The Engineering Behind Laser Holography And Working Process:
In the Gabor original hologram model hologram was a record of the interference between the light diffracted by the object and a collinear background. The main problem with this model was creating three-dimensional realism in photographs. To solve this issue it is necessary that the light emitting from the source must itself be photographed. If the waves of the streaming light, with their multiple amplitudes of fast-moving crests and troughs, can be stopped or frozen for a movement and photographed, the wave pattern can then be reconstructed and will exhibit the same three-dimensional (3D) pictures as the object from which the light is reflected. The Holography accomplishes such a reconstruction by recording the phase and amplitude content of the reflected light waves of the light source. This light source is a LASER. The coherent and monochromatic nature of LASER light makes it useful for holography.
There are multiple processes to make a hologram of any object by using LASER light. Some of them are given below:
Continuous-wave laser holography:
This method uses a continuous wave laser system such as a helium-neon gas laser. After proper arrangements of optics to create an image and reference beam (for creating 3D view), an exposure time is required to allow for the interference pattern to create fringes. The continuous-wave laser method has a stability problem, however, it can be handled by using proper optical arrangement. To properly render the information in the hologram, the correct intensity must be allocated to the reference and object beams respectively which depends on viewing methods.
Gas lasers such as Argon-ion and Krypton-ion may also be used. The advantage of using Argon-ion laser is that green and blue coherent light can be produced at higher whereas Krypton-ion gas laser spans the whole visible spectrum range (from red to blue) and can also produce coherent beams outside visible wavelengths.
Pulsed laser holography:
This is another method of laser holography. The laser system available for the production of the hologram is a pulsed-ruby laser. The pulse duration can be less than 10-7 seconds; and, as long as the object does not move more than 1/10 of a wavelength of light during this short time interval, a usable hologram can be obtained. This method is useful for creating slow-motion holograms. The optical arrangements for specific types of holograms are essentially the same as with a continuous wave laser however special optical equipment needed to be used due to the presence of higher energy laser beams.