Leow S.T. Aloysius 3O3 (15)

Ever saw a Star Wars movie and wondered what is that green 3-D image of Yoda?

This image is actually a hologram.

Holography was invented in 1947 by Hungarian physicist Dennis Gabor

Did not really advance until the invention of LASER in 1960

He received the Nobel Prize in physics in 1971

It is the process by which three-dimensional pictures can be stored and reproduced by laser light.

A hologram is therefore a record of an image as seen from many viewpoints.

What happens when a photo is taken:1) The shutter opens.2) Light passes through a lens and hits the photographic emulsion on a piece of film.3) Silver halide reacts with the light and records its amplitude as it reflects off of the scene4) The shutter closes

It is a point-to-point recording of the intensity of light rays that make up an image

Each point on the photograph records just the intensity of the light wave that illuminates that particular point.

When we develop the film and make a print of the picture, our brain interprets the light that reflects from the picture as a representation of the original image.

The wavelength affects the wave’s frequency.

This determines its color and is measured in cycles per second, or Hertz (Hz)

White light: Contains different

wavelengths traveling in different directions and different phase

LASER light: Monochromatic ( has one

wavelength and one color) Waves are in phase

White light can be used to make or view photographs but a hologram requires the organized light of a LASER

Holograms record differences in both amplitude and the phase

The light has to start out with one wavelength and one phase in order for the film to record these difference.

1) Light from the LASER is split to form object beam and reference beam.

2) Light from the object beam reflects off the object.

3)  The light from the object and the reference beam form an interference pattern on the film.

Shine the light of a LASER on the hologram, in the same orientation as the reference beam

Because both the phase and intensity are reproduced, the image appears three-dimensional

The eye is focused behind the film to see the image suspended in space.

Things you need:1) A LASER: Helium-Neon (HeNe) lasers are

common in holography2) Diverging Lenses3) A beam splitter: Uses mirrors and prisms

to spread a beam into two4) Mirrors: To direct the beams of light to the

correct location5) Holographic film: To record light at high

resolution

1) The laser points at the beam splitter, dividing the beam into two.

2) Mirrors are used to direct the beams to intended targets (eg. Make sure the object beam hits the object).

3) The two beams pass through diverging lenses and becomes a wide swath of light.

4) The object beam reflects off the object, onto the holographic film.

5) The reference beam hits the holographic film without reflecting off anything but the mirror.

A humorous video on the applications of holograms.

Holography

Security

Display

Medical

And many more…

The presence of holograms indicates the authenticity of these items

Security holograms are also being used in anti-counterfeiting, identification documents, including credit and phone cards, drivers licenses etc

Various Hollywood movies, specially the science fiction films, have used holographic special effects. (eg. Star Wars, Star Trek)

Holograms are also used as promotional tools on records and CD covers.

Holographic technique is also used in various medical applications. (eg. CAT scans, X-ray, MRI, Ultrasound)

http://science.howstuffworks.com/hologram.htm http://www.fact-index.com/h/ho/holography.html http://hyperphysics.phy-astr.gsu.edu/hbase/opt

mod/holog2.html http://www.holo.com/holo//book/book.html#thho

lo http://www.holoworld.com/holo/kids.html http://www.hololight.net/holography.html http://www.holography.ru/maineng.htm http://www.holography.co.uk/questions/

holuses.htm http://www.wikipedia.org http://www.google.com http://www.hologramsuppliers.com/holograms-

applications.html http://silver.neep.wisc.edu/~lakes/hoAppl.html

Any questions?