Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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AUTOMATIC BIOMETRIC DATA SYSTEM
TECHNICAL FIELD
The present invention relates to an apparatus
and method for calculating height and weight of human
subjects using an electronic scale and a sonar head and
taking into account sound wave noise created in the
measurement area. The apparatus and method are also
capable of calculating the body surface area and
percentile for the age of the subject.
The automated system and method of the present
invention measures the weight and height of human
subjects, children and adults. This system makes use
of sonic waves to calculate the height of the subject,
and it may also calculates automatically the body
surface area. The results are given in absolute
figures (height, weight, surface area) and in terms of
the percentile for a normal population of the same age
and sex. The results are printed on stickers which can
be easily pasted in the subject's file, and the data
are also accumulated by the computer to be loaded later
in an institution's main frame computer.
Height and weight measurement of individuals are
an important part of clinical evaluation, both in
public and private clinics. Most corporations will
also request, before hiring an employee, a complete
physical examination that include those measurements.
These measurements may take a certain time, and errors
can happen when obtaining the data or during
transcription of the results on the subject's chart.
In addition, in medicine, many normal parameters are
now indexed to the body surface area which is derived
from height and weight by using a chart. This is,
again, time consuming and involves errors in
calculation and transcription. In pediatrics, it is
also customary to plot the patient's height and weight
on percentile curves for normal subjects. This
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involves, of course, plotting these parameters on graph
and transcribing the results in the patient's file.
BACKGROUND ART
Height and weight have been routinely measured
in patients at least since the beginning of this
century. Weight measurements at the beginning made use
of classical scales with counterweight, and later
equipment has been more sophisticated involving tension
10 gauges with digital output, and the weight is usually
displayed on a screen using light emitting diodes.
However, measurements of height has not progressed in
the same fashion and it is still done in a rather
primitive fashion comparing the patient's height to a
15 ruler graduated either in inches or centimeters,
although a few developments have been disclosed in
patent literature. In babies, a tape measure is used.
A typical example of a patented apparatus for
automatically measuring height is described in U.S.
20 Patent No. 4,518,052 where a digital read-out is
provided. In one of its aspects, the height and weight
measuring machine uses infrared rays that are impinged
upon a subject's head at a slanting angle whereby some
rays are reflected horizontally to pass through a
25 transparent glass graduated scale in the front of the
body. Sensors detect this reflected ray and a
measurement of height is obtained, but there is still
mechanical manipulation. The weight is provided by a
scale on which the person stands. It is also important
30 that the patient assumes a very precise position with
respect to a sliding plate disposed in a vertical
frame.
Reference is also made to Japanese Specification
5828609 of Matsushita Denki K.K. which describes a
35 system to measure height by transmitting ultrasonic
waves to the head part of the human subject, capting
??? the signals of the reflector wave lower than a
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certain level and measuring the time during which the
reflected wave arrives. The circuit measures the time
during which the ultrasonic wave propagates back and
forth between an emitter and the floor surface on which
the subject is standing as well as the head of the
subject. One problem with using ultrasonic pulses is
that these pulses will bounce off the hair of the
patient and provide false signals. There are also
false signals provided by environmental objects, and
these also result in errors. Accordingly, precise
calculations of height are difficult to obtain from the
method and apparatus described. Another disadvantage
of prior art apparatus is that they are time consuming
to use and provide automatic output information on only
one parameter of a subject.
SUMMARY OF INVENTION
It is therefore a feature of the present
invention to provide an automatic apparatus and method
for measuring and calculating the height and weight of
human subjects which substantially overcome all of the
above-mentioned disadvantages of the prior art.
Another feature of the present invention is to
provide an automatic measuring apparatus and method for
calculating height and weight of human subjects wherein
these measurements can be obtained quickly with
increased precision and without transcription errors,
and further wherein the data can be accumulated in a
computer to be unloaded in a patient's computer chart
or other computer systems.
