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Medicine Technology

Goodbye Bifocals — Electronic Glasses Change Focus 166

kkleiner writes "Move over Ben Franklin, we finally have a replacement for bifocals. Virginia-based Pixel Optics has developed a composite lens that can change the range of focus electronically. The emPower! glasses were created in cooperation with Panasonic Healthcare, and allow you to switch between long distance and short distance vision in a split second. Rather than having a lens divided into two sections, emPower! uses an LCD overlay that can change the focal length of the glasses via electric current. When the LCD layer is off, your lenses are good for intermediate/long distances. Turn the LCD layer on, and a section of the lens is suddenly magnifying close-up images – perfect for reading."
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Goodbye Bifocals — Electronic Glasses Change Focus

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  • by Anonymous Coward on Wednesday January 12, 2011 @02:00PM (#34850874)

    RTFA - you either touch the frame or "engage an accelerometer" (probably not the right device) to switch when you tip your head down.

    Also, the entire lens doesn't change focal length, only sections at the bottom of the lens.

    Basically, you have bifocals that can be switched to full-frame far vision.

  • by mcgrew ( 92797 ) * on Wednesday January 12, 2011 @02:56PM (#34851776) Homepage Journal

    Not as nifty as my CrystaLens. Its focus accomodates, exactly like the eye of a young person does (at least from the user's perspective, even if the mechanism is different).

    Over the life of your eyeballs a CrystaLens is probably cheaper, too. The surgery is ~$7k per eye, but you only need it once and your eyes focus for the rest of your life, no glasses needed (at least, if your surgeon is competent). If you have cataracts, insurance will pay all but about $1k per eye. You can get cataracts from steroid eyedrops.

    The downsides are that the CrystaLens is a surgical implant; they stick a neeedle in your eye, shoot ultrasound down the needle to turn your eye's lens to mush, suck the mush out through the needle, and insert the implant in its place. Most patients don't require any external lenses like glasses or contacts after the surgery, but some do (Evil-X is wearing bifocals, but I think that was a bad choice of surgeons), but most don't have the better than 20/20 vision I got, although something like 98% have better than 20/25. Glasses give better vision for most patients.

    (Journal of the procedure here) [slashdot.org]

  • by goodmanj ( 234846 ) on Thursday January 13, 2011 @01:31AM (#34858148)

    Thanks to people who linked to the patent, I think I understand what's going on now. My guess was mostly right...

    A liquid crystal material consists of long rod-shaped molecules. They have the funny property that light passes through them at a different speed depending on whether the light is polarized parallel to or perpendicular to the axis of the rods. This is called "birefringence".

    Normally, if a thin layer of liquid crystal is sandwiched between two glass plates, the molecules line up parallel to the plates. However, if you put a voltage across the plates, the molecules line up end-to-end, perpendicular to the plates.

    Therefore, applying a voltage effectively changes the speed of light passing through the liquid crystal. Glass optics work because the speed of light in glass is slower than in air: the difference in speed causes the light to be bent. Since liquid crystals can *change* their speed of light electrically, if you create a LC layer with exactly the right shape you can make a "lens" that vanishes when you switch off the voltage.

    There's a lot of technical details (rather than creating a classical lens, the liquid crystals impersonate a Fresnel lens, requiring specific shapes and voltages for the electrodes) but that's the gist of it.

    Where I was being led astray was by the effect liquid crystals have on *rotating the polarization* of light. This is a crucial part of understanding how LCD monitors work [www.kth.se], but after thinking about it I realize that when used in these glasses, the liquid crystal will indeed rotate the polarization, but that's not something the human eye can detect.

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