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Showing papers in "Applied Optics in 1983"


Journal ArticleDOI
TL;DR: The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model and it is shown that -epsilon1(omegas) = epsilon2(omega) approximately omega(2)(p)/(2omega( 2)(tau) at the damping frequency omega = omega(tau), where the plasma frequency is omega(p).
Abstract: Infrared optical constants collected from the literature are tabulated. The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model. It is shown that -epsilon1(omega) = epsilon2(omega) approximately omega(2)(p)/(2omega(2)(tau)) at the damping frequency omega = omega(tau). Also -epsilon1(omega(tau)) approximately - (1/2) epsilon1(0), where the plasma frequency is omega(p).

2,014 citations


Journal ArticleDOI
TL;DR: A new computer-based technique for automatic 3-D shape measurement is proposed and verified by experiments that has a much higher sensitivity than the conventional moire technique and is capable of fully automatic distinction between a depression and an elevation on the object surface.
Abstract: A new computer-based technique for automatic 3-D shape measurement is proposed and verified by experiments. In contrast to the moire contouring technique, a grating pattern projected onto the object surface is Fourier-transformed and processed in its spatial frequency domain as well as in its space-signal domain. This technique has a much higher sensitivity than the conventional moire technique and is capable of fully automatic distinction between a depression and an elevation on the object surface. There is no requirement for assigning fringe orders and interpolating data in the regions between contour fringes. The technique is free from errors caused by spurious moire fringes generated by the higher harmonic components of the grating pattern.

1,863 citations


Journal ArticleDOI
TL;DR: To study the occurrence of wave-front irregularities caused by dust particles a model has been developed and countermeasures derived which assure sufficient regularity of contour line plots, and the repeatability of the present experimental setup was better than λ/200 within the 3σ limits.
Abstract: Digital wave-front measuring interferometry is a well-established technique but only few investigations of systematic error sources have been carried out so far. In this work three especially serious error sources are discussed in some detail: inaccuracies of the reference phase values needed for this type of evaluation technique; disturbances due to extraneous fringes; and spatially high frequency noise on the wave fronts caused by dust particles, inhomogeneities, etc. For the first two error sources formulas of the resulting phase deviation are derived and compensation possibilities discussed and experimentally verified. To study the occurrence of wave-front irregularities caused by dust particles a model has been developed and countermeasures derived which assure sufficient regularity of contour line plots. The repeatability of the present experimental setup was better than λ/200 within the 3σ limits.

792 citations


Journal ArticleDOI
TL;DR: The processing algorithms used for relating the apparent color of the ocean observed with the Coastal-Zone Color Scanner on Nimbus-7 to the concentration of phytoplankton pigments are developed and discussed in detail and suggest the error in the retrieved pigment concentration is of the order of 30-40% for a variety of atmospheric turbidities.
Abstract: The processing algorithms used for relating the apparent color of the ocean observed with the Coastal-Zone Color Scanner on Nimbus-7 to the concentration of phytoplankton pigments (principally the pigment responsible for photosynthesis, chlorophyll-a) are developed and discussed in detail. These algorithms are applied to the shelf and slope waters of the Middle Atlantic Bight and also to Sargasso Sea waters. In all, four images are examined, and the resulting pigment concentrations are compared to continuous measurements made along ship tracks. The results suggest that over the 0.08-1.5 mg/cu m range, the error in the retrieved pigment concentration is of the order of 30-40% for a variety of atmospheric turbidities. In three direct comparisons between ship-measured and satellite-retrieved values of the water-leaving radiance, the atmospheric correction algorithm retrieved the water-leaving radiance with an average error of about 10%. This atmospheric correction algorithm does not require any surface measurements for its application.

764 citations


Journal ArticleDOI
TL;DR: The theory of speckle masking is presented; it makes use of triple correlations and their Fourier counterparts, the bispectra, and shows algorithms for the recovery of the object from genuine astronomical Bispectra data.
Abstract: Due to the turbulent atmosphere the resolution of conventional astrophotography is limited to ∼1 sec of arc. However, the speckle-masking method can yield diffraction-limited resolution, i.e., 0.03 sec of arc with a 3.6-m telescope. Speckle masking yields true images of general astronomical objects. No point source is required in the isoplanatic field of the object. We present the theory of speckle masking; it makes use of triple correlations and their Fourier counterparts, the bispectra. We show algorithms for the recovery of the object from genuine astronomical bispectra data.