Another feature of the present invention is to
provide an automtic measuring apparatus and method for
calculating the height and weight of human subjects
wherein the height is calculated using sound waves
which are calibrated at ambient temperature, and
further wherein the measurement signals are treated to
separate environmental noise therefrom.
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Another feature of the present invention is to
provide an automatic measuring apparatus and method for
calculating the height and weight, and further capable
of providing data on the body surface area and
percentile for the age of the subject as well as
calculating the subject's age based on relevant
parameters entered into the computer by the operator.
According to the above features, from a broad
aspect, the present invention provides an automatic
measuring apparatus for calculating the height and
weight of human subjects. The apparatus comprises an
electronic scale having a weight sensor to sense the
weight of the subject standing thereon. A sonar head
is positioned stationary a predetermined distance above
the scale sufficient to permit the subject to stand
upright on the scale and below the sonar head. The
sonar head has a sound wave emitter and a plurality of
sound wave receptors. A data processing means is
connected to the receptors. Means is provided to
activate the data processing means. The sound wave
receptors and a weight sensor provide digital output
measurement signals to the data processing means
representative of measurements of a subject standing
upright on the scale. The sound wave receptors provide
further digital reference signals when no subject is
standing on the scale. The data processing means has a
software to calculate the weight and height of the
subject based on said measurement and said reference
signals.
According to a further broad aspect of the
present invention there is provided a method of
automatically measuring and calculating the height and
weight of a subject comprising the steps of placing the
subject upright on an electronic scale and under a
stationary sonar head having a sound wave emitter and a
plurality of sound wave receptors. A data processing
means is actuated to initiate the sonar head and to
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receive digital output measurement signals from the
sound receptors. The data processing means also
receives measurement signals from a weight sensor
associated with the scale. The sonar head is actuated
without the subject standing on the scale to provide
further digital reference signals to the data
processing means. The digital output measurement
signals and further digital reference signals are
processed in accordance with a software to calculate
the weight and height of the subject.
BRIEF DESCRIPTION OF DRAWINGS
A preferred embodiment of the present invention
will now be described with reference to the
accompanying drawings in which:
FIG. 1 is a simplified schematic view showing
the measuring apparatus of the present invention and
wherein the height and weight of the subject is being
calculated automatically by the apparatus;
FIG. 2 is a simplified block diagram showing how
the echoes or sound wave signals at the output of each
sound receptor is processed to be converted into
digital output measurement signals;
FIG. 3A is a plan view showing the construction
of the sonar head;
FIG. 3B is a perspective view of the sonar head;
FIG. 4A is an illustration of the echo signal
without a subject positioned on the scale;
FIG. 4B is an illustration of the signal with
the patient positioned on the scale;
FIG. 4C is an illustration of the resultant
signal when the signal of Fig. 4A is subtracted from
the signal of Fig. 4B;
FIG. 4D is an illustration of a template which
has the same shape as the target's echo;
FIG. 4E is an illustration of the signal
correlated with the template;
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FIGS. 5A to 5C are illustrations of the signals
showing how the top of the subject's head is detected;
and
FIG 6 is a schematic illustration showing how
the distance between the emitter and the uppermost
portion of the patient's head is calculated using
triangulation.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings and more particularly
to Fig. 1, there is shown generally at 10 the automated
measuring apparatus of the present invention for
calculating the height and weight of a human subject 11
standing on an electronic scale 12 in an upright manner
and assisted by a vertical surfave 13. A sonar head 14
is disposed a predetermined distance above a top flat
surface 15 of the scale 12 to permit the subject 11 to
stand upright therebetween, as herein illustrated. The
sonar head emits sound waves in the direction of the
subject 11 and also receives echoes or reflected sound
waves from the subject as well as from other objects in
the room, such as the operator (not shown) and walls,
etc. and these are considered to be reflected noise.
