What Is Optical Camouflage ?
Optical camouflage is a hypothetical type of
active camouflage currently only in a very primitive stage of development. The
idea is relatively straightforward: to create the illusion of invisibility by
covering an object with something that projects the scene directly behind that
object. Although optical is a term that technically refers to all forms of
light, most proposed forms of optical camouflage would only provide
invisibility in the visible portion of the spectrum. Prototype examples and
proposed designs of optical camouflage devices range back to the late eighties
at least, and the concept began to appear in fiction in the late nineties.
Creating a truly
realistic optical illusion would likely require Phase Array Optics, which would
project light of a specific amplitude and phase and therefore provide even
greater levels of invisibility. We may end up finding optical camouflage to be
most useful in the environment of space, where any given background is
generally less complex than earthly backdrops and therefore easier to record,
process, and project.
Head-mounted Displays
An HMD has either one
or two small CRT, LCD, LCoS (Liquid Crystal on Silicon), or OLED displays with
magnifying lenses embedded in a helmet, glasses or visor. With two displays, the
technology can be used to show stereoscopic images by displaying an offset
image to each eye. Lenses are used to give the perception that the images are
coming from a greater distance, to prevent eye strain. One company, Sensics,
makes an HMD with 24 OLED displays, with the lenses designed to combine 12
displays into a seamless image for each eye. Head-mounted displays may also be
coupled with head-movement tracking devices to allow the user to "look
around" a virtual reality environment naturally by moving the head without
the need for a separate controller. Performing this update quickly enough to
make the experience immersive requires a great amount of computer image
processing. If six axis position sensing (direction and position) is used then
the wearer may physically move about and have their movement translated into
movement in the virtual environment.
Augmented reality(AR)
is a field of computer rearch which deals with the combination of real world
and computer generated data. At present, most AR research is concerned with the
use of live video imagery which is digitally processed and
"augmented" by the addition of computer generated graphics. Advanced
research includes the use of motion tracking data, fiducial marker recognition
using machine vision, and the construction of controlled environments
containing any number of sensors and actuators.
Introduction
Optical camouflage
delivers a similar experience to Harry Potter's invisibility cloak, but using
it requires a slightly more complicated arrangement. First, the person who
wants to be invisible (let's call her Person A) dons a garment that resembles a
hooded raincoat. The garment is made of a special material (highly reflective
material). Next, an observer (Person B) stands before Person A at a specific
location. At that location, instead of seeing Person A wearing a hooded
raincoat, Person B sees right through the cloak, making Person A appear to be
invisible. The photograph on the right below shows you what Person B would see.
Active Camouflage
Active camouflage is a
group of camouflage technologies which allow an object to blend into its
surroundings by use of panels or coatings capable of altering their appearance,
color, luminance and reflective properties. Active camouflage has the potential
to achieve perfect concealment from visual detection.
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 user's eye, the combiner allows the user
to perceive both the image enhanced by the computer and light from the
surrounding world. This is critical because the computer-generated image and
the real-world 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.
Conclusion
The weak point of this
technique is that the observer needs to look through a half-mirror. The current
system needs a half-mirror and projectors, which were fixed on the ground. In
the next step of our research, an observer would be able to observe the
background image from various viewpoints with H.M.P.
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