18-04-2010, 08:42 PM
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OPTICAL CAMOUFLAGE
PRESENTED BY
A.ABHINAYA, M. AYESHA,
III year (ECE)
SIDDHARTH INSTITUTE OF ENGINEERING AND TECHOLOGY,
NARAYANAVANAM ROAD, PUTTUR.
Abstract:
This paper describes a kind of active camouflage system named Optical Camouflage. Initially, Camouflage is made understood and then the theory of optical camouflage is developed. Optical Camouflage uses the Retro-reflective Projection Technology, a projection based augmented“reality system, composed of a projector with a small iris and a retro reflective screen. The concept of optical camouflage is straightforward: to create the illusion of invisibility by covering an object with something that projects the scene directly behind that object. This system was conceived with the primary view in mind of concealing stationary or moving objects such as men, vehicles, or aircraft from view and has practical military, law enforcement, and security applications.
Introduction:
Various methods have been proposed to integrate the visual space. In the field of Mixed Reality, one of the most popular topics is about displaying a virtual object into real world .However making objects virtually transparent, like in H.G. Wellsâ„¢ 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.
Camouflage:
Camouflage is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples include a tiger's stripes and Battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word 'camoufler' meaning 'to disguise'.
Natural camouflage:
In nature, there is a strong evolutionary pressure for animals to blend into their environment or conceal their shape; for prey animals to avoid predators and for predators to be able to sneak up on prey. Natural camouflage is one method that animals use to meet these aims.
Anolis caroliensis showing blending
Camouflage and counter shading
Military camouflage:
These were intended to daunt the enemy, attract recruits, foster unit cohesion, and allow easier identification of units in the fog of war. The British in India in 1857 were forced by casualties to dye their red tunics to neutral tones, initially a muddy tan called khaki. The United States was quick to follow the British, going khaki in the same year. Later in 20th century, digital camouflage patterns have been experimented on helicopters, battledresses & other vehicles. It is termed "digital" because much of the design was done on a computer and unlike other camouflage patterns; it is blocky and appears almost pixelated.
Theory of Camouflage:
MacKay's statement above remains one of the most important elements in the theory of camouflage †an exact match with the environment's colours is less crucial than the patterning of the regions of colour themselves. Ideally, camouflage should be made to break up and thereby conceal the structural lines of the object which it hides. Thus, the patterns often seen on camouflage clothing, masking cloth and vehicle paints are carefully constructed to deceive the human eye by breaking up the boundaries that define sharp edges and human silhouettes. This is called high difference or disruptive camouflage. This mix of blending and disruptive patterns is called coincident disruption - the aim of modern military camouflage. The opposite of camouflage is making a person or object more visible and easier to recognize, for example with retro reflectors and high-visibility clothing...
What is Optical Camouflage
Optical camouflage is a kind of active camouflage. This idea is very simple. If you project Background image onto the masked object, you can observe the masked object just as if it were virtually transparent. 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. The most intriguing 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 an external projector which projects the image onto a person wearing a special retro reflective coat. This can lead to different results depending on the quality of the camera, the projector, and the coat, but by the late nineties, convincing illusions were created. The downside is the large amount of external hardware required, along with the fact that the illusion is only convincing when viewed from a certain angle. 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. 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 of a human observer, more sophisticated machinery would be necessary to create perfect illusions in other electromagnetic bands, such as 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.
Fig.1
Fig. 2
This shows the principle of the optical camouflage using Xâ„¢tal vision. You can select camouflaged object to cover with retro reflector. Moreover, to project a stereoscopic image, the observer looks at the masking object more transparent.
Fig 3
In the above shown figure, this transparent cloak makes you see as if the cloak is transparent by projecting the shooting image behind the person onto the cloak i.e. it looks like three men walking behind are seen through the body of the person. So, actually, the cloak is not really transparent.
How does it work
First, putting the video camera behind the person in the cloak, and capturing his background. Then, projecting the captured image onto the cloak from the projector. So, if you see from the peephole, you will see as if the cloak is transparent. Because the image is projected by the technology called Retro-reflective Projection Technology (RPT), you can see the reflection only on the cloak and clearly even in brightness.
Fig .4
Cloakâ„¢s Secret!
