JPH0933663A - Hot-wire sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a static body by using a pyroelectric element. SOLUTION: A circuit board 2 mounting a pyroelectric element 3 is held inside a case 1. A Fresnel lens 5 for setting a warning zone is formed on a cover 4 and rotated in reciprocation in such a prescribed angular range as shown by an arrow 10 by a driving device 9 comprising a motor and others. In the case when a static body is present in a visual field, the warning zone and the static body move relatively, since the Fresnel lens 5 being an optical system for setting the warning zone is rotated in reciprocation, and consequently the static body can be detected.

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. 2A is a diagram showing a schematic configuration example thereof, in which a chopper 12 is arranged in front of the pyroelectric element 11, and a window 13 is opened in a part of the chopper 12. The chopper 12 is rotated by the motor 14 at a predetermined speed. The optical system is omitted in FIG. 2A.

Therefore, for example, if the pyroelectric element 11 receives heat rays from a predetermined visual field through the window 13 during the period indicated by A in FIG. 2B, the pyroelectric element 11 during the period indicated by B in FIG. It will be masked by 12.

Since the chopper 12 is substantially at the same temperature as the surrounding 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, so the output voltage of the pyroelectric element 11 is very small. However, when a stationary body is present in the visual field, the visual field temperature is the environmental temperature. Since the temperature is different from the temperature, the temperature change between the environmental temperature and the field-of-view temperature by the chopper 12 causes t in FIG.
_{At 1} , t ₂ , t ₃ , t ₄ , t ₅ , and t ₆ , a significant output voltage is obtained from the pyroelectric element 11.

Therefore, by comparing the output voltage of the pyroelectric element 11 with the threshold value, it is possible to detect whether or not there is a stationary body.

In FIG. 2B, t ₁ , t ₃ and t ₅ are from the state where the pyroelectric element 11 is masked by the chopper 12 to the window 1.
It is time to move to the state of vision through 3
Obviously, t ₂ , t ₄ , t _{6 in} FIG. 2B is the time when the pyroelectric element 11 transitions from being directed into the field of view through the window 13 to being masked by the chopper 12.

In addition, in the structure of FIG. 2A, the detection of the moving body is performed during the period indicated by A in FIG.
It is clear that this can be done during the period when it is directed to the field of view through.

[0012]

However, as shown in FIG.
In the method using the mechanical chopper shown in FIG.
In general, the temperature of the field of view as viewed through the window 13 is different from that of the background. Therefore, the temperature difference appears in the output signal of the pyroelectric element 11 as noise, 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, and a drive for moving the optical system. And means.

[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 drive means moves the optical system. Here, a reciprocating rotary motion or the like may be performed as the motion of the optical system. Also,
The optical system may be composed of a reflecting mirror or Fresnel lens.

Therefore, in this heat ray sensor, the movement of the optical system moves the warning zone set by the optical system. Therefore, when there is a stationary body, the heat ray sensor moves relative to the stationary body. Since the stationary body appears to move from the heat ray sensor, the stationary body can be detected.

[0018]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a schematic sectional view showing the structure of an embodiment of a heat ray sensor according to the present invention, in which 1 is a case, 2 is a circuit board, 3 is a pyroelectric element, 4 is a cover, and 5 is a Fresnel lens. ,
6 is a thick part, 7 is a collar part, 8 is a roller, 9 is a drive device, R
Indicates a roller.

Inside the case 1, a circuit board 2 and a motor 9 are provided.
Is stored. Then, the pyroelectric element 3 is provided on the circuit board 2.
Is installed. The number of pyroelectric elements 11 may be one,
There may be more than one.

On the cover 4, one or a plurality of Fresnel lenses 5 are formed in order to set a warning zone. The number of Fresnel lenses 5 to be formed can be arbitrarily determined according to the warning zone to be set.

A thick portion 6 is formed on the end of the cover 4, and a flange portion 7 is formed on the thick portion 6 toward the outside.

Inside the case 1, rollers R are provided in pairs at predetermined positions. The number of the pairs of rollers R provided is arbitrary. The flange 7 of the cover 4 is sandwiched and supported by the pair of rollers R.

A roller 8 is in contact with the inside of the thick portion 6 of the cover 4, and the roller 8 is rotated by a driving device 9 such as a motor. The driving device 9 is for reciprocally rotating the cover 4 on which the Fresnel lens 5 is formed over a predetermined angle range as indicated by an arrow 10 in the figure. It is obvious that such a driving device 9 can be configured by using a stepping motor or the like.

As described above, in this heat ray sensor, the cover 4 is used.
Since the optical system composed of the Fresnel lens 5 formed in the above-described section makes a reciprocating rotary motion, even if there is a stationary body, if the warning zone set by the Fresnel lens 5 crosses the stationary body, Since the stationary body moves relative to the stationary body, the stationary body can be detected. It is also clear that this configuration can detect a moving body.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment 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, the optical system for setting the warning zone need only be driven so as to make some movement. is there. Of course, the movement of the optical system is not limited to the reciprocating rotary movement described above, and needless to say, may be other movement.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining a conventional stationary object detection method using a chopper.

[Explanation of symbols]

1 ... Case, 2 ... Circuit board, 3 ... Pyroelectric element, 4 ... Cover, 5 ... Fresnel lens, 6 ... Thick part, 7 ... Collar part, 8 ...
Roller, 9 ... Driving device, R ... Roller.

Claims (1)

[Claims] 1. A heat ray sensor comprising at least one pyroelectric element, an optical system for setting a warning zone, and a drive means for moving the optical system.