610 citations


Journal ArticleDOI
TL;DR: Comparison of the results indicates the range of values of the scattering and absorption parameters where the computationally fast diffusion approach is applicable.
Abstract: To allow the determination of scattering and absorption parameters of a turbid material from reflection measurements the relation of these parameters to the reflection has been described by two theoretical approaches. One approach is based on the diffusion theory which has been extended to include anisotropic scattering. This results in a reflection formula in which the scattering and absorption are described by one parameter each. As a second more general approach a Monte Carlo model is applied. Comparison of the results indicates the range of values of the scattering and absorption parameters where the computationally fast diffusion approach is applicable.

498 citations


Journal ArticleDOI
TL;DR: The measured data and knowledge of the mechanics of the observed dynamics of the data can provide rigorous validation and verification tests for theoretical radiative transfer models, especially in interpreting aircraft and satellite data, where the scan angle varies widely and can have different orientations with respect to the sun.
Abstract: Directional reflectance factors that span the entire exitance hemisphere are collected on the ground for a variety of homogeneous vegetation canopies and bare soils. NOAA 6/7 AVHRR bands 1 (0.58-0.68 micron) and 2 (0.73-1.1 microns) are used. When possible, geometric measurements of leaf orientation distributions are taken simultaneously with each spectral measurement. Other supporting structural and optical measurements are made. These data sets are taken at various times of the day for each cover type. These unique sets, together with pertinent data in the literature, are used to investigate the dynamics of the directional reflectance factor distribution as a function of the geometric structure of the scene, solar zenith angle, and optical properties of the scene components (leaves and soil). For complete homogeneous vegetation canopies, the principal trend observed at all sun angles and spectral bands is a minimum reflectance near nadir and increasing reflectance with increasing off-nadir view angle for all azimuth directions.

400 citations


Journal ArticleDOI
TL;DR: Two-dimensional sinusoid fitting and Fourier transform methods of analyzing fringes to determine the wave-front topography are described and are accurate.
Abstract: Two-dimensional sinusoid fitting and Fourier transform methods of analyzing fringes to determine the wave-front topography are described. The methods are easy to apply because they do not require finding fringe centers and fringe orders. Also, they are accurate. For an active optics experiment in which we have used these techniques, experimental noise exceeds the error resulting from analysis of noise-free theoretical fringe patterns.

389 citations


Journal ArticleDOI
TL;DR: An inversion algorithm, involving a linear least-squares method, is developed to analyze the intensity data obtained by application of the traveling knife-edge method, and diameters can be measured to an accuracy of 0.05%.
Abstract: An inversion algorithm, involving a linear least-squares method, is developed to analyze the intensity data obtained by application of the traveling knife-edge method. Through use of simulated intensity data, diameters can be measured to an accuracy of 0.05%. The method also yields good results when it is applied to He–Ne laser beam data.

366 citations


Journal ArticleDOI
TL;DR: Simple procedures and formulas for tracing the characteristics of a spherical Gaussian beam through a train of lenses or mirrors are described which are analogous to those used in geometrical optics to trace repeated images through an optical train.
Abstract: Simple procedures and formulas for tracing the characteristics of a spherical Gaussian beam through a train of lenses or mirrors are described which are analogous to those used in geometrical optics to trace repeated images through an optical train.

339 citations


Journal ArticleDOI
TL;DR: Substantial increases in the packing densities of SiO2, TiO2 , and ZrO2 films have been produced as measured by the reduction in the adsorption of moisture when the films are exposed to a humid atmosphere.
Abstract: Some effects on the properties of electron-beam evaporated thin films produced by ion bombardment of the growing film are reported. Substantial increases in the packing densities of SiO2 , TiO2 , and ZrO2 films have been produced as measured by the reduction in the adsorption of moisture when the films are exposed to a humid atmosphere. In a ZrO2-SiO2 multilayer interference filter, changes in the wavelength of the peak transmittance on exposure to the atmosphere have been reduced from 8 nm for films deposited without ion bombardment to <1 nm for ion-beam-assisted films.


