VISION BY MEMS TECHNOLOGY IMAGE PROCESSING TECHNIQUE

PREPARED BY,BALAMURUGAN.R.KBALASUBRAMANI.K

FINAL YEAR, ECE

PSNA COLLEGE OF ENGINEERING AND TECHNOLOGY

CONTACT:balamuruganpsna@gmail.com

9791542371

ABSTRACT

The human eye is a

remarkable imaging device, with

many attractive design features.

The human eye is somewhat like

a filter with a response similar to

that of a tuned circuit. It has

been shown that electrical

stimulation of retinal ganglion

cells yields visual sensations.

Therefore, a retinal implant for

blind humans suffering from

retinitis pigmentosa based on

this concept seems to be

feasible. Until now, those who

lost their vision to retinal disease

would have had little hope of

regaining it. But technological

breakthroughs could soon give

back the gift of sight. Several

groups of scientists have already

developed silicon microchips

that can create artificial vision.

Diseases like macular

degeneration and retinitis

pigmentosa destroy the retina

and lead to blindness. This

implant would replace damaged

rods and cones, acting as a light

receptor and optical signal

converter.

MEMS:Microelectromechanical

systems is the integration of

mechanical elements, sensors,

actuators, and electronics using

batch-level microfabrication

technology.With advancements

in electronics, and biomedical

engineering technology, it may

someday be possible to have an

artificial eye that can provide

sight as well. Work is already in

progress to achieve this goal,

based on advanced

microelectronics and

sophisticated image recognition

techniques.

"The aim is to bring a

blind person to the point where

he or she can read, move

around objects in the house, and

do basic household chores,"

says Sandia project leader Kurt

Wessendorf. "They won't be able

to drive cars, at least in the near

AIRBORNE INTERNET 2

future, because instead of

millions of pixels, they'll see

approximately a thousand. The

images will come a little slowly

and appear yellow. But people

who are blind will see."

This paper concentrates on the MEMS part of this implant.

INTRODUCTION

This paper describes about the

extraocular part of the system

that records visual images. The

images are transformed by a

neural net into corresponding

signals for stimulation of the

retinal ganglion cells. These

signals are transmitted to a

receiver unit of an intraocular

implant, the retina stimulator.

Integrated circuitry of this unit

decodes the signals and

transfers the data to a

stimulation circuitry that selects

stimulation electrodes placed

onto the retina and generates

current pulses to the electrodes.

By this, action potentials in

retinal ganglion cells are evoked,

causing a visual sensation.

It is proved that the

nerves behind the retina still

functioned even when the retina

had degenerated. Dr. Mark

Humayun demonstrated that a

blind person could be made to

see light by stimulating the nerve

ganglia behind the retina with an

electrical current. Based on this

information, scientists created a

device that could translate

images and electrical pulses that

could restore vision.

MEMS promises to

revolutionize nearly every

product category by bringing

together silicon-based

microelectronics with

micromachining technology,

making possible the realization

of complete systems-on-a-chip.

MEMS is an enabling technology

allowing the development of

smart products, augmenting the

computational ability of

microelectronics with the

perception and control

capabilities of microsensors and

microactuators and expanding

the space of possible designs

and applications.

PERCEPTION OF

AN EYE

Vision is a biological

phenomenon in which

electromagnetic radiation

interacts with specialized cells

that when stimulated cause a

chemical change. This chemical

change starts a cascade of

neurological events resulting in

perception of the organism's

external environment. Human

retina, the part of the eye that

interacts with electromagnetic

radiation and sends information

to the brain for further

processing.

The retina is the region of the

eye that allows that receives and

is changed by electromagnetic

radiation. Only electromagnetic

radiation of wavelengths that can

change retinal cells can be

perceived by humans as light.

These wavelengths are called

the visible spectrum. The range

of the visible spectrum is usually

between 400 and 700 nm.

Electromagnetic radiation that

has a wavelength outside of this

window is does not affect retinal

cells and therefore cannot be

perceived.

