Make the frames of glasses out of a heating element. Apply a small amount of voltage from one AAA battery worn around the neck (and feeding power through a small wire), to heat the frames and prevent the glasses from fogging every time you walk into a warm building.-- DIYMatt, Jan 31 2011 Heated Goggles https://airandspace...y-heated-gogglesjpg [bs0u0155, Nov 04 2020] Also useful for Transitions type lenses which take considerably longer to return to clear in cold weather.-- MechE, Jan 31 2011 I don't think heat would propagate very quicky from the frames across the lenses.
However, heated car windscreens have very fine heating elements embedded in them, which are almost invisible (and would be especially so when that close to the eye). Alternatively, transparent oxide coatings can act as conductive heating elements.
Batteries wouldn't last long, though.-- MaxwellBuchanan, Jan 31 2011 Photovoltaic power ? After all, if it's dark, you don't need glasses ...-- 8th of 7, Jan 31 2011 But how could you possibly use sunlight to warm something up???-- MaxwellBuchanan, Jan 31 2011 A hand crank in your pocket?-- pocmloc, Jan 31 2011 No, onlookers might misunderstand ....-- 8th of 7, Jan 31 2011 Peltier plate TEG worn around the neck then?-- DIYMatt, Jan 31 2011 Tear-ducts are not needed 24/7. Simply learn to blow air through them (some people can already do this), and you will be able to warm your lenses without additional apparatus.-- MaxwellBuchanan, Jan 31 2011 Humans have a dedicated high-capacity blood supply to the ears, because proto-humans used them to cool the brain (if any).
Since the sidepieces of the spectacles rest on the ears, it would seem obvious to make them into heat-pipes, and install a small dispenser for a suitable heat-rub cream to stimulate blood flow.-- 8th of 7, Jan 31 2011 Bah. Once again, a good idea to stop spectacles fogging when wearing a facemask turns out to already exist on the hb ...-- 8th of 7, Nov 04 2020 //spectacles fogging when wearing a facemask// I have a wire running along the top edge of my facemask which can be moulded to closely follow the contours of my nose - doing this stops my glasses fogging up.-- hippo, Nov 04 2020 It is not a problem affecting us, but others seem to suffer from it, and it occurred to us that there is money to be made from a suitable innovation, along with the special-to-type disposable batteries...-- 8th of 7, Nov 04 2020 hmm, heated optics are very old. The window on a ~1960's vintage cold room in my building has a heated window. Pilots <link> were using them in the black and white days and I know a Canadian that says that heated snowmobile goggles were a thing in the 1970s*
*Canada is expected to enter the 1980's within the next century.-- bs0u0155, Nov 04 2020 random, halfbakery