A holographic print is a rendition of a hologram on a flat surface, producing 3-D (three-dimensional) effects when viewed. A holographic print differs from a traditional hologram in that the print does not require any special lighting arrangements to yield the 3-D effect. The viewer does not need any task-specific eyewear to view the image.
Holographic prints are extensively used for identification and security purposes. Credit cards, driver licenses, passports, and security badges commonly have small holographic prints embedded on their surfaces. Holographic prints work especially well in these applications because the image cannot be duplicated with a scanner or photocopier, and counterfeiting such an image has proven exceptionally difficult and expensive. Engineers and architects use large holographic prints to demonstrate or promote their projects in a more enhanced fashion than conventional photographs can do. In some situations, holographic prints can take the place of cumbersome video demonstrations.
See a demonstration of holographic prints:
Holographic printing cannot be done on ordinary paper. In order to facilitate the process, the paper or other printing surface must be coated with a layer of metal (usually aluminum or steel) or reflective plastic. The hologram is embossed into the shiny metal or plastic, forming a complicated, extremely detailed, pixelated image in relief. When viewed under a microscope, the metal or plastic surface seems to have hills, gullies, ridges, and valleys. These irregularities produce the 3-D effect by scattering reflected light and diffracting it into its constituent color wavelengths. The reflected waves interfere with each other in such a way as to give a vivid, realistic 3-D portrayal of perspective and parallax.
Small holographic prints, such as those found on identification documents and credit cards, can be produced at moderate cost. Large holographic prints, such as engineers might use, can range upwards of $3000 apiece.
Holographic printing should not be confused with lenticular printing, which involves a different format and can be done with simpler equipment.