|
|
|
| Sunday, 24 July 2005 |
 |
|
 |
Junior Observer |  |
| News Business Features Editorial
|
3-D images from holograms Have you ever heard about holograms? Well, a hologram is like a picture. A hologram is in 3-D. The “D” in “3-D” stands for “dimension”. The “3” in “3-D” stands for how many “dimensions” something has. A photo, even this piece of paper is 2-D, or two dimensional: up and down and left and right. When something is 3-D, like the world in which we live — or a hologram — it has an added dimension: up and down, left and right and forwards and backwards. When talking about dimensions, we call forwards and backwards “depth”. So, when we say that a hologram has three dimensions, it means we can see up and down, and left and right, just like a picture or photo, but we can also look “into” the hologram because the hologram, and the objects that it contains, have depth. Looking at certain types of holograms is just like looking at something that is really in front of your eyes. In fact, some holograms are so real that you want to touch the object in it — but your hand goes right through it. Have you ever watched an old movie on TV? Perhaps it was in black and white. Perhaps, looking at it was slow and boring. When you see something new on TV, it is usually made with the help of computers and is very fast and exciting. But everything gets old. Even those big-screen TVs that seem so hi-tech will one day be very boring. Why? Someday, everything we look at will be holographic images. One day in the future, 3-D holographic images will be sent into our homes and we will see all the action as if it is taking place right in our own living rooms. Then you might even laugh at the special effects you love in the present day movies. So, what are holograms used for? With holography, we can test all kinds of things . . . from automobile engines, to aircraft tyres, to artificial bones and joints. This type of holography is called “interferometry”, and the resulting hologram is called an “interferogram”. Holography is also used in medical imaging where doctors can look at a 3-dimensional CAT scan and actually go in and take measurements within the holographic image. Very simple (and colourful) holograms are used on consumer packaging materials such as cereal and toothpaste boxes, and a host of other items. Holograms are used for security for credit cards and for identifying manufactured objects such as clothing to help cut down on conterfeiting (faking). Holographic Optica Elements (HOE) are used by airplane pilots for navigation. It allows them to keep their eyes on the sky or runway, while still being able to read their instruments, which appear to float in front of their cockpit window. This feature is already available as an option on several automobiles. Holographic lenses and contacts can make one lens provide several different functions, such as correcting regular vision and acting as magnifiers for reading — all in the same lens, and throughout the entire lens, at the same time. Holograms can be made into portraits of people or pets. Artists use holography to express their creativity, displayed in galleries around the world. They are used in printing for magazine and book covers with. National Geographic and Sports Illustrated being famous examples. Holograms can be used for point-of-purchase advertising, taking the place of a photograph of a product or service in a store or supermarket. Holograms can be used for data storage, such as holographic hard drives. Would you believe that the entire contents of the US Library of Congress can be stored in an area, the size of a sugar cube? As the technology grows and develops, we will see holographic television and motion pictures as mentioned earlier. A true holograph is actually a special type of photograph. But there are some crucial differences. The main differences between a hologram and a standard camera shot are: 1. A high contrast, very fine grain (3000 lines/mm) photographic film is needed to record all the information. 2. The position of the film in the optical set-up is different. Rather than recording the virtual image of the object, a hologram records the diffraction (breaking up a beam of light into a series of coloured or dark and light bands) pattern of the object. 3. We need a reference beam to illuminate the film, usually by splitting the light into two paths. The reference beam provides a means to produce an interference pattern within the film. 4. The interference can only be created between two lightwaves which are in-phase. So, the object has to be illuminated by coherent light, rather than the incoherent light produced by the Sun or a lightbulb. Nowadays, this is achieved by a laser, giving single colour (monochromatic) images. More and more 3-D movies are being created with more cinemas being built all over the world. True moving holograms, which project a wide angle of stereoscopic information, without the need for any goggles are the ultimate aim. However, current animated 3-dimensional images are possible only by using expensive technology. It is the home market that will show how robust and cost-effective any future technology is. It is likely that any new animated 3-D system will be a personal computer peripheral. Television and home computers are currently merging. PC graphics cards that can receive TV format signals are available and DVD provides a common multimedia, for use in both computers and televideo systems. Therefore, 3-D television will surely emerge from a combined computer cum digital television, that uses the internet, DVD or cable or satellite digital television decoders as a source for the movie. One day, computer-generated holograms which allow us to see all aspects of the image, from any angle, will be commercially available. The research into moving holograms is progressing quickly, with small animated colour holograms capable of many frames a second being developed. Computer-generated interference patterns are produced directly in a regenerative medium, rather than relying on photosensitive film. Materials, whose optical properties are affected by acoustical or magnetic interactions, are used to modify a projected light beam. This is similar to the way LCD displays modify the light transmitting through them, using the liquid crystal molecules as a series of fine shutters. |
| News | Business | Features
| Editorial | Security
| Politics | Produced by Lake House |
