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1. (WO2010124347) IMPROVEMENTS TO PARTICLE DETECTORS
Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

CLAIMS

1. A light source for use in a particle detection system, the light source adapted to transmit:

a first light beam in a first wavelength band;

a second light beam in a second wavelength band; and

a third light beam in a third wavelength band,

wherein the first and second wavelengths bands are substantially equal and are different to the third wavelength band.

2. A light source as claimed in claim 1 wherein first and second wavelength bands are in the ultraviolet portion of the electromagnetic spectrum.

3. A light source as claimed in any one of the preceding claims wherein the third wavelength band is in the infrared portion of the electromagnetic spectrum.

4. A light source as claimed in any one of the preceding claims wherein a location from which the first light beam is transmitted from the light source is separated from the location from which the second light beam is transmitted from the light source.

5. A light source as claimed in claim 5 wherein the separation is in any one of the following ranges 10 to 20mm, 20 to 30mm, 30 to 40mm, 40 to 50mm.

6. A light source as claimed in any one of the preceding claims wherein the light source further includes a first light emitter for emitting the first and second light beams and a second light emitter for emitting the third light beam.

7. A light source as claimed in claim 6 wherein the light source further includes a beam splitter for splitting light emitted from the first light emitter into the first and second light beams.

8. A light source as claimed in any one of the preceding claims which includes a first light emitter for emitting the first light beam, and a second light emitter for emitting the second light beam, and a third light emitter for emitting the third light beam.

9. A light source as claimed in claims 6 or 8 wherein the first, second and/or third light emitters are light emitting diodes.

10. A light source as claimed in any one of the preceding claims which further includes a controller configured to cause the light source to generate the first, second and third light beams in a repeated sequence.

11. A light source as claimed in claim 10 wherein the repeated sequence includes the alternate operation of the first, second and/or third light emitters.

12. A light source for use in a particle detection system, the light source including:

a first light emitter for emitting a first beam of light;

a second light emitter for emitting a second beam of light; and

an optical system including a transmission zone from which light from the first and second light emitters is transmitted from the light source, wherein the optical system is arranged such that obstruction of the transmission zone results in a substantially equivalent obstruction of both the first and second beams of light.

13. A light source as claimed in claim 12 wherein the first and second light emitters are semiconductor dies.

14. A light source as claimed in claim 13 wherein the semiconductor dies are housed within a single optical package.

15. A light source as claimed in any one of claims 12 to 14 wherein the optical system further includes light directing optics for directing the first and second beams of light from the first and second light emitters to the transmission zone.

16. A light source as claimed in claim 15 wherein the light directing optics are selected from a group including:

a convex lens, a Fresnel lens, and a mirror, or a combination of any two or more of the aforementioned optical elements.

17. A light source as claimed in any one of claims 12 to 16 wherein the transmission zone forms at least a part of an externally accessible optical surface of the optical system.

18. A light source as claimed in any one of claims 12 to 17 in which the optical system may includes beam shaping optics adapted to modify a beam shape of either or both of the first and second beams of light.

19. A light source as claimed in claim 18 wherein the beam shaping optics provide light transmitted from the light source with a beam divergence of approximately 10 degrees.

20. A light source as claimed in either of claims 18 or 19 in which the beam shaping optics may modify the beam shape of either or both of the beams to extend further in one direction than another.

21. A light source as claimed in any one of claims 18 to 20 in which the beam shaping optics modify the first and second beams so that they have a different beam shape to each other.

22. A light source as claimed in claim 21 in which the beam shaping optics modify the first beam of light to have a wider beam shape than the second beam of light.

23. A light source as claimed in any one of claims 18 to 22 in which the beam shaping optics include one or more beam intensity adjusting elements configured to adjust the spatial intensity of the beam.

24. A light source as claimed in claim 23 in which the beam intensity adjusting elements are selected from a group including:

an optical surface coating,

a ground glass d iff user, and

an etched glass d iff user.

25. A light source as claimed in any one of claims 12 to 25 wherein the first light emitter emits an ultraviolet light beam and the second light emitter emits an infrared light beam.

26. A light source as claimed in either of claims 18 to 24 in which the light directing optics and beam shaping optics are combined into a single optical element.

27. A light source for a particle detector, including:

one or more light emitters adapted to generate at least one light beam having a first apparent size from a distant point of view;

an optical system arranged to receive the at least one light beam and transmit the at least one light beam and adapted to cause the transmitted light beam to have a second apparent size larger than the first apparent size from the distant point of view.

28. A light source as claimed in claim 27 in which the optical system includes a beam diffuser.

29. A light source as claimed in claim 28 wherein the diffuser is a dedicated optical component.

30. A light source as claimed in claim 28 wherein the diffuser is integrally formed with an optical component that is used for another purpose.

31. A light source as claimed in claim 28 wherein the diffuser is formed as a surface treatment on an optical component.

32. A light source for a particle detector, including: one or more light emitters adapted to generate at least one light beam having components in at least two wavelength bands, and optionally an optical system through which the one or more beams pass; the light emitter(s) and or optical system being configured to cause light in one of the at least two wavelength bands to have a spatial intensity profile which is different to light in another of the wavelength bands.

33. A light source as claimed in claim 32 wherein the beam width of light in one wavelength band is wider than the beam width of light in another wavelength band.