This Cloaking System is designed to conceal an object from view by placing a thin video screen between the observer and the object being concealed and at the same time presenting a full colour image of the background on the screen for view by the observer, thus creating the illusion that the object is not there. The special material is used as screen for RPT. Thatâ„¢s different from the screen in the cinemas. This material is called ËœRetro-reflective Materialâ„¢, and also used for the cloak. The surface of Retro-reflective Material is covered with very small beads. If the light strikes the material, the light reflects only in the same direction as it has come. So, the image is reflected clearly even in brightness. Optical camouflage requires the viewer to be in position with a sensor. The illusion is broken if you are a few meters off the mark, so this isn't exactly ready for military use. This can be used for two purposes. The first of which being showing a representation of something behind an object, on top of said object. The second is to actually change what you're looking at. This is accomplished with a reflective coating applied to the objects to receive the camouflage. Mirrors work even better. The selected background is filmed, and then projected back onto the source exactly. This is nearly unnoticeable until a highly reflective surface passes by. You then see only a little more than a shimmering outline. In fact, we can find a lot of things using Retro-reflective Material around you. Traffic signs, bicycleâ„¢s reflector and the lighting part of the raincoat are made from Retro reflective Material. As like the transparent cloak, it can be seen from far away because they shine brightly by little light of the cars.
Retro-reflective Projection Technology (RPT):
Now that we Ëœve seen how does optical camouflage works using RPT & Xâ„¢stal vision, let us illustrate RPT. When using a See-Through Head-mounted Display (STHMD) to merge virtual and real environments, the operator may see the image of a virtual object that is meant to be located behind a real object. This contradicts our intuition of depth, since the projected image of an object located behind another object in one's field of view will be obstructed at least partially. This depth cue is called occlusion, and is critical for the effectiveness of the presentation of virtual objects in three dimensions. To solve the occlusion contradiction problem, we developed RPT. The three key techniques of RPT are the followings:
¢To use an object covered by retro-reflective material as a screen;
¢To place a projector into a position optically conjugated with the observer's eye by using a half-mirror;
¢To make the projector's iris as small as possible (by using a pinhole).
Each of these points provides the following advantages, respectively:
Fig.5
Fig.6
Fig.5 and Fig.6 shows the principles of RPT.
The image of a virtual object is projected
Through a pinhole. The projected image is reflected by the half-mirror on a right angle and then retro-reflected by the retro-reflective screen.
Fig.7 optical camouflaged hap tic display
Fig 7 shows the hap tic display (real object) hiding the virtual object, but Optical Camouflage techniques permit to make the hap tic display to become transparent. However the operatorâ„¢s hand is not made transparent, which implies that it is possible to use this technology.
Applications:
¢Used in Stealth technology, to make airplane invisible to Radar
¢Utilization of this technology also has three important secondary energy saving by-products
:
(a) As a security instrument it can protect national strategic resources from theft and
sabotage by concealing both the resource and a much reduced security force from view by either presenting the natural background on the screen or by presenting an artificial image of the resource on the screen.
(b) Its variable reflective capability could assist in heating or cooling the facility, thus realizing considerable energy savings; and
© Environmental enhancement of industrial facilities using Chameleon screens in lieu of artificial buildings/landscaping and enhancement of working spaces allowing artificial scenes on the wall and/or outside views without the need for windows.
¢Technical Advantages -
The need for the camouflage aspect of this system arises out of the present state of the art of military camouflage in the visible light spectrum which is generally limited to techniques involving painting, colouring, and/or contour shaping to allow an object to better blend in with the background; such methods do little to conceal moving objects as their appearance must be constantly controlled from the viewpoint of the observer to blend in with the changing background.
¢Others-
1. For example, if this technique is used in cockpit for making the floor transparent at landing, the pilot can land safely with seeing runway. Also, used for other vehicles like car. If you can see through the back of car, you will put the car into the garage successfully. This technique was invented from the study that skilfully mixing the real world and the world made artificially, and trying to let your life and work convenient.
2. The idea appears in many fictional works, such as the William Gibson novel Necromancer, where it is referred to as a "polychromatic suit," but achieved recognition in the successful James Bond movie. Die Another Day. The car of James bond, Aston Martin Vanquish V-12 is equipped with all the usual refinements including front-firing rockets, hood mounted guns, and passenger ejector seat in homage to the original Aston Martin DB5 driven by Bond in Gold finger. The car was also equipped with an adaptive camouflage device that allowed it to become invisible to the naked eye at the push of a button (although it could still be detected in infrared.)
Similar camouflage is also used by the creatures in the Predator movies, though in that case light is bent around the camouflage.
¢Optical Camouflage can be used on surgical globes or equipments so they don™t block surgeon™s view during delicate operations.
¢Conclusion:
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. 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. 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.
