How is a hologram made?

Answer 1

The word "holography" is derived from the Greek words "holos" (whole) and "graphe" (writing). A hologram is a recording of an object, very similar in concept to a standard photograph, but significantly more sophisticated. When light waves are reflected from an object, the sizes (the amplitudes) of the waves, the frequency in which the waves occur (the wavelengths) and the phases of the waves: (the points where their peaks and troughs occur) are different, causing them to interfere with each other and thus affecting our visual perception of the object. While a black and white photograph merely records the amplitude of light (as its intensity or brightness), and a colour photograph records both the amplitude and wavelength (in the form of brightness and colour), a hologram records both the phases and amplitudes of the light waves: in effect, the whole "light field" reflected by an object. (Some types of hologram also record wavelength, resulting in coloured holograms, though they are often just monochromatic- usually green or red). The result is an almost ghostly image of the "real object" in its original, solid, three-dimensional state, which usually appears to be floating in space "behind" the surface of the image. Holograms have "parallax"- they appear different depending upon your viewpoint. The different view of a hologram that we see from each of our eyes creates the three dimensional effect. Therefore, the viewer can move back and forth in front of a hologram and see the image move as their viewpoint changes, as if they were looking at the original object itself. Holography is not only used to record images, it can also be used to store information optically. In fact, two of the most commonplace data storage media, CD and DVD, have key aspects in common with holograms: they rely upon laser technology to function and incorporate a "diffraction grating"- a grid of microscopic ridges that interfere with the light that reflects from them. The differences in the light reflected from the surface of the discs allow for the data to be encoded. Another commonplace technology that owes much to holography can be found in the scanners used to read the prices of items from barcodes at supermarket checkouts. Holographic technology is still evolving very quickly (and Martin Richardson's work is a definite part of that evolution). As a result, techniques that allow the creation of digital holograms are already in existence, as are methods for creating "real-time" (i.e. moving) holograms. These technologies are expected to become increasingly commonplace in the near future. The concept of holography was invented initially by the Hungarian physicist Dennis Gabor in 1948, but he was prevented from executing his idea particularly effectively by the lack of a light source of the required "coherence" (see "how holograms are made"- later in this article) and an emulsion of the necessary sophistication to process the images. These problems were alleviated by the subsequent invention of the laser just over ten years later, allowing the first holographic recordings of three dimensional objects to be created by Emmett Leith and Juris Upatnieks (in the United States) and Yuri Denisyuk (in the Soviet Union) in the early 1960s. Once the technology necessary to create effective holograms arrived upon the scene, the ground- breaking importance of Gabor's discovery was recognised and in 1971 he was awarded the Nobel Prize for Physics. In their early days, holograms often needed the intense "coherent" light of a laser to be viewed as well as created, but it was not long before holograms that could be viewed in ordinary white light became more commonplace. These were typically monochrome (i.e. one colour) but in the years since, colour holographs have also been created (including some ground-breaking colour images created by Martin himself). A major factor in the growth of holography has been the wider availability of "solid state" laser technology of the sort used in CD and DVD players. The increasing sophistication of these cheaper, smaller lasers has broadened the ability to create holograms to enthusiasts with lower budgets.

