holograms

Holograms are three-dimensional images created using holography, a technique that records the light field emanating from an object rather than a single photograph. A hologram is typically a photographic plate or film that stores interference patterns produced when coherent light, usually from a laser, is split into an object beam that reflects from the subject and a reference beam that illuminates the recording medium. When the developed hologram is illuminated by the reference beam, the diffraction of light reconstructs the original light field, producing a 3D image with parallax as the viewer moves.

The concept was proposed by Dennis Gabor in 1947 as a method to improve electron microscopy; practical holography emerged in the 1960s with engineers Emmett Leith and Yuri Upatnieks using laser light and translucent emulsions.

Types and techniques include transmission holograms, viewed with light passing through the recording medium, and reflection holograms, viewed by reflected light. Volume holograms store 3D information in a thick recording medium, enabling angular and depth cues. Digital holography uses computer-generated holograms or spatial light modulators to create or display holograms without a physical object, supporting dynamic or interactive content.

Applications span data storage, security and anti-counterfeiting (such as holographic labels and banknotes), art and education, and medical imaging. Holographic displays and related technologies aim to present true 3D images for consumer devices, while holographic projection and augmented reality research explore dynamic holograms. Limitations include the need for coherent light sources, sensitivity to vibration, limited brightness and viewing angle, and higher manufacturing costs compared with conventional 2D media.

Despite these challenges, holography remains a versatile tool in science and industry, with ongoing advances in materials, digital synthesis, and novel display concepts expanding its practical use.