An optical engine for use in a bench top flow cytometer, the optical engine comprising a set of lasers; a different set of beam shaping optics for each laser, wherein each set comprises two lenses to adjustably focus light horizontally along an x-axis to a same horizontal position and vertically along a y-axis to a different vertical position along a same plane; collection optics for collecting fluorescence from the flow cell; filtration optics that filter the collected fluorescence from the flow cell into different detection channels according to wavelength ranges; and a detector for each detection channel that converts the filtered fluorescence to electrical signals, wherein electrical signals are processed so that the fluorescence from each laser at the different vertical positions is distinguished at the same detector.