U.S. patent application number 09/817436 was filed with the patent office on 2001-09-20 for implantable device with optical telemetry.
This patent application is currently assigned to Intermedics Inc.. Invention is credited to Bendele, Travis H., Pauly, Robert L..
Application Number | 20010023361 09/817436 |
Document ID | / |
Family ID | 22259525 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010023361 |
Kind Code |
A1 |
Pauly, Robert L. ; et
al. |
September 20, 2001 |
Implantable device with optical telemetry
Abstract
A system is provided for optically communicating with an
implantable device. In one embodiment, the system includes an
implantable device having a large memory and an external unit which
downloads information from the memory for analysis and display. The
implantable device includes a light-emitting diode (LED) and a
modulator for driving the LED. Although various frequencies can be
used, frequencies which experience relatively little attenuation
through body tissue are presently preferred. The external device
includes a photomultiplier tube (PMT) and a demodulator for
equalizing and demodulating the detection signal produced by the
PMT in response to detected light. A high bandwidth channel
(perhaps as much as 500 Mbits/sec) is created by these components.
This channel advantageously allows for a substantially reduced
download time.
Inventors: |
Pauly, Robert L.;
(Friendswood, TX) ; Bendele, Travis H.; (Devine,
TX) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Intermedics Inc.
|
Family ID: |
22259525 |
Appl. No.: |
09/817436 |
Filed: |
March 26, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09817436 |
Mar 26, 2001 |
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09096877 |
Jun 12, 1998 |
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6243608 |
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Current U.S.
Class: |
607/60 |
Current CPC
Class: |
Y10S 128/903 20130101;
A61N 1/37217 20130101 |
Class at
Publication: |
607/60 |
International
Class: |
A61N 001/365 |
Claims
What is claimed is:
1. An implantable device capable of supporting a high-bandwidth
optical communications link with an external device, wherein the
implantable device comprises: a memory configured to store data for
later retrieval; a photo-emitter configured to generate light
having a transmission frequency in a frequency range from
approximately 4.3.times.10.sup.14 to approximately
20.0.times.10.sup.14 Hz; a modulator coupled to receive data from
the memory and configured to convert the data into an electrical
signal for driving the photo-emitter.
2. The implantable device of claim 1, wherein the transmission
frequency is in a frequency range from approximately
4.3.times.10.sup.14 to approximately 7.3.times.10.sup.14Hz.
3. The implantable device of claim 1, wherein the transmission
frequency is in a frequency range from approximately
4.5.times.10.sup.14 to approximately 4.7.times.10.sup.14 Hz.
4. The implantable device of claim 1, further comprising: a
receiver coil configured to generate an induced current in response
to a communication signal from the external programmer; a current
sensor configured to detect the current induced in the receiver
coil and to convert the induced current into a detected signal; a
demodulator coupled to the current sensor to receive the detected
signal and configured to convert the detected signal into an
operational signal for the implantable device; and a microprocessor
coupled to the demodulator and the memory, wherein the
microprocessor receives the operational signal from the
demodulator, wherein the microprocessor collects data for
transmission to the programmer, and wherein the microprocessor
stores the collected data in the memory.
5. The implantable device of claim 4, wherein the microprocessor is
coupled to a stimulus generator which operates in response to a
trigger signal provided by the microprocessor, and wherein the
operational signal is used to determine trigger signal
characteristics.
6. The implantable device of claim 4, further comprising a power
converter coupled to the receiver coil and configured to convert
the induced current into power to be supplied to the modulator.
7. The implantable device of claim 4, further comprising a power
converter coupled to the receiver coil and the modulator to convert
induced current from the receiver coil into electrical power to
operate the photo-emitter.
8. The implantable device of claim 1, further comprising a sensor
configured to sample heart-generated electrical signals and coupled
to the memory to provide the sampled signals for storage.
9. A system for transcutaneous communication, wherein the system
comprises: an implantable device which includes: a memory
configured to store data for later retrieval; a photo-emitter
configured to generate light in response to a modulated signal; a
modulator coupled to receive data from the memory and configured to
convert it into the modulated signal for driving the photo-emitter;
an external unit which includes: a photo-multiplier configured to
detect light emitted by the photo-emitter and configured to
responsively generate a detection signal; a demodulator coupled to
the photo-multiplier to receive the detection signal and configured
to convert the detection signal into a data signal; a display
coupled to the demodulator to receive the data signal and
configured to produce an output display representative of the data
signal.
