JPS63132123A - Pyroelectric type infrared detector - Google Patents

Abstract

PURPOSE:To detect heat generation even on both sides at distance from a device by forming the external edge of a mirror piece rectangularly and making intervals of detection zones by the reflection of the mirror piece constant. CONSTITUTION:An infrared sensor 2 has pyroelectric infrared detecting elements 2a and 2b in two sections divided by the mirror piece 4, and an infrared ray reflected by the mirror piece 4 is made incident. Then the external edge of the mirror piece 4 is constituted rectangularly and then an equation I holds on a line Y2 having a 45 deg. angle to a Z axis running between the elements 2a and 2b. The widths DELTAY and DELTAY2 between detection zones (2) and (4) are equal to each other. For the purpose, the external edge of the mirror 4 is formed rectangularly to make the widths of areas (2) and (4) in detection zones constant in a plane crossing the Z axis at constant distance from the device at right angles.

Description

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

<Prior Art> In recent years, pyroelectric infrared sensors have been used in various fields. Pyroelectric infrared sensors utilize the pyroelectric effect in which when a temperature change is applied to a pyroelectric crystal, charges are generated on the surface of the pyroelectric crystal due to a change in spontaneous polarization.

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 by 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 concave condensing mirror is placed opposite the pyroelectric infrared sensor to focus the infrared rays emitted from the infrared source. The light is focused on an electric infrared sensor and devised to increase the S/N ratio.

However, as mentioned above, since the pyroelectric infrared sensor was placed opposite the condensing mirror, the entire device became large.
Furthermore, in order to use the condensing mirror, the mirror had to be formed into a concave reflective surface, making it difficult to manufacture.

For this reason, the present inventor has designed a semicircular mirror piece 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, as shown in FIG. A pyroelectric infrared detection device 10 is proposed, which is mounted perpendicularly to the upper surface 12 of the casing 11 and divided into two by a plane passing between the pyroelectric infrared detection elements 14a and 14b of the pyroelectric infrared sensor 14. did. The pyroelectric infrared detecting elements 14a and 14b of the pyroelectric infrared sensor 14 in this pyroelectric infrared detecting device 10 have polarized ends of the same polarity connected in series, as shown in the circuit diagram in FIG. A differential output is output from an emitter follower impedance conversion circuit using a field effect transistor (FET). Note that R1 and R2 are resistors. In FIG. 9, a pyroelectric infrared detection element 14a,
Although the same poles of the poles 14b are connected in series, they may be connected in parallel by connecting the poles of different polarities.

The operation in such a configuration is shown in the operation explanatory diagram in FIG. 10 and the pyroelectric infrared detection elements 14a and 14b in FIG. 11(a).
This will be explained using the output waveform diagram of the FET shown in FIG. 11(b).

When a detected object having a width ΔY emitting heat rays, that is, infrared rays, arrives at region (1) from a relatively far distance, the first focused infrared detecting element 14a is placed at a distance G from it. Infrared rays are incident on the second pyroelectric infrared detection element 14b, but due to the relationship between the distance to the object to be detected and the angle of incidence, the output from the first pyroelectric infrared element 14a is
The output is slightly larger than that of the pyroelectric infrared detection element 14b. Next, when the object to be detected is in region (2), that is, the first detection zone by shielding and reflection, the mirror piece 15 is placed in the first detection zone.
The second pyroelectric infrared detection element 14a has an effect of blocking the infrared rays, and the second pyroelectric infrared detection element 14b has an effect of shielding the infrared rays by adding it to the directly incident infrared rays and reflecting and projecting the infrared rays. to obtain a large differential output. Area (3)
Now, assuming that the object to be detected is a point, mirror piece 1
5, the infrared rays enter the first and second pyroelectric infrared detecting elements 14a and 14b and no differential output appears, but since the actual object to be detected has a width ΔY, As shown in the figure, initially the first pyroelectric infrared detection element 14a
The output of FET is larger, and as it moves toward the center in region (3), the FET output approaches 0, and as it approaches region (4), the FETff1 force increases in the negative direction. region(
4) That is, in the second detection zone by shielding and reflection, the mirror piece 15 shields infrared rays from the first pyroelectric infrared detection element 14a, and the second pyroelectric infrared detection element 1
4b, the infrared rays are added to the directly incident infrared rays, reflected and projected, and then incident, thereby obtaining a large differential output. In region (5), infrared rays are incident on both the first and second pyroelectric infrared detection elements 14a and 14b;
The output of the second pyroelectric infrared detection element 14b is larger than that of the first one. Note that since the detected object has a width ΔY, the area between areas (1) and (2) and between areas (4) and (5)
When moving between the two regions, the FET output changes while being influenced by each region.

