JPH0499926A - Heat wave sensor - Google Patents

Abstract

PURPOSE:To make a reflecting mirror compact by providing a visual field controlling member which controls the visual field of a heat wave detecting element. CONSTITUTION:A visual field controlling member 6 is provided in the vicinity of a pyroelectric element 1 mounted on a substrate 1 so as to control the visual field of the element 1. The member 6 may be a flat plate, having the height set so that only the far infrared rays from a reflecting mirror are allowed to enter the element, and the far infrared rays from the different position can be shut. In this structure, if an angle phi of the reflecting mirror is 30 deg., the heat wave sensor can be made compact in size.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a heat ray sensor.

[Prior Art] Conventionally, a heat ray sensor including a pyroelectric element and a reflecting mirror is known as a device for detecting the presence or absence of a human being, such as detecting the presence or absence of a person in a room. An example of its configuration is shown in FIG.

In FIG. 2, far infrared rays 3 emitted from a human being are reflected by a reflecting mirror 2 and incident on a pyroelectric element 1 placed at the focal point of the reflecting mirror 2. The pyroelectric element 1 converts the incident far infrared rays into voltage and outputs it to a signal processing circuit (not shown).

[Problems to be Solved by the Invention] In the conventional heat ray sensor, the reflecting mirror 2 is arranged at an angle of about 50'' on both sides from the center of the pyroelectric element 1. That is, in FIG. 2, φ= In such a configuration, the reflector 2 covers most of the field of view of the pyroelectric element 1, as can be understood from the directivity characteristics of a general pyroelectric element shown in FIG. Therefore, it is possible to effectively detect human presence and absence.

It is effective to arrange the reflector 2 at a wide angle in this way, and even if far infrared rays directly enter the pyroelectric element 1 from a position away from the reflector 2, the directivity at that angle is very low. Although the possibility of causing a false alarm is very low, it has been extremely difficult to achieve the miniaturization of the heat ray sensor, which has been strongly desired in recent years, because the reflecting mirror 2 has to be large. .

On the other hand, for example, the angle φ of the reflecting mirror 2 in FIG.
If the angle is changed from about 30° to about 30°, the reflector 2 can be made smaller and the entire heat ray sensor can be made smaller, but in this case, a large sensitivity can also be achieved at positions outside the reflector 2. As a result, as shown by 4 in Figure 2, far infrared rays incident from outside the originally required field of view, that is, the field of view determined by the angle of the reflector 2, are also detected, resulting in false alarms. There were cases where this occurred.

The present invention solves the above-mentioned problems, and aims to provide a heat ray sensor that can be miniaturized and does not malfunction.

[Means for Solving the Problems] In order to achieve the above object, the heat ray sensor of the present invention has the following features:
The heat ray sensor includes a reflecting mirror and a heat ray detection element that detects heat rays, and is characterized by comprising a field-of-view limiting member that limits the field of view of the heat ray detection element.

[Operations and Effects of the Invention] In the present invention, in a heat ray sensor that includes a reflecting mirror and a heat ray detection element that detects heat rays, a field of view limiting member that limits the field of view of the heat ray detection element is provided. Therefore, only the heat rays reflected by the reflecting mirror are incident on the heat ray detection element, so that the heat rays from outside the desired viewing angle are not detected and false alarms are not generated.

As described above, according to the present invention, the reflecting mirror can be easily downsized.

[Example code] Examples will be described below with reference to the drawings.

FIG. 1(a) is a diagram showing the configuration of an embodiment of a heat ray sensor according to the present invention, in which a pyroelectric element 1 attached to a substrate 5 is shown.
A field-of-view limiting member 6 for restricting the field of view of the pyroelectric element 1 is arranged near the pyroelectric element 1 . The field of view limiting member 6 may be a flat plate, or may be curved along the outer shape of the pyroelectric element 1. In addition, the height of the viewing field limiting member 6 is determined by the reflector (see Fig. 1(a)).
It is set at a height that allows only far infrared rays from sources (not shown) to enter, and blocks far infrared rays from other locations.

In the configuration shown in FIG. 1(a), now the angle of the reflecting mirror is φ
=30°, the heat ray sensor can be downsized as described above. The height of the viewing field limiting member 6 is
As shown in the figure, only the far infrared rays from the reflecting mirror are allowed to enter the pyroelectric element 1. - This makes it possible to effectively block far infrared rays from outside the predetermined field of view as shown by 7 in the figure.

FIG. 1(b) is a diagram showing another example of the configuration of the visual field limiting member, in which the visual field limiting member 8 is formed into a ring shape of a suitable resin such as rubber, and has a convex shape on at least a part thereof for limiting the visual field. I am doing part 9. Therefore, the field of view limiting member 8 is
As shown in Figure (C), the visibility can be effectively restricted by attaching the convex part 9 to the pyroelectric element 1 in such a way as to block far infrared rays from a position other than the reflecting mirror, as shown by 10 in the figure. It can be carried out. Note that, as shown in FIG. 1(b), the field of view limiting member 8 is not a complete ring but has a gap 11.
This allows attachment to various pyroelectric elements having different outer diameters.

FIG. 1(d) is a diagram showing another example of the configuration of the visual field limiting member, in which a flange 14 is formed on the shield member 13, and the visual field is limited by the flange 14. That is, in a hot wire sensor, in order to prevent electromagnetic wave interference from the outside, shield members 12 and 13 are usually arranged below and above the substrate 5 to surround the pyroelectric element 1. A part of the shield member 13 is cut and raised to form a flange 14, thereby blocking far infrared rays from outside the desired field of view as shown by 15 in the figure.

FIG. 1(e) is a diagram showing the configuration of yet another embodiment,
Light shielding members 1 are provided at both ends of the reflecting mirror 2 to limit the field of view.
7.18 to limit the field of view. The mounting angle and size of the light shielding members 17 and 18 are such that a desired viewing angle is obtained, all reflected light from the reflecting mirror 2 enters the pyroelectric element 1, and far infrared rays from outside the viewing angle are effective. It is set so that it can block light.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be modified in various ways. It's a good thing. Therefore, in the above embodiment, a pyroelectric element was used as the heat ray detection element, but
The present invention can also be applied to heat ray sensors using other heat ray detection elements, and although the above embodiment detects far infrared rays, the present invention can also be applied to near infrared rays, infrared rays, etc. The present invention can be similarly applied to a heat ray sensor that detects light at the earth's wavelength.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a heat ray sensor according to the present invention, FIG. 2 is a diagram showing an example of the configuration of a conventional heat ray sensor, and FIG. 3 is a diagram for explaining the directional characteristics of a pyroelectric element. . 1... Pyroelectric element, 2... Reflector, 5... Substrate, 6
．． 8.14.17.18...Visual field limiting member. Applicant Atsumi Electric Co., Ltd.

Claims (1)

[Claims] (1) A heat ray sensor comprising a reflecting mirror and a heat ray detection element for detecting heat rays, characterized in that the heat ray sensor includes a field of view limiting member that limits the field of view of the heat ray detection element.