U.S. patent application number 11/303838 was filed with the patent office on 2006-05-18 for artificial vision system.
This patent application is currently assigned to POLYVALOR s.e.c.. Invention is credited to Jonathan Coulombe, Colince Donfack, Jean-Francois Harvey, Martin Roy, Yvon Savaria, Mohamad Sawan.
Application Number | 20060106432 11/303838 |
Document ID | / |
Family ID | 4143111 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060106432 |
Kind Code |
A1 |
Sawan; Mohamad ; et
al. |
May 18, 2006 |
Artificial vision system
Abstract
A miniaturized body electronic implant for providing artificial
vision to a blind person or for other uses as neuromuscular sensors
and microstimulators. The implant has a high resolution electrode
array connected to a chip integrating implant stimulation and
monitoring circuits, mounted on the back of the electrode array.
The implant is powered by and communicates with an external unit
through an inductive bi-directional link.
Inventors: |
Sawan; Mohamad; (Laval,
CA) ; Harvey; Jean-Francois; (Blainville, CA)
; Roy; Martin; (Montreal, CA) ; Coulombe;
Jonathan; (Montreal, CA) ; Savaria; Yvon;
(Montreal, CA) ; Donfack; Colince; (Nepean,
CA) |
Correspondence
Address: |
FOGG AND ASSOCIATES, LLC
P.O. BOX 581339
MINNEAPOLIS
MN
55458-1339
US
|
Assignee: |
POLYVALOR s.e.c.
Montreal
CA
|
Family ID: |
4143111 |
Appl. No.: |
11/303838 |
Filed: |
December 16, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10416403 |
May 12, 2003 |
|
|
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11303838 |
Dec 16, 2005 |
|
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Current U.S.
Class: |
607/54 |
Current CPC
Class: |
A61N 1/0551 20130101;
A61N 1/0543 20130101; A61N 1/36046 20130101 |
Class at
Publication: |
607/054 |
International
Class: |
A61N 1/18 20060101
A61N001/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2000 |
WO |
PCT/CA00/01374 |
Claims
1. An artificial vision system for stimulating a visual cortex of a
blind person, comprising: a body implant including an electrode
array having multiple adjacent electrodes applicable against the
visual cortex of the blind person, and a micro-stimulator means
mounted on a back side of the electrode array, for selectively
generating stimulation signals on the electrodes producing
phosphenes on the visual cortex representing an artificial image in
response to airwave-received implant control signals; and an
external unit including an image sensor adapted to take a real
scene image, an image processor and command generator means
connected to the image sensor for processing image data signals
produced by the image sensor in accordance with predetermined
processing operations and generating implant compatible stimulation
commands causing the body implant to produce the artificial image
on the visual cortex corresponding to the real scene image, and a
transceiver circuit connected to the image processor and command
generator means, for producing airwave-transmitted implant control
signals carrying the stimulation commands, the processing
operations including a digitalization of the image data signals to
form a digital image, an image reduction of the digital image into
a scaled down image having a same resolution as the electrode
array, and an image enhancement of the scaled down image to form an
enhanced image corresponding to the artificial image produced by
the implant unit and from which the stimulation commands are
generated.
2. The artificial vision system according to claim 1, wherein the
image reduction comprises a determination of an average light
intensity on complementary areas of the digital image covering a
predetermined number of adjacent pixels, each one of the areas
corresponding to one of the electrodes of the electrode array, the
stimulation commands being produced as a function of the average
light intensity.
3. The artificial vision system according to claim 2, wherein the
image enhancement comprises a linear histogram equalization of the
scaled down image based on maximum and minimum pixel intensities
detected in the scaled down image.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/416,403, filed Nov. 16, 2000, which claims the benefit
under 35 USC 371 of international application PCT/CA00/01374, filed
Nov. 16, 2000, both of which are incorporated herein by reference
in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to body electronic implants,
and more particularly to a body electronic implant that can be used
to stimulate the visual cortex of a blind person for providing
artificial vision, or to stimulate other body organs or tissues or
nerves for other purposes, and that can also be used as a
monitoring instrument for diagnostic purposes.
BACKGROUND
[0003] Blindness is still nowadays difficult to cure. Technologies
such as speech synthesizers, 3D tactile displays and dedicated
scanners improve the quality of life of blind persons by allowing
them to read text and manipulate money. However, for seeing, the
situation is still the same as a hundred, or even a thousand years
ago.
[0004] Since electrical stimulation techniques are applied in many
circumstances to enhance or restore organ function, a few research
teams are working on the recuperation of a limited but functional
vision to totally blind persons. A functional vision means that the
person will be able to do, without assistance, most of the tasks
being part of every day life. It will be limited since no system in
the near future will be able to replace the natural vision system
with the same accuracy. The required resolution and data processing
capabilities are simply too large.
[0005] A person is considered legally blind if a visual dysfunction
is present and sufficient to greatly affect his everyday life. The
medical criterions vary from one country to another but, in
general, those who are considered legally blind include a specific
group of totally blind persons. This means that they do not see
anything and live in a world of complete darkness. The causes of
blindness are numerous. Some causes originate in the eye and others
are related to the visual pathways.
[0006] The history of human visual stimulation began in 1960 when
it was found that when a specific part of the human brain was
stimulated with an electrical current, a fixed light spot appeared
in the visual field of the patient. The part of the brain was later
identified as the visual cortex and the light spots are called
phosphenes. In 1968, results of clinical experiments related to
visual stimulation were first published. The experiments were done
with different voltage sources and spacing between electrodes
through an array of 81 platinum electrodes. In all cases, the
electrical stimulation was done on the surface of the visual
cortex. As research progressed, notable discoveries were made and
can be summarized as follows: current based intracortical
stimulation leads to a significant current reduction, more stable
phosphenes and a phosphene intensity that is proportional to the
current. To accomplish the visual stimulation, two main steps are
necessary. The first is to acquire a real life scene and generate
stimulation information, or stimulation command words. The second
is to inject the proper electrical current to do the stimulation
according to the command words.
[0007] There are at least three undertaken research activities
intended to create adequate vision using electrical stimulation.
