the liquid of a flow cytometer itself acts as an optical waveguide , thus transmitting the light to an optical filter / detector combination . this alternative apparatus and method for detecting scattered light in a flow cytometer is provided by a device which views and detects the light trapped within the optical waveguide formed by the flow stream . a fiber optic or other light collecting device is positioned within the flow stream . this provides enormous advantages over the standard light collection technique which uses a microscope objective . the signal - to - noise ratio is greatly increased over that for right - angle - scattered light collected by a microscope objective , and the alignment requirements are simplified .