Laser noise detection and mitigation in particle counting instruments

An optical particle analyzer comprising:

• a laser for generating a beam of electromagnetic radiation;
• a flow chamber for flowing a fluid containing particles along a flow direction and through the beam of electromagnetic radiation, thereby generating scattered or emitted electromagnetic radiation;
• an optical collection system for collecting and directing said scattered or emitted electromagnetic radiation from a viewing region onto a plurality of detector elements;
• said detector elements for detecting said electromagnetic radiation and generating independent output signals;
• and wherein each detector element is positioned to receive scattered or emitted electromagnetic radiation from a different portion of said viewing region;
• and
• a signal processing system operationally connected to said detector elements for:
• comparing output signals from at least two different detector elements to discriminate output signals corresponding to a particle detection event from output signals corresponding to a laser noise event;
• analyzing said output signals corresponding to said detection event;
• and
• identifying said laser noise event;
• wherein said laser noise event is identified when the output signals of each of at least two non-adjacent detector elements is independently equal to or greater than a threshold value.

A method of distinguishing particle scattering from laser noise in an optical particle analyzer, said method comprising the steps of:

• providing a fluid flow having particles to said optical particle analyzer;
• exposing said fluid flow to a beam of electromagnetic radiation from a laser,
• wherein interaction between said fluid flow and said beam generates scattered or emitted electromagnetic radiation;
• collecting and directing said scattered or emitted electromagnetic radiation from a viewing region onto a plurality of detector elements;
• wherein each detector element is positioned to receive said scattered or emitted electromagnetic radiation of from a different portion of said viewing region;
• detecting said electromagnetic radiation directed onto said plurality of detector elements, wherein each of said detector elements generates independent output signals;
• comparing output signals from at least two nonadjacent different detector elements to discriminate output signals corresponding to a particle detection event from output signals corresponding to a laser noise event;
• and
• identifying said laser noise event;
• wherein said laser noise event is identified when the output signals of each of at least two non-adjacent detector elements is independently equal to or greater than a threshold value.

A method for detecting particles in a fluid flow, said method comprising the steps of:

• providing said fluid flow having said particles;
• exposing said fluid flow to a beam of electromagnetic radiation from a laser, thereby generating scattered or emitted electromagnetic radiation;
• collecting and directing said scattered or emitted electromagnetic radiation from a viewing region onto a plurality of detector elements;
• wherein each detector element is positioned to receive said scattered or emitted electromagnetic radiation from a different portion of said viewing region;
• detecting said electromagnetic radiation directed onto said plurality of detector elements, wherein each of said detector elements generates independent output signals;
• comparing output signals from at least two different detector elements to discriminate output signals corresponding to a particle detection event from output signals corresponding to a laser noise event;
• analyzing output signals corresponding to said detection event, thereby detecting said particles in said fluid flow;
• identifying said laser noise event;
• storing said output signals for all detector elements for a preselected time period;
• and
• analyzing said stored output signals in the event that no laser noise event is identified or discarding said stored output signals in the event that said laser noise event is identified.

A method for detecting particles in a fluid flow, said method comprising the steps of:

• providing said fluid flow having said particles;
• exposing said fluid flow to a beam of electromagnetic radiation from a laser, thereby generating scattered or emitted electromagnetic radiation;
• collecting and directing said scattered or emitted electromagnetic radiation from a viewing region onto a plurality of detector elements;
• wherein each detector element is positioned to receive said scattered or emitted electromagnetic radiation from a different portion of said viewing region;
• detecting said electromagnetic radiation directed onto said plurality of detector elements, wherein each of said detector elements generates independent output signals;
• comparing output signals from at least two different detector elements to discriminate output signals corresponding to a particle detection event from output signals corresponding to a laser noise event;
• analyzing output signals corresponding to said detection event, thereby detecting said particles in said fluid flow;
• identifying said laser noise event;
• and
• upon identification of a laser noise event, waiting for a preselected time period prior to identifying a particle detection event.