34. A light source as claimed in claim 32 or 33 wherein light in a longer wavelength wavelength band has a narrower beam width than light shorter wavelength wavelength band.

35. A light source as claimed in claim 34 wherein the longer wavelength band includes the infrared or red portion of the EM spectrum.

36. A light source as claimed in claim 34 wherein the shorter wavelength band includes light in the blue, violet or ultraviolet portion of the EM spectrum.

37. A particle detection system including:

a light source as claimed in any one of claims 1 to 36; and

a receiver for receiving a beam or beams of light emitted by the light source and determine on the basis of the received beam or beams of light whether particles are impinging on the beams.

38. A beam detector arrangement comprising,

a transmitter adapted to transmit one or more beams of light having a predetermined characteristic over a field of illumination, and

a receiver having a field of view and adapted to receive a beam of light transmitted by the transmitter;

said beam detector being installed to protect a monitored volume which includes a structure having one or more reflective surfaces within the field of illumination of the transmitter and the field of view of the receiver; wherein the beam detector includes a processor adapted to determine whether a light beam received at the receiver possesses one or more predetermined light characteristics.

39. A beam detector as claimed in claim 38 wherein in the event that the one or more characteristics are possessed the processor is adapted to determine that a beam of light from the transmitter is received.

40. A beam detector as claimed in either claim 38 or 39 wherein in the event that a received beam does not possess one or more of said characteristics, the processor can determine that a beam of light from the transmitter is not received.

41. A beam detector as claimed in claim 38 or 39 wherein in the event that a received beam does not possess one or more of said characteristics, the processor adapted to determine that the beam of light received is a reflection of the transmitted beam.

42. A beam detector as claimed in any one of claims 38 to 41 wherein the beam detector arrangement can include signalling means adapted to signal a fault condition in the event that the processor determines that a beam of light from the transmitter is not received and/or a reflected beam is received.

43. A method for determining whether a beam of light received by a receiver of a beam detector is a directly transmitted beam or a reflected beam, said method including:

receiving the beam at a receiver and measuring one or more predetermined characteristics of the beam, and

depending on an extent to which the predetermined characteristic is present in the beam, determining if the received beam is a directly transmitted beam or a reflected beam.

44. A method as claimed in claim 43 wherein, in the event that the one or more characteristics of the received beam do not substantially match one or more predetermined characteristics of the transmitted beam the method can include, determining that the received beam is a reflection.

45. A method as claimed in either of claims 43 or 44 wherein the beam characteristics can include relative strength of two or more wavelength components in the received beam and/or received polarisation characteristics of the beam.

46. A receiver for a beam detector, the receiver including:

a plurality of image sensors, each image sensor including a plurality of sensor elements, said image sensors being arranged to have at least partially overlapping fields of view;

an optical arrangement adapted to form an image on each of the two sensors,

image analysis means to analyse an image from more than one of the plurality of image sensors to determine an angular position of an image component within the field of view of a plurality of the sensors.

47. A receiver for a beam detector as claimed in claim 46 in which the component is one or more beams transmitted by a light source of a beam detector.

48. A receiver for a beam detector, the receiver including:

one or more sensors including a plurality of sensor elements to receive a beam of light from a transmitter;

processing means in data communication with the one or more sensors to receive and process image data therefrom; and

input means adapted to receive an input representative of a number of beams which are to be received from one or more transmitters of the beam detector.

49. A receiver for a beam detector as claimed in claim 48 wherein the input means includes any one or more of the following;

one or more switches, a data input interface over which data may be provided to the processor means, or memory associated therewith.

50. A beam detector including:

one or more light sources adapted to transmit said beam of light across a region being monitored;

one or more receivers arranged with respect to the transmitter and the volume being monitored such that light from the transmitter arrives at the receiver after traversing at least a part of the volume being monitored; and

one or more light blocking baffles arranged with respect to the volume being monitored and the transmitter and/or receiver such that no reflections from a surface within a field of illumination a light source and a field of view of a light receiver of the beam detector arrive at the receiver.

51. A transmitter for a beam detector including one or more light sources adapted to generate light in a spatially distinct beam pattern.

52. A transmitter as claimed in claim 51 in which the spatially distinguishable beam pattern is not symmetrical in at least one plane.

53. A transmitter as claimed in claim 51 or 52 in which the spatially distinguishable beam pattern includes a pattern of individual light beams having distinguishable characteristics.

54. A transmitter as claimed in claim 53 in which the distinguishable characteristics are any one or more of wavelength characteristics, polarisation characteristics or modulation characteristics.

55. A transmitter as claimed in claim 53 wherein the distinguishable pattern includes a pair of distinguishable light beams.

56. A transmitter as claimed in claim 51 in which the transmitter has single light source which produces a beam that is directionally distinguishable from an image of the beam.

57. A method of determining whether a beam received at a receiver is transmitted by a direct or reflected path, in a beam detector including a transmitter as claimed in any one of claims 51 to 56, the method including: arranging a light source and receiver such that the beam transmitted by the light source is received at the receiver; and

orienting the light source with respect to an adjacent surface within the field of illumination of the light source and field of view of the receiver, such that a direct image of the light source and reflected mirror image of the light source from the surface are distinguishable at the receiver.

58. A method as claimed in claim 57 wherein the step of aligning includes: aligning the light source such that its image is not symmetrical in the direct and reflected images.

