It’s not refraction, it’s specular reflection
Its cross-section is like an open folding fan. When you look at it from an angle of about 45 degrees to the left, you see the direction perpendicular to your line of sight. One, the other is invisible because it is parallel to your line of sight, and vice versa
With the rapid development of holographic anti-counterfeiting technology, laser holographic labels can not only present a three-dimensional effect, but also can Changes in the viewing angle cause a series of changes in the image, and the effect cannot be achieved by ordinary printing methods.
Laser holographic anti-counterfeiting technology is a modern laser application technology that has received widespread attention at home and abroad in recent years. As a result, it has won the favor of consumers with its profound holographic imaging principle and colorful flash effect.
Laser holographic images are also called rainbow holographic images. Laser holographic technology belongs to the holographic grating technology in optics. Its product is very different from ordinary photos. It can not only reproduce the main image of the original object, but also show the shape of different sides of the original object depending on the direction of sight. Laser holograms have received widespread attention and application in the field of anti-counterfeiting due to their magical colors, realistic images, high information content, and the ability to be copied in large quantities through lamination.
Laser holographic image anti-counterfeiting technology uses laser plate making to produce images on plastic films, producing colorful diffraction effects. It also makes the picture have a sense of two-dimensional and three-dimensional space. Under ordinary light, the hidden images and information will reappear. When light shines at a certain angle, a new image appears. This molded holographic image can be reproduced in large quantities and quickly, just like printing, at a lower cost, and can be combined with various printing technologies.
This kind of laser anti-counterfeiting mark has inherent flaws in its initial stage: it only relies on the confidentiality and control of the production technology to prevent counterfeiting; it is a simple observation anti-counterfeiting technology, and its observation point is mainly to see whether it is holographic. image, and secondly to see whether the pattern conforms to the published pattern, but ordinary consumers can only distinguish two different versions of the holographic logo when comparing carefully; there is no technical method to prevent the anti-counterfeiting logo itself from being reused; there is no prevention of anti-counterfeiting attached There is no technical method for the labeled packaging to be reused; there is no technical method to prevent counterfeiters from obtaining anti-counterfeiting labels by means of bribery or bribery.
When laser embossed holographic anti-counterfeiting technology was introduced into our country in large quantities in the late 1980s and early 1990s, hundreds of production lines were introduced across the country, accounting for more than half of the world's manufacturers at that time. Although this anti-counterfeiting technology did play a certain anti-counterfeiting role in the early days of its introduction, as time went by, laser holographic image production technology spread rapidly. Now it has been broken by counterfeiters from all aspects, and its anti-counterfeiting effect has almost been completely lost.
Therefore, on this basis, computer technology has been used to improve holographic images, transparent laser holographic image anti-counterfeiting signs and reflective laser holographic image anti-counterfeiting signs.
Computer image processing technology has experienced two development forms to improve laser holographic images. The first form is computer-generated holographic technology. This technology is to optically image a series of ordinary two-dimensional images, process them according to the imaging principle of holographic images, and then record them on a piece of holographic recording material, thereby forming a computer pixel holographic image. When observing this pixel holographic image, you can see different three-dimensional images at different viewing angles. Its graphics and colors have extremely flexible and dynamic effects and are not limited by the direction of the reproduced light. The second form is computer-controlled direct exposure technology. Different from ordinary holographic imaging, this technology does not require a subject to be photographed. The required graphics are completely generated by a computer. The computer controls two coherent beams to generate all patterns point by point in units of pixels. The clamp between the two beams can be changed for different points. angles to produce three-dimensional holograms with special effects.
Ordinary laser holographic images are generally made of aluminum-plated polyester film that is molded (it can also be molded with polyester film first and then aluminum-plated). The function of aluminum plating is to increase the intensity of reflected light. Makes the reproduced image brighter. With both illumination light and viewing direction on the observer's side, the laser rainbow embossed hologram is opaque.
The transparent laser holographic image actually eliminates the aluminum coating and embosses the holographic image directly on the transparent polyester film.
The imaging principle of reflected laser holographic image is to shoot the incident laser onto the transparent holographic latex medium. Part of the reflected light is used as the reference light, and the other part is transmitted through the medium to illuminate the object, and then the object is scattered back to the medium as the object. Light, object light and reference light interfere with each other, generating multi-layer interference fringe surfaces inside the medium. After the medium film is processed, multi-layer semi-transparent reflective surfaces are generated inside the medium (for example, a 6-micron thick latex layer can have more than 20 reflections surface), a white light point light source is used to illuminate the hologram, and the multi-layered semi-transparent reflective surface generated inside the medium reflects the light back. Facing the reflected light, a virtual image of the original object can be seen, so it is called a reflection laser hologram. But these improvements essentially do not change the inherent shortcomings of this technology.
Encrypted holographic image anti-counterfeiting technology is a more advanced technology than laser holographic image anti-counterfeiting marking technology. Its encrypted holographic image adopts methods such as random phase coding image encryption, Moiré coding image encryption, laser speckle image Encryption, an optical image coding encryption technology, encrypts the anti-counterfeiting image to obtain an encrypted image that is invisible or becomes speckles. The image encrypted by random phase encoding is invisible, and only a specialized photoelectric decoder can display the original image.
Although this kind of image encryption technology requires special instruments to display, it is easily counterfeited in today's high-tech and international world. Because when consumers purchase goods, they not only get anti-counterfeiting labels containing encrypted images, but also decoding gratings or decoding speckles used to verify authenticity. As a result, the encryption of images does not play any role in anti-counterfeiting. The anti-counterfeiting of this kind of anti-counterfeiting logo completely depends on the difficulty of mastering the manufacturing technology of encrypted images, and mastering this technology is not very difficult. Therefore, this anti-counterfeiting technology also has shortcomings.
The latest anti-counterfeiting technology is: presenting hidden images from holograms.
It is a silver-white holographic anti-counterfeiting technology introduced to the market by Toppan Printing Co., Ltd. using electron beam technology (EB) in 1994 (the silver-white color of the usual hologram will change with different viewing angles). The color changes, and this silver-white hologram is fixed as silver-white no matter what angle it is viewed from), which is a new anti-counterfeiting technology. This technology retains the dazzling visual effect of the original silver-white holographic technology. When a special simple detector is used to detect it, the coded image hidden in the hologram is immediately visible. Images hidden in high-definition images that can be observed with detection devices can be continuous, multi-screen images stored at any location. This is the first of its kind in the world and has a high anti-counterfeiting effect and is easy to detect. Features. Hidden images can be made on linear and striped holographic films that often appear in gift certificates, stocks and other securities (intellectual property rights include 7 patent applications).
With the continuous innovation and development of holographic technology, many new technologies using holograms as carriers have emerged, such as dynamic holographic technology, 2D/3D technology, dot matrix holographic technology, micro-encryption technology, and synthetic encryption. technology, actinic relief technology, machine identification information technology, etc. This makes holographic anti-counterfeiting technology have both first-line and second-line anti-counterfeiting characteristics. It is believed that holographic technology will become one of the most widely used anti-counterfeiting technologies with the strongest anti-counterfeiting capabilities. With its unique artistic effect and anti-counterfeiting performance, it will be widely used in the field of printing and packaging. been applied on a large scale.