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TRANSISTOR THIN FILM TECHNOLOGY

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irum sabah

on 4 December 2013

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Transcript of TRANSISTOR THIN FILM TECHNOLOGY

Artificial Retinas are referred to as visual prosthesis, it is also known as a bionic eye
It is an experimental visual device intended to restore functional vision in those suffering from partial or total blindness
In this presentation we will be discussing about the Artificial Retina made using. Thin-Film Transistors, which can be fabricated on transparent and exible substrates. Electronic photo devices and circuits are integrated on the artificial retina, which is implanted on the inside surface of the living retina at the back part of the human eyeballs.
NEED FOR ARTIFICIAL RETINAS???
IT HELPS PEOPLE SUFFERING FROM THE FOLLOWING EYE DISEASES:-
Retinitis Pigmentosa-
Hereditary genetic disease.
Degeneration of the retina
Gradually progress towards center of eye.
Spares the foveal region.
Tunnel vision results
Macular Degeneration-
Genetically related.
Cones in macula region degenerate.
Loss or damage of central vision.
Common among aged people.
Peripheral retina spared.
RETINAL IMPLANTATION:-
A retinal implant is a biomedical implant technology currently being developed by a number of private companies and research institutions worldwide.The first application of an implantable stimulator for vision restoration was developed by Drs. Brindley and Lewin in 1968. The implant is meant to partially restore useful vision to people who have lost their vision. There are two types of retinal implants namely epiretinal implant and subretinal implant.


WORKING OPERATION:-
Artificial Retina using Thin-Film Transistors (TFTs) is fabricated on transparent and exible substrates
Electronic photo devices and circuits are integrated on the artificial retina, which is implanted on the inside surface of the living retina at the back part of the human eyeballs. Since the irradiated light comes from one side of the artificial retina and the stimulus signal goes out of the other side, the transparent substrate is preferable
ARTIFICIAL RETINA USING TRANSISTOR THIN FILM TECHNOLOGY
DRIVEN BY WIRELESS POWER SUPPLY

WHAT IS ARTIFICIAL RETINA TECHNOLOGY???
The concept model of the artificial retina fabricated on a transparent and exible substrate and implanted using epiretinal implant is shown in figure
The retina array includes matrix-like multiple retina pixels.The design of the retina pixel is based on an elementary current mirror, but some improvements are added by considering the characteristics of the TFPDs and poly-Si TFTs and operation of an artificial retina.When a pixel is highly illuminated, its Vout is high
The retina pixel consists of a photo transistor, current mirror, and load resistance. The photo transistor is optimized to achieve high efficiency, and the current mirror and load resistance are designed by considering the transistor characteristic of TFTs
WIRELESS POWER SUPPLY USING INDUCTIVE COUPLING
The wireless power supply using inductive coupling is shown in figure
This system includes a power transmitter, powe
r receiver, diode bridge, and Zener diodes. The power transmitter consists of an ac voltage source and induction coil. The Vpp of the ac voltage source is 10 V, and the frequency is 34 kHz, which is a resonance frequency of this system. The material of the in- duction coil is an enameled copper wire, the diameter is 1.8 cm, and the winding number is 370 times. The power receiver also consists of an induction coil, which is the same as the power transmitter and located face to face. The diode bridge rectifies the ac voltage to the dc voltage, and the Zener diodes regulate the voltage value.
system should be downsized and bio-compatibility has to be in- spected, the supply system is in principle very simple to implant it into human eyeballs. the generated power is not so stable
which may be because the artificial retina is fabricated on a insulator substrates, has little parasitic capacitance, and is subject to the influence of noise. Therefore, it is necessary to confirm whether the artificial retina can be cor- rectly operated even using the unstable power source.
DETECTED RESULT OF ILLUMINATION PROFILE
The artificial retina with the wireless power supply system is located in a light-shield chamber, and Vout in each retina pixel is probed by a manual prober and voltage meter. White light from a metal halide lamp is diaphragmmed by a pinhole slit, fo- cused through a convex lens, reflected by a triangular prism and irradiated through the glass substrate to the back surfaces of the artificial retina on a rubber spacer. The real image of the pinhole slit is reproduced on the back surface.

MERITS
An artificial retina can offer hope to those with retinitis pigmentosa, as it may help them achieve a level of visual perception
The artificial retina provides an interface between biotic and abiotic systems
This design for the artificial retina facilitates both surgical procedures and regulatory compliance.

DEMERITS
There are several patents for artificial retinas.But all of them have limitations
Some require the patient to have sight. Some restore only limited acuity, or the ability to detect motion or to distinguish between light and dark. Some are bulky and/or require prosthesis.
OVERALL SUMMARY
Artificial Retina, a retinal prosthesis that can be used to treat age-related macular degeneration and inherited retinal disorders such as retinitis pigmentosa. The device uses application-specific integrated circuits to transform digital images from a camera into electrical signals in the eye that the brain uses to create a visual image. The system features a video camera and transmitter mounted in sunglasses, a visual processing unit, and a battery pack to power the device that is worn on the belt. The retinal implant receives a signal via wireless transmission, encodes it into specific patterns of stimulation pulses that are conducted through a cable to the electrode array that stimulates the retina. The brain perceives the patterns of light spots corresponding to the stimulated electrodes. In clinical trials, patients with vision loss were able to identify objects, increase mobility and detect movement
SOME OF ITS DEVELOPERS ARE :-
Lawrence Livermore National Laboratory, Livermore, Calif.
Argonne National Laboratory, Lemont, Ill,
Los Alamos National Laboratory, Los Alamos, N.M.
Oak Ridge National Laboratory, Oak Ridge, Tenn.

SOME OF ITS ORGINAZTIONS ARE :-
Argonne National Laboratory (U.S. Dept. of Energy)
California Institute of Technology
Doheny Eye Institute
Lawrence Livermore National Laboratory (U.S. Dept. of Energy)

CURRENT STATUS AND FUTURE DEVELOPMENTS
Clinical reports to date have demonstrated mixed success, with all patients report at least some sensation of light from the electrodes, and a smaller proportion gaining more detailed visual function, such as identifying patterns of light and dark areas.
However, clinical testing in implanted subjects is somewhat limited and the majority of spatial resolution simulation experiments have been conducted in normal controls. It remains unclear whether the low level vision provided by current retinal implants is sufficient to balance the risks associated with the surgical procedure, especially for subjects with intact peripheral vision
THE END
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