59. A method of distinguishing a directly received beam from a reflected beam in a beam detector system, the method including receiving an image containing two image segments which potentially correspond to beams transmitted by the particle detector;

determining a brightness of each of the received beams; and

determining that a brightest one of the received beams is the directly received beam.

60. A method of determining which one of a plurality of received beams is directly received from a light source and which is received by a reflection from a surface, the method including:

determining which of the received beams is received at a sensor element of a light sensor of a receiver of the beam detector that is furthest perpendicularly from the reflecting surface; and

designating the determined beam image as the direct beam image.

61. A beam detector including:

a light source adapted to transmit a beam of light with a first polarisation state;

a light receiver adapted to receive light in a second polarisation state and output a received light level; and

a controller adapted to analyse the received light level and apply alarm and/or fault logic and if a predetermined fault condition exists, to initiate an action.

62. A component of a beam detector system including: at least one electro-optical component configured to emit light or receive light in a first spatial distribution; and

an optical subsystem arranged with respect to the electro-optical component such that the first spatial distribution is adjusted to form a second spatial distribution, wherein

the relative extent of the first spatial distribution along two non-parallel axes are different to the relative extent of the second spatial distribution along the same axes.

63. A component as claimed in claim 62 wherein the optical subsystem includes an anamorphic lens, or other 'wide-screen' optical system.

64. A light source for a beam detector including:

at least a light emitter to generate a beam of light; and

an optical subsystem for controlling the angular dispersion of the beam of light wherein the optical subsystem is adapted to shape the beam of light such that it has a larger angular dispersion along one axis than another.

65. A receiver for a beam detector, the receiver including:

a light sensor capable of providing an output representative of a sensed light level at a plurality of positions on the sensor; and

an optical subsystem adapted to receive light in a field of view having a first shape and direct it onto the light sensor in an image of a second different shape.

66. A receiver for a beam detector as claimed in claim 65 wherein the optical subsystem includes an anamorphic lens.

67. A component of a smoke detector comprising:

an optical module including one or more light sources and/or one or more light receivers;

mounting means for mounting the optical module to a support surface;

an articulated connection located between the mounting means and the optical module; and a visual alignment device fixed to move with the optical module for assisting in aligning the light source or sources and/or receiver or receivers, relative to a target.

68. A component of a smoke detector as claimed in claim 67 wherein the visual alignment device comprises one or more sockets in the optical module in which an alignment beam generator can be inserted.

69. A component of a smoke detector as claimed in any of claims 67 or 68 wherein the articulated connection includes one or more locking means for locking the orientation of the optical module relative to the mounting means.

70. A component of a smoke detector as claimed in any of claims 67 to 69 wherein the articulated connection comprises a ball and cup joint, capable of allowing the optical module to be tilted relative to the mounting means through a relatively large arc of tilt, the locking means adapted to lock the ball to the cup in a selected orientation.

71. A component of a smoke detector as claimed in claim 70 wherein the locking means comprises a screw member which engages in a threaded bore in the cup and contacts the surface of the ball to lock the ball and cup together.

72. A component of a smoke detector as claimed in claim 71 wherein the screw is accessible via the visual alignment device.

73. A component of a smoke detector comprising:

an optical module including one or more light sources and/or one or more light receivers;

fixed mounting means for mounting the optical module to a support surface;

an articulated mounting means located between the optical module and one or more light sources or light receivers; and

a visual alignment device fixed to move with the light source or sources and/or receiver or receivers, to assist in aligning the light source, sources and/or receivers relative to a target.

74. A component of a smoke detector as claimed in claim 73 wherein the visual alignment device comprises one or more sockets in the articulated mounting means in which an alignment beam generator can be inserted.

75. A component of a smoke detector as claimed in any of claims 73 to 74 wherein the articulated connection comprises one or more locking means for locking the orientation of the optical module relative to the articulated mounting means.

76. A component of a smoke detector as claimed in any of claims 73 to 75 wherein the articulated connection comprises a ball and cup joint, capable of allowing the optical module to be tilted relative to the mounting means through a relatively large arc of tilt, the locking means adapted to lock the ball to the cup in a selected orientation.

77. A component of a smoke detector as claimed in claim 76 wherein the locking means comprises a screw member which engages in a threaded bore in the cup and contacts the surface of the ball to lock the ball and cup together.

78. A component of a smoke detector as claimed in claim 77 wherein the screw is accessible via the visual alignment device.

79. A component of a smoke detector as claimed in any of claims 67 to 78 wherein the visual alignment device comprises a laser housed in or mounted on a cylindrical tube or shaft sized to be a sliding fit in the beam alignment means.

80. A component of a smoke detector as claimed in claim 79 wherein the laser forms part of a tool for locking the articulated connection.

81. A component of a smoke detector as claimed in any of claims 78 or 79 wherein the laser flashes in use to assist in visual identification.

82. A component of a smoke detector as claimed in any of claims 67 to 79 wherein the visual alignment device comprises a video camera mounted to move with the housing, and able to generate an image of the target.

83. A component of a smoke detector as claimed in claim 82 wherein the image includes sighting means which, when aligned with the target will indicate that the optical component is operationally aligned.

84. A component of a smoke detector as claimed in claim 82 wherein the housing includes a video camera mount which, when the camera is mounted thereto aligns the camera with the housing such that the camera has a field of view aligned in a direction in a known orientation relative to the light source.

