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Showing papers in "Applied Optics in 1990"


Journal ArticleDOI
TL;DR: It is shown that the POF appears to provide a good compromise between noise tolerance and peak sharpness, with the help of a new family of filters called fractional power filters (FPFs).
Abstract: Several performance criteria are described to enable a fair comparison among the various correlation filter designs: signal-to-noise ratio, peak sharpness, peak location, light efficiency, discriminability, and distortion invariance. The trade-offs resulting between some of these criteria are illustrated with the help of a new family of filters called fractional power filters (FPFs). The classical matched filter, phase-only filter (POF), and inverse filter are special cases of FPFs. Using examples, we show that the POF appears to provide a good compromise between noise tolerance and peak sharpness.

572 citations


Journal ArticleDOI
TL;DR: A correlation microscope based on the Mirau interferometer configuration using a thin silicon nitride film beam splitter is constructed, which predicts accurately both the transverse resolution at a sharp edge and the range resolution for a perfect plane reflector.
Abstract: We have constructed a correlation microscope based on the Mirau interferometer configuration using a thin silicon nitride film beam splitter. This microscope provides the amplitude and phase information for the reflected signal from a sample located on the microscope-object plane. The device is remarkably insensitive to vibrations and is self-correcting for spherical and chromatic range aberrations of the objective. An imaging theory for the correlation microscope has been derived, which predicts accurately both the transverse resolution at a sharp edge and the range resolution for a perfect plane reflector. The range resolution is slightly better than that for a scanning optical microscope using a lens with the same aperture.

491 citations


Journal ArticleDOI
TL;DR: Two interferometric techniques for converting a linearly polarized laser beam into a radially polarized beam with uniform azimuthal intensity are described.
Abstract: Two interferometric techniques for converting a linearly polarized laser beam into a radially polarized beam with uniform azimuthal intensity are described. The techniques are based on the linear combination of orthogonally polarized beams, which have tailored intensity and phase profiles. Linearly polarized beams with intensity profiles tailored using a modified laser or an apodization filter are combined in separate experiments to produce radially polarized light. A beam with an extinction ratio of −21.7 dB and azimuthal intensity variations of less than ±12% is produced using the modified laser output. The second technique uses circularly polarized light and a unique spiral phase delay plate to produce the required phase profile. When focused, a radially polarized beam has a net longitudinal field useful for particle acceleration and, perhaps, other unique applications.

449 citations


Journal ArticleDOI
Byron S. Lee1, Timothy C. Strand1
TL;DR: This approach has two significant implications for profilometry: the longitudinal resolution is decoupled from the lateral resolution, and interference effects can be used to further enhance the longitudinalresolution.
Abstract: Coherence scanning microscopy is a new technique in high resolution imaging. It shares many of the features of confocal microscopy but uses coherence effects to enhance the lateral and longitudinal resolution rather than physical apertures. This approach has two significant implications for profilometry: the longitudinal resolution is decoupled from the lateral resolution, and interference effects can be used to further enhance the longitudinal resolution. We detail the features of coherence scanning profilometry and give some examples.

378 citations



Journal ArticleDOI
TL;DR: Binary phase elements in photoresist have been implemented which transform a uniform beam of light into an array of output light spots by means of the fractional Talbot effect.
Abstract: Binary phase elements in photoresist have been implemented which transform a uniform beam of light into an array of output light spots by means of the fractional Talbot effect. Arrays of more than 30 x 30 light spots with varying spot shapes have been achieved with compression ratios of up to 1:9.

