05-03-2011, 11:55 AM
[attachment=9580]
1. INTRODUCTION
Optical camouflage is a hypo-thetical type of active camouflage currently only in a very primitive stage of development. The idea is relatively straight forward to create the illusion of invisibility by covering an object with something that projects the scene directly behind that object.
First, the person who want be invisible (let’s call his person A) dons a garment. That resembles a hooded raincoat .The garment is made of a special material. Next, an observer (person B) stands before a 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. If person B were viewing from a slightly different location, he would simply see person A wearing a silver garment. Still, despite its limitations, this is a cool piece of technology.
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. 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.
1.1 . CAMOUFLAGE
Camouflage is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples in-clude a tiger's stripes and the battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word 'camoufler' meaning 'to disguise'.
1.2 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.
1.3MILITARY 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 vehi-cles. 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 pixilated.
2. PRINCIPLE
If you project background image on to the masked object, you can observe the masked object just as if it were virtually transparent. This shows the principle of the optical camouflage.
The three key techniques of RPT are the followings
1. To use an object covered by retro-reflective material as a screen;
2. To place a projector into a position optically conjugated with the observer's eye by using a half mirror;
3. To make the projector's iris as small as possible (by using a pinhole).
Each of these points provides the following advantages, respectively Fig. 2.2 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 you can view a block diagram of the above explanation.
3. REQUIREMENTS
The things needed to make a person appear invisible are
• A garment made from highly reflective material
• A video camera
• A computer
• A projector
• A special, half-silvered mirror called a combiner
Let's look at each of these compo-nents in greater detail.
3.1. THE CLOAK
The cloak that enables optical camouflage to work is made from a special material known as retroreflect-ive material. A retro reflective material is covered with thousands and 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. A rough surface creates a diffused reflection because the incident (incoming) light rays get scattered in many different directions. A perfectly smooth surface, like that of a mirror, creates what is known as a specular reflection and a reflection in which incident light rays and reflected light rays form the exact same angle with the mirror surface. 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. The result is an observer situated at the light source receives more of the reflected light and therefore sees a brighter reflection; retro-reflective materials are actually quite common. Traffic signs, road markers and bicycle reflectors all take advantage of retro-reflection to be more visible to people driving at night. Movie screens used in most modern commercial theaters also take advantage of this material because it allows for high brilliance under dark conditions.
In optical camouflage, the use of retro-reflective material is critical because it can be seen from far away and outside in bright sunlight two requirements for the illusion of invisibility
1. INTRODUCTION
Optical camouflage is a hypo-thetical type of active camouflage currently only in a very primitive stage of development. The idea is relatively straight forward to create the illusion of invisibility by covering an object with something that projects the scene directly behind that object.
First, the person who want be invisible (let’s call his person A) dons a garment. That resembles a hooded raincoat .The garment is made of a special material. Next, an observer (person B) stands before a 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. If person B were viewing from a slightly different location, he would simply see person A wearing a silver garment. Still, despite its limitations, this is a cool piece of technology.
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. 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.
1.1 . CAMOUFLAGE
Camouflage is the method which allows an otherwise visible organism or object to remain indiscernible from the surrounding environment. Examples in-clude a tiger's stripes and the battledress of a modern soldier. Camouflage is a form of deception. The word camouflage comes from the French word 'camoufler' meaning 'to disguise'.
1.2 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.
1.3MILITARY 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 vehi-cles. 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 pixilated.
2. PRINCIPLE
If you project background image on to the masked object, you can observe the masked object just as if it were virtually transparent. This shows the principle of the optical camouflage.
The three key techniques of RPT are the followings
1. To use an object covered by retro-reflective material as a screen;
2. To place a projector into a position optically conjugated with the observer's eye by using a half mirror;
3. To make the projector's iris as small as possible (by using a pinhole).
Each of these points provides the following advantages, respectively Fig. 2.2 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 you can view a block diagram of the above explanation.
3. REQUIREMENTS
The things needed to make a person appear invisible are
• A garment made from highly reflective material
• A video camera
• A computer
• A projector
• A special, half-silvered mirror called a combiner
Let's look at each of these compo-nents in greater detail.
3.1. THE CLOAK
The cloak that enables optical camouflage to work is made from a special material known as retroreflect-ive material. A retro reflective material is covered with thousands and 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. A rough surface creates a diffused reflection because the incident (incoming) light rays get scattered in many different directions. A perfectly smooth surface, like that of a mirror, creates what is known as a specular reflection and a reflection in which incident light rays and reflected light rays form the exact same angle with the mirror surface. 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. The result is an observer situated at the light source receives more of the reflected light and therefore sees a brighter reflection; retro-reflective materials are actually quite common. Traffic signs, road markers and bicycle reflectors all take advantage of retro-reflection to be more visible to people driving at night. Movie screens used in most modern commercial theaters also take advantage of this material because it allows for high brilliance under dark conditions.
In optical camouflage, the use of retro-reflective material is critical because it can be seen from far away and outside in bright sunlight two requirements for the illusion of invisibility
