Optical camouflage uses augmented reality technology and retro-reflective materials to make objects appear invisible. It works by using a video camera to capture the background scene, a computer to process the image, a projector to display the image on the retro-reflective cloak, and a special mirror that allows the wearer to see the projected background. This creates the illusion that the wearer is invisible. Potential applications include helping pilots see runways or surgeons see through their hands. A related concept is mutual telexistence, which allows people in different locations to perceive each other as if in the same place through the use of video cameras and projectors with retro-reflective robots.

1. Optical Camouflage
---towards creating an magical invisible world
A PAPER PRESENTED UNDER THE TOPIC
Nanotechnology
By:
P.Lavanya, III B.Tech , ECE . K.Bhargavi III B.Tech, ECE.
SIDDARTHA INSTITUTE OF SCIENCE AND TECHNOLOGY
PUTTUR, CHITTOOR DISTRICT.

2. Abstract: the fundamentals of optical physics. To be
clearer, our concept delivers similar experiences
Mankind always sensed the milestones of science
to that of harry potter’s invisibility cloak.
as wonders. Designing of things and applications that
the humans may not even dream of had become the Contents:
ultimate aim of the scientists and researchers. Here,
we present one of such creative and awesome Principle
technology that emerged as a landmark in the field of
Altered Reality
artificial intelligence.
The Cloak & Video Camera
In this unique paper, we aim to explain how
to turn any living or non living object invisible. This The Computer
is not a magic and is made possible by the revolution
The Projector & Combiner
in the field of optical physics. The application of
aug-mented reality and nanotechnology are the The Complete System
pillars behind this concept. A new concept called
Head Mounted Displays
retro reflection, made possible thr-ough nano
technology is also demonstrated. The entire set up Real World Applications
and the process behind this including the projector,
digital computer and the cloak made of weeds is Conclusion
elucidated very clearly by including some real life
and commercial applications. Finally we discussed
the concept of head mounted displays, which made Principle:
tele-conferencing an ease and also made the same
If you project background image on to the
person’s presence at multiple places at the same time.
masked object, you can observe the masked object
just as if it were virtually transparent. This shows the
principle of the optical camouflage.
In a single statement, our innovative paper
deals with the concept of optical camouflage, Altered Reality:
which holds the key in making a desired object or
a person, look invisible and can even project a Optical camouflage doesn't work by way of
person at different place at the same time by using magic. It works by taking advantage of something
called augmented-reality technology -- a type of
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3. technology that pulls graphics out of your television Let's look at each of these components in greater
screen or computer display and integrate them into detail
real-world environments.
The Cloak:
Augmented-reality systems add computer-
generated information to a user's sensory perceptions. The cloak that enables optical camouflage to work
Imagine, for example, that you're walking down a is made from a special material known as retro-
city street. As you gaze at sites along the way, reflective material. A retro-reflective material is
additional information appears to enhance and enrich covered with thousands and thousands of small
your normal view. Perhaps it's the day's specials at a beads. When light strikes one of these beads, the light
restaurant or the show times at a theater or the bus rays bounce back exactly in the same direction from
schedule at the station. What's critical to understand which they came.
here is that augmented reality is not the same as
A rough surface creates a diffused reflection
virtual reality, while virtual reality aims to replace the
because the incident (incoming) light rays get
world, augmented reality merely tries to supplement
scattered in many different directions. A perfectly
it with additional, helpful content.
smooth surface, like that of a mirror, creates what is
Most augmented-reality systems require that known as a specular reflection -- a reflection in which
users look through a special viewing apparatus to see incident light rays and reflected light rays form the
a real-world scene enhanced with synthesized exact same angle with the mirror surface. In retro-
graphics. They also require a powerful computer. reflection, the glass beads act like prisms, bending
Optical camouflage requires these things, as well, but the light rays by a process known as refraction. This
it also requires several other components. Here's causes the reflected light rays to travel back along the
everything needed to make a person appear invisible: same path as the incident light rays.
 A garment made from highly reflective The result: An observer situated at the
material light source receives more of the reflected light and
therefore sees a brighter reflection. Retro-reflective
 A video camera
materials are actually quite common. Traffic signs,
 A computer road markers and bicycle reflectors all take advantage
of retro-reflection to be more visible to people
 A projector driving at night. Movie screens used in most modern
commercial theaters also take advantage of this
 A special, half-silvered mirror called a
material because it allows for high brilliance under
combiner
dark conditions. In optical camouflage, the use of
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4. retro-reflective material is critical because it can be The Video Camera:
seen from far away and outside in bright sunlight --
two requirements for the illusion of invisibility. The retro-reflective garment doesn't actually
make a person invisible -- in fact, it's perfectly
opaque. What the garment does is create an illusion
of invisibility by acting like a movie screen onto
which an image from the background is projected.
Capturing the background image requires a video
camera, which sits behind the person wearing the
cloak. The video from the camera must be in a digital
format so it can be sent to a computer for processing.
Computer:
All augmented-reality systems rely on
powerful computers to synthesize graphics and then
superimpose them on a real-world image. For optical
camouflage to work, the hardware/software combo
must take the captured image from the video camera,
calculate the appropriate perspective to simulate
reality and transform the captured image into the
image that will be projected onto the retro-reflective
material.
