laser anti-counterfeiting technology includes laser holographic image anti-counterfeiting identification, encrypted laser holographic image anti-counterfeiting identification and laser holographic lithography anti-counterfeiting technology.
first generation laser anti-counterfeiting technology
the first generation laser anti-counterfeiting technology is laser molded holographic image anti-counterfeiting logo.
holography was discovered by American scientist M.J. Buerger when taking pictures of the atomic structure of crystals with X-rays, and together with dennis gabor, a holographic theory was established: by using the principle of double-beam interference, the object light and another beam (reference beam) which is coherent with the object light can generate an interference pattern to "merge" the phases, so that the lower phase can be recorded simultaneously with the photosensitive film. However, holography is shot according to the principle of interferometry and must be recorded with high-density (resolution) photosensitive film. Due to the poor monochromaticity and coherence of ordinary light sources, the development of holographic technology is slow, and it is difficult to shoot decent holograms. It was not until the appearance of laser in the early 196s that its characteristics of high brightness, high monochromaticity and high coherence rapidly promoted the development of holographic technology. Many kinds of holograms were produced, and the holographic theory was well verified. However, due to the special requirements of shooting and reproduction, it was almost confined to the laboratory since its birth.
in the late 197s, it was found that holographic pictures had a surface structure (i.e. criss-crossing interference fringes) including three-dimensional information, which could be transferred to high-density photographic plates and other materials. In 198, American scientists transferred the holographic surface structure to polyester film by using the embossing holographic technology, thus successfully printing the world's first embossed holographic picture. This kind of laser holographic picture, also known as rainbow holographic picture, is made on plastic film by laser plate making, which produces colorful diffraction effect and makes the picture have a two-dimensional and three-dimensional sense of space. Under ordinary light, hidden images and information will reappear. When the light shines from a certain angle, a new image will appear. This kind of embossed holographic picture can be copied quickly in large quantities like printing, with low cost, and can be used in combination with various printed materials. At this point, holography has taken a decisive step towards social application.
At that time, the production technology of this kind of molded holographic picture was very advanced and only a few people mastered it, so it was used as an anti-counterfeiting mark. The anti-counterfeiting principle is as follows:
1. In the whole process of laser holographic picture shooting, if one condition is different (such as the condition of shooting rainbow hologram), the effect of holographic identification will be different.
2. The holographic information of this holographic image cannot be photographed by ordinary photography, so it is difficult to copy the holographic pattern.
Johnny Walke Whishy (a whisky) was the first to use holographic pictures as anti-counterfeiting marks. When it was applied in Thailand, it was said that its sales increased by about 45%.
The laser-molded holographic anti-counterfeiting technology was introduced into China in the late 198s and early 199s, especially during 199-1994. Hundreds of production lines were introduced from all over the country, accounting for more than half of the world's manufacturers at that time. At the initial stage of introduction, this anti-counterfeiting technology did play a certain anti-counterfeiting role, but with the passage of time, the laser holographic image production technology spread rapidly, and now it has been broken by counterfeiters from all aspects, almost completely losing its anti-counterfeiting ability.
technical comments
laser anti-counterfeiting marks have the following inherent defects when they are produced:
1. Only relying on the confidentiality and control of production technology to prevent counterfeiting.
2. It belongs to simple observation anti-counterfeiting technology, and its observation point is mainly to see whether it is a holographic image, and secondly to see whether the pattern conforms to the published pattern, but ordinary consumers can distinguish two different versions of holographic logo only by careful comparison.
3. There is no technical method to prevent the anti-counterfeiting mark itself from being reused.
4. there is no technical method to prevent the packaging with anti-counterfeiting marks from being reused.
5. there is no technical method to prevent counterfeiters from obtaining anti-counterfeiting marks by means of buying and bribing.
second, the improved laser holographic image anti-counterfeiting logo
because the first generation of laser holographic anti-counterfeiting logo has completely lost its anti-counterfeiting function, people have to start to improve it. There are three main improvement methods: the first is to improve the holographic image by computer technology, the second is to develop a transparent laser holographic image anti-counterfeiting logo, and the third is to reflect the laser holographic image anti-counterfeiting logo.
2.1 Improvement of computer image processing technology
The improvement of laser holographic image by computer image processing technology has gone through two stages. The first stage is computer synthetic holographic technology. This technology is that a series of ordinary two-dimensional images are optically imaged, processed according to the principle of holographic image, and recorded on a holographic recording material to form a computer pixel holographic image. When observing this pixel holographic image, different three-dimensional images can be seen from different perspectives. The second stage is computer-controlled direct exposure technology, which is different from ordinary holographic imaging. This technology does not need to shoot the object, and the required patterns are completely generated by the computer. By controlling two coherent beams by the computer to generate all the patterns point by point, the angle between the two beams can be changed for different points, thus making a three-dimensional hologram with special effects.
2.2 transparent laser holographic image anti-counterfeiting technology
The ordinary laser holographic image is made of aluminized polyester film by molding (or the polyester film can be molded first and then aluminized). The function of aluminizing is to increase the intensity of reflected light and make the reproduced image brighter. The illumination light and observation direction are on the observer's side, so the laser rainbow molded hologram is opaque. The improvement of transparent laser holographic image is actually to cancel the aluminum plating layer, and the holographic image is directly molded on the transparent polyester film. In 1996, China's Ministry of Public Security decided to apply the transparent laser rainbow embossed hologram to the resident ID card. The ID card was completely covered and sealed by the transparent film. When the front of the card was observed under the light, not only the certificate could be seen clearly, but also the two-dimensional and three-dimensional rainbow holographic images (Chinese and English characters of the Great Wall and China) reproduced on the transparent film could be seen.
