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Description  |
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FIELD OF THE INVENTION
The present invention relates to an apparatus for detecting the presence of
a person or persons inside a room, the apparatus finding applications, for
example, in prevention of crimes and energy saving as well as in
automation of houses adapted for the aged and handicapped.
BACKGROUND OF THE INVENTION
One known apparatus for detecting every person inside a room processes
images picked up by a camera such as a visible light camera or infrared
camera. Another known apparatus used for the same purpose employs active
sensors such as infrared sensors or ultrasonic sensors to detect a person
within a narrow region. A further known apparatus makes use of a passive
sensor equipped with a shutter mechanism.
In the prior art apparatus for detecting the presence of a person or
persons with a camera, it is necessary to correct the processed image,
depending on the condition of the camera. Also, it is not easy for the
user to set up the apparatus. Furthermore, the apparatus is bulky. In
addition, it consumes a large amount of electric power. Further, the
optical system must be so set up that the dead angle is compensated for.
Therefore, it is inevitable that the optical system is separate from the
image processing portion. Moreover, the camera puts stress on the subject
person. Hence, contrivance is needed in the field of house automation,
especially in the way in which the optical system is received in the
apparatus.
The person presence-detecting apparatus using an active sensor such as an
infrared sensor or ultrasonic sensor constantly emits light, or keeps
oscillating. Therefore, it consumes a large amount of electric power.
Also, this apparatus is cable of covering only a limited narrow area,
since restrictions are imposed on the positional relation between the
emitting portion, or oscillating portion, and the light-receiving portion.
In order to compensate for the dead angle, the sensor must be divided into
plural separate portions which are separated from the signal-processing
portion.
The apparatus comprising the passive sensor having the shutter mechanism
has a portion that is invariably operating. Therefore, it is difficult to
power this apparatus by a battery, and it is impossible to fabricate it as
a unit.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an
integrated apparatus which uses passive sensors each consuming only a
small amount of electric power and which acts to detect the presence of a
person or persons inside a room having a door.
It is another object of the invention to provide an apparatus which acts to
detect the presence of a person or persons inside a room having a door and
which has a novel circuit configuration including a sensor for detecting
movement of the person as well as a sensor for detecting opening and
closing of the door.
The above objects are achieved in accordance with the teachings of the
invention by an apparatus in which a sensor detecting movement of a person
is combined with a sensor detecting the opening and closing of a door, to
detect the presence of the person inside a room.
In one feature of the invention, the sensor detecting the movement of the
person is a pyroelectric infrared sensor. The sensor detecting the opening
and closing of the door is a piezoelectric air pressure sensor. The
pyroelectric infrared sensor utilizes a pyroelectric crystal whose
spontaneous polarization varies with temperature. By making use of this
phenomenon, infrared rays corresponding to the temperature of the human
body and the ambient temperature, respectively, are made to hit the
pyroelectric crystal. A change in the difference in energy between these
two kinds of infrared rays brings about a change in the spontaneous
polarization due to the pyroelectric effect. This, in turn, changes the
surface charge on the electrode portion. A potential difference is
obtained from this change. In this way, the movement of a person within
the optical field of view is detected. The piezoelectric air pressure
sensor comprises a piezoelectric material which is polarized when strain
is applied to it. When atmospheric pressure changes, strain is produced in
the piezoelectric material. As a result, the piezoelectric material is
polarized, generating surface charge on the electrode portion. A potential
difference is developed by the surface charge. Thus, the change in
atmospheric pressure is detected.
