Holography

Do you have a license, credit card, or any official merchandise such as authentic sports memorabilia? Do you own a CD or DVD? Do you know what all of these everyday items have in common and why they are important? Well, a common factor in all of these items is holography. A license, credit card, and official merchandise include holograms to show authenticity and protect against fraud. However, these examples of holography are not superb in quality because they appear more shiny than in three dimension. What is holography? Well, pay attention and you'll find out!

Holography has been defined as "a method of creating a three-dimensional image of an object on film by encoding not just the intensity but also the phase information of the light striking the film" by the American Heritage Science Dictionary. The theory of holography was developed by Dennis Gabor. He developed this theory while he was trying to improve electron microscopes. The word hologram is derived from the Greek words holos and gramma, which means "whole message". In the time of Gabor, holography was much simpler. Holography involved film transparencies and a mercury arc lamp, which caused the holograms to be semi-distorted and an "extraneous twin image". The invention of the laser in 1960 was the ideal tool to create better holograms. How do holograms work?

Well, holograms can be made with very few tools. The essential tools include a laser, lenses, a beam splitter, mirrors, and holographic film. Commonly, helium-neon lasers or "red lasers" are used in making holograms. Some holography experiments have relied on laser pointers, but this results in less coherent and less stable holograms. Certain lasers require a shutter to control exposure. Holography is commonly mislabeled as the "lens less photography", but lenses are required. On the contrary to camera lenses, holography lenses cause the beam to spread out. A beam splitter and mirrors are rather self-explanatory tools. Holographic film is different than photographic film because it must be able to record extremely small changes of light taking place over microscopic distances. This film must have a very fine grain and some holographic film responds only to red light lasers. Below demonstrates a basic transmission hologram setup.

One form of holography as mentioned above is transmission holography. A typical transmission hologram is viewed with laser light. It often uses the same type of laser used in making recordings. The virtual image created in a transmission hologram is very sharp and deep. An example given is "through a small hologram, a full-size room with people in it can be seen as if the hologram were a window". When the hologram is broken, a person can still see the entire "scene" in each piece of the hologram. There is one other main type of hologram and one mixed hologram type.

The other main type of hologram is a reflection hologram. This is considered the most common type of hologram displayed in galleries. It is a "truly three-dimensional image which is seen near its surface". The hologram is "illuminated by a spot of white incandescent light". This light is placed at specific angles and distances and on the "viewer's side". Therefore, the image is formed with light reflected by the hologram. The next type of hologram is not considered a main type, but is also very important.

Hybrid holograms are very important to holography. These holograms are variations formed from reflection and transmission types of holograms. There are different forms of hybrid holograms. The most common types of hybrid holograms include embossed, integral, holographic interferometry, multichannel, and computer-generated holograms. Embossed holograms are mass produced, inexpensive holograms used for security reasons like credit cards. This is when a "two-dimensional interference pattern is pressed onto thin plastic foils". Integral holograms are important to medical holography. Computer-generated holograms will become very important in the future and use the mathematics of holography.

Holography is growing increasingly important and is rapidly changing due to technology. Holography is often used for security purposes or CD and DVD technology. Holography also has an important role in medicine today. Imaging through tissues, ophthalmology, dentistry, urology, ontology, pathology, and orthopedics all show "strong premises" for holography to become even more important to the medical community. The possibilities for medical holography seem almost endless and will most likely continue to grow in the next decade. Other holography that makes a medical difference is X-ray and multiplexed holography. Both allow doctors or scientists to examine samples without damaging the patient. How will holography continue to grow in the future?

In the future, holography will play an even more important role. There has been much speculation about having holograms affect the advertisement industry. This would occur by having animated billboards. One example of these animated billboards would be a woman with a can of Coca Cola, who takes a sip of it and offers it to you. This would create a whole new industry and countless jobs. Also, it is rumored that holography principles could be applied to video games. That would make the demand for video game programmers, designers, and many other jobs in that industry even higher. I wonder what else people will be able to use holography for in the future. Holography is a very unique and interesting form of photography that has highly valuable uses and will only continue to become more involved in our lives over the next couple of decades!