/ / What is Hologram?

What is Hologram?

The recording and reconstruction of Light Waves on a photographic plate through the means of coherent light source, commonly considered to be lasers…

Hologram

Science has been developing for a while with a ton of applications as well as use cases ranging from global development of future innovative technology.

Hologram: An Overview

We are often familiar with the concept of recording a voice that can be playable later but here’s a concept of recording of light. In simple language, the concept of Hologram works by recording and mapping light illuminated objects that can be later reconstructed and played.

It all started in the 1940s when a Hungarian physicist Dennis Gabor found a strange incident (later named Hologram) that led him towards winning the Nobel Prize in Physics (1971). However, the development of the same was triggered with the discovery of laser beams in the 1960s. Today, we often witness a holographic image with the help of laser beams.

Holography is the process of production of Hologram or Holographic images. The word ‘holography’ came from the Greek word holos meaning whole (since the interference contained both amplitude and phase) and graphē meaning writing or drawing. Unlike projectors producing 2D imagery, structures produced from Holography (i.e. Hologram) have three-dimensional images and can be easily viewed from any angle.

The hologram may be said to superimposition a second wavefront, thereby generating an interference pattern later recorded on a medium. Today, two wavefronts are modeled digitally and reconstructed accordingly to obtain the required holographic imagery (computer-generated). In the early days, Holograms were expensive, since they involved emulsions that were ineffective and needed a high-power supply to operate but were easily absorbed. However, with the years going on, we have successfully invented a more efficient way that can operate in a comparatively low power supply with a high-efficiency rate. Holographics imagery or Holograms are constantly finding their applications with time, some of them involve use in Electron microscopes, etc.

How does a Hologram work?

A hologram is generally the game of lighting i.e. coherent light. The working of the hologram works in two steps i.e. recording and reconstructing the imagery. However, we can obtain various holographic images using different setups and constituents, but we would consider them the easiest to understand here.

Recording a Hologram

The most integral part of holographic production is recording the same for utilization. Laser, in general, is considered the best for recording an object due to its high intensity and coherent nature. 

Firstly, a coherent light beam i.e. laser is passed through a beamsplitter (a partially silvered glass that reflects a percentage of incident light and transmits rest) which splits the incoming light beam towards object and mirror respectively. On the one hand, the mirror (kept at an angle of 45°) then reflects the same towards the photographic plate. However, on the other hand, light from an object is also reflected towards the photographic plate where it is intersected with the reference beam (light reflected from the mirror) and is illuminated. The illuminated light then leaves a microscopic imprint of the object upon the photographic plates that are then left for the reconstruction of the hologram.

Reconstruction of Hologram

In comparison to the above recording part, where mirrors were needed to be placed at a fixed angle for proper recording of the subject, reconstruction of the holographic images needs photographic plates to be kept at a requisite angle. In general, any laser beam identical to the reference beam (reflected beam from mirror during the recording of the object) can trigger the reconstruction of a virtual object or the required holographic image that completely matches the recorded object. 

Unlike the above exact matching hologram which was obtained through a dark-fringe interference, the speckled interference pattern can also produce holographic images. When a different laser beam than the reference beam hits the photographic plates, it can produce Holograms. However, the hologram formed in this case would be a bit artificial or won’t match the original object completely.

A holographic technique may be used to detect the changes in any object with time by viewing it from different angles.

Types of Hologram

Reflection and Transmission Hologram are the two major well-known types of Holographic Imagery or Holograms.

Reflection Hologram

These are a special type of holograms that can be easily viewed through sunlight or white light without any involvement of laser light. When an incandescent ray illuminates, it hits the Hologram at a certain angle from the viewer’s side or camera’s end. The ray is then reflected from the Hologram towards the viewer thereby obtaining a 3D image. This type of holographic imagery is best viewed with a directional source of light (polarised light source) than a non-directional source of light (unpolarized light source). However, the same can be viewed with a non-directional light source but then the 3-dimensional image fades its clarity rather than being deep.