One embodiment of the invention lies in an apparatus for detecting the
presence of a person or persons inside a room having a door, said
apparatus comprising: an infrared sensor which detects movement of a
person inside the room and produces a signal indicating the movement of a
person; an air pressure sensor detecting opening and closing of the door
and producing a signal indicating the opening and closing of the door; an
entry-detecting means which is connected with the two sensors and which,
when the signal indicating the movement of a person is applied later than
the signal indicating the opening and closing of the door, produces a
signal indicating the entry of a person; an exit-detecting means which is
connected with the two sensors and which, when the signal indicating the
opening and closing of the door is applied later than the signal
indicating the movement of a person, produces a signal indicating the exit
of a person; a person presence-detecting means which is connected with the
entry-detecting means and also with the exit-detecting means and which,
when the signal indicating the entry of a person is applied, produces a
signal indicating the presence of a person and which, when the signal
indicating the exit of a person is applied, produces a signal indicating
the absence of any person; and an inhibiting means which is connected
between the infrared sensor and the person presence-detecting means and
which, when the signal indicating the movement of a person is produced
after the signal indicating the exit of a person is produced, inhibits the
person presence-detecting means from producing the signal indicating the
absence of any person.
The output signal from the piezoelectric air pressure sensor detecting the
variation in the pressure caused by the opening and closing of the door is
combined with the output signal from the pyroelectric infrared sensor
detecting the movement of a person to detect movement of a person before
and after the door is opened and closed. Consequently, it is possible to
know whether a person enters or leaves the room. The obtained information
is combined with the presence or absence of the output signal from the
infrared sensor to know the presence of a person or persons inside the
room. Preferably, the pyroelectric infrared sensor is a small sensor of
the TO-5 type. Both pyroelectric sensor and piezoelectric air pressure
sensor are passive sensors and so each sensor consumes only a small amount
of electric power. Since the piezoelectric air pressure sensor itself has
no directionality, it can be integrated with the pyroelectric infrared
sensor. Furthermore, the pyroelectric infrared sensor has a wide field of
view and exhibits a high sensitivity. Hence, few restrictions are imposed
on the position at which the infrared sensor is mounted. This makes it
easy to mount the infrared sensor. The output signals from these sensors
are voltages signals and, therefore, it is easy to built the circuit. In
addition, the apparatus can be powered by a battery, since it consumes
only a small amount of electric power. In consequence, a small-sized
integrated apparatus can be fabricated.
Other objects and features of the invention will appear in the course of
the description thereof which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit block diagram of an apparatus for detecting the
presence of a person or persons inside a room having a door, the apparatus
being built in accordance with the present invention;
FIG. 2 is a timing chart of the waveforms of various signals produced in
the apparatus shown in FIG. 1 when a person enters the room;
FIG. 3 is a timing chart of the waveforms of various signals produced in
the apparatus shown in FIG. 1 when one person is present in the room and
another person enters the room; and
FIG. 4 is a timing chart of the waveforms of various signals produced in
the apparatus shown in FIG. 1 when two persons successively leave the room
.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, there is shown an apparatus according to the
invention. This apparatus includes a pyroelectric infrared sensor 1. The
output 6a of this sensor 1 is connected with a monostable multivibrator
4a, another monostable multivibrator 4d, and an AND gate 5d via an
amplification-and-comparator circuit 3a. The apparatus further includes a
piezoelectric air pressure sensor 2 whose output 6c is connected with a
monostable multivibrator 4b via an amplification-and-comparator circuit
3b. The output 6a' of the amplification-and-comparator circuit 3a is
directly connected with one input terminal of the AND gate 5d. Also, the
output 6a' of the amplification-and-comparator circuit 3a is connected
with the other input terminal of the AND gate 5d via the output 6i of the
monostable multivibrator 4d. The gate 5d produces an output signal 6j. The
output 6b of the multivibrator 4a and the output 6d of the multivibrator
4b are connected with an AND gate 5a.
The output 6e of the AND gate 5a is connected with a monostable
multivibrator 4c. The output 6f of this multivibrator 4c is connected with
one input terminal of an AND gate 5b, while the output 6b of the
multivibrator 4a is connected with the other input terminal of the AND
gate 5b. The output 6f of the multivibrator 4c is also connected with one
input terminal of an AND gate 5c, the output 6d of the multivibrator 4b
being connected with the other input terminal of the gate 5c.