Each one has its own distinctive characteristics, which are the
following:
[0008] 1) Retina stimulation, where an electrode array is inserted
into the light sensitive retina. The advantage of this method is to
use most of the natural visual pathway. It is an advantage but also
an inconvenience since the visual pathway must be intact and
functioning properly. Some of the best challenges of this method of
stimulation are mechanical. Since the electrode array is located on
the retina, it will be subjected to the very large angular
accelerations of the eye. The electrode array must be secured in
place very firmly to avoid damaging the retina. Furthermore, to
have a good contact with the retina, the electrode array must not
be planar but must match the spherical nature of the eye. This
approach seems to be dedicated to vision enhancement because the
visual pathway is intact. For example, it would be ideal for
patients losing the sensitivity of their peripheral vision.
[0009] 2) Cortical stimulation, where the electrode array is
inserted into the brain visual cortex. This method is also
dedicated to totally blind persons. Its only requirement is that
the visual cortex be intact, which seems to be the case more than
90% of the time. Research is under progress to determine long term
stimulation effects on the brain and cell damage due to a high
density of electrodes, but the preliminary results are encouraging.
A critical step to this method is the insertion of the electrode
array into the visual cortex. The current approach suggests a
pneumatic system.
[0010] 3) Optical nerve stimulation is a new stimulation strategy
recently introduced. Obviously, the visual pathway must be intact
from the optic nerve to the visual cortex. The exact nature of the
signals carried by the optic nerve is not thoroughly known and more
research is needed before feasibility can be demonstrated.
[0011] Known in the art are U.S. Pat. No. 4,551,149 (Sciarra); U.S.
Pat. No. 4,628,933 (Michelson); U.S. Pat. No. 5,159,927 (Schmid);
U.S. Pat. No. 5,215,088 (Normann et al.); U.S. Pat. No. 5,324,315
(Grevious); U.S. Pat. No. 5,324,316 (Schulman et al.); U.S. Pat.
No. 5,876,425 (Gord et al.); U.S. Pat. No. 5,800,535 (Howard, III);
U.S. Pat. No. 5,807,397 (Barreras); U.S. Pat. No. 5,873,901 (Wu et
al.); U.S. Pat. No. 5,935,155 (Humayun et al.); UK patent
application GB 2,016,276 assigned to W H Ross Foundation (Scotland)
for Research into Blindness and published on Sep. 26, 1979; and
Canadian patent no. 908,750 (Brindley et al.) issued on Aug. 29,
1972, depicting the state of the art.
[0012] The above patent documents show that various implants have
been designed, at least on a theoretical basis. However, many
problems arise when the time comes to put them into practice.
Difficulties in the production of electronic implants lay for
example in the integration of the various required functions and
the miniaturisation of the whole system. The existing implants
exhibit high power consumption as they are built using separate
electronic modules that further take significant space. The RF
part, operating at high speed, is generally made with discrete
electronic components due to the electromagnetic interferences
generated by this part; it is thus not integrated with the rest of
the implant circuit, which would otherwise allow a reduction of the
dimensions and the power consumption of the implant. Since an
implantable system with discrete components has a high power
rating, its power supply by an inductive link is thus hardly
practicable. A few designs group the electronics and the electrodes
on the same silicon slice. This method facilitates achievement of a
vector of a few electrodes, but its application to a large number
of electrodes in an array format remains to be proven. The
efficiency of an inductive coupling to supply the implantable part
of the system is very low because the majority of the currently
used techniques are based on ASK modulation. This low efficiency
prevents the integration of all the desired functions in the same
implant when discrete component designs are used.
[0013] The implants used for electric stimulation purposes are thus
far unable to monitor changes on the electrode-tissue interface.
Such a monitoring function is however highly desired to monitor and
follow the evolution of the milieu in contact with the implanted
system. The majority of the existing systems are unable to process
a large number of inputs and outputs (many tens and hundreds); they
are mostly designed for a few stimulation channels only, e.g. for a
10.times.10 array of electrodes. Furthermore, the assembly of
implant electronics with an electrode array having a large number
of electrodes in a surface having reduced dimensions has so far not
received much attention in the art, as for some other aspects
related to implants and implant systems.
SUMMARY
[0014] An object of the present invention is to provide a body
electronic implant which may be used as a stimulating implant on
the visual cortex to provide artificial vision to a blind person,
or for other applications such as a monitoring device for
implantable biomedical measurements, and especially for measuring
parameters around an electrode-neuronal tissues interface.
[0015] Another object of the present invention is to provide a body
implant which is sufficiently miniaturized and has an integration
level adapted for full and direct fitting into the cerebral cortex,
at the back of the head of a user, yet which is highly
configurable, functionally flexible and has a low power
consumption.
[0016] Another object of the present invention is to provide a body
implant assembly combining a full custom mixed-signal chip and a
large number of electrodes fitting on a surface having reduced
dimensions.
[0017] Another object of the present invention is to provide a body
implant capable of storing preset stimulation parameters actively
useable with real-time incoming specific stimulation parameters to
form the stimulation signals, thereby relieving external
unit-implant real-time communications.
[0018] Another object of the present invention is to provide a body
implant capable of monitoring changes on the electrode-tissue
interface through voltage, current and impedance measurements, and
capable of reporting these changes to the external unit for
diagnosis and adjustment purposes.
[0019] Another object of the present invention is to provide an
implant system based on the above implant, and which can process
real scene images for improved stimulation over an electrode array
having a limited resolution.
[0020] According to the present invention, there is provided a body
implant assembly comprising:
[0021] an electrode array having multiple adjacent electrodes
directed towards respective stimulation sites;
[0022] an antenna;
[0023] a full custom mixed-signal chip including a transceiver
circuit coupled to the antenna, an AC to DC voltage transformation
circuit coupled to the transceiver circuit and powering the full
custom mixed-signal chip from energy contained in a control signal
received by the transceiver circuit, a controller connected to the
transceiver circuit and processing operation data contained in the
control signal received by the transceiver circuit, and a stimuli
generator circuit connected to the controller and generating
stimulation signals in accordance with the operation data;
[0024] an electrode selection circuit connected to the stimuli
generator circuit and having selectable outputs for transmission of
the stimulation signals to selected ones of the electrodes in
accordance with the operation data; and
[0025] a substrate support having a first side receiving the full
custom mixed-signal chip, the antenna and the electrode selection
circuit, and a second, opposite side receiving the electrode array,
the first side having contacts lying around the full custom
mixed-signal chip and connected to the outputs of the electrode
selection circuit respectively, the second side having an array of
adjacent contacts aligned with and connected to the electrodes
respectively, the contacts on the first and second sides being
interconnected respectively together by an interconnection circuit
across the substrate support.
