Phased Array Optics (PAO) is the as-yet unimplemented idea of creating 2-D arrays of tiny screens programmed to emit light of the specific amplitude and phase necessary to create the illusion of a 3-D image. Implementing this concept would require a lot of computing power; many equations must be solved in realtime in order to create the appropriate optical output. This is beyond the present-day processing capacity of wearable computers, though with advances such as nanoelectronics, portable Phased Array Optics would become practical.

If a large number of mini-screens are used, and their states updated rapidly enough, any 3-D image can be projected. The illusion would be convincing to anyone with the 2-D screen in their line of sight. A room with walls covered in Phased Array Optics could operate like a "holodeck" from Star Trek. A suit covered in flexible PAOs could provide an illusion of invisibility by projecting an image of whatever is behind the user, or give the illusion of the user being very far away or very close to any specific observer. Large Phased Array Optics could simulate the appearance of entire cities, at a level of resolution so fine that the illusion would be preserved even if binoculars were used. A superlarge PAO surrounding a planet could provide the illusion of the planet being anywhere.

Because of the technical difficulty of manufacturing so many tiny screens and their corresponding computational hardware, Phased Array Optics are thought of as a futuristic technology, and often mentioned as an application of advanced nanotechnology. Crude "invisibility suits" have been demonstrated for years, but they are very expensive, and generally provide an illusion only to observers from one point of view. The seminal article on Phased Array Optics was written by Dr. Brian Wowk and is a chapter of the book, Nanotechnology: Speculations on Molecular Abundance. In 2002, MIT's Institute for Soldier Nanotechnologies was formed with a 5-year, $50 million grant from the Army. Part of their agenda is to use PAOs to develop an invisibility suit for the military. Although completion of such a suit before the grant runs out is thought by experts to be unlikely, important strides will be made.

Aside from tapping directly into the optic nerve, Phased Array Optics offer the best possible way to project a virtual reality. Screens at any distance away from the user can be used to simulate objects at nearly any distance. Phased Array Optics will allow the realistic creation of landscapes never before seen on Earth. They will probably be one of the first exciting applications of nanotechnology, with arrival likely sometime between 2010 and 2020.