306 citations


Journal ArticleDOI
TL;DR: A 2-D array of 10 x 10 diffractive lenslets was fabricated and tested, and the performance of the lenslets is based on the diffraction of light at a Fresnel zone plate (FZP).
Abstract: A 2-D array of 10 x 10 diffractive lenslets was fabricated and tested Each lenslet has a rectangular aperture and a size of 15 mm x 15 mm The focal length of each lenslet is 47 mm The array was produced by depositing thin films of silicon monoxide on a quartz glass substrate and by using photolithographic techniques The performance of the lenslets is based on the diffraction of light at a Fresnel zone plate (FZP) The FZP pattern was implemented as a phase structure with eight discrete levels The diffraction efficiency was measured to be 91%

212 citations


Journal ArticleDOI
TL;DR: Luminescent organic dye molecules have been incorporated via the solgel method into organically modified silicate (ORMOSIL) polymer host matrices and show improved photostability with respect to comparable polymeric host materials.
Abstract: The solgel process is a solution synthesis technique which provides a low temperature chemical route for the preparation of rigid transparent matrix materials. Luminescent organic dye molecules have been incorporated via the solgel method into organically modified silicate (ORMOSIL) polymer host matrices. Optical gain, laser oscillation, and photostability of rhodamine and coumarin dyes doped into ORMOSIL gels are reported. The gel laser materials exhibit peak gain values of 40 cm−1 and show improved photostability with respect to comparable polymeric host materials.

206 citations


Journal ArticleDOI
TL;DR: It is shown that this equation provides a unified description for incoherent wavefront sensing methods, bringing new insights and opening new prospects in this area.
Abstract: Phase retrieval has recently been experimentally demonstrated, using the irradiance transport equation. We show that this equation provides a unified description for incoherent wavefront sensing methods, bringing new insights and opening new prospects in this area.

192 citations


Journal ArticleDOI
TL;DR: Tunable excimer lasers are used to obtain 2-D images of molecular density distributions inside a cylinder of a modified four-cylinder in-line engine that has optical access to find the laser and fluorescence frequencies needed to measure isolated species.
Abstract: Tunable excimer lasers are used to obtain 2-D images of molecular (and some state-specific) density distributions inside a cylinder of a modified four-cylinder in-line engine that has optical access. Natural fluorescence (i.e., without a laser) is used for some OH pictures, normal laser-induced fluorescence (LIF) for those of NO and of the isooctane fuel, and laser-induced predissociative fluorescence (LIPF) for other OH pictures and for those of O(2). Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species. LIPF works well at high pressures, is state specific, and is ideally suited to follow turbulent processes. No similar measurements in engines have been previously reported. Pictures are taken in succeeding engine cycles. Their sequence is either at a particular point of the engine's cycle to show cyclic fluctuations, or at succeeding portions of the cycle to illustrate the progress of the gasdynamics or of the combustion.

191 citations


Journal ArticleDOI
TL;DR: Brillouin frequency shift in two kinds of jacketed optical single-mode silica fiber, with an ultraviolet curable resin coat and a nylon coat, has been measured at temperatures ranging from -30 to +60 degrees C.
Abstract: Brillouin frequency shift in two kinds of jacketed optical single-mode silica fiber, with an ultraviolet curable resin coat and a nylon coat, has been measured at temperatures ranging from -30 to +60 degrees C. It has been found that there are two reasons for the Brillouin frequency shift change in jacketed optical fibers against temperature change. One is the Brillouin frequency shift change for bare fibers. The other is the thermal stress due to the differences in thermal expansion coefficients in bare fiber and its coating material.

Journal ArticleDOI
TL;DR: Ten different optimization methods, representing both local and global minimum seeking algorithms, were applied to the solution of three different optical thin film design problems, finding the relative efficiencies of the various methods.
Abstract: Ten different optimization methods, representing both local and global minimum seeking algorithms, were applied to the solution of three different optical thin film design problems. Because all methods were incorporated in the same thin film design program, and because a routine was invoked that reads CPU time, the relative efficiencies of the various methods could be compared directly.