85. A component of a smoke detector as claimed in claim 84 wherein the known orientation is axially aligned with light emitting from the light source.

86. A component of a smoke detector as claimed in any one of claims 67 to 85 wherein the component is any one of a transmitter, receiver or target for a particle detector.

87. A method of aligning a component of a smoke detector comprising:

mounting the component in an initial orientation to a support surface, the component including a visual alignment device;

determining the orientation of the component by visually observing an output of the visual alignment device;

adjusting the orientation of the component by monitoring the visual alignment device until the component is in a selected operating orientation; and

fixing the component in said operating orientation.

88. A method as claimed in claim 87, further including: removing the visual alignment device from the component.

89. A method as claimed in claim 87 wherein the orientation of the component can be determined by observing either of a position of an alignment light beam emitted from the visual alignment device at a location remote from the support surface, or observing an image of the remote surface generated by a camera of the visual alignment device.

90. An alignment tool comprising:

a shaft having a handle;

a driver actuatable by the handle;

a visual alignment device in a fixed or known orientation relative to the driver.

91. An alignment tool as claimed in claim 90 wherein the visual alignment device comprises a laser.

92. An alignment tool as claimed in claim 91 wherein a handle of the tool includes a recess therein shaped to receive the laser.

93. An alignment tool as claimed in any one of claims 90 to 92 wherein shaft is straight.

94. An alignment tool as claimed in any one of claims 90 to 92 wherein shaft is has an elbow therein

95. An alignment tool as claimed in any one of claims 90 to 92 wherein the visual alignment device comprises a video camera.

96. A visual alignment tool having:

engagement means for engaging with and aligning the visual alignment tool relative to a particle detector component; and

visual targeting means for providing a visual indication of the alignment of the particle detector component when so engaged.

97. A visual alignment tool as claimed in claim 96 wherein the visual targeting means is a camera.

98. A visual alignment tool as claimed in 96 wherein the visual targeting means is a means for projecting visible light.

99. A visual alignment tool as claimed in claim 98 wherein the visible light is a beam.

100. A tool as claimed in any one of claims 96 to 99 wherein the engagement means is an elongate projection receivable within a recess within the particle detector component.

101. A tool as claimed in any one of claims 96 to 100 wherein the visual targeting means is coaxially aligned with the engagement means.

102. A tool as claimed in any one of claims 96 to 101 wherein visual alignment tool includes an elongate handle and a shaft, the shaft projecting from an end of the handle and being coaxially aligned therewith, wherein at least a portion of the shaft forms the engagement means.

103. A tool as claimed in any one of claims 96 to 102 wherein the visual targeting means is preferably arranged at an opposite end of shaft to the handle.

104. A tool as claimed in any one of claims 96 to 103 wherein the visual alignment tool includes a driver for engaging with and actuating a locking means of a particle detector component.

105. A tool as claimed in any one of claims 96 to 104 wherein the driver is formed at an end of the shaft distal from the handle and rotatable about the axis of the shaft to actuate the locking means.

106. A tool as claimed in any one of claims 96 to 105 wherein the driver is selected from a list including:

an Allen key (hex),

Phillips head;

other propriety shape driver.

107. A tool as claimed in any one of claims 96 to 106 wherein the driver is shaped for engagement with the locking means in only a single relative rotational orientation, so that the rotational orientation of the visual alignment tool is indicative of the state of the locking means.

108. A tool as claimed in claim 107 wherein visible indicia is provided on the tool to aid in said indication.

109. A particle detector component;

the component including a mounting portion, an optical module, and locking means;

the mounting portion being fixedly attachable to a mounting surface;

the optical module being articulated relative to the mounting portion for alignment relative to a target and including means for enabling a visual indication of said alignment; and

the locking means being actuatable to lock the optical module relative to the mounting portion in a selected alignment.

110. A particle detector component as claimed in claim 109 wherein the means for enabling a visual indication are a visual targeting means, including an electro optical device.

111. A particle detector component as claimed in claim 109 wherein the means for enabling a visual indication is an engagement feature for cooperating with a visual alignment tool incorporating visual targeting means.

112. A particle detector component as claimed in any one of claims 109 to 111 wherein the optical module includes an elongate recess forming the engagement feature.

113. A particle detector component as claimed in claim 112 wherein the recess has at least one open end and is arranged so that the axis of the recess projects toward the target when the optical module is in alignment with it.

114. A particle detector component as claimed in claim 112 or 113 wherein the recess projects in any one of:

a direction parallel to a limit of a field of operation of the optical module; or

any known physical relationship with the spatial optical characteristics of the optical module.

115. A particle detector component as claimed in any one of claims 109 to 114 wherein the locking means is actuatable by the visual alignment tool.

116. A particle detector component as claimed in any one of claims 109 to 115 wherein the locking means includes a driven member located within the recess and engageable with a driver of the visual alignment tool to actuate the locking mechanism.

117. A particle detector component as claimed in claim 116 wherein the locking means is adapted to be rotationally driven about the axis of the recess to a selected orientation to actuate with locking means.

118. A particle detector component as claimed in claim 117 wherein the driven member is preferably shaped for engagement with the driver of the visual alignment tool in only a single relative rotational orientation, so that the rotational orientation of the visual alignment tool is indicative of the state of the locking means.

