Particle ID with narrow angle detectors

A method for identifying unknown particles that are present in a fluid, which includes interrogating particles by directing a light beam (104) through the fluid while flowing the fluid in a stream past the beam and detecting scattered light by a plurality of detectors (112) as a result of an event, which is when a particle passes through a detection zone (114) that lies along said beam, and recording the outputs of said detectors for an event to produce an eventvector, which includes producing multiple events for particles that are of a known first species to produce multiple eventvectors for that known first species, producing an event for an unknown particle of an unknown species to produce an eventvector for the unknown particle, and comparing the multiple eventvectors for said known first species to said eventvector for the unknown species to determine whether the unknown particle is of said known first species, characterized by:

• said step of flowing the fluid includes flowing the fluid through locations along said light beam that are not in said detection zone, so light is scattered by particles passing through locations along said beam that are not in said detect zone;
• said step of detecting scattered light by a plurality of detectors, includes detecting, by each of said detectors, only light that is scattered from said detect zone but not light that is scattered from locations along said light beam that are outside said detect zone.

Apparatus for identifying a species of particle that is present in fluid that is to be analyzed, which includes means (102) for generating a light beam (104) and a plurality of detectors (112) that each detects light dispersed from a detection zone (114) lying along the beam when a particle enters the detection zone and thereby produces an event, the detect zone being surrounded by said fluid, and the outputs of the detectors for an event constituting an eventvector for the event, the apparatus including a memory (116) that stores a plurality of known-particle patterns (210) for particles of each of a plurality of known species, where each known-particle pattern comprises a group (202, 204, 206) having multiple eventvectors that were each recorded when a different particle of the same known species of particle entered the detection zone to create an event and said apparatus includes pattern recognition means (118) for indicating whether or not an unknown eventvector (236) produced by an event of an unknown particle, is sufficiently similar to the eventvectors of one of said known-particle patterns to indicate that the unknown particle that produced the unknown eventvector is of one of said known species, characterized by:

• said detectors are each constructed to detect light scattered from said detect zone but not from locations along said beam that are outside said detect zone.