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Claims  |
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I claim:
1. A system for measuring a distance to at least one object in a
predetermined non-liquid filled space comprising:
(a) a plurality of ultrasonic transducers, each said transducer being
adapted to transmit and receive ultrasonic pulses;
(b) beam shaping means associated with each said transducer for shaping the
beamwidth of each said transducer in a predetermined manner enabling both
widening and narrowing of said beamwidth;
(c) control means for controlling said system connected to said transducers
via integrated circuit means for directly controlling transmission of
pulses from said transducers and for conveying signals related to echoes
received by said transducers to said control means;
(d) said control means and integrated circuit means being preprogrammed to
effect time gain control of said transducers to increase gain as a
function of time; and
(e) said control means being programmed to (1) measure the time from
transmission of pulses by said transducers to the time from transmission
of pulses by said transducers to receiving of pulses reflected from said
object, and (2) therefrom to calculate the distance between the object and
said transducers.
2. The invention of claim 1, wherein said beam shaping means comprises a
plate with a hard surface for each transducer with a slot formed therein,
each said plate being installed in front of a respective transducer where
sound pressure is in a null so as to shape said beamwidth.
3. The invention of claim 2, wherein said plate includes a separate layer
made of a sound absorbing material or is padded on the inside facing the
transducer with a sound absorbing material so as to attenuate the standing
sound waves caused by the beam shaping slot.
4. The invention of claim 1, wherein each said transducer includes a foil
layer including conductive and nonconductive regions, said conductive
region comprising said beam shaping means and being formed in the shape of
a slot.
5. The invention of said claim 1, wherein each said transducer includes a
grooved metallic backplate including grooved and nongrooved regions, said
grooved region comprising said beam shaping means and being formed in the
shape of a slot.
6. The invention of any one of claims 2, 3, 4 or 5, wherein said slot is
formed vertically.
7. The invention of any one of claims 2, 3, 4 or 5, wherein said slot is
formed horizontally.
8. The invention of any one of claims 2, 3, 4 or 5, wherein said slot is
elliptical.
9. The invention of claim 1, wherein said control means comprises a
computer.
10. The invention of claim 1, wherein said control means comprises a
microcomputer.
11. The invention of claim 1, wherein said circuit means include a circuit
controllable by said control means for enabling said circuitry to transmit
a predetermined number of pulses controlled by software.
12. The invention of claim 1, wherein said integrated circuit means
includes a sub-circuit means controllable by said control means for
transmitting said pulses at predetermined frequencies controlled by
software.
13. The invention of claim 1, wherein said integrated circuit means
includes a sub-circuit means for enabling said time gain control, said
sub-circuit means including a plurality of on-off switches, each said
switch corresponding to a predetermined gain level, said switches being
controlled by said control means to set a desired gain level for said
pulses.
14. The invention of claim 1, wherein said integrated circuit means
includes a sub-circuit means including a preamplifier means for enabling
additional gain by adjustment of said preamplifier, in order to select a
first gain step to be higher than a previously selected gain.
15. The invention of claim 1, wherein said integrated circuit means
includes a sub-circuit means controllable by said control means for
blanking said transducers for a predetermined blanking time, starting
immediately before a transmission and ending at a further predetermined
time, when ringing of the transducers is below a predetermined level, said
blanking time being programmed into associated software and determining a
minimum detectable distance of said object.
16. The invention of claim 1, wherein said integrated circuit means
includes a sub-circuit means for increasing the resistance in series with
a resonant receiver circuit in order to attenuate ringing of the
transducer and noise picked up by the transducer.
17. The invention of claim 1, wherein said integrated circuit means
includes a sub-circuit means controllable by said control means for
closing a switch on a primary side of a transformer in a transmitter
circuit of said control means and thereby switching a large resistor into
series with a resonant receiver circuitry in order to quickly attenuate
ringing of at least one of said transducers, said switching being
accomplished through software programming.
18. The invention of any one of claims 1, 2, 3, 4, 5, 10, 11, 12, 13, 14 or
15 wherein said plurality of transducers comprises four transducers.
19. The invention of claim 18, wherein said transducers are mounted in a
housing with each transducer facing perpendicularly with respect to two
adjacent transducers, said beam shaping means being arranged so that said
transducers combine to form an omnidirectional distance measurement
system.
20. The invention of claim 19, wherein said at least one object comprises
up to four objects, the speed and range of which may be measured by said
system.
