Showing papers in "Journal of the Optical Society of America in 1980"
TL;DR: Two-dimensional image moments with respect to Zernike polynomials are defined, and it is shown how to construct an arbitrarily large number of independent, algebraic combinations of zernike moments that are invariant to image translation, orientation, and size as discussed by the authors.
Abstract: Two-dimensional image moments with respect to Zernike polynomials are defined, and it is shown how to construct an arbitrarily large number of independent, algebraic combinations of Zernike moments that are invariant to image translation, orientation, and size. This approach is contrasted with the usual method of moments. The general problem of two-dimensional pattern recognition and three-dimensional object recognition is discussed within this framework. A unique reconstruction of an image in either real space or Fourier space is given in terms of a finite number of moments. Examples of applications of the method are given. A coding scheme for image storage and retrieval is discussed.
2,362 citations
Journal Article•
1,602 citations
TL;DR: It is argued that the visual cortex representation corresponds closely to the Gabor scheme owing to its advantages in treating the subsequent problem of pattern recognition.
Abstract: On the basis of measured receptive field profiles and spatial frequency tuning characteristics of simple cortical cells, it can be concluded that the representation of an image in the visual cortex must involve both spatial and spatial frequency variables. In a scheme due to Gabor, an image is represented in terms of localized symmetrical and antisymmetrical elementary signals. Both measured receptive fields and measured spatial frequency tuning curves conform closely to the functional form of Gabor elementary signals. It is argued that the visual cortex representation corresponds closely to the Gabor scheme owing to its advantages in treating the subsequent problem of pattern recognition.
1,307 citations
TL;DR: A masking model is presented that encompasses contrast detection, discrimination, and masking phenomena that includes a linear spatial frequency filter, a nonlinear transducer, and a process of spatial pooling that acts at low contrasts only.
Abstract: Contrast masking was studied psychophysically. A two-alternative forced-choice procedure was used to measure contrast thresholds for 2.0 cpd sine-wave gratings in the presence of masking sine-wave gratings. Thresholds were measured for 11 masker contrasts spanning three log units, and seven masker frequencies ranging +/- one octave from the signal frequency. Corresponding measurements were made for gratings with horizontal widths of 0.75 degrees (narrow fields) and 6.0 degrees (wide fields). For high contrast maskers at all frequencies, signal thresholds were related to masking contrast by power functions with exponents near 0.6. For a range of low masking contrasts, signal thresholds were reduced by the masker. For the wide fields, high contrast masking tuning functions peaked at the signal frequency, were slightly asymmetric, and had approximately invariant half-maximum frequencies that lie 3/4 octave below and 1 octave above the signal frequency. The corresponding low contrast tuning functions exhibited peak threshold reduction at the signal frequency, with half-minimum frequencies at roughly +/- 0.25 octaves. For the narrow fields, the masking tuning functions were much broader at both low and high masking contrasts. A masking model is presented that encompasses contrast detection, discrimination, and masking phenomena. Central constructs of the model include a linear spatial frequency filter, a nonlinear transducer, and a process of spatial pooling that acts at low contrasts only.
1,241 citations
TL;DR: In this paper, the problem of wavefront estimation from wave-front slope measurements has been examined from a least-squares curve fitting model point of view, and a new zonal phase gradient model is introduced and its error propagator, which relates the mean square wavefront error to the noisy slope measurements, has been compared with two previously used models.
Abstract: The problem of wave-front estimation from wave-front slope measurements has been examined from a least-squares curve fitting model point of view. It is shown that the slope measurement sampling geometry influences the model selection for the phase estimation. Successive over-relaxation (SOR) is employed to numerically solve the exact zonal phase estimation problem. A new zonal phase gradient model is introduced and its error propagator, which relates the mean-square wave-front error to the noisy slope measurements, has been compared with two previously used models. A technique for the rapid extraction of phase aperture functions is presented. Error propagation properties for modal estimation are evaluated and compared with zonal estimation results.
958 citations
TL;DR: Intensity-dependent parameters that stimulate the adaptation of receptors and opponent and nonopponent mechanisms are varied to predict a wide range of data for both normals and dichromats.
