U.S. Philips Corporation

Martin Renals

Geoffrey Baker

Patrick J Ball

Michael A Rose

An infrared radiation detector comprises a pyroelectric detector element in a hermetically sealed housing. The housing comprises a base and cover with an aperture. A Fresnel lens, for example made of polyethylene transmissive in the 8-14 .mu.m wavelength range, is fastened over the aperture on the inside of the cover for condensing the radiation to be detected onto the detector element. In one example the Fresnel lens is held against a flange surrounding the aperture by a press-fit ring. Alternatively, the Fresnel lens is glued to a silicon window which in turn is fastened to the flange surrounding the aperture. The Fresnel lens thus forms an integral part of the detector housing avoiding the need for external mirrors or lenses.

Infrared radiation detector with integral fresnel lens window

A pyroelectric infrared radiation detector which is particularly suited to automated assembly comprises a pyroelectric detector element mounted in a housing having a window transparent to infrared radiation. Electrically conductive leads in a single-in-line configuration extend through a base portion of the housing for making external electrical connections to the detector. One lead has an extended portion within the housing. The extended portion provides a cantilever support to which the detector element is fastened. The leads may all be formed from portions of a unitary lead frame. A second differentially connected pyroelectric detector element may be fastened to another cantilever support formed by a portion of the same lead frame. The cantilever supports preferably extend from an insulating block which encapsulates an associated electrical component and which also provides support for the detector elements.

Infra-red radiation detector

An infrared radiation detector for an intruder alarm has a pyroelectric element comprising a pyroelectric body sandwiched between two electrodes. The element is supported above a header by two leads of a microminiature circuit package. The package is mounted on its back on the header. One lead of the circuit package is electrically connected to the element. The other lead is insulated from the element. A second pyroelectric element may similarly be supported by two leads of the package.

Pyroelectric infrared radiation detector

An infrared radiation detector comprises two differentially connected pyroelectric detector elements in parallel-opposition. The detector elements are formed in a single body of pyroelectric material having two adjacent pairs of overlapping electrodes on opposite major surfaces of the body. The two detector elements are poled in the same direction. To electrically connect the top electrodes of each pair to the bottom electrodes of the other pair, each electrode is provided with an L-shaped extension. Each extension is arranged such that at an edge of the body the extension of the top electrode of one pair overlaps the extension of the bottom electrode of the other pair. The overlapping extensions can be electrically connected together by conductive epoxy or by conductive clips on the edge of the body.

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Southampton, United Kingdom

Martin Renals