Table of contents

A new and simple method for pseudo-coloring a photograph in a coherent optical processing system, utilizing a newly developed technique of half-tone screens, is described. By selective spatial filtering of the high diffraction orders in the Fourier plane of a coherent optical system, images with up to ten contours of constant brightness have been generated on a picture from a single half-tone copy of that picture. The pseudo-coloring of the picture is achieved by mixing the high-diffraction-order outputs generated by lasers of different wavelengths. In the experiment described herein, an argon laser and a He-Ne laser were used. The experimental results demonstrate that the method has considerable flexibility. A discussion of the theory, the method, and potential applications is given.

The colour distribution in the Polychromatic Line Spread Function is computed in the case of primary aberrations. Different corrections of longitudinal and transverse chromatism, constant and dispersive cases of spherical aberration, coma and astigmatism have been considered. The calculations have been carried out for source C, and the standard observer, specified by the three sensitivity functions of the human eye CIE 1931.

An object illuminated with partially coherent light is imaged through a square law medium characterized by the dielectric variation (r, z) = ₀(1 - α²r²). We have studied the performance of this medium as an imaging element. An expression for the intensity distribution at the observation plane is derived and is found to be formally identical to the homogenous case. This formal identity is used to obtain an expression for the optical transfer function in the incoherent case. The variation of the degree of coherence at the observation plane is also considered in a special case when the object is incoherently illuminated.

The apodization problem is solved analytically for determining the pupil function (amplitude distribution over the exit pupil) which minimizes the second moment of the intensity distribution in the Fraunhofer diffraction pattern of a point object, on the conditions that the central intensity is prespecified to take a certain value less than that for the standard Airy-type optical system without filter and that the optical system is a passive one. The problem is treated for a rotationally symmetric optical system without aberrations. The method used to solve the problem is the calculus of variations of unconventional type involving the constraint of inequalities due to the passivity of the optical system. A detailed derivation of the optimum pupil function is presented and discussion on the resultant pupil function is given.

Waves whose amplitudes become null at infinity are searched. The problem is reduced to the research of solutions of a two partial derivatives equations system. For the cartesian components of fields it proceeds the orthogonality condition of the isophase and the equiamplitude surfaces and the conditions of equality between the wave vector modulus and the propagation constant of the medium. The waves, the longitudinal components, isophases and equiamplitudes of which, have the same revolving axis, are studied in the case where the phase is proportional to the course. The waves, the equiamplitudes of which are orthogonal to plane isophases, have a constant in the whole space wave vector. More, if, the equiamplitudes are plane the solution are the plane and uniform heterogeneous waves (the plane and homogeneous waves are a peculiar case). If the cylindrical components, equiamplitudes are circular cylinders and if their isophases are plane, there are solutions with finite amplitude everywhere and null amplitude in any direction except the one of the propagation. They give a representation of a parellel light beam. A method to elaborate such a beam is suggested. Two of those beams, of the same frequency, which follow the same way, conduct to the interferences specifical to heterogeneous waves.

Photovoltaic phenomena similar to phototransition effects are induced in ZnS sputtered films by light of energy beneath the band-gap (not more than 0.22 eV). It is advanced that hot electron may escape from the photoionized coulombic centre and moves to some level within shallow traps distribution. Thickness dependent phenomena confirm the existence of a critical thickness in which the density of coulombic centres is higher.

When light intensities are distributed on a spherical wave according to a gaussian law, it is possible to obtain an accurate analytic relationship expressing the N_i number of ions created in a K-photon ionization experiment.

This relationship may be considered, for a given K value, as a function of p = A int ^T₀ Γ^K₀ dt which is called ionization probability at the center of curvature of the wave. It has been numerically computed with K = 2 through 7, 11 and 19.

At last, it is shown how to get out of experimental results the value of A with the help of the graphs N_i(p, K).