119. A particle detector component as claimed in claim 118 further including indicia provided thereon to aid in said indication.

120. A particle detector component as claimed in any one of claims 109 to 119 wherein one of the optical module and the mounting portion, is captured within the other portion, said articulation being effected by a spherical sliding fit between the optical module and the mounting portion.

121. A particle detector component as claimed in claim 116 wherein driven member is a grub screw within one of the optical module and mounting portion, and rotatable to engage the other of the optical module or mounting portion.

122. A particle detector component as claimed in claim 116 wherein the optical module includes a brake shoe and a cam, wherein the cam is arranged to be driven by the driven member and in turn drive the brake shoe to, frictionally or otherwise, engage the mounting portion and thereby lock the optical module relative to the mounting portion.

123. A particle detector component as claimed in claim 122 wherein the cam is attached to the driven member or integrally formed therewith.

124. A particle detector component as claimed in claim 122 or 123 wherein the braking shoe is biased towards a retracted, non-braking, position.

125. A particle detector component as claimed in any one of claims 109 to 124 wherein the optical module any one or more of the following:

a lens;

a mirror for redirecting a beam;

a light emitting element; and

light receiver.

126. A particle detector component as claimed in any one of claims 109 to 124 wherein the particle detector component is configured to operatively connect a circuit, to enable operation of the electro-optical element, to a power supply when said locking means is actuated.

127. A particle detector component as claimed in claim 126 wherein a switch may be associated with the driven member.

128. A particle detector component as claimed in claim 127 wherein the driven member caries, at a point at a radius from its axis a magnet which is arranged to act on a reed switch when the driven member is rotated to a selected orientation.

129. A method of aligning a particle detector component, the particle detector component including an optical module, a mounting portion and locking means, the method including articulating the optical module relative to the mounting portion to align a visual indication of orientation with a target.

130. A method as claimed in claim 129 wherein the method includes actuating the locking means to lock the optical module in said alignment.

131. A method as claimed in claim 129 or 130 wherein the method further includes:

engaging a visual alignment tool with the optical module of the particle detector component to provide said visual indication of the orientation of the optical module; and

disengaging said visual alignment tool.

132. A method as claimed in claim 131 wherein said actuation includes:

rotating said visual indication tool.

133. A method of installing a particle detector component including:

fixedly mounting a mounting portion of the particle detector component to a mounting surface; and

aligning the particle detector component in accordance with a method as claimed in any one of claims 129 to 132.

134. A smoke detector component, including a mounting portion, an optical module, locking means and activation means;

the mounting portion being fixedly attachable to a mounting surface;

the optical module including a electro-optical element and being articulated relative to the mounting portion for alignment relative to a target;

the locking means being actuatable in response to an installer input to lock the optical module relative to the mounting portion in a selected alignment; and

the activation means configured to operatively connect the electro-optical element to a power supply in response to said installer input.

135. A component of a particle detector including an electro-optical component adapted to at least transmit or receive an optical signal over an angular region, an optical assembly adapted to redirect an optical signal said optical assembly an electro-optical component being mounted relative to each other such that the electro-optical component receives or transmits optical signals via the optical assembly, wherein: the orientation of the optical assembly is adjustable with respect to the electro-optical component to enable the direction of optical signals transmitted or received by the component to be changed.

136. A particle detector assembly comprising:

a first module having an actuator and a second module configured to be mounted to the first module,

the second module comprising:

an electro-optical system for use in a beam-detection system and a power source operable to provide electrical power to the electro-optical system;

a switch responsive to the actuator, wherein when the second module is mounted to the first module, the actuator causes the switch to operatively connect the power source to the electro-optical system.

137. A particle detector assembly as claimed in claim 136 wherein the actuator is a magnet, and wherein a reed switch is used to detect the proximity of the magnet when the two modules are assembled.

138. A method in an optical beam detector, including:

detecting a long time drift in received light level in a particle detection system; and

increasing gain of a detection circuit to compensate for the drift.

139. A light emitter usable in a particle beam detector, the light emitter including: housing including a window portion through which light is emitted;

means to generate light in a plurality of wavelength bands; and

a light sensitive element arranged within the housing and configured to receive a portion of the light in at least one or more of the wavelength bands emitted by the means to generate light;

one or more electrical contacts for enabling electrical connection between the means to generate light, the light sensitive element and an electrical circuit.

140. A method of determining the output strength of a light emitting element of a light source in a particle detector, the method including:

illuminating the light emitting element in accordance with a modulation pattern including "on periods" in which the light emitter is emitting light and "off periods" in which no light is emitted by the light emitter;

detecting the output from the light emitting element in one or more on periods and one or more off periods;

correcting the detected light output in one or more on periods on the basis of the measured light level in the one or more off periods.

141. A method in a light source of a particle detector, the method including:

illuminating at least light emitter of the light source according to a first modulation pattern, the pattern including a plurality of illumination pulses;

receiving a feedback signal; adjusting the modulation pattern in response to the feedback signal.

142. A component for a beam detector including:

a housing having at least one side defining at least one internal volume, the at least one wall including an optically transmissive wall portion through which light may pass into or out of the housing;

an electro-optical system within the internal volume adapted to transmit and/or receive light through an optically transmissive wall portion of the housing;

a foreign body detection system adapted to detect a foreign body on or near an outer surface of the optically transmissive wall portion, and including a light source adapted to illuminate the outer surface and any foreign body on or near the outer surface;

a light receiver to receive light scattered from the foreign body in the event one is illuminated, and generate an output signal;

a controller adapted to analyse the output signal and apply fault logic to determine the presence of a foreign body in the event that one or more criteria are met and take an action.

