Abstract: Abeam detector apparatus (1) comprising: beam emitter apparatus (2); reflector apparatus (3), locatable across a volume to be monitored; and beam receiver apparatus (4). The beam emitter apparatus (2) is capable of creating a first linearly polarised beam of light of first linear polarisation and directing said first linearly polarised beam of light towards the reflector apparatus. The reflector apparatus (3) is capable of either: receiving the first linearly polarised beam of light and modifying such light into a beam having circular polarisation, elliptical polarisation or being unpolarised, and reflecting said circularly polarised, elliptically polarised or unpolarised beam of light towards the beam receiver apparatus; OR receiving the first linearly polarised beam of light and reflecting such light towards the beam receiver, and modifying such light into a beam having circular polarisation, elliptical polarisation or being unpolarised.

Abstract: A method for aligning a projected beam on a reflector in a reflective-type beam detector, the method including adjusting the projected beam so as to: project on to substantially all, if not all, of a reflective surface of the reflector; or project on to at least a portion of a reflective surface of the reflector until a constant, or within a predetermined threshold of a constant, signal is received from the reflector; and detecting one or more edges of the reflective surface of the reflector and thereby: centering the projected beam, so as to align an approximate center of the projected beam on, or within a predetermined threshold of, an approximate center of the reflective surface of the reflector; and/or determining a shape or profile of the reflector.

Abstract: A flame detector (1) including: a fire sensor (2a), capable of detecting a characteristic blackbody-type radiated heat signature emitted by a flaming material; and a guard sensor (2b), for detecting an at least further part of the spectrum emitted by the material and which serves to assist in rejecting false alarms, wherein, in use during detection of a flame, the guard sensor (2b) detects an amount of radiation G and the fire sensor (2a) detects an amount of radiation F, and positive detection of a flaming material depends upon the following criteria: F>0; G>0; and F>G.

Abstract: A method for adjusting the timing of beam projections in a beam detector. The method includes projecting a beam for the purpose of detecting obscuration of the beam and, if a level of signal of the beam detected is less than a threshold for each of a number of consecutive projections or for each consecutive projection over a pre-determined time period, initiating a warning, signalling an alarm or otherwise reacting. The method further includes adjusting the timing of projecting the beam from a nominal transmit interval ‘T’ to be within a window time-period ‘W’ extending from an amount before to an amount after the nominal transmit interval ‘T’.

Abstract: A method for adjusting the timing of beam projections in a beam detector. The method includes projecting a beam for the purpose of detecting obscuration of the beam and, if a level of signal of the beam detected is less than a threshold for each of a number of consecutive projections or for each consecutive projection over a pre-determined time period, initiating a warning, signalling an alarm or otherwise reacting. The method further includes adjusting the timing of projecting the beam from a nominal transmit interval ‘T’ to be within a window time-period ‘W’ extending from an amount before to an amount after the nominal transmit interval ‘T’.

Abstract: A method for aligning a projected beam on a reflector in a reflective-type beam detector, the method including adjusting the projected beam so as to: project on to substantially all, if not all, of a reflective surface of the reflector; or project on to at least a portion of a reflective surface of the reflector until a constant, or within a predetermined threshold of a constant, signal is received from the reflector; and detecting one or more edges of the reflective surface of the reflector and thereby: centering the projected beam, so as to align an approximate center of the projected beam on, or within a predetermined threshold of, an approximate center of the reflective surface of the reflector; and/or determining a shape or profile of the reflector.

Abstract: A flame detector (1) including: a fire sensor (2a), capable of detecting a characteristic blackbody-type radiated heat signature emitted by a flaming material; and a guard sensor (2b), for detecting an at least further part of the spectrum emitted by the material and which serves to assist in rejecting false alarms, wherein, in use during detection of a flame, the guard sensor (2b) detects an amount of radiation G and the fire sensor (2a) detects an amount of radiation F, and positive detection of a flaming material depends upon the following criteria: F>0; G>0; and F>G.