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What is a reflection hologram Figure 1 (omitted) shows the recording hologram recording process. When the incident laser beam hits the transparent medium, part of the light is used as a reference light, and the other part of the light is transmitted through the medium to illuminate the object, and then the object is scattered back to the medium to generate a multilayer interference fringe surface in the medium. The medium film is processed in the medium. Multiple layers of transparent reflective surfaces are created internally (for example, there are more than 20 reflective surfaces in a 6 μm thick latex layer). Figure 2 (omitted) shows the reflection hologram reproduction process. At this time, the object does not exist, and when the hologram is irradiated with the white light source, the virtual image of the original can be seen against the reflected light, and thus it is called a reflection hologram.
Application of reflection holograms The reflection holograms described above are monochromatic and do not exhibit rainbow changes. Three-dimensional imaging can have a great depth and viewing angle. Because the interference fringe surface generated by it penetrates deep into the interior of the medium instead of being concentrated on the surface, it cannot be copied by molding. This kind of early application in the field of cultural relics display, treasure display, souvenirs, decorations, holographic elements and other fields, the media used silver salt, dichromate gelatin and so on. The use of reflection holograms for anti-counterfeit markings is a recent matter. The medium used is photopolymer, which can be processed in real-time and facilitates the automation of mass optical copies.
Commercially available true color three-dimensional holograms DAI NIPPON PRINTING CO., LTD (DNP) has recently launched a commercially available true color three-dimensional photopolymer (PHOTOPOLYMER) hologram film that can be mass-reproduced. Color three-dimensional photography, publishing and printing, product promotion, packaging and decoration, security security, souvenir production and other aspects have been applied.
The company has successfully produced a series of true color three-dimensional holograms, among which there are 3000 "POCKET MONSTER" holograms for gift card production, and 12,000 "ASTRO BOY" holograms for Promotion/commemoration card production; 5,000 true-color 3D holograms used in the field of trade; in addition, they also created “PARROTS IN THE JUNGLE†for the covers of the MARKET PLACE magazine (8th edition) distributed all over the world. The parrot in the) true color 3D hologram. These true-color three-dimensional holograms have vivid colors, high brightness and large field of view, which have attracted the attention of the international holographic community and are considered to be new breakthroughs in commercial true color three-dimensional holography.
The recording material of commercially available true color three-dimensional photopolymer holograms that can be mass-reproduced by Japan DNP Corporation is a new full-color photopolymer holographic recording material of HRF 800001-15 recently introduced by DuPont, which is characterized by various visible light waves. The sensitivity range and refractive index change range are large, and a hologram with high brightness and a large field of view can be produced.
Different holographic recording materials have different characteristics:
1, silver salt emulsion holographic media, high sensitivity, but a smaller range of refractive index changes;
2, dichromated gelatin holographic media, refractive index changes in a wide range, but the sensitivity is low;
3, photopolymer emulsion holographic media, high sensitivity, refractive index change range is also very large, suitable for the reproduction of high brightness, large hologram. In addition, this medium can be processed in real time with dry processing (only ultraviolet irradiation and heating, which eliminates the traditional wet processing method). Therefore, the photopolymer latex holographic medium is particularly suitable for the production of holographic masters. Make bulk contact copies.
DuPont Photovoltaic Polymer Coats is still 5 micron and is generally coated on a 0.002 inch thick MYLAR polyester base film. A 0.00092 inch thick MYLAR polyester film is applied to the surface of the latex.
Japanese DNP company introduced their production steps:
1. Design, depending on the needs of customers;
2. Model making, elaborate production and color matching of three-dimensional objects or two-dimensional planes;
3, master production;
4, copy, exposure on a special dedicated machine;
5, processing, using heating and UV irradiation method to reproduce the image of a stable, bright hologram, DNP company uses DuPont's oven and laminating machine;
6, after processing, according to the needs of customers for gluing, die-cutting and other steps.
DNP's production continues to increase, making it possible to make multiple rolls of holograms per day, each roll being one foot wide and 500 feet long. The price of the hologram is calculated as 2 inches x 2 inches, which is about 70 yen (about 0.5 USD).
American holographic expert Hans BJELKHANGEN thought: “The new full-color photopolymer holographic recording material recently introduced by DuPont Company is especially suitable for true color three-dimensional holography, although its sensitivity is slightly higher than that of silver salt emulsion holographic media. It is low, but it can be processed in real time with a dry process, so it is especially suitable for making large-scale contact copies after the silver salt master is made. When recording, attach the film to the glass plate with matching liquid (be careful not to make the glass plate Air bubbles or dust remain. To achieve high-volume production, special machines are required for copying. The RGB (red, green and blue) trichromatic ratio can be taken as 4:1:2, and 3 lasers can be scanned at the same time. Exposure intensity Can select 10 millijoules per square centimeter.After the laser scanning exposure is over, it needs to be exposed to strong white light or ultraviolet light, DuPont suggested that the exposure intensity can choose 100 millijoules per square centimeter, the wavelength can choose 350-380 nanometers. It is heated in an oven at a temperature of 120 degrees Celsius for 2 hours to enhance the brightness of the reproduced image.
DNP claims that the lasers they use are: helium ion lasers for red light; argon ion lasers for green light, diode-pumped solid-state lasers, dye lasers; and argon-ion lasers for blue light.
Commercialization and application of reflection holograms
In recent years, rainbow molded hologram anti-counterfeiting labels have been widely used in China, and their characteristics have been familiar to people. With the development of holographic anti-counterfeiting technology, another kind of anti-counterfeiting label for holograms, the anti-counterfeiting label for reflection holograms, has entered the market quietly. Several companies in Taiwan and the United States have successively demonstrated and introduced such useable polymers in China. Reflective hologram anti-counterfeit labels made of media are refreshing. At present, this type of anti-counterfeiting label has been used in imported cameras in 1996, the National Ninth Five-Year Spark Program promotion project in 1998, and international Sanshou competition tournament tickets in 1998. It has achieved great success and made people realize once again that the application of laser holography technology. Anti-counterfeiting artistic charm and anti-counterfeiting efforts.