The images are sent directly onto the retina

US firm Microvision has developed a system that projects lasers onto the retina, allowing users to view images on top of their normal field of vision.

It could allow surgeons to get a bird's eye view of the innards of a patient, offer military units in the field a view of the entire battlefield and provide mechanics with a simulation of the inside of a car's engine.

The system uses tiny lasers, which scan their light onto the retina to produce the entire range of human vision, reported the journal of the Institute of the Electrical and Electronics Engineers, IEEE Spectrum.

Eye for repair

"I was amazed by what I saw," said Harry Goldstein, senior associate editor of IEEE Spectrum.

"Seeing is believing and seeing these images floating in front of you at about arms length distance is pretty incredible."

Service technicians use it so that they can work on an engine and their view is superimposed on what they are seeing

Harry Goldstein, IEEE Spectrum

The system has been years in the making and has only just come into commercial usage in the car industry, with Honda using it in its dealerships.

The first generation product, called the Nomad Expert Technician System, consists of a wireless computer and a hi-tech monocle, costing around $4,000.

The monocle is worn in front of the eye and reflects scanned laser light to the eye allowing mechanics to view car diagnostics and instructions superimposed on their field of vision.

"Service technicians use it so that they can work on an engine and their view is superimposed on what they are seeing," Mr Goldstein told the BBC programme, Go Digital.

"They don't have to get up from what they are doing and go to a separate computer terminal or flick through a manual. They have it right where they need it."

Honda has found that technicians are saving about 40% in terms of the time spent working on engines, saving the company an estimated $2,000 per month per technician.

Surgeons have also tested a version of the system which gives them vital patient data, such as heart rate and blood pressure, as they operate.

Already 100 of the see-through laser-based displays have been shipped to Iraq for use by the US Army's Stryker Brigade.

Safe to use

There are four components to the system - electronics, light sources, scanners and optics.

1: Light projected to scanning mirror 2: Pupil expander enlarges the image 3: Lens focuses the image 4: Image reflected onto the retina

The signals contain vital information about the intensity and mix of the colours which can be reproduced by the light source.

The scanner then applies the image to the retina. It is made up of a tiny mirror that sweeps the light beam until a full image appears to the user.

The scanned beam is focused onto an optical element called an exit pupil expander. When the light from the expander is collected by a lens and guided by a mirror and a see-through monocle to the eye, it covers the entire area seen by the pupil.

Microvision say the technology is safe because of very low strength of the laser used.

The power of the light is about a thousandth of a watt," said Mr Goldstein.

"Not only is it low power, but it is also not dwelling in one place on the retina for any period of time. It is sweeping across the retina at a very high rate."

Virtual reality

The military got so-called scanned-beam technology off the ground in the 1980s, producing helmet-mounted displays to improve fighter pilots' field of vision.

Microvision licensed the patent that came out of the research done at the University of Washington and has been working on the system ever since.

There is still work to be done but potentially the system could become second only to tapping into the optic nerve in terms of getting images to the brain.

It could provide three dimensional pictures in perfect colour, able to simulate near or distant objects with complete realism, which could provide gamers with an intense sense of reality.

Within five years, such systems could be incorporated into mobile phones or hand-held computers and appear to the brain as a brightly lit widescreen TV version of what is on the device.

Offshoots of the technology could be put into digital cameras, offering the same viewfinder capabilities of a high quality single lens reflex camera.

Photographers would be able to preview a full-colour image and make focus-control and depth-of-field adjustments much more easily.