Plastic card printing, such as that used for credit cards, often makes use of so-called holograms for security purposes. It’s important to distinguish the pseudo-holograms used on credit cards from “real” holograms that are formed on expensive dot matrix machines or through electron-beam lithography.
Not All Holograms Are the Same
The purpose of a security hologram is to make forgery difficult. It is used not only on credit cards, but also on the banknotes of several nations, on passports and on high-quality products, such as electronics. Credit card holography dates back to 1987 when the U.S granted a patent to Automatic Toll Systems, Inc., the forerunner of the popular E-Z-Pass systems used on many toll roads.
The “holograms” used on credit cards are actually multi-layer images that are stacked and alternately visible at different viewing angles. The technology is not very different from that used to manufacture red safety reflectors for vehicles. A 2D hologram has a background and foreground. Add a middle ground and you have a 3D version, which has a unique look consisting of multiple colors and levels. Credit card holograms seem to float above the surface of the plastic, while the background seems to recede into the body of the card, yielding the illusion of depth.
More advanced holograms, with a resolution of up to ten micrometers per element, are available from expensive dot matrix machines. A computer is used to generate different patterns using a set of algorithms. But the highest-quality holograms are available from electron-beam lithography. These holograms use highly sophisticated micro-optical systems to produce a resolution of 0.1 micrometers, which is equal to a phenomenal 254,000 dots per inch. Once again, unique computer algorithms are used to generate the design patterns.
Some of the features available via security holograms include:
Covert Laser Readable (CLR) Images: Available on holograms generated by dot matrix printers, a laser is used to verify that a hologram is authentic. Generating these images, which are either dynamic or multigrade, requires advanced computing power.
Kinetic Images: The appearance of movement when the angle of observation is changed.
Nanotexts: Tiny text smaller than 50 micrometers across can be embedded in holograms and can only be detected via a microscope.
Concealed Images: Very thin contours and lines that can only be observed at a particular, classified angle.
Guilloche Patterns: Intricate geometrical patterns at high resolutions and with different colors on each line.
Combination Effects: These combine nanotexts, concealed images, etc. with 2D or 3D images to form a very secure hologram.