Abstract: A non-extractive optical particulate monitor for measuring particulate matter entrained in a flow within a smokestack, the monitor includes a light emission system which projects a beam of light into the smokestack, a light detection system positioned in a non co-linear relationship with the light emission system to receive and detect light scattered by the particulate matter in the smokestack, and a calibration system located between the light emission system and the light detection system to selectively enable light from the light emission system access to the light detection system without traveling through the flow structure for calibration of the monitor.

Abstract: A back scattering collector, comprising: a first spherical reflective surface; a second spherical reflective surface having an annular form defining a central aperture; a refractive element, the first and second reflective surfaces and the refractive element being aligned along an optical axis; a light excitation source for illuminating a volume for analysis; the first and second reflective surfaces having respective diameters which reflect light rays back scattered from the volume at least three times between the first and second reflective surfaces, a last one of the at least three refections directing the light rays through the refractive element; and, a photo detector, the refractive element focusing the light reflected light rays onto the photo detector. The second reflective surface can be formed on the convex side of a plano-convex lens, the refractive element being formed by a central portion of the lens. The distance between the reflective surfaces is adjustable.