143. A method in a particle detection system comprising one or more light sources and a receiver arranged so that light from the one or more light sources traverses an area to be monitored for particles and is received by the receiver, and a controller programmed to monitor for the occurrence of one or more predefined alarm and/or fault conditions based on at least one received light intensity threshold; the method including:

providing at least one initial light received intensity threshold for use by the controller during a commissioning period; and

providing at least one first operational received light intensity threshold for use during an operational period following the commissioning period.

144. A controller for particle detection system comprising one or more light sources and a receiver arranged so that light from the one or more light sources traverses an area to be monitored for particles and is received by the receiver, said controller being programmed to monitor for the occurrence of one or more predefined alarm and/or fault conditions based on at least one received light intensity threshold; said controller being adapted to perform a method as claimed in any one of claims 197 to 209.

145. A method of commissioning and operating a particle detection system, comprising:

arranging one or more light sources and a receiver so that light from the one or more light sources traverses an area to be monitored for smoke before being received by the receiver; and performing a method as claimed in any one of claims 197 to 207.

146. A particle detection system for monitoring a volume, the system including:

at least one transmitter adapted to transmit one or more light beams;

a receiver adapted to receive said one or more light beams from at least one transmitter after traversing the volume being monitored;

a controller adapted to determining the presence of particles in the volume on the basis of the output of the receiver; and

means for determining a light output intensity of a transmitter for use in particle detection.

147. A transmitter for a particle detection system, including:

at least one light source to generate a beam of light at least one wavelength;

a housing in which the light source is mounted;

one or more filters selectively mountable with respect to the light source for selectively attenuating the beam of light.

148. A receiver for a particle detection system:

at least one light sensor for measuring the level of light received from a transmitter of a particle detection system;

a controller to selectively activate the light sensor to receive signals.

149. A test filter comprising at least one sheet like filter element, and being configured to transmit light in a first wavelength band transmitted by the particle detector to a different extent than light in a second wavelength band transmitted by the particle detector.

150. A receiver in a particle detector, said receiver including:

at least one sensor element adapted to receive light and output a signal indicative of the received light intensity at plurality of spatial positions; and

an optical system including at least one wavelength selective element configured to receive light at a plurality of wavelengths simultaneously and transmit light in two or more wavelength bands to the one or more sensor elements such that an output signal indicative of the received light intensity in the at least two wavelength bands can be obtained.

151. A projected beam particle detector including a receiver as claimed in claim 150.

152. A projected beam particle detector as claimed in claim 151 which includes a polychromatic light source.

153. A transmitter for a beam detector including a light source configured to emit light in a plurality of wavelength bands corresponding substantially to respective passbands of filter of the receiver of the beam detector.

154. A smoke detector including:

a transmitter adapted to emit a light beam;

a receiver having a light sensor with a plurality of sensor elements, for detecting the light beam, each of the sensor elements being adapted to generate an electrical signal related to the intensity of light impinging upon it;

the transmitter and received being arranged such that at least a portion of a light beam from the transmitter is received by the receiver;

a beam diffusing optics located in a path of travel of the light beam to the receiver, for forming a diffused image of the light beam on the light sensor, and

a controller that processes electrical signals generated by a plurality of the sensor elements to determine the intensity of the received beam, and apply alarm and/or fault logic to the intensity data to determine if a predetermined condition is fulfilled, and initiate an action if the predetermined condition is fulfilled.

155. A smoke detector as claimed in claim 154 wherein the beam diffusing optics includes a lens which focuses the light beam at a point which is not coincident with the sensor.

156. A smoke detector as claimed in claim 154 or 155 wherein the beam diffusing optics include a diffuser which may be placed between the transmitter and the light sensors.

157. A smoke detector as claimed in claim 154 and 156 wherein diffused image of the beam covers a plurality of sensor elements on the sensor of the receiver.

158. A smoke detector as claimed in claim 157 wherein the diffused beam covers between 2 and 100 elements.

159. A smoke detector as claimed in claim 158 wherein the diffused beam covers between 4 and 20 sensor elements.

160. A smoke detector as claimed in claim any one of claims 154 to 159 wherein the diffused image of the beam is preferably larger than a sharply focused image of the beam would be.

161. A smoke detector as claimed in any one of claims 154 to 160 wherein the controller is configured to combine received signals from a plurality of sensor elements to determine the received light level.

162. A smoke detector as claimed in claim 161 wherein the measured light level from a plurality of sensor elements are added.

163. A smoke detector as claimed in claim 162 wherein the measured light level from a plurality of sensor elements are added in a weighted sum.

164. A smoke detector as claimed in any one of claims 154 to 163 wherein the controller determines a centre-of-signal position corresponding to an image of a beam on the light sensors, and weight the signal from each sensor element according to a distance between each sensor and the centre-of-signal position.

165. A smoke detector as claimed in any one of claims 154 to 164 wherein the transmitter transmits a beam of light having components in two or more wavelength bands.

