OPTICAL DEVICE FOR THERMAL DETECTOR

摘要

PURPOSE:To obtain a thermal detector which has a caution area in a horizontal 360 deg. direction by guiding a horizontal heat ray incident on the entire 360 deg. periphery of a detector to the photodetection surface of a pyroelectric element by an optical path changing means. CONSTITUTION:Fresnel lenses 1 are arranged over the entire 360 deg. periphery at equal intervals as shown in a figure (a) and a pole 3 for standing a device body 2 on a floor surface is provided at the center bottom part of the device body 2. The respectively lenses 1 have their lens surfaces directed horizontally to have a visual field in the horizontal 360 deg. directions. Then, a reflecting mirror 4 whose reflecting surface slants downward slantingly is arranged circularly corresponding to the respective lenses 1 as shown in a figure (b) and the pyroelectric element 5 is arranged below the arrangement center of the reflecting mirror 4 so that the photodetection surface faces up. A heat ray incident on the lens 1 horizontally in parallel is reflected by the reflecting mirror 4 and converged on the element 5 at the focus position of the lens 1, so horizontally 360 deg. monitoring is possible about the thermal detector as the center.