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VISION BY MEMS TECHNOLOGY IMAGE PROCESSING TECHNIQUE
PREPARED BY,BALAMURUGAN.R.KBALASUBRAMANI.K
FINAL YEAR, ECE
PSNA COLLEGE OF ENGINEERING AND TECHNOLOGY
CONTACT:[email protected]
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