In the standard reflectance model for inhomogeneous materials it is assumed that light is reflected by two independent mechanisms. One component is reflected at the interface of the material and air. Light reflected b...
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In the standard reflectance model for inhomogeneous materials it is assumed that light is reflected by two independent mechanisms. One component is reflected at the interface of the material and air. Light reflected by this mechanism does not interact with surface colorant, and its spectral composition is assumed to equal that of the incident light. The second component is reflected after entering and interacting with the subsurface structure of the material. This interaction substantially changes the spectral composition of the reflected light. We adopt a vector analysis technique for testing the standard reflectance model. Further, we develop a computational method to determine the components of the observed spectra, and we obtain an estimate of the illuminant without using a reference white standard. Finally, we evaluate the accuracy of the standard model and the feasibility of the illuminant spectral estimation by using several test objectives.
Three methods have been described for computing the two-dimensional, discrete Hartley transform. Two of these employ a separable transform; the third method, the vector-radix algorithm, does not require separability. ...
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Three methods have been described for computing the two-dimensional, discrete Hartley transform. Two of these employ a separable transform; the third method, the vector-radix algorithm, does not require separability. In-place computation of the vector-radix method is described. Operation counts and execution times indicate that the vector-radix method is fastest.
A method for computing the optical properties of contoured layered media is presented. The wave equation is solved in the layers by invoking the Rayleigh hypothesis, and the solution is expressed as a scattering matri...
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A method for computing the optical properties of contoured layered media is presented. The wave equation is solved in the layers by invoking the Rayleigh hypothesis, and the solution is expressed as a scattering matrix that relates the Fourier components of the incoming fields to those of the outgoing fields. Images of layered structures produced by a given optical system can then be calculated by combining the scattering matrix representing the object with matrices that represent the illumination and projection optics and that include the effects of apertures and aberrations. The application of this method to partially coherent imaging is described.
Instabilities and transition to optical turbulence in a phase-conjugate resonator are numerically investigated under the influence of more than one control parameter. The dynamics of intracavity modes, including one t...
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Instabilities and transition to optical turbulence in a phase-conjugate resonator are numerically investigated under the influence of more than one control parameter. The dynamics of intracavity modes, including one transverse spatial dimension, is considered under various conditions and in different regions of the multidimensional parameter space. A great variety of phenomena is observed, including Feigenbaum, intermittency and the Ruelle–Takens–Newhouse route to chaos, spatial filamentation and making the beam profile chaotic, coexisting attractors and boundary crises, optical bistability and dynamical effects, and inverse bifurcations. The route to high-dimensional chaos in this infinitely dimensional dissipative dynamical system is monitored qualitatively and quantitatively by using embedding techniques, Fourier and Lyapunov spectra, Poincaré sections, and bifurcation diagrams. We find similarities and significant differences with other infinite systems, notably with fluid dynamical flows and a time-delay differential equation.
Finding the relationship between two coordinate systems by using pairs of measurements of the coordinates of a number of points in both systems is a classic photogrammetric task. The solution has applications in stere...
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Finding the relationship between two coordinate systems by using pairs of measurements of the coordinates of a number of points in both systems is a classic photogrammetric task. The solution has applications in stereophotogrammetry and in robotics. We present here a closed-form solution to the least-squares problem for three or more points. Currently, various empirical, graphical, and numerical iterative methods are in use. Derivation of a closed-form solution can be simplified by using unit quaternions to represent rotation, as was shown in an earlier paper [J. Opt. Soc. Am. A 4 , 629 (1987)]. Since orthonormal matrices are used more widely to represent rotation, we now present a solution in which 3 × 3 matrices are used. Our method requires the computation of the square root of a symmetric matrix. We compare the new result with that obtained by an alternative method in which orthonormality is not directly enforced. In this other method a best-fit linear transformation is found, and then the nearest orthonormal matrix is chosen for the rotation. We note that the best translational offset is the difference between the centroid of the coordinates in one system and the rotated and scaled centroid of the coordinates in the other system. The best scale is equal to the ratio of the root-mean-square deviations of the coordinates in the two systems from their respective centroids. These exact results are to be preferred to approximate methods based on measurements of a few selected points.
