JPH023234B2 - - Google Patents

Description

Detailed Description of the Invention This invention prevents equipment malfunctions caused by weather conditions, especially frost adhering to the surface of the transparent cover in front of the optical system, and is an outdoor installation type with a simple structure and excellent appearance. This invention relates to an infrared security alarm device.

Radiation cooling, which is used in the meteorological field, refers to far-infrared rays being emitted from an object toward the sky to lower the temperature of the object. In the case of an outdoor infrared security alarm system, if frost forms on the transparent cover surface in front of the optical system of the emitter or receiver due to radiation cooling at night, the amount of infrared rays emitted from the emitter or incident on the receiver will decrease. It is known that the attenuation factor is reduced to less than 1/100 compared to the case where there is no attenuation factor at all. An infrared security device uses a receiver to detect near-infrared rays with a wavelength of approximately 0.91 to 0.94 μm emitted from a projector, and issues an alarm when an intruder blocks the infrared rays. Therefore, if the amount of infrared rays incident on the light receiver falls below a certain level, the alarm device will be activated, so an extreme decrease in the amount of projected light or the amount of incident light due to the accumulation of frost is a serious problem.

Therefore, in conventional equipment, in order to prevent frost from adhering to the surface of the transparent cover due to radiation cooling, a hood is installed above the emitter and the receiver to prevent far-infrared rays from being radiated toward the sky from the surface of the transparent cover. are doing. However, although this far-infrared ray shielding hood is useful for preventing frost build-up due to radiant cooling, it seriously impairs the aesthetic appearance. Furthermore, if an optical system of a projector or a light receiver is made to be rotatable, a hood having an area corresponding to the range of rotation is required, but the aesthetic appearance of the hood is also significantly impaired. Therefore, in conventional devices, the emission direction of the projector or the direction of incidence of the light receiver is generally limited to the front direction, but there is a possibility that a third party may detect the security area. I didn't like it.

On the other hand, the factor of attenuating the amount of infrared rays due to weather conditions is not limited to frost; the amount of infrared rays is also significantly attenuated by rain, snow, fog, etc. compared to a clear day. Therefore, infrared security alarm systems are provided with a sensitivity margin so that they can operate normally even under the worst expected weather conditions. ~100 times.

The present invention has been made with attention to this sensitivity margin. For example, assuming a device with a sensitivity margin set to 100 times, even if frost adheres to the surface of the light-transmitting cover, compared to a clear and dry day, hand
If 1/100th the amount of light is incident on the light receiving element in the light receiver, the device can operate normally. On the other hand, the weather conditions in which frost occurs are limited to times when radiative cooling is severe, that is, when there is no wind and clear skies, so other attenuation factors for infrared rays in the optical path, such as rain, snow, fog, etc., may attenuate infrared rays. There isn't. Therefore, it can be seen that it is sufficient to secure an area on the surface of the light-transmitting cover that is free from frost so that at least 1/100th the amount of light enters the light-receiving element compared to when the sky is clear and dry. The present invention has been made with this point in mind, and will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a conventional infrared security alarm system, in which a far-infrared shielding hood 3 is used to block far-infrared rays from being radiated toward the sky from the surface of a transparent cover 2 of a projector or receiver 1. It is installed above the projector or receiver 1. Although this far-infrared shielding hood 3 is useful for preventing frost from adhering, it has caused a significant loss of aesthetic appearance.

The present invention includes a projector that emits infrared rays, a receiver that receives the infrared beam emitted from the projector,
The emitter and the receiver are composed of a light emitting element or a light receiving element, an optical system interposed between the infrared beam and the light emitting element or the light receiving element, and an alarm device connected to the infrared beam. It is composed of a transparent cover that allows the light to pass through.

FIG. 2 is a sectional view showing an embodiment of the light receiver according to the present invention. The front side of the condensing mirror 4 is covered with a transparent cover 2 that transmits infrared rays, and a small opening 5 is provided in the transparent cover 2. This opening 5 is located within a region through which the infrared beam focused by the condensing mirror 4 passes, and its area may be approximately 1/100 or more of the cross-sectional area of the infrared beam.

Since the light-transmitting cover 2 is provided with the small-area opening 5, even if frost adheres to the surface of the light-transmitting cover 2, it will pass through the opening 5 to the light-receiving element 6 such as a phototransistor. Since the above amount of light is incident, the device can operate normally. Note that since the air inside the light receiver 1 serves as a heat insulator, there is little risk of frost adhering to the surfaces of the condensing mirror 4 and the like inside the receiver.