Journal ArticleDOI
TL;DR: It is shown that errors can occur in calculating the true rms surface roughness from actual TIS measurements; ways to correct these errors are discussed.
Abstract: Previously published vector equations describing angle-resolved scattering from single-layer- and multilayer-coated optics have been integrated numerically and analytically over all angles in the reflecting hemisphere to obtain numerical results and analytical expressions for total integrated scattering (TIS). The effects of correlation length, polarization, angle of incidence, roughness height distribution, scattered light missed by the collecting hemisphere, and roughness cross-correlation properties of the multilayer stack on the TIS expression are considered. Background material on TIS from optics coated with single opaque reflecting layers is given for completeness and comparison to corresponding multilayer TIS results. It is shown that errors can occur in calculating the true rms surface roughness from actual TIS measurements; ways to correct these errors are discussed.

Journal ArticleDOI
TL;DR: A high spectral resolution lidar technique to measure optical scattering properties of atmospheric aerosols is described, and Aerosol optical properties, such as the backscatter ratio, optical depth, extinctionCross section, scattering cross section, and theBackscatter phase function are derived.
Abstract: A high spectral resolution lidar technique to measure optical scattering properties of atmospheric aerosols is described. Light backscattered by the atmosphere from a narrowband optically pumped oscillator-amplifier dye laser is separated into its Doppler broadened molecular and elastically scattered aerosol components by a two-channel Fabry-Perot polyetalon interferometer. Aerosol optical properties, such as the backscatter ratio, optical depth, extinction cross section, scattering cross section, and the backscatter phase function, are derived from the two-channel measurements.


Journal ArticleDOI
TL;DR: A semiautomatic method is described for measuring, fast and accurately, the mode propagation losses of planar or channel waveguides for integrated optical circuits and it is feasible over a broad range from low loss to high loss.
Abstract: A semiautomatic method is described for measuring, fast and accurately, the mode propagation losses of planar or channel waveguides for integrated optical circuits. It involves a video camera aided by a microcomputer, and the real-time measurement is feasible over a broad range from low loss (<1 dB/cm) to high loss (of the order of 102 dB/cm). We examined the propagation properties of several optical waveguides prepared by sputtering or ion migration.

Journal ArticleDOI
TL;DR: A device utilizing four inversion layer photodiodes in a light-trapping arrangement was constructed and tested and it was found that applying a reverse bias voltage extended the high quantum efficiency response over the entire visible spectrum and up to the highest radiant power level studied.
Abstract: A device utilizing four inversion layer photodiodes in a light-trapping arrangement was constructed and tested. The device was found to have a photon-to-electron conversion efficiency of 0.999 for short wavelength and low power visible radiation. It was found that applying a reverse bias voltage extended the high quantum efficiency response over the entire visible spectrum and up to the highest radiant power level studied (several milliwatts). Several radiometrically important characteristics were studied and the results presented: spectral reflectance; polarization sensitivity; quantum efficiency vs wavelength, photon flux density, and reverse bias voltage; and dark current vs reverse bias.

Journal ArticleDOI
TL;DR: A new technique has been developed that employs highly focused laser beams for both generating and detecting thermal waves in the megahertz frequency regime and includes a comprehensive 3-D depth-profiling theoretical model; it has been used to measure the thickness of both transparent and opaque thin films with high spatial resolution.
Abstract: A new technique has been developed that employs highly focused laser beams for both generating and detecting thermal waves in the megahertz frequency regime. This technique includes a comprehensive 3-D depth-profiling theoretical model; it has been used to measure the thickness of both transparent and opaque thin films with high spatial resolution. Thickness sensitivities of ±2% over the 500–25,000-A range have been obtained for Al and SiO2 films on Si substrates.

