Diffraction of light and Holograms

1. Definition of diffraction of light• Diffraction of light is the bending of light waves around an object. The amount of light diffracted

or which changes direction is dependent on an object's size. This also applies to light waves that pass through an opening, such as the aperture of a camera or through the pupil of an eye. As light waves pass around the edge of an object or through an opening, light is diffracted or broken into the colors of the rainbow.

Characteristics of diffraction of light• Diffraction of light occurs when a light wave passes by a corner or

through an opening or slit that is physically the approximate size of, or even smaller than that light's wavelength.• If the two are closer in size or equal, the amount of bending is

considerable, and easily seen with the naked eye.

• Diffraction occurs with all waves, including sound waves, water waves, and electronic waves such as visible light, X-rays and radio waves• Diffraction not only occurs in small slits or holes but in every case

where light waves bend round a corner.

2. What’s about hologram?• Hologram is a photographic record produced by illuminating the object with

coherent light (as from a laser) and, without using lenses, exposing a film to light reflected from this object and to a direct beam of coherent light. When interference patterns on the film are illuminated by the coherent light a three-dimensional image is produced

Doubled-slit diffraction:

Single-slit diffraction:

Some images for hologram

3. Application of hologram• Security: The use of holograms on credit cards and bank-notes has reduced the opportunity for

forgery• Interferometry: If a "double exposure" hologram is made of an object before and after the object

is subjected to stress, the change in the shape of the object due to that stress is recorded as a series of light and dark bands. In industrial situations this can be used in component testing and quality control.

• Medical records: Medical, dental and other records can be made both for teaching and for documentation.

• Measurements: Particle physicists make holographic records of bubble-chambers from which accurate measurements can be made.

• Display of artifacts: Many museums have made holograms of valuable articles in their collections, both for insurance purposes and to check for deterioration. In the former Soviet Union exhibitions of holograms of national treasures were sent to remote areas, enabling people to see and appreciate their national heritage without the necessity of travelling to major museums in Moscow or Leningrad

Transparent Hologram ID Card Overlay:

Holograms are an advanced technology that can recreate 3D objects in midair. One can find information about holograms by just entering the key word: holograms in the search box of any browsers. Advantages and Disadvantages are listed below.

Advantages:

• Cost effective• Higher storage capacity• Increased feasibility of objects (depth)• Enables the achievement of multiple images on a single plate and 3D

images• Ability to combine with other technologies

Disadvantages:

• Provide static images• Do not produce images of complex movement• Require complicated precise machinery to produce and view an image• Low axial resolution of inline holography• Reference illumination beams are collinear