Holography

For recording derivation just go through LASERS book by Milloni. It is very easy and useful derivation. Thank you.

1. HOLOGRAPHY Submitted by: Shadab Siddiqui M. Tech (LEOC) Defence Institute of Advanced Technology Pune 411025

2. What is Holography? The term Hologram was coined from the Greek words holos , meaning “whole” and Gramma meaning “Message”. It is an advanced form of photography that allows an image to be recorded in three dimensions. The technique of holography can also be used to optically store, retrieve, and process information. The object is transformed into a photographic record. A method of obtaining three-dimensional photographic images. These images are obtained without a lens, so the method is also called lensless photography. The records are called holograms. A Holographic Image is created using a coherent light source to create an interference pattern on a film or plate.

3. History: Dennis Gabor : Father of Holography and Holographic technologies Dennis wrote a paper in 1948 for use in electron microscopy. The most interesting thing about all this is, when he wrote his paper the laser light had not even been invented yet Gabor received Nobel Prize in 1971 Leith and Upatneiks in 1962 applied laser light to holography and introduced an important off-axis technique.

4. Conventional Photography 2D version of 3D scene Photograph lacks depth perception or parallax Film sensitive only to radiant energy Phase relation i.e interference are lost Holographic Photography Freezes the intricate wavefront of light that carries all the visual information of the scene. To view the hologram wavefront is reconstructed, Using Hologram original scene can be viewed. Provide depth perception and parallax. While standard photography records colour and intensity information, a hologram encodes phase and intensity.

5. Hologram Properties: If you look at the holograms from different angles, you see objects from different perspectives, just like you would if you were looking at a real object If you cut one in half, each half contains whole views of the entire holographic images.

6. Formation of a hologram The basic technique of holograph formation is to divide the coherent light coming from a laser into two beams: one to illustrate a subject and one to act as a reference.

7. Basic Practical setup:

8. Construction:

9. Construction: Laser: Red Laser, usually He-Ne Laser are common in holography Beam Splitter: This is a device that uses mirrors and prism to split one beam of light into two beams. Mirrors: use to direct the beams of light to the correct locations. Holographic Films: Records light at a very high resolution, which is necessary for creating a hologram. It’s a layer of light sensitive compounds on a transparent surface, like photographic film.

10. Reconstruction of Hologram:

11. Types of HOLOGRAM: Transmission Hologram Use 2 beam for create interference Reference and object waves traverse the film from the same side Produce interference fringes in planes that are perpendicular to the plane of the emulsion. Reflection Hologram Place the film between light source and object Reference and object waves traverse the emulsion from opposite sides Produce interference fringes in planes that are parallel to the plane of the emulsion.

12. The fundamental difference between a transmission hologram and a reflection hologram lies in the direction of the interference fringes that are recorded inside the photosensitive emulsion.

13. Advantages : Cost effective Higher storage capacity Increased feasibility of objects(depth) Enables the achievement of multiple images on a single plate Ability to Combine with other technology

14. Drawback: Do not produce images of complex movement Require complicated precise machinery to produce and view an images Low axial resolution of inline holography Reference illumination beams are collinear

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