Improved phase modulation method based on moire effect

Abstract

The invention discloses an improved phase modulation method based on moire effect. The method comprises the following steps that step 1, a host image is selected, the host image is decomposed to enable the host image to be composed of a channel C, a channel M, a channel Y and a channel K which are with four colors; step 2, the host image is carried out halftone processing, the four color channelsare correspondingly provided with dot adding parameters for dot adding processing, wherein the dot adding parameters comprise the dot adding angles, the dot adding angle of the mother plate is theta,and a mother plate half-tone graph and three auxiliary plate half-tone graphs which are composed of dots are obtained; and step 3, anti-counterfeiting information are hidden. According to the method,threshold values for generating the dots overlapping are determined, and the distance and the angle which can be modulated by the dots are optimized.

Description

technical field [0001] The invention belongs to the technical field of printing anti-counterfeiting, and in particular relates to an improved phase modulation method based on the moiré effect. Background technique [0002] The limit resolution ability of normal human vision is limited. When the size and pitch of dots in the digitally screened image are smaller than the limit resolution ability of human vision, the human eye cannot distinguish the dots. Therefore, in fact, the discretized binary image is discontinuous, but due to the visual characteristics of the human eye, if you look at it at a certain viewing distance, you cannot distinguish the dots at all, that is, you cannot distinguish the image details, and finally give people a continuous tone. image effects for print reproduction of continuous tone originals. [0003] Grating anti-counterfeiting is the anti-counterfeiting technology produced by the combination of halftone screening technology and Moiré effect. The ...

AI Technical Summary

Problems solved by technology

[0007] 1. There is a far-reaching technical bias in the principle of optimal outlets: Existing studies all believe that the displacement setting of outlets must meet the principle of optimal outlets. Only when the outlets that make up the anti-counterfeiting information are at the optimal location, when the digital grating detects the anti-counterfeiting information, The reproduction of anti-counterfeiting information is the most obvious and clear, but there has been a habitual technical bias in the prior art for many years, and it is believed that the best point is only to move D / 2 along the direction of the screen angle or the direction perpendicular to the screen angle, resulting in theoretical Guidance angle The angle and distance that can be adjusted by the net point are very limited;

[0008] 2. The research on the overlap of dots is not in place: In order to realize the moiré effect, all the dots in the dot selection area are considered to be displaced in the same way. The displacement direction is along the direction of the screen angle or the direction perpendicular to the screen angle. The displacement distance It is D / 2, that is, in the existing method, the dots of all color values ​​(dot percentage) are generalized, and there is no pertinence; at the same time, since the screening parameters will be set in the early halftone processing, the number of screen lines is a known number , the number of screen lines determines D and the side length D of a single screen adjustment unit 2 , D=D 2 , therefore, D / 2 is a fixed value; however, for some dots located on the border of the dot selection area, the actual movable distance is the distance between the closest points of the two dots, which is recorded as D 1 , with the increase of dot percentage, D 1 will gradually decrease, therefore, D 1 is a variable; when D 1 When it is less than D / 2, if the phase modulation is still carried out according to the method of the prior art, it will cause overlapping between the network points on the boundary, cause strong visual perception, and make the anti-counterfeiting invalid. The actual distance between the network points has not been considered in the prior art Synergistic impact on concealment and extraction performance

Images