Journal ArticleDOI
TL;DR: The properties of optical elements fabricated by holographically recording an ultrahigh spatial-frequency pattern in a photoresist mask followed by reactive ion etching to transfer this pattern into the surface of a quartz substrate are discussed.
Abstract: In this paper we discuss the properties of optical elements fabricated by holographically recording an ultrahigh spatial-frequency pattern in a photoresist mask followed by reactive ion etching to transfer this pattern into the surface of a quartz substrate. Such optical elements are environmentally durable, potentially easy to replicate, and exhibit diffraction efficiencies in excess of 85%. In addition, two other properties are reported for the first time. Such elements at normal (0°) incidence are antireflective, with broadband reflection coefficients as low as 0.035%. Also, the elements exhibit artificially produced birefringence making them useful as wave plates. These results may be particularly significant in the UV and IR, where damage-resistant antireflection coatings and transparent birefringent materials may not exist.

Journal ArticleDOI
TL;DR: Solution of the small-angle approximation of Weinman et al.1 is piled on the solution of the truncation approximation to synthesize the intensity field in the solar aureole to estimate the forward parts of the aerosol phase functions and retrieval of aerosol volume spectra.
Abstract: Solution of the small-angle approximation of Weinman et al.1 is piled on the solution of the truncation approximation to synthesize the intensity field in the solar aureole. Accuracy within ±3% is attained for almost all parts of the sky and for air masses less than ∼5. An iterative algorithm utilizing this calculation scheme is applied to the spectral aureole and extinction measurements to estimate the forward parts of the aerosol phase functions and to retrieve the aerosol volume spectra from them.

Journal ArticleDOI
TL;DR: Simple and useful approximations, valid at infrared wavelengths, to the equations for synchrotron radiation are presented and used to quantify the brightness and power advantage of current synch Rotron radiation light sources over conventional infrared broadband laboratory sources.
Abstract: Simple and useful approximations, valid at infrared wavelengths, to the equations for synchrotron radiation are presented and used to quantify the brightness and power advantage of current synchrotron radiation light sources over conventional infrared broadband laboratory sources. The Daresbury Synchrotron Radiation Source (SRS) and the Brookhaven National Synchrotron Light Source (vacuum ultraviolet) [NSLS(VUV)] storage rings are used as examples in the calculation of the properties of infrared synchrotron radiation. The pulsed nature of the emission is also discussed, and potential areas of application for the brightness, power, and time structure advantages are presented. The use of infrared free electron lasers and undulators on the next generation of storage ring light sources is briefly considered.

Journal ArticleDOI
TL;DR: A new lidar scheme using a pseudorandom code modulated cw laser as a transmitting laser source (RM-CW lidar) is proposed and a demonstration of its use for aerosol measurement is shown.
Abstract: A new lidar scheme using a pseudorandom code modulated cw laser as a transmitting laser source (RM-CW lidar) is proposed and a demonstration of its use for aerosol measurement is shown. A formula for estimating the SNR values in RM-CW lidar was derived, and it was demonstrated that the observed SNR value was in good agreement with the calculation.

Journal ArticleDOI
TL;DR: Spectrally separated fluorescence emissions from liquid and vapor diesel fuel can be obtained by adding an exciplex-forming molecule to the fuel by dominating the condensed phase emission and the monomer emission.
Abstract: Spectrally separated fluorescence emissions from liquid and vapor diesel fuel can be obtained by adding an exciplex-forming molecule to the fuel. The exciplex emission dominates the condensed phase emission, while the monomer emission dominates the vapor phase emission. In particular with the naphthalene/tetramethyl-p-phenylene diamine system, the liquid and vapor phase emissions peak at 470 and 380 nm, respectively. Results for droplets at 110 and 250°C are presented.

Journal ArticleDOI
TL;DR: In this paper, a method for determination of the optical constants of a variety of coating materials is described based on the use of an optical thin film synthesis program to adjust the constants of dispersion equations until a good fit is obtained between measured and calculated spectral transmittance and or reflectance curves.
Abstract: A versatile method for determination of the optical constants is described that can be applied to a variety of coating materials. It is based on the use of an optical thin film synthesis program to adjust the constants of dispersion equations until a good fit is obtained between measured and calculated spectral transmittance and/or reflectance curves. The sensitivity of the determination can be increased by a suitable combination of measurement quantities. Because more than the minimum amount of data can be used, sensitivity to measurement errors and the chances of obtaining multiple solutions can both be reduced. To illustrate the method optical constants are determined of MgF2, ZnS, MgO, Inconel, and Si films in the visible part of the spectrum and of ITO films in the 0.4–12.0-μm range.