10. The system of claim 9, wherein the light produced by the
photo-emitter has a frequency in a range from approximately
4.3.times.10.sup.14 to approximately 20.0.times.10.sup.14 Hz.
11. The system of claim 9, wherein the external unit further
includes: an external unit microprocessor configured to generate
data for storage in the memory; an external unit modulator coupled
to receive the data for storage from the external unit
microprocessor and configured to convert the data into a
communication signal; a signaling coil connected proximate to the
photo-multiplier and driven by the communication signal, wherein
the signaling coil is configured to produce a changing magnetic
field.
12. The system of claim 11, wherein the implantable device further
includes: a receiver coil in which a current is induced that is
representative of an induced current representative of the
communication signal; a second demodulator coupled to receive the
communication signal from the receiver coil and configured to
convert the communication signal into the data for storage, wherein
the second demodulator is coupled to store the data in the
memory.
13. The system of claim 12, wherein the implantable device further
includes: a power converter coupled to the receiver coil to convert
the induced current into energy; a capacitor coupled to the power
converter to receive and store the energy, and configured to supply
the energy to the modulator for conversion into the modulated
signal.
14. A method for transcutaneous communication to an external
device, wherein the method comprises: retrieving stored data from a
memory in an implanted device; converting the stored data into a
modulation signal; applying the modulation signal to a
photo-emitter to produce light; positioning a photo-multiplier tube
to detect the light; converting the light into a detection signal;
and demodulating the detection signal to reproduce the stored
data.
15. The method of claim 14, wherein the light produced by the
photo-emitter has a frequency in a range from approximately
4.3.times.10.sup.14 to approximately 20.0.times.10.sup.14 Hz.
16. The method of claim 14, further comprising: generating a
programming signal in the external device; driving a signaling coil
with the programming signal; inducing a current in a receiving coil
in the implanted device; converting the induced current into stored
energy on a capacitor; using the stored energy to produce the
modulation signal.
17. The method of claim 16, further comprising: demodulating the
induced current into program data; storing the program data in the
memory in the implanted device.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates generally to wireless communication
systems for devices implanted in the body, and more particularly to
optical communication between an implanted device and a device
external to the body.
[0003] 2. Description of the Related Art
[0004] Implantable devices have become a standard method of
treating various medical conditions, many of which relate to the
heart. Examples of devices which are routinely implanted include
pacemakers, defibrillators, and nerve stimulators. These devices
and others which have not yet become routine (such as implanted
personal identification chips) are being provided with large
memories for storing vast amounts of data. In the case of medical
devices, this data may include physiological data such as the
electrogram (electrical waveform at the electrodes), instantaneous
heart rate, blood pressure, volume pumped, body temperature, etc.,
and configuration data such as mode of operation, amplifier
sensitivity, filter bandwidth, and error messages. Often the device
stores data that has been collected over a period of hours or days.
This data is periodically retrieved by a doctor to monitor the
patient's condition and to monitor the device's status. In
response, the doctor might re-program the device for a different
mode of operation, sensitivity setting, etc..
[0005] A method is needed to retrieve this data rapidly. The
retrieval needs to be rapid so as to minimize the inconvenience to
the patient who will usually have to remain in the doctor's office
for the data retrieval process. To download four megabytes of
medical device data, for example, at 20 Kbit/s would take nearly a
half-hour--an undesirably long time for both the patient and
medical professional or technician.
[0006] One method for data retrieval is the use of electromagnetic
coupling between a pair of coils. One coil is excited to induce a
current in the other. Modulation of the excitation signal can be
detected in the induced current, and so communication is achieved.
The problem with this is bandwidth. The coils each have a
self-inductance which acts to attenuate high frequency signals, so
that the bandwidth of communications is limited.
[0007] Another method for data retrieval is to provide a direct
electrical connection. A wire connected to the implanted device is
passed directly through the skin and coupled to the external
device. Inherent with this technique is increased discomfort and
increased risk of infection.
[0008] Thus, another method is needed to transfer a large amount of
data quickly from the implanted device to the external device with
minimal discomfort.
SUMMARY OF THE INVENTION
[0009] Accordingly, there is provided herein a system for
communicating between an implantable device and an external device.
