Finding of the optimal parameters of animated and stereographic rainbow diffractive images

摘要

We have considered the basic aspects of the technology of animated andudstereographic rainbow images. These images can be included in Optical Security Devicesud(OSDs) in order to increase their structure complexity and to improve their protectiveudproperties. The cited technology provides, on the one hand, a simple identification on theudvisual level of verification and, on the other hand, the sufficient reliability againstudcounterfeits. The last property is achieved at first by the division of the elemental unit onudelemental regions of any adjusted shape with outline of the precision that is inaccessibleudfor the recreation without Electron Beam Lithography Equipment (EBLE) which is usedudfor the recording of OSDs. Second, the used encoding methods also assure the certainudreliability.ududIn the context of the paper, the theoretical discussion based a quantitative formulation ofudthe Huygens--Fresnel law of the diffraction on an elemental diffractive grating is carriedudout. For other definite Conditions of Lighting and Observation of Diffracting Lightud(CLODL), the correlation between the slope angle of diffraction grating strokes and theudcorresponding horizontal parallax angle is got; and the parameter which defines theudchannel selection (the quality of splitting into separate channels) is introduced. The ruleudfor the definition of the wavelength and the intensity of light that diffracts on a givenudgrating under certain CLODL is derived as well. This fact allows one to create theudsoftware utility that models the behavior of anigrams or stereograms.udAn algorithm of the synthesis of anigrams and stereograms as parts of OSDs using theudtechnology of a composite “figure” elemental unit (that is composed from parts of anyudshape) and applying the halftone encoding by the period, filling, and achromaticity or alludthese parameters at once is elaborated, and its software implementation is constructed.udThe criteria for the choice of such anigram’s parameters as the resolution, number ofudchannels, and angle distances between them are elaborated. In order to check them, theudresults of tests are summarized. The investigation of the optimal parameters of halftoneudimages’ encoding finding is implemented, and the results obtained for the tough andudflexible linkings of a channel to the subregion of an elemental unit for hatching imagesudare compared.