[0026] According to the present invention, there is also provided a
body implant comprising:
[0027] an electrode array having multiple adjacent electrodes
directed towards respective stimulation sites;
[0028] an antenna;
[0029] a transceiver circuit coupled to the antenna;
[0030] an AC to DC voltage transformation circuit coupled to the
transceiver circuit and providing implant power supply from energy
contained in an implant control signal received by the transceiver
circuit;
[0031] a controller connected to the transceiver circuit and
processing operation data contained in the implant control signal
received by the transceiver circuit;
[0032] a stimuli generator circuit connected to the controller and
generating stimulation signals in accordance with the operation
data; and
[0033] an electrode selection circuit connected between the stimuli
generation circuit and the electrode array, the electrode selection
circuit having selectable outputs for transmission of the
stimulation signals to selected ones of the electrodes in
accordance with the operation data;
[0034] the controller having a decoder circuit decoding the
operation data contained in the implant control signal, a
configuration controller storing common and specific stimulation
parameters specified in the operation data and respectively
addressed to all of the stimulation sites and specific ones of the
stimulation sites, and a stimulation command controller
transmitting stimulation control signals to the stimuli generator
circuit in accordance with the common and specific stimulation
parameters.
[0035] According to the present invention, there is also provided a
body implant comprising:
[0036] an electrode array having multiple adjacent electrodes
directed towards respective stimulation sites;
[0037] an antenna;
[0038] a transceiver circuit coupled to the antenna;
[0039] an AC to DC voltage transformation circuit coupled to the
transceiver circuit and providing implant power supply from energy
contained in an implant control signal received by the transceiver
circuit;
[0040] a controller connected to the transceiver circuit and
processing operation data contained in the implant control signal
received by the transceiver circuit;
[0041] a stimuli generator circuit connected to the controller and
generating stimulation signals in accordance with the operation
data;
[0042] an electrode selection circuit connected between the stimuli
generation circuit and the electrode array, the electrode selection
circuit having selectable outputs for transmission of the
stimulation signals to selected ones of the electrodes in
accordance with the operation data; and
[0043] a monitoring unit coupled between the controller and the
electrode selection circuit, and controllably taking signal
measurements at selected ones of the stimulation sites in response
to monitoring control signals and producing test result signals
indicative of the signal measurements;
[0044] the controller having a decoder circuit decoding the
operation data contained in the implant control signal, a
monitoring command generator decoding diagnosis instructions
contained in the operation data and transmitting the monitoring
control signals to the monitoring unit in accordance with the
diagnosis instructions, and a diagnosis controller receiving and
processing the test result signals from the monitoring unit.
[0045] According to the present invention, there is also provided a
body implant comprising:
[0046] an electrode array having multiple adjacent electrodes
directed towards respective measurement sites;
[0047] an antenna;
[0048] a transceiver circuit coupled to the antenna;
[0049] an AC to DC voltage transformation circuit coupled to the
transceiver circuit and providing implant power supply from energy
contained in an implant control signal received by the transceiver
circuit;
[0050] a controller connected to the transceiver circuit and
processing operation data contained in the implant control signal
received by the transceiver circuit;
[0051] an electrode selection circuit connected to the electrode
array, the electrode selection circuit having selectable outputs
for communication with selected ones of the electrodes and the
respective measurement sites; and
[0052] a monitoring unit coupled between the controller and the
electrode selection circuit, and controllably taking signal
measurements at the selected ones of the measurement sites in
response to monitoring control signals and producing test result
signals indicative of the signal measurements;
[0053] the controller having a decoder circuit decoding the
operation data contained in the implant control signal, a
monitoring command generator decoding diagnosis instructions
contained in the operation data and transmitting the monitoring
control signals to the monitoring unit in accordance with the
diagnosis instructions, and a diagnosis controller receiving and
processing the test result signals from the monitoring unit.
[0054] According to the present invention, there is also provided a
body implant comprising:
[0055] an electrode array having multiple adjacent electrodes
directed towards respective stimulation sites;
[0056] an antenna;
[0057] a transceiver circuit coupled to the antenna;
[0058] an AC to DC voltage transformation circuit coupled to the
transceiver circuit and providing implant power supply from energy
contained in an implant control signal received by the transceiver
circuit;
[0059] a controller connected to the transceiver circuit and
processing operation data contained in the implant control signal
received by the transceiver circuit;
[0060] a stimuli generator circuit connected to the controller and
generating stimulation signals in accordance with the operation
data; and
[0061] an electrode selection circuit connected between the stimuli
generation circuit and the electrode array, the electrode selection
circuit having selectable outputs grouped into channels for
transmission of the stimulation signals to selected ones of the
electrodes in accordance with the operation data;
[0062] the electrode selection circuit including, for each channel,
a demultiplexer circuit connected to and operating switch
arrangements in accordance with site and polarity control signals,
the switch arrangements being subjected to the stimulation signals
and connected respectively to the outputs assigned to the
channel;
[0063] the stimuli generator circuit including, for each channel, a
signal generator controlled by a channel controller assisted by a
timer connected to a register circuit receiving stimulation control
signals, the signal generator producing the stimulation signals in
accordance with the stimulation control signals, the register
circuit and the channel controller producing the site and polarity
control signals in accordance with the stimulation control signals;
and
[0064] the controller having a decoder circuit decoding the
operation data contained in the implant control signal, a
configuration controller storing stimulation parameters specified
in the operation data, and a stimulation command controller
transmitting the stimulation control signals to the stimuli
generator circuit in accordance with the stimulation
parameters.