Journal ArticleDOI
TL;DR: An optical laser differential interferometer, based on a modified differential interference contrast microscope, has been developed to measure the thermal motion of microscopic protrusions (stereocilia) that are the sites of mechanoelectrical transduction in auditory hair cells, and experimental data were found to be in agreement with theoretical estimates.
Abstract: An optical laser differential interferometer, based on a modified differential interference contrast microscope, has been developed to measure the thermal motion of microscopic protrusions (stereocilia) that are the sites of mechanoelectrical transduction in auditory hair cells. The measurement sensitivity was limited at high frequencies mainly by shot noise, at intermediate frequencies by acoustic interference, and at low frequencies by thermal drift. The power spectral density of the instrumental noise was found to be as low as 1 pm/Hz in the shot noise regime. We could, thus, measure the Brownian motion of hair bundles over the frequency range from 1 Hz–100 kHz. Experimental data that test and demonstrate the sensitivity and spatial discrimination of the instrument were found to be in agreement with theoretical estimates.

Journal ArticleDOI
TL;DR: A parallel distributed processing model with local space-invariant interconnections is proposed, which is more readily implemented by optics and is able to classify patterns correctly, even if they have been shifted or distorted.
Abstract: This paper proposes a parallel distributed processing model with local space-invariant interconnections, which is more readily implemented by optics and is able to classify patterns correctly, even if they have been shifted or distorted. Error backpropagation is used as a training algorithm. Computer simulation results presented indicate that the processing is effective and the network can deal with the shifted or distorted patterns. Moreover, the optical implementation architecture using matched filters for the model is discussed.

Journal ArticleDOI
TL;DR: The use of the rate of change of the relative phase shift of p- and s-polarized light with voltage to determine the electrooptic coefficient of a poled polymer film is discussed.
Abstract: The use of the rate of change of the relative phase shift of p- and s-polarized light with voltage to determine the electrooptic coefficient of a poled polymer film is discussed.

Journal ArticleDOI
TL;DR: NOAA's fieldable injection-seeded, pulsed, coherent CO(2) lidar was developed over a 5-yr period and its performance and reliability are characterized.
Abstract: NOAA's fieldable injection-seeded, pulsed, coherent CO(2) lidar was developed over a 5-yr period. Its performance and reliability are characterized. Techniques for calibration, alignment, collimation, and for improving detector performance and frequency stability are presented.

Journal ArticleDOI
TL;DR: The influence of Raman scattering, based on predictions of a modified two-stream model, is in agreement with measured values of spectral reflectance R( lambda,z) and the spectral diffuse attenuation coefficient for irradiance K(lambda,z).
Abstract: Inelastic (transpectral) scattering may contribute significantly to the in-water light field. Major mechanisms for inelastic scattering include Raman scattering, which is important in clear ocean waters, and fluorescence from a variety of sources, which may be important in more turbid waters. The Raman cross section for liquid water is found to be 8.2 x 10 to the -30th sq cm/sr molecule, which is in agreement with the lower range of published values. Inelastic scattering has important ramifications for several aspects of marine biooptics, including the determination of in-water spectral absorption, the estimation of clear-water ocean optical properties, and possibly various aspects of algal photobiology.

Journal ArticleDOI
TL;DR: An optical volume memory based on the two-photon effect which allows for high density and parallel access and has the advantages of having high capacity and throughput which may overcome the disadvantages of current memories.
Abstract: The advent of optoelectronic computers and highly parallel electronic processors has brought about a need for storage systems with enormous memory capacity and memory bandwidth. These demands cannot be met with current memory technologies (i.e., semiconductor, magnetic, or optical disk) without having the memory system completely dominate the processors in terms of the overall cost, power consumption, volume, and weight. As a solution, we propose an optical volume memory based on the two-photon effect which allows for high density and parallel access. In addition, the two-photon 3-D memory system has the advantages of having high capacity and throughput which may overcome the disadvantages of current memories.

