Pyrodetector for the detection of a body entering into its detection area

Claim 1

A pyrodetector for detection of a body entering into a detection area of the pyrodetector, said body having a temperature deviating from its environment, comprising: a concave mirror shaped to focus heat radiation emanating from the body; a first sensor element positioned at a focus of the concave mirror and at least one further sensor element positioned for compensation of environmental influences; a film of uniform electrically non-conductive material having an iso-directional, permanent orientation polarization and electrodes situated thereon which are employed to form the first and further sensor elements; the film and sensors forming an arrangement which is secured in a mounting; a covering positioned to cover a cavity of the mirror and which is permeable to incident radiation; an electronic evaluation means; the film and sensor elements being arranged in the concave mirror such that radiation reflected by the concave mirror is incident on both surface sides of the film; the concave mirror being a parabolic mirror dimensioned such that its focus lies in an inner half thereof; the film with the sensor elements lying at an optical axis of the concave mirror so that the first sensor element is essentially impinged only by a radiation of the body which has been reflected in the concave mirror when the body is situated at a large distance relative to a size of the mirror; the covering comprising a thin film of polyethylene which is stretched over a honeycomb lattice acting as a support and which is arranged in front of the cavity of the mirror; said concave mirror being formed of a body having side walls perpendicular to one another and having a rectangular cross-section with a major axis and a minor axis, and a reflector portion extending inwardly from said side walls and curved in two planes forming a continuous arced surface as said concave mirror; said film with said sensor elements being positioned in said mounting parallel to said minor axis, and an opening in said reflector portion of said concave mirror which is dimensioned to permit insertion of said film together with a retaining frame carrying said film and said mounting; said mounting comprising two spaced apart U-shaped parts dimensioned for mounting said retaining frame, said U-shaped parts being parallel to one another from said opening into the cavity of the concave mirror; said electronic evaluation means comprising a circuit board with printed interconnnects and active and passive electrical components, said circuit board being arranged outside of said concave mirror and behind the reflector portion thereof, and said sensor elements being connected to said evaluation means via plug pins extending from said retaining frame; said electronic evaluation means being held by resilient clamps provided with barbs, said clamps being secured to said body rearwardly of said concave mirror; and said concave mirror, retaining frame with the film and sensor elements, the electronic evaluation means, and the honeycomb lattice provided with the cover being accommodated in a housing means for shielding against disturbing influences.