Holograms: Difference between revisions
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A hologram is the recorded interference pattern between a point sourced of light of fixed wavelength (reference beam) and a wavefield scattered from the object (object beam). A hologram is recorded in a two- or three-dimensional medium and contains information about the entire three-dimensional wavefield of the recorded object. When the hologram is illuminated by the reference beam, the diffraction pattern recreates the lightfield of the original object. The viewer is then able to see an image that is indistinguishable from the recorded object <ref name=”1”> Jeong, A. and Jeong, T. What are the main types of holograms? Retrieved from http://www.integraf.com/resources/articles/a-main-types-of-holograms</ref> <ref name=”2”> Schnars, U. and Jüptner, W. (2002). Digital recording and numerical reconstruction of holograms. Meas. Sci. Technol., 13: R85-R101</ref>. | A hologram is the recorded interference pattern between a point sourced of light of fixed wavelength (reference beam) and a wavefield scattered from the object (object beam). A hologram is recorded in a two- or three-dimensional medium and contains information about the entire three-dimensional wavefield of the recorded object. When the hologram is illuminated by the reference beam, the diffraction pattern recreates the lightfield of the original object. The viewer is then able to see an image that is indistinguishable from the recorded object <ref name=”1”> Jeong, A. and Jeong, T. What are the main types of holograms? Retrieved from http://www.integraf.com/resources/articles/a-main-types-of-holograms</ref> <ref name=”2”> Schnars, U. and Jüptner, W. (2002). Digital recording and numerical reconstruction of holograms. Meas. Sci. Technol., 13: R85-R101</ref>. | ||
The holographic plate is a kind of recording medium, in which the 3D virtual image of an object is stored. While in a recording media | The holographic plate is a kind of recording medium, in which the 3D virtual image of an object is stored. While in a recording media (e.g a CD) the grooves contain information about sound that can be used to reconstruct a song, a holographic plate contains information about light that is used to reconstruct an object <ref name=”3”> Physics Central. Holograms: virtually approaching science fiction. Retrieved from http://physicscentral.com/explore/action/hologram.cfm</ref>. | ||
The information about light is coded in the form of bright and dark microinterferences. Usually, these are not visible to the human eye due to the high spatial frequencies. Reconstructing the object wave by illuminating the hologram with the reference wave creates a 3D image that exhibits the effects of perspective and depth of focus <ref name=”2”></ref>. | The information about light is coded in the form of bright and dark microinterferences. Usually, these are not visible to the human eye due to the high spatial frequencies. Reconstructing the object wave by illuminating the hologram with the reference wave creates a 3D image that exhibits the effects of perspective and depth of focus <ref name=”2”></ref>. | ||
This photographic technique of recording light scattered from an object and presenting it as a 3D image is called Holography. The object representations | This photographic technique of recording light scattered from an object and presenting it as a 3D image is called Holography. The object's representations generated by this technique are the most lifelike 3D renditions because it records information in a way closer to what our eyes use to see the world around us <ref name=”4”> Workman, R. (2013). What is a hologram? Retrieved from http://www.livescience.com/34652-hologram.html</ref> <ref name=”5”> Bryner, M. (2010). ‘Star Wars’-like holograms nearly a reality. Retrieved from http://www.livescience.com/10227-star-wars-holograms-reality.html</ref>. Therefore, it is an attractive imaging technique since it allows the viewer to see a complete three-dimensional volume of one image <ref name=”6”> Rosen, J., Katz, B. and Brooker, G. (2009). Review of three-dimensional holographic imaging by Fresnel incoherent correlation holograms. 3D Research, 1(1)</ref>. | ||
Throughout the years, several types of holograms have been created. These include transmission holograms, that allow light to be shined through them and the image to be viewed from the side, and rainbow holograms. These are common in credit cards and driver’s licenses (used for security reasons) <ref name=”4”></ref>. | Throughout the years, several types of holograms have been created. These include transmission holograms, that allow light to be shined through them and the image to be viewed from the side, and rainbow holograms. These are common in credit cards and driver’s licenses (used for security reasons) <ref name=”4”></ref>. | ||
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True 3D holograms could not be a practical reality without the invention of the laser. A laser creates waves of light that are coherent. It is this coherent light that makes it possible to record the light wave interference patterns of holography <ref name=”8”></ref>. While white light contains all of the different frequencies of light traveling in all directions, laser light produces light that has only one wavelength and one color (Figure 1) <ref name=”7”></ref>. | True 3D holograms could not be a practical reality without the invention of the laser. A laser creates waves of light that are coherent. It is this coherent light that makes it possible to record the light wave interference patterns of holography <ref name=”8”></ref>. While white light contains all of the different frequencies of light traveling in all directions, laser light produces light that has only one wavelength and one color (Figure 1) <ref name=”7”></ref>. | ||
In | In its basic form, three elements are necessary to create a hologram: an object or person, a laser beam, and a recording medium. A clear environment is also recommended to enable the light beams to intersect <ref name=”4”></ref>. | ||
