Patent ID: 7483139

Claim:
A particle detector including: a chamber having a substantially high reflectivity substantially Lambertian surface and a radiation absorbing surface, and for receiving particles, radiation emitting means for emitting radiation into the chamber and directly irradiating the substantially high reflectivity substantially Lambertian surface, and radiation detecting means for detecting the effect of the particles on the radiation within the chamber, wherein the radiation detecting means is primarily for detecting absorption of the radiation by the particles, wherein the radiation detecting means has a wide viewing angle to receive radiation directly from a substantial portion of the high reflectivity Lambertian surface, wherein the radiation detecting means is located at the radiation absorbing surface, and wherein the detector further includes a second radiation detecting means primarily for detecting scattering of radiation by the particles, and wherein the second radiation detecting means is sensitive substantially only to radiation in a path between the second radiation detecting means and the radiation absorbing surface.