New halftone screening method for security printing

I. Preface

With the increase in input/output resolution of color photocopiers, color scanners, and printers, imitations of securities prints have become easier to produce. At the same time, aiming at the use of sensors to exploit vulnerabilities of self-selling machines, it is no longer a matter of improving the sensors of self-sale machines. It is no better than going to the composition of the securities prints themselves and standing on a new perspective.

Recent securities prints have made it easy for ordinary users to judge the authenticity and have given technology such as holography or optical mutagenesis inks to ensure safety. However, these require special materials, generally expensive, and when the principle is seen, there is a danger of making similar imitations.

Therefore, according to the above principle, configuration, etc., it becomes more detailed or complicated, making it difficult to produce the same printed matter, even if a similar imitation product is made, as long as it is observed under a prescribed environment, it is rendered by the latent image. The gradation image, it is easy to judge the authenticity of the technology has been successfully developed.

In this paper, as an example, we have found an image processing method in which embedded images and embedded images are interleaved on the same plane in a securities print, and the core embedded technology is called ImageSwitch, which will be required for embedding. The software is called ScreenGeneratorSoftware. This kind of image embedding technology can not only produce marks with very high anti-counterfeiting effect, but also can be easily realized by four-color inks used in general commercial printing. In addition, a corresponding network-based security sign making system can be constructed.

The methods for judging the authenticity are as follows: the authenticity judgment method that does not require tools at all, the judgment method that uses simple tools, and the electronic authentication method that uses the Internet.

This article mainly describes its principle and various trial products and trial production methods.

II. Principle

The black ink among the basic four-color inks of CMYK used in general commercial printing is a black pigment mainly composed of carbon black and exhibits absorption from the ultraviolet region to the entire infrared region. In general, in the market, there are safe recording materials that can exhibit specific properties that do not absorb infrared light. However, in the basic four colors, CMY is always overlapped and the infrared light is not used. When using a special authentication device such as an infrared camera When observed, images printed with black ink containing carbon black can be seen.

Using this phenomenon, the bar code information (true information) containing carbon black and the bar code information (false information) of the same color that does not contain carbon black are arranged on the same plane, and can only be read by a special device such as infrared ray. The situation of real information has become a reality.

However, simply using bar-coded information makes it easier to recognize visually, and when it comes to seeing the principle, similar imitations can easily be made.

Therefore, as shown in Fig. 1, the technical information concerning Postscript language published by the Adobe company in the United States is discussed, focusing on the direct determination of the functions of the two kinds of outlet data (Threshold data), and by using this, two kinds of dot images have been developed. Image processing method staggered on the same plane.

FIG. 2 is a diagram illustrating the basic principle of an ImageSwitch in which two types of screens are interleaved. According to this principle, it is possible to indicate that there are two kinds of images on one plane. Needless to say, in this case, the respective components constituting the first image (visible image) and the second image (embedded image or latent image) are arranged so as to have a large first image area and a small second image area. In order to form two types of images, two kinds of image areas are staggered to fully represent the effect of image transition. Specifically, under normal conditions, only the first image can be seen, but under certain conditions, the first image disappears, and the latent image of the second image appears.

For example, according to the above, according to a special half-tone screening technology having a fine structure of two kinds of dots, equalization is achieved, and then commercial anti-counterfeiting technology for various applications comes into existence with the cooperation of special specifications of materials.

1.ImageSwitchYMCK

FIG. 3 is an illustration of the dot structure of the simplest ImageSwitch using the four-color ink for general commercial printing.

Under normal light sources, CMY overprinting can exhibit a similar carbon black color. The black system formed by the CMY group allows infrared rays to pass through, but the carbon black absorbs infrared rays. According to this principle, in the small image area (second image area) of FIG. 3 , dots (dots) are formed from carbon black, and black lines with CMY overlapping are disposed outside this dot.

In general, the CMY-matched color that does not absorb infrared light and the infrared-absorbing black that contains carbon black do not form an equal color relationship, but the second image field in which both are arranged has a fine structure and a resolution energy limit from the human eye. From the viewpoint of visual inspection, it is impossible to discriminate color difference, and because the image field is a subtle structure, it can be identified under a certain light source according to a certain density, and if it is under infrared light, it can be seen as a second image. The latent image. Further, this latent image can be used to change the area occupancy rate of the outlets and display a tone image. Therefore, the first image (consisting of the three primary colors of CMY) that can be seen under the normal light source disappears under the infrared ray, and a second image made of carbon black appears instead.

FIG. 4 is a river landscape for a mountain landscape image that is a halftone image P1 (visible image) and a halftone image P2 (embedded image or latent image), and each size is used for two types of screens (first dot area and second area). The dot matrix structure diagram of ImageSwitch, which is staggeredly configured.

For the first image area, the halftone dot image P1 arranged with circular dots is printed in CMY three colors, and for the second image field, the halftone dot image P2 arranged with round dots is printed in black, and the circular dot pattern of halftone dots image P2 is printed. The negative part is configured with CMY's three-color field.

In this case, the shape of the dot on each image area is not limited to a circular dot, but is changed to an irregular dot or a hyphenated character of a client company, or an input image added with a process is converted into a dot shape. Continuity of mesh points can be completely applied to the special shape of the dots.

Reprinted from: Chenyi Printing Network