[0065] According to the present invention, there is also provided
an artificial vision system for stimulating a visual cortex of a
blind person, comprising:
[0066] a body implant including an electrode array having multiple
adjacent electrodes applicable against the visual cortex of the
blind person, and a micro-stimulator means mounted on a back side
of the electrode array, for selectively generating stimulation
signals on the electrodes producing phosphenes on the visual cortex
representing an artificial image in response to airwave-received
implant control signals; and
[0067] an external unit including an image sensor adapted to take a
real scene image, an image processor and command generator means
connected to the image sensor for processing image data signals
produced by the image sensor in accordance with predetermined
processing operations and generating implant compatible stimulation
commands causing the body implant to produce the artificial image
on the visual cortex corresponding to the real scene image, and a
transceiver circuit connected to the image processor and command
generator means, for producing airwave-transmitted implant control
signals carrying the stimulation commands, the processing
operations including a digitalization of the image data signals to
form a digital image, an image reduction of the digital image into
a scaled down image having a same resolution as the electrode
array, and an image enhancement of the scaled down image to form an
enhanced image corresponding to the artificial image produced by
the implant unit and from which the stimulation commands are
generated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] A detailed description of preferred embodiments will be
given hereinbelow with reference to the following drawings, in
which like numbers refer to like elements:
[0069] FIGS. 1, 2 and 3 are, respectively, schematic views of front
and rear sides of a substrate support of a body implant assembly
and an exploded view thereof with an electrode array according to
an embodiment of the present invention;
[0070] FIGS. 4, 5 and 6 are, respectively, schematic views of front
and rear sides of a substrate support of a body implant assembly
and an exploded view thereof with an electrode array according to
another embodiment of the present invention;
[0071] FIG. 7 is a schematic diagram of a body implant system
according to an embodiment of the present invention;
[0072] FIGS. 8, 9, 10 and 11 are schematic diagrams of the internal
controller, the stimuli generation circuit, the monitoring circuit
and the electrode selection circuit of a body implant according to
the present invention;
[0073] FIG. 12 is a schematic diagram illustrating a possible
format of a communication protocol for a body implant according to
the present invention;
[0074] FIG. 13 is a schematic diagram illustrating possible
definitions of parameters in the registers of an internal
controller of a body implant according to the present
invention;
[0075] FIG. 14 is a schematic diagram illustrating a stimulation
mode command format for a body implant according to the present
invention;
[0076] FIG. 15 is a schematic diagram illustrating a diagnosis mode
command format for a body implant according to the present
invention;
[0077] FIG. 16 is a schematic diagram illustrating a power
management mode command format for a body implant according to the
present invention;
[0078] FIG. 17 is a schematic diagram illustrating an image
processing sequence performed by an image processor for command
word generation for implant control according to the present
invention;
[0079] FIGS. 18A-B and 19A-B are schematic diagrams illustrating
scaled-down and enhanced images generated by an image processor and
the corresponding histograms respectively, according to the present
invention;
[0080] FIG. 20 is a schematic diagram illustrating a screen capture
of an external unit user interface according to the present
invention; and
[0081] FIG. 21 is a schematic diagram illustrating a body implant
artificial vision system worn by a user according to the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0082] Referring to FIG. 21, there is shown a body implant system
worn by a user 2 according to the present invention, in the context
where the user 2 is a blind person and the system is used to
provide artificial vision to the user 2. It should be understood
that this context exemplifies a typical use of the implant system
according to the present invention, and should not be taken in a
limitative or restrictive sense, as the implant system may be used
in many other contexts, for example for monitoring purposes, and
especially for measuring parameters around an electrode-neuronal
tissues interface.
[0083] The body implant system includes two main parts: an implant
4 positioned on the visual cortex of the user 2, and an external
unit 6 that can be inserted in a pocket and which acquires real
life scenes, processes the image information and communicates with
the implant 4 to provide energy for powering the implant 4 and to
control it in order to stimulate the visual cortex of the user 2
through an electrode array used to generate phosphenes in the
visual field corresponding to a transposition of the real life
scenes. The real life scenes can be acquired through a camera 8
(e.g. a CMOS image sensor) mounted on an earpiece of an eyeglass,
while the implant energy and control signals can be transmitted
through an inductive link using an antenna 10 positioned behind the
head of the user 2.
[0084] Referring to FIGS. 1-6, there are shown two embodiments of
the body implant assembly according to the present invention. These
embodiments feature integration of most of the electronic
components of the implant in a single full custom mixed-signal chip
12, thereby reducing power consumption and size of the circuit.
Furthermore, a special interconnection circuit is provided for
interconnection of the chip 12 with a high resolution electrode
array 14 having multiple adjacent electrodes 16, e.g. a 25.times.26
array=650 electrodes made of biocompatible materials, having an
average height of approx. 1,5 mm, spaced by approx. 400 .mu.m from
one another and extending over a very small area, e.g. 1 cm.sup.2.
The resulting implant assembly is thus highly miniaturized compared
to prior art implants, and the interconnection circuit provides
individual connections to every electrode 16. The electrode array
14 can be made of several smaller electrode arrays assembled
together (not shown), instead of a larger single array if
desired.
[0085] Referring to FIGS. 1-3, the chip 12 is embedded on a side of
a very thin substrate support 14 having contacts 17 lying around
the chip 12, at a given distance therefrom. These contacts 17 are
respectively connected to the pads 18 of the chip 12 for example by
a wire bond 24. The other side of the substrate support 14 is
provided with an array of adjacent contacts 20 aligned with and
connected to the electrodes 16 respectively. The connection of the
contacts 20 with the electrodes 16 can be achieved by cold welding
or any other suitable technique. The contacts 17 and 20 on both
sides of the substrate support 14 are interconnected respectively
together by an interconnection circuit 22 across the substrate
support. Depending on the number of links to achieve, the
interconnection circuit 22 may be formed of layers made in the
substrate support 14 and stacked between the sides thereof. To
reduce the space taken by the contacts 17, they may be distributed
in an alternate shifted pattern over two or more adjacent sets of
rows surrounding the chip 12. The body implant assembly resulting
from this embodiment is thus very thin for a reasonable cross
section. An antenna 34 extends on the substrate support 14 around
the chip 12 for communication with the external unit 6. The antenna
34 is connected to pads 18 of the chip 12 assigned for this
purpose. A capacitor 36 is coupled to the antenna 34 for proper
operation. Other suitable antenna configurations may be used.
