CELL-DYN 3000 System Operator’s Manual 3-99140240E — May 1995Chapter 3 Principles of OperationThe light source is a vertically polarized 5 mW helium-neon laser with awavelength of 632.8 nm. The laser beam passes through a cylindricallens which changes the shape from a circle to an ellipse. The beam isthen directed through a 125 μm slit which blocks the weaker outer edges.This process yields a uniformly intense beam approximately 80 μm wide.Consequently, the cell stream may wander slightly in the flow cell andyet still be exposed to the same light intensity. An imaging lens centersthe focused laser beam onto the quartz flow cell.The WBC metering syringe slowly injects 78 μL of the WBC dilutioninto the sheath stream in the WBC flow cell. The sample ishydrodynamically focused into a small stream approximately 30 μm indiameter. This focused stream aligns the diluted cells in single file asthey pass through the sensing region, which allows them to be analyzedone at a time.Figure 3.3: Optical BenchSince the average WBC is much smaller than the focused laser beam, thecells do not scatter much laser light. If the remaining so-called axial lightwere allowed to reach the 0° detector, it would saturate the electronics.Therefore, it is blocked from the detector by the obscuration bar. Theforward angle scatter is directed to a perforated mirror. The 0° lightscatter passes through the mirror to the 0° photodiode detector. The 10°light scatter is deflected off the mirror to the 10° photodiode detector.90° LightScatterPMT90° DepolarizedLight ScatterPMT Polarizer(Horizontal)Helium-Neon Laser(632.8 nm) PolarizedVerticallyBeamSplitter10° LightScatterPhotodiode0° LightScatterPhotodiodePerforatedMirrorObscurationBarWBCFlowCellImagingLensFrontSurfaceMirrorCylindricalLens700 μmSlitFrontSurfaceMirror125 μmVerticalSlit
