Optical Camouflage

SUBMITTED BY:-

SUBRAT KUMAR SWAIN1201109204 (2015-16)Mechanical Engg. PMEC

OPTICAL CAMOUFLAGEOPTICAL CAMOUFLAGE• Optical camouflage is a hypothetical type of

active camouflage. 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 .

• Optical camouflage is a kind of active camouflage which completely envelopes the wearer. It displays an image of the scene on the side opposite the viewer on it, so that the viewer can "see through" the wearer, rendering the wearer invisible.

• 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.

H O W D O E S I T W O H O W D O E S I T W O R K ?R K ?

It works on the principle of Retro-reflective Projection. Creating complete Optical Camouflage across the visible light spectrum would require a coating or suit covered in tiny cameras and projectors, programmed to gather visual data from a multitude of different angles and project the gathered images outwards in an equally large number of different directions to give the illusion of invisibility from all angles.

I N V I S I B I L I T Y C L I N V I S I B I L I T Y C L O A KO A K

• The cloak that enables optical camouflage to work is made from a special material known as retro-reflective material.

• A retro-reflective material is covered with thousands of small beads. When light strikes one of these beads, the light rays bounce back exactly in the same direction from which they came.

• Yes the invisibility cloak which we all have seen in harry porter movie, is now a reality.• This cloak is a type of suit discovered by scientists from University Of Tokyo.

UNIQUE NATURE OF RETRO –REFLECTIVE

MATERIAL

Look at how light reflects off of normal surfaces:

• A rough surface creates a diffused reflection.

• A perfectly smooth surface, like that of a mirror, creates what is known as a specular reflection.

• In retro-reflection, the glass beads act like prisms, bending the light rays by a process known as refraction. This causes the reflected light rays to travel back along the same path as the incident light rays.

WHAT MAKES A CLOAK WHAT MAKES A CLOAK INVISIBLE?INVISIBLE?

• Optical camouflage doesn't work by way of magic. It works by taking advantage of augmented-reality technology .

• Augmented-reality systems add computer-generated information to a user's sensory perceptions.

• Here's everything needed to make an object appear invisible:

• A video camera• A computer • A projector • A special, half-silvered mirror called a

combinerVideo Camera • Video camera sits behind the object with

cloak and captures the background data to be processed by the computer in digital format.

SCHEMATIC DIAGRAM

Continued...Continued...Computer • For optical camouflage to work, computer decrypts

the captured image from the video camera, and calculates the appropriate perspective to simulate reality and transform the captured image into the image that will be projected onto the retro-reflective material.

Projector• This device is positioned optically conjugated with

the observer’s eye by using a combiner.• Then it projects the generated image through iris

diaphragm (can control it’s opening) onto combiner. Combiner • It is a special mirror that reflects the projected

image towards the cloak and lets the reflected light off the cloak to the observer’s eye.

• It contains two parts in two halves, silvered half- reflects light and transparent half – transmits light.

AFTER PUTTING ON THE CLOAK:• A digital video camera captures the scene behind

the object with the cloak. • The computer processes the captured image and

makes the calculations necessary to adjust the still image or video to make it realistic.

• The projector receives the enhanced image from the computer and shines the image through a pinhole-sized opening onto the combiner.

• The silvered half of the combiner, which is completely reflective, bounces the projected image toward the object with the cloak.

• The cloak acts like a movie screen, reflecting light directly back to the source, which in this case is the mirror.

• Light rays bouncing off of the cloak (projected virtual image) pass through the transparent part of the mirror and fall on the user's eye.

• The object with the cloak appears invisible because the background scene is being displayed onto 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.

Advantages & Advantages & ApplicationsApplications

• Uniform for military personnel • Surgical instruments and devices in

medicine field  • Beautification and security of house • Pilots landing a plane could use this

technology to make cockpit floors transparent.

• Drivers backing up cars• To carry out special operations in critical

environment by police• Encourages idea of mutual-telexistence

L i m i t a t i o nThe view point of observer needs to be more practical. At this stage observer has to look through a half-mirror to see the effect .

C O N C L U S I O NC O N C L U S I O NThis was a briefing of a extra-ordinary technology which showed us a way to realise one of our weird fantasy of being invisible. We learnt how it happens and what are the limitations. It’s in a primitive stage and still has a way to go. With coming up of meta-materials, things will get a bit easier. And we may “not” see people around us in our near future.

R E F E R E N C E S• Lee Tamahori, Die Another Day- James Bond• “Optical Camouflage Using Retro-reflective Projection Technology” by Masahiko Inami, Naoki Kawakami, Susumu Tachi, University Of Tokyo• Wikipedia• science.howstuffworks.com• The Indian Express• www.researchgate.net• Google images• www.youtube.com•“Invisibility System Using Image Processing And Optical Camouflage Technology” by Vasireddy Srikanth1 , Pillem Ramesh2 1 Student, Electronics And Communication Engineering, K L University.

THANK YOU

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