TECHNOLOGY

Stay healthy witha smart contact lensLenses that monitor pressure in the eye or glucose in tearsare on the way. Welcome to the world of augmented vision

Duncan Graham-Rowe

THE next time you gaze deep intosomeone's eyes, you might beshocked at what you see: tinycircuits ringing their irises. theirpupils dancing with pinpricks oflight. These smart contact lensesaren't intended to improve vision.Instead, they will monitor bloodsugar levels in people with diabetesor look for signs of glaucoma.The lenses could also map

images directly onto the field ofview, creating head-up displays forthe ultimate augmented realityexperience, without wearingglasses or a headset. To producesuch lenses, researchers aremerging transparent, eye-friendlymaterials with microelectronics.In 2008, as a proof of concept,

Babak Parviz at the University ofWashington in Seattle created aprototype contact lens containinga single red LED.Using the sametechnology, he has now created alens capable of monitoring glucoselevels in people with diabetes.Itworks because glucose levels

in tear fluid correspond directly tothose found in the blood, makingcontinuous measurementpossible without the need forthumb pricks, he says. Parviz'sdesign calls for the contact lens tosend this information wirelesslyto a portable device worn bydiabetics, allowing them tomanage their diet and medicationmore accurately.Lenses that also contain arrays

oftiny LEOsmay allow this orother types of digital informationto be displayed directly to thewearer through the lens. This

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kind of augmented reality hasalready taken offin cellphones,with countless software appssuperimposing digital dataonto images of our surroundings,effectively blending the physicaland online worlds.Making it work on a contact lens

won't be easy, but the technologyhas begun to take shape. LastSeptember, Sensimed, a Swissspin-off from the Swiss FederalInstitute of Technology inLausanne, launched the very firstcommercial smart contact lens,designed to improve treatmentfor people with glaucoma.

The disease puts pressure onthe optic nerve through fluidbuild-up, and can irreversiblydamage vision if not properlytreated. Highly sensitive platinumstrain gauges embedded inSensimed's Triggerfish lens recordchanges in the curvature of thecornea, which correspond directly.to the pressure inside the eye, saysCEOJean-Marc Wismer. The lenstransmits this information

"The idea is to map imagesonto the field of view,creating head-up displaysfor augmented reality"

wirelessly at regular intervals to aportable recording device worn bythe patient, he says.Like an RFIDtag or London's

Oyster travel cards, the lens getsits power from a nearby loopantenna - in this case taped to thepatient's face. The poweredantenna transmits electricity tothe contact lens, which is used tointerrogate the sensors, processthe signals and transmit thereadings back.Each disposable contact lens is

designed to be worn just once for24 hours, and the patient repeatsthe process once or twice a year.This allows researchers to look forpeaks in eye pressure which varyfrom patient to patient during thecourse of a day. This informationis then used to schedule thetimings ofmedication."The timing of these drugs

is important," Wisner says.Parviz, however, has taken a

different approach. His glucosesensor uses sets of electrodes torun tiny currents through the tearfluid and measures them to

Eye strain? Triggerfish will knoW

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detect very small quantities ofdissolved sugar. These electrodes,along with a computer chipthat contains a radio frequencyantenna, are fabricated on a flatsubstrate made of polyethyleneterephthalate (PET),a transparentpolymer commonly foundin plastic bottles. This is thenmoulded into the shape of acontact lens to fit the eye.Parviz plans to use a higher-

powered antenna to get a betterrange, allowing patients to carrya single external device in theirbreast pocket or on their belt.Preliminary tests show thathis sensors can accurately detecteven very low glucose levels.Parvis is due to present hisresults later this month at theIEEEMEMS 2011 conference inCancun, Mexico."There's still a lot more testing

we have to do," says Parviz. Inthe meantime, his lab has madeprogress with contact lensdisplays. They have developedboth red and blue miniatureLEOs-leaving only green forfull colour - and have separatelybuilt lenses with 3D optics thatresemble the head-up visorsused to view movies in 3D.Parviz has yet to combine both

the optics and the LEOsin thesame contact lens, but he isconfident that even images soclose to the eye can be broughtinto focus. "You won't necessarilyhave to shift your focus to see theimage generated by the contactlens," says Parviz.1t will justappear in front of you, he says.The LEDswill be arranged in a gridpattern, and should not interferewith normal vision when thedisplay is off.For Sensimed, the circuitry is

entirely around the edge of thelens (see photo). However, bothhave yet to address the fact thatwearing these lenses might makeyou look like the robots in theTerminator movies. False irisescould eventually solve thisproblem, says Parviz. "But that'snot something at the top of ourpriority list," he says .•