[0086] Referring to FIGS. 4-6, the substrate support 14 may be
formed of a front relatively flat portion 26 having however a
smaller cross section than the substrate support 14 in the former
embodiment, and a smaller rear portion 28 projecting behind the
front portion and receiving the electrode array 14. As in the
former case, the contacts 17 on the foremost face of the front
portion 26 are connected respectively to the pads 18 of the chip
12. The contacts 17 however also project through and appear behind
the front portion 26. The interconnection circuit in this case has
a series of peripheral contacts 30 surrounding the array of
adjacent contacts 20 on the rearmost face of the rear portion 28.
The peripheral contacts 30 and the contacts 17 appearing behind the
front portion 26 are respectively connected together by a wire bond
32. Circuit layers of suitable designs made in the rear portion 28
and stacked between the rearmost and foremost face thereof
interconnect the peripheral contacts 30 with the array of adjacent
contacts 20 respectively. The body implant assembly resulting from
this embodiment is thus thicker than in the former embodiment, but
as a smaller cross-section.
[0087] In both of the above embodiments, the body implant assembly
can be made from a silicon die containing all the electronic
circuitry necessary to receive command words, detect and correct
transmission errors, decode the command words and control the
stimulation process accordingly.
[0088] Referring to FIG. 7, the full custom mixed-signal chip 12
preferably integrates a FM bi-directional data transfer &
energy receiver 38, a controller 40, a stimuli generator unit 44,
an optional but generally desirable monitoring unit 46, and
depending on the chosen design, an electrode selection circuit 48
or not as it can also be provided as a separate circuit from the
chip 12 as depicted by the dotted lines 202, then forming another
full custom chip.
[0089] The receiver 38 recovers high frequency AC signal from the
implant control signal emitted by the external unit 6, and
transforms it to a DC voltage. This DC voltage is used to power up
the whole implant. The receiver 38 recovers also clock and data
from the same implant control signal emitted by the external unit
6, and transmits it to the internal controller 40. The receiver 38
gets feedback data from the internal controller 40 and transmits it
to the user through the inductive link depicted by arrows 42. The
receiver 38 thus acts as a transceiver. Although the feedback
function is likely to be indispensable in most applications, it can
nevertheless be omitted if it is really useless for a specific
application.
[0090] The controller 40 decodes the commands generated by the
external unit 6 in order to produce all control signals to the
stimuli generator unit 44 and the monitoring unit 46.
[0091] Referring to FIG. 8, the controller 40 may be embodied by a
circuitry mainly containing 12 units, which are grouped into 3 main
sections: a main controller module 50, a stimulation controller
module 52, and a diagnosis controller module 54. The main
controller module 50 detects data frames and corrects communication
errors, if present, in order to build the command words used by the
other modules in the controller 40. This can be achieved through a
serial/parallel converter & frame detector 56 and an error
correction & command word decoder 58.
[0092] A power management module 60 (PMM) can be provided to turn
other modules, units, or stimulation channels on or off
individually to keep power consumption to a minimum at any given
time. Only the PMM 60 itself and the two previous modules 56, 58,
necessary for command reception, are not susceptible to being
turned off. Turning a module off means lowering its power
consumption down to zero, but does not imply a real shut down of
the unit, keeping programmed parameters valid where volatile memory
is used. For sake of clarity, only few of the many control lines to
the controller's internal modules are presented in FIG. 8.
[0093] A configuration controller 62 preferably keeps every
communication, stimulation, and diagnosis parameter programmed by
the user by means of registers CRO-CR8, and makes them available
for other modules or units. A Power-On-Reset function controlled by
the main controller 50 can be implemented.
[0094] A proper knowledge of the communication protocol for the
implant as set forth hereinafter might be important for
understanding the following part.
[0095] The stimulation controller module 52 has a Random Access
Memory 64 (RAM) intended to keep a stimulation channel/site address
sequence programmed by the external unit 6 during the configuration
process.
[0096] A stimulation commands generator 66 (SCG) decodes the
stimulation instructions and sends the required control signals to
the stimuli generator unit 44 (as shown in FIG. 7), according to
programmed shared stimulation parameters, if applicable.
[0097] A clock signal 68 whose frequency depends on a specific
programmed parameter SCTB stored in the register CR3 is used for
stimulation by the stimuli generator unit 44 and is generated by a
stimulation clock module 70.
[0098] The diagnosis controller module 54 has a monitoring commands
generator 72 (MCG) which decodes the diagnosis instructions related
to the analog monitoring of the stimulation system and
electrode/tissue condition, and sends the required control signals
to the monitoring unit 46 (as shown in FIG. 7), according to the
programmed options/parameters.
[0099] A clock signal 74 whose frequency depends on a specific
programmed parameter MCTB stored in the register CR5 is used for
monitoring purposes by the monitoring unit 46 and is generated by a
monitoring clock module 76.
[0100] A diagnosis controller 78 (DC) transmits test vectors sent
by the external unit 6 upon request to any module and units, and
receives test results thereof, both from digital tests and from
analog monitoring performed by the monitoring commands generator
72. The DC 78 also sends the results back to the external unit 6,
via parity insertion & return word encoder and parallel/serial
converter modules 80, 82. For sake of clarity, only a few of the
many control lines to the controller's internal modules are
presented in this FIG. 8.
[0101] Referring to FIG. 9, the stimuli generator unit 44 may be
embodied by a circuitry composed of 25 individual and independent
channel stimuli generators 84 (CSG). Each of the CSG 84 has a
channel controller 86 (CC), a timer module 88 and a current digital
to analog converter 90 (DAC).
[0102] Two sets of registers 92, 94 allow to load the next
stimulation parameters while the current ones are used, thereby
eliminating delays between two successive stimulations. Not shown
are the diagnosis signals to/from the controller's diagnosis
controller module 78 (see FIG. 8) for testability and the power
management control signals from the power management module 60.
[0103] Referring to FIG. 10, the monitoring unit 46 may be embodied
by a circuitry having the necessary sources and measurement modules
to perform real/time continuous stimulation supervision and
detailed voltage/current/complex impedance measurement for detailed
diagnosis.