A numerical method for eliminating channel spectra from data obtained with a bandlimited infrared Fourier transform spectrometer is developed. The method is compared with others in common use on a synthetic model spec...
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A numerical method for eliminating channel spectra from data obtained with a bandlimited infrared Fourier transform spectrometer is developed. The method is compared with others in common use on a synthetic model spectrum.
The new 4x4 matrix method described by Lin-Chung and Teitler [P. J. Lin-Chung and S. Teitler, J. Opt. Soc. Am. A 1, 703 (1984)] is used to study the optics of multilayer magnetooptic recording media. It is demonstrate...
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The new 4x4 matrix method described by Lin-Chung and Teitler [P. J. Lin-Chung and S. Teitler, J. Opt. Soc. Am. A 1, 703 (1984)] is used to study the optics of multilayer magnetooptic recording media. It is demonstrated that the method is capable of handling very complicated optical multilayer structures. For a quodrilayer magnetooptic recording system consisting of an overcoat layer, a magnetic layer, an intermediate dielectric layer, and a reflector, the readout of the system is optimized against the thickness of the overcoat and intermediate layers. As well, cases of oblique angle of incidence, anisotropy in the nonmagnetic part of the dielectric constants, and misalignment of the magnetization are treated.
This paper presents a passive method for computation of thermal IR transmittance over slant paths. This double viewing angle technique utilizes data gathered by a radiometer or imager carried by a manned or unmanned a...
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This paper presents a passive method for computation of thermal IR transmittance over slant paths. This double viewing angle technique utilizes data gathered by a radiometer or imager carried by a manned or unmanned aircraft. A sensitivity analysis showed the effect of changes or errors in input parameters on calculated transmittances. The analysis suggested the applicability and limitations of this method. Accuracies attainable through the use of the double viewing angle method appear to be similar to those from more complex techniques for many atmospheric conditions.
In this paper we analyze factors influencing the accuracy and precision of optical density measurement of light microscopical objects. The study is applied to the DNA content of Feulgen-stained cells using a low-resol...
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In this paper we analyze factors influencing the accuracy and precision of optical density measurement of light microscopical objects. The study is applied to the DNA content of Feulgen-stained cells using a low-resolution, TV-equipped microscope connected to a digital image processing system. Factors influencing the accuracy of density measurement include staining (not considered here), image formation (glare, focus, diffraction), image sampling (distribution, sampling density, noise), and computational accuracy. These factors are reviewed with respect to potential remedies. Evaluation of the measurement error contribution is performed on the level of the individual cell and on the specimen level. It is concluded that a coefficient of variation of 5% (in contrast to 3.5% using flow cytometry of the same specimen) in the measured values of normal cells of one specimen is attainable using adequate shading correction. With relatively simple computational methods, image cytometry may be well suited for pathology practice.
A simple technique for final correction of aberrated diffraction patterns calculated by using the fast-Fourier-transform–quasi-fast-Hankel-transform (FFT–QFHT) algorithm is proposed. In order to compensate for the i...
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A simple technique for final correction of aberrated diffraction patterns calculated by using the fast-Fourier-transform–quasi-fast-Hankel-transform (FFT–QFHT) algorithm is proposed. In order to compensate for the influence of the artificial obscuration in the sampling grid (which is unavoidable when Siegman’s QFHT algorithm is used), the proper field contribution associated with a defocused perfect system is finally added to the diffraction pattern just computed. Such a global correction technique utilizes simple analytic approximations to corresponding diffraction integrals and permits the number of samples in the exit pupil to be reduced significantly. On the basis of first numerical experiments it appears that a factor-of-4 improvement in both running time and occupied memory is achieved.
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