What Is Hologram? | Definition | Principle | Applications

  • Holograms are virtual 3D images generated by the interference of light beams that reflect off real, physical objects
  • Holograms retain the depth, parallax, and other properties of the original object.
  • They are excellently suitable for presenting complex technical concepts and displaying visually appealing goods. 

Although the concept of holograms was introduced in the 1940s, it didn’t become popular until Princess Leia appeared as a floating image in Star Wars.

For years, it seemed like this technology was going to be forever relegated to the realms of science fiction. The things, however, are different today, thanks to advances in optical technology.

Below, we have explained what exactly is a hologram, how does it work, and its potential applications. We have tried to keep things as simple as possible, so you don’t get confused.

Definition Of Hologram

A hologram is a three-dimensional light field that is generated via a physical recording of an interference pattern. This pattern involves a phenomenon called diffraction, which ultimately results in a virtual 3D image of the original scene.

In simple terms, holograms are 3D images generated by the interference of light beams that reflect off real, physical objects. Unlike common 3D projections, holograms can be seen with the naked eye. There is no need to wear 3D glasses.

The science and practice of creating holograms is called holography. The technology has not quite caught up to movie magic yet, but it can be used to create holograms that retain the depth, parallax, and other properties of an actual scene.

Difference Between A Hologram And Ordinary Photographic Image

While an ordinary photographic image captures the variation in the intensity of light, holography captures both the intensity and phase of the light. This is why holograms produce truly three-dimensional images, instead of simply producing the illusion of depth.

3D holographic display | Credit: Voxon Photonics

A hologram represents a photographic recording of a light field, instead of a picture formed by a lens. It exhibits visual depth cues that realistically change with the observer’s relative position.

Holography is also different from lenticular and earlier autostereoscopic 3D display technologies, such as autostereoscopic. Although those technologies generate similar results, they rely on traditional lens imaging.

Who Invented The Holography?

In 1947, the Hungarian-British physicist Dennis Gabor developed a theory of hologram while working to enhance the resolution of an electron microscope. He coined the term hologram, which was taken from two Greek words ‘holos’ (meaning ‘whole’) and gramma (meaning ‘message’).

However, the optical holography didn’t really advance until the advent of the laser in 1960. The laser emits a very powerful burst of light that lasts only a few nanoseconds. This enabled holograms of high-speed events, such as a bullet in flight.

In the following decade, many scientists came up with different techniques to create 3D holograms using a laser. The first hologram of an individual was created in 1967, which paved the way for various applications of holography.

How Does Hologram Work?

Holography involves recording a light field and then reconstructing it in the absence of the original objects. You can think of it as something similar to sound recording, in which a sound field generated by vibrating substance is processed in such a manner that it can be regenerated later (in the absence of original vibrating substance).

Ambisonic sound recording (full-sphere surround sound format) is, in fact, more similar to holography, where specific listening angles of a sound field can be recreated in the reproduction.

To create a hologram, you need three things:

  1. A laser beam to be shined upon the object
  2. A recording medium with proper materials
  3. A clean environment to enable the light beam to intersect

Recording a hologram | Image credit: Wikimedia 

A laser beam is divided into two identical beams using a beamsplitter. One of them is reflected off the object onto the recording medium, while the other one is directly passed onto the recording medium. This way, it does not conflict with the imagery that comes from the object beam.

Reconstructing a hologram | Image credit: Wikimedia 

When two beams intersect with each other, they create an interference pattern, which is imprinted on the recording medium (mostly made of silver halide). The layer of this recording medium is attached to a transparent substrate, such as glass, which recreates the virtual image at a much higher resolution than photographic film.

The optical instruments, the object, and the recording medium must remain motionless relative to each other during the process. Otherwise, the interference pattern and the hologram will be blurred and spoiled.

Read: Scientists Develop Holograms That You Can Touch & Hear

Applications

3D holograms have a wide range of uses. For example, they can be used in:

Data Storage: Holographic data storage is a potential technology that can store information at high density inside photopolymers or crystals. As existing storage methods like Blu-ray Disc reach the upper limit of data density, holographic storage can become the next generation of popular storage media.

Security: Security holograms are by far the most common type of holograms. They are used widely in passports, bank and credit cards, and several banknotes around the world.

Although it is not a hologram in the true sense, the term ‘hologram’ has taken on a secondary meaning due to the extensive use of a multilayer image on driver licenses and credit cards. Some number plates on vehicles contain registered hologram stickers that indicate authenticity.

Sensor: A hologram embedded in a smart device makes a holographic sensor. It can be used to detect specific molecules or metabolites.

Scanners: Holographic scanners are used in automated conveyor systems and larger shipping firms to determine the dimensions of a package.

One of the latest (commercially available) implementations of holographic-like technology is the Microsoft HoloLens headset. It uses optical projection and computer processing systems to produce digital hologram-like objects that users can view and interact with in their real environment, but only while wearing the headset.

Among other things, holograms can be used for 

  • Trade fairs
  • Exhibitions
  • Events
  • Meetings
  • Museums
  • Showrooms
  • Product presentations

Apart from that, 3D holograms are perfectly suitable for presenting complex technical concepts, displaying precious gems and similar visually appealing goods.

Holography can additionally emphasize the beauty and perfection of the object being displayed, presenting it in an extremely aesthetic way.

Read: 18 Best Augmented Reality (AR) App

In principle, holograms can be created from any wave. Electron holography, for example, is the application of holography methods to electron waves (instead of light waves). It is mostly used to analyze electric and magnetic fields in thin films.

Similarly, neutron beam holography is used to observe the inside of solid objects.

Written by
Varun Kumar

Varun Kumar is a professional science and technology journalist and a big fan of AI, machines, and space exploration. He received a Master's degree in computer science from Indraprastha University. To find out about his latest projects, feel free to directly email him at [email protected] 

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