It was later applied in the University of Michigan. It used silver halide emulsions as the recoding medium although the images formed were not very clear. Over the recent years, the technology has been improved through the application of refractive index to alter light transmission. This has also seen development of many types of holograms including transmission and rainbow holograms (Workman 2). Transmission hologram allows light through it but the image is viewed from the side. Rainbow hologram on the other hand is used to serve security purposes on drivers’ licenses and on credit cards.
Hologram is set by use of an object, a beam of light and recording medium (Workman 1). The beam of light should be shined on the object so as to cast its image on the recording medium. The environment should be appropriate to allow intersection of light as it enters into the hologram. A mirror is used to direct light to both the recording medium and the object. The beam of light moving to the object is known as the object or illumination beam and the one moving to the recording medium is known as the reference beam (Workman 2). The two set of beams coordinate to produce a clear image onto the medium. The interaction between the two patters gives rise to interference pattern which are now recorded as the virtual image. The recording medium can be made using various materials but the most common one is the photographic film (Workman 2). Some light-reactive grains are added to this film to make it react with the incoming beam of light. This has made it possible to record a higher resolution compared to that produced by halide materials used in 1960s.
Currently, researchers have formed tiny holograms by use of meta-surface. This hologram is able to control light and has advanced sensors, fast information processing and high resolution. Meta-surface is made up of thousands of V-shaped nano-antennas which are made into ultrathin gold foil (Elmorshidy 104). These