Holographic cards are hard pieces of cardboard and papers that have shiny, metallic images on them. Sometimes the images can move and even change into other images when the cards are repositioned and turned toward certain angles. In other cases, the images do not change, but appear three-dimensional, moving and turning in different angles and looking like they float just above the card. Holographic cards are also usually colorful, with the colors slightly changing if the card is moved from side to side. One can think of a holographic card as an updated version of a photograph that only captures an image in 2D.
The concept of holograms can be likened to how the eyes see three-dimensional images. The left eye sees an image in one angle, while the right eye sees the image in another angle. When the brain receives these images, it combines them and turns them into one 3D image. When the person shifts at another angle, the brain does the same process and presents the image in another perspective. Holographic cards operate in similar methods in that they record several angles on paper, hence the 3D effects of the images.
Capturing images on holographic cards can require certain tools such as the holographic film, a red laser, mirrors, lenses, and a half-mirror, which is a glass with a coating of silver on half of its surface. The red laser is aimed at the half-mirror, making half of the light beam pass through the glass, and the other half is then reflected to another mirror due to the silver coating. The reflected half-beam is again reflected to another mirror, which then angles the said half-beam to hit directly at the object. The half-beam then bounces from the object towards the holographic film.
The other half-beam that passed through the half-mirror is also reflected by another mirror, which then angles the beam towards the holographic film as well. The image on holographic cards is finally created when both the half-beams hit the holographic film, producing the 3D image. In this way, both the half-beams somehow act similarly as the eyes, seeing the image in different angles through several mirrors.
To create clear images on the holographic cards, it is best to do the whole process in a very dark room. All the tools should also be placed on a flat surface and must remain unmoved; even the slightest vibration from a footstep or breathing can possibly distort the image on the card. Many holography studios have customized tables that contain absorbers underneath to reduce vibration.
Holographic cards have much usage, particularly for security reasons. Companies and organizations issue holographic identification cards that are hard to copy by counterfeiters. The hologram process can even place some data that only computers can read, keeping private information as such.