Transcript Low Power Artificial Retina

Low Power Artificial Retina
By
Duha Jabakhanji
Content
Introduction:
 Prosthetic Implants
 The Eye
 The retina
 Types of vision implants
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Subretinal Implants:
Why subretinal implants?
How it works
Clinical trials
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Challenges:
The main issues
Temperature Variable Supply Voltage
How it works
 The Project:
 Project Plan
 Time Table
Introduction: Prosthetic Implants
 What to look for in prosthetic implants?
 Stability
 Biocompatibility
 Small and Lightweight
 Non-Intrusive and requiring a simple surgery to implant the
device
 Low Power
Introduction: The eye
Introduction: The retina
Light
Introduction: Types of vision implants
Depending on the
type of vision
impairment, there
are different types of
implants.
Retinal Prosthesis
Epiretinal prosthesis
Subretinal Prosthesis
Optic Nerve Prosthesis
Subretinal Implants: Why Subretinal
Implants?
Advantages:
 More stable due to their location in the retina. Easier
to attach.
 No need for extra equipment, it is a stand-alone unit.
 Uses solar power instead of a battery. No need to
send the chip power.
 Easy surgery to implant the chip. Patients recover
within a day.
Subretinal Implants: Why Subretinal
Implants?
Disadvantages:
 Applies only to two kinds of blindness: retinitis pigmentosa and
age-related macular degeneration.
 Remote area in the subretinal space.
Subretinal Implants: How it works
Retinitis pigmentosa and
age-related macular
degeneration degrades
the rods and cones, but
spares the remainder of
the retina.
Subretinal Implants: How it works
 If the bipolar cells and horizontal cells are replaced, then edge
detection circuitry is needed.
 Other wise, only a circuit that converts the current from the
photo diode into pulses is needed.
 The frequency of the pulses depends on the intensity of the
light.
 There are many different circuits to implement the chip.
Subretinal Implants: How it works
M. Mazza, P. Renaud, D. C. Bertrand, and A. M. Ionescu, “CMOS Pixels for Subretinal
Implantable Prothesis”
Subretinal Implants: How it works
M. Mazza, P. Renaud, D. C. Bertrand, and A. M. Ionescu, “CMOS Pixels for Subretinal
Implantable Prothesis”
Subretinal Implants: Clinical Trials
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Subretinal implants have been tested on animals.
Recently they have been implanted in humans.
Degradation in the retina has been observed in patients.
Reasons are not fully understood.
Possible reason is the blocking nutrients from reaching the
retina.
 Laser holes have to be drilled to allow the flow of nutrients.
 No patients have shown any rejection, infection, erosion,
inflammation or retinal detachment.
 Its long-term effects have yet to be tested.
 In some cases the artificial retina has failed, cause unknown.
Challenges: The main issues
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Size is critical, the smaller the circuit the better.
200-pixel matrix is needed for basic orientation.
650-pixel matrix is needed for ordinary script reading.
Low power consumption is a must.
Due to its remote location on the eye, methods of delivering
power are difficult.
 Solar arrays power is limited.
 Location of the subretinal implant makes heat dissipation
difficult.
 It also comes in contact with retinal cells, making heat damage
an issue.
Challenges: Temperature Variable Supply
voltage (TVS)
 A temperature variable supply voltage is suggested to lower
power.
 The circuit will detect the temperature of the chip and lower its
voltage supply accordingly.
 This will lower power consumption and heat dissipation.
 It will consequently lower the temperature of the chip.
 P=Pdy+Pst+Psc
 Pdy=CVdd2f
 Pst=VddIsub
 Isub=I0Exp{Vthq/kT-1}
 Cox is oxide capacitance and CD0 is depletion capacitance.
 0 is the low field mobility, K the Boltzman constant, and Weff and Leff
are the effective width and length respectively.
Challenges: How Temperature Variable
Supply voltage (TVS) works
G. Ono, M. Miyazaki, H. Tanaka, N. Ohkubo, and T. Kawahara, “Temperature referenced
supply voltage and forward-body-bias control (TSFC) architecture for minimum power
consumption [ubiquitous computing processors]”
Challenges: How Temperature Variable
Supply voltage (TVS) works
Solar
Panel
Control
Circuit
A/D
converter
Temperature
Sensor
VDD
Project Plan
 O.13 Technology will be
used.
 Pixel array will be designed.
 Solar array will not be
implemented.
 TVS circuit will be designed.
 Both circuits will be
combined.
 An environment similar to
the subretinal space is to be
simulated.
Solar Panel
S
ol
ar
P
a
n
el
T
VS
Pixel Array
Solar Panel
S
ol
ar
P
a
n
el
Time table
Feb-16
Design of the chip (putting the
circuits together)
Implementation and testing
(using Cadence)
Second Presentation
Final report
Mar-12
Mar-28
Mar-31
April-20 (two weeks after the final)
References
[1] M. Mazza, P. Renaud, D. C. Bertrand, and A. M. Ionescu, “CMOS Pixels for
Subretinal Implantable Prothesis”, IEEE Sensors Journal, Vol. 5, No. 1, February
2005.
[2] C. Y. Wu, F. Cheng, C. T. Chiang, and P. K. Lin, “ A Low-Power implantable
pseudo-BJT-based silicon retina with solar cells for artificial retinal prosthesis”,
Circuits and Systems, 2004. ISCAS '04. Proceedings of the 2004 International
Symposium on, Volume: 4 , 23-26 May 2004
[3] K. Shakeri, and J. D. Meindl, “Temperature Variable Supply Voltage for Power
Reduction”, VLSI, 2002. Proceedings. IEEE Computer Society Annual
Symposium on, 25-26 April 2002, Pages: 64 – 67
[4] G. Ono, M. Miyazaki, H. Tanaka, N. Ohkubo, and T. Kawahara, “Temperature
referenced supply voltage and forward-body-bias control (TSFC)
architecture for minimum power consumption [ubiquitous computing
processors]” Solid-State Circuits Conference, 2004. ESSCIRC 2004.
Proceeding of the 30th European, 21-23 Sept. 2004, Pages:391 – 394
[5] E. Marggalit et al. “Retinal Prosthesis for the Blind”, Opthamology.
Survey of, Vol. 47, No. 4, July-August 2002
[6] E. Funatsu, Y. Nitta, Y. Miyake, T. Toyoda, J. Ohta, and K. Kyuma, “ An
Artificial Retina Chip with Current-Mode Focal Place Image Processing
Functions” Electron Devices, IEE Transaction on, Vol. 44, No. 10,
October 1997
[7] F. Paillet, D. Mercier, T. M. Bernard, and E. Senn, “ Low Power Issues
in a Digital Programmable Artificial Retina” Low-Power Design, 1999.
Proceedings. IEEE Alessandro Volta Memorial Workshop on, 4-5
March 1999 Pages: 153 - 161
[8] M. S. Humayum et al. “Pattern electrical stimulation of the human
retina”, Vision research 39,1999 pages: 2569-2576
[9] C. Y. Wu, L. J. Lin, K. H. Huang, “ A new light-activated CMOS retinalpulse generation circuit without external power supple for artificial
retinal prosthesis” Electronics, Circuits and Systems, 2001. ICECS
2001. The 8th IEEE International Conference on, Volume: 2 , 2-5 Sept.
2001 Pages:619 - 622 vol.2