Abstract: There is disclosed an optical microphone which reduces hindrance to the vibration of a membrane with respect to the input elastic wave, to thereby obtain a linear output current fluctuation with respect to the input elastic wave. Specifically, the total area of an outlet window 8 for performing irradiation and an inlet window 7 for receiving light is made equal to or less than 5% of the area of a membrane 5. And the vertical sectional shape of a light-guiding portion 9 includes a multidimensional function curve portion of 1.2 dimension or more. Moreover, the sectional shape is such that if an angle formed between the substrate and the tangent of the sectional shape at an intersection of the curve and a normal with respect to the substrate respectively extended from the light emission element and the light-receiving element is designated as &agr;, the critical angle of the light-guiding portion material becomes larger than 180-2&agr;.

Abstract: An infrared human body detector has an infrared detector (PE) having at least one light-detecting surface and disposed in a plane, groups of divided infrared ray converging members (LR and LD) disposed in the plane about the infrared detector in surrounding relation thereto, a primary reflecting mirror member (M.sub.1 or M.sub.1 ') disposed inwardly of the groups of divided infrared ray converging members for reflecting, in a primary fashion, rays (B) applied inwardly through the respective groups of divided infrared ray converging members, and a secondary reflecting mirror member (M.sub.2) disposed inwardly of the groups of divided infrared ray converging members for introducing the reflected rays from the primary reflecting mirror member within a sensitive angle of the infrared detector to apply the rays to the light-detecting surfaces thereof, the secondary reflecting mirror member having a reflecting surface sufficiently small as compared with the surface areas of the infrared ray converging members.

Abstract: A pyroelectric infrared sensor for use in intrusion alarm systems, including a pyroelectric ceramic element provided with two pairs of electrodes, of which the front electrodes are so configured as to permit a simplified printing process for higher productivity and lower production costs. The front electrodes each have a first region overlapping with a part of one of the back electrodes and a second region overlapping with a part of the other of the back electrodes, and are arranged adjacent to each other and are electrically insulated from each other. The first regions and the second regions of the front electrodes have a ratio of areas of approximately 1:1. The pyroelectric element is attached to a holding member which is so designed that the back electrode areas of the element are free from physical contact with any thermally conductive solid material that may detract from the thermal responsiveness of the element.

Abstract: An ultrasonic transducer comprises a vibrating assembly having a thickness-poled piezoelectric ceramic disk (12) bonded concentrically to a resonant plate (13) of greater diameter than that of the ceramic disk (12), which having a radiator (30) is set in the center of the resonant plate (13) on the opposite surface to the ceramic disk (12), and which fitted onto a plastic baseplate (51) using such adhesive (52) as will retain elasticity after curing and accommodated within a housing (80) with a director (81) on top.The ultrasonic transducer has superior performance to conventional bimorph devices by 6 dB in terms of receiving sensitivity.