Optical Camouflage

Y.Jyothsna Devi S.L.A.Sindhu

¾ B.Tech E.C.E Shri Vishnu engineering college for women

Abstract stationary or moving objects such as men, vehicles, or aircraft from view and has practical This paper describes a kind of active military, law enforcement, and security applications. camouflage system named Optical Camouflage. Initially, Camouflage is made understood and 1. Introduction then the theory of optical camouflage is developed. Since the beginning of time, man Invisibility has been on human wish list, at least and all other types of life have used camouflage. since the advent of fictious idea of invisibility It can be used offensively or defensively. of H.G.Wells. With the recent advances of Optical Camouflage uses the Retro-reflective optics and computing and the recent advents of flexible electronics, such as liquid crystal Projection Technology, a projection based display, that would allow the back ground augmented–reality system, composed of a image to be displayed on the material itself; projector with a small iris and a retro reflective however this elusive goal is no longer purely screen Optical camouflage using Meta imaginary. materials. Three professors at university of Tokyo created a prototypical camouflage system in which a This is accomplished by manipulating the paths video camera takes a shot of the back ground traversed by light through an optical material. and displays it on the cloth using an external Optical camouflage is a hypothetical type of projector. It can reflect the images even when active camouflage currently only in a very the material is wrinkled. It is an application of primitive stage of development. The idea is the optical camouflage and is called the relatively straightforward: to create the illusion invisibility cloak. of invisibility by covering an object with This proto type uses an external camera placed something that projects the scene directly behind the cloak to record a scene, which it then behind that object. This system was conceived transmits to a computer for image processing. with the primary view in mind of concealing The computer feeds the image onto an external projector which projects the image onto a person wearing a special retro reflective coat. Research is now being carried out to implement this in nanotechnology. 2. Camouflage and active camouflage

Camouflage is a method of crypsis (hiding). The word camouflage comes from the French word 'camoufler' meaning 'to disguise'. It allows an otherwise visible organism or object to remain unnoticed, by blending with its environment. The theory of camouflage covers the various strategies which are used to achieve this effect. Examples of camouflage can be seen through the ages. It can evidently be seen in animals and in the military uniforms. The transfer of camouflage patterns from military to exclusive civilian use, is a relatively recent 3. Optical camouflage - An over view: phenomenon. Active camouflage or adaptive camouflage is a group of camouflage Optical camouflage is a kind of active technologies which allow an object to blend into camouflage which completely envelopes the its surroundings by use of panels or coatings wearer. It displays an image of the scene capable of altering their appearance, color, opposite the viewer on it so that the viewer can luminance and reflective properties. Active see through the wearer, rendering the wearer camouflage has the capacity to provide perfect invisible. The idea is relatively straight forward: concealment from visual detection to create the illusion of invisibility by covering Active camouflage provides concealment in the object with something that projects the two important ways: firstly, it makes the scene directly behind that object. This would camouflaged object appear not merely similar to make the object virtually transparent. its surroundings, but effectively invisible through the use of mimicry; secondly, active Various methods have been proposed to camouflage changes the appearance of the integrate the visual space. In the field of Mixed object as changes occur in the background. Reality, one of the most popular topics is about Ideally, active camouflage mimics nearby displaying a virtual object into real world objects as well as objects as distant as the .However making objects virtually transparent, horizon. like in H.G. Wells’ “Invisible Man” can also be seen as dream of human being. In this paper, we describe what could be called a camouflage technique named Optical Camouflage. The most intriguing prototypes of optical camouflage yet have been created by the Tachi Lab at the University of Tokyo, under the supervision of professors Susumu Tachi, Masahiko Inami and Naoki Kawakami. Their prototype uses an external camera placed behind the cloaked object to record a scene, which it then transmits to a computer for image processing. The computer feeds the image into of a human observer, more sophisticated an external projector which projects the image machinery would be necessary to create perfect onto a person wearing a special retro reflective illusions in other electromagnetic bands, such as coat. the infrared band. Sophisticated target-tracking software could ensure that the majority of computing power is focused on projecting false images in those directions where observers are most likely to be present, creating the most realistic illusion possible. 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. 4. Working of optical camouflage:

This can lead to different results depending on Optical camouflage takes advantage of a the quality of the camera, the projector, and the technology called augmented reality. The coat, but by the late nineties, convincing augmented technology is a field of computer illusions were created. The downside is the research which deals with the combination of large amount of external hardware required, real world and computer generated data. The along with the fact that the illusion is only optical camouflage is much to say a mixed convincing when viewed from a certain angle. reality application. Creating complete optical camouflage across the visible spectrum would require a coating or suit Here the procedure involves a set of apparatus. 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. For a surface subject to bending like a flexible suit, a massive amount of computing power and embedded sensors would be necessary to continuously project the correct images in all directions. This would almost certainly require sophisticated nanotechnology, as our computers, projectors, and cameras are not yet miniaturized enough to meet these conditions. Although the suit described above would provide a convincing illusion to the naked eye 4.1. Requirements:

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

Video Camera: 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: Combiner: All augmented-reality systems rely on powerful A special mirror to both reflect the projected computers to synthesize graphics and image toward the cloak and to let light rays then superimpose them on a real-world image. bouncing off the cloak return to the user's eye. For optical camouflage, the Computer must take This special mirror is called a beam splitter, or a the image from the video camera; calculate the combiner. The combiner allows the user to appropriate perspective to simulate reality to be perceive both the image enhanced by the projected onto the retro-reflective material. computer and light from the surrounding world. Projector: For optical camouflage, the central opening 6. REAL WORLD APPLICATIONS: must be the size of a pinhole. This ensures a larger depth of field so that the cloak can be located any distance from the projector.

• Pilots landing a plane could use this technology to make cockpit floors transparent. This would enable them to see the runway and the landing gear simply by 7. Advantages glancing down. Optical Camouflage can be used on surgical • Doctors performing surgery could use globes or equipments so they don’t block optical camouflage to see through their surgeon’s view during delicate operations. hands and instruments to the underlying tissue. In aviation, cockpit floors could be made invisible to assist the pilot in landing. • Providing a view of the outside in windowless rooms is one of the more 8. Metamaterials cloaking: fanciful applications of Optical Camouflage. Metamaterials cloaking is the science of • Drivers backing up cars could benefit one applying metamaterials to achieve invisibility- day from optical camouflage. A quick cloaking. This is accomplished by manipulating glance backward through a transparent rear the paths traversed by light through an optical would make it easy to know when to stop. material. Metamaterials direct and control the propagation and transmission of specified parts of the light spectrum and could be utilized to render an object seemingly invisible. Metamaterials cloaking, derived from transformation optics, describes the process of shielding something from view by controlling electromagnetic radiation. Objects in the defined location are still present, but incident waves are guided around them without being affected by the object itself.

9. Research

Other theories of cloaking discuss various science and research based theories for producing an electromagnetic cloak of invisibility. Theories presented employ transformation optics, event cloaking, dipolar scattering cancellation, tunneling light transmittance, sensors and active sources, and sacoustic cloaking.

10. References [1]http://science.howstuffworks.com/invisibili [4]http://www.seminarprojects.com/Thread- ty-cloak5.htm optical-camouflage-a-seminar-report [2]http://www.wisegeek.com/what-is-optical- camouflage.htm [3]http://en.wikipedia.org/wiki/Metamaterial _cloaking