JPH095156A - Heat ray sensor - Google Patents

Abstract

PURPOSE: To detect a static object using a pyroelectric element. CONSTITUTION: A cover 12 is mounted on a base 10 to cover a pyroelectric element 11 and a Fresnel lens 13 is formed on the cover 12 to set a precaution zone. A sensor section comprising the base 10, a pyroelectric element 11 and the cover 12 is connected to a driver 14. The driver 14 drives the sensor section to reciprocatively rotate on a specified rotary shaft over a specified range of angle as indicated by the arrow 15. With such an arrangement, the pyroelectric element 11 and the Fresnel lens 13 move integrally and when a static object exists within a visual field, a heat ray sensor and the static object move relatively thereby enabling detecting of the static object.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat ray sensor capable of detecting a stationary object.

[0002]

2. Description of the Related Art A so-called heat ray sensor, which detects whether or not a person is present within the field of view by detecting the heat ray radiated from the human body, penetrates into a door switch or a security system for controlling the opening and closing of an automatic door. Although widely used for detecting a person, a pyroelectric element has been widely used in the past as an infrared light receiving element used for such a heat ray sensor. It should be noted that here, the pyroelectric element means an element having a pyroelectric effect, such as TGS, PZT, and lead titanate (PbT).
iO ₃ ) and the like are known.

However, since the pyroelectric element detects the amount of change in the heat ray received, it can be detected when a human is moving (hereinafter referred to as a moving body), but it remains stationary. There is a problem that a human being (hereinafter referred to as a stationary body) cannot be detected.

However, in detecting a door switch or an intruder, it is required to be able to detect even when a person is stationary. For example, considering the case of using it for a door switch, a person may go near the door and stop, but in such a case it can be detected when moving and the door will open, but it will stop Since the door cannot be detected, the door will be closed, and there is a risk that a person will be caught in the door. In addition, considering the case of using for intruder detection, it is obvious that a security alarm system is insufficient if it cannot detect when an intruder stops.

On the other hand, there is known a method of detecting not only a moving body but also a stationary body by combining a pyroelectric element and a mechanical chopper.

FIG. 4A is a diagram showing a schematic configuration example thereof, in which a chopper 2 is arranged in front of the pyroelectric element 1,
A window 3 is opened in a part of the chopper 2. The chopper 2 is rotated by the motor 4 at a predetermined speed. The optical system is omitted in FIG. 4A.

Therefore, for example, assuming that the pyroelectric element 1 receives heat rays from a predetermined visual field through the window 3 in the period shown by A in FIG. 4B, the pyroelectric element 1 is chopper by the period shown by B in FIG. 4B. It will be masked by 2.

Since the chopper 2 is at approximately the same temperature as the ambient environment (hereinafter referred to as the ambient temperature),
When no human is present in the visual field, the visual field temperature is substantially equal to the environmental temperature, and therefore the output voltage of the pyroelectric element 1 is very small. However, when a stationary body is present in the visual field, the visual field temperature is the environmental temperature. Since it is different from the temperature, the temperature change between the environmental temperature and the visual field temperature by the chopper 2 causes t ₁ , t in FIG. 4B to change.
_When indicated by ₂ , t ₃ , t ₄ , t ₅ , t ₆ , a significant output voltage is obtained from the pyroelectric element 1.

Therefore, by comparing the output voltage of the pyroelectric element 1 with the threshold value, it is possible to detect whether or not there is a stationary body.

Note that t ₁ , t ₃ , and t _{5 in} FIG. 4B are when the pyroelectric element 1 is changed from being masked by the chopper 2 to being directed to the visual field through the window 3, as shown in FIG. 4B.
It is clear that t ₂ , t ₄ and t ₆ of FIG. 2 are the time when the pyroelectric element 1 is shifted from the state in which the pyroelectric element 1 is directed to the visual field through the window 3 to the state in which it is masked by the chopper 2.

Further, in the configuration of FIG. 4A, it is apparent that the detection of the moving body can be performed during the period indicated by A in FIG. 4B, that is, the period in which the pyroelectric element 1 is directed to the visual field through the window 3. is there.

[0012]

However, as shown in FIG.
In the method using the mechanical chopper shown in FIG.
And the temperature of the background of the field of view seen through the window 3 are different from each other. Therefore, the temperature difference appears as noise in the output signal of the pyroelectric element 1 and the necessary S / N ratio cannot be secured. is there.

In order to prevent this, it is conceivable to control the chopper temperature or perform arithmetic processing on the signals to correct the temperature difference, but the device becomes large and expensive. Is.

The present invention is to solve the above-mentioned problems, and in a heat ray sensor using a pyroelectric element, it is possible to detect not only a moving body but also a stationary body without using a mechanical chopper. It is an object of the present invention to provide a heat ray sensor capable of performing the above.

[0015]

In order to achieve the above object, the heat ray sensor of the present invention comprises at least one pyroelectric element, an optical system for setting a warning zone, a pyroelectric element and an optical system. And driving means for moving relative to the stationary body as a unit.

[0016]

This heat ray sensor comprises at least one pyroelectric element and an optical system for setting the warning zone, and further comprises a driving means. This driving means integrally moves the pyroelectric element and the optical system with respect to the stationary body. Here, as the relative movement, a reciprocating rotary movement, a reciprocating swing movement, or the like may be performed. The optical system may be composed of a reflecting mirror or Fresnel lens.