Abstract: The inclusion of cone mechanisms in a slightly revised version of an earlier model allows accounts of phenomena that involve receptor effects as well as dichromatic color vision. Intensity-dependent parameters that stimulate the adaptation of receptors and opponent and nonopponent mechanisms are varied to predict a wide range of data for both normals and dichromats, including: (i) color matching; (ii) the approximate apparent hue and saturation of the spectrum; (iii) foveal spectral sensitivities obtained by flicker photometry and by detection in the dark and under conditions of achromatic or chromatic adaptation; (iv) heterochromatic additivity failures in the dark-adapted and chromatically adapted eye; (v) approximate differences between brightness and luminance; and, (vi) color and wavelength discrimination under varying adaptation conditions.
236 citations
TL;DR: In this paper, a generalized least-squares wave front reconstruction problem with minimum norm is formulated and solved for a given array of phase-difference measurements and two different discretizations for the gradient are used and the reasons for the different results are given.
Abstract: Requirements for adaptive optics and compensating imaging systems lead to wave front reconstruction problems which we formulate as generalized least-squares problems. For a given array of phase-difference measurements, we construct explicit and exact solutions for the least-squares wave front error. Of particular interest are solutions with minimum norm. Two different discretizations for the gradient are used and the reasons for the different results are given.
215 citations
TL;DR: Components of the dielectric function of a biaxial crystal are related in a simple first-order approximation to pseudodielectric functions calculated in the isotropic two-phase model from ellipsometric data.
Abstract: Components of the dielectric function of a biaxial crystal are related in a simple first-order approximation to pseudodielectric functions calculated in the isotropic two-phase model from ellipsometric data. If |e| ≫ 1 and one of the principal axes is normal to the plane of incidence, the dominant contribution is shown to arise from the projection of the dielectric tensor onto the line of intersection between surface and plane of incidence.
182 citations
TL;DR: In this article, an intuitive argument is presented for the phase anomaly, that is, the 180° phase shift of a light wave in passing through a focus, and the treatment is based on the geometrical properties of Gaussian light beams.
Abstract: An intuitive argument is presented for the phase anomaly, that is, the 180° phase shift of a light wave in passing through a focus. The treatment is based on the geometrical properties of Gaussian light beams, and suggests a new viewpoint for understanding the origin of the phase shift. Generalizing the argument by including higher-order modes of the light field allows the case of a spherical wave to be treated.
178 citations
TL;DR: Spectacle blur decreases stereoacuity more than ordinary visual acuity, and this cannot be accounted for by contrast reduction or by accommodation and/or convergence instability, and representation of the whole spatial frequency spectrum is required.
Abstract: Spectacle blur decreases stereoacuity more than ordinary visual acuity, and this cannot be accounted for by contrast reduction or by accommodation and/or convergence instability. Stereoscopic acuity was measured over a range of defocus exceeding 2 D in normal subjects with a 3-mm artificial pupil. Blur of one eye leads to a decrement in stereoacuity that is at least as high and usually higher than blur of both eyes; blurring only the disparate element of the pattern while keeping the rest clear is nearly as detrimental as blurring the whole pattern. In a separate experiment, the individual line elements of the pattern were subjected to spatial frequency filtering in the horizontal direction. For best stereoacuity values, representation of the whole spatial frequency spectrum is required. Patterns with diminished high-frequency content (> 10 cycles/deg) show lowered stereoacuity and those utilizing predominantly a spatial frequency band centered on 22 cycles/deg even more so.
176 citations
TL;DR: By using violet backgrounds, blue-cone sensitivity is selectively altered but no change in flicker photometric sensitivity is found, indicating that blue cones do not contribute to luminance as defined by flickers photometry.
Abstract: By using violet backgrounds we selectively altered blue-cone sensitivity but found no change in flicker photometric sensitivity. This indicates that blue cones do not contribute to luminance as defined by flicker photometry.
TL;DR: In this paper, the theory of backscattering was extended to single-mode fibers, and the result of the present investigation is nearly the same as for multimode fibers although the theory in the latter case is based on a ray optical approach.
Abstract: The theory of the backscattering method, which so far has been known only for multimode fibers, is extended to single-mode fibers. Under certain conditions the result of the present investigation is nearly the same as for multimode fibers although the theory in the latter case is based on a ray optical approach.