166. A method for detecting smoke, including:

transmitting a light beam from a transmitter to a receiver having a sensor comprising multiple sensor elements;

arranging a receiver so that it receives the beam;

forming a diffused image of the light beam on the sensor;

generating electrical signals related to the intensity of the received light level detected by at least those sensor elements of the multiple sensor elements on which the beam impinges;

determining the intensity of the received beam based on a plurality of the signals;

applying an alarm and/or fault logic to the received determined intensity; and

initiating an action if a predetermined alarm and/or fault condition is determined.

167. A method as claimed in claim 166 wherein the step of forming a diffused image of the beam comprises:

defocusing the light beam such that it is focused at a position that is not coincident with the light sensor.

168. A method as claimed in claim 166 or 167 wherein the step of diffusing the beam includes:

placing a diffuser between the transmitter and the sensor.

169. A method as claimed in claim any of claims 166 to 168 wherein the step of determining the intensity of the received beam includes:

combining a plurality of the received signals in a weighted in the combination.

170. A method as claimed in claim 169 wherein the method include:

determining a centre of signal position of the diffused image of the beam and weighting the signals according to the distance of their corresponding sensor element from the centre of signal position.

171. A component for a particle detection system including:

a first processor adapted to intermittently receive data from an image capture device and to process said data;

a second processor communicatively coupled with the first processor and adapted to selectively activate the first processor.

172. A component as claimed in claim 171 wherein the second processing device is configured to perform one or more of the following functions of the particle detection system:

communication with an external data communication system connected to the particle detector;

control of one or more interface components of the system;

monitoring of a fault condition of the component.

173. A method as claimed in either or claims 171 or 172 wherein the second processor is of lower power consumption than the first processor.

175. A method in a particle detection system including:

monitoring an activation period of a first processor using a second processor;

activating the first processor in response to a signal from the second processor; and

performing one or more data processing steps with the first processor.

176. A method as claimed in claim 175 wherein the method includes deactivating the first processor upon completion of one or more processing tasks.

177. A method as claimed in claim 175 to 176 wherein the first processor is configured to process video data from a receiver of the particle detection system.

178. A method as claimed in any of claims 175 to 177 wherein the method includes:

determining an activation period of the first processor.

179. A method as claimed in claim 178 wherein the step of determining an activation period includes , analysing a series of images and determining an illumination pattern of a light source in the images.

180. A method as claimed in claim 175 to 179 which includes activating the first processor substantially continuously during a commissioning period

181. A light source for a particle detector, including:

at least one light emitter for emitting at least one beam of light for illuminating a part of a region being monitored;

a battery for supplying electrical power to the light source;

a battery monitor for measuring at least one of the voltage of the battery or its current output;

a controller configured to, control the illumination of at least one light emitter of the light source and to receive at least one of, the voltage of the battery or its current output, and to determine a valve indicative of a remaining expected battery life.

182. An environmental monitoring system including:

a beam detector subsystem including at least one transmitter adapted to emit one or more beams of light across a region being monitored and at least one receiver, adapted to receive at least one beam of light emitted by a transmitter;

at least one additional environmental monitor adapted to sense an environmental condition associated with the region being monitored and to communicate an output, via an optical communication channel, to a receiver of the beam detector subsystem.

183. A beam detection system comprising:

a plurality of beam detectors;

at least one controller in data communication with the detectors and receiving an output from each of said beam detectors, said controller being configured to correlate the output of at least a pair of beam detectors which are spatially substantially spatially coincident for at least part of their beam length and in the event that a predetermined correlation condition exists determining that either particle detection event or a fault condition has occurred.

184. A method of operating a particle detection system including plurality of beam detectors having beams that can substantially coincident at least one point, the method including:

receiving an output from the plurality of beam detectors,

determining if a correlation condition exists between at least two of the outputs, and

if a predetermined correlation condition exists; determining either a particle detection event or false alarm event has occurred according to predetermined particle detection and/or fault logic.

184. A beam detector including at least one transmitter arranged to emit at least one beam of radiation across a volume being monitored, and receiver arranged to receive at least one beam of radiation, a controller configured to receive an output from the receiver and process the output to determine whether particles are present in the volume, the beam detector being adapted to implement a method as claimed in any one of the preceding claims.

185. A beam detector including at least one transmitter arranged to emit at least one beam of radiation across a volume being monitored, and receiver arranged to receive at least one beam of radiation, a controller configured to receive an output from the receiver and process the output to determine whether particles are present in the volume, wherein the transmitter is a transmitter as claimed in any one of the preceding claims.

186. A beam detector including at least one transmitter arranged to emit at least one beam of radiation across a volume being monitored, and receiver arranged to receive at least one beam of radiation, a controller configured to receive an output from the receiver and process the output to determine whether particles are present in the volume, wherein the receiver is a receiver as claimed in any one of the preceding claims.

187. A beam detector including at least one transmitter arranged to emit at least one beam of radiation across a volume being monitored, and receiver arranged to receive at least one beam of radiation, a controller configured to receive an output from the receiver and process the output to determine whether particles are present in the volume, wherein the transmitter includes an emitter or light source as claimed in any one of the preceding claims.

188. A beam detector including at least one transmitter arranged to emit at least one beam of radiation across a volume being monitored, and receiver arranged to receive at least one beam of radiation, a controller configured to receive an output from the receiver and process the output to determine whether particles are present in the volume, wherein the receiver includes an sensor or optical arrangement as claimed in any one of the preceding claims.

