Holography is a technology that uses waves of light to reproduce three-dimensional stereoscopic images, and was developed with the invention of the laser. Used in museums and exhibitions, the technology has the potential to be commercialized and revolutionize a wide range of industries.
Holography is a combination of the Greek words “holo,” meaning “complete,” and “graphy,” meaning “picture,” and refers to the technology of taking and reproducing three-dimensional stereoscopic images that are perfect pictures. This technology is more than just taking a picture, and it has gained attention for its ability to recreate objects as if they were actually in front of you. Ordinary photographs taken with film or digital cameras record two-dimensional information about an object: light contrast and color. Holography, on the other hand, records phase information, which is three-dimensional information, based on the principle of light waves, and reproduces it as a three-dimensional image.
The principle of holography was first discovered in 1948 by the Hungarian-born British physicist Gabor, but it was not developed much at that time because there was no light source to realize it properly. In 1948, World War II had just ended, and the aftermath of the war limited research and development in science and technology. However, in the 1960s, the invention of the laser led to rapid advances in holographic technology. This is because lasers are monochromatic, unlike ordinary light, which is a mixture of multiple wavelengths, and have very strong luminance and a straight beam that does not spread, making them highly interference resistant. Luminance is a measure of the brightness of light radiated from a display screen such as a television or computer, and indirectness is a phenomenon in which two or more waves of the same type, such as sound or light waves, meet at a point and overlap, making them stronger or weaker than each other.
Let’s take a step-by-step look at how holography works. First, we split the laser in two, since the same beam of light interferes well. Since the laser is straight, you need a mirror to reflect the light in order to split it into two. One of the two beams of light hits the film without passing through the object (reference light), and the other beam hits the film with the reflected light from the object we want to see (object light). Since the object light is the light reflected from each surface of the object, the phase difference (the distance from the object surface to the film) is different for each surface of the object. When the reference light and object light are recombined on the film, the unmodified reference light interferes with the object light, creating a pattern. The interference pattern contains the three-dimensional information of the object, which is stored in the film. Unlike a simple drawing or photograph, the interference pattern imprinted on the film contains complex three-dimensional information through light waves and interference. This is the hologram you see on a banknote or credit card. To reproduce the stored image, you need to shoot a laser beam back at the hologram. This is because only waves with the same wavelength as when they were recorded are reproduced in three dimensions, while light with a different wavelength and phase passes through the stored hologram without any effect.
Although holography is not the only way to realize three-dimensional images, it is still used in museums and art exhibitions because it does not cause eye strain and has a better sense of three-dimensionality than other methods. In particular, holography plays an important role in the restoration of ancient artifacts and works of art. This is because the technology is excellent for creating detailed replicas without damaging the actual artifact.
However, holography is still a long way off from being beamed to your television and appearing in your living room, or being implemented in science fiction movies. Therefore, in order to commercialize holography, it is important to advance the technology by closely linking not only the basic optical technology but also related fields such as media-related technologies such as information processing and device material technology. In addition, the commercialization of holography has the potential to bring about innovative changes in education, entertainment, and medical fields, and related research is being actively conducted.