A data processing circuit or system 16 is
connected to the sonar head 14 and to a weight sensor
17 associated with the electronic scale 12, as well as
a thermistor assembly 18 which senses ambient
temperature when the subject 11 is standing on the
scale. These input connections feed measurement
signals to the data processing circuit 16. A control
panel 19 and/or keypad 21 is conveniently positioned on
the wall member or post 20 or elsewhere to actuate the
data processing circuit and to provide other control
functions, and to input information into the data
processing circuit 16. The processing circuit is
provided with a memory 22 controlled by a computer
program. The output 23 of the data processing circuit
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is connected to a printer 24 or other output devices to
provide a print-out or display of information relating
to the subject 11 being analyzed.
Referring now additionally to Figs. 2, 3A and
3B, there is shown in Figs. 3A and 3B the construction
of the sonar head 14. As herein shown, it consists of
a substantially rectangular housing 25 having flat
receptive plane 26 at the center of which is mounted a
sound emitting device 27 capable of transforming an
electric signal into an acoustic signal. A plurality
of sound wave receptors, herein microphones 28, are
equidistantly spaced about the emitter 27 in the plane
26 and, as herein shown, are positioned on straight
axes defining a square configuration. The housing 25,
as shown in Fig. 1, is secured with its receptive plane
26 disposed substantially parallel to the upper flat
support surface 15 of the scale 12.
Summarizing briefly the operation of the
apparatus and method for automatic measurement of a
subject's height and weight, the subject is firstly
positioned to stand upright on the scale 12 which is a
commercially available digital scale. The sonar head
14 is disposed stationary approximately 30 cm above his
head 11' and the emitter 27 is actuated through the
control panel 19 or keypad 21 to start emitting sound
waves in the direction of the subject. An operator
then enters basic data into the data processing circuit
by means of the panel 19 or keypad 21. This basic data
includes the date of birth, sex, age, and a chart
number pertaining to the subject 11, and depresses
another key on the control panel or keypad. Within a
few seconds the data processing circuit feeds
information signals to the printer 24 where the height,
weight, body surface area, and percentile for the age
of the subject, as well as the basic data for
identification of the subject is printed. The print-
out can be provided on pre-pasted paper which is then
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immediately pasted on the file of the subject by the
operator, who can be a technician or nurse.
Obtaining these data involves firstly the
calibration of the instrument after correction of the
speed of sound at ambient temperature. The digital
output of both the scale and the ultrasonic sensor is
integrated through the data processing circuit 16 with
the use of a software that calculates the height,
weight and the body surface area (by applying the
Dubois formula). The percentile for height and weight
of the patient is also given using equations derived
from data readily available and stored in the memory
22.
When the system is switched on through the
control panel 19 or keypad 21, the processor excites
the emitter 27 to generate a sound wave. The emitter
transforms an electric signal into an acoustic signal.
The sound wave of this acoustic signal travels
downwards, hits the subject 11 and other objects in the
area thereof, and reflects back to the microphones 28.
The reflected signal is known in the art as an echo,
and the echo is transformed into an electric signal by
the microphones.
As shown in Fig. 2, the signal is then amplified
by the amplifier 30 and directed to a pole 31 of a
multi-position switch 32 which is operated by the data
processing circuit 16, which is a computer. The
software controls the circuit to alternatively select
one of the channels 33 connected to a respective one of
the microphones, herein eight microphones 28. The
signal received in the selected channel is then
attenuated by a control amplifier/attenuator 34 having
a gain which is proportional to the square of the sound
wave flight time. The purpose of this is to compensate
for the loss of power of echo which is proportional to
the square of the target distance. The resulting
scaled signal at the output 35 of the attenuator 34 is
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then fed to an analog/digital converter 36, and the
sampled data signal is stored in the memory 22 of the
computer.
The data processing circuit 16 processes the
output measurement signals from the sound wave
receptors or microphones 28, and signal subtraction is
used in order to separate the echo from the noise,
cross-talk, echo from the room and from the lateral
walls, etc. When the subject 11 stands under the sonar
head 14, the echo of the patient's head 11', superposed
with the noise as shown in Fig. 4B, is memorized when
the operator performs the first step measuring the
subject. The subject is then asked to step down from
the scale 12 and the noise or echo of the surrounding
space is memorized, and such is illustrated in Fig. 4A.
