Fluorescence analysis of stained particles

Claim 1

In apparatus for effecting fluorescence analysis of particles, dyed with two different dyestuffs in a continuous flowthrough procedure, by suspending the particles in a carrier fluid, forming the particle-containing carrier fluid into a sample stream and encasing the sample stream in a sheath stream, conducting the resulting composite stream in laminar flow through an intensive laser light zone where fluorescent light pulses are generated by the laser light and emanate from the particles, and detecting and processing the flourescent light pulses in real time in an electronic evaluation system, the improvement comprising a focussing lens system for producing the laser light zone by focussing at least two laser beams of respectively different wavelengths, each wavelength being matched to a respectively different dyestuff or its fluorescence spectrum, on two points located at the center of the sample stream and spaced at a given distance apart along the path of the particle-containing fluid in the composite stream, said lens system being arranged to direct the laser beams normal to the sample stream with a slight divergence from one another, which divergence determines the spacing between the points at which the beams are focussed, and pivotally mounted deflection mirrors located upstream of said lens system for reflecting the laser beams onto said system and for adjusting the spacing between such points, and wherein said electronic evaluation system comprises means for correlating the fluorescent light pulses emanating from the two points on the basis of the spacing between the two points and of the flow speed of the stream, in order to evaluate only those pulses which correspond to the travel time of individual particles between the two points.