Enhanced light collection in a flow cytometer.

A modified flow cell in a conventional flow cytometer is described. The refraction of light in the flow cell-to-air interface is analyzed. The analysis shows that much of the light that can be collected is refracted out of the collection optics. The efficiency of light collection is doubled by the addition of a plano-convex lens to the flow cell. Also, more stable operation of the flow cell is achieved with the addition of a secondary sheath.