ARTIFICIAL EYE

The United States Department of

Energy has sponsored research

into one model of an artificial

retina. In this model, a camera is

placed in a pair of eyeglasses.

The camera receives visual

information and transmits the

infromation to a microprocessor

in the earpiece of the glasses.

The microprocessor converts the

signal from the camera to a

digital signal is transmitted to a

device implanted on the retina.

This retinal implant sends

electrical signal directly to the

ganglion cells of the retina.This

information is then sent back

through the optic nerve to the

brain.When light strikes retinal

cells, it changes the chemical

composition of cells in the retina.

This information is then carried

via the optic nerve to the brain.

Where the information is

processed and interpreted.

This device has been been

tested in six patients. Presently,

this retinal implant has sixteen

electrodes meaning that

individuals with the implant have

16 discreet regions that can

receive light. These individuals

are all now able to discern light

from dark environments and

sense the presence of large

objects.

A tiny camera and RF

transmitter on the patient's

glasses captures images. A

microcomputer worn on the belt

processes the images. From

there, they're transmitted to the

microchip. Next, the chip

transmit the images as electrical

pulses to the retina via an array

of implanted electrodes. That

information is then processed

and sent to the brain, creating

the effect of sight.

There are two approaches to

the stimulation of retinal ganglion

cells. In the subretinal approach

stimulation electrodes are placed

behind the retina at the place of

the degenerated rods and

cones. In the epiretinal approach

the stimulation electrodes are

placed on the retina from inside

the eye.

EPI-RETINAL

IMPLANT SYSTEM

Step1: The system consists of

an extraocular part and an

intraocular part. In the

extraocular part a camera takes

visual images. Using a digital

signal processor, the visual

images are transformed via a

neural net into control data for

the stimulation part of the

system. These data are finally

transmitted into the interior of the

eye via a radio frequency (RF)

link, together with the energy

needed to supply the intraocular

part. On the implant, the data

are decoded in a receiver unit

and transferred via connectors to

the stimulation part of the

system.

Step 2:

View through the polyimide film onto

the receiver chip.

The receiver unit consists of

a small coil, a receiver chip for

power and data recovery and

some surface mount devices.

Metal lines connect the receiving

unit to the stimulation unit. The

stimulator consists of a

stimulator chip and planar

stimulation electrodes made

from platinum. All components

are assembled onto a 10 µm thin

polyimide foil.

The receiver unit is located

in an artificial lens. Because a

wireless connection RF coupling

is implemented using resonator

circuits, the data, which have

been coded to guarantee a safe

transmission, are separated from

the carrier by demodulation and

decoding. The electrical power is

extracted from the RF signal by

rectifying this voltage. The data

are forwarded via an integrated

micro cable in a serial manner to

the stimulator chip.The current

consumption is approximately

170 µA. The coded data rate

amounts to 200 kbit/s. Both

receiver and stimulator chip are

driven with the same 10-V power

supply extracted from the RF

signal. According to the received

data, the stimulator circuitry

selects the stimulation electrode

and delivers bipolar stimulation

pulses to it.

This circuitry can drive up

to 25 electrodes. The pulses are

adjustable to pulse widths from

10–1130 µs and pulse currents

from 0–100 µA. The current

consumption at maximum

stimulation current amounts to

330 µA. A pulse rate of up to 500

Hz is possible.

After assembly of the

different parts, the device is

encapsulated with biocompatible

parylene and silicone to prevent

eye liquids from reaching the

electronic components and to

ensure biocompatibility of the

whole system.

Step 3: Shows a fully

encapsulated system.

Photo of an encapsulated retina

implant system.

The left part of the picture shows

the receiving part encapsulated

into an artificial lens.

The right part of the picture

shows the encapsulated

stimulator chip and the

stimulation electrodes.

