Self-compensating projected-beam smoke detector

Abstract

A modular transceiver head including cooperative cover and base members operable as a transmitter or as a receiver of infrared energy. The cover member includes a window defining a comparatively wide field of view in azimuth and in elevation. An optical train including a gimbaled specular member that is mounted to the base member readily allows both rough and fine adjustment of the pointing direction of the specular member anywhere within the field of view of the cover member window. A controller including a processor is coupled to a transceiver head pair respectively operative as a transmitter and as a receiver of infrared energy to controllably project a beam of infrared energy therebetween through a protected region. The controller is operative to de-sensitize the beam against potential electrically interferring effects present along the beam path. The controller is periodically operative in a self-test mode to reduce the intensity of the projected-beam to simulate a smoke condition. The controller is periodically operative in a self-compensation mode to compensate for long and short term beam degredation effects such as pollution variation normally encountered along the beam path arising in the normal operation of the protected region and to compensate for film build-up on the elements of the transceiver head optical trains. The controller is cooperative with a watch-dog timer to monitor its own operating state. Plural alalrm thresholds are operator selectable to provide enhanced confidence detection, and particularized signal indications are provided to readily and quickly identify possible alarm and trouble conditions.