Patent ID: 7268881

Claim:
A light scattering detector device, comprising: a detection cell to accept particles suspended in a gas stream and permit a polarized beam to pass through a trajectory of the particles and gas stream; a sample light detector disposed to detect light scattered in the detection cell; a light trap that accepts the polarized beam after it passes through the detection cell, the light trap including, an elongated housing through which the polarized beam passes, and light absorptive material within the elongated housing; and an absorptive filter disposed to substantially align the electric field vector of the polarized beam with the plane of incidence defined by the polarized beam and the normal to said absorptive filter, and disposed to intersect the polarized beam at an angle of incidence that approximates Brewster's angle; a reference light detector to detect light passing through said absorptive filter; and a noise cancellation circuit to sum a reference signal corresponding to light received by said reference light detector and a sample signal corresponding to light received by said sample light detector, the noise cancellation circuit further comprising one or more potentiometers that may be adjusted to balance said reference signal and said sample signal.