Bibliography:
google.com
ziddu.com
http://seminarsprojects.in
OPTICAL CAMOUFLAGE
PRESENTED BY
A.ABHINAYA, M. AYESHA,
III year (ECE)
SIDDHARTH INSTITUTE OF ENGINEERING AND TECHOLOGY,
NARAYANAVANAM ROAD, PUTTUR.
Abstract:
This paper describes a kind of active camouflage system named Optical Camouflage. Initially, Camouflage is made understood and then the theory of optical camouflage is developed. Optical Camouflage uses the Retro-reflective Projection Technology, a projection based augmented“reality system, composed of a projector with a small iris and a retro reflective screen. The concept of optical camouflage is straightforward: to create the illusion of invisibility by covering an object with something that projects the scene directly behind that object. This system was conceived with the primary view in mind of concealing stationary or moving objects such as men, vehicles, or aircraft from view and has practical military, law enforcement, and security applications.
Introduction:
Various methods have been proposed to integrate the visual space. In the field of Mixed Reality, one of the most popular topics is about displaying a virtual object into real world .However making objects virtually transparent, like in H.G. Wellsâ„¢ 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.
Camouflage:
Camouflage is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples include a tiger's stripes and Battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word 'camoufler' meaning 'to disguise'.
Natural camouflage:
In nature, there is a strong evolutionary pressure for animals to blend into their environment or conceal their shape; for prey animals to avoid predators and for predators to be able to sneak up on prey. Natural camouflage is one method that animals use to meet these aims.
Anolis caroliensis showing blending
Camouflage and counter shading
Military camouflage:
These were intended to daunt the enemy, attract recruits, foster unit cohesion, and allow easier identification of units in the fog of war. The British in India in 1857 were forced by casualties to dye their red tunics to neutral tones, initially a muddy tan called khaki. The United States was quick to follow the British, going khaki in the same year. Later in 20th century, digital camouflage patterns have been experimented on helicopters, battledresses & other vehicles. It is termed "digital" because much of the design was done on a computer and unlike other camouflage patterns; it is blocky and appears almost pixelated.
Theory of Camouflage:
MacKay's statement above remains one of the most important elements in the theory of camouflage †an exact match with the environment's colours is less crucial than the patterning of the regions of colour themselves. Ideally, camouflage should be made to break up and thereby conceal the structural lines of the object which it hides. Thus, the patterns often seen on camouflage clothing, masking cloth and vehicle paints are carefully constructed to deceive the human eye by breaking up the boundaries that define sharp edges and human silhouettes. This is called high difference or disruptive camouflage. This mix of blending and disruptive patterns is called coincident disruption - the aim of modern military camouflage. The opposite of camouflage is making a person or object more visible and easier to recognize, for example with retro reflectors and high-visibility clothing...
What is Optical Camouflage
Optical camouflage is a kind of active camouflage. This idea is very simple. If you project Background image onto the masked object, you can observe the masked object just as if it were virtually transparent. 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. The most intriguing 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 an external projector which projects the image onto a person wearing a special retro reflective coat. This can lead to different results depending on the quality of the camera, the projector, and the coat, but by the late nineties, convincing illusions were created. The downside is the large amount of external hardware required, along with the fact that the illusion is only convincing when viewed from a certain angle. 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. 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 of a human observer, more sophisticated machinery would be necessary to create perfect illusions in other electromagnetic bands, such as 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.
Fig.1
Fig. 2
This shows the principle of the optical camouflage using Xâ„¢tal vision. You can select camouflaged object to cover with retro reflector. Moreover, to project a stereoscopic image, the observer looks at the masking object more transparent.
Fig 3
In the above shown figure, this transparent cloak makes you see as if the cloak is transparent by projecting the shooting image behind the person onto the cloak i.e. it looks like three men walking behind are seen through the body of the person. So, actually, the cloak is not really transparent.
How does it work
First, putting the video camera behind the person in the cloak, and capturing his background. Then, projecting the captured image onto the cloak from the projector. So, if you see from the peephole, you will see as if the cloak is transparent. Because the image is projected by the technology called Retro-reflective Projection Technology (RPT), you can see the reflection only on the cloak and clearly even in brightness.
Fig .4
Cloakâ„¢s Secret!
