An optical engine its use in a bench top flow cytometer, the optical engine having a set of lasers, each focused horizontally along an x-axis to a same horizontal position and vertically along a y-axis to a different vertical position along a same excitation plane of a flow cell, a set of optics that separate fluorescence of a same wavelength range into different locations in a focal plane of collection optics according to the different lasers by which the fluorescent light is excited; and a detector that selectively detects light from the different locations thereby distinguishing between fluorescence emitted within the same wavelength range as excited by the different lasers.