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
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
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
fine wire gizmos. Each one consists of a coil of wire
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).
also put a tiny soft-iron rod down the middle of the coil.
These little things are arranged in a circle around the
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
dotted line around the contact lens, with the loops of the
D's radiating out like flower petals. I hope that's
Now, suppose we generate a fairly high-frequency field
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
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
we have created a little ring of magnets around the edge
of the lens, all north-to-south), which should constrict
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
to the contacts (which is a nuisance), perhaps behind the
Focus adjustment could be done manually (as it is on
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
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.