Therefore, when there is a stationary body, the heat ray sensor moves relative to the stationary body, so that the stationary body seems to be moving from the heat ray sensor, and the stationary body is also detected. It is possible to

Further, according to this structure, unlike the conventional method using the chopper, noise due to the temperature difference between the chopper and the background is not generated, so that a signal with a good S / N can be obtained. .

[0019]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a sectional view showing the configuration of a first embodiment of a heat ray sensor according to the present invention. In the figure, 10 is a base, 11 is a pyroelectric element, 12 is a cover, 13 is a Fresnel lens, and 14 is a driving device. Indicates.

Although a circuit board is housed in the base 10, it is omitted in FIG. The pyroelectric element 11 is attached to the base 10. The number of the pyroelectric elements 11 may be one or plural.

A cover 12 is attached to the base 10 so as to cover the pyroelectric element 11, and one or a plurality of Fresnel lenses 13 are formed on the cover 12 to set a warning zone. When a plurality of pyroelectric elements 11 are arranged, it is desirable to provide one Fresnel lens for each pyroelectric element.

The base 10, the pyroelectric element 11, and the cover 12 which are integrated (hereinafter referred to as a sensor portion) are connected to the driving device 14. The drive unit 14 reciprocally rotates the sensor unit about a predetermined rotation axis over a predetermined angle range as indicated by an arrow 15. Such a driving device 14 can be configured by using a stepping motor or the like.

As described above, this heat ray sensor has the pyroelectric element 1
1 and the optical system including the Fresnel lens 13 formed on the cover 12 move integrally, so that when there is a stationary body in the field of view of the heat ray sensor, the heat ray sensor and the stationary body are relatively moved to each other. This stationary body can be detected. Moreover, it is natural that the moving object can be detected by this configuration.

The first embodiment has been described above.
Next, a second embodiment will be described with reference to FIG. In the first embodiment, the base 10 and the pyroelectric element 1 are used.
1 and the cover 12 are integrally reciprocally rotated, the second embodiment is different from the first embodiment in that only the pyroelectric element and the optical system are integrally reciprocally rotated.
Is different from the embodiment. In FIG. 2, the same components as those shown in FIG. 1 are designated by the same reference numerals.

In FIG. 2, the circuit board 1 is provided in the case 16.
7 is mounted on the circuit board 17
Is installed. A turntable 19 is attached to the drive device 18, and the pyroelectric element 11 is mounted on the turntable 19. A cover 12 having a Fresnel lens 13 formed thereon is attached to the turntable 19 so as to cover the pyroelectric element 11.

According to this structure, the pyroelectric element 11 and the Fresnel lens 13, which is an optical system, reciprocally rotate about the rotation axis of the turntable 19 over a predetermined angle range as indicated by an arrow 15. Therefore, not only the moving body but also the stationary body can be detected from the above description.

The heat ray sensor having the configuration shown in FIGS. 1 and 2 is suitable for mounting on the ceiling in the center of the place where the intruder is detected.

Next, a third embodiment will be described with reference to FIG. 3A is a cross-sectional view of the heat ray sensor as seen from the front, and FIG. 3B is a cross-sectional view as seen from the direction of arrow 22 in FIG. 3A. 3A and 3B, the same components as those shown in FIG. 1 are designated by the same reference numerals.

In FIG. 3A, the sensor unit is a drive unit 20.
Are connected by a shaft 21. This drive device 20
Is configured to reciprocate the sensor unit and make a motion of swinging the head (hereinafter referred to as a swing motion) as shown by an arrow 23 in FIG. 3B. It is obvious that such a driving device can be composed of a motor or the like.

According to this structure, since the pyroelectric element 11 and the optical system including the Fresnel lens 13 formed on the cover 12 move integrally, there is a stationary body in the visual field of the heat ray sensor. In this case, the heat ray sensor and the stationary body move relative to each other, and the stationary body can be detected. It is also clear that this configuration can detect a moving body.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications can be made. For example, in the above embodiment, the Fresnel lens is used as the optical system for setting the warning zone, but it goes without saying that the reflecting mirror used in the conventional heat ray sensor can also be used.

Further, the structures shown in the above embodiments are merely examples, and in the present invention, in short, the pyroelectric element and the optical system for setting the warning zone are integrated with respect to the stationary body. It suffices if it is provided with a structure for performing some relative movement.

[Brief description of drawings]

FIG. 1 is a sectional view showing the configuration of a first embodiment of a heat ray sensor according to the present invention.

FIG. 2 is a sectional view showing a configuration of a second embodiment of the heat ray sensor according to the present invention.

FIG. 3 is a cross-sectional view showing the configuration of a third embodiment of the heat ray sensor according to the present invention.

FIG. 4 is a diagram for explaining a conventional stationary object detection method using a chopper.

[Explanation of Codes] 10 ... Base, 11 ... Pyroelectric element, 12 ... Cover, 13 ...
Fresnel lens, 14 ... Drive device.

Claims (1)

[Claims] 1. At least one pyroelectric element, an optical system for setting a warning zone, and a driving means for integrally moving the pyroelectric element and the optical system with respect to a stationary body. And a heat ray sensor.