A holographic image is generated by a swirling, intricate pattern of "intensity fringes"- ridges and troughs- that have been burned into a photographic plate by coherent beams of light. This pattern distorts the light waves that fall upon it, changing their amplitudes and wavelengths so that they interfere with one another. The pattern of ridges is a form of "diffraction grating", an incredibly complex surface that distorts the light reflected from it or refracted through it, in a similar way to the "rainbow" patterns that can be seen when a CD or DVD are tilted in a light source. The more complex, controlled distortion of light caused by a hologram's diffraction grating recreates a specific pattern of the phases of light waves. The waves recreated are those reflected from the original object that first exposed the photographic plate when the hologram was created. This recreation of "all the light" reflected from the original object creates the hologram's three-dimensional effect (the "whole word", in effect). The image of the object is captured from every point of view on the reflected side. Many of the early holograms could only be viewed by shining bright laser light through them. However, "rainbow transmission holograms" that reflect a mirrored background back through the diffraction grating were another early development. These allowed holograms to be viewed in white light for the first time, and thus broadened their accessibility to those without a laser light source. A further development in holography was the "white light reflection hologram", where the light from the viewer's side of the hologram is reflected back from the diffraction grating to create an impression of the original light field. These holograms can be breathtaking in their realism, though it is important to pay attention to the way they are lit when put on display to allow the full effect to be achieved. The current cutting-edge of holography concerns both the digital generation and recording of holograms, by either controlling the light source that creates the hologram with a computer to generate "virtual" images, or using a CCD sensor (of the sort found in a digital camera) to record the holographic information. Another area of research is the creation of "real time" holograms, where the light source generates an image in a medium that can be "refreshed"- allowing sequences of holograms to be strung together to replicate movement. Unlike traditional Photography, where only a fraction of the light reflecting from an object is focused through an aperture via a lens, a holographic image is created by capturing the entire "field" of light that is reflected from the original object. This process is undertaken by splitting a "coherent" beam of light with a beam splitter. Half of the beam is directed at the object whose image is being captured, and is thus referred to as the object beam. The reflected light from the object then falls upon the photographic plate that is exposed to create the hologram. Meanwhile, the second half of the original beam (known as the reference beam) is also directed at the holographic plate using a mirror. The interference between the light waves as they merge on the surface of the plate exposes it with the image; the end result is that the entire light field reflected by the object is captured. Lasers are used in holography as they provide the "coherent" light necessary for the process to work, though it is possible to use other forms of light source. For instance, Dennis Gabor's original experiments were undertaken using Mercury arc lamps, though these are far less effective than lasers. In essence, the coherence of the light refers to the similarity in amplitude and phase of the light waves contained within the beam- in effect, how "in-step" the light waves are. Waves within the reference beam remain coherent, whereas waves reflected from the object are interfered with: less so when they have fallen upon a reflective, shiny surface, more so when the fall upon darker, absorbent surfaces. As the more coherent waves in the object beam merge with the reference beam, they expose the plate more. The less coherent waves in the object beam expose it less. In this fashion, the entire field of light is captured: the plate records the object from every viewpoint of the side that is reflected, not just from the restricted point of view captured by traditional photography. The word "holography" is derived from the Greek words "holos" (whole) and "graphe" (writing). A hologram is a recording of an object, very similar in concept to a standard photograph, but significantly more sophisticated. When light waves are reflected from an object, the sizes (the amplitudes) of the waves, the frequency in which the waves occur (the wavelengths) and the phases of the waves: (the points where their peaks and troughs occur) are different, causing them to interfere with each other and thus affecting our visual perception of the object. While a black and white photograph merely records the amplitude of light (as its intensity or brightness), and a colour photograph records both the amplitude and wavelength (in the form of brightness and colour), a hologram records both the phases and amplitudes of the light waves: in effect, the whole "light field" reflected by an object. (Some types of hologram also record wavelength, resulting in coloured holograms, though they are often just monochromatic- usually green or red). The result is an almost ghostly image of the "real object" in its original, solid, three-dimensional state, which usually appears to be floating in space "behind" the surface of the image. Holograms have "parallax"- they appear different depending upon your viewpoint. The different view of a hologram that we see from each of our eyes creates the three dimensional effect. Therefore, the viewer can move back and forth in front of a hologram and see the image move as their viewpoint changes, as if they were looking at the original object itself. Holography is not only used to record images, it can also be used to store information optically. In fact, two of the most commonplace data storage media, CD and DVD, have key aspects in common with holograms: they rely upon laser technology to function and incorporate a "diffraction grating"- a grid of microscopic ridges that interfere with the light that reflects from them. The differences in the light reflected from the surface of the discs allow for the data to be encoded. Another commonplace technology that owes much to holography can be found in the scanners used to read the prices of items from barcodes at supermarket checkouts. Holographic technology is still evolving very quickly (and Martin Richardson's work is a definite part of that evolution). As a result, techniques that allow the creation of digital holograms are already in existence, as are methods for creating "real-time" (i.e. moving) holograms. These technologies are expected to become increasingly commonplace in the near future. The concept of holography was invented initially by the Hungarian physicist Dennis Gabor in 1948, but he was prevented from executing his idea particularly effectively by the lack of a light source of the required "coherence" (see "how holograms are made"- later in this article) and an emulsion of the necessary sophistication to process the images. These problems were alleviated by the subsequent invention of the laser just over ten years later, allowing the first holographic recordings of three dimensional objects to be created by Emmett Leith and Juris Upatnieks (in the United States) and Yuri Denisyuk (in the Soviet Union) in the early 1960s. Once the technology necessary to create effective holograms arrived upon the scene, the ground- breaking importance of Gabor's discovery was recognised and in 1971 he was awarded the Nobel Prize for Physics. In their early days, holograms often needed the intense "coherent" light of a laser to be viewed as well as created, but it was not long before holograms that could be viewed in ordinary white light became more commonplace. These were typically monochrome (i.e. one colour) but in the years since, colour holographs have also been created (including some ground-breaking colour images created by Martin himself). A major factor in the growth of holography has been the wider availability of "solid state" laser technology of the sort used in CD and DVD players. The increasing sophistication of these cheaper, smaller lasers has broadened the ability to create holograms to enthusiasts with lower budgets.