In one embodiment, the system includes an implantable device having
a large memory and an external unit which downloads information
from the memory for analysis and display. The implantable device
includes a light-emitting diode (LED) and a modulator for driving
the LED. The LED emits a modulated light signal representing the
data that is stored in memory. One light frequency range which may
be used is 4.3.times.10.sup.14-5.0.times..sup.1- 4 Hz, as body
tissue exhibits good transmission in this range. The external
device includes a photo-multiplier tube (PMT) for detecting and
amplifying the modulated light signal, and a demodulator for
equalizing and demodulating the detection signal produced by the
PMT in response to modulated light.
[0010] These components will support a high bandwidth optical
channel capable of carrying as much as 500 Mbits or more, and
thereby provide for a substantially reduced data retrieval time.
The implantable device may further include a receiver coil which
has currents induced in response to a communication signal from the
external device. A power converter may be coupled to the receiver
coil to convert the induced currents into energy for powering the
LED.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Other objects and advantages of the invention will become
apparent upon reading the following detailed description and upon
reference to the accompanying drawings in which:
[0012] FIG. 1 shows an implantable medical device having optical
telemetry, implanted in an environment within which a
high-bandwidth channel would be desirably employed;
[0013] FIG. 2 is a block diagram of an implantable
pacemaker/defibrillator- ;
[0014] FIG. 3 is a schematic diagram illustrating communications
between an implantable device and an external device;
[0015] FIG. 4 is a block diagram of portions of an external
device;
[0016] FIG. 5 is a block diagram of a telemetry module which
supports an optical communications link;
[0017] FIG. 6 shows an exemplary configuration of the system;
and
[0018] FIG. 7 shows a second exemplary configuration of the
system.
[0019] While the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by
way of examples in the drawings and will herein be described in
detail. It should be understood, however, that the drawings and
detailed description thereto are not intended to limit the
invention to the particular form disclosed, but on the contrary,
the intention is to cover all modifications, equivalents and
alternatives falling within the spirit and scope of the present
invention as defined by the appended claims.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] The following description illustrates the principles of the
invention with respect to an implantable pacemaker ("pacer") and an
external device ("programmer"). The invention, however, is directed
to an improved telemetry link between any implantable device and
any external device configurable to download information from the
implantable device. Thus, the invention applies to implantable
cardioverter/defibrillators (ICD's), nerve stimulators, drug
delivery devices, or any other implantable device configured to
transmit data to an external device.
[0021] Turning now to the figures, FIG. 1 shows a human torso 102
having a heart 104 and an implanted pacer 106. Also shown is a wand
108 which is an extensible portion of an external programmer 110.
Wand 108 is placed on an exterior surface of torso 102 near to the
pacer 106. In the embodiment shown, pacer 106 is a pacemaker
coupled to heart 104 to assist in regulating its operation. In any
case, pacer 106 includes a memory for storing data for later
retrieval. In the case of a pacemaker, the data may represent
measured physiological signals such as cardiac voltages (EKG
signals), blood temperatures, oxygen levels, sugar levels, etc.
[0022] Illustratively, programmer 110 is a programmer/analyzer for
use by a physician. The programmer/analyzer operates to download
information stored in pacer 106 by transmitting signals which place
the pacer in a mode for downloading, and thereafter detecting
signals sent by the device. Then, under control of the physician or
other medical professional, the programmer/analyzer operates to
analyze and display the information in a format which allows the
physician to diagnose any problems. After performing an analysis,
the physician may instruct the programmer/analyzer to adjust
operating parameters of pacer 106. If this is the case, the
programmer/analyzer provides new operating parameters to pacer
106.
[0023] FIG. 2 is a block diagram of an exemplary pacer 106. Pacer
106 has a power supply 202 coupled to a microprocessor 204. Power
supply 202 provides support to all the devices shown in FIG. 2
through connections not shown. Microprocessor 204 is coupled to a
memory 206, a first interval timer 208, and a second interval timer
210 via an I/O (input/output) bus 211. Microprocessor 204 is also
coupled to control an atrium sensor/stimulator 212 and a ventricle
sensor/stimulator 214, each of which may be coupled to the heart by
flexible leads. Finally, microprocessor 204 is coupled to a
telemetry module 218 to communicate with programmer 106.