Journal ArticleDOI
TL;DR: The experimental results showed that the maximum of the energy distribution is asymetrically positioned relative to the center and closer to the internal wall at a smaller bending radius than was predicted in the previous theoretical calculation.
Abstract: Plastic hollow fibers were made from plastic tubes covered on the internal wall with a metal layer (a-type) or a metal layer and dielectric layer on top of it (b-type). The CO(2) laser energy transmission through the hollow fiber was measured as a function of the radius of curvature and the coupling lens (focal length at a constant fiber length). The yield of the transmission decreased in subtle curvatures (radius of curvature up to 100 cm) and remained almost constant as the curvature became sharper (down to radius of curvature of 13 cm). For the a-type fibers, the characteristics of attenuation depended on the focal length of the coupling lenses. The energy distribution at the output was measured and mapped. The experimental results showed that the maximum of the energy distribution is asymetrically positioned relative to the center and closer to the internal wall at a smaller bending radius. This was predicted in our previous theoretical calculation. The value of transmitted power attenuation was up to 1.4 dB/m. Maximum power at the output was 30 W, for a fiber of 50-cm length and a cross-sectional diameter of 1.9 mm. These types of hollow fiber have already been used in surgical experiments on dogs.

Journal ArticleDOI
TL;DR: A simplified mathematical model for the far field of a monomode diode laser is employed for easy but fairly accurate computations of the optical field in the focal region and the results of computations are shown to agree well with the measurements.
Abstract: A simplified mathematical model for the far field of a monomode diode laser is employed for easy but fairly accurate computations of the optical field in the focal region. The present treatment is concerned with laser junctions significantly narrower than the wavelength. The field distribution in the plane perpendicular to the diode junction is considered in detail. The results of computations are shown to agree well with the measurements. Hence, the computational code is valuable for the designing of optical devices, such as diode-fiber couplings and laser Doppler anemometers. The present work is not concerned with design calculations for specific applications. Instead, it is intended to illustrate the general features of the proposed mathematical model of monomode diode laser beams.

Journal ArticleDOI
TL;DR: Two configurations of a scanning near field optical microscope working in reflection worked in reflection and results exhibiting nanometric resolution are given and discussed.
Abstract: Two configurations of a scanning near field optical microscope working in reflection are presented. Results exhibiting nanometric resolution are given and discussed.

Journal ArticleDOI
TL;DR: Rayleigh optical depth values obtained from various computations, tabulations, and parameterizations are not always in good agreement and important differences can arise depending on the choice of depolarization factor, the formula used for the refractive index of air, and the choices of columnar and molecular number densities.
Abstract: Rayleigh optical depth values obtained from various computations, tabulations, and parameterizations are not always in good agreement. Important differences as large as 3 or 4% can arise depending on the choice of depolarization factor, the formula used for the refractive index of air, and the choice of standard values for columnar and molecular number densities. The fitting equations generally give rise to the largest differences. The use of different standard altitude profiles for atmospheric pressure and temperature causes a variation of 1% or less in Rayleigh optical depth.

Journal ArticleDOI
TL;DR: A two-spherical mirror multipass cell which allows efficient coupling of a laser beam to a collimated molecular beam at the center of the cell is reported, and an approximately parabolic pattern of reflections is observed on each mirror.
Abstract: We report a two-spherical mirror multipass cell which allows efficient coupling of a laser beam to a collimated molecular beam at the center of the cell. With near-concentric alignment and the laser beam coupled into and out of the cell at the edges of opposite mirrors, an approximately parabolic pattern of reflections is observed on each mirror. Aligned for forty to fifty passes, the cell is used for direct absorption spectroscopy of jet-cooled acetylene, propyne, and 1-butyne in the 3-μm region. Sub-Doppler linewidths as narrow as 12 MHz have been recorded.

Journal ArticleDOI
TL;DR: The algorithm given here offers a useful tool in understanding the mechanism of light absorption in various spectroscopic methods, and is convenient to use where intensity of the IR spectrum is of interest.
Abstract: A new algorithm has been proposed for the calculation of the electric field intensity in stratified multilayered films when light is incident on the system. The algorithm utilizes matrix formulas based on Abeles’s formulas for the calculation of reflectance and transmittance. Equations for calculating patial absorptance due to a certain depth in the films are also derived. Some examples of the application of the electric field description are given for the analysis of three kinds of reflection spectroscopic methods which use metal surfaces: reflection–absorption, surface electromagnetic wave, and metal overlayer ATR methods. The algorithm given here offers a useful tool in understanding the mechanism of light absorption in various spectroscopic methods, and is convenient to use where intensity of the IR spectrum is of interest.