The output 6g of the AND gate 5b and the output 6j of the AND gate 5d are
connected with an OR gate 8. The output 6j of the AND gate 5d is connected
with the reset terminal of a flip-flop 9b. The output 6h of the AND gate
5c is tied to the set terminal of the flip-flop 9b. The output 6h of the
AND gate 5c is connected with a monostable multivibrator 4e. The output 6k
of the multivibrator 4e and the output 6l of the flip-flop 9b are
connected with two input terminals, respectively, of an AND gate 5e. The
output 6m of the gate 5e is connected with the reset terminal of a
flip-flop 9a. The output 6n of the OR gate 8 is connected with the set
terminal of the flip-flop 9a. This circuit is powered by a lithium battery
(not shown). Preferably, the battery is incorporated in the circuit.
The operation of this apparatus for detecting the presence of a person or
persons is next described by referring also to FIGS. 2-4. Since the
pyroelectric infrared sensor differentiates its input signal, the sensor
detects only movement of a person or persons. Generally, where a person is
present inside a room, it is hardly likely that he or she constantly moves
about. Also, the parson moves at irregular intervals of time. We have
noticed that whenever a person enters or leaves a room, he or she
inevitably moves. The novel apparatus for detecting the presence of a
person or persons detects the movement of a person made before and after
the door is opened and closed to determine whether the person enters or
leaves the room. Then, the apparatus judges that a person is located
inside the room.
FIG. 2 is a timing chart of the waveforms of various signals produced by
the novel apparatus when a person enters a room. At this time, the door is
opened and closed. Then, the person moves inside the room. First, the
piezoelectric air pressure sensor 2 shown in FIG. 1 detects the opening
and closing of the door and produces output signal 6c indicating the
opening and closing. This output signal 6c is applied to the
amplification-and-comparator circuit 3b, which produces output signal 6c'
of TTL level. The leading edge of the output signal 6c' triggers the
monostable multivibrator 4b, so that the multivibrator produces output
signal 6d. Subsequently, the pyroelectric infrared sensor 1 detects the
movement of the person and delivers output signal 6a indicative of the
movement. This output signal 6a is applied to the
amplification-and-comparator circuit 3a to cause it to produce output
signal 6a' of TTL level. This output signal 6a' triggers the monostable
multivibrators 4a and 4d to produce output signals 6b and 6i,
respectively. The output 6i from the multivibrator 4d and the output 6a'
from the amplification-and-comparator 3a are applied to the two input
terminals, respectively, of the AND gate 5d. When the pyroelectric
infrared sensor 1 produces noise as shown in FIG. 2, i.e., when a single
impulse is generated due to a malfunction, the output signal 6j of the AND
gate 5d remains low, whereby the noise can be removed. If the person moves
during the given width of the output signal 6i from the multivibrator 4d,
then the output signal 6j from the AND gate 5d goes high. Thus, the
movement of the person can be confirmed without being affected by the
malfunction.
The output signal 6b from the monostable multivibrator 4a indicating the
movement of a person and the output signal 6d from the monostable
multivibrator 4b indicating the opening and closing of the door are
applied to the AND gate 5a. When the output signal 6b of a given width and
the output signal 6d of a certain width are overlapped, the AND gate 5a
produces high output signal 6e. Hence, the movement of the person made
before and after the door is opened and closed can be detected. The
trailing edge of the output signal 6e triggers the monostable
multivibrator 4c. The output signal 6f from this multivibrator 4c is
applied to the AND gate 5b, together with the output signal 6b from the
monostable multivibrator 4a. The output signal 6g from the AND gate 5b
goes high only when the air pressure sensor output signal indicating the
opening and closing of the door is detected earlier than the infrared
sensor output signal indicating the movement of the person. Consequently,
this output signal 6g indicates the entry of a person.
This output signal 6g and the output signal 6j from the AND gate 5d are
applied to the OR gate 8. The output signal 6n from the OR gate 8 triggers
the flip-flop 9a, so that the output signal 7 from this flip-flop goes
high. This output signal 7 indicates that a person is present inside the
room. When a person enters the room, the output signal 6g from the AND
gate 5b can be used to create information given to the person.