2.3 reflection laser holographic image anti-counterfeiting technology
reflection hologram is to shoot incident laser onto a transparent holographic latex medium, and part of the light is used as reference light, and the other part illuminates the object through the medium, and then the object scatters back to the medium as object light. The object light and the reference light interfere with each other to generate multi-layer interference fringe surfaces inside the medium, and the negative film of the medium is processed to generate multi-layer semi-transparent reflection surfaces inside the medium (for example, there can be more than 2 reflection surfaces in a 6 micron thick latex layer). In the process of hologram reproduction, the hologram is illuminated by a white point light source, and the multi-layer semi-transparent reflecting surface generated inside the medium reflects the light back, and the virtual image of the original object can be seen against the reflected light, so it is called a reflection hologram.
technical comment
these improvements in laser anti-counterfeiting technology have not and are unlikely to extend the life cycle of laser holographic image anti-counterfeiting technology, because these improvements only increase the difficulty of image manufacturing to varying degrees, and fail to improve even the inherent shortcomings of laser holographic image anti-counterfeiting, and the original problems still exist.
III. Anti-counterfeiting technology of encrypted holographic image
The encrypted holographic image uses optical image coding encryption technology such as random phase coding image encryption, moire coding image encryption and laser speckle image encryption to encrypt the anti-counterfeiting image, and obtains an encrypted image that is invisible or becomes some speckle. Among them, the image encrypted by random phase coding is invisible, and the original image can only be displayed by using a special photoelectric decoder, which is not suitable for general goods. At present, it is mainly used for anti-counterfeiting of various cards. Images encrypted by moire code and laser speckle can only be displayed if they are superimposed with the decoded grating or decoded speckle, which can be used for general commodity anti-counterfeiting.
the principle of encryption image anti-counterfeiting is that the encrypted image is invisible or noisy, and it is difficult to decipher without a key, so it has certain anti-counterfeiting function.
technical comments
in fact, these technologies are originally an image encryption technology, and it is really reluctant to use them for anti-counterfeiting. First of all, the image encrypted by random phase coding, although it needs special instruments to display, is it difficult to have it in today's high-tech and international counterfeiting? How difficult is it to decipher? As for the images encrypted by moire code and laser speckle, it is easier to counterfeit, because consumers get not only the anti-counterfeiting logo with encrypted images, but also the decoding grating or decoding speckle for verifying the authenticity. Since then, the encryption of images has not played any role in anti-counterfeiting, and the anti-counterfeiting of such anti-counterfeiting logos depends entirely on the difficulty of mastering the manufacturing technology of encrypted images. It is not very difficult to master this technology
IV. Laser holographic lithography anti-counterfeiting technology
Laser holographic lithography anti-counterfeiting technology is also called laser coding technology, also known as laser "burning" technology. Because the laser encoder is expensive and not widely used, it is only used in occasions where mass production or other printing methods cannot be realized. Because of this, it has played a role in anti-counterfeiting packaging. Laser coding sealing technology is a good container anti-counterfeiting technology. After the product is filled, sealed and capped, laser printing is carried out at the joint between the lid and the container, so that the upper half of the font is printed on the lid and the lower half is printed on the container. The anti-counterfeiting function of this technology lies in:
(1) Packaging containers cannot be reused. The new lid matches the old container, and the handwriting is difficult to align.
(2) The laser is expensive, and the code is printed on the production line. It is difficult for ordinary counterfeiters to invest huge sums of money to buy this equipment
(3) Manufacturers can change printing templates at will, and use different templates on different dates. Only a few people know the details of the replacement, and it is difficult for outsiders to crack it.
from the perspective of anti-counterfeiting effect, laser coding technology is even better than laser holographic image technology. The laser holographic logo is printed by a printing factory, and the manufacturer who uses the logo cannot ensure that the master will not flow out of the printing process or be illegally copied. For counterfeiters, laser holographic marks can be purchased directly in batches, without equipment investment or mastering the technology. While using laser coding technology to prevent counterfeiting, the first problem that counterfeiters encounter is the expensive equipment investment. Laser encoder is expensive, and it must be used online. In addition, the change of font template is secret, which makes it difficult for scattered small and medium-sized factories to make fakes. For these reasons, the life of packaging with laser coding technology is longer than that with laser holography.
technical comment
although the anti-counterfeiting effect of laser holographic lithography is better than some anti-counterfeiting marks, it also has the following shortcomings:
1. Because the laser encoder is expensive, it is difficult for small and medium-sized enterprises to adopt it.
2. Relying on high investment barriers to prevent counterfeiting, once counterfeiters have this kind of equipment, their anti-counterfeiting function will immediately fail
General technical comment:
Laser holographic anti-counterfeiting technology is a modern laser application technology achievement that has received widespread attention at home and abroad in recent years, and it is favored and loved by consumers for its profound holographic imaging principle and colorful flash effect. Laser holographic anti-counterfeiting logo can be widely used in famous trademarks, securities, confidential cards and luxury handicrafts in light industry, medicine, food, cosmetics and electronics industries. Compared with general printed trademarks, it has unique advantages and charm. However, there are many domestic manufacturers and their management is extremely chaotic, which greatly affects their credibility in the eyes of the public. This technology is suitable to be combined with other anti-counterfeiting technologies, such as laser holographic comprehensive anti-counterfeiting, laser code composite, laser ink composite, packaging laser composite and so on.