[0104] During normal stimulation, continuous monitoring can be
performed by constantly comparing the peak voltage Vpk across any
monitored stimulation site Prb0, Prb1 to a maximum reference
voltage VRef, through comparator 96. If the monitored voltage
exceeds the reference, the channel over-flow signal ChanOF is
activated and the channel on which the problem arose is stored in a
register 98 DefChan. The reference signal VRef is set by the
maximum allowed current and impedance between any stimulation site
monitored by the DAC 100 and in accordance with the parameter
CalRes stored in the register CR6 of the configuration controller
62 shown in FIG. 8 and sent to the calibration channel decoder 102
shown in FIG. 11.
[0105] Many options are available for detailed diagnosis. The
source may be either internal, then using the DAC 100 for this
purpose, or external and then using any of the channel's DAC 90
shown in FIG. 9, as selected by the MonSrc signal produced by the
demultiplexer 104 and operating the transistor arrangements 106
shown in FIG. 11. A waveform shaper 108 may be used to provide an
unaltered square wave or a sine shaped wave for testing purposes.
An output stage 110 provides the electrode array 14 with a
stimulation current MonStim transmitted to the transistor
arrangements 106 and provides the monitoring circuit 46 with an
accurate voltage dependent copy of the stimulation current, which
may be measured via a current controlled oscillator 112, whose
range can be modified according to the input signal level OscRng
derived from the parameter OCR stored in the register CR7 of the
configuration controller 62 shown in FIG. 8. Any sampled voltage
across the monitored site can be measured with the same oscillator
112 through a transconductance amplifier 114 with variable gain for
various input voltage ranges as set by the signal GmRng. The peak
magnitude of the voltage across the monitored site can be measured
by means of a peak detector 116. The phase between the stimulation
current and the monitored voltage can be measured through a phase
detector 118 and a frequency and phase estimator 120 for complex
impedance measurements. A monitoring unit controller 166 controls
most of the components of the monitoring unit 46 in accordance with
the various control signals produced by the monitoring commands
generator 72 (see FIG. 8). A sample and hold circuit 168 is
provided for the transconductance measurement.
[0106] Not shown are the diagnosis signals to/from the controller's
diagnosis controller 78 (see FIG. 8) for testability and the power
management control signals from the power management module 60.
[0107] It should be noted that in the case where the implant 4 is
intended to be used solely for monitoring purposes, then all the
circuits of the implant 4 with functions only related to the
generation of stimulation signals can be removed from the implant 4
inasmuch as no stimulation signals are required. Such is the case
when the implant 4 is used for example to monitor certain body
organs producing measurable electric signals to be monitored. For
example, the DACs 90 and 100 (see FIG. 10), and the stimulation
commands generator 66 (see FIG. 8) can be omitted in such a
case.
[0108] Referring to FIG. 11, the electrode selection circuit 48 can
be embodied by a multiplexor/demultiplexor circuitry comprising 25
selection channels 122 provided with channel decoders 126 for
activating up to 25 sites simultaneously. Each site can be
activated in both directions by means of switch arrangements 124,
depending on the sign bit (signal Sign #x) for every channel.
[0109] A test channel decoder 128 selects which channel has to be
monitored. When a specific channel is monitored, the current from
the corresponding channel stimuli generator 84 in the stimuli
generator unit 44 is deviated to the monitoring unit 46 through the
MonSrc line 130 and the stimulation current comes from that latter
unit through the MonStim line 132. The channel stimuli generator 84
is notified that its channel is being monitored with the MonChan#x
signal transmitted to corresponding the channel controller 86.
[0110] The electrode selection circuit 48 may be provided with a
calibration channel circuit formed of the channel decoder 102 and a
calibration network 134 and used by the analog monitoring unit 46.
The calibration channel decoder 102 selects an appropriate known
resistive element value. This is also used in the continuous
monitoring process, generating the appropriate reference limit
voltage VRef.
[0111] Sets of analog multiplexers 136 provide the monitoring unit
46 with the voltage across any pair of electrodes through the PrbO
and Prb1 lines 138, 140.
[0112] Referring to FIG. 12, there is shown a possible format of a
communication protocol for the body implant according to the
present invention. In the illustrated case, the command words 142
are 26 bits long or less and are composed of three parts, the mode
identification bits 144,the instruction 146 and the data 148. Note
that each instruction 146 can contain one or several parts,
depending on the selected mode.
[0113] A session usually starts with a configuration process. Then
the stimulation period can start, according to the programmed
configuration parameters 148 transmitted by the external unit 6. If
a problem arises, the diagnosis mode allows a monitoring of both
analog and digital components of the system. Finally, at any time,
the power management mode enables the external unit 6 to turn on or
off any component for reduced power consumption.
[0114] The configuration mode set by the command word
<1,0>==00 allows to define several variable parameters
related to stimulation or monitoring.
[0115] The first five configuration registers CR0 to CR4 of the
configuration controller 62 (see FIG. 8) define the communication
protocol during stimulation. The next four registers CR5 to CR8
define many diagnosis parameters, the first three being dedicated
to the analog monitoring and the last one relating to digital
diagnosis of the system.
