end of a fiber optic 160 contained in a fiber optic housing 161 by a plano convex lens 108 closely situated to the emission source the closer the lens is to the source the more light it can capture a large lens with a short focal length would be ideal however if the optical housing 170 is too close to the emission source it infringes on the laser light path the optical housing 170 and the sample analyzer head chambers are coated with a black matte non reflecting or emitting paint assays described above are based upon type 1 disposable tips in which the reagent tag is on a matrix surrounded by the tip wall another type of assay is based on type 2 disposable tips which increases the sensitivity and decreases error in the assy with a type 2 tip a ligand is coupled to the matrix which ligand specifically binds the molecule of interest in a test sample as well as the reagent tag the reagent tag is the same as the molecule of interest but is labeled with a laser dye such as nn 382 this is a competitive assay in which an antibody b coupled to the matrix specifically recognizes and binds the test sample antigen b 1 flowing through the matrix as well as the reagent tag antigen b1 nn 382 in order to measure the amount of antigen b1 in a test sample a calibrated quantity of reagent tag is mixed with the test sample the amount of reagent tag added to the test sample is just enough to.