Merezhany A., Antonyuk V. Genetic Algorithms Application For The Computer-Aided Design Engineering Of Mechanical Treatment Of Details. - Научно-теоретический и практический журнал "ОРАЛДЫН FЫЛЫМ ЖАРШЫСЫ" - № 1 (28) 2011.

This research examines the questions of genetic algorithms implementation for CAD EP of mechanical treatment in instrument and machine engineering. The advantages of genetic algorithms over existing tecniques of the computer-aided design are adduced. Analysis and choice of an optimization criterion of engineering processes are given.

Full article

Measurement of refraction distribution in the human eye opens new opportunities to make photorefractive surgery more accurate due to accounting imperfections not only of the cornea, but of the eye as an optical system. To calculate the to-be-ablated cornea layers, mathematical relations must be found between measured coordinates of retina ray tracings and transfer function of an eye. A new concept for modelling eye optical system is proposed using four phase transparencies, each of them exercising its own function: accommodation (equivalent to varifocal system), image focusing on the retina (optical system with constant optical power), regular aberrations (spherical and chromatic, astigmatism), and irregular phase distribution. It is shown, how the parameters, necessary for phase transparencies description, can be derived from direct and indirect measurements. Results of modelling experiment with simplified set of test points showed good sight correction. Investigated methodology proved to be fruitful even with limited number of test points and restricted length of polynomial approximation. In our refraction mapping system, transfer function reconstruction will use initial information from 65 points.
Keywords: eye model, phase transparency, retina ray tracing technique.

Full article

New horizons for accurate photorefractive sight correction, afforded by novel flying spot technologies, require adequate measurements of photorefractive properties of an eye. Proposed techniques of eye refraction mapping present results of measurements for finite number of points of eye aperture, requiring to approximate these data by 3D surface. A technique of wave front approximation with Zernike polynomials is described, using optimization of the number of polynomial coefficients. Criterion of optimization is the nearest proximity of the resulted continuous surface to the values calculated for given discrete points. Methodology includes statistical evaluation of minimal root mean square deviation (RMSD) of transverse aberrations, in particular, varying consecutively the values of maximal coefficient indices of Zernike polynomials, recalculating the coefficients, and computing the value of RMSD. Optimization is finished at minimal value of RMSD. Formulas are given for computing ametropia, size of the spot of light on retina, caused by spherical aberration, coma, and astigmatism. Results are illustrated by experimental data, that could be of interest for other applications, where detailed evaluation of eye parameters is needed.
Keywords: eye aberrations, sight correction, photorefractive operations, eye refraction map, refraction non-homogeneity, Zernike polynomials, eye refraction measurement.

Full article

In photorefractive sight correction, pre-operational computations of to-be-ablated layers are usually based on information about cornea shape that is one of the causes of aberrations. To obtain high-quality results of operation, contributions to aberrations of other origins are to be taken into account. Technique of eye-aberration mapping has been investigated, we called retina ray-tracing. It consists in directing into the eye a narrow beam, scanned (translated) in parallel to itself. Computer controls trajectory of scanning. Beam projection (spot of light) is formed on the retina. Aberrations result in varying position of the spot on retina in the course of scanning. Deviations from initial position are measured and reconstructed into wave aberration function. Mathematical relations, using Zernike polynomial expansions, were found to transform these data into necessary cornea shape correction with ablation technologies. In our experimental setup, we used the technique of acousto-optic scanning with frame time less than 10 ms for 65 sensed points. Eye-aberration mapping is realized with optical power resolution 0.1 diopter.
Key words: photorefractive sight correction, retina ray-tracing, acousto-optic scanning, Zernike polynomials, ablation technology, eye-aberration mapping, wave aberration function.

Full article

Full article