DIGITAL CONTACT LENSES: THE EYES OF THE FUTURE
Yrret Maldonado Ortiz
Envision the idea of being constantly updated with the latest information. At the present time the possibilities are remarkable. An international team of researchers has developed the first working prototype for such a device. In a study published in the Journal of Micromechanics and Microengineering, the researchers from the University of Washington, Seattle, and Aalto University in Finland describe the construction of a computerized single pixel contact lens and demonstrated its safety by testing it on live eyes that showed no adverse side effects.
The prototype contact lens has the capacity of streaming real-time information across the field of vision; potentially providing the wearer with information updates. This device is an example of the integration of devices into miniaturization unconventional substrates. The lens display consists of an antenna to harvest power sent out by an external source, as well as an integrated circuit to store this energy and transfer it to a transparent sapphire chip containing a single blue LED.
One of the mayor challenges the researchers had to face in the design process of generating the contact lens was due to the required small size of the nature of the contact lens and that due to the fact that the human eye has a minimum focal distance which is at least several centimetre away, therefore objects on a contact lens cannot be resolved, making the information in the lens itself look blurry and out of focus. In order to resolve this problem researcher employed a set of a class of micro-lens known as micro-Fresnel lenses, which focus light by refraction in a set of concentric curved surfaces. Their design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. Compared to conventional bulky lenses, the Fresnel lens is much thinner, larger, flatter and have shorter focal lenghts, allowing it to focus the projected image onto the retina. Therefore the use of this Fresnel lenses in the design of the contact lens is ideal, because it does not only help solve the problem of the image projection on the retina, making the lens more biocompatible but it also fits the required measurements of volume needed in order to use it in the design of the contact lens.
In order for the lens to acquire the necessary energy for the system to operate without a wired connection, researchers had to developed an CMOS integrated circuit because it meet the terms of the limitation of the design of the lens. Since the strict low power consumption and small footprint requirements in the design of the contact lens prohibited the use of commercially available integrated circuits. Therefore the researchers had to design a custom IC to perform control and radio functions. In order to be able to incorporate the wireless electronics onto a contact lens. This chip design by the researcher has the ability as the lead researcher Babak Parviz from the university of Washington establish to perform the following tasks: “the conversion of RF power received by the on-lens antenna to a dc-supply voltage, on-chip energy storage sufficient to excite the micro-LED, and generation of an on-chip clock source to duty cycle an LED driver switch.”
Custom designed and fabricated power harvesting and LED driver circuit. (a) Schematic of the CMOS IC architecture and connectivity. (b) Photograph of assembled chip with rectifier and storage capacitor outlined in white, viewed through the polymer substrate. Scale bar is 250μm.
The power management circuitry consists of a ring oscillator, a pulse generator and a passive level shifter. As established by the researchers, “the ring oscillator is powered from the second stage of an eight-stage cascaded rectifier. Each inverter in the three-stage oscillator uses stacked high-threshold devices for low leakage and low-power operation.” As a result, (as the research should) the power consumption of the ring oscillator is less than 500 nW at 1.0 MHz.
The device could overlay computer-generated visual information making it easy to access information instantly from platforms such as mobile phones. The researchers claim that their device will have a wide range of uses; that goes from leisure in its use for gaming devices and navigation system as it can be employed for educational, health application, such as a biosensor and even as an aid to the hearing impaired. Significant improvements are necessary to produce fully functional, remotely powered, high-resolution displays. However the research, data, results and design that wave been obtained by this group of researcher have establish a create stepping stone in the fundamental change of how people access and interact with visual information and how they see the world.
Reference:
A single-pixel wireless contact lens display
A R Lingley1, M Ali2, Y Liao1, R Mirjalili1, M Klonner2, M Sopanen2, S Suihkonen2, T Shen3, B P Otis1, H Lipsanen2 and B A Parviz1
Journal of Micromechanics and Microengineering, Vol.21, Num.12, 125014, 2011
"Digital Contact Lenses Come into Focus." Physicsworld.com. Web. 30 Nov. 2011. .
Future Contact Lenses Can Put Pixels on Our Eyeballs
By Ross A. Lincoln - 12:00 AM - November 26, 2011
http://www.tomsguide.com/us/1-Pixel-Contact-Lens-HUD-implant,news- 13298.html
"Fresnel Lenses." Michigan. Web. 01 Dec. 2011. .
^ "Fresnel lens." Encyclopædia Britannica. 2005. Encyclopædia Britannica Online. 11 November 2005.
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