FIG. 3 is a timing chart showing the waveforms of signals produced when one
person is present inside a room and another person enters it. The output
signal 7 from the flip-flop 9a which indicates the presence of a person
remains high from the first. Since the person is present inside the room,
the pyroelectric infrared sensor 1 detects the movement of the person. The
output signal 6a from this sensor 1 triggers the monostable multivibrator
4d via the amplification-and-comparator 3a. The output signal 6i from this
multivibrator 4d and the output signal 6a' from the
amplification-and-comparator circuit 3a are applied to the AND gate 5d.
The output signal 6j from the AND gate 5d goes high in response to the
movement of the person without being affected by a malfunction. The high
output signal 6j from the AND gate 5d is applied to the set terminal of
the flip-flop 9a via the OR gate 8. Since the flip-flop 9a has been
already set, the output signal 7 from the flip-flop 9a is kept high. This
means that a person is present inside the room.
As shown in FIG. 3, if another person subsequently enters the room, a
signal which sets the flip-flop 9a is applied to the flip-flop 9a from the
output 6g of the AND gate 5b via the OR gate 8, in the same way as the
operation described already in connection with FIG. 2. However, the
flip-flop 9a has been already set as described above. Therefore, the
output signal 7 from the flip-flop 9a is kept high.
FIG. 4 is a timing chart showing the waveforms of signals produced in the
following situation: Two persons are present in the room as described
above; one of them leaves the room; and the other leaves the room after a
while. When one of them leaves the room, the pyroelectric infrared sensor
1 detects the movement of the person who is approaching the door. The
sensor 1 produces the output signal 6a, which triggers the monostable
multivibrator 4a via the amplification-and-comparator circuit 3a. Then,
the door is opened. The piezoelectric air pressure sensor 2 detects the
variation in the pressure and delivers the output signal 6c, which
triggers the monostable multivibrator 4b via the
amplification-and-comparator circuit 3b. As described previously, the
output signal 6b from the multivibrator 4a and the output signal 6d from
the multivibrator 4b are applied to the AND gate 5a and so the output
signal 6e from this gate 5a responds to the movement of the person before
and after the door is opened and closed. The trailing edge of the output
signal 6e triggers the monostable multivibrator 4c. The output signal 6f
from this multivibrator 4c and the output signal 6d from the monostable
multivibrator 4b are applied to the AND gate 5c. The output signal 6h from
this gate 5c goes high only when the output signal from the pyroelectric
infrared sensor 1 indicating the movement of a person is detected earlier
than the output signal from the piezoelectric air pressure sensor 2 that
indicates the opening and closing of the door. It is possible to know from
this high output signal 6h that a person has left the room.
The leading edge of the output signal 6h triggers the flip-flop 9b. When
only one of the two persons present inside the room leaves it, it is
possible that the remaining one moves intermittently. If such movement is
made, it is detected by the infrared sensor 1. The output signal 6a from
this sensor 1 is applied to the amplification-and-comparator circuit 3a.
The output signal 6a' from this amplification-and-comparator circuit 3a
causes the AND gate 5d to produce the output signal 6j as described above.
The trailing edge of this output signal 6j resets the flip-flop 9b.
Therefore, the output signal 6m from the AND gate 5e, or the signal
applied to the reset terminal of the flip-flop 9a, is kept low, the gate
5e receiving the output signal 6l from the flip-flop 9b and the output
signal 6k from the monostable multivibrator 4e. In consequence, the
flip-flop 9a is not reset. Hence, the output signal 7 from the flip-flop
9a remains high. The output signal 6h from the AND gate 5c indicates that
a person has left the room. On the other hand, the high output signal 7
from the flip-flop 9a indicates that a person still stays inside the room.
That is, if movement of a second person is detected after a first person
leaves the room, or within a given time set by the monostable
multivibrator 4e, then the flip-flop 9a is stopped from being reset. This
indicates that a person still remains.
