JPH0455256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an infrared detection device used for detecting heat rays emitted from a human body, that is, infrared rays, for the purpose of crime prevention, for example.

<Prior Art> Infrared sensors that detect infrared rays are generally classified into two types: quantum type sensors that utilize the photoelectric effect of semiconductors, and thermal type sensors that utilize the thermoelectric effect or pyroelectric effect.

Although the quantum type has very high sensitivity, its response wavelength range is narrow and cooling is required for infrared detection, so its use remains limited. On the other hand, thermal type sensors have low detection sensitivity but are inexpensive, operate at room temperature, and have no wavelength dependence. For this reason, recently thermal infrared sensors,
In particular, pyroelectric infrared sensors are used in various fields.

A pyroelectric infrared sensor is a type of infrared sensor that detects temperature by utilizing the pyroelectric effect, in which when a temperature change is applied to a pyroelectric crystal, a charge is generated on the surface of the pyroelectric crystal due to a change in spontaneous polarization. It is a temperature sensor and is used for human body detection, flame detection, temperature detection, etc.

By the way, pyroelectric infrared sensors have the drawbacks of high impedance and susceptibility to external noise, as is clear from the above operating principle of detecting temperature changes using charges generated on the surface of a pyroelectric crystal. are doing. Therefore, in a pyroelectric infrared detection device using this type of pyroelectric infrared sensor, a condensing mirror is placed around the mounting part of the pyroelectric infrared sensor, and the infrared rays emitted from the infrared source are The light is focused on a shaped infrared sensor to increase the S/N ratio.

The conventionally used pyroelectric infrared detection device is configured to focus reflected light on a pyroelectric infrared sensor placed opposite a condensing mirror formed of a concave reflective surface.

However, as mentioned above, because the pyroelectric infrared sensor was placed opposite the condensing mirror,
The entire device is large in size, and the mirror must be formed into a concave reflective surface to serve as a condensing mirror, making it difficult to manufacture.

For this reason, as an improved version, Fig. 8a and Fig. 8b
, the pyroelectric infrared sensor 14 is mounted perpendicularly to the upper surface 12 of the housing 11 so that the reflected light is projected onto the pyroelectric infrared sensor 14 located in the opening 13 of the upper surface 12 of the housing 11. Pyroelectric infrared detection device 10 having a mirror piece 15 mounted at the center
was considered. The pyroelectric detection elements 14a and 14b of the pyroelectric infrared sensor 14 in this pyroelectric infrared detection device 10 are directly connected with the same type of polarization as shown in the circuit diagram shown in FIG. It is output from an emitter follower impedance conversion circuit using a transistor (FET). Note that R1 and R2 are resistors. In FIG. 9, the pyroelectric infrared detecting elements 14a and 14b with the same polarity are directly connected to each other, but they may be connected in parallel with different polarizations.

In this configuration, the operation will be explained using the operation explanatory diagram in FIG. 10 and the waveform diagram in FIG. 11. When a human body emitting heat rays, that is, infrared rays, arrives at the area () from a relatively far distance, one pyroelectric infrared detection element 14a and another pyroelectric infrared detection element 14a placed at a distance d from this element are detected. Detection element 1
Since infrared rays are incident on both of 4b, the differential output is extremely small. Next, in the region (), that is, the shielding and reflecting region, the mirror piece 15 shields infrared rays from the pyroelectric infrared detection element 14b,
Since the pyroelectric infrared detection element 14a has the effect of reflecting and projecting infrared rays and making them incident, a differential output level approximately twice as high as that obtained when infrared rays are simply shielded is obtained. . In region (), the pyroelectric infrared detection element 14a detects infrared rays, and since the human body is in the area shielded by the mirror piece 15, the pyroelectric infrared detection element 14b detects the infrared rays.
does not detect infrared rays and provides differential output. Furthermore, when a human body comes to the area (), both pyroelectric infrared detection elements 14 are detected without being affected by the mirror piece 15.
a and b are detected, but the differential output is small. In region (), the pyroelectric infrared detection element 14b detects infrared rays, and since the human body is in the area shielded by the mirror piece 15, the pyroelectric infrared detection element 14a detects infrared rays.
does not detect infrared rays and differential output appears. Also,
Mirror piece 15 in the shielding and reflection area of area ()
acts to reflect infrared rays and make them incident on the pyroelectric infrared detection element 14b, and blocks infrared rays from the pyroelectric infrared detection element 14a to obtain a large differential output. In region (), both pyroelectric infrared detection elements 14a and 14b detect infrared rays, and the differential output is small. Therefore, at this time, the output of the pyroelectric infrared detection elements 14a, 14b and the FET
The output status is as shown in Figure 11a and b,
Outputs appear in the FET in areas (), (), (), (), and even if the human body does not move from area () to (), it will at least move from area () to () or from area () to (). Infrared rays can be detected simply by moving to

Furthermore, by arranging a plurality of mirror pieces 15 at appropriate intervals around the infrared sensor 14 as shown in FIG. 12, passage of a human body can be detected in a narrower area.