INSIGHT

Glasses-free 3D TV triesto broaden out its appealTELEVISION makers have shifted theirsights from HD to 3D. In 2010, the first3D TVs from major manufacturerswent on sale, and a spate of 3Dchannels launched around the world.However, many viewers dislike the

special glasses that existing 3D TVsrequire. Over half of the people askedto watch 30 minutes of 3DTVfoundthe glasses "a hassle", accordingto a recent report by the Cable andTelecommunications Associationfor Marketing, a non-profit cableTV industry body in National Harbor,Maryland. So the emphasis in 2011is likely to be on "autostereoscopic"displays, These aim separate imagesat the viewer's right and left eye, withno need for special glasses,Unlike the 3D TVs already on the

market many of the first glasses-freedevices deliver 3D images to just oneviewer at a time, That's the case withthe Nintendo 305, a hand-heldgaming unit due for release in Japanin February. It works by interlacingvertical strips of the images fortheleft and right eye, To do this it hasan array of slits - known as a parallaxbarrier - in front of the screen to

ensure that each eye sees only thestrips it is meant to, as long as the userstays within a narrow viewing area,That's not a drawback for a hand-helddevice, but it might be for the firstglasses-free 3D TVs, which Toshibareleased in Japan in December. Theyare available with 3D-centimetre(12-inch) and 51-centimetre screens,but neither model produces a 3Deffect outside a small viewing area.iPont International, based in

Budapest Hungary, has a different

"It has to be easy forviewers to find and keep tothe sweet spots where the3D effect springs into life"

solution, At the Consumer ElectronicsShow in Las Vegas, Nevada, this week,it demonstrated a 140-centimetreglasses-free 3D display developedby Tridelity in Jersey City, New Jersey,Tridelity's screens have multipleparallax barriers and so can sendlight from pairs of images in fivedirections at once, considerablywidening the viewing area so thatat least five people can enjoy the

Looks great, but just one gamerat a time can see the 3D effect

3D experience simultaneously.iPont has already begun

deploying the screens in cinemalobbies, says Glen Harper, thecompany's business developmentdirector, "Far back from the screen,it looks like 20," he says, "but whenpeople get close enough to see thepop-out effect they say it's cool.'Tridelity's technology has its

own drawbacks, however, Parallaxbarriers reduce the brightness ofthe display since they block someof the light says Doug Lanman ofthe Massachusetts Institute ofTechnology Media Lab, Dividing thelight five ways, as Tridelity's screensdo, will only compound that issue,so that viewers will need to be in darksurroundings to see the 3D effectLanman and his team are

attempting to minimise this problemwith a parallax barrier that adaptsto each video frame to block onlythe minimum amount of light toachieve a 3D effect For instance,if the edge of an object is lyinghorizontally, the left and right-eyeimages are essentially identical, sothe barrier in this part of the imagecan be temporarily switched off. Thesame applies to any featureless areasof the image, With this approach,Lanman says they can build a displaythree to five times as bright as otherparallax barrier displays,Even so, there are still questions

to be answered before glasses-free3D displays for multiple viewers areready for market. Perhaps the mostimportant challenge is to make iteasy for viewers to find and keep tothe sweet spots where the 3D effectsprings into life, In the interveningzones, images get sent to thewrong eyes, making the picturelook garbled, warns 3D consultantJohn Merritt of Williamsburg,Massachusetts, Despite the buzzaround autostereoscopic displays,he sounds a pessimistic note, "Rightnow, I know of no good substitutefor glasses." Jeff Hecht.

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