A holographic image is generated by a swirling, intricate pattern of "intensity fringes"- ridges and troughs- that have been burned into a photographic plate by coherent beams of light. This pattern distorts the light waves that fall upon it, changing their amplitudes and wavelengths so that they interfere with one another. The pattern of ridges is a form of "diffraction grating", an incredibly complex surface that distorts the light reflected from it or refracted through it, in a similar way to the "rainbow" patterns that can be seen when a CD or DVD are tilted in a light source. The more complex, controlled distortion of light caused by a hologram's diffraction grating recreates a specific pattern of the phases of light waves. The waves recreated are those reflected from the original object that first exposed the photographic plate when the hologram was created. This recreation of "all the light" reflected from the original object creates the hologram's three-dimensional effect (the "whole word", in effect). The image of the object is captured from every point of view on the reflected side. Many of the early holograms could only be viewed by shining bright laser light through them. However, "rainbow transmission holograms" that reflect a mirrored background back through the diffraction grating were another early development. These allowed holograms to be viewed in white light for the first time, and thus broadened their accessibility to those without a laser light source. A further development in holography was the "white light reflection hologram", where the light from the viewer's side of the hologram is reflected back from the diffraction grating to create an impression of the original light field. These holograms can be breathtaking in their realism, though it is important to pay attention to the way they are lit when put on display to allow the full effect to be achieved. The current cutting-edge of holography concerns both the digital generation and recording of holograms, by either controlling the light source that creates the hologram with a computer to generate "virtual" images, or using a CCD sensor (of the sort found in a digital camera) to record the holographic information. Another area of research is the creation of "real time" holograms, where the light source generates an image in a medium that can be "refreshed"- allowing sequences of holograms to be strung together to replicate movement. Unlike traditional photography, where only a fraction of the light reflecting from an object is focused through an aperture via a lens, a holographic image is created by capturing the entire "field" of light that is reflected from the original object. This process is undertaken by splitting a "coherent" beam of light with a beam splitter. Half of the beam is directed at the object whose image is being captured, and is thus referred to as the object beam. The reflected light from the object then falls upon the photographic plate that is exposed to create the hologram. Meanwhile, the second half of the original beam (known as the reference beam) is also directed at the holographic plate using a mirror. The interference between the light waves as they merge on the surface of the plate exposes it with the image; the end result is that the entire light field reflected by the object is captured. Lasers are used in holography as they provide the "coherent" light necessary for the process to work, though it is possible to use other forms of light source. For instance, Dennis Gabor's original experiments were undertaken using mercury arc lamps, though these are far less effective than lasers. In essence, the coherence of the light refers to the similarity in amplitude and phase of the light waves contained within the beam- in effect, how "in-step" the light waves are. Waves within the reference beam remain coherent, whereas waves reflected from the object are interfered with: less so when they have fallen upon a reflective, shiny surface, more so when the fall upon darker, absorbent surfaces. As the more coherent waves in the object beam merge with the reference beam, they expose the plate more. The less coherent waves in the object beam expose it less. In this fashion, the entire field of light is captured: the plate records the object from every viewpoint of the side that is reflected, not just from the restricted point of view captured by traditional photography. The word "holography" is derived from the Greek words "holos" (whole) and "graphe" (writing). A hologram is a recording of an object, very similar in concept to a standard photograph, but significantly more sophisticated. When light waves are reflected from an object, the sizes (the amplitudes) of the waves, the frequency in which the waves occur (the wavelengths) and the phases of the waves: (the points where their peaks and troughs occur) are different, causing them to interfere with each other and thus affecting our visual perception of the object. While a black and white photograph merely records the amplitude of light (as its intensity or brightness), and a colour photograph records both the amplitude and wavelength (in the form of brightness and colour), a hologram records both the phases and amplitudes of the light waves: in effect, the whole "light field" reflected by an object. (Some types of hologram also record wavelength, resulting in coloured holograms, though they are often just monochromatic- usually green or red). The result is an almost ghostly image of the "real object" in its original, solid, three-dimensional state, which usually appears to be floating in space "behind" the surface of the image. Holograms have "parallax"- they appear different depending upon your viewpoint. The different view of a hologram that we see from each of our eyes creates the three dimensional effect. Therefore, the viewer can move back and forth in front of a hologram and see the image move as their viewpoint changes, as if they were looking at the original object itself. Holography is not only used to record images, it can also be used to store information optically. In fact, two of the most commonplace data storage media, CD and DVD, have key aspects in common with holograms: they rely upon laser technology to function and incorporate a "diffraction grating"- a grid of microscopic ridges that interfere with the light that reflects from them. The differences in the light reflected from the surface of the discs allow for the data to be encoded. Another commonplace technology that owes much to holography can be found in the scanners used to read the prices of items from barcodes at supermarket checkouts. Holographic technology is still evolving very quickly (and Martin Richardson's work is a definite part of that evolution). As a result, techniques that allow the creation of digital holograms are already in existence, as are methods for creating "real-time" (i.e. moving) holograms. These technologies are expected to become increasingly commonplace in the near future. The concept of holography was invented initially by the Hungarian physicist Dennis Gabor in 1948, but he was prevented from executing his idea particularly effectively by the lack of a light source of the required "coherence" (see "how holograms are made"- later in this article) and an emulsion of the necessary sophistication to process the images. These problems were alleviated by the subsequent invention of the laser just over ten years later, allowing the first holographic recordings of three dimensional objects to be created by Emmett Leith and Juris Upatnieks (in the United States) and Yuri Denisyuk (in the Soviet Union) in the early 1960s. Once the technology necessary to create effective holograms arrived upon the scene, the ground- breaking importance of Gabor's discovery was recognised and in 1971 he was awarded the Nobel Prize for Physics. In their early days, holograms often needed the intense "coherent" light of a laser to be viewed as well as created, but it was not long before holograms that could be viewed in ordinary white light became more commonplace. These were typically monochrome (i.e. one colour) but in the years since, colour holographs have also been created (including some ground-breaking colour images created by Martin himself). A major factor in the growth of holography has been the wider availability of "solid state" laser technology of the sort used in CD and DVD players. The increasing sophistication of these cheaper, smaller lasers has broadened the ability to create holograms to enthusiasts with lower budgets.

