JPH0639311Y2 - Heat ray detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat ray sensor that outputs a corresponding electric signal when a heat source that generates heat rays is present in a detection region.

BACKGROUND ART Generally, a heat ray detector includes a heat ray sensing element that senses a heat ray, and a light condensing means that condenses an incident light ray on a light receiving surface of the heat ray sensing element. Mirrors and Fresnel lenses are used. If such a light collecting means is exposed to the outside, the reflection efficiency and the transmission efficiency will be deteriorated due to the adhesion of dust and the like, which will cause a secular change, so it is desirable to cover the light collecting means with a cover.

By the way, in the past, it was general to use a reflecting mirror as a light converging means, but recently a Fresnel lens is used as a light converging means because the development period is short and the investment cost to the mold is small and easy. The number of heat ray detectors used is increasing. When the Fresnel lens is used as the light converging means, the incident light is attenuated by both the cover and the Fresnel lens, so it is necessary to enhance the sensitivity of the heat ray sensing element. In particular, a heat ray sensor intended to detect heat rays from a long distance requires high sensitivity, and as a result, malfunction due to outside light cannot be avoided.

[Object of the Invention] The present invention has been made in view of the above points, and its main purpose is to provide a cover with a selective permeability that allows only heat rays to pass therethrough. Another object of the present invention is to provide a heat ray sensor which prevents malfunction due to external light.

DISCLOSURE OF THE INVENTION (Embodiment) As shown in FIG. 1, when a heat ray is received like a pyroelectric element, a corresponding electric signal is generated and a corresponding electric signal is generated. The Fresnel lens 3 is provided, and in front of the Fresnel lens 3, a heat ray transmissive cover 4 that covers the Fresnel lens 3 over the entire surface is provided. As shown in FIG. 2, the heat ray transmissive cover 4 has an uneven matte surface 7 formed by embossing on the entire surface of a transparent substrate 5 made of polyethylene, which is a material that absorbs less heat rays. Is. Here, an example in which the mat surface 7 is formed on one surface of the transparent substrate 5 is shown, but the mat surface 7 may be formed on both surfaces of the transparent substrate 5. The pitch of the irregularities on the matte surface 7 is set to about a half wavelength (0.2 to 0.3 μm) of the central wavelength (approximately 0.4 μm) of the visible light region. Therefore,
The matte surface 7 has a selective transmissivity so as to reflect or absorb a light ray in a region having a shorter wavelength than the heat ray and transmit only the heat ray.

As described above, by disposing the heat ray transmission cover 4 having the matte surface 7 having selective permeability in front of the Fresnel lens 3, only heat rays can be introduced into the heat ray sensing element 1. The effect of external light can be removed. Further, by disposing the heat ray transmission cover 4 closer to the heat source than the Fresnel lens 3,
As compared with the case where the heat ray transmitting cover 4 is provided between the heat ray sensing element 1 and the Fresnel lens 3, it is possible to remove the light rays in the wavelength region other than the heat ray in the portion having a smaller energy density. Therefore, there is an advantage that unnecessary external light can be removed even with the matte surface 7 having a relatively small thickness, the attenuation factor of the heat ray can be reduced, and only the heat ray can be efficiently introduced into the heat ray sensing element 1. Furthermore, since the selective permeability is imparted by the matte surface 7 formed by the embossing, it is possible to impart the selective permeability at the same time as the molding of the heat ray transmissive cover 4, and impart the selective permeability to the heat ray transmissive cover 4. This eliminates the need for a separate process and facilitates manufacturing.

[Advantages of the Invention] As described above, the present invention has a heat ray sensing element for sensing a heat ray, a light collecting means for collecting incident light on a light receiving surface of the heat ray sensing element, and a light collecting means arranged in front of the light collecting means. It is composed of a heat ray transmission cover that covers substantially the entire front surface of the light means and selectively transmits only heat rays. Since it is provided to the cover, there is an advantage that external light other than heat rays is not introduced into the heat ray sensing element, and malfunction due to outside light can be prevented. Further, since the heat ray transmission cover is arranged on the side closer to the heat source than the light collecting means, the energy density is small as compared with the case where the heat ray transmission cover is arranged between the heat ray sensing element and the light collecting means. It is possible to remove light rays in the wavelength region other than the heat ray at a part, and it is possible to make the thickness of the member having selective permeability relatively small, the attenuation rate of the heat ray becomes small, and only the heat ray can be efficiently heated. It has the advantage that it can be incorporated into the sensor element. Moreover, the heat ray transmissive cover has a matte surface on at least one of the front and back surfaces of the heat transmissive substrate, which absorbs less heat ray, and has an uneven surface with a pitch of about a half wavelength of visible light rays formed over almost the entire surface. The matte surface formed on the surface of the transmissive substrate that allows transmission of heat can enhance the efficiency of separation of visible rays and heat rays. Moreover, the matte surface having selective transparency can be formed at the same time as the heat ray transmission cover is textured. Since it can be formed, it does not require a separate step for imparting selective permeability, and has an effect of facilitating manufacturing.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of heat ray sensing according to the present invention, and FIG. 2 is a sectional view of a heat ray transmitting cover used in the same. 1 is a heat ray sensing element, 2 is a light receiving surface, 3 is a Fresnel lens,
Reference numeral 4 is a heat ray transparent cover, 5 is a transparent substrate, and 7 is a matte surface.

Claims (1)

[Scope of utility model registration request] 1. A heat ray sensing element for sensing a heat ray, a light collecting means for collecting incident light on a light receiving surface of the heat ray sensing element, and a front surface of the light collecting means disposed in front of the light collecting means on substantially the entire surface. It consists of a heat ray transmissive cover that covers over and selectively transmits only heat rays.The heat ray transmissive cover has about half a wavelength of visible light over almost the entire surface of at least one of the front and back surfaces of the transparent substrate that absorbs less heat rays. A heat ray detector having a matte surface on which unevenness of the pitch is formed.