Infra-red radiation detector devices.

摘要

An infra-red radiation detector device, for example, for an intruder alarm comprises two dual detectors each of which constitutes a separate detection channel and has two pyroelectric detector elements (10, 12 and 11, 13) formed from pyroelectric material (22, 30) with electrodes on opposite surfaces, the detector elements of each dual detector being 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 (10) of one dual detector is interdigitated with a respective detector element (11) 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 (12 and 13) of the dual detectors may similarly also be interdigitated.