Anti-counterfeiting Method Optimization Based On Invisible Latent Image

The grating anti-counterfeiting technology is based on the halftone image screening and moire fringe principle.The phase modulation method is used to realize the embedding of the latent image,and the grating refraction performance is used to realize the extraction of the latent image.In this paper,based on the phase modulation grating anti-counterfeiting technology,combined with the characteristics of halftone image structure,the related experimental schemes of information hiding,latent image extraction,quality optimization and grating design are designed.The research contents mainly include the following aspects:To obtain the most suitable screening angle for latent image embedding and improve anti-counterfeiting quality,the correlation between anti-counterfeiting master screening angle and latent image was explored.Aiming at understanding the influence of the single master and double splicing master on the concealment and extraction for latent image,and the experimental design,analysis and evaluation were carried out.The C master was selected as a single master,and its screening angle was designed to be 0 °,15 °,45 °and 75 °.Then latent image information was embedded into the master of different angles.Designing the corresponding grating to extract the latent image,and the security characteristics were evaluated.The C and M masters were combined into a double master,forming a combination of six angle master.The "butterfly" shape were embedded into the left and right sides of the combined master,and the security characteristics were evaluated.The experimental results showed that screen angle could affect the anti-counterfeiting quality of the latent image.When the angle of the single master was 45°,the anti-counterfeiting effect was the best.The anti-counterfeiting characteristic was good when the angle combination was 0o+45°.To reveal the mechanism of the latent image affecting the color quality,the law of the phase modulation method on the dot properties was explored.Based on the minimum position transformation and center position transformation model in phase modulation,the effect of different paths on the latent image dot was studied,and the variation of the center distance and the area ratio were quantified,and the influence of the spatial distribution on the color development was analyzed.The results showed that the image color reproduction quality under the minimum position and center position model was 0.9113 and 0.8629,and the phase modulation method changed the spatial distribution of the dot,and the variation of dot arrangement and dot density affected the color rendering effect.For the minimum position modulation latent image,there was a problem that the upper and lower boundary dot jitters were so obvious that the image color could not be reproduced.The spatial attributes of the upper and lower boundary points were analyzed,and the modulation positions and percentage adjustment coefficients of the boundary points were calculated through theoretical derivation,so as to improve the traditional phase modulation method.The objectiveand subjective methods were used to compare and analyze the experiment.The results showed that the CISI was increased by about 10%,and the FSIMc was up to 99%,which showed that the improved method could significantly improve the color rendering effect of the image and was beneficial to the color reproduction.Aiming at the limitation that linear grating was only suitable for amplitude modulation image,the anti-counterfeiting technology of phase modulation latent image based on frequency modulation image was studied to expand the application scope.The latent image was hidden on the error diffusion screened image by phase modulation method,and the Mutual Information was taken as the evaluation index of the hiding effect.Based on the principle of grating extraction,an irregular grating was designed.And based on the concept of irregular grating design,the application scope in amplitude modulation image was explored.The experimental result showed that the irregular grating could clearly extract the latent image in the frequency modulation image,and was suitable for different tonality of the amplitude modulation image.The innovations of this paper were mainly reflected in the research of phase modulation latent image method,improving the anti-counterfeiting effect and image color rendering performance,and expanding the applicable range of phase modulation latent image anti-counterfeiting.It was a new development in the field of grating anti-counterfeiting technology.