[0024] Microprocessor 204 preferably is programmable and operates
according to a program stored in a nonvolatile memory. The program
often is parameterized--i.e. one or more of the operations the
microprocessor performs is alterable by setting a parameter. For
example, the microprocessor may be programmed to periodically
trigger atrium stimulator 212. One of the parameters for this
operation might be a value specifying the rate at which the
stimulator is triggered. The parameters may be provided to
microprocessor 204 via telemetry module 218 and stored in memory
206.
[0025] Pacer 106 in FIG. 2 uses first interval timer 208 to
determine the delay between trigger signals applied to atrium
stimulator 212 and ventricle stimulator 214. Further, second
interval timer 210 measures the time since the last heartbeat
sensed by the atrium sensor/stimulator 212 or ventricle
sensor/stimulator 214. When either timer elapses, the elapsed timer
asserts an interrupt to microprocessor 204 to notify microprocessor
204 that the set amount of time has passed. Microprocessor 204
determines the source of the interrupt and takes the appropriate
action. For example, if a maximum time has elapsed since the last
heartbeat, microprocessor 204 might trigger atrium
sensor/stimulator 212.
[0026] Microprocessor 204 preferably also monitors one or more
physiological signals. For example, microprocessor 204 may detect
cardiac voltage signals via atrium sensor 212 and/or ventricle
sensor 214. Blood pressure, body temperature, and adaptive
configuration data may also be monitored. These signals preferably
are logged in memory 206 for later retrieval by programmer 110.
Memory 206 preferably is large enough to store a variety of
physiological signals that are monitored over a period of several
days. This amount of data may comprise several megabytes of data.
Memory 206 preferably is implemented as dynamic random access
memory (DRAM) or other suitable memory type.
[0027] Atrium sensor/stimulator 212 is an interface circuit between
microprocessor 204 and a heart lead coupled to an atrium of the
heart. Similarly, ventricle sensor/stimulator 214 is an interface
circuit between microprocessor 204 and a heart lead that is coupled
to a ventricle of the heart. These interface circuits are
configured to apply a customized electrical energy pulse to the
respective region of the heart in response to a trigger signal from
microprocessor 204. Interface circuits 212, 214 may also be
configured to measure cardiac voltage signals from the electrodes
so that microprocessor 204 can monitor the performance of the
heart. The microprocessor 204 may store the cardiac waveforms (or
"electrograms") in memory for subsequent retrieval by a medical
technician.
[0028] Telemetry module 218 may be designed to be activated by
programmer 110 when wand 108 enters into proximity with pacer 106.
This event causes telemetry module 218 to be activated and to
notify microprocessor 204 of an incoming communication.
Microprocessor 204 monitors the incoming communication from
programmer 110 and stores programming data or parameters, and
responds to any requests. For example, one request might be to
transfer the data from memory 206 to programmer 110. In this case,
microprocessor 204 provides the data from memory 206 to telemetry
module 218 for transferal to programmer 110.
[0029] FIG. 3 is a schematic diagram of the communications channels
employed by pacer 106 and programmer 110. A wand transmitter 302
provides a communication signal which is transmitted to a pacer
receiver 304 through body tissues 306. This communication signal,
for example, might represent a programmer request for the pacer 106
to transmit data. This technique using a pair of coils is well
known to those of ordinary skill in the art. An example of this
technique is illustrated in U.S. Pat. No. 5,314,453, which is
hereby incorporated by reference as though completely set forth
herein.
[0030] To provide a download of a substantial amount of data in as
short a time as possible from pacer 106 to programmer 110, a high
bandwidth connection in the reverse direction (i.e. from the pacer
to the programmer) is desired. This high-bandwidth connection
comprises a pacer transmitter 308 which transmits a modulated light
signal to a wand receiver 310 through body tissues 306. It is
contemplated that wand transmitter 302 and implant receiver 304 are
coils that communicate via a shared inductive coupling. Thus one
embodiment uses an inductive coupling communications link for
programmer 110 to transmit data and commands to pacer 106, and an
optical communications link to transmit data and status information
from pacer 106 to programmer 110. Alternatively, an optical link
could be used to communicate in both directions.
[0031] It is contemplated that implant transmitter 308 includes an
LED that emits light in the infrared (<4.3.times.10.sup.14 Hz),
visible (4.3.times.10.sup.14-7.3.times.10.sup.14 Hz) or ultraviolet
(>7.3.times.10.sup.14 Hz) frequency ranges, and that wand
receiver 310 includes a light sensor sensitive to light emitted by
implant transmitter 308. The various frequencies (colors) of light
experience differing amounts of attenuation by body tissues 306.