21. The invention of anyone of claim 1, 2, 3 or 4 wherein at least one of
said transducers is placed in a grounded metallic enclosure so as to be
able to use said at least one transducer within a magnetic field, an
electrical field or an electromagnetic field and in order for said
transducer to pick up less noise.
22. The invention of claim 1 wherein said time gain control is used to
dynamically widen or narrow the effective beam of a single transducer in
both the horizontal and the vertical directions by programming of
associated software.
23. The invention of claim 1, wherein ringing of the transducer is measured
initially and stored in a memory of said control means, and is thereafter
subtracted from a measured transducer signal when the system is operated.
24. A system for locating at least one object in a predetermined space
comprising:
(a) a plurality of ultrasonic transducers, each said transducer being
adapted to transmit and receive ultrasonic pulses;
(b) beam shaping means associated with each said transducer for shaping the
beamwidth of each said transducer in a predetermined manner enabling both
widening and narrowing of said beamwidth;
(c) control means for controlling said system connected to said transducers
via integrated circuit means for directly controlling transmission of
pulses from said transducers and for conveying signals related to echoes
received by said transducers to said control means;
(d) said control means and integrated circuit means being programmed to
effect time gain control of said transducers; and
(e) each said transducer including a grooved metallic backplate including
grooved and non-grooved regions, said grooved region comprising said beam
shaping means and being formed in a shape of a slot, at least one of said
transducers being placed in a grounded metallic enclosure so as to be able
to use said at least one transducer within a magnetic field, an electrical
field or an electromagnetic field and in order for said transducer to pick
less noise.
25. A system for locating at least one object in a predetermined space
comprising:
(a) a plurality of ultrasonic transducers, each said transducer being
adapted to transmit and receive ultrasonic pulses;
(b) beam shaping means associated with each said transducer for shaping the
beamwidth of a beam of each said transducer in a predetermined manner;
(c) control means for controlling said system connected to said transducers
via integrated circuit means for directly controlling transmission of
pulses from said transducers and for conveying signals related to echoes
received by said transducers to said control means, said integrated
circuit means including a sub-circuit means for enabling time gain
control, said sub-circuit means including a plurality of on-off switches,
each said switch corresponding to a predetermined gain level, said
switches being controlled by said control means to set a desired gain
level for said pulses, said time gain control sub-circuit means being used
to dynamically widen or narrow each said beam in both the horizontal and
the vertical directions.
26. A system for measuring a distance to at least one object in a
redetermined non-liquid filled space comprising:
(a) a plurality of ultrasonic transducers, each said transducer being
adapted to transmit and receive ultrasonic pulses;
(b) beam shaping means associated with each said transducer for shaping the
beamwidth of each said transducer in a predetermined manner;
(c) control means for controlling said system connected to said transducers
via integrated circuit means for directly controlling transmission of
pulses from said transducers and for conveying signals related to echoes
received by said transducers to said control means;
(d) said control means and integrated circuit means being preprogrammed to
effect time gain control of said transducers to increase gain as a
function of time and to dynamically widen or narrow the effective beam of
a single transducer in both the horizontal and vertical directions by
programming of associated software; and
(e) said control means being programmed to (1) measure the time from
transmission of pulses by said transducers to the time for transmission of
pulses by said transducers to receiving of pulses reflected from said
object and (2) therefrom to calculate the distance between the object and
said transducers. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
In the prior art, many distance measurement systems exist, however, to the
knowledge of Applicant, none of the existing systems have the flexibility
of beamwidth shaping, ease of control, flexibility of reprogramming, low
cost and minimization of components as are the case with the present
invention.
In prior art systems known to Applicant, the ultrasonic transducers thereof
are characterized by fixed beamwidth in both the horizontal and vertical
planes which renders these systems inflexible for the many uses
contemplated for the present invention. In another deficiency in the prior
art, most distance measuring systems utilize a first transducer for
transmitting and a second transducer for receiving. With such systems, it
is quite possible that confusion will exist especially when the receiving
transducer may be receiving signals which are not related to those which
have previously been transmitted by the transmitting transducer. The
following prior art references which are believed to be only generally
related to the teachings of the present invention are known to Applicant:
Cudworth U.S. Pat. No. 3,226,673 discloses a device for indicating objects
rearwardly of a vehicle which device includes a plurality of signal
emitting transducers which may be mounted in transversely spaced
relationship on the rear bumper of a vehicle. When an object is within a
predetermined short distance of the rear of the vehicle an indication is
given to the driver of the vehicle through the energization of an
emergency or danger signalling circuit so that the driver knows that the
vehicle is dangerously close to the object. This system utilizes separate
transducers for the transmitting and receiving functions. This system is
different from the present invention for several reasons. Firstly, the
Cudworth system uses separate transmitting and receiving transducers
whereas in the present invention, each transducer performs both
transmitting and receiving functions sequentially. Thus, through the use
of the present invention, more transmitter-receiver transducers may be
placed in a given area. Furthermore, the Cudworth system uses no beam
shaping techniques nor does it utilize time dependent gain control nor
does it use microprocessor control and processing whereas the present
invention includes each of these features.
