Gabor theorized in that each crest of the wave pattern contains the whole information of its original source, and that this information could be stored on film and reproduced. This is why it is called a Hologram.
Copying and mass production[ edit ] An existing hologram can be copied by embossing  or optically. Embossing, which is similar to the method used to stamp out plastic discs from a master in audio recording, involves copying this surface relief pattern by impressing it onto another material.
The first step in the embossing process is to make a stamper by electrodeposition of nickel on the relief image recorded on the photoresist or photothermoplastic.
When the nickel layer is thick enough, it is separated from the master hologram and mounted on a metal backing plate. The material used to make embossed copies consists of a polyester base film, a resin separation layer and a thermoplastic film constituting the holographic layer.
The embossing process can be carried out with a simple heated press. The bottom layer of the duplicating film the thermoplastic layer is heated above its softening point and pressed against the stamper, so that it takes up its shape.
This shape is retained when the film is cooled and removed from the press. In order to permit the viewing of embossed holograms in reflection, an additional reflecting layer of aluminum is usually added on the hologram recording layer.
This method is particularly suited to mass production. This featured a 5. On the inner sleeve was an explanation of the holographic process and instructions on how to light the hologram and National Geographic published the first magazine with a hologram cover in March Stability and coherence requirements are significantly reduced if the two plates are located very close together.
Uniform illumination can be obtained by scanning point-by-point or with a beam shaped into a thin line. Reconstructing and viewing the holographic image[ edit ] Holographic self-portrait, exhibited at the National Polytechnic Museum, Sofia When the hologram plate is illuminated by a laser beam identical to the reference beam which was used to record the hologram, an exact reconstruction of the original object wavefront is obtained.
When the lens is moved, the image changes in the same way as it would have done when the object was in place. If several objects were present when the hologram was recorded, the reconstructed objects move relative to one another, i.
It was very common in the early days of holography to use a chess board as the object and then take photographs at several different angles using the reconstructed light to show how the relative positions of the chess pieces appeared to change.
A holographic image can also be obtained using a different laser beam configuration to the original recording object beam, but the reconstructed image will not match the original exactly.
This can be a major drawback in viewing a hologram. White light consists of light of a wide range of wavelengths. Normally, if a hologram is illuminated by a white light source, each wavelength can be considered to generate its own holographic reconstruction, and these will vary in size, angle, and distance.
These will be superimposed, and the summed image will wipe out any information about the original scene, as if superimposing a set of photographs of the same object of different sizes and orientations. However, a holographic image can be obtained using white light in specific circumstances, e.
The white light source used to view these holograms should always approximate to a point source, i. An extended source e. White light reconstructions do not contain speckles. Volume hologram A reflection-type volume hologram can give an acceptably clear reconstructed image using a white light source, as the hologram structure itself effectively filters out light of wavelengths outside a relatively narrow range.
In theory, the result should be an image of approximately the same colour as the laser light used to make the hologram. In practice, with recording media that require chemical processing, there is typically a compaction of the structure due to the processing and a consequent colour shift to a shorter wavelength.
Such a hologram recorded in a silver halide gelatin emulsion by red laser light will usually display a green image. Deliberate temporary alteration of the emulsion thickness before exposure, or permanent alteration after processing, has been used by artists to produce unusual colours and multicoloured effects.
Rainbow hologram Rainbow hologram showing the change in colour in the vertical direction In this method, parallax in the vertical plane is sacrificed to allow a bright, well-defined, gradiently colored reconstructed image to be obtained using white light. The rainbow holography recording process usually begins with a standard transmission hologram and copies it using a horizontal slit to eliminate vertical parallax in the output image.
The viewer is therefore effectively viewing the holographic image through a narrow horizontal slit, but the slit has been expanded into a window by the same dispersion that would otherwise smear the entire image.
Horizontal parallax information is preserved but movement in the vertical direction results in a color shift rather than altered vertical perspective.
Stereopsis and horizontal motion parallax, two relatively powerful cues to depth, are preserved. The holograms found on credit cards are examples of rainbow holograms. These are technically transmission holograms mounted onto a reflective surface like a metalized polyethylene terephthalate substrate commonly known as PET.
Fidelity of the reconstructed beam[ edit ] Reconstructions from two parts of a broken hologram. Note the different viewpoints required to see the whole object To replicate the original object beam exactly, the reconstructing reference beam must be identical to the original reference beam and the recording medium must be able to fully resolve the interference pattern formed between the object and reference beams.
This requires very precise relocation of the developed holographic plate. Any change in the shape, orientation or wavelength of the reference beam gives rise to aberrations in the reconstructed image.History of Holography.
Holography dates from , when British (native of Hungary) scientist Dennis Gabor developed the theory of holography while working to improve the resolution of an electron srmvision.com coined the term Holography from the Greek words holos, meaning "whole," and gramma, meaning "message".
History of Hologram. Holography dates from , when British (native of Hungary) scientist Dennis Gabor developed the theory of holography while working to improve the resolution of an electron srmvision.com coined the term Hologram from the Greek words holos, meaning "whole," and gramma, meaning "message".
In its pure form, holography requires the use of laser light for illuminating the subject and for viewing the finished hologram. In a side-by-side comparison under optimal conditions, a holographic image is visually indistinguishable from the actual subject.
Dennis writes that the years after the war were the most fruitful. One his first papers was on communication theory. He also developed a system of stereoscopic cinematography, and in the last year at BTH carried out the basic experiments in holography, at that time called "wavefront reconstruction".
Dennis Gabor, inventor of holography, stands beside his 18"x24" laser transmission, pulsed portrait. The historic portrait was recorded in by R. Rinehart, McDonnell Douglas Electronics Company, St. Charles, MO to commemorate Gabor's winning of the Nobel Prize that year.
Dennis Gabor, inventor of holography, stands beside his 18"x24" laser transmission, pulsed portrait. The historic portrait was recorded in by R. Rinehart, McDonnell Douglas Electronics Company, St.
Charles, MO to commemorate Gabor's winning of the Nobel Prize that year.