What Is Optical Camouflage ?
Optical camouflage is a hypothetical type of active camouflage currently only in a very primitive stage of development. 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. 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. Prototype examples and proposed designs of optical camouflage devices range back to the late eighties at least, and the concept began to appear in fiction in the late nineties.
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.
Head-mounted Displays
An HMD has either one or two small CRT, LCD, LCoS (Liquid Crystal on Silicon), or OLED displays with magnifying lenses embedded in a helmet, glasses or visor. With two displays, the technology can be used to show stereoscopic images by displaying an offset image to each eye. Lenses are used to give the perception that the images are coming from a greater distance, to prevent eye strain. One company, Sensics, makes an HMD with 24 OLED displays, with the lenses designed to combine 12 displays into a seamless image for each eye. Head-mounted displays may also be coupled with head-movement tracking devices to allow the user to "look around" a virtual reality environment naturally by moving the head without the need for a separate controller. Performing this update quickly enough to make the experience immersive requires a great amount of computer image processing. If six axis position sensing (direction and position) is used then the wearer may physically move about and have their movement translated into movement in the virtual environment.
Augmented reality(AR) is a field of computer rearch which deals with the combination of real world and computer generated data. At present, most AR research is concerned with the use of live video imagery which is digitally processed and "augmented" by the addition of computer generated graphics. Advanced research includes the use of motion tracking data, fiducial marker recognition using machine vision, and the construction of controlled environments containing any number of sensors and actuators.
Introduction
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 (highly reflective 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.
Active Camouflage
Active camouflage is a group of camouflage technologies which allow an object to blend into its surroundings by use of panels or coatings capable of altering their appearance, color, luminance and reflective properties. Active camouflage has the potential to achieve perfect concealment from visual detection.
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). If properly positioned in front of the user's eye, the combiner allows the user to perceive both the image enhanced by the computer and light from the surrounding world. This is critical because the computer-generated image and the real-world scene must be fully integrated for the illusion of invisibility to seem realistic. The user has to look through a peephole in this mirror to see the augmented reality.
Conclusion
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. In the next step of our research, an observer would be able to observe the background image from various viewpoints with H.M.P.
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