The processor then subtracts the data representative of
the signal shown in Fig. 4A from the signal of Fig. 4B
to obtain a signal, as shown in Fig. 4C, representative
of the subject. In order to locate the echo as shown
in the circle 37 in Fig. 4B with precision and to
eliminate more noise, the resulting signal 38 is
correlated with a template 39, as shown in Fig. 4D.
This template is the same shape as the target's
(subject) echo. The template 39 is sampled at a
frequency eight times higher than the signal. The
resulting correlated signal is then eight times more
detailed and free of the ambient room noise. Fig. 4E
is a representation of the signal correlated with the
template.
As shown in Figs. 5A to 5C, when a match is
encountered on the signal, a lobe appears in the
correction signal, as shown in Fig. 5B. If the lobe is
higher than the determined threshold, the threshold
being represented at 40 in Fig. 5A, this lobe 41 and
the top is located with precision. This yields the
round-trip flight time of the sound wave. The same
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process is repeated for each of the signals in the
channels 33.
The data processor 16 also calculates the speed
of sound, and this is effectuated by the software which
reads the temperature signals from the thermistor
assembly 18 to apply a correction factor in the
calculation. The software combines the time of flight
with the speed of sound to calculate the round-trip
distance covered by the sound wave.
As shown in Fig. 6, this calculation also takes
into account the triangulation to calculate the exact
three-dimensional position of the target, herein the
uppermost portion of the subject's head 11' relative to
the sonar head assembly or its receiving surface or
plane 26. The microphones yield four equations and
there are three unknown coordinates. The coordinates
X, Y and Z axes are calculated and an equation is used
to verify the coherence of the three unknowns. The
vertical distance between the plane formed by the
microphones and the uppermost part of the subject's
head 11' is known from the solution of those equations.
Because the sonar head is fixed, the software knows the
calibration distance between the surface 26 of the
sonar head or the plane of the microphones and the flat
top surface of the scale. The height of the patient
can then be calculated by obtaining the difference
between the calibration distance and the vertical
distance between the plane of the microphones and the
uppermost portion of the head 11' of the subject.
The process for measuring the subject's height
and weight requires that the subject be positioned on
the scale 12 and the operator actuates the processor.
The software communicates with the scale 12 to get the
weight of the patient through the sensor 17 which
simultaneously excites the emitter 27 and the sonar
head 14, and samples and memorizes the reflected
signals or digital output measurement signals returned
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from the uppermost part of the patient's head 11'. The
operator then enters other parameters of this subject,
such as date of birth and sex. An internal clock (not
shown) calculates the subject's age. The subject is
then asked to step down from the scale and the software
again excites the emitter to produce another sound
wave. The echo returned from the room alone is sampled
to provide a further digital reference signal. The
software then performs the necessary calculation and
the results are displayed on a printer or a CRT (not
shown), or can be transmitted to a far end central
computer.
The software effectuates the following
calculation. Firstly the data processor processes the
digital signals to improve the quality of the echo
returned from the subject's head, and localizes with
precision the echo on each channel or each receptor,
and calculates the propagation time of the sound wave.
The ambient temperature is obtained from the transducer
assembly 18 and the computer calculates the speed of
sound. The propagation time is combined with the speed
of sound to calculate the round-trip travel distance of
the sound wave. The vertical distance between the
sonar head 14 and the uppermost part of the subject's
head 11' is then calculated by triangulation, as shown
in Fig. 6. This distance is compared with the distance
between the sonar head and the flat top surface 15 of
the scale. From this comparison the height of the
subject is calculated. The software then finds the
percentile body height and weight of the subject with
internal growth tables stored in the memory 22.
It is within the ambit of the present invention
to cover any obvious modifications of the preferred
embodiment described herein, provided such
modifications fall within the scope of the appended
claims. It is also conceived that this apparatus may
be modifiable to provide, in addition with the
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parameters herein described, a parameter indicative of
the body temperature of the subject, blood pressure,
pulse rate, and peripheral oximetry.
