29-06-2012, 11:18 AM
OPTICAL CAMOUFLAGE USING RETRO REFLECTIVE PROJECTION TECHNOLOGY
OPTICAL CAMOUFLAGE USING RETRO REFLECTIVE PROJECTION TECHNOLOGY.doc (Size: 466.5 KB / Downloads: 34)
ABSTRACT
This paper describes a kind of active camouflage system named Optical Camouflage. 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. A technology pioneered by scientists at Tachi laboratory, University of Tokyo. Using this technology a person or object can be made partially invisible. It basically captures the image of the background of the object making the masking object virtually transparent.
Retro-reflection technology can find uses in various fields be it aviation medicine, engineering or entertainment. For example in a plane the cockpit can be made partially transparent for pilots to have a better view of runway. Also it can be a boon to entertainment industry and open new gates of virtual reality.
In this paper we also introduce the concept of Telexistence. In this we make a person or object virtually present where he is not. Projecting the image of subject in a remote location over a similar shape and size of object does this.
OPTICAL COMOUFLAGE: AN OVERVIEW
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 HG. 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.
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. 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. If Person B were viewing from a slightly different location, he would simply see Person A wearing a silver garment (left photograph below).
Still, despite its limitations, this is a cool piece of technology. Not only that, but it's also a technology that's been around for a while
HISTORICAL BACKGROUND
History has many evidences, which tells the tale of mankind’s one of the greatest desire, to become invisible. Throughout the past we have fascinated to become something, which cannot be seen. Be it top notch secret services or worlds most powerful army, stealth and invisibility is the key to success. There have been many techniques developed in the past to provide secrecy to army warfare. And apart from that in normal life as well it has been every young minds dream to become invisible.
AUGMENTED REALITY
Augmented-reality systems add computer-generated information to a user's sensory perceptions. Imagine, for example, that you're walking down a city street. As you gaze at sites along the way, additional information appears to enhance and enrich your normal view. Perhaps it's the day's specials at a restaurant or the show times at a theater or the bus schedule at the station. What's critical to understand here is that augmented reality is not the same as virtual reality? While virtual reality aims to replace the world, augmented reality merely tries to supplement it with additional, helpful content.
Tracking and Orientation
The biggest challenge of augmented reality is the need to know where the user is located in reference to his or her surroundings. There's also the additional problem of tracking the movement of users' eyes and heads. A tracking system has to recognize these movements and project the graphics related to the real-world environment the user is seeing at any given moment
Mobile Computing Power
For a wearable augmented reality system, there is still not enough computing power to create stereo 3-D graphics. So researchers are using whatever they can get out of laptops and personal computers, for now. Laptops are just now starting to be equipped with graphics processing units (GPUs).
THEORY OF RETRO REFECTION TECHNOLOGY
Retro-Reflection
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.
Light reflects off of various types of surfaces.A rough surface creates a diffused reflection because the incident (incoming) light rays get scattered in many different directions.
WORKING
1. Video Camera
The retro-reflective garment doesn't actually make a person invisible -- in fact, it's perfectly opaque. What the garment does is create an illusion of invisibility by acting like a movie screen onto which an image from the background is projected.
2 Computers
All augmented-reality systems rely on powerful computers to synthesize graphics and then superimpose them on a real-world image.
3 The Projector
The modified image produced by the computer must be shone onto the garment, which acts like a movie screen. A projector accomplishes this task by shining a light beam through an opening controlled by a device called an iris diaphragm. An iris diaphragm is made of thin, opaque plates, and turning a ring changes the diameter of the central opening.
4 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).
The Complete System
Now let's put all of these components together to see how the invisibility cloak appears to make a person transparent. The diagram below shows the typical arrangement of all of the various devices and pieces of equipment.