JPH0455258B2 - - Google Patents

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, and the mirror had to be formed into a concave reflective surface in order to function as a condensing mirror. It was not easy to manufacture.

For this reason, the inventor created a semicircular mirror piece,
As shown in FIG. 8, the pyroelectric infrared rays are perpendicular to the upper surface 12 of the casing 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 casing 11. Pyroelectric infrared detecting device 1 installed so as to be divided into two by a plane passing between pyroelectric infrared forming elements 14a and 14b of sensor 14
I suggested 0. 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. 9th
In the figure, the same polarity of the pyroelectric infrared detection elements 14a and 14b are connected in series, but they may be connected in parallel with different polarization ends.

The operation in such a configuration is illustrated in the operation explanatory diagram in FIG. 10 and the pyroelectric infrared detection element 14 in FIG. 11a.
This will be explained using the output waveform diagrams of FETs a and 14b and the FET output waveform diagram of FIG. 11b.

When a detected object with a width ΔY that emits heat rays or infrared rays arrives at area (1) from a relatively far distance,
Infrared rays are incident on the first pyroelectric infrared detection element 14a and the second pyroelectric infrared detection element 14b arranged at a distance G from the first pyroelectric infrared detection element 14a, but the relationship between the distance to the object to be detected and the angle of incidence Therefore, the output from the first pyroelectric infrared element 14a is slightly larger than the output from the second pyroelectric infrared detection element 14b.
Next, when the object to be detected is in region (2), that is, the first detection zone due to shielding and reflection, the mirror piece 15 adds the amount of infrared rays directly incident to the first pyroelectric infrared detection element 14a, and is reflected, projected, and incident on the second pyroelectric infrared detection element 14.
For b, it acts to shield infrared rays and obtain a large differential output. In region (3), if the object to be detected is assumed to be a point, the first and second pyroelectric infrared detection elements 14a,
Although infrared rays are incident on 14b and no differential output appears, since the actual object to be detected has a width ΔY, initially the output of the first pyroelectric infrared detection element 14a is smaller than that of the first pyroelectric infrared detection element 14a as shown in the figure. The FET output approaches 0 as it moves toward the center in region (3).
Further approaching region (4), the FET output increases in the negative direction. In region (4), that is, the second detection zone by shielding and reflection, the mirror piece 15 shields infrared rays from the first pyroelectric infrared detecting element 14a, and blocks infrared rays from the second pyroelectric infrared detecting element 14b. In this case, the infrared rays are added to the directly incident infrared rays, and the infrared rays are reflected, 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, but the output of the second pyroelectric infrared detection element 14b is greater than that of the first. Note that since the object to be detected has a width ΔY, when moving between areas (1) and (2) and between areas (4) and (5), the FET output is affected by each area. However, it is changing.

Based on the outputs 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.
The output of the FET is guided to a bandpass filter, level detector, etc. (not shown), and is connected to, for example, an alarm to activate the alarm.

In the above example, the mirror piece 15 was a concentric semicircle, but the fan-shaped mirror piece 151 as shown in FIG.
The same operation occurs even when two mirror pieces 151 are mounted perpendicularly to the upper surface 12, and a plurality of mirror pieces 151 can be arranged, for example, at equal intervals around the pyroelectric infrared sensor 14 as shown in FIG. In this case, the 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 direction in which the mirror piece 15 divides between the pyroelectric infrared detecting elements 14a and 14b is the X axis, the direction perpendicular to the surface of the mirror piece 15 is the Y axis, and the focus. If the Z-axis is the direction perpendicular to the installation surface of the electro-conductive infrared detecting elements 14a and 14b, the first and second signals on a plane perpendicular to the Z-axis, which is a certain distance L away from the pyroelectric infrared sensor 14, are As shown in FIG. 14, the areas (2) and (4) as detection zones are at their narrowest interval ΔY at X=0, and as |X| becomes larger, that is, the pyroelectric infrared detector 10 The further away you are, the wider it becomes. Therefore, for example, the pyroelectric infrared detection device 1
0 is mounted on the ceiling or wall, the distance L is the same as when the detected object moves on the Y axis at X=0, and
There is a difference in detection as follows when moving on the line _Y1 shifted to = _X1 . That is, for example, if the interval ΔY between areas (2) and (4) as the first and second detection zones on the Y axis matches the size of the detected object, when moving in the Y direction, the detection zone As the detected object moves from area (2) to (4) as
The FET output can be obtained continuously as shown in FIG. 11b. However, when moving on a line that is shifted by X ₌ This results in an area (3-2) that cannot be obtained.

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, but if the pyroelectric infrared detector 10 is mounted on both sides of the The disadvantage is that the output level is low and there are areas that are not detected. This is because in an installation location where there is a possibility that the object to be detected may move in the X direction, if the object moves without entering the detection zone, it may not be detected at all.