Journal ArticleDOI
TL;DR: An application of speckle photography techniques to unsteady gas flow measurements is presented and it is shown that 2-D velocity fields can be measured even when the flow is not perfectly 2D.
Abstract: An application of speckle photography techniques to unsteady gas flow measurements is presented. The instrumentation developed for the analysis of double-exposure photographs by digital signal processing is described. It is shown that 2-D velocity fields can be measured even when the flow is not perfectly 2-D. Accuracy and limitations of these techniques are discussed.

Journal ArticleDOI
TL;DR: The feasibility and advantages of using atomic vapor cells as blocking filters for measuring atmospheric parameters are demonstrated with a numerical example worked out in detail.
Abstract: A new lidar technique for measuring the profiles of backscatter ratio, atmospheric visibility, and atmospheric temperature is proposed. Based on the theory of high resolution Rayleigh/Mie scattering, the feasibility and advantages of using atomic vapor cells as blocking filters for measuring atmospheric parameters are demonstrated with a numerical example worked out in detail. Ten percent accuracy in determining backscatter ratio and visibility can be achieved easily. With a SNR of 300, temperature of 1 K accuracy can be measured directly along with the backscatter ratio to a better accuracy of ±1%. Using a large lidar system and assuming 50-km visibility, the proposed technique can be applied to measure backscatter ratio and temperature profiles simultaneously for a 10-km path with 30-m depth resolution in 3 min. With higher SNR the atmospheric pressure profile can also be determined.

Journal ArticleDOI
TL;DR: The application of a general-purpose image-processing computer system to automatic fringe analysis is presented and three areas of application have been examined where the use of a system based on a random access frame store has enabled a processing algorithm to be developed to suit a specific problem.
Abstract: The application of a general-purpose image-processing computer system to automatic fringe analysis is presented. Three areas of application have been examined where the use of a system based on a random access frame store has enabled a processing algorithm to be developed to suit a specific problem. Furthermore, it has enabled automatic analysis to be performed with complex and noisy data. The applications considered are strain measurement by speckle interferometry, position location in three axes, and fault detection in holographic nondestructive testing. A brief description of each problem is presented, followed by a description of the processing algorithm, results, and timings.

Journal ArticleDOI
TL;DR: A set of holographic filters was developed to convert the Gaussian intensity distribution of a collimated laser beam into a uniform one and experimental results are shown.
Abstract: A set of holographic filters was developed to convert the Gaussian intensity distribution of a collimated laser beam into a uniform one. The design and the fabricating method of the holographic filters are presented and experimental results are shown.

Journal ArticleDOI
TL;DR: Three algorithms for implementing an improved composite image construction by setting criteria for selecting the in-focus segments of an image sample are discussed.
Abstract: Improvement in the depth of field is demonstrated by properly processing a succession of image samples. Due to the limited depth of field each image sample has in-focus as well as out-of-focus segments. By setting criteria for selecting the in-focus segments, an improved composite image is formed. Three algorithms for implementing this construction are discussed.

Journal ArticleDOI
TL;DR: The diameter and refractive index of micrometer sized spherical dielectric particles are simultaneously deduced using the wavelength dependence of backscattering data from optically levitated particles to represent the most accurate determination of absolute size andRefractive index yet made by light scattering.
Abstract: The diameter and refractive index of micrometer sized spherical dielectric particles are simultaneously deduced using the wavelength dependence of backscattering data from optically levitated particles. The accuracy of the results is set by experimental errors in the determination of the wavelength of backscatter resonance peaks and the ratio of slopes of specified peaks. At present the refractive index and diameter can be deduced with relative errors of 5 x 10(-5). This represents the most accurate determination of absolute size and refractive index yet made by light scattering. A reduction of these errors by an order of magnitude is possible. We assume a priori knowledge of diameter and refractive index with accuracy of 10(-1) and 5 x 10(-3), respectively.