A holographic image is generated by a swirling, intricate pattern of "intensity fringes"- ridges and troughs- that have been burned into a photographic plate by coherent beams of light. This pattern distorts the light waves that fall upon it, changing their amplitudes and wavelengths so that they interfere with one another. The pattern of ridges is a form of "diffraction grating", an incredibly complex surface that distorts the light reflected from it or refracted through it, in a similar way to the "rainbow" patterns that can be seen when a CD or DVD are tilted in a light source. The more complex, controlled distortion of light caused by a hologram's diffraction grating recreates a specific pattern of the phases of light waves. The waves recreated are those reflected from the original object that first exposed the photographic plate when the hologram was created. This recreation of "all the light" reflected from the original object creates the hologram's three-dimensional effect (the "whole word", in effect). The image of the object is captured from every point of view on the reflected side. Many of the early holograms could only be viewed by shining bright laser light through them. However, "rainbow transmission holograms" that reflect a mirrored background back through the diffraction grating were another early development. These allowed holograms to be viewed in white light for the first time, and thus broadened their accessibility to those without a laser light source. A further development in holography was the "white light reflection hologram", where the light from the viewer's side of the hologram is reflected back from the diffraction grating to create an impression of the original light field. These holograms can be breathtaking in their realism, though it is important to pay attention to the way they are lit when put on display to allow the full effect to be achieved. The current cutting-edge of holography concerns both the digital generation and recording of holograms, by either controlling the light source that creates the hologram with a computer to generate "virtual" images, or using a CCD sensor (of the sort found in a digital camera) to record the holographic information. Another area of research is the creation of "real time" holograms, where the light source generates an image in a medium that can be "refreshed"- allowing sequences of holograms to be strung together to replicate movement. Unlike traditional photography, where only a fraction of the light reflecting from an object is focused through an aperture via a lens, a holographic image is created by capturing the entire "field" of light that is reflected from the original object. This process is undertaken by splitting a "coherent" beam of light with a beam splitter. Half of the beam is directed at the object whose image is being captured, and is thus referred to as the object beam. The reflected light from the object then falls upon the photographic plate that is exposed to create the hologram. Meanwhile, the second half of the original beam (known as the reference beam) is also directed at the holographic plate using a mirror. The interference between the light waves as they merge on the surface of the plate exposes it with the image; the end result is that the entire light field reflected by the object is captured. Lasers are used in holography as they provide the "coherent" light necessary for the process to work, though it is possible to use other forms of light source. For instance, Dennis Gabor's original experiments were undertaken using mercury arc lamps, though these are far less effective than lasers. In essence, the coherence of the light refers to the similarity in amplitude and phase of the light waves contained within the beam- in effect, how "in-step" the light waves are. Waves within the reference beam remain coherent, whereas waves reflected from the object are interfered with: less so when they have fallen upon a reflective, shiny surface, more so when the fall upon darker, absorbent surfaces. As the more coherent waves in the object beam merge with the reference beam, they expose the plate more. The less coherent waves in the object beam expose it less. In this fashion, the entire field of light is captured: the plate records the object from every viewpoint of the side that is reflected, not just from the restricted point of view captured by traditional photography.

Answer 2

A hologram is made by a light shining through a projector making a hologram.