Coincidence arbitration in a flow cytomery sorting system

A particle detecting and sorting apparatus having a detection station for asynchronously providing a set of data signals manifesting the detection and various parameters of a plurality of particles flowing in a liquid stream containing said plurality of particles, and a sorting station having means, responsive to a droplet signal having a certain droplet rate, for breaking said liquid stream into a series of droplets, only certain ones of which contain said detected particles and means for sorting said droplets into various categories, said apparatus further having logic means for detecting coincidences of particles at said sorting station comprising:

• means, responsive to said data signals, for providing a series of category signals, in synchronism with said droplet signal and at a rate greater than said certain droplet rate, only one of said category signals manifesting a detected particle at any given time;
• means for storing a plurality of successive category signals;
• and
• means, coupled to said means for storing, for detecting, for each one category signal provided, a coincidence between said one category signal and those category signals occurring within a finite time before and after said one category signal and for selectively aborting the sorting of a droplet associated with said one category signal having a detected coincidence.

A method of detecting and sorting a plurality of different particles flowing in a liquid stream, comprising the steps of:

• detecting each particle in said stream and providing a series of asynchronously occurring particle signals manifesting the detection of unidentified particles and a plurality of identified particles;
• forming said stream into a series of sortable droplets in response to a sort signal, selected ones of said droplets containing said particles;
• delaying and synchronizing said particle signals to the formation of said droplets;
• detecting the occurrence of coincidences between said particle signals within a certain time period surrounding the formation of each droplet and whether or not said coincidence is between the same identified particles;
• and
• providing said sort signal each time said particle signal manifests an identified particle, unless a coincidence with a different identified, or an unidentified, particle is detected.