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In a few earlier communications, spatial-transverse-impulse response (STIR) associated with the initial field transversely distributed across the entrance pupil of an inhomogeneous optical wave guide (photoreceptor) has been investigated. In the present work, effects of indetermination in the location of the origin on an arbitrarily defined refractive index profile, representing the degree of inhomogeity at the aperture pupil of a single receptor, have been studied. Some consequences related to a few possible technical applications have been discussed.

Rigorous approximation techniques for the scattering of a classical electromagnetic wave by fixed obstacles are studied. For that purpose, a new Green's function G^T is introduced, which is divergenceless throughout all space and, hence, less singular at short distances than the one commonly used Γ. The two scattering integral equations for the total electric field with G^T and Γ respectively, as well as their iterations, are studied comparatively. It is concluded that the iterations of the integral equation containing G^T converge under more general conditions than those for the one containing Γ, so that G^T is, for rigorous studies, more suitable than Γ.

We present here numerical estimates of the density and flux of energy based on physical parameters associated with the absorption properties of certain types of absorbing optical waveguides. These results are based on a theoretical formalism established previously for the initial field incident upon the entrance pupil of an absorbing optical waveguide. Based on these results, the mechanisms of confined energy transmission and possible cross talk between neighboring waveguides are discussed. Some comments on the behavior of Bessel functions with complex arguments are also included in the discussion.

A three-dimensional analysis of bending losses in dielectric optical waveguides is presented. It constitutes a nontrivial generalization of previous two- and three-dimensional studies by other authors. Our analysis is based on homogeneous integral equations for the total radiation field and suitable asymptotic approximations for Green’s functions. A key role is played by a new three-dimensional approximation for a relevant Bessel function with large order and argument (the former being larger than the latter). A nontrivial check of the consistency of all those approximations is given. General formulas are presented for the radiated field and the energy flow and for a bending-loss coefficient in three dimensions. Numerical results are also given, in order to assess the difference between the results of other authors and ours. Such a difference is rather small for monomode behavior near cutoff, increases as the behavior of the waveguide changes from monomode to multimode, and decreases as the parameter V increases for a given core radius and propagation mode.

The authors present a mathematically exact formulation of the initial field striking the aperture of an absorbing optical waveguide, via an integral equation description. An analysis of the residual scattering by the waveguide is presented. Because of the presence of the non-negligible absorption coefficient, the solution for the fraction of the confined power is obtained by performing non-trivial integrations of Bessel and Hankel functions with complex arguments. In order to carry out a numerical analysis a specific computational method is applied by using an approximated polynomial expansion whose validity is also discussed.

We outline ,a systematic procedure for formulating the general transfer function of a compound optical system working in the Fresnel regime.

It is known that the cones and rods of the retina have directional sensitivity. For a normal observer, in the absence of aberrations like myopia, astigmatism, etc. the light entering the pupil of the eye is directly focussed on the retinal plane by the optical system of the eye. There, in the retina, the cones and the rods are regularly distributed in different retinal regions forming a mosaic structure. It is very well established from the earlier works of Enoch, (1), that both types of optical photoreceptors act as optical waveguides. This behaviour can be accounted for due to their special optical properties allowing conditions for total internal reflections inside its structure. At the time of the confinement of the energy inside each single receptor an important phenomenon of orientation takes place as well. In this work, we wish to establish that the various effects arising out of this phenomenon can be interpreted in terms of a possible apodising action of the eye.It will be shown that an improvement in the resolution of the retinal image detection is possible by comparing the human visual system with an apodised optical system. For that purpose we have established a linear array model for a section of the fovea, ( all receptors having the same geometry and optical properties ), then, we have calculated the distribution of the density of energy captured in this particular section of the retina, by assuming that the receptors are acting as monomode optical waveguides.The orientation mechanism is also considered, by including an inclination factor affecting each single receptor. We have compared the so obtained distribution to the one associated to a single receptor© (1987) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An exact formulation of the electromagnetic field striking an optical waveguide is presented and compared with the decomposition relationship used in the literature. The expression for the critical angle is derived as a natural consequence of this formulation. Equations for the total fraction of power confined within a waveguide are derived and analyzed for the special case of absorbing waveguides. An explicit expression is derived for the fraction of energy confined within a waveguide supporting two sets of modes.