If the last person remaining inside the room subsequently leaves it, the
infrared sensor 1 detects movement of the person approaching the door and
produces the output signal 6a as shown in FIG. 4. This output signal 6a
triggers the multivibrator 4a via the amplification-and-comparator circuit
3a. Then, the door is opened. The air pressure sensor 2 detects the
variation in the pressure and delivers the output signal 6c. This output
signal 6c triggers the multivibrator 4b via the
amplification-and-comparator circuit 3b. The output signal 6d from the
multivibrator 4b and the output signal 6b from the multivibrator 4a are
applied to the AND gate 5a. The trailing edge of the output signal 6e from
this gate 5a triggers the multivibrator 4c. The output signal 6f from the
multivibrator 4c and the output signal 6d from the multivibrator 4b are
applied to the AND gate 5c. The output signal 6h from this gate 5c
indicates that a person has left the room, as described already. The
leading edge of this output signal 6h triggers the multivibrator 4e. The
trailing edge of this output signal 6h sets the flip-flop 9b.
When no person remains inside the room, the infrared sensor 1 detects no
movement of persons. The flip-flop 9b is not reset but remains set. That
is, the output signal from the flip-flop 9b is kept high. When a given
time elapses since the last person left the room, the output signal 6k
from the monostable multivibrator 4e goes high. As a result, the output
signal 6m from the AND gate 5e goes high, the gate 5e receiving the output
signal 6l from the flip-flop 9b and the output signal 6k from the
multivibrator 4e. This resets the flip-flop 9a. The output signal 7 from
the flip-flop 9a goes low for the first time, indicating that no person
remains inside the room.
Where two persons are present in the room, if they leave the room
simultaneously rather than one after another, the infrared sensor 1 no
longer detects movement of persons. Therefore, the flip-flop 9b is not
reset. The flip-flip 9a is reset after a lapse of a given time which is
set by the monostable multivibrator 4e.
Where two persons are present inside the room, if one of them leaves the
room, and if the remaining one does not move until the given time set by
the multivibrator 4e passes, then the infrared sensor produces no output
signal. The flip-flop 9a is once reset. This indicates that no person is
present in the room. If the remaining person moves subsequently, the
movement is detected by the infrared sensor. The output signal 6j from the
AND gate 5d is applied to the set terminal of the flip-flop 9a via the OR
gate 8. The output signal from the flip-flop 9a goes high, indicating the
presence of a person or persons inside the room, irrespective of whether
the signal 6g indicating the entry and the signal 6h indicating the exit
are present or not.
As described in detail thus far, the novel apparatus uses the piezoelectric
air pressure sensor detecting variations in the pressure caused by the
opening and closing of the door, as well as the pyroelectric infrared
sensor detecting movement of a person. Thus, the movement of the person
which is made before and after the door is opened and closed is detected.
This enables ascertainment of the entry and exit of a person. This
ascertainment is combined with the information obtained from the
pyroelectric infrared sensor, i.e., the presence or absence of a person,
to know whether at least one person is present inside the room.
Preferably, the pyroelectric infrared sensor is a small infrared sensor of
the TO-5 type. Both pyroelectric infrared sensor and piezoelectric sensor
are passive sensors and, therefore, each sensor consumes only a small
amount of electric power. Additionally, the piezoelectric air pressure
sensor and the pyroelectric infrared sensor can be combined into a unit,
because the piezoelectric air pressure sensor itself has no
directionality. Since the pyroelectric infrared sensor has a wide field of
view and shows a high sensitivity, the position at which the sensor is
mounted can be varied over a wide region. This facilitates mounting the
sensor. Furthermore, an arithmetic and logic unit can be easily
fabricated, since the outputs from these two sensors are voltage signals.
Further, the apparatus consumes only a small amount of electric power.
This permits the apparatus to be powered by a battery. In this way, a
small integrated apparatus can be built.
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