U.S. Philips Corporation

Geoffrey Baker

Martin Renals

Patrick J Ball

Alexander D Annis

Roger Pearce

Paul L Williamson

Roger A Lockett

An infra-red radiation detector has a pyroelectric element (10), comprising for example TGS material, supported in spaced relationship over a heatsink body (16) for stabilizing the temperature of the element in operation with the space between opposing faces of the element (10) and body (16) containing a thermally-conductive, non-hardening and non-gaseous gel-like medium (22) such as silicon dielectric gel which thermally couples the element with the body. A small quantity of material such as solder or epoxy may be used to bond the element to the body and fix the spacing therebetween or, alternatively, the element may be supported over and bonded to the body simply by means of the medium (22) itself. Capillary action may conveniently be used to introduce the medium into the space between the element and the body.

Pyroelectric infra-red detectors and their method of manufacture

An infrared radiation detector device, for example, for an intruder alarm, comprises two dual detectors. Each dual detector constitutes a separate detection channel and has two pyroelectric detector elements. The detector elements are formed from pyroelectric material with electrodes on opposite surfaces. The detector elements of each dual detector are spaced apart from one another and connected in a circuit differentially to cancel out the effects of temperature changes common to both elements. One detector element of one dual detector is interdigitated with a respective detector element of the other dual detector, thus enabling the two dual detectors to respond to incoming radiation and provide outputs at, or very nearly at, the same time. In this way, when used in an intruder alarm, the risk of false triggering is reduced. The other detector elements of the dual detectors may similarly also be interdigitated.

Infra-red radiation detector devices

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

The detector has a pyroelectric element sandwiched between two electrodes which are transparent to the wavelength of radiation to be detected. The pyroelectric element is maintained in spaced relationship to the surface of a header by a pillar and by a lead of a microminiature package which is mounted on its back on the header surface. A second pyroelectric element can be similarly supported by another lead and another pillar. Electrical connections between the remaining leads and the posts of the header, and between the upper electrodes of the pyroelectric elements can be made with metal foil straps, thus eliminating the need for bonded wires.

Infrared radiation detector

The indiction of temperature discontinuities in a scene can be used to indicate the boundaries of objects, for example the level of the contents of a storage silo. The thermal radiation from the object scene is imaged upon a pair of adjacent pyroelectric radiation detectors 9, 10. The scene radiation is chopped and the difference in detector outputs displayed to the observer while the field of view of the detectors, aligned with a visual aiming sight, is traversed across the object. The location and sign of a temperature discontinuity in the visual scene enables the observer to measure the silo contents.

Differential radiation detection apparatus

In a pyroelectric detector circuit arrangement in which a pair of capacitive detector elements (C.sub.1 and C.sub.2) formed of polarized pyroelectric material are electrically connected in series with the directions of polarization of the elements being such that the normally produced signal voltages are in opposition, means are provided for inhibiting the depoling of the elements under conditions of cooling or excessive temperature cycling. These depoling inhibiting means comprise a pair of ultra-low leakage diode elements (D.sub.1 and D.sub.2) in series opposition connection and arranged in parallel connection with the capacitive detector elements. Connections are present between the common points in the diode series and the capacitive detector element series. The diode elements are arranged with respect to the directions of polarization of the detector elements so that under conditions of large decreases in temperature of the detector elements the voltages generated across the detector elements are effective to forward bias the diode elements into conduction and thereby inhibit depoling of the detector elements. The diode elements, under normal conditions of irradiation of the detector elements, present a high impedance path between the input of FET amplifier means and a point of constant potential. In one embodiment the capacitive detectors (C.sub.1 and C.sub.2), the ultra-low leakage diode elements (D.sub.1 and D.sub.2), and FET amplifier means are present in a common envelope in the form of a hybrid microcircuit having only three external terminal connections.

Radiation detector circuits which inhibit depoling of the detector

A radiation detector circuit including a pyroelectric detector element and field effect transistor amplifier means. In order to inhibit saturation of the amplifier means under conditions of large transients in the radiation input or progressive changes in radiation input of low magnitude, at least one ultra-low leakage non-linear device is connected in the part of the circuit including the gate electrode of the amplifier means and the detector element. In one embodiment a pair of picoampere diodes are reverse parallel connected across the detector element and the circuit is formed as a hybrid microcircuit device having three external terminal connections. In another embodiment the non-linear device is incorporated in a feedback path between the output side of an amplification stage and the detector element.

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Southampton, United Kingdom

Geoffrey Baker