Sato , et al. U.S. Pat. No. 3,778,823 discloses a system which senses an
imminent collision so as to activate control means to blow up an air bag
in a vehicle. The system operates through the use of microwaves and has
separate transmitter and receiver antennas. The system measures both the
position of an object and the speed by which the vehicle is approaching
the object by the well known Doppler technique. The present invention is
distinct from the teachings of Sato, et al. as utilizing ultrasound waves
rather than microwaves, as using transducers which perform both the
transmitting and receiving functions rather than separate transmitting and
receiving transducers, and as utilizing beam-shaping techniques,
time-dependent gain-control and microprocessor circuitry for control and
processing, none of which are taught or suggested in Sato, et al.
Inoue U.S. Pat. No. 4,104,610 discloses an ultrasonic horn having a
particularly shaped opening for beam shaping purposes. This device is
different from the generally corresponding device in Applicant's system
since Inoue discloses a horn whereas the present invention utilizes a slot
which is significantly different therefrom. In one aspect, a horn in
general cannot achieve as wide a beamwidth as can a slot and further, when
size considerations are important, a transducer using a slot may be made
much smaller than one which uses a horn.
Galvin, et al. U.S. Pat. No. 4,155,066 discloses an intrusion alarm system
utilizing separate transmitting and receiving transducers having
sensitivities which are reduced along the normal or boresight axis thereof
and which are increased along axes angularly displaced from the boresight
axis. This results in an energy pattern of reduced intensity along the
boresight axis thereby reducing the intensity of standing waves which may
occur thereat. This system is materially different from the present
invention for many of the reasons set forth above and further because the
Galvin, et al. device utilizes a cavity design to achieve a particular
beam pattern whereas the present invention uses a slot to achieve a flat
bell curve beam pattern.
Morgera U.S. Pat. No. 4,207,620 discloses an underwater mapping system
utilizing a plurality of transducers which enable the measurement of a
swath of terrain much wider than the beamwidth of the sonar pulses. This
system is significantly different from the system of the present invention
as failing to utilize beam shaping through the use of a slot and as
failing to use a microprocessor for control and processing. The invention
of Morgera only utilizes a microprocessor for beam steering and display
purposes.
Duncan, et al. U.S. Pat. No. 4,240,152 discloses a device utilizing at
least three transducers comprised of two transmitters and one receiver or
one transmitter and two receivers which system may utilize a triangulation
technique in order to find the location of an object. Of course, the
present invention is different from the system as utilizing transducers
which perform both the transmitting and receiving function. Furthermore,
the present invention only measures the distance to the object whereas the
system of Duncan, et al. utilizes a triangulation technique in order to
find the location of the object, which is a complication for the purposes
of the present invention. Further, other differences discussed above with
regard to the other known prior art references also apply here.
Tournois U.S. Pat. No. 4,456,982 discloses a bidimensional imaging system
which utilizes a transmitting array and a receiving array which system
utilizes transmitted and received echoes. This system is believed to be
related to Morgera, discussed above, and is discussed from the teachings
of the present invention for the same reasons discussed with regard to
Morgera.
Gelhard U.S. Pat. No. 4,500,977 discloses a motor vehicle mounted distance
measuring device utilizing four different transducers and ultrasonic echo
signals. Several differences exist between the teachings of Gelhard and
those of the present invention. Firstly, Gelhard discloses a large number
of different types of transducers which are used in his system whereas in
the present invention, only a single transducer having the beam thereof
shaped by a simple slot and controlled by the use of a time-gain scheme is
used. Further, Gelhard teaches the use of a horn to narrow the beam in
both directions whereas the present invention utilizes a slot. Thus,
Gelhard is different from the present invention in the same manner as
Inoue discussed above in this regard. Furthermore, the present invention
utilizes the concepts of dynamic beam shaping, time-dependent gain-control
and microprocessor control and processing none of which are taught or
suggested by Gelhard.