The Projector:
The modified image produced by the
computer must be shone onto the garment, which acts
like a movie screen. A projector accomplishes this
task by shining a light beam through an opening
controlled by a device called an iris diaphragm. An
iris diaphragm is made of thin, opaque plates, and
turning a ring changes the diameter of the central
opening. For optical camouflage to work properly,
this opening must be the size of a pinhole. Why? This
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5. ensures a larger depth of field so that the screen (in
this case the cloak) can be located any distance from
the projector.
The Combiner:
The system requires a special mirror to both
reflect the projected image toward the cloak and to let
light rays bouncing off the cloak return to the user's
eye. This special mirror is called a beam splitter, or a
combiner -- a half-silvered mirror that both reflects
light (the silvered half) and transmits light (the
transparent half). If properly positioned in front of the
Now let's put all of these components together
user's eye, the combiner allows the user to perceive
to see how the invisibility cloak appears to make a
both the image enhanced by the computer and light
person transparent. The diagram below shows the
from the surrounding world. This is critical because
typical arrangement of all of the various devices and
the computer-generated image and the real-world
pieces of equipment.
scene must be fully integrated for the illusion of
invisibility to seem realistic. The user has to look
through a peephole in this mirror to see the
augmented reality.
Once a person puts on the cloak made with the
retro-reflective material, here's the sequence of
events:
 A digital video camera captures the scene
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6. behind the person wearing the cloak. practical use if the user had to stand in a fixed
 The computer processes the captured image location. That's why most systems require that the
and makes the calculations necessary to user carry the computer on his or her person, either in
adjust the still image or video so it will look a backpack or clipped on the hip. It's also why most
realistic when it is projected. systems take advantage of head-mounted displays, or
 The projector receives the enhanced image HMDs, which assemble the combiner and optics in a
from the computer and shines the image wearable device.
through a pinhole-sized opening onto the
There are two types of HMDs: optical see-
combiner.
through displays and video see-through displays.
 The silvered half of the mirror, which is
Optical see-through displays look like high-tech
completely reflective, bounces the projected
goggles, sort of like the goggles Cyclops wears in the
image toward the person wearing the cloak.
X-Men comic books and movies. These goggles
The cloak acts like a movie screen, reflecting
provide a display and optics for each eye, so the user
light directly back to the source, which in
sees the augmented reality in stereo. Video see-
this case is the mirror.
through displays, on the other hand, use video-
Light rays bouncing off of the cloak pass through mixing technology to combine the image from a
the transparent part of the mirror and fall on head-worn camera with computer-generated graphics.
the user's eyes. Remember that the light rays
In this arrangement, video of the real world
bouncing off of the cloak contain the image
is mixed with synthesized graphics and then
of the scene that exists behind the person
presented on a liquid-crystal display. The great
wearing the cloak.
advantage of video see-through displays is that
The person wearing the cloak appears invisible virtual objects can fully obscure real-world objects
because the background scene is being displayed onto and vice versa.
the retro-reflective material. At the same time, light
rays from the rest of the world are allowed reach the
user's eye, making it seem as if an invisible person
exists in an otherwise normal-looking world.
Head-mounted Displays:
Of course, making the observer stand
behind a stationary combiner is not very pragmatic --
no augmented-reality system would be of much
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7. The scientists who have developed optical-
camouflage technology are currently perfecting a
variation of a video see-through display that brings
together all of the components necessary to make the
invisibility cloak work.
Real-World Applications:
One of the most promising applications of this
While an invisibility cloak is an interesting application
technology, however, has less to do with making
of optical camouflage, it's probably not the most usefu l one.
objects invisible and more about making them
Here are some practical ways the technology might
visible. The concept is called mutual
be applied:
telexistence: working and perceiving with the
Pilots landing a plane could use this feeling that you are in several places at once.
technology to make cockpit floors Here's how it works:
transparent. This would enable them to see
Human user A is at one location while his
the runway and the landing gear simply by
telexistence robot A is at another location
glancing down.
with human user B.
Doctors performing surgery could use
Human user B is at one location while his
optical camouflage to see through their
telexistence robot B is at another location
hands and instruments to the underlying
with human user A.
tissue.
Both telexistence robots are covered in retro-
Providing a view of the outside in
reflective material so that they act like
windowless rooms is one of the more
screens.
fanciful applications of the technology, but
one that might improve the psychological With video cameras and projectors at each
well-being of people in such environments. location, the images of the two human users
are projected onto their respective robots in
Drivers backing up cars could benefit one
the remote locations.
day from optical camouflage. A quick
glance backward through a transparent rear This gives each human the perception that he is
hatch or tailgate would make it easy to know working with another human instead of a robot.
when to stop.
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8. Conclusion:
Through optical camouflage we may step
into a more advanced phase of today’s
teleconferencing. In future we may have a New
World where we can have the same person at
different places at the same time.
.
References:
[1].M. Shiro ,Ghost in the shell,Kodansya,1991
[2]. http://www.star.t.u-tokyo.ac.jp
[3]. http://en.wikipedia.org/wiki/Cloaking_device.
[4]. http://en.wikipedia.org/wiki/Active-camouflage
[5].http://www.wisegeek.com/what-is-optical-
camouflage.htm.
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