Gagne de la cryptomonnaie GRATUITE en 5 clics et aide institut numérique à propager la connaissance universitaire >> CLIQUEZ ICI <<

4) Holograms

Non classé

Nowadays, when one refers to the hologram we tend to ask questions about it. A question that is often asked when I mention it around me, it still subsist a misunderstanding. After a few well-established references, my interlocutors tend to think of it as being out of time, imaginary or utopian. For moviegoers, the hologram is the Red Queen in “Resident Evil” or “Star Wars.” For the majority of people this is fiction, but most of the time fiction is just near to reality.

With the rapid development of new technologies, we definitely could imagine that the commercialization of holograms would maybe create a new market in the world of communication.

Holography is considered as a branch of optics, combining some rules of physics (using laser) to technological prowess in recent years (tools more efficient) and some knowledge of chemistry or photograph (chemical development of the hologram plate). Holography could be defined as three-dimensional photographic representation of an object through the light. Light plays an essential role in the holographic representation: the laser light used to print the image permanently and reproduce (same for white light) the same image. During the past decade, the final report (hologram) becomes more realistic and begins a breakthrough in the field of advertising.

Laser light is called coherent light because all the photons that compose it have the same frequency. Unlike the so-called incoherent white light that goes in all directions and deflected by a prism, we can see that it is composed of several photons of different frequency (color), this is called the spectrum of light and it can be seen in the nature during rainbow (method of refraction of the white light through the water droplets of rain)

At the beginning, holography was a mean of expression for many artists that search a new form of expression combining fictional realism and lighting. Nowadays variations are larger, such as in the fields of fashion industry, advertising, presentation of a brand or product, entertainment and some professionals and scientists believe that it would be one day part of our daily lives.

The following study will attempt to collect the different fields of application of holography, these variations, behind the scenes but also the analysis of the cost and impact of new communication technologies.

a. Holograms by transmission

The hologram by transmission is the most common. The laser light register the hologram and transcript it. The object is illuminated by two beams from the same laser. Each beam plays a very important role in the realization of the hologram. One can capture the shapes of the object and the other acts as a spot.

The principle is the following : There is a plate that interfere two beams of coherent light (laser). The first beam (called reference) is directed towards the plate, while the second (called the object beam) illuminate the object and prints the image on the plate. The addition of the two beams creates an image, that conveys information and print it on the plate (position in space, outline, form, appearance …). The process requires bringing reflective and semi reflective mirror in order to adjust the two beams onto the plate. Therefore the laser light plays the role of information carrier which will then be engraved on a plaque.

The equipment needed for such an assembly is accessible to all, just bring a table anti vibration, laser, two lenses, two reflecting mirrors, two semi-reflecting mirrors, film or holographic plate, an object and a shutter(5).

Holograms by transmission

This is by illuminating the plate with the beam (which is identical to the reference beam) that we obtain the hologram. The projected image gives the illusion of a real object in three dimensions. It recreates the wave of holography that characterizes the object from a reference wave. Indeed, every object has a wave field of its own.

The only limit of this technique is that it is necessary to visualize it with the laser that recorded it. Again, science has made its solution to the problem by inventing a process that is perfectly suited to white light…

b. Holograms by reflection

The reflection hologram has the great advantage of being visible white light (sunlight or a standard lamp). In addition to visible white light, installation is easier to achieve because it does not require much equipment compared with the hologram transmission.

The equipment required is as follows: anti vibration table, a laser, a lens, a reflecting mirror, a holographic film or plate, an object and a shutter.

The principle is the following mounting, place the holographic film or plate between the object and the laser. The laser light passes through the hologram plate and then typing the object and is then reflected on the plate. In this case the laser beam plays both the role of the reference beam and object beam, the interference of the two then gives the image printed on the plate producing the hologram. In order to see the hologram it is necessary to place the light on the same side as the observer.(6)

Holograms by reflection

The reflection hologram is observable by the white light for the simple reason that the holographic plate let’s all light rays. The installation is the same as we have seen previously with the hologram by transmission. Without the filtering effect, the image is blurred, so a hologram observed in white light will always be the same color as the laser used for shooting.

The difference between the transmission hologram and the reflection hologram is the mounting, and the refund. The exposure and development are the same as for the transmission hologram (although the fixing bath is replaced by bleach).

c. Rainbow hologram

The rainbow hologram is simply the most widespread and more present in our daily lives. In 1968 Dr. Benton invented this technology for the company Polaroid Corporation which later became MIT. The rainbow hologram has the distinction of being restored by the white light so the angle of view appears with several colors. We can easily see it on our credit cards, in advertising, gadgets (collectible cards, for example) or in software.

To make a rainbow hologram, we must first proceed according to the principle of reflection hologram which is then covered with a film and then apply a second hologram.

Rainbow holograms are also called security holograms, they appear on our passports, credit cards, identity cards, visas, and bank note … They may not be copied or be photographed or scanned which it gives them, the character of inviolability.

This field appears as a company leading the fight against counterfeiting. This company is actually a group “Hologramme Industries” (Cf companies’ cases).

“Now we can record a three-dimensional image in one location and present it to another location, in real time, anywhere in the world,”
Nasser Peyghambarian, professor in charge of holographic research project.

6 See appendix 3

Page suivante : Chapter 3 : Issues

Retour au menu : Hologram : A niche market