<Problems to be Solved by the Invention> As described above, arranging the mirror pieces approximately radially around the pyroelectric infrared detection element has a remarkable advantage, but the mirror pieces are fixed to the housing. Therefore, it has not been possible to easily increase the detection area in which the differential output of the pyroelectric infrared detection element occurs. Therefore, it was not possible to detect minute movements of the hand or arm within the detection area.

<Means for Solving the Problems> The present invention has been made to solve the above problems, and includes a single mirror piece or a plurality of mirror pieces arranged around a pair of pyroelectric infrared detecting elements. The pyroelectric infrared detection device is characterized in that an auxiliary body is disposed to block part of the infrared rays incident on the pair of pyroelectric detection elements.

<Example> Hereinafter, an example of the pyroelectric infrared detection device of the present invention will be described in detail using the drawings.

In FIG. 1, a pyroelectric infrared detection device 1 has an opening 4 in the center of the upper surface 3 of a resin cylindrical housing 2.
A pyroelectric infrared sensor 5 is disposed in the opening 4, which is housed in the housing 2 and includes a pair of pyroelectric infrared detection elements 51a and 51b. Although the infrared detecting elements 51a and 51b are shown exposed in the drawing, they are actually housed inside the infrared sensor 5, and the heat rays enter through an optical filter. Top surface 3 of housing 2
Six mirror-finished mirror pieces 6 are mounted around the pair of pyroelectric infrared detecting elements 51a and 51b at appropriate intervals, for example, every 60 degrees. Between the pyroelectric infrared sensor 5 and the mirror piece 6, and on a plane that bisects the pyroelectric infrared detection elements 51a and 51b, an auxiliary thin rod-shaped member made of a substance that shields infrared rays is provided. Place body 7. The auxiliary body 7 may be attached on top of the infrared sensor 5 as shown, but it may also be fixed to the housing 2 across the infrared sensor. In either case, it is disposed close to the incident surface of the infrared sensor.

The operation of the embodiment in which this auxiliary body 7 is arranged will be explained with reference to the operation diagram in FIG. 2 and the waveform diagrams in FIGS. 3a and 3b. With this arrangement of the auxiliary body 7, the range in which the pyroelectric infrared detection elements 51a and 51b view the auxiliary body 7 becomes a new shielding area, as shown in FIG.

In this region, the infrared rays from the heat source are detected by the pyroelectric infrared detection elements 51a and 51b, and therefore the differential output of the FET becomes small. Next, in the newly generated shielding area, infrared rays are detected only by the first pyroelectric infrared detection element 51a, and infrared rays are detected by the auxiliary body 7 to the second pyroelectric infrared detection element 51b. is blocked and not detected,
Differential output appears on the FET. In this region, infrared rays are detected by both the pyroelectric infrared detection elements 51a and 51b, and the differential output to the FET becomes small. When the heat generation source further advances and comes to the shielding and reflection area, the second pyroelectric infrared detection element 51b is shielded by the mirror piece 6 and no infrared rays enter it, but the first pyroelectric infrared detection element 51b is blocked by the mirror piece 6. Since the direct infrared rays and the infrared rays reflected by the mirror piece 6 are incident on the element 51a, an output approximately twice as large as that in the case where the infrared detecting element 51b is simply shielded appears. In the shielded area of the area, the infrared rays are directly
The light enters the second pyroelectric infrared detection element 51a, and is not input to the second pyroelectric infrared detection element 51b because it is blocked by the mirror piece 6. At this time, an output appears at the FET. In this region, the infrared rays are not blocked by the mirror piece 6 and the auxiliary body 7 and are incident on the first and second pyroelectric infrared detection elements 51a and 51b, where they are detected, so that the differential output of the FET becomes small. Furthermore, in the shielded region, the infrared rays to the second pyroelectric infrared detection element 51a are blocked by the mirror piece 6 and are not incident, but are detected only by the second pyroelectric infrared detection element 51b, and there is no difference in the FET. A dynamic force appears. In the shielding and reflection region, the first pyroelectric infrared detection element 51a is shielded by the mirror piece 6 and no infrared rays are incident on it, and the second pyroelectric infrared detection element 51b receives direct infrared rays and mirror piece 6. Since the infrared rays reflected by the FET are incident, a large output appears in the FET. In this region, infrared rays are detected by both the pyroelectric infrared detection elements 51a and 51b, and no differential output appears in the FET. In the shielded area, the infrared rays are detected only by the second pyroelectric infrared detection element 51b, and the infrared rays are not detected by the first pyroelectric infrared detection element 51a because they are blocked by the auxiliary body 7, so that the infrared rays are not detected by the FET. Differential output appears. Furthermore, infrared rays are detected by pyroelectric infrared detection elements 51a and 51b in the area.
The differential output of the FET becomes smaller.

