Holograms and Optical Variable Devices
Holograms are classified into different types with reference to the degree of level of optical security incorporated in them during the process of master origination. The different classifications are described below:
2D / 3D hologram
These are by far the most common type of hologram preferred by customers. These holograms (and therefore the artwork of these holograms) may be of two layers (i.e. with a background and a foreground) or three – layers (with a background, a middle ground and a foreground). The matter of the middle ground in the case of the two - layer holograms are usually superimposed over the matter of the background of the hologram. These holograms display a unique multilevel, multi-colour effect. These images have one or two levels of flat graphics “floating” above or at the surface of the hologram. The matter in the background appears to be “under” or “behind” the hologram, giving the illusion of depth.
Apart from being the most cost-effective type of hologram the 2D / 3D Hologram, when viewed under a variety of sources of light, is found by many to be extremely eye–catching.
Dot matrix
The hologram produced using Dot Matrix technology are considered to be the most secured hologram internationally. These holograms are originated using highly sophisticated and very expensive Dot Matrix System. This kind of technology allows creating of originals of holograms with a resolution of up to 10 micrometres. Dot Matrix technology makes it possible to create originals of computer synthesized holograms with high level of protection. The hologram includes elements that cannot be manufactured using other optical or printing technologies. This technique requires development of various algorithms for designing optical elements that shapes scattered radiation patterns. The various kinds of features possible in this type of origination are mentioned below:
Concealed Images
They usually have the form of very thin lines and contours. Concealed images can be seen at large angle light diffraction and at one particular angle only.
Guilloche Pattern (High Resolution Line Patterns)
These are sets of thin lines of a complicated geometry (Guilloche Patterns) drawn with high resolution. The technology allows continuous visual changes of colour along each separated lines.
Kinetic images
They can be seen when the conditions of hologram observations are being changed. Turning or inclining the OVD allows the movements of certain features of the image to be studied.
Microtexts or nanotexts
Dot Matrix Technologies allows implanting into hologram microtext of various sizes. There are three types of microtexts in holograms: high contrast microtexts of size 50 – 150 micrometres; diffractive grating filled microtexts of size 50 – 150 micrometres low contrast microtexts. To distinguish microtexts of sizes smaller than 50 micrometres, it is called nanotext. Nanotexts with sizes of less than 50 micrometres can be observed with a microscope only.
CLR (Covert Laser Readable) image
This feature permits one to use a simple laser device to control the authenticity of the hologram. Computing CLR images is a complicated mathematical task that involves solving ill-posed problems. This feature is only possible in hologram originated with Dot Matrix technology. There are two types of CLR which we can offer. Firstly, Dynamic CLR is a set of CLR fragments that produce animated images on the screen as the control device moves along the hologram surface. Secondly, Multigrade CLR images produce certain images on the screen of the controlling device, which differ in the first and minus first orders of laser light diffraction. As a variant we can create a hidden image which is negative and positive in plus one and minus one order respectively.
Computer Synthesized 2D/3D and 3D images
Using this technology we can also allow 2D / 3D images to be combined with other security features (microtexts, concealed images, CLR etc.) this combination effect cannot be achieved using any other traditional technologies of origination.
True colour images
True colour images are very effective decorative pictures. If combined with microtexts and hidden images, true colour yields high security holograms.
This origination technique offers manifold possibilities for combining various security features. The technology of computer synthesis of holograms opens ample opportunity for the creation of OVD with highest level of security.
E-BEAM & 12,000 dpi
These types of hologram are originated using highly sophisticated and very expensive e-beam lithography system and this is the latest technology in the world at present. This kind of technology allows the creation of originals of holograms with a resolution of up to 0.1 micrometres. E-beam technology makes it possible to create originals of computer synthesized holograms with high level of protection. The holograms include elements that cannot be manufactured using other optical or printing technologies. This technique requires development of various algorithms for designing optical elements that shapes scattered radiation patterns. This type of hologram offers features like the viewing of four lasers at a single point, 2D/3D raster text, Mini Switch Effect, Four Channel, Pure 3D effect, Concealed Images, True Colour Images. Some of the other various kinds of features possible in this type of origination are mentioned below:
White gradient
Generally in holography different colour appears but this is a special effect i.e. in holography white colour can be shooted.
High Resolution Line Pattern
These are sets of thin lines of a complicated geometry (guilloche patterns) drawn with high resolution. The technology allows continuous visual changes of colour along each separate line.
Kinetic images
They can be seen when the conditions of holograms observations are being changed. Turning or inclining the OVD allows the movements of certain features of the image to be studied.
Microtexts or nanotexts
E-beam technologies allow implanting into hologram microtext of various sizes. There are three types of microtext in holograms: high contrast microtext of size 20 – 150 micrometres; diffraction grating filled microtext of size 40 - 150 micrometres; 40 – 150 micrometre low contrast microtext. To distinguish microtext of sizes smaller than 10 micrometres, it is called nanotext. Nanotexts with sizes of less than 10 micrometres can be observed with an electron microscope only.
CLR (Covert Laser Readable) image
This feature permits one to use a simple laser device to control the authenticity of the hologram. Computing CLR images is a complicated mathematical task that involves solving ill-posed problems. This feature is only possible in holograms originated with e-beam technology. There are two type of CLR which we can offer: Firstly, Dynamic CLR is a set of CLR fragments that produce animated images on the screen as the control device moves along the hologram surface. Secondly, Multigrade CLR images (2 Channel CLR images): Multigrade CLR images produce certain images on the screen of the controlling device, which differ in the first and minus first orders of laser light diffraction. As a variant we can create a hidden image, which is negative and positive in plus one and minus one order respectively.
Computer Synthesized 2D-3D and 3D images
Using this technology we can also allow 2D / 3D images to be combined with other security features (microtexts, concealed images, CLR, etc). This combination effect cannot be achieved using any other traditional technologies of origination.
Raster text / image raster
Texts are hidden text which can be viewed with the help of a specialized film only. The text is hidden and invisible to the naked eye.
This origination technique offers manifold possibilities for combining various security features. The technology of computer synthesis of holograms opens ample opportunities for the creation of OVD with highest level of security.