Furthermore, Applicant is aware of U.S. Pat. Nos. 3,522,764; 3,523,275;
4,081,626; 4,085,297 and 4,199,246. Each of these patents discloses a
transducer design per se and possibly the use of a particular transducer
design in an application such as for a camera range finder. In the present
invention, designs of transducers similar to those disclosed in some of
these patents are utilized as a starting point and are extensively
modified through the use of the slot device as set forth hereinabove for
beam shaping purposes and thus, these references are believed to be of
only general interest vis-a-vis the present invention.
The publication "A Prosthetic Aid for A Developing Blind Child" by Boys, et
al. published in Ultrasonics Magazine, Jan., 1979, is believed to be only
generally relevant to the teachings of the present invention as suggesting
the concept of "blanking" during the measuring sequence. Otherwise, this
publication is believed to be of only general interest concerning the
teachings of the present invention.
Accordingly, a need has developed for an omnidirectional distance
measurement system having the flexibility of beamwidth shaping, ease of
control, flexibility of reprogramming low cost and a minimum of
components. With these criteria in mind, the present invention was
developed.
SUMMARY OF THE INVENTION
The present invention overcomes the deficiencies of prior art devices as
discussed hereinabove and provides an omnidirectional distance measuring
system fulfilling each and every one of the prerequisites set forth above
as to flexibility of beamwidth shaping, ease of control, flexibility of
reprogramming, low cost and component limitations. The present invention
includes the following combination of integrated elements:
(a) In a first aspect of the present invention, in the preferred embodiment
thereof, four ultrasonic transducers are provided. The beamwidth of each
transducer is shaped using a specially designed slot. In one embodiment,
the slot is formed by a separate device placed over the transducer. In
another embodiment, the slot is formed in the conductive foil of the
transducer itself. In yet another embodiment the slot is formed in the
grooved metallic back-plate of the transducer itself. In the two latter
mentioned embodiments, modification of the transducer is necessary.
(b) In a further aspect of the present invention, it is preferred that each
of the transducers both transmits and receives ultrasonic waves. In this
way, through the use of only four transducers, the present invention is
able to detect the distance, direction and speed of four objects with
respect to their respective transducers in the work area substantially
simultaneously.
(c) In a further aspect of the present invention, the size of the work area
is determined in the software which is created so as to control the
operation of microprocessor controlling means for the system. In this
regard, the system may be devised as desired to have an integral
microprocessor capability or if desired, may be designed so as to
interface with a separate microprocessor or computer.
(d) In the preferred embodiment, each of the four transducers uses an
analog board to enable it to transmit and receive ultrasonic waves.
Transformer circuitry associated with the transducer is pulsed so as to
provide the high voltage necessary to transmit ultrasonic waves. A bias
voltage is kept on the transducer after transmission enabling the
transducer to be used as a microphone in order to receive ultrasonic
waves. In a further aspect, the circuitry incorporates a blanking circuit
so that each transducer's receiver is cleared immediately prior to the
emission of ultrasonic waves and held clear until a predetermined time
after the emission so as to avoid receiving false signals caused by
transducer ringing. The transformer circuitry is shortened on the
secondary side immediately after the transmission of sufficient pulses has
taken place. This causes a large impedance on the primary side of the
transformer circuitry and therefore in series with the resonant receiving
circuitry, which dampens the ringing of the transducer faster. The
transformer circuitry is shortened until receiver is stopped being cleared
(blanked).
(e) In an important aspect of the present invention, "time gain" control is
provided by the computer or microprocessor to control the signals received
by the transducers. In this regard, the receiver for each transducer is in
a low gain setting to start with, and the gain is increased in steps as
time elapses in order to compensate for the attenuation of ultrasound in
air as a function of the distance. Thus, any one transducer in accordance
with the present invention will initially receive in a low gain setting
and then the gain is increased over time until such time as an echo
indicating the presence of an object is received.
