So, my earlier idea for "pinhole contacts" ran into problems, possibly due to diffraction. The aim was to produce a contact lens which could give an infinite depth of field, for people like me who are both short-sighted and presbyopic.

This is plan B.

Imagine a contact lens made of very soft silicone or a similar material. If we had some sort of annulus around the outer edge of the contact which could enlarge and contract, it would distort the contact in much the same way that the eye's own lens distorts when we shift focus, becoming flatter for far-vision and more convex for near- vision.

So, how to do this? Maybe like this:

Around the edge of the lens (ie, set into the body of the lens, but close to the edge), we put a large number of very fine wire gizmos. Each one consists of a coil of wire (say, 10 turns), with the ends connected together (so, it's a bit like a D, except that the vertical part of the D is coil). We also put a tiny soft-iron rod down the middle of the coil.

These little things are arranged in a circle around the edge of the lens, with the straight part of the D innermost. What I mean is - the straight parts of the D's form a sort of dotted line around the contact lens, with the loops of the D's radiating out like flower petals. I hope that's clearish.

Now, suppose we generate a fairly high-frequency field in the general vicinity of the lens. This should induce a current in each of the little D's, flowing through the coil (the upright of the D) and then around the loop and back again.

This in turn should create a magnetic field (aided and abetted by the little soft-iron core). This in turn should mean that each "D" is attracted to those adjacent to it (ie, we have created a little ring of magnets around the edge of the lens, all north-to-south), which should constrict the lens and cause it to become more convex.

Thus, by controlling the field strength, we can shift focus from far to near.

I have no idea how much force one could generate with a reasonably-sized transmitter and these tiny coils. If it's doable, then the transmitter might need to be worn close to the contacts (which is a nuisance), perhaps behind the ear.

Focus adjustment could be done manually (as it is on some truly variable-focus glasses), via a slider on the transmitter. Ultimately, it would be nice to have autofocus, but this would be very much harder to implement. Some of the new glasses (like "emPower" by Pixelvision) have a tilt-sensor which automatically activates the near-focus mode when the head tilts down, although this isn't ideal.

Does anyone know much about electrorefractive materials? These are what seem to be used in the emPower glasses, but I can't find out much about them. They may offer a better solution for contact lenses.
-- MaxwellBuchanan, Jul 12 2011

Varioptic http://www.variopti...tilt-control-1.html
Maybe the glasses work like this? [NoOneYouKnow, Sep 02 2011]

Eye caramba...

Been wearing glasses all my life, so I'm all for innovative tech in this field (+)
-- normzone, Jul 12 2011


Anyone know enough to comment on the force that could be induced by coils in a contact lens?
-- MaxwellBuchanan, Jul 12 2011


The problem with (relatively) inexpensive adaptive optics is that they are extremely prone to distortion, usually fish eye, although other variations are possible I believe. This isn't to bad if you can train a computer to cancel this out for a given lens setting, but would probably be a bit of a headache for the human brain.
-- MechE, Sep 01 2011



random, halfbakery