As discussed earlier, the reflection holograms have light sources from either direction of the viewer being reflected the same direction. The recorded fringe in reflection holograms is almost similar to that of transmission holograms, i.e., laser-formed holograms but parallel to film. Due to the same, most of the wavelengths are filtered out or simply diffracted, hence the non-diffracted wavelengths can easily pass through them to appear in the holograms, white being non-diffracted can easily and clearly replay images.

Reflection Holograms can no doubt be used for monitoring long-term changes for various compositions. It can also be utilized to measure the deformation of the platen in compression testing machines. The holographic technique can be super helpful in studying the deformation of the aluminum sheets over time.

Transmission Hologram

The most commonly and widely used holographic technique uses laser beams to reconstruct holographic imageries. This type of hologram uses laser but it can easily work if any quasi-monochromatic source of light is used.

Recording a hologram needs correct interference patterns and alignment to be correctly viewed. Therefore needing a lot of polarised light sources or monochromatic light (lasers are taken into consideration). Unlike Reflection Hologram, which can illuminate or be viewed even with an unpolarized light i.e. sunlight. This type of holography has object and reference beams incident on the same side resulting in the formation of the final object behind the film and when they’re reconstructed using a polarised point light source, they form a highly sharp and contrasting object. Their Holograms can easily be converted to reflection holograms with a simple tweak in geometry as well as chemistry. 

These are the most commonly used holographic technology to date that is expected to deliver the most of the benefits of the complete holographic technology. With better and efficient data storage and encryption as well as various uses in the field of art for showpieces at various locations namely Museums, etc. 

Applications of Hologram

Holography is not a new term in the field of technology. Hence it has the potential of delivering various benefits in various fields under various circumstances. Some of which are discussed below:-

Showcase

Holograms from the very early days of research are considered the best tool for the showcase of various precious objects or personalities. Holography is used for showcasing various global leaders and various tools that can’t be made public and their only prototypes are displayed in the form of Holograms. In the same, reflection holograms is way more forward in terms of global acceptance.

Data storage

With the pandemic hitting the World harder, we are continuously shifting the ways online, thereby generating a ton of data scraps every day. This sudden shift has raised digital storage demands globally, triggering the consumer rollout of holographic-based data storage mechanisms. 

Physical data storage on the one hand stores data unencrypted and accessible for everybody but holography-based storage records the light emitting from the object to be recorded. Therefore can store the raw or pure format of data i.e. pages, media, documents, etc. In comparison to the physical drivers, these are way long-lasting and secure for data storage.

Medical Education

The most difficult task for a medical student is the practice of surgeries making a better surgeon of the future. In this initiative, as discussed earlier, 3D Printing medical organs can help in studying the human body. However, in the same context, Hologram can perform way better by reconstructing deeply detailed imagery for every time in use. 

For the same initiative, a brand from Scotland had successfully operated the same technique for one of the country’s medical colleges. For proper implementation of Holography in Medical Science, data storage techniques involving holography may also be implemented to store high-definition images of human organs or anyways without 3d printing the same or operating in real-life.

Privacy/ Security

Holography-based optical devices are complex and make frauds a lot more difficult to pull off than earlier. Modern credit cards or banknotes have a special holographic enhanced implementation that is monochromatically backed by a mirror that changes its wavelength as you use the card for transactions. This as a result helps users for better and enhanced security at the time of checkout.

Future of Holography

According to a survey, Holography is expected to gain a market net-worth of 5 Billion USD in the coming decade with a lot of applications coming as time goes on. With the rise of the 2020’s pandemic, World has witnessed the need for physical meetings, especially in the corporate sectors. Various researchers laid out their views on Holographic Meetings or Conferencing.

Apart from the conferencing, Hologram is expected to completely change the security and storage in the upcoming years with a ton of applications in various fields.

So this was it for today’s post. We will see you soon in the upcoming one with an amazing explanation. Hope you liked our presentation, if yes then kindly consider sharing with others but if not, kindly leave a comment below with valuable feedback.

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