The light emitted by implant transmitter 308 preferably experiences
relatively small losses while passing through body tissues 306.
Experiments have been done using a light frequency of
5.42.times.10.sup.14 Hz (green light), but somewhat lower
frequencies such as 4.3.times.10.sup.14-5.0.times.10.sup.14 Hz may
be preferred, and 4.5.times.10.sup.14-4.7.times.10.sup.14 Hz may be
more preferred.
[0032] FIG. 4 is a block diagram of portions of one embodiment of a
programmer 110. Programmer 110 includes a microprocessor 402, a
modulator 404, a transmit coil 406, a light sensor 408, and a
demodulator 410. Microprocessor 402 accepts and responds to user
input (via controls not shown) and initiates communications with
pacer 106. For example, if a user requests a download of data from
pacer 106 to programmer 110, microprocessor 402 formulates a
command signal, and sends the signal to modulator 404. Modulator
404 converts the command signal into a modulated signal for driving
transmit coil 406. The signal driving the transmit coil produces a
changing magnetic field which induces a current in a receive coil
in pacer 106. Pacer 106 processes the induced current in a manner
described further below. Pacer 106 can transmit signals to
programmer 110 by modulating a light signal. The modulated light
signal may be greatly attenuated by body tissues. When enabled,
light sensor 408 detects and amplifies the modulated light signal
to produce a detection signal. Demodulator 410 demodulates the
detection signal and converts it into the data transmitted by the
pacer 106. Demodulator 410 then provides the data to microprocessor
402 for eventual analysis and display.
[0033] Because the optical signal may be greatly attenuated (i.e.
reduced in intensity) by body tissue, light sensor 408 preferably
is highly sensitive and must be protected from ambient light. This
protection may be provided in the form of an enable signal which is
asserted only when the ambient light is blocked, e.g. when the wand
is pressed flat against the torso. In one implementation, the
enable signal may be asserted when a mechanical switch is closed
upon pressing the wand against the torso. In another
implementation, the enable signal may be asserted when a
photo-transistor adjacent to the light sensor 408 detects that the
light intensity has fallen below a predetermined threshold.
[0034] One light sensor which is contemplated for use in wand 108
is a PMT (photo-multiplier tube) such as R5600-01 PMT from
Hamamatsu Corporation. PMT's are well known and widely available,
and are able to detect single photons while maintaining a low noise
level. This light sensor is advantageously sensitive to light in
the frequency range from 4.3.times.10.sup.14 to
20.0.times.10.sup.14 Hz.
[0035] In another embodiment, light sensor 408 comprises a
photo-diode which may be robust enough to withstand ambient light
and sensitive enough to detect attenuated light emissions from the
pacer. This light sensor advantageously does not require an enable
signal and the means for generating the enable signal.
[0036] FIG. 5 shows a block diagram of an illustrative telemetry
module 218 of pacer 106. Telemetry module 218 comprises an implant
receiver coil 502, a current sensor 504, a demodulator 506, a power
converter 508, a modulator 510, and a light source 512. A
communication signal from wand 108 induces a current in coil 502.
Current sensor 504 detects the induced currents and produces an
amplified detection signal representative of the communication
signal sent by wand 108. Demodulator 506 demodulates the
communication signal to obtain the commands, data and/or parameters
being sent by wand 108. Microprocessor 204 processes the
demodulated signal and determines an appropriate response. For
example, if the transmitted data represents a download request,
microprocessor 204 will initiate a download of the requested data
stored in memory 206, i.e. the microprocessor will cause data from
memory 206 to be supplied to modulator 510.
[0037] Referring still to FIG. 5, power converter 508 is coupled to
implant receiver coil 502 to convert the induced currents into
stored energy. As modulator 510 converts the data from
microprocessor 204 into a modulated signal, it uses stored energy
from power converter 508 to drive light source 512 in accordance
with the modulated signal. Light source 512 may be an LED (light
emitting diode) which emits light with a frequency suitable to pass
through the body to the wand. Preferably the LED emits light with a
frequency between 4.3.times.10.sup.14 and 5.0.times.10.sup.14 Hz,
but other frequencies may be used as well. The light emitted is
modulated in accordance with the modulated signal from modulator
510. The modulated light may be detected and demodulated by wand
108 to recover the data stored in memory 206 as described
above.
