Optical design in a flow system for imaging cells

The imaging flow cytometer is an instrument that acquires the images of cells in a flow system. These images are analyzed for real-time cell classification and sorting. The optical units in the system perform the functions of laser beam focusing, cell detection, and cell imaging. The glass nozzle in which the cell stream flows introduces air-glass optical interfaces, resulting in optical aberrations that impair performance. This report describes the analysis of the optical aberrations in nozzles fabricated from a cylindrical glass capillary tube. Flat surfaces could be machined on the originally cylindrical surface to reduce the severity of these aberrations. The analysis shows that a nozzle with three flat surfaces is a feasible low-cost solution.