Explain the construction and reconstruction of hologram.

Holography technique to obtain 3D image of an object:  

1. Holography is the science and practice of making holograms. Holography is actually a  recording of interference pattern formed between two beams of coherent light coming from  the same source.

2. In this process,both the amplitude and phase components of a light wave are recorded on a  light sensitive medium such as a photographic plate. The recording is known as a hologram.

3. Holography requires an intense coherent light source.It became a practical proposition only  after the invention of LASERS.

4. Holography is a two step process.In the first step,recording of hologram is done where the  object is transformed into a photographic record and the second step is the reconstruction in  which the hologram is transformed into image.

Construction process : 

1.During the recording process we superimpose on the scattered wave emanating from the  object,the another coherent wave(called as reference beam) of the same wavelength.

2.These 2 waves interfere in the plane of recording medium and produce interference  fringes.This is the recording process of hologram.

Reconstruction process : 

1.The reproduction of the image from the hologram is known as reconstruction of the  hologram.

2.In this process,a wave identical to reference beam is used.

3.When the hologram is illuminated by the reconstruction wave,2waves are produced.

4.One wave appears to diverge from the object and provides the virtual image of the object.

5.The second wave converges to form the real image of the object.