[0116] Referring to FIG. 13, the definition of the parameters in
the registers CRO-CR8 is as follows. The Partial Stimulation Word
Chain Length (PSWCL) parameter defines the number of sequential
stimulation words that are sent without interruption. The Amplitude
Flag (AF) parameter defines whether the stimulation current
amplitude is specific or common for every site. The Amplitude Word
Length (AWL) parameter defines the number of bits specifying the
amplitude of the stimulation current. The Pulse Duration Flag (PDF)
parameter defines if the stimulation current pulse duration is
specific or common for every site. The Pulse Duration Word Length
(PDWL) parameter defines the number of bits specifying the pulse
duration of the stimulation current. The Interphase Duration Flag
(IDF) parameter defines if the delay between the two phases of the
stimulation current is specific or common for every site. The
Interphase Duration Word Length (IDWL) parameter defines the number
of bits specifying the delay between the two phases of the
stimulation current. The Common Amplitude (CAMP) parameter defines
the amplitude of the stimulation current if this parameter is
common for every site. The Common Pulse Duration (CPD) parameter
defines the pulse duration of the stimulation current if this
parameter is common for every site. The Common Interphase Duration
(CID) parameter defines the delay between the two phases of the
stimulation current if this parameter is common for every site. The
Stimulation Clock Time Base (SCTB) parameter defines the frequency
of the stimulation clock 70 shown in FIG. 8. The Stimulation
Sequence Channel (SSC) and the Stimulation Sequence Site (SSS)
parameters are used to fill the Stimulation Sequence RAM 64 shown
in FIG. 8. The Low Pass Filter Cut-off Frequency (LPFCF) parameter
defines the cut-off frequency of the Gm-C low-pass filter 150 shown
in FIG. 10 in the monitoring unit 46. The Monitoring Clock Time
Base (MCTB) parameter defines the frequency of the monitoring clock
76 in the controller 40 (see FIG. 8). The Monitoring DAC Amplitude
(MDACA) parameter defines the amplitude of the output current of
the DAC 90 (FIG. 9) for continuous monitoring. The Calibration
Resistor (CALRES) parameter defines the reference equivalent
resistor in the calibration network 134 for continuous monitoring
(see FIG. 11). The Transconductance Range (GMR) parameter defines
the gain of the transconductance amplifier 114 (see FIG. 10). The
Oscillator Current Range (OCR) parameter defines the input current
range of the current controlled oscillator 112 (see FIG. 10). The
Unit/Module Under Test (UMUT) parameter defines the unit or module
under test for digital diagnosis. The Scan Chain Length (SCL)
parameter defines the number of bits of the scan chain in the unit
or module under test. The Stimulation clock Sync (SS) parameter
synchronizes the stimulation clock 70 (FIG. 8). The Monitoring
clock Sync (MS) parameter synchronizes the monitoring clock 76
(FIG. 8). The RAM Reset (RR) parameter resets the address pointer
of the 10 Stimulation Sequence RAM 64 (FIG. 8) to zero. The
Continuous Monitoring (CM) parameter turns the continuous
monitoring feature of the controller 40 (FIG. 7) on/off.
[0117] Referring to FIG. 14, in the stimulation mode set by the
command word <1,0>==01, the instruction 152 depends directly
on the stimulation communication protocol defined in the
configuration. The instruction 152 is sent as a chain of a certain
number (PSWCL) of stimulation words, each containing 1 to 34 bits,
depending on the common parameters. If the chain is longer than 24
bits, it is divided into sequential stimulation instruction words
of 24 bits or less for the last word.
[0118] Referring to FIG. 15, the diagnosis mode set by the command
word <1,0>==10 allows detailed and various analyses of the
condition of the system, on both the digital and analog sides. When
the first bit of the diagnosis instruction word 154 is set in a low
state 156, the following data is used to determine the information
required for analog monitoring. The instruction is then composed
of: a Monitored Site (MS) parameter, a Monitored Channel (MC)
parameter, a Monitoring current Amplitude (MAMP) parameter, and a
Monitoring Options (MOPT) parameter. The MOPT parameter specifies
what the stimulation source is, what the stimulation waveform is,
if the measured value is a current, if the measured value is a
voltage, and if the measured value is the phase between current and
voltage.
[0119] When the first bit of the diagnosis instruction word 154 is
set in a high state 158, the diagnosis concerns the digital system.
To input a test vector, the next bit is set to a low state and the
vector 160 itself follows. If the length of the test vector is
longer than 22 bits as defined by the SCL parameter in the
configuration mode, the 23rd and next bits are sent in a subsequent
similar diagnosis instruction word.
[0120] To read the data in a particular module of the system, both
the first and second bit of the diagnosis instruction word are set
in a high state 162. The controller will then send the test result
back to the external unit 6.
[0121] Referring to FIG. 16, the power management mode set by the
command word <1,0>==11 allows to turn any component of the
system on and off. The two parameters supplied in this mode are the
power management action (PA), which defines if the unit/module has
to be turned on/off, and the unit/module identification (MID) that
defines which unit/module the power management action has to be
applied to.
[0122] As mentioned hereinabove, the stimulation biphasic current
pulses used to generate a phosphene can be described by three
parameters, which are the amplitude, the phase duration and the
inter-phase duration of the pulses. Each one of theses parameters,
as well as the pulse frequency, influences the phosphenes visual
appearance. It would require a high data transmission rate to send
in real time all the stimulation parameters as well as the
addresses of the corresponding stimulation sites from the external
unit 6 to the implant 4. In order to reduce this rate, the needed
stimulation data can be transferred as follows. First, each of the
parameters is, beforehand, defined to be common or specific. A
common parameter is shared by all the stimulation sites and has to
be loaded only once at the beginning. However, the specific
parameters have to be updated at each activation site. As an
example, the phase and inter-phase durations can be common, and the
amplitude can be specific. Using one or two common parameters
allows a significant reduction in the transmission rate between the
external unit 6 and the implant 4. The choice of which parameters
are common or specific, as well as the number of bits necessary to
specify each one of them can be set at any time in the
configuration mode.
[0123] Secondly, instead of sending the stimulation site address
with each parameter, the RAM 64 (FIG. 8) is used. During the
configuration phase of the implant 4, the external unit 6 fills the
memory 64 with the scan sequence of each frame in an image that
will be used by both devices (the implant 4 and the external unit
6). The stimulation parameters are then sent in the order specified
in the memory 64.
[0124] This kind of transfer of the needed data makes the implant 4
highly configurable, allowing the external unit 6 to fully control
the stimulation operations and allowing a higher frame (image)
transmission rate, if needed.
[0125] Referring to FIG. 8, in operation, the stimulation commands
generator 66 combines the common parameter data with each specific
stimulation word to generate the proper stimulation control signals
for the stimuli generator unit 44, indicating in particular the
amplitude of the biphasic pulse (StimAmp), the phase duration of
the pulse (PhaseDur), the interphase duration of the pulse
(InterDur), the stimulation site address (StimSite), the
stimulation channel number (StimChan).
[0126] Referring to FIG. 9, when a particular channel controller 86
receives the stimulation control signals, it loads the data into
the set of temporary registers 92. Once the previous stimulation is
completed, the data are transferred into the main registers 94 as a
result of a control performed by the channel controller (Idnp and
ldcp signals). The DAC 90 is responsive to the channel controller
86 (Stim signal) and generates a stimulation current having an
amplitude depending on the StimAmp value. The stimulation operation
begins using the site address bus 164 to select the proper site in
the channel and the Stim signal to start and stop stimulation. The
channel controller 86 uses the timer 88 based on the stimulation
clock 70 (FIG. 8) to set the phase and interphase durations of the
pulses.