The second embodiment is shown in the operation explanatory diagram of FIG. In the second embodiment, the position of the mirror piece 6 is slightly shifted in relation to the pyroelectric infrared detecting elements 51a and 51b, and the infrared rays reflected by the mirror piece 6 are transmitted to one of the pyroelectric infrared detecting elements (the second embodiment). In FIG. 4, even if the light is incident only on the first pyroelectric infrared detecting element 51b and not on the other, the auxiliary body placed between the first and second pyroelectric infrared detecting elements 51a and 51b 7, a new shielding area S1 can be easily created.

The action of this new shielding area S1 is the same as in the first embodiment, and when the heat source crosses this shielding area S1, infrared rays are detected in this area as well in the same manner as in the first embodiment. be able to.

A third embodiment is shown in FIG. The third embodiment is a shielding and reflection detection area where infrared rays hit the auxiliary body 7, are reflected, and enter the second pyroelectric infrared detection element 51b (or the first pyroelectric infrared detection element 51a). By arranging the auxiliary body 7 in a part of the inner RS, a new shielding area S3 can be created in a part of the area.

In addition, the auxiliary body 7 is replaced by a pyroelectric infrared detection element 51.
Similarly, by arranging the auxiliary body 7 in front of the mirror piece 6 as shown in FIG. 6 as a fourth embodiment, instead of between a and 51b, a new shielding area S3 is created.
can be made.

The new shielding area S3 in these third and fourth embodiments is a shielding area provided within the shielding and reflection detection area RS, and generates an output in response to the movement of a part of the human body such as a hand or arm. Can be done.

A fifth embodiment is shown in FIG. In the fifth embodiment, the auxiliary body 7 is not located between the pyroelectric infrared sensor 5 and the mirror piece 6, but is placed apart from them to create a new shielding area S1.

The operation of the new shielding area S1 of the fifth embodiment is the same as that of the first embodiment, and since the heat source crosses this shielding area S1, the operation of this area is similar to that of the first embodiment. can detect infrared rays.

In this way, as seen in the first to fifth embodiments, the position of the auxiliary body 7 is similar to that of the pyroelectric infrared detection element 51.
51b and the mirror piece 6, or between the pyroelectric infrared detecting elements 51a, 51b and the heat generation source, it can be configured anywhere.

<Effects of the Invention> The pyroelectric infrared detection device of the present invention has been described in detail above, and produces the following effects. In other words, a pyroelectric infrared detection device has a plurality of mirror pieces arranged around a pair of pyroelectric infrared detection elements. Since the detection area where the differential output is generated can be relatively easily increased. Furthermore, since it is sufficient to simply provide an auxiliary body, the shielding area can be easily changed. In addition, it is possible to relatively easily add a small shielding area within the shielding and reflection detection area by the mirror piece, and this makes it possible to detect minute movements of the hand or arm within the reflection detection area with high sensitivity. can be detected.

[Brief explanation of the drawing]

1a, b, and c are a plan view, a front sectional view, and a side sectional view showing one embodiment of the pyroelectric infrared detection device of the present invention; FIG. 2 is an explanatory diagram of the operation of the first embodiment;
FIG. 3a is a waveform diagram showing the output of the pyroelectric infrared detection element, FIG. 3b is a waveform diagram showing the output of the FET, FIG. 4 is an explanatory diagram of the operation of the second embodiment, and FIG. 3
Fig. 6 is an explanatory diagram of the operation of the fourth embodiment, Fig. 7 is an explanatory diagram of the operation of the fifth embodiment, and Figs. 8a and b are conventional pyroelectric infrared devices. A front view and a front sectional view of an example, Fig. 9 is an electric circuit diagram applied to a pyroelectric infrared detection device, Fig. 10 is a conventional operation explanatory diagram, and Figs. 11a and b are infrared sensor elements and FETs. FIG. 12 is another plan view of a conventional pyroelectric infrared detection device. In the figure, 1 is a pyroelectric infrared detector, 2 is a housing,
3 is the top surface, 4 is the opening, 5 is the pyroelectric infrared sensor,
51a and 51b are pyroelectric infrared detection elements, 6 is a mirror piece, and 7 is an auxiliary body.

Claims (1)

[Claims] 1. In a pyroelectric infrared detection device in which a plurality of mirror pieces are arranged around a pair of pyroelectric infrared detection elements, a portion of the infrared rays incident on the pair of pyroelectric detection elements A pyroelectric infrared detection device characterized in that an auxiliary body is arranged to block the pyroelectric infrared detection device.