Step 4:

Implant system activity

The serial data stream to

the stimulator chip (violet) and

the bipolar stimulation pulses

(red) directly measured by micro

needles from the stimulation

electrodes. Video signals from

an external camera are

transmitted to the implant via a

radio antenna and microchip

beneath the skin just behind the

ear. By shifting the phase and

varying the strength of the

signals, the coil can stimulate

different parts of the optic nerve.

SUBRETINAL

IMPLANT SYSTEM

The "Sub retinal"

approach involves the electrical

stimulation of the inner retina

from the sub retinal space by

implantation of a semiconductor-

based micro photodiode array

(MPA) into this location. The

concept of the sub retinal

approach is that electrical

charge generated by the MPA in

response to a light stimulus may

be used to artificially alter the

membrane potential of neurons

in the remaining retinal layers in

a manner to produce formed

images.

silicon

array

Some subretinal implants use

signals and power from external

circuitry, while others use only

incident light as a power source

and effectively replace damaged

photoreceptors.

MEMS IN

ARTIFICIAL EYEMicromachined lens arrays:

Three types of MEMS

lens arrays

To create the artificial eye,

the team first needed to

construct a hemispherical mold

of the eye's outer layer, a

structure consisting of thousands

of microlenses.

Using existing technology,

they made a flat array of these

tiny, domed lenses arranged in

the hexagonal honeycomb

pattern.

A scanning electron

microscope image of the surface

of an artificial compound eye

shows some of the 8,700

hexagonal microlenses that

make up its surface.

On top of the hexagonal

honeycomb pattern, apply a thin

slab of an elastic polymer called

polydimethylsiloxane, or PDMS,

creating a concave pattern of the

CYLINDRICAL

SQUARE PACKED

HEXAGONAL

lenses in the polymer. By affixing

the PDMS membrane over the

opening of a vacuum chamber

and applying negative air

pressure, they pulled it into the

dome shapes they needed,

controlling its form by using

different pressures.

schematic illustrtion of hemispherical

elastomeric transfer element

RF MEMS

COMPONENTS

Several types of MEMS

components have been

designed to operate in radio-

frequency communications

circuits. Low-power MEMS

filters, variable capacitors, and

switches have all been identified

as promising MEMS

components of RF

communications systems.

MEMS filters use mechanical

vibrations to filter RF signals.

ADVANTAGES

High accuracy

Small size Fast response time High precision Large dynamic range Systems integration Lower costs

The nature of MEMS technology

and its diversity of useful

applications make it potentially a

far more pervasive technology

than even integrated circuit

microchips. Furthermore, MEMS

is not about making things out of

silicon, even though silicon

possesses excellent materials

properties making it an attractive

choice for many applications.

DRAWBACKS

Resolution

Programming

Difficulty in design

CONCLUSION

Eye movement-based

interaction offers the potential of

easy, natural, and fast ways of

interacting in virtual

environments. ”This approach

allows us to put electronicsin

places where we couldn’t before.

Microelectronic integrated

circuits can be thought of as the

"brains" of a system and MEMS

augments this decision-making

capability with "eyes" to allow

microsystems to sense and

control the environment.

Sensors gather information from

the environment through

measuring mechanical, thermal,

biological, chemical, optical, and

magnetic phenomena.

The electronics then

process the information derived

from the sensors and through

some decision making capability

direct the actuators to respond

by moving, positioning,

regulating, pumping, and

filtering, thereby controlling the

environment for some desired

outcome or purpose. Among the

numerous methods for improving

devices, considerable

possibilities are provided by the

application of mems.

REFERENCES

Integrated Circuit

Research Vol-3 published

by University Of Florida

"Joint 'biochip' project

eyes artificial retina,"

Electronic Engineering

Times

Artificial Retina Project:

Restoring Sight Through

Science

Human Physiology: The

Mechanisms of Body

Function.

http://www.mems-

exchange.org

http://www.slackinc.com/

eye/osn/osnhome.htm.

http://

pharmacology.case.edu/

Department/faculty/

palczewski/lab