What's the modus operandi of holograms?<\/p>\n
JAKARTA (JP): Holography is a special photographic technique
\nusing two laser beams that are in interference with each other on
\na photographic plate of film (photographic emulsion). The first
\nbeam is directed immediately towards the film, while the second
\nbeam is directed at the object, which reflects the rays onto the
\nfilm. The interference of the rays is captured on the film.<\/p>\n
To reiterate, in greater detail: the laser directs rays
\ntowards a beam splitter. Beam A continues straight ahead, while
\nBeam B is diverted. Reference Beam A is reflected by a mirror and
\nenlarged with lenses before continuing onto the film. Object Beam
\nB is diverted towards a mirror and enlarged by lenses, projecting
\nrays onto the object which is to be recorded. The rays are
\nreflected onto the film as well. Before reaching the film, the
\ntwo beams create an interference pattern, and this pattern is
\nwhat is captured by the film.<\/p>\n
All light waves reflected from the object interact with the
\nreference beam and are recorded on the film. Once the film is
\ndeveloped, the interference pattern is turned into a hologram,
\nwhich is a three-dimensional record of the light waves reflected
\nby the object.<\/p>\n
There are two main kinds of holographic images. The
\ntransmission hologram is created by projecting laser generated
\nreference beams towards the film. The beam projected towards the
\nfilm and on to viewers diffracts when it hits the film. The
\ndiffracted beam projects different wavelengths of light. Hence,
\nviewers see the object formed by different configurations of
\nthese light rays. The complex combination of light waves creates
\nboth a horizontal and a vertical parallax. As you change your
\nviewing position you perceive the object from different angles of
\nthe rays, and the object appears in three dimensions.<\/p>\n
While you can only view the laser transmission hologram using
\nlaser light, a rainbow hologram can be mass produced. Usually,
\nthe vertical element of the three dimensional effect is reduced
\nby masking the hologram. A horizontal slit eliminates the
\nvertical parallax from the hologram. Through the horizontal slit,
\nthe laser constructs a second hologram, called a rainbow
\nhologram. This hologram only has horizontal parallax, and the
\nthree dimensional effect can only be seen from side to side. A
\nmulticolored spectrum of light is instead projected vertically.
\nSo, as you move your viewing position up and down, you see the
\nholographic image in different color tones.<\/p>\n
A special emulsion (\"photoresist\") is used to record the
\nhologram, which renders the interference pattern of the hologram
\nas ultrafine ridges. Through a process of electrolysis using
\nnickel, a mold is created. By means of the mold, the pattern is
\ntransferred onto a plastic sheet. It is then coated with
\naluminum. The mirror-like surface of the sheet reflects white-
\nlight waves, creating a holographic image of the object.<\/p>\n
As holograms can not yet be duplicated, the same process needs
\nto be repeated for every single reproduction.<\/p>\n
-- Amir Sidharta<\/p>", "url": "https:\/\/jawawa.id\/newsitem\/whats-the-modus-operandi-of-holograms-1447893297", "image": "" }, "sponsor": "Okusi Associates", "sponsor_url": "https:\/\/okusiassociates.com" }