The laser beam is separated into two beams and redirected using mirrors (Figure 2). One of the beams is directed at the object, while the other - the reference beam - is directed | The laser beam is separated into two beams and redirected using mirrors (Figure 2). One of the beams is directed at the object, while the other - the reference beam - is directed to the recording medium. Some of the light of the object beam is reflected off the object onto the recording medium. The beams intersect and interfere with each other, creating an interference pattern that is imprinted on the recording medium. This medium can be composed of various materials. A common recording medium is a photographic film with an added amount of light reactive grains, enabling a higher resolution for the two beams, and making the image more realistic than using silver halide material <ref name=”4”></ref>. | ||
A developed film from a regular camera shows the negative view of the original scene, with light and dark areas. Looking at it, it is still possible to more or less understand what the original scene looked like. However, when looking at a revealed holographic tape, there is nothing that resembles the original scene. There can be dark frames of film or a random pattern of lines and swirls, and only with the right illumination is the captured object properly shown <ref name=”7”></ref>. | A developed film from a regular camera shows the negative view of the original scene, with light and dark areas. Looking at it, it is still possible to more or less understand what the original scene looked like. However, when looking at a revealed holographic tape, there is nothing that resembles the original scene. There can be dark frames of film or a random pattern of lines and swirls, and only with the right illumination is the captured object properly shown <ref name=”7”></ref>. | ||
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==Brief history== | ==Brief history== | ||
'''1886 -''' Gabriel Lippmann, in France, develops a theory of using light wave interference to capture color in photography. He presented his theory in 1891 to the Academy of Sciences, along with some primitive examples of his interference color photographs. In 1983, he presented perfect color photographs to the Academy and won a Nobel Prize in Physics in 1908 due to his work in this area. | '''1886 -''' Gabriel Lippmann, in France, develops a theory of using light wave interference to capture color in photography. He presented his theory in 1891 to the Academy of Sciences, along with some primitive examples of his interference color photographs. In 1983, he presented perfect color photographs to the Academy and won a Nobel Prize in Physics, in 1908, due to his work in this area. | ||
1947 - Dennis Gabor develops the theory of holography. He coined the term hologram from the Greek words holos (meaning ‘whole’) and gramma (‘message’). | |||
'''1947''' - Dennis Gabor develops the theory of holography. He coined the term hologram from the Greek words holos (meaning ‘whole’) and gramma (‘message’). | |||
'''1960 -''' N. Bassov, A. Prokhorov, and Charles Towns contributed to the development of the laser. Its pure, intense light was optimal for creating holograms. | '''1960 -''' N. Bassov, A. Prokhorov, and Charles Towns contributed to the development of the laser. Its pure, intense light was optimal for creating holograms. | ||
'''1962 -''' Yuri Denisyuk publishes his work in recording 3D images, inspired by | '''1962 -''' Yuri Denisyuk publishes his work in recording 3D images, inspired by Lippmann’s description of interference photography. He began his experiments in 1958 using a highly filtered mercury discharge tube as his light source. | ||
'''1968 -''' Dr. Stephen A. Benton invents the white-light transmission holography while researching holographic television. The white-light hologram can be viewed in ordinary white light. | '''1968 -''' Dr. Stephen A. Benton invents the white-light transmission holography while researching holographic television. The white-light hologram can be viewed in ordinary white light. | ||
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==Main types of holograms== | ==Main types of holograms== | ||
'''White-light transmission holograms -''' This type of | '''White-light transmission holograms -''' This type of hologram is illuminated with incandescent light, producing images that contain the rainbow spectrum of colors. Depending on the point of view of the viewer, the holograms' colors change. They are also called rainbow holograms. | ||
'''Reflection holograms -''' Reflection holograms are usually mass-produced using a stamping method. They can be seen in credit cards or in a driver’s license. Normally, these holograms can be viewed in white light. | '''Reflection holograms -''' Reflection holograms are usually mass-produced using a stamping method. They can be seen in credit cards or in a driver’s license. Normally, these holograms can be viewed in white light. | ||
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'''Transmission holograms -''' Typically, a transmission hologram is viewed with laser light. The light is directed from behind the hologram and the image projected to the viewer’s side. | '''Transmission holograms -''' Typically, a transmission hologram is viewed with laser light. The light is directed from behind the hologram and the image projected to the viewer’s side. | ||
'''Hybrid hologram -''' | '''Hybrid hologram -''' This type of hologram is between the reflection and transmission types. Examples include embossed holograms, integral holograms, holographic interferometry, multichannel holograms, and computer-generated holograms. <ref name=”1”></ref> <ref name=”7”></ref> <ref name=”10”> MIT Museum. Holography glossary. Retrieved from https://mitmuseum.mit.edu/holography-glossary</ref> | ||
==References== | ==References== | ||