Computer Optics

312-321

Authors: V.V. Kotlyar, A.A. Kovalev, A.P. Porfirev

We derived exact analytical relationships to describe the complex amplitude of a perfect optical vortex generated by means of three different optical elements, namely, (i) an amplitude-phase element with the transmission function proportional to a Bessel function, (ii) an optimal phase element with transmission equal to the sign function of a Bessel function, and (iii) a vortex axicon. The doughnut intensity was shown to be highest when using an optimal phase element. The vortex-axicon-aided intensity ring was found to be about twice as wide as when generated using two other elements under analysis. Thus, the optimal filter was shown to be best suited for generating a perfect optical vortex. Simulation results were shown to corroborate theoretical predictions, with the experiment being in agreement with theory and simulation.

331-337

Authors: S.I. Kharitonov, S.G. Volotovsky, S.N. Khonina

The work is devoted to the study of the point spread function of a harmonic diffractive lens illuminated by non-monochromatic radiation using a hybrid geometrical and wave optics approach.

346-352

Authors: L.L. Doskolovich, E.S. Andreev, E.V. Byzov

A new variant of source-to-target mapping for the design of mirrors generating prescribed twodimensional intensity distributions is presented. Design examples show high performance of the proposed technique: for rectangular and elliptical uniform intensity patterns of the angular size varying from 80°×20° to 40°×20° the relative error is less than 8.5%.

360-369

Authors: M.A. Bolotov, V.A. Pechenin, S.P.Murzin

This paper presents a method for estimating the uncertainty of spatial mating of high-precision parts using optical measurements. The method is applicable in computer designing for optical and mechanical systems, taking into account the manufacturing uncertainties and relative position their elements. Another of its application can be to find the most acceptable method of assembly and adjustment of precision optical systems based on the results of measurements of the geometry of mating parts. The method involves the analysis of parts geometry deviation on the results of the optical measurements; creating of geometric models for real surfaces of the parts, the calculation of relative spatial arrangement of parts in modeling their mates using the modernized of the iterative closest points algorithm (ICP).

380-387

Authors: A.Y. Denisova, Y.N. Juravel, V.V. Myasnikov

In this paper, we propose a novel method for estimating parameters of a linear spectral mixture for hyperspectral images. This method allows omitting a preliminary atmospheric correction of the input image. In order to derive a solution of the mixture problem different models of radiation transmission in atmosphere are considered. An evaluation of the effects of noise, the number of input pixels, and the number of signatures on the accuracy of the linear mixture coefficient restoration and the input pixel representation error is made.

395-403

Authors: I. A. Kunina, S. A. Gladilin, D. P. Nikolaev

In this paper, we present an automatic technique for compensation of radial distortion, which is characteristic of wide-angle lenses. The proposed method estimates distortion parameters using a single image from unknown source. No calibration objects are required, but it is assumed that the original scene contains straight lines. The method is based on finding such radial distortion parameters, that maximize total length of linear segments. We employ a fast Hough transform to estimate the overall curvature of lines without selecting any. The proposed algorithm is tested on real images obtained using calibrated camera lenses with different radial distortion. For the formal evaluation of the algorithm, we propose a quality measure for geometric distortion compensation, which works correctly even in the case when the problem of determining the coefficients is ill-conditioned.

410-415

Authors: N.N. Vasin, R.R. Diyazitdinov

We propose a machine vision system for the inspection of the railway track condition. Key stages of an algorithm for detecting gauge marks that serve to identify mechanical stresses of a continuous welded rail track are described. In the final section of the article, we discuss some peculiarities found in real exploitation conditions: effects of the rail surface defects on the algorithm performance and false detection of railway infrastructure elements similar to gauge marks.

422-426

Authors: S.D. Poletaev, S.G. Volotovsky

We discuss a problem of reducing the thickness of lines of the contact pattern masks produced by laser ablation of thin films of refractory metals and used when synthesizing the micro-relief of diffractive optical elements (DOEs). For a contact mask for a DOE on molybdenum, patterns with features in the range 0.25-0.3 µm were recorder by laser ablation on 40-nm thick films. This is approximately 3 times smaller than the characteristic dimensions obtained by thermochemical recording chromium films of the same thickness in the standard process. A microrelief of height of up to 300 nm was formed in a quartz substrate by reactive ion etching in an inductively coupled plasma through the mask. We show that thin molybdenum films can have promising applications as metallic masks when synthesizing a DOE microrelief.