The output of the FET based on the output of the first and second pyroelectric infrared detection elements 14a and 14b into which the infrared rays of the object to be detected are incident is guided to a bandpass filter, level detector, etc. (not shown), and
For example, it is connected to an alarm and activates the alarm.

In the above example, the mirror piece 15 was a concentric semicircle, but even if two fan-shaped mirror pieces 151 as shown in FIG. A plurality of sensors 151 can be arranged, for example, at equal intervals around the pyroelectric infrared sensor 14 as shown in FIG. 13, and in this case, passage of the object to be detected can be detected in a narrower area.

<Problems to be Solved by the Invention> In the case of having a semicircular or a plurality of fan-shaped mirror pieces as in the past, the detection zone is as shown in FIG. That is, with the pyroelectric infrared sensor 14 as the origin 0, the mirror piece 1
The direction in which 5 divides the pyroelectric infrared detection elements 14a and 14b is the Y-axis, and the direction perpendicular to the surface of the mirror piece 15 is the Y-axis.
If the Z-axis is the direction perpendicular to the installation surface of the pyroelectric infrared detection elements 14a and 14b, the first and second sensors are located on a plane orthogonal to the Z-axis a certain distance away from the pyroelectric infrared sensor 14.
As shown in FIG. 14, areas (2) and (4) as detection zones are at their narrowest distance ΔY when X=0, and as IX+ increases, that is, from the pyroelectric infrared detection device 10. The further away, the wider it becomes. Therefore, for example, when the pyroelectric infrared detection device 10 is mounted on the ceiling or wall,
There is a difference in detection between the case where the object to be detected moves along the Y-axis at X=0 and the case where the object moves along the line \1 shifted to X=X1 as follows. That is, for example,
areas (2) as first and second detection zones on the Y axis;
If the interval ΔY in (4) is made to match the size of the detected object, then
When moving in the Y direction, the FET output changes from area (2) to area (4) as the detection zone as the detected object moves.
As shown in Fig. 1(b), it is obtained without interruption. However, X
=X, when moving on the shifted line, as shown in the output waveform diagram in Fig.
Area (3-2) where the intermediate receiving output of (3) cannot be obtained between 4)
will occur.

In this way, when the pyroelectric infrared detector 10 is mounted on the ceiling or wall, continuous output can be obtained directly below or directly in front of the pyroelectric infrared detector 10;
The pyroelectric infrared device IO has a drawback in that the output level is low on both sides, resulting in areas that are not detected. This means that the detected object is
In an installation location where there is a possibility of movement in any direction, there may be cases where no detection occurs if the sensor moves without entering the detection zone.

Means for Solving the Problems> The present invention has been made to solve the above problems.
A pyroelectric infrared detection device having a mirror piece disposed perpendicular to the pyroelectric infrared sensor surface so that reflected light is projected onto the pyroelectric infrared sensor located at the center of the housing,
The pyroelectric infrared detection device is characterized in that the mirror piece has at least a square outer edge.

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

FIG. 1 is a perspective view showing an embodiment of a pyroelectric infrared detection device 1 of the present invention, in which a pyroelectric infrared sensor 2 is arranged in the center of a housing 3. Mirror pieces 4 are arranged so as to divide it into two parts. The pyroelectric infrared sensor 2 has a first pyroelectric infrared detection element 2a and a second pyroelectric infrared detection element 2b in each of the sections divided into two by the mirror piece 4. The reflected infrared rays are made incident. FIG. 2(a) shows the shape of the mirror piece 4 used in the present invention.

2(b), and FIG. 2(a) is formed by cutting out an area of approximately 1/4 circle 40a from one corner of a square plate 40 with side M2. In Fig. 2(b), the height is M2.
, a rectangular plate 41 with a width of 2M2 is formed by removing an approximately semicircular area 41b from the middle part of the lower side. The distance from the center of the substantially 1/4 circle and the substantially semicircle to one of the opposite corners is 5M2.

