Eccescopy, part 17

On the subject of eye contact, I’ve been thinking that it should be possible, without waiting for the future technology of electronic contact lenses, to create an ambiscope that does not place any visible impediment at all in front of your pupil — not even something on the order of eyeglasses.

The form factor I’m thinking of might look something like this:


The ear-piece that you see in the above image would extend out from a module that clips to one’s ear, much like the Jawbone hands-free cellphone. Collimated light from that small red tip would be projected toward the user’s eye.

One would think that this couldn’t work, since the rays of light are entering the user’s pupil from the wrong angle. But this is where a little nano-fabrication comes in handy.

Consider the humble contact lens:


Normally a contact lens, which rests upon its user’s cornea, uses refractive optics to make slight corrections to incoming light rays. But independently of this, we could also place diffractive patterns inside a contact lens, at a scale smaller than the wavelength of light. Effectively, we would be embedding a custom holographic optical element inside the contact lens.

Below is an image of a blazed nano-scale relief pattern that is currently used as a kind of diffractive mirror. When coherent laser light of the proper frequency encounters this element, the beam of light becomes coherently diffracted, and heads out again into a very different (and very specific) direction:


Similar sub-wavelength patterns embedded in a contact lens could be used to deflect laser light coming in from the side, so that the light ends up heading into the eye and toward the retina. The lens could be weighted on one side to keep it oriented properly, which is standard practice for astigmatism-correcting lenses.

Such a custom diffractive pattern would have essentially no effect on non-coherent light that heads straight into the eye, so the contact lens would not interfere at all with normal vision.

This is, in effect, a scaled down analog of the technology currently used for transparent rear-projection screens such as the DaLite Holo Screen. So unlike an electronic contact lens, this is technology that could be built today, given a standard nano-fabrication facility and a little engineering.

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