(f) The present invention, in the preferred embodiment, is devised so that
all four transducers operate through a common microprocessor control
device. Thus, when, for example, four transducers are utilized, ultrasonic
waves from the transducers are transmitted sequentially and with
sufficient spacing between the transmission and receiving until the
ringing of the transducer is lower than a predetermined level, through the
use of a blanking circuit so that the microprocessor can receive and
interpret the appropriate reflected signals from the objects which are
being tracked by the transducers. The time elapsed between transmission
and receiving the return signal (echo) is proportional to the distance
travelled by the ultrasound. Since the speed of sound is known, the
distance can be calculated.
(g) In a further aspect of the present invention, the system embodied in
the present invention may be utilized in many diverse applications such as
those of collision avoidance for vehicles, distance measuring on robots,
intrusion detecting security devices, detection systems for the disabled
such as the blind, and speed and position detection.
Accordingly, it is a first object of the present invention to provide an
omnidirectional distance measurement system.
It is a further object of the present invention to provide such an
omnidirectional distance measurement system which in the preferred
embodiment may measure the distance and location of an object with respect
to a fixed transducer and the speed of an object in a defined work space.
It is a further object of the present invention to provide such a system
wherein the number of objects which may be measured corresponds to the
number of transducers utilized in the system.
It is a still further object of the present invention to provide such a
system wherein each transducer provides both the transmitting and
receiving functions.
It is a still further object of the present invention to provide such a
system wherein beam shaping is utilized as a modification of known
transducers so as to accurately define the space within which measurements
are to be taken.
It is a yet further object of the present invention to provide such a
system which may incorporate integrally its own microprocessor or computer
or may be designed so as to interface with a separate microprocessor or
computer as desired.
It is a still further object of the present invention to provide such a
system wherein the associated microprocessor or computer is programmed to
control emission of ultrasonic waves from the respective transducers and
the gains of the negative receivers, which are variable with time, for the
specific purposes set forth hereinafter
These and other objects, aspects, and features of the present invention
will be better understood from the following detailed description of the
preferred embodiments when read in conjunction with the appended drawing
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of a preferred embodiment of the present
invention.
FIG. 2 shows a first embodiment of the circuitry from the block diagram of
FIG. 1, omitting the microprocessor or computer circuitry for detail.
FIG. 3 shows a further embodiment of the circuitry of the embodiment of
FIG. 1 including a single-chip microcomputer.
FIG. 4 shows an exploded perspective view of an ultrasonic transducer
modified with the provision of a beam shaping slot. The slot is narrowing
the beamwidth in the vertical direction and is widening the beamwidth in
the horizontal direction.
FIG. 5 shows an exploded perspective view of an ultrasonic transducer
modified with a beam shaping slot. The slot makes the beamwidth wider in
both the horizontal and the vertical direction.
FIG. 6 shows an exploded perspective view of a further embodiment of
transducer wherein the beam shaping slot is formed in the conductive foil
thereof.
FIG. 7 shows an exploded perspective view of a further embodiment of an
ultrasonic transducer wherein the beam shaping slot is formed in the
grooved metallic back-plate thereof.
FIG. 8 shows a perspective view illustrating the employment of four
transducers in the inventive system.
FIG. 9 shows a flow chart of the present invention including the use of
four transducers.
FIG. 10 shows the effective beamwidth of the system for various initial
gain settings.
FIG. 11 shows the circuitry for measuring the ringing of the transducer
initially and storing the measurement in the computer memory.
FIG. 12 shows the circuitry for subtracting the stored information of the
transducer ringing from the measured transducer signal in order to
compensate for the transducer ringing.
SPECIFIC DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference now to FIG. 1, a block diagram of a preferred embodiment of
the present invention in the form of the system designated by reference
numeral 1 is seen. As shown, a plurality of transducers 3 are provided
which in the preferred embodiment are four in number and are designated in
FIG. 1 with reference numerals 3a, 3b, 3c and 3d. Connected to each
transducer 3 is a circuit 5 which interfaces the transducers 3 with the
control means 20 which may be a microprocessor or a single-chip
microcomputer. As should be understood, the control means 20 controls the
transducers 3 via the circuit 5 so as to control the transmission of
ultrasonic waves, the number of pulses, the frequencies of the different
pulses, the blanking of the circuits, the attenuation of the ringing of
the transducer and the receipt of reflected echos which provide
information to the control means 20 so as to enable it to calculate range,
location and speed of objects which are being tracked by the system 1.
