Hologram

September 8, 2011 by · Leave a Comment 

tufail holoHOLOGRAPHY is the process of recording a three-dimensional image of an object using the special properties of light from a LASER. Unlike photography, which only records the brightness and contrast of an object, a HOLOGRAM records brightness, contrast and DIMENSION. This allows holography to display the final image in true 3D.

You do not need any special glasses to view a hologram. Although the hologram is most famous for 3D images, holograms can also be of a 2D image as well. What both share in common is that they were created through the use of a LASER.

The first hologram was conceived of, and produced in 1948 by Dr. Dennis Gabor, a researcher at the Imperial College of London. For his theories and work, he received the Nobel Prize in physics in 1971. Gabor’s early holograms were created without the use of a laser, since the laser wasn’t invented until 1960. Therefore his holograms were only capable of showing the slightest amount of depth (about the thickness of a postage stamp). His light-producing instrument was a mercury-vapor lamp.

With the invention of the laser in 1960, researchers had the proper type of light to begin recording an object dimensionally. Emmett Leith and Juris Upatnieks in the United States (University of Michigan), along with Yuri Denisyuk in the former Soviet Union, all familiar with the work of Gabor, applied this special new light of the laser to produce the first practical holograms.

These early holograms required a laser to both record and view the image. It wasn’t long however, before new techniques allowed the hologram, although still requiring a laser to record, to be viewed with ordinary light (such as a light bulb). Also, many different types of holograms were developed, each with their own technique used to produce them.

The excitement of viewing a hologram is only exceeded by the thrill of actually making one. Today, in 2011, it is fairly easy to make small holograms using inexpensive and easy-to-find equipment. Students from elementary school to high school are making holograms. The expensive lasers of the past have been replaced by the inexpensive laser pointers of today.

Holograms are made in laser laboratories, but they are also made in homes and schools every day. There are a few important things that need to be done before you can make a hologram, but none of those things are very hard to do. To give one example, a hologram must be made in a very quiet and darkened room. That’s not too difficult, right? We can’t give the full directions to make a hologram here, but we can say that simple holograms are made using a laser, a lens, and a recording medium, such as a light-sensitive film or glass plate.

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Holograms

January 28, 2010 by · Leave a Comment 

tufail only - adil

A hologram is a flat surface that, under proper illumination, appears to contain a three-dimensional image. A hologram may also project a three-dimensional image into the air—a lifelike image that can be photographed although it cannot be touched. Because they cannot be copied by ordinary means, holograms are widely used to prevent counterfeiting of documents such as credit cards, driver’s licenses, and admission tickets. The word hologram comes from the Greek roots holos meaning whole and gramma meaning message. The process of making a hologram is called holography. When a hologram is made, light from a laser records an image of the desired object on film or a photographic plate.

There are basically two types of holograms. A reflection hologram is viewed when lit from the front, while a transmission hologram is viewed by shining a light through it from the back side. An embossed hologram is made by backing a transmission hologram with a mirror-like substance, which allows it to be viewed when lit from the front. Holograms can also be made that show moving objects; these sequences, called stereograms, are typically three to 20 seconds long.

Although a hologram is a visual image of a physical object, it is quite different from a photograph. For instance, when an object is photographed, each portion of the photo contains an image of the corresponding portion of the original object. Each section of a hologram, however, contains a complete image of the original object, viewed from a vantage point that corresponds to the section’s position on the hologram. Thus, if the transparent plate containing a transmission hologram is broken, each piece will still be able to project the entire image, albeit from a different point of view. Using a piece from near the top of the holographic plate will produce an image as seen from above, while using a piece from near the bottom of the plate will create the impression of looking upward toward the object.

Another interesting property of holograms is that they preserve the optical properties of objects such as lenses. For instance, consider making a hologram of a magnifying glass placed in front of a butterfly. When viewing the holographic image of those objects, an observer will find that the portions of the butterfly seen through the image of the magnifying glass will be enlarged.

Holographic packaging has been shown to increase the sales of certain products. Projection holograms are especially eye-catching and are used at trade shows and retail stores. They can be used to display extremely delicate or valuable objects. A classic example was an image of a diamond-adorned hand that was projected over the sidewalk outside the Cartier jewelry store in New York City in 1970. Not only did it catch the attention of people walking by it, it attracted television news crews. In fact, it was even attacked by an umbrella-wielding pedestrian who thought it was the “work of the devil.” In another instance, rather than repeatedly handling the fragile skull of the 2,300 year old Lindow Man, researchers studied its holographic image. Scotland Yard’s Forensic Science Department used this holographic image to construct a physical model of the remains of the prehistoric man. As yet another application of holography, former Chicago Bears football coach Mike Ditka displayed a holographic portrait of himself in his restaurant to create a somewhat personal image when he could not be there in person.

Holograms can be made at home by hobbyists for a modest investment in equipment. The process requires a laser and an isolation table to prevent movement of the equipment while the film is being exposed. Holograms are also produced commercially and can be reproduced in large quantities. Using stock artwork, a master hologram for mass production can be created for as little as $2,500, whereas using custom artwork can cost $5,000 to $10,000. Reproducing the image costs from 1 to 4 cents per inch (2.5 cm), depending on the volume; this represents a 40% decrease since embossed holograms were first marketed in the late 1970s. Finished holograms can be attached to other objects as pressure-sensitive labels (0.5 to 1.5 cents each) or by hot stamping (2 to 5 cents each). Once the artwork is finalized, it takes about three months to create and reproduce a batch of commercial holograms. It is estimated that more than $200 million worth of embossed holograms were manufactured in 1995.

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