The present invention can be applied on an arbitrary line Y1 away from directly in front of the pyroelectric infrared detection device 1 or on a line Y2 at an angle of 45 degrees from the plane where the first and second pyroelectric infrared detection elements 2a and 2b are arranged. The width between areas (2) and (4) of the detection zone is made equal to the width ΔY on the Y axis.

That is, as in the conventional case shown in FIG.
When the outer edge of is fan-shaped or semicircular, the following equation holds true from the relationship shown in FIG. 3 showing shielding and reflection of the detection zone on the Y axis. However, G is the first and second pyroelectric infrared detection elements 2
The distance between a and 2b, M2 is the height of the mirror piece 4, L is the distance from the pyroelectric infrared sensor surface to the plane perpendicular to the predetermined Z axis,
ΔY is the interval width between regions (2) and (4) as detection zones.

G/2 ΔY/2 2L-M2 Than, -M2 ΔY=×G holds true.

Furthermore, as shown in the perspective view of the detection zone according to the embodiment of the present invention in FIG. 2
On the line Y2 at an angle of 45 degrees from the Z axis passing between
From the relationship shown in the figure, G/2 ΔY2/2 and penalty M2 5L-Tai M2, L-5M2 ΔY2=□\G holds true.

Therefore, the widths ΔY, ΔY between detection zones (2) and (4)
2 will be equal. Therefore, the shape of the mirror piece 4 is shown in Figure 2 (
If steps a) and (b) are followed, the pyroelectric infrared detector 1
The width between areas (2) and (4) of the detection zone on a plane perpendicular to the Z-axis, which is a certain distance @L from , can be made constant. That is, if the mirror piece 4 has an approximate square shape with the same vertical and horizontal dimensions, ΔY will be the same on the line Y2 having an angle of 45 degrees. If it is desired to make ΔY the same on any line Y1, the mirror piece 41 may have unequal vertical and horizontal dimensions, or may have an approximate rectangular shape.

Note that FIG. 6(a) shows a mirror piece with a small square 42a removed from one corner of a square plate 42 with side M2, and FIG. 6(b) shows one side of a plate 43 with short side M2 and long side 2M2. It is a mirror piece with a small rectangle 43a cut out from the long edge of the mirror. When such a mirror piece is used, the detection zone regions (2) and (4) can be made straight on the outside as shown in FIG.

<Effects of the Invention> The pyroelectric infrared detection device of the present invention has been described in detail above, and produces the following effects.

That is, since the outer end of the mirror piece that reflects infrared rays incident on the pyroelectric infrared cotton sensor is formed into a square shape, the detection zone can be changed by reflection from the mirror piece without changing the installation surface of the pyroelectric infrared detector. The interval can be made constant, and the heat source can be detected even on both sides away from the pyroelectric infrared detection device.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the pyroelectric infrared detection device of the present invention, FIGS. 2(a) and (b) are front views of mirror pieces used in the present invention, and FIGS. 3 and 5 are 4 is a perspective view illustrating the detection zone of the device shown in FIG. 1; FIGS. 6(a) and 6(b) are front views showing other embodiments of the mirror piece; 7 is a perspective view of a detection zone according to another embodiment of the present invention, FIGS. 8(a) and 8(b) are a plan view and front sectional view of a conventional pyroelectric infrared detection device, and FIG. 9 is a pyroelectric infrared detection device. Fig. 10 is an explanatory diagram of the operation of a conventional pyroelectric infrared detection device, Fig. 11 is an operation output waveform diagram, and Figs. 12 and 13 are conventional pyroelectric infrared detection devices. FIG. 14 is a perspective view showing another example of the detection device; FIG. 14 is a perspective view illustrating a conventional detection zone; FIGS.
) is an output waveform diagram. 1... Pyroelectric infrared detection device, 2... Pyroelectric infrared sensor, 2a, 2b... Pyroelectric infrared detection element, 3.
...Case, 4...Mirror piece. Patent applicant Murata Manufacturing Co., Ltd. Figure 1 Figure 2 (a) (b) Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 (a) (b) Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15

Claims (1)

[Scope of Claims] A pyroelectric infrared detection device having a mirror piece disposed perpendicular to the pyroelectric infrared sensor surface so that reflected light is projected onto the pyroelectric infrared sensor located at the center of the housing. . A pyroelectric infrared detection device, wherein at least an outer edge of the mirror piece is formed into a square shape.