With reference now to FIG. 2, an electrical circuit is shown which
comprises a first embodiment of a circuit corresponding to those which are
referred to by the reference numeral 5 in FIG. 1. The circuit 5 includes a
chip 6 which may, if desired, be a U1 ranging receiver such as that
manufactured by Texas Instruments for use by the Polaroid Company. The
circuit 5 includes a plurality of ports numbered 7, 8, 9, 10, 11, 12, 13
and 14.
As shown in FIG. 2, the port 7 controls the transmission of ultrasonic
pulses by the transducers 3, including the number of pulses and the
frequencies of the different pulses. This is set in the software in the
microprocessor or the single-chip microcomputer. The port 8 communicates
to the control means echos which have been received by the transducers 3
in response to the transmitted ultrasonic pulses. The port 9 conveys
signals from the control means to the circuit 5 which signals cause the
circuit 5 to be blanked immediately before the transmission and until the
ringing of the transducer is below a predetermined level so as to prevent
the receipt of false signals from the transducer ringing caused by the
transmission.
The ports 10, 11 and 12 are binary ports which are utilized to control the
gain of the particular pulses which are transmitted by the transducers 3.
These ports are binary in that the port 10 corresponds to 2.sup.0, the
port 11 corresponds to 2.sup.1 and the port 12 corresponds to 2.sup.2 such
that gain increment levels of from 0 to 7 may be provided through the
various combinations of the ports 10, 11 and 12 being activated. For
example, if the ports 10 and 12 are activated, the gain level would
correspond to the number 5 out of 7 levels. If all three ports 10, 11 and
12 are activated, gain level 7 would be attained. In a still further
example, if ports 10 and 11 are activated, gain level 3 would be attained.
Port 12 also includes a flip-flop, which is triggered by a negative going
pulse, so when gain step 7 has been set and ports 10, 11 and 12 are
switched to zero, the gain is set to step eight. The method described
above will then set the gain steps from 8 to 15. It is possible to set
gain step zero next time the ports 10, 11 and 12 are switched to zero. In
this way, the control means through the selective activation of the ports
10, 11 and 12 controls the level of the gain of the ultrasonic pulses
transmitted by the transducers 3. In the embodiment of FIG. 2, 3 gain
level ports 10, 11 and 12 are shown. Of course, the more gain ports there
are, the more incremental levels of gain control are available.
Also shown in FIG. 2 are two ports 13 and 14 each of which connects the
circuit 5 with a transducer 3. As should further be understood, the ports
7, 8, 9, 10, 11 and 12 are connected to a control means such as the
control means 20 schematically depicted in FIG. 1.
Reference is now made to FIG. 3 wherein a further embodiment of the circuit
5 is shown and designated by reference numeral 105. The circuit 105 is
similar to the circuit 5 but differs as including integrally formed
therewith a control means 120 corresponding to the control means 20 in
FIG. 1 which control means 120 may, if desired, be a microprocessor or
computer but in the example shown in FIG. 3 comprises a Rockwell R6500
microcomputer. This is to be considered merely exemplary as any computer
corresponding in functions to this microcomputer may be utilized in the
circuit 105. Furthermore, FIG. 3 merely shows a circuit representative of
the circuits which may be employed in the present invention since the FIG.
3 circuit only shows circuitry for use with two transducers 103. As should
be understood by those skilled in the art, the circuit 105 may be
augmented through the use of additional ports in the control means 120 so
as to include as many transducers 103 as are necessary. As shown, the
control means 120 includes the ports 107 which control the transmission of
ultrasonic pulses by the transducers 103, the ports 108 which control the
receipt of echoes created by the reflection of the transmitted pulses of
the objects which are being tracked by the system. It is possible to set
the number of pulses for transmission and the frequencies of the different
pulses in the software of the single-chip microcomputer 120 in a manner
well known to those skilled in the art. Further, the control means 120
includes the blanking ports 109 which control the conveyance of signals
from the control means 120 which signals cause receiver 130 of the circuit
105 to be blanked a predetermined time starting immediately before the
transmission and ending when the ringing of the transducer 103 is less
than a predetermined level. Further, the control means 120 includes
switching ports 193 which control the switching of a shortening 192 of the
secondary side of the transformer 194, which will cause a large resistor
on the primary side of the transformer 194 to be placed in series with the
resonant receiver circuit in order to attenuate the ringing of the
transducer. The resistor is switched in immediately after the transmission
and switched out when the blanking of the receiver 130 is stopped.
