Mechanism of holography, Laser uses in medicine, computers and military fields

Laser rays are used in different fields such as Holography, medicine, communication field, military field, industry field, computers field, surveying to determine dimensions and areas, space research, arts and laser shows.

Holography

The image of the body is formed by collecting the reflected rays on the body to be filmed on the photographic plate where the information is carried by the rays.

The 3D image: The photographic plate records all the information which are carried by the reflected rays from the surface of the body such as the difference in the optical intensity and the path difference of rays (which result due to the topography of the body) or difference in the phase of light waves ( (2π/λ) × The path difference ).

The photographic image: The sensitive photographic plate records only part of the information which is carried by the reflected rays from the surface of the body which is the difference in the optical intensity (which is proportional to the square of the amplitude).

The mechanism of holography

In 1948, a Hungarian scientist Gabor proposed a method to obtain the missing component from the information of the image and retrieve it from the beam:

1. Using a beam of parallel rays have the same wavelength of the rays which are reflected from the body to be hologramed and is called the reference beam.
2. A laser beam is split into two beams, one is used to illuminate the object and the other is used as the reference beam, the reflected beam and the reference beam meet at the photographic plate.
3. An interference occurs and after the photographic plate is developed, the resulting interference fringes appear coded and we call such an image a hologram.
4. By illuminating the hologram with a laser of the same wavelength and looking through the hologram with the naked eye, we see an identical 3D image of the object without using any lenses.

Reference beams are parallel rays used in holography and have the same wavelength of the reflected rays from the body, Hologram is a coded image formed due to the interference of the reference rays with the reflected rays from the body and appears in the form of fringes after the developing of the photographic plate.

The used rays in holography must be coherent to obtain interference model and this can be achieved only by using laser, Using lasers many images can be stored on hologram and 3D images of moving bodies can also be obtained.

Laser in medicine

Laser rays are used with optical fibers for diagnoses and treatment by endoscopy and also it is used in ophthalmology.

1. To treat the retinal detachment: When a part of the retina separates from the layer underneath, it loses its function, unless quickly treated, the eye may lose sight completely, The eye may be treated by reconnecting the detached part with the layer underneath and this operation takes less time and effort than before, the thermal heat from the laser cauterizes the points of detachment (endothermic).
2. Lasers are also used to treat cases of long and short-sightedness, So the patient can dispose of glasses.
   
3. Lasers are used in endoscopy using optical fibers in operative surgery and diagnosis.

Communication field

Laser rays are used in communication with optical fibers instead of telephone cables.

Military fields 

Laser rays are used in rocket guidance with high accuracy and in smart bombs and laser radar (LADAR) in what is known as Star Wars, where lasers are used to destroy missiles and planes in space after lunch directly.

Industry field

Some types of laser generate enough energy for melting metals, for example, you can focus laser light to vaporize liquified iron and some laser generate enough to make a hole in the diamond.

Computers field

Laser rays are used in recording on CDs (Laser CDs), They are used in the laser printer, where the laser beam is used to transfer information from the computer to the disc by the photosensitive material then printing on paper using ink.

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