Furthermore, the air inside the container is constantly flowing due to convection, and there is some communication with the outside air through the opening 5. For this reason, air movement occurs around the periphery of the opening 5 and heat is supplied from the moving air, making it difficult for frost to adhere to the periphery of the opening 5. Therefore, the effective field of view is larger than the opening area of the opening 5. It also has the advantage of being secured.

FIG. 3 is a diagram showing another embodiment of the present invention in which the optical system is rotatable, and FIG. 4 is a sectional view thereof. For example, to explain a light receiver as an example, the light-transmitting cover 2 on the front surface of the light collecting mirror 4 and the support member 7 of the light collecting mirror 4 are configured separately, and the support member 7 is suspended and supported on the upper part of the main body of the light receiver 1. and can be rotated horizontally. Opening 5
A plurality of apertures 5 are arranged in series along the rotating direction of the condensing mirror 4, and the area and number of apertures 5 are appropriately set according to the sensitivity margin or the state of the warning area. According to the present invention, there is no need for a far-infrared shielding hood that is a hindrance to aesthetics as in the past, so the optical path of infrared rays is not limited, and therefore openings are provided as appropriate along the rotational direction of the optical system. If you keep it, almost
It is possible to set the field of view in any direction within a 180 degree range.

Although the above description has mainly been made regarding the light receiver, the projector has exactly the same structure, so the gist of the present invention can be applied without any modification.

Furthermore, in the above explanation, we did not mention the details of the transparent cover on the front of the optical system.
Generally, it is not desirable for the structure of this type of alarm device to be observed from the outside;
Furthermore, in order to protect the light-receiving element from direct sunlight, it is desirable that the transparent cover be made of a material that transmits near-infrared rays but blocks visible rays, such as acrylic resin or polycarbonate resin containing dye. .

An electric circuit for driving the light emitting element is connected to the emitter, and an electric circuit for amplifying and discriminating the output of the light receiving element and activating the alarm is connected to the light receiver. This constitutes an alarm device, but since this alarm device is a well-known technology, its explanation will be omitted.

As detailed above, the infrared security alarm device according to the present invention has a very simple structure in which an opening is provided in a part of the transparent cover in front of the optical system, but it is designed to prevent malfunctions caused by frost buildup in conventional devices. The far-infrared shielding hood that was required for this purpose can be completely removed, resulting in an aesthetically pleasing product.In addition, the opening is provided within the light beam transmission area.
Even if frost builds up on the front surface of the translucent cover at night during winter, more than the minimum amount of light received is ensured, the alarm function is maintained, and a highly reliable security alarm system is obtained. Further, as shown in the embodiment, when a plurality of openings are arranged in series, it is possible to set an arbitrary field of view within a range of approximately 180 degrees, and this exhibits a remarkable effect.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional infrared security alarm system.
FIG. 2 shows an infrared security alarm device according to the invention, and FIGS. 3 and 4 show other embodiments of the invention. 1... Emitter or receiver, 2... Transparent cover, 3
... Far-infrared shielding hood, 4... Condensing mirror, 5... Opening, 6... Light receiving element, 7... Optical system support member.

Claims (1)

[Scope of Claims] 1. A device comprising a projector that emits infrared rays, a receiver that receives the infrared beam emitted from the projector, and an alarm device connected to the receiver, wherein the projector and the receiver are configured to emit light. element or light-receiving element, an optical system interposed between the infrared beam and the light-emitting element or the light-receiving element, and a transmission cover that transmits the infrared beam,
An infrared security alarm device characterized in that an opening smaller than the cross-sectional area of the infrared beam is provided in the infrared beam transmission area of the transmission cover. 2. The infrared security alarm device according to claim 1, characterized in that a plurality of openings are arranged in series in the transparent cover on the front surface of the optical system. 3. The infrared security alarm device according to claim 1 or 2, characterized in that the optical system of the projector or receiver is rotatable. 4. The infrared security alarm device according to any one of claims 1 to 3, wherein the transparent cover is made of a material that blocks light in the visible range. 5. The infrared security alarm device according to claim 1, wherein the area of the opening is 1/100 or more of the cross-sectional area of the infrared beam.