This Cloaking System is designed to conceal an object from view by placing a thin video screen between the observer and the object being concealed and at the same time presenting a full colour image of the background on the screen for view by the observer, thus creating the illusion that the object is not there. The special material is used as screen for RPT. Thatâ„¢s different from the screen in the cinemas. This material is called ËœRetro-reflective Materialâ„¢, and also used for the cloak. The surface of Retro-reflective Material is covered with very small beads. If the light strikes the material, the light reflects only in the same direction as it has come. So, the image is reflected clearly even in brightness. Optical camouflage requires the viewer to be in position with a sensor. The illusion is broken if you are a few meters off the mark, so this isn't exactly ready for military use. This can be used for two purposes. The first of which being showing a representation of something behind an object, on top of said object. The second is to actually change what you're looking at. This is accomplished with a reflective coating applied to the objects to receive the camouflage. Mirrors work even better. The selected background is filmed, and then projected back onto the source exactly. This is nearly unnoticeable until a highly reflective surface passes by. You then see only a little more than a shimmering outline. In fact, we can find a lot of things using Retro-reflective Material around you. Traffic signs, bicycleâ„¢s reflector and the lighting part of the raincoat are made from Retro reflective Material. As like the transparent cloak, it can be seen from far away because they shine brightly by little light of the cars.
Retro-reflective Projection Technology (RPT):
Now that we Ëœve seen how does optical camouflage works using RPT & Xâ„¢stal vision, let us illustrate RPT. When using a See-Through Head-mounted Display (STHMD) to merge virtual and real environments, the operator may see the image of a virtual object that is meant to be located behind a real object. This contradicts our intuition of depth, since the projected image of an object located behind another object in one's field of view will be obstructed at least partially. This depth cue is called occlusion, and is critical for the effectiveness of the presentation of virtual objects in three dimensions. To solve the occlusion contradiction problem, we developed RPT. The three key techniques of RPT are the followings:
¢To use an object covered by retro-reflective material as a screen;
¢To place a projector into a position optically conjugated with the observer's eye by using a half-mirror;
¢To make the projector's iris as small as possible (by using a pinhole).
Each of these points provides the following advantages, respectively:
Fig.5
Fig.6
Fig.5 and Fig.6 shows the principles of RPT.
The image of a virtual object is projected
Through a pinhole. The projected image is reflected by the half-mirror on a right angle and then retro-reflected by the retro-reflective screen.
Fig.7 optical camouflaged hap tic display
Fig 7 shows the hap tic display (real object) hiding the virtual object, but Optical Camouflage techniques permit to make the hap tic display to become transparent. However the operatorâ„¢s hand is not made transparent, which implies that it is possible to use this technology.
Applications:
¢Used in Stealth technology, to make airplane invisible to Radar
¢Utilization of this technology also has three important secondary energy saving by-products
:
(a) As a security instrument it can protect national strategic resources from theft and
sabotage by concealing both the resource and a much reduced security force from view by either presenting the natural background on the screen or by presenting an artificial image of the resource on the screen.
(b) Its variable reflective capability could assist in heating or cooling the facility, thus realizing considerable energy savings; and
© Environmental enhancement of industrial facilities using Chameleon screens in lieu of artificial buildings/landscaping and enhancement of working spaces allowing artificial scenes on the wall and/or outside views without the need for windows.
¢Technical Advantages -
The need for the camouflage aspect of this system arises out of the present state of the art of military camouflage in the visible light spectrum which is generally limited to techniques involving painting, colouring, and/or contour shaping to allow an object to better blend in with the background; such methods do little to conceal moving objects as their appearance must be constantly controlled from the viewpoint of the observer to blend in with the changing background.
¢Others-
1. For example, if this technique is used in cockpit for making the floor transparent at landing, the pilot can land safely with seeing runway. Also, used for other vehicles like car. If you can see through the back of car, you will put the car into the garage successfully. This technique was invented from the study that skilfully mixing the real world and the world made artificially, and trying to let your life and work convenient.
2. The idea appears in many fictional works, such as the William Gibson novel Necromancer, where it is referred to as a "polychromatic suit," but achieved recognition in the successful James Bond movie. Die Another Day. The car of James bond, Aston Martin Vanquish V-12 is equipped with all the usual refinements including front-firing rockets, hood mounted guns, and passenger ejector seat in homage to the original Aston Martin DB5 driven by Bond in Gold finger. The car was also equipped with an adaptive camouflage device that allowed it to become invisible to the naked eye at the push of a button (although it could still be detected in infrared.)
Similar camouflage is also used by the creatures in the Predator movies, though in that case light is bent around the camouflage.
¢Optical Camouflage can be used on surgical globes or equipments so they don™t block surgeon™s view during delicate operations.
¢Conclusion:
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. 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. 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.
Bibliography:
google.com
ziddu.com
http://seminarsprojects.in
