Particle analyzer with spatially split wavelength filter

Abstract

A fluorescence particle analyzer includes a flow tube through which particles marked with different fluorochromes pass from a first location to a second location. Emissions from the first and second locations are respectively imaged at respective first and second filter elements so that emissions that reach a photodetector from said first location are primarily filtered by the first filter element, while emission that reach the same photodetector from the second location are primarily filtered by the second filter element. The first filter element is selected to preferentially transmit emissions from a first fluorochrome at the expense of emissions from a second fluorochrome, while the second filter element is selected to preferentially transmit emissions from the second fluorochrome at the expense of emissions from the first fluorochrome. The first location is illuminated by a laser that preferentially excites the first fluorochrome at the expense of the second fluorochrome, while the second location is illuminated by a laser that preferentially excites the second fluorochrome at the expense of the first fluorochrome. The photodetector output includes a first pulse that corresponds predominately to the quantity of the first fluorochrome in the particle; subsequently, a second pulse appears corresponding predominantly to the quantity of the second fluorochrome in the particle. The use of the two filters minimizes cross talk between the fluorochrome emissions in the photodetector output pulses.