TL;DR: In this article, a two-parameter phase function for highly anisotropic angular scattering distributions is described, which has a convenient analytic representation since it is the generating function for the Gegenbauer polynomials.
Abstract: A two-parameter phase function is described for highly anisotropic angular scattering distributions. The phase function has a convenient analytic representation since it is the generating function for the Gegenbauer (or ultraspherical) polynomials. Sample calculations illustrate the large variety of forward-to-backward scattering amplitudes and shapes that can be fit with the two parameters. Illustrative phase functions are given that approximate light scattering distributions predicted for several biological and atmospheric specimens from Rayleigh-Gans and Mie models. A suggested classification scheme for size and refractive index of microparticles in human blood is presented as a potential application of the phase function with two parameters.
TL;DR: Measurements in five young subjects with normal fundi indicate that the speed of the leukocytes in the macular capillaries of the retina is pulsatile.
Abstract: The blue field entoptic phenomenon consists of the perception of one’s own leukocytes (white blood cells) flowing in the macular capillaries of the retina. A method has been developed for determining the speed of the leukocytes. In this method, the motion of the leukocytes is simulated on a screen by means of a minicomputer system. The subject is instructed to match the motion of the simulated white blood cells with that of his own leukocytes. For this, he can adjust the number and the maximum and minimum speeds of the simulated particles. Measurements in five young subjects with normal fundi indicate that the speed of the leukocytes in the macular capillaries of the retina is pulsatile. Minimum and maximum speeds are approximately 0.5 and 1 mm/s.
TL;DR: In this paper, the dependence of atmospheric absorption and refraction upon fluctuations in temperature, humidity, and pressure was found for infrared frequencies, including line and continuum absorption and anomalous refraction by water vapor.
Abstract: The dependence of fluctuations in atmospheric absorption and refraction upon fluctuations in temperature, humidity, and pressure is found for infrared frequencies. This dependence has contributions from line and continuum absorption and from anomalous refraction by water vapor. The functions that relate these fluctuations are necessary for evaluating degradation of electromagnetic radiation by turbulence. They are computed for a given choice of mean atmospheric conditions and graphed as functions of frequency in the wavelength range 5.7 μm to radio waves. It is found that turbulent fluctuations in total pressure give a negligible contribution to absorption and refraction fluctuations. Humidity fluctuations dominate absorption fluctuations, but contributions by temperature and humidity affect refraction fluctuations. Sufficiently strong humidity fluctuations can dominate the refraction fluctuations for some infrared frequencies but not for visible frequencies. We examine the variance of log amplitude for scintillation of infrared light to determine whether absorption or refraction fluctuations dominate under several conditions.
TL;DR: In this article, a generalized brightness theorem was derived that describes the thermodynamic limitations of the fluorescent planar concentrator and the maximum brightness concentration ratio allowed by thermodynamics is exp (hΔν/kT) where Δν is the Stokes shift in fluorescence.
Abstract: A “generalized brightness theorem” is derived that describes the thermodynamic limitations of the fluorescent planar concentrator. The maximum brightness concentration ratio allowed by thermodynamics is exp (hΔν/kT) where Δν is the Stokes shift in fluorescence.
TL;DR: In this article, a simple operator algebra is proposed to describe Fourier diffraction by replacing the Fresnel-Kirchhoff integral, the lens transfer factor, and other operations by operators.
Abstract: Fresnel diffraction is described by replacing the Fresnel-Kirchhoff integral, the lens transfer factor, and other operations by operators. The resulting operator algebra leads to the description of Fourier optics in a simple and compact way, bypassing the cumbersome integral calculus. Aberration effects and Gaussian beam illumination are also treated as a simple extension of the present theory.
TL;DR: In this paper, a method for finding the electromagnetic fields scattered or guided by lossy dielectric gratings having arbitrary profiles is presented, which unifies the treatment of both perpendicular (TE) and parallel polarizations by expressing the fields in terms of two coupled first-order differential equations.