189. A particle detection system including;

at least one light source adapted to illuminate a volume being monitored, said illumination including a pulse train including a plurality of pulses, said pulse train being repeated with a first period;

a receiver having a field of view and being adapted to receive light from at least one light source after said light has traversed the volume being monitored and being adapted to generate signals indicative of the intensity of light received at regions within the field of view of the receiver, said receiver being configured to receive light from the at least one light source in a series defined by an exposure time and receiving frame rate;

a processor associated with the receiver adapted to process the signals generated by the receiver, wherein the pulses with the pulse train emitted within each plurality of pulses has a temporal position that is related to the receiving frame rate.

190. A particle detector as claimed in claim 189 wherein at least one pulse in the pulse train has a duration about half the exposure time.

191. A particle detector as claimed in either of claims189 or 190 wherein the period of repetition of the pulse train is substantially longer than the period between temporally adjacent frames.

192. A particle detector as claimed in any one of claims189 to 191 wherein the frame rate is in any one of the following ranges: 100fps-1500fps, 900fps-1100fps, 500fps to 1200fps.

193. A particle detector as claimed in any one of claims189 to 192 wherein the frame rate is about 1000f ps.

194. A particle detector as claimed in any one of claims189 to 193 wherein the duration of a pulse is between 1μs and 100μs.

195. A particle detector as claimed in any one of claims189 to 194 wherein the duration of a pulse is about 50μs.

196. A particle detector as claimed in any one of claims189 to 195 wherein the exposure time is between 2 and 200Ds.

197. A particle detector as claimed in any one of claims189 to 196 wherein the exposure time is about 100DS.

198. A particle detector as claimed in any one of claims189 to 197 wherein the pulse train includes at least one synchronisation pulse.

199. A particle detector as claimed in any one of claims 189 to 198 wherein the pulse train includes at least one pulse at a first wavelength.

200. A particle detector as claimed in any one of claims189 to 199 wherein the pulse train includes at least one pulse at a second wavelength.

201. A particle detector as claimed in any one of claims189 to 200 wherein the pulse train includes at least one data pulse.

202. A particle detector as claimed in any one of claims'! 89 to 201 wherein the frame rare and temporal spacing between each of the pulses are selected such in at least a first time period that there is changing phase difference between them.

203. A particle detector as claimed in any one of claims189 to 202 wherein the frame rate and temporal spacing between each of the pulses are selected the temporal spacing between each of the pulses is such that each of the pulses in a pulse train substantially fall within a respective exposure.

204. A method in a particle detection system including;

at least one light source adapted to illuminate a volume being monitored,

a receiver having a field of view and being adapted to receive light from at least one light source after said light has traversed the volume being monitored and being adapted to generate a series of frames indicative of the intensity of light received at regions within the field of view of the receiver, and

a processor associated with the receiver adapted to process the signals generated by the receiver, and provide an output; said method including:

determining a number of light sources from which the receiver is receiving light.

205. A method as claimed in claim 204 which further includes:

analysing a plurality of frames output by the receiver to determine the number of light sources.

206. A method as claimed in any one of claims 204 to 205 wherein the method includes;

operating the receiver at a high frame rate during the step of determining the number of light sources; and

subsequently operating the receiver at a second lower frame rate.

207. A method as claimed in any one of claims 204 to 206 wherein the method includes:

analysing a plurality of frames from the receiver to identify regions having relatively high variation in received light level between frames to identify candidate positions within the field of view of the receiver.

208. A method as claimed in claim 207 wherein the method includes: comparing the variation in received light levels for a position between frames to a threshold.

209. A method as claimed in any one of claims 204 to 208 wherein the method includes:

attempting to synchronise the receiver to a predetermined transmission pattern expected from a transmitter for a candidate position,

and in the event synchronisation is successful determining the candidate position is receiving light from a transmitter.

210. A method as claimed in any one of claims 204 to 209 wherein the method includes:

attempting to synchronise the receiver to a predetermined transmission pattern expected from a transmitter for a candidate position,

and in the event synchronisation is unsuccessful determining the candidate position is not receiving light from a transmitter.

211. A method as claimed in any one of claims 204 to 210 wherein the step of attempting to synchronise the receiver to a predetermined transmission pattern includes:

capturing a plurality of at least partial frames including the candidate location;

comparing the received frames to an expected pattern of received light corresponding to a pulse train emitted by a transmitter;

attempting to synchronise to the received pattern using a phase locked loop.

212. A method as claimed in any one of claims 204 to 211 wherein the step of comparing the received frames to an expected pattern of received light corresponding to a pulse train emitted by a transmitter; include

determining a reference level of received light representing a time when no pulse is received for the candidate position;

comparing a light level received from each pulse to the reference level and if the difference exceeds a predetermined threshold, determining a pulse is received.

213. A method as claimed in any one of claims 204 to 212 wherein the step of comparing the received frames to an expected pattern of received light corresponding to a pulse train emitted by a transmitter; includes

determining whether a series of pulses corresponding to an expected pattern is received.

214. A method as claimed in any one of claims 204 to 213 wherein the method includes, comparing the determined number of light sources with a predetermined number of light sources; and in the event that the determined number does not match the predetermined number either:

repeating the determining step; or

signalling a fault.