<Means for Solving the Problems> The present invention has been made in order to solve the above problems. The pyroelectric infrared detecting device has a mirror piece disposed perpendicularly to a surface of the infrared sensor, 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, and a pyroelectric infrared sensor 2.
is arranged in the center of the housing 3, and a mirror piece 4 is arranged so as to divide the pyroelectric infrared sensor 2 into two. 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. and,
The shape of the mirror piece 4 used in the present invention is shown in Figures 2a and b.
2a is a square plate 40 with one side of _M2 , and an area approximately 1/4 circle 40a is cut out from one corner of the square plate 40. Figure 2b shows the height
A rectangular plate 41 with a width of 2M ₂ and a width of 2M ₂ is formed by removing a substantially semicircular area 41b from the middle part of the lower side. The distance from the center of the approximately 1/4 circle and the approximately semicircle to one of the opposite corners is √2M ₂ .

The present invention is directed to an arbitrary line _Y1 that is away from directly in front of the pyroelectric infrared detection device 1, or a line Y2 that is at an angle of 45 degrees from the plane where the first and second pyroelectric infrared detection elements 2a and _2b are arranged. on top the area of the detection zone (2),
The width between (4) is made equal to the width ΔY on the Y axis.

That is, when the outer edge of the mirror piece 15 is fan-shaped or semicircular as in the conventional case shown in FIG. 14, the following equation is established based on the relationship shown in FIG. 3 showing shielding and reflection of the detection zone on the Y-axis. do. However, G is the distance between the first and second pyroelectric infrared detection elements 2a and 2b,
M ₂ is the height of the mirror piece 4, L is the distance from the pyroelectric infrared sensor surface to the plane perpendicular to the specified Z axis, ΔY
is the interval width between areas (2) and (4) as detection zones.

From G/2/M ₂ =ΔY/2/L−M ₂ , ΔY=L−M ₂ /M ₂ ×G holds true.

Furthermore, as shown in the perspective view of the detection zone according to the embodiment of the present invention in FIG. Angle from the Z axis passing between 2b
On the 45 degree line Y ₂ , from the relationship shown in Figure 5, G/2/√2M ₂ = ΔY ₂ /2/√2L−√2M ₂ From ΔY ₂ =√2L−√2M ₂ /√2M ₂ ×G holds true.

Therefore, the width ΔY between detection zones (2) and (4), ΔY ₂
are equal. Therefore, the shape of the mirror piece 4 is changed to the second shape.
If it is done as shown in Figures a and b, the width between the detection zone areas (2) and (4) on the plane perpendicular to the Z-axis, which is a certain distance L from the pyroelectric infrared detector 1, will be constant. can do. In other words, if the mirror piece 4 has an approximate square shape with the same vertical and horizontal dimensions, a line Y ₂ with an angle of 45 degrees
ΔY will be the same as above. ΔY on any line Y ₁
If the mirror pieces 41 are desired to be the same, the mirror pieces 41 may have unequal vertical and horizontal dimensions, or may be approximately rectangular.

In addition, FIG. 6a shows a mirror piece with a small square 42a removed from one corner of a square plate 42 with one side _M2 , and FIG. 6b shows a plate 43 with a short side _M2 and a long side _2M2.
It is a mirror piece with a small rectangle 43a cut out from one long edge of the mirror. When such a mirror piece is used, the detection zone regions (2) and (4) can be made linear 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 the infrared rays incident on the pyroelectric infrared sensor is formed into a square shape,
It is possible to maintain a constant spacing between the detection zones due to the reflection of the mirror piece without changing the installation surface of the pyroelectric infrared detector, and it is possible to detect heat sources even on both sides far from the pyroelectric infrared detector. can.

[Brief explanation of drawings]

Figure 1 is a perspective view of an embodiment of the pyroelectric infrared detector of the present invention, Figures 2a and b are front views of mirror pieces used in the present invention, and Figures 3 and 5 are the intervals between detection zones. FIG. 4 is a perspective view illustrating the detection zone of the device shown in FIG. 1, FIGS. 6 a and b are front views showing other embodiments of the mirror piece, and FIG. A perspective view of a detection zone according to an embodiment; FIGS. 8a and 8b are a plan view and a front sectional view of a conventional pyroelectric infrared detector; FIG. 9 is an electric circuit applied to the pyroelectric infrared detector; 11 is an operation output waveform diagram, FIGS. 12 and 13 are perspective views showing other examples of the conventional pyroelectric infrared detector, and FIG. Figure 14 is a perspective view illustrating a conventional detection zone;
Figures a and b are output waveform diagrams. DESCRIPTION OF SYMBOLS 1... Pyroelectric infrared detection device, 2... Pyroelectric infrared sensor, 2a, 2b... Pyroelectric infrared detection element, 3... Housing, 4... Mirror piece.

Claims (1)

[Claims] 1. A pyroelectric infrared detection device having a mirror piece arranged perpendicularly 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 the mirror piece has at least a square outer edge.