Journal ArticleDOI
TL;DR: A novel amplitude-modulated phase-only filter (AMPOF) is proposed for achieving improved correlation discrimination and is found to have significantly superior correlation discrimination capability.
Abstract: A novel amplitude-modulated phase-only filter (AMPOF) is proposed for achieving improved correlation discrimination The proposed AMPOF has an amplitude spectrum which is the inverse of a biased amplitude spectrum of the object function and a phase spectrum which is a complex conjugate of the phase spectrum of the object function When compared with the phase-only filters, the AMPOF is found to have significantly superior correlation discrimination capability

Journal ArticleDOI
TL;DR: A fast technique for automatic 3-D shape measurement that can automatically and accurately obtain the phase map or the height information of a measured object at every pixel point without assigning fringe orders and interpreting data in the regions between the fringe orders is proposed and verified by experiments.
Abstract: A fast technique for automatic 3-D shape measurement is proposed and verified by experiments. The technique, based on the principle of phase measurement of the deformed grating pattern which carries the 3-D information of the measured object, can automatically and accurately obtain the phase map or the height information of a measured object at every pixel point without assigning fringe orders and interpreting data in the regions between the fringe orders. Only one image pattern is sufficient for obtaining the phase map. In contrast to the fast Fourier transform based technique, the technique processes a fringe pattern in the real-signal domain instead of the frequency domain by using demodulation and convolution techniques, can process an arbitrary number of pixel points, and is much faster. Theoretical analysis, simulation results, and experimental results are presented.

Journal ArticleDOI
TL;DR: Airborne fluorosensor measurements over maritime oil spills show that this method enables a sensitive classification and quantification of surface films having a thickness in the 1-microm range, however, significant changes of the optical signature of oil occur in the presence of submicrometer films which are not yet fully understood.
Abstract: Airborne fluorosensor measurements over maritime oil spills show that this method enables a sensitive classification and quantification of surface films having a thickness in the 1-microm range. However, significant changes of the optical signature of oil occur in the presence of submicrometer films which are not yet fully understood. Possible reasons for this effect are discussed and the limitations of laser fluorosensing of small oil discharges are outlined.

Journal ArticleDOI
TL;DR: A numerically stable and accurate algorithm for computation of the internal radiative properties, as well as the overall scattering and extinction of a stratified sphere having an arbitrary number of layers is developed.
Abstract: Series expressions for the radially dependent absorption cross section and angle-averaged absorption heat source function within a stratified sphere are presented A numerically stable and accurate algorithm for computation of the internal radiative properties, as well as the overall scattering and extinction of a stratified sphere having an arbitrary number of layers is developed The results allow for direct estimation of the degree of penetration and intensity of radiative heating in radially inhomogeneous spherical particles, and also provide an estimate of the thermal emission coefficient of particles having a radial temperature distribution

Journal ArticleDOI
TL;DR: A surface plasmon based chemooptical sensor has been optimized by the use of computer simulation programs and calculated and experimentally measured performances are in good agreement, showing the value of the simulation tool.
Abstract: A surface plasmon based chemooptical sensor has been optimized by the use of computer simulation programs. Calculated and experimentally measured performances are in good agreement, showing the value of the simulation tool.

Journal ArticleDOI
TL;DR: The effect of the grating period and relief depth on the phase retardation and on the rotation of the polarization of the transmitted light is studied.
Abstract: Quarterwave plates can be made as holographic gratings in positive photoresist. We studied the effect of the grating period and relief depth on the phase retardation and on the rotation of the polarization of the transmitted light. Experiments were performed with gratings of different periods, which also exhibit an antireflection property.