Abstract: Based on an exact solution of the pertinent boundary-value problem, a method is presented for finding the electromagnetic fields scattered or guided by lossy dielectric gratings having arbitrary profiles. This method unifies the treatment of both perpendicular (TE) and parallel (TM) polarizations by expressing the fields in terms of two coupled first-order differential equations. Their solution is obtained by resorting to difference equations in conjunction with the algorithm of Adams–Moulton, which easily leads to accurate results for a large variety of practical problems. To illustrate the application of this approach, quantitative results are presented for the scattering of plane waves by lossy corrugated structures and for the guiding of (leaky) surface waves by triangular gratings with symmetric or asymmetric profiles.
TL;DR: In this article, the authors used a speckle theory approach to study the frequency dependence of modal noise and measured and analyzed the correlation of two sparsification patterns as a function of source frequency difference.
Abstract: Under certain conditions a changing speckle pattern exists at the output plane of a multimode fiber, resulting in modal noise which can degrade the error performance of a fiber data link. Fiber motion is the usual cause of such speckle change, and Daino et al. have studied the first-order statistics of such modal noise, assuming a single frequency source. But source frequency variation can also cause modal noise; and source frequency diversity has been shown effective in its reduction. In this paper we use a speckle theory approach to study the frequency dependence of modal noise. We have measured and analyzed the correlation of two speckle patterns as a function of source frequency difference, and the speckle spatial frequency distribution as a function of fiber parameters. We have also measured the speckle contrast as a function of fiber length for several sources and fiber types. Such information permits the prediction of the modal noise statistics, from which corresponding changes in error rates can be derived.
TL;DR: In this paper, the diffusion equation is derived from the ordinary space-time transport equation having a scattering cross section of the form σ(Ω·Ω′), Ω and Ω′ being the azimuth vectors of incident and scattered waves.
Abstract: The diffusion equation is derived from the ordinary space-time transport equation having a scattering cross section of the form σ(Ω·Ω′), Ω and Ω′ being the azimuth vectors of incident and scattered waves. The condition of applicability is examined in detail. It is shown that the diffusion equation necessarily becomes first order in time in contrast to a recent paper on a similar subject in which it is given as second order in time. This is further confirmed for the case of isotropic scattering where an exact analytical solution is obtainable. The boundary conditions on a surface of medium discontinuity are also derived in the diffusion approximation and, in this connection, the pulse-width broadening in random media is investigated in terms of the pulse moments, which are obtained by solving boundary-value problems of a simple equation in space.
TL;DR: A model of the human eye is presented with the crystalline lens treated as having a gradient-index structure and an accommodation index I ranging from 0 to 1 is defined, finding the optical parameters of the eye in various states of accommodation.
Abstract: A model of the human eye is presented with the crystalline lens treated as having a gradient-index structure. By defining an accommodation index I ranging from 0 (unaccommodated) to 1 (accommodated), the optical parameters of the eye in various states of accommodation may be found. The results are in agreement with experimental values.
TL;DR: The stabilized spatiotemporal threshold response surface can be modeled as the linear difference between the threshold response surfaces of two mechanisms, each of which is simply the product of a spatial and temporal frequency response curve.
Abstract: The stabilized spatiotemporal threshold response surface can be modeled as the linear difference between the threshold response surfaces of two mechanisms, each of which is simply the product of a spatial and temporal frequency response curve. With no free parameters, the resulting model is shown to be a good fit to available data.
TL;DR: A large-field substitution procedure for making Rayleigh matches was used to study the color matches of eight red-green dichromats and two extreme anomalous trichromats, finding that seven of eight dichromat were still able to make unique matches with the rods desensitized.
Abstract: A large-field substitution procedure for making Rayleigh matches was used to study the color matches of eight red-green dichromats and two extreme anomalous trichromats. Matches were made under three experimental conditions: (1) During the cone plateau period after a bleach; (2) after the rods had recovered from the bleach; and (3) on a blue background. Under conditions (1) and (3) rods were desensitized and appear to be unable to contribute to the color match. Seven of eight dichromats were still able to make unique matches with the rods desensitized. The matches of six of these seven dichromats were consistent with predicted matches for simple protanomalous and simple deuteranomalous trichromats. Matches made under condition (2) were typically more nearly consistent with matches predicted for the rods and the remaining normal cone mechanism, but there were also some individual differences in these matches. The matches of the two extreme anomalous trichromats were similar to the matches of the dichromats.
TL;DR: It is suggested from the psychophysical data on two-point and line acuity that the smallest foveal channel in human vision must have an excitatory center with a diameter of around 1' 20".
