How Do Holograms Work?

By Sarah Saltiel

We’ve all heard the word "hologram" before, but what exactly is it? A hologram is an image that looks like it's 3-D, but in actuality, is flat. In short, they’re a recording of reflected light. They’re used in security, product packaging, airplanes, and cars. They’re nearly impossible to counterfeit, so they’re popular in items requiring individuality. It all depends on the type of hologram.

Holography was first thought of in 1947 by Dennis Gabor. He was trying to improve the resolution of a microscope. He got the word from the Latin terms “holos” meaning whole, and “gramma” meaning message. Unfortunately, he did not get to expand on his idea because light technology was not very advanced. Holography wasn’t fully explored until the 1960’s when Russian scientists N. Bassov and A. Prokhorov created a laser. This was crucial to making holograms.

 Since the invention of the laser, hologram technology has improved considerably. The 3-D aspect has been added to it, as well being able to photograph living objects. Currently, thousands of labs have the equipment to make holograms and do indeed use them on a day-to-day basis. The technology was further added to when the splitting of white light was discovered, allowing holograms to be many different colors.

To make a hologram, you need a laser, lenses, a beam splitter, mirrors, and holographic film. Arrange it something like this:

The beam-splitter will cut the lasers light so it goes off into two directions. The mirrors will then direct the light so it goes in the intended directions. Then, the beams will go through lenses and become wider, as shown above. One beam will reflect off the object and onto the film. The other will hit the film and will not reflect off anything besides a mirror. Holographic film will record the light at a high resolution, causing there to be an image on the screen. A shutter opens or moves out of the path of a laser. (In some setups, a pulsed laser fires a single pulse of light, making it unnecessary to use a shutter.)

The light from the object beam reflects off of an object. The light from the reference beam goes past the object entirely. The light from both beams comes into contact with the photographic emulsion, where light-sensitive compounds react to it. The shutter closes,which in effect, blocks the light.

Copying a hologram can be extremely difficult, a reason that it is used in credit cards and such. But the problem is, to create a hologram, there can be absolutely no vibrations. The surface of the table must be completely still, same with the air. This makes it hard to produce, not only for the people trying to copy the hologram, but for the people originally making one.

Although the technology has come a long way, it still has a long way to go. Most holograms are still only one color. If people could mass produce holograms with many different colors, the possibilities could be endless. The holograms are currently also rather small. There are a few that are larger or multi-colored, so developers need discover how to successfully manufacture them in mass amounts. However, they should stay difficult to be counterfeited because they are a valuable resource for our nation’s security.

http://www.wisegeek.com/what-is-a-hologram.htm

http://science.howstuffworks.com/hologram1.htm

http://www.holography.ru/histeng.htm

http://www.holograms.bc.ca/faq.htm