[0127] Referring to FIG. 7, the external unit 6 has an image
processor and command generator module 174 connected to the camera
8 for processing image data signals corresponding to a real life
scene captured by the camera 8, in accordance with predetermined
processing operations, and for generating implant compatible
stimulation commands causing the implant 4 to produce the
artificial image on the visual cortex corresponding to the real
scene image. A transceiver module 176 preferably in the form of a
FM bi-directional data transfer and energy transmitter is connected
to the image processor and command generator module, for producing
airwave-transmitted implant control signals carrying the
stimulation commands, as depicted by the arrows 42. The external
unit 6 is preferably powered by a battery 204.
[0128] Referring to FIGS. 7 and 17, the processing operations
performed by the image processor and commands generator 174 on the
real life scene 170 subjected to acquisition 178 by the camera 8
can be a digitalization of the image data signals to form a digital
image 180, an image reduction of the digital image 180 into a
scaled down image 182 having a same resolution as the electrode
array 14, and an image enhancement of the scaled down image 14 to
form an enhanced image 184 corresponding to the artificial image
produced by the implant unit 4 and from which the stimulation
commands 186 are generated.
[0129] The external unit 6 may be provided with a pattern
generation interface (not shown) where the command words are formed
from internal patterns instead of the image sensor 8. Such a
feature would allow to quickly test recognizable patterns like a
square, a circle or a cross for adjustment of the implant 4 to the
user 2.
[0130] Once the image 182 has the proper resolution, basic image
enhancement techniques are preferably applied. The purpose of the
enhancement is to give to the image more balanced contrasts and
luminosity. The applied technique can be a linear histogram
equalization consisting of stretching the image histogram to cover
the totality of the available pixel intensity spectrum. It is not
necessary to calculate the whole histogram since only the minimum
and maximum pixel intensities are useful. With those values, a
look-up table can be built to transform, one by one, each pixel of
the initial image.
[0131] FIGS. 18A-B and 19A-B illustrate scaled-down and enhanced
images generated by the image processor 174 (FIG. 7), and the
corresponding histograms respectively. As it can be seen, the
histogram shown in FIG. 19B, corresponding to the enhance image
shown in FIG. 19A, covers a wider spectrum than the histogram shown
in FIG. 18B for the image prior to enhancement as shown in FIG.
18A.
[0132] After the image enhancement, each pixel of the resulting
image will represent a phosphene that should be created during the
cortex stimulation. To create this phosphene, a command word must
be created to specify every stimulation parameter, from waveform
shape to phase delay. Since many of the parameters affect only the
qualitative part of phosphene appearance and the effects of their
modification is not currently thoroughly known, those parameters
must be easily and quickly alterable. In addition, when stimulating
biological cells with an electrical current, the stimulation of the
same cells, or cells in the surrounding, cannot be repeated before
a delay of few ms. This delay is called repolarization time. For
this reason, serial scanning cannot be used for the stimulation of
the cortex in order to create an image. Instead, a scan sequence
must be selected in such a way that each sequential stimulation is
not executed in an area where a stimulation occurred before the
repolarization time is elapsed. The flexibility of the implant
system according to the invention allows the use of any desired
scanning sequence and the configuration of the implant 4 with the
same sequence.
[0133] Referring to FIGS. 7 and 20, the external unit 6 may be
provided with a communication port 188 for communication with a
computer (not shown) for configuration and test purposes. For
example, to test the system, easily recognizable shapes may be used
to test the phosphene apparition parameters, as mentioned
hereinabove. Those shapes can be generated by the external unit 6
in response to a test request issued by the computer, as inputted
through a user interface 190. The user can select different
patterns 192 and adjust the parameters 194 on the fly. For example,
a square, a cross or a circle may be selected, each of which can be
in a solid or outline form. Character generation can also be
implemented to enable more complex shapes. For greater user
control, those patterns may bypass the usual data pathway and
directly generate the command words in the external unit 6.
[0134] The user interface 190 may display a source image 196 as
captured by the camera 8 or from another source, and the
corresponding image 198 reduced to the resolution of the electrode
array 14, in its enhanced form. The reduced image resolution can be
changed instantly within the drop down menu list 200.
[0135] Referring to FIG. 7, the camera 8 has preferably a variable
resolution providing an electronic zoom function. Such a feature
can be used to adapt the low resolution of the image transmitted to
the implant 4 (e.g. 25.times.25) to the situation in which the user
is. For example, the user may choose between a coarse view over a
large field of vision or, conversely, a detailed view over a
limited zone in order to discern the details of a point of interest
or for reading purposes.
[0136] Instead of using a predetermined addressing process using
the RAM 64 (see FIG. 8) as hereinabove described, which allows to
reduce the pass-band of the transmitted data when the stimulation
sequence and the pixel numbers are constant for each image, a
specific addressing process can also be implemented to allow the
stimulation sites to be chosen according to each image to be
transmitted. Then, by setting a light intensity threshold under
which the stimulation effect is considered to be negligible,
certain pixels of the image will be simply disregarded by the
external unit 6. As a result, power consumption can be thereby
reduced while the image refresh rate is improved. Preferably, the
threshold is adjustable in order to discriminate the pixels to be
transmitted from those to be discarded. Other suitable addressing
methods can also be implemented.
[0137] The implant system according to the invention can be
equipped for example with an ultrasound sensor (not shown) having a
large field of detection, preferably set as a function of the
minimum zoom of the camera 8 or larger, providing information on
the proximity of detected objects, which information affects the
light intensity transmitted to the brain. Such a system would allow
the user to move smoothly by following the dark or clear zones that
he or she sees, without requiring visual recognition of the
surrounding objects, which may be difficult to achieve at a low
resolution (e.g. 25.times.25).
[0138] While embodiments of this invention have been illustrated in
the accompanying drawings and described above, it will be evident
to those skilled in the art that changes and modifications may be
made therein without departing from the essence of this invention.
All such modifications or variations are believed to be within the
scope of the invention as defined by the claims appended
hereto.
* * * * *