Abstract: We suggest from the psychophysical data on two-point and line acuity that the smallest foveal channel in human vision must have an excitatory center with a diameter of around 1′ 20″. Taking into account the optics of the eye and the finite size of the receptors, we show that this would correspond well to the properties of a retinal ganglion cell receiving excitatory input from a single cone.
TL;DR: In this paper, the basic properties of propagation of electromagnetic waves in nonlinear media are a direct consequence of classical conservation laws for energy, and for components of momentum and angular momentum.
Abstract: Basic properties of propagation of electromagnetic waves in nonlinear media are a direct consequence of classical conservation laws for energy, and for components of momentum and angular momentum.
TL;DR: In this article, the Kubelka-Munk theory of light propagation in intensely scattering materials is extended for application to fluorescing media and applied to the plant sensory pigment system phytochrome that is masked by chlorophyll.
Abstract: The Kubelka–Munk theory of light propagation in intensely scattering materials is extended for application to fluorescing media. As an example, the extended theory is applied to the plant sensory pigment system phytochrome that is masked by chlorophyll.
TL;DR: In this article, the Mie theory applied to unagglomerated small carbon spheres can simulate the optical properties of acetylene smoke in the visible region but underestimates the specific extinction at 10.6 μm by at least a factor of 2.
Abstract: Optical extinction measurements of acetylene smoke in a 1.8-m tube at wavelengths of 0.5145 and 10.6 μm give specific extinction coefficients AE of 9.8 ± 0.8 and 0.94 ± 0.1 m2 g−1 respectively. The Mie theory applied to unagglomerated small carbon spheres can simulate the optical properties of acetylene smoke in the visible region but underestimates the specific extinction at 10.6 μm by at least a factor of 2. Both the visible and infrared experimental data are consistent with a model in which agglomeration of the smoke particles enhances the infrared extinction over that from small individual spheres.
TL;DR: A deterministic model for monocular space perception is presented, according to which retinal luminance changes due to involuntary eye movements are detected and locally analyzed to yield the angular velocity of each image point.
Abstract: A deterministic model for monocular space perception is presented. According to the model, retinal luminance changes due to involuntary eye movements are detected and locally analyzed to yield the angular velocity of each image point. The stable three-dimensional spatial coordinates of viewed objects are then reconstructed using a method of infinitesimal transformations. The extraction of the movement (parallax) field from the optical flow is represented by a set of differential equations, the derivation of which is based on the conservation of energy principle. The relation of the model to retinal neurophysiology and to various aspects of visual space perception is discussed.
TL;DR: In this article, the absorption coefficients of thin-film spectra of solid NH3 at a resolution of 1 cm−1 were used to determine its absorption coefficient over the range 50-7000 cm− 1.
Abstract: Thin-film spectra of solid NH3 at a resolution of 1 cm−1 were used to determine its absorption coefficient over the range 50–7000 cm−1. The thin films were formed inside a liquid N2 cooled dewar using a variety of substrates and dewar windows. The spectra were recorded with two Fourier spectrometers, one covering the range from 1 to 4 μm and the other from 2.6 to 200 μm. The thickness of the films was measured with a laser interference technique. The absorption coefficients were determined by application of Lambert’s law and by a fitting procedure to the observed spectra using thin-film theory. Good agreement was found with the absorption coefficients recently determined by other investigators over a more restricted wavelength range. A metastable phase was observed near a temperature of 90°K and its absorption coefficient is reported. No other major spectral changes with temperature were noted for the range 88–120°K.
TL;DR: In this paper, the theory of Bragg diffraction of finite beams by thick planar gratings is developed, using coupled-wave theory, and analytical expressions for the profiles of the transmitted and diffracted beams in the near field are obtained.
Abstract: The theory of Bragg diffraction of finite beams by thick planar gratings is developed, using coupled-wave theory. Simple analytical expressions for the profiles of the transmitted and diffracted beams in the near field are obtained. Detailed diffraction characteristics for the important case of Gaussian-profile beams are presented. It is shown that the diffraction characteristics depend only on two normalized parameters, the grating strength, and a geometry parameter. The diffraction efficiency and the profiles of the transmitted and diffracted beams are calculated as functions of these two controlling parameters.