Thermopile far infrared radiation detection apparatus for...

Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive

Reexamination Certificate

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C250S338100, C250S340000

Reexamination Certificate

active

06552345

ABSTRACT:

BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a thermopile far infrared radiation detection apparatus for crime prevention and an indoor type thermopile far infrared radiation detection apparatus for crime prevention, which detect an intruder into a space by using three or more thermopiles.
(2) Description of the Prior Art
Conventionally, as a method to detect an intruder into a space such as an office, such method is known that it detects a temperature emitted from a human body, that is, a far infrared radiation; and as a detector thereof, passive infrared detection devices such as pyroelectric devices, thermopiles, etc. are used.
A pyroelectric device, which is conventionally used, is a device that detects a change in temperature; and is effective in the case where an intruder enters at a speed more than a predetermined speed.
At first, a conventional detection method utilizing a single pyroelectric device will be explained in reference to
FIGS. 9-12
.
FIG. 9
shows a detection apparatus c in which a lens b is provided in front of a detector a which has a pyroelectric device. d in the figure shows a human body which moves in the space.
A far infrared radiation which is emitted from the human body d is converged onto the detector a by the lens b. The detector a outputs an electric signal if the amount of the far infrared radiation changes; and by this output, it is detected as to whether or not there is an intruder in the space.
FIGS. 10 and 11
show output changes from the detector a in the case where a human body d is moving in the space. When the human body d enters the detection space, the detector a detects a temperature of the human body d and outputs such detection as an electric signal. In accordance with the movement of the human body, the output value changes up and down as time goes. Next, when the human body d is inside the detection space, no output changes appear since the amount of far infrared radiation which enters into the detector a is uniform. And, when the human body d exits from the detection space, the detector a detects the temperature of the human body d and outputs the detection as an electrical signal. In accordance with the movement of the human body d, the output value changes up and down as time goes.
Here,
FIG. 10
shows the case in which the human body d moves at a high speed; and,
FIG. 11
shows the case in which the human body d moves at a low speed.
As apparent from these
FIGS. 10 and 11
, in case that a human body d is moving at a certain speed, it is easy to detect changes of the human body d; however, in case that a human body is moving slowly or stands still, the detector is not able to clearly detect the differences between the body temperature and the room temperature.
As explained above, in case that a pyroelectric device is used for detection, when an intruder's speed in entering is slow or an intruder stands still, the change between the intruder's temperature and background temperature inside the space, namely, the difference between body temperature of the intruder and the room temperature is not be able to be distinguished; thereby, it is not possible to surely detect an intruder.
On the other hand, a thermopile detects an absolute value of the temperature rather than the changes in temperature as in the case of pyroelectric device; therefore, it is conventionally used as a radiation thermometer to measure an absolute value of the temperature of the subject of measurement.
FIG. 12
shows the output changes generated in response to the movement of a human body d when a conventional thermopile is used in the configuration shown in FIG.
9
.
FIG. 12
shows respective output changes in the cases: the room temperature is 25° C.; the room temperature is higher than 25° C.; and the room temperature is lower than 25° C.
FIG. 13
shows an output change in the case where the output signal is treated such that the detection of far infrared radiation by a thermopile is as same as the detection responses of a pyroelectric device.
Further, there is such a detection method of an intruder into a space that utilizes a thermal image device in which a plurality of thermopiles are arranged in two dimensions; an output of each devices is retrieved; and outputs from all devices are treated as a thermal image.
A conventional configuration which utilizes a plurality of thermopile devices is explained in reference to
FIGS. 14-17
.
FIG. 14
shows a detection apparatus g in which a lens f is disposed of in front of detectors e
1
, e
2
and e
3
, which are provided with variable amplifiers j
1
, j
2
and j
3
. In this figure, h
1
, h
2
and h
3
indicate respective spaces in which the detectors e
1
, e
2
and e
3
are capable of detection. If a human body moves in either of spaces h
1
, h
2
and h
3
, the temperature of the human body is detected through the lens f by one of the detectors e
1
, e
2
or e
3
; the detected far infrared radiation, that is, the body temperature, is amplified by the variable amplifiers j
1
, j
2
and j
3
as electric outputs; and is outputted as electric signal outputs k
1
, k
2
and k
3
. And, by the changes of these outputs k
1
, k
2
and k
3
, it is detected whether or not there has been an entry of intruder.
Accordingly, the thermal distributions of spaces h
1
, h
2
and h
3
are always measured; and in case no intruder is in either of h
1
and h
2
or h
3
, there is almost no differences among the outputs k
1
, k
2
and k
3
as shown in
FIG. 15A
; however, if an intruder enters into either of h
1
, h
2
and h
3
, due to the temperature of a human body, the temperature of one of the spaces h
1
, h
2
or h
3
increases and in accordance with it, there will be a difference among the outputs k
1
, k
2
and k
3
from these variable amplifiers j
1
, j
2
and j
3
as shown in FIG.
15
B.
FIG. 15B
shows that an intruder has entered the space h
2
. By increasing the number of the detectors, e
1
, e
2
and e
3
, it becomes possible to measure detailed thermal distributions in the prescribed area, thereby, it becomes possible to capture a whole detection space as an image (infrared image) and it becomes possible to make sure that there has been an entry be intruder into the space.
Incidentally,
FIG. 16
shows the output changes of thermopile in response to the changes of room temperature.
As shown in the figure, in the cases in which the room temperature is either low or high, a proper output cannot be generated because the output is saturated. Therefore, when the room temperature is low, it is necessary to increase the sensitivity; and when the room temperature is high, it is necessary to decrease the sensitivity. Therefore, as shown in
FIG. 14
, the input side and the output side of the variable amplifiers j
1
, j
2
and j
3
are connected to an automatic sensitivity adjustment apparatus m; and the outputs k
1
, k
2
and k
3
from the variable amplifiers j
1
, j
2
and j
3
are adjusted to maintain an average value by the variable amplifiers j
1
, j
2
and j
3
.
FIG. 17
shows another conventional detection apparatus. The detection apparatus shown in the figure is configured such that a plurality of detector e
1
, e
2
, e
3
, e
4
and e
5
are connected to an amplifier n, which amplifies outputs obtained from the respective detectors through an electronic switch p. And, by sequentially switching the electronic switch p, outputs from the respective detectors e
1
, e
2
, e
3
, e
4
and e
5
are detected and are output after amplification by the amplifier n.
However, even in the case where a thermopile is used, if a single thermopile is used and the room temperature is high, the difference z
1
between the room temperature and the body temperature is very slight as shown in
FIG. 12
, therefore, the output changes cannot be detected sufficiently and it is not possible to assuredly determine to make an output that there is a human body. Further, in the case where the room temperature is low, the difference between the room temperature and the body temperature Z
2
is large

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