Further, the circuitry 105 includes a variable resistor 190 and a variable
resistor 191. The ratio of resistor 191 to resistor 190 determines the
gain of the preamplifier in circuit 103. The value of resistor 190
determines the attenuation of the received signal (echo), the ringing of
the transducer and the noise picked up by the transducer. Further, the
control means 120 includes ports 110, 111, 112 and 113 which correspond to
the ports 10, 11, and 12 in FIG. 2. The provision of four ports provides
gain levels in increments from 0 to 15 depending upon which of the ports
are activated by the control means 120, without the use of an internal
flip-flop. The gain steps as a function of time can be set in the software
in the single-chip microcomputer 120. Only a number of the available gain
steps are needed in most applications.
For each transducer 103, a chip 130 is provided which in some respects is
analogous to the chip 6 illustrated in FIG. 2. In the circuit embodiment
shown in FIG. 3, the chip 130 is preferably a Texas Instrument TL852
integrated circuit. The chip 130 has slightly more flexibility than the
chip 6 which is exemplified by, for example, the provision of four gain
level ports rather than the three gain level ports available with the chip
6 shown in FIG. 2. As further shown in FIG. 3, the control means 120
includes range output ports commonly designated with the reference numeral
117 which provide any one of an audible or visual display or indication of
the signals which have been received by the control means 120 responsive
to the transmission of ultrasonic pulses by the transducers 103. The port
119 provides connection to a further audible feedback device 121 which
may, for example, comprise a buzzer. The rest of the circuit should be
understood by those skilled in the art.
Reference is now made to FIGS. 4, 5, 6 and 7 wherein four examples of
transducers usable with the present invention are shown. In FIG. 4, a
transducer assembly 203 is seen to include a transducer 205 and a beam
shaping device 207 having a slot therein designated by the reference
numeral 209. It further has a metallic encapsule, 201, which is grounded
in order to lower the noise picked up by the transducer 205. The slot 209
will narrow the beam in the vertical direction and widen the beam in the
horizontal direction. The beamwidth of the modified transducer can be
estimated by using the equation for a rectangular piston:
##EQU1##
Where P(.theta.)=the sound pressure as a function of the off-axis angle
.theta.=off-axis angle
P.sub.o =constant pressure
d=width of slot
.lambda.=wavelength of ultrasound
It is possible, from this equation, to find the on-axis sound pressure as a
function of the slot width. It is also possible to find the 3 dB beamwidth
in degrees as a function of the slot width.
In FIG. 5, a transducer assembly 203' is seen to include a transducer 205,
a beam shaping device 207' having a slot therein designated to the
reference numeral 203'. It further has a metallic encapsule, 201, which is
grounded, in order to lower the noise picked up by the transducer. The
slot 209' is of circular shape and will widen the beam in both the
horizontal and the vertical directions. The beamwidth of the modified
transducer can be estimated by using the equation for a circular piston:
##EQU2##
.lambda.=wavelength of the ultrasound P(.theta.)=the sound pressure as a
function of the off-axis angle
P.sub.o =constant sound pressure
a=radius of the circular piston
J.sub.1 =the bessel function of first order
It is possible, from the equation, to find the on-axis sound pressure as a
function of the slot radius. It is further possible to find the 3dB
beamwidth as a function of the slot radius. It is of course, also possible
to find the on-axis sound pressure and the 3dB beamwidth of the transducer
205, without a slot modification. It is possible to estimate the on-axis
sound pressure and the 3dB beamwidth from an elliptical slot modification,
by either looking at an elliptical piston or a combination of the two
equations above.
The slot device 207 and 207' in FIGS. 4 and 5 is made by a sound absorbing
material or it is padded on the inside with a sound absorbing material in
order to attenuate the standing waves caused by the beam shaping slot
device, which will cause more ringing of the transducer 205.
With reference now to FIG. 6, a transducer assembly 203" is seen to include
a beam shaping slot 209" integrally formed in the conductive foil member
208 of the transducer. As is well known in the art, the transducer
assembly 203' further includes an inner ring 211, a retainer 213, a groove
plate 215 and a housing cover 217. The beamwidth and the on-axis sound
pressure of this slot modification can be estimated by using the equations
above.
With reference now to FIG. 7, a transducer assembly 203"' is seen to
include a beam shaping slot 209"' integrally formed in the
grooved-metallic back-plate 215 of the transducer. The beamwidth and the
on-axis sound pressure of this slot modification can be estimated by the
use of the equations above.
FIG. 8 shows an arrangement of four transducers designated by reference
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