Patent ID: 7436515

Claim:
An apparatus for the detection of fluid borne particles which comprises: a zone through which a fluid to be analyzed flows, in use; a source of illumination to illuminate/irradiate fluid borne particles present in said zone; and a detector to detect light from the particles as an indicator of the presence or characteristics of the particles, wherein the apparatus comprises a pair of opposed concave reflective surfaces and the zone is between these surfaces, the apparatus having two sources and two detectors, the first of the two detectors detecting a first wavelength band and the second of the two detectors detecting a second wavelength band that is narrower than the first band and falls within the first band, the first source illuminating/irradiating within a wavelength band that is below the wavelength detecting band of the first detector and the second detector, and the second source illuminating/irradiating with a wavelength band that is within the wavelength detecting band of the first detector.