[0038] In one embodiment, power converter 508 employs a full-wave
rectifier to convert the currents induced in coil 502 into a
unidirectional charging current. The power converter also includes
a bank of switching capacitors to be charged by the unidirectional
charging current and thereafter step up the voltage to charge an
energy storage capacitor. Current sensor 504 may be configured to
detect the induced currents by sensing the voltage drop across one
or more diodes in the full-wave rectifier.
[0039] In another embodiment, the LED is powered by power supply
202 of pacer 106. Power converter 508 may be included for the
purpose of recharging power supply 202.
[0040] Various modulation schemes may be employed for the
communication channels. The wand-to-implant communications channel
may use pulse-width modulation (PWM), frequency-shift keying (FSK),
or other suitable techniques. The implant-to-wand communications
channel may also employ any suitable techniques such as pulse-code
modulation (PCM) and simplex signaling. Both channels may employ
channel coding for error detection, timing, and/or constraining
power usage. Such channel coding techniques are known to those of
ordinary skill in the art. It is noted that light sensor 408 may be
configured to generate a detection signal which is proportional to
the light intensity, and that consequently both digital and analog
amplitude modulation signaling is also supported by the
contemplated configuration.
[0041] FIG. 6 shows an exemplary configuration of wand 108 and
pacer 106 shown in cross-section. Wand 108 is pressed against body
tissues 306 proximate to the location of pacer 106 and in active
communication with pacer 106. Pacer 106 comprises power supply 202,
electronics module 602, implant receiver coil 502, light source
512, and header 604. Electronics module 602 includes microprocessor
204, memory 206, timers 208, 210, sensor/stimulators 212, 214,
current sensor 504, demodulator 506, power converter 508, and
modulator 510. Electronics module 602 and the components it
contains may be constructed as a circuit board. Header 604 is a
transparent portion of pacer 106 which may include electrical
connectors for the heart leads (FIG. 2) and light source 512.
Alternatively, light source 512 may be located in electronics
module 602. As electronics module 602 is normally placed in an
opaque portion of pacer 106, light source 512 is configured to emit
light in the direction of the transparent header 604. A mirror may
be located within header 604 to redirect the modulated light toward
wand 108. This mirror may be concave to reduce dispersion of the
modulated light signal. For either placement of light source 512,
header 604 may also have a portion of its exterior surface
configured as a lens to reduce the dispersion of the modulated
light signal. Some of these configurations are described in U.S.
Pat. No. 5,556,421, which is hereby incorporated by reference in
its entirety.
[0042] Wand 108 illustratively comprises modulator 404, transmit
coil 406, light sensor 408, demodulator 410, ambient light detector
606, reflective surface 608, interface module 610, and user
interface 612. In one embodiment, light sensor 408 is placed near a
convergence point of light rays that reflect from reflective
surface 608. Reflective surface 608 is designed to increase the
light-gathering ability of wand 108. Ambient light detector 606 is
positioned within the concavity defined by reflective surface 608
and/or adjacent to light sensor 408. Ambient light detector 606
provides the enable signal discussed in FIG. 4 when a sensitive
light sensor 408 is employed. Ambient light detector 606 may be a
photo-transistor or photo-diode or any other photo-sensitive device
robust enough to withstand anticipated light levels when wand 108
is separated from torso 102. Interface module 610 may be a line
driver/buffer for communications with the rest of programmer 110,
and may further comprise a power supply or converter for powering
the electronics of wand 108. User interface 612 may comprise
buttons for user input (e.g. begin download) and lights for user
feedback regarding the status of the communications link with the
implanted device. Directional lights may also be provided to aid
the user in positioning the wand to achieve the highest
communications signal-to-noise ratio and the maximum communications
rate for downloading information from the memory of the pacer.
[0043] FIG. 7 shows a second exemplary configuration of wand 108,
in which mechanical switches 702 rather than ambient light detector
606 are used to provide the enable signal of FIG. 4. Mechanical
switches 702 are pressure sensitive and positioned on the face of
the wand so that when the wand is correctly pressed against the
torso, the normally open switches are all closed. Variations on
this may be employed so long as the enable signal is only asserted
when the light sensor 408 is shielded from excessive light levels.
Numerous variations and modifications will become apparent to those
skilled in the art once the above disclosure is fully appreciated.
It is intended that the following claims be interpreted to embrace
all such variations and modifications.
* * * * *