors in the order of 10 percent.
 
Article
A lidar facility has been established at the Jet Propulsion Laboratory-Table Mountain Facility located at an altitude of 2300 m in the San Gabriel Mountains in Southern California. This facility is using the technique of differential absorption lidar to measure atmospheric ozone concentration profiles. Two separate systems are needed to obtain the profile from the ground up to an altitude of 45 to 50 km. An Nd:YAG-based system is described for measurements from the ground up to 15 to 20 km altitude, and an excimer-laser-based system for measurements from 15 km to 45 to 50 km altitude. The systems were designed to make high-precision, long-term measurements to aid in the detection of changes in the atmospheric ozone abundance through participation in the Network of Detection of Stratospheric Change.
 
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Range-resolved water vapor measurements using the differential-absorption lidar (DIAL) technique is described in detail. The system uses two independently tunable optically pumped lasers operating in the near infrared with laser pulses of less than 100 microseconds separation, to minimize concentration errors caused by atmospheric scattering. Water vapor concentration profiles are calculated for each measurement by a minicomputer, in real time. The work is needed in the study of atmospheric motion and thermodynamics as well as in forestry and agriculture problems.
 
Top-cited authors
Robert J. Woodham
  • University of British Columbia - Vancouver
L.A. Coldren
  • University of California, Santa Barbara
Wally Peters
  • University of South Carolina
Song Zhang
  • Chang'an University
Larry Andrews
  • University of Central Florida