Hologram

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					Agenda
Overview

Explanation of the different types of hologram

How they work

Applications of holograms in our lives today

How it can be used in the future
Overview
 Holography was discovered in 1947
 by Hungarian physicist Dennis Gabor
  But “Clean” 3-D images were only invented from
  the 1960s
How are they formed?
 Through holography

 As a recorded image of an object
What is holography?
 It is a technique that allows the light scattered
 from an object to be recorded and later
 reconstructed

 So that it appears as if the object is in the same
 position relative to the recording medium as it
 was when recorded.
What is a hologram?
 Holograms are photographic images that are
 three-dimensional and appear to have depth



 Works by creating an image composed of two
 superimposed 2-dimensional pictures of the
 same object seen from different reference points
Difference between hologram
and an photographic image
  Mainly the way an image is produced in both
  methods



  This difference in the mode of process makes a
  photograph two dimensional (2-D) image while a
  hologram three dimensional (3-D) images
A hologram image
 It cannot be produced by a single ray model.

 The image is produced by diffraction and
 interference through wave phenomena.
A photographic image
 Can be produced by a camera lens using a
 simple geometric or ray model for the behaviour
 of light
Types of hologram
Reflection hologram
 One of the most common type of hologram
How does it work?
How does it work?
 It requires the use of light of a single exact
 wavelength, so lasers must be used



 In reflection holograms, the kind of holography
 that can be viewed in normal light, two laser
 beams and a photographic plate are used to take
 an image of the object
How does it work?
 Both laser beams used in a holograph go
 through beam spreaders, which spread the laser
 light out like a flashlight. The coherence of the
 beam is lost, but it remains an exact wavelength
 One beam illuminates the object from the side.
 The other beam, known as a reference beam,
 travels through a photographic plate and hits the
 object head-on, similar to the way in which a
 conventional camera takes a 2-D image
How does it work?
 The reflecting light from the reference beam
 leaves an image, or hologram, on the
 photographic plate, but so does the light
 reflected by the object from the side beam. The
 result is a photographic plate that registers two
 images simultaneously, creating a hologram.
Transmission hologram
 Another major type of hologram present today
How does it work?
How does it work?
 The coherent light from the laser is split to form
 an object beam and a reference beam.

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

 This pattern (hologram) contains the information
 about the object which can then be viewed as a
 three dimensional image.
How to view it?
 The image is captured in the interference
 pattern on the film
  Can be reconstructed for viewing by shining the
  coherent light of a laser on the hologram


 The image will be seen as suspended in space
 behind the hologram
Properties of a hologram
 The images are true three-dimensional images,
 showing depth and parallax and continually
 changing in aspect with the viewing angle
Properties of a hologram

Any part of the hologram
contains the whole image
If you tear a hologram in half,
you can still see the whole image
in each piece. The same is true
with smaller and smaller pieces
Properties of a hologram
 The images are scalable. They can be made with
 one wavelength and viewed with another, with
 the possibility of magnification
Applications of
holography/hologram in life
 Data storage

 Security

 Holographic scanners

 Holographic interferometry

 Medical applications
Data storage
 A technique that can store information at high
 density inside crystals or photopolymers
Security
 Holograms are very difficult to forge because
 they are replicated from a master hologram
 which requires expensive, specialized and
 technologically advanced equipment



 Used widely in many currencies and credit cards
 etc
Holographic Scanners
 Used in post offices, larger shipping firms, and
 automated conveyor systems
    To determine the three-dimensional size of a
   package. They are often used in tandem
   with checkweighers to allow automated pre-
   packing of given volumes, such as a truck or pallet
   for bulk shipment of goods.
Holographic
interferometry
 Holographic interferometry is a technique which enables
 static and dynamic displacements of objects with optically
 rough surfaces to be measured to optical interferometric
 precision.
 It can also be used to detect optical path length variations
 in transparent media, which enables, for example, fluid
 flow to be visualised and analysed.
  It can also be used to generate contours representing the
 form of the surface.
 It has been widely used to measure stress, strain, and
 vibration in engineering structures.
Medical applications
 In dentistry
   Storing orthodontic study models that can be
   retrieved by a laser beam or a white light source
   for accurate 3D measurement
   Holograms can be employed as training aids in the
   disciplines of dental anatomy and operative
   dentistry
Medical applications
 In x-rays
    For the imaging of internal parts of the body and
   living biological specimens with very high
   resolution without the need for sample preparation
Future uses of hologram
 Computers and data storage

  Holography will facilitate the invention of powerful
  computing systems known as optical or photonic
  computers.
  Optical computers will use holograms in circuitry to
  enable parallel processing.
  Holograms also will replace disc drives, microfilm and
  even flash memory as a data recording medium due to
  holography's higher memory storage capacity.
Future uses of hologram
 Holographic projection
  In television
  Computers
  PDA’s
Bibliography
 http://en.wikipedia.org/wiki/Holography
 http://science.howstuffworks.com/hologram.htm
 http://hyperphysics.phy-
 astr.gsu.edu/hbase/optmod/holog.html
 http://www.martin-
 richardson.com/articles/articlePage.aspx?pageId=pa
 g0003&articleId=art0001
 http://web.mit.edu/museum/lightforest/holograms.ht
 ml

				
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posted:1/30/2012
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