Particle Counter With Improved Image Sensor Array

Abstract

A particle counter for optically detecting an unconstrained particle of less than one micron in size suspended in a flowing liquid includes a sample chamber having a fluid inlet and a fluid outlet; a laser module producing a laser beam; a beam shaping optical system providing a multiple laser beam pattern in the sample chamber; and a CMOS optical detector located to detect light scattered by the particles in the sample chamber. The particle counter has a particle sensing area within the sample chamber in which the intensity of light is at least 10 Watts/mm 2 , the sensing area having an area of 0.5 square mm or more. The detector has thirty or more detector array elements. In the preferred embodiment, the laser optical system reflects and refocuses the laser beam to effect multiple passes of the same laser beam through the sensing area.

1 . An optical particle counter for optically detecting single unconstrained particles of less than one micron in size suspended in a flowing fluid, said optical particle counter comprising:
 a sample chamber having a fluid inlet and a fluid outlet;   a source of light;   a light-directing optical system directing said light through said sample chamber;   an optical collection system located to collect light scattered by said single unconstrained particles of less than one micron in size in said fluid flowing through said sample chamber; and   a detection system located to detect light collected by said optical collection system, said detection system including an optical detector producing an electric signal characteristic of the number of said single unconstrained particles of less than one micron in size which are detected;   wherein said optical detector comprises a CMOS imager.   
   
   
       2 . A device as in  claim 1  wherein said fluid is a liquid. 
   
   
       3 . A device as in  claim 1  wherein said source of light comprises a laser. 
   
   
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       5 . A device as in  claim 1  wherein said, said optical collection system has an optical axis, and, in a direction along said optical axis opposite to the direction of said detector from said sample chamber, said sample chamber has no sample chamber wall from which stray light sufficient to create optical noise can enter said detector. 
   
   
       6 . A device as in  claim 1  wherein said detection system comprises a microprocessor. 
   
   
       7 . A device as in  claim 1  wherein said detection system comprises a computer. 
   
   
       8 . A device as in  claim 3  wherein said light-directing optical system comprises redirection optics for directing and refocusing said laser through said sample chamber a plurality of times. 
   
   
       9 . A device as in  claim 8  wherein said redirection optics comprise a plurality of mirrors. 
   
   
       10 . A device as in  claim 9  wherein said plurality of mirrors are located to direct said laser beam through said sample chamber 10 or more times. 
   
   
       11 . A device as in  claim 10  wherein said plurality of mirrors are located to direct said laser beam through said sample chamber 25 or more times. 
   
   
       12 . A device as in  claim 8  wherein said light collecting system has an optical axis, and said plurality of beam passes through said sample chamber lie in a plane perpendicular to said optical axis. 
   
   
       13 . A device as in  claim 3  wherein said source of light comprises a plurality of lasers producing a plurality of laser beams, and said light-directing optical system comprises an optical system for directing said plurality of laser beams through said sample chamber. 
   
   
       14 . A device as in  claim 1  wherein said optical collection system has an optical axis, and said fluid flow is in a direction substantially parallel to said optical axis. 
   
   
       15 . A device as in  claim 1  wherein said liquid is water, and said sample chamber comprises a fused silica glass window or lens. 
   
   
       16 . A method of detecting single unconstrained particles of less than one micron in size in a flowing fluid, said method comprising:
 flowing said fluid containing said single unconstrained particles of less than one micron in size;   directing a laser beam through said fluid flow;   collecting light scattered by said single unconstrained particles of less than one micron in size in said fluid; and   detecting said collected light with a CMOS imager and outputting a signal from said CMOS imager that is characteristic of a parameter of said single unconstrained particles of less than one micron in size.   
   
   
       17 . A method as in  claim 16  wherein said directing comprises passing said laser beam through said fluid flow and refocusing the beam a plurality of times. 
   
   
       18 . A method as in  claim 16  wherein said passing comprises passing said laser beam through said fluid flow three or more times in the same plane. 
   
   
       19 . A method as in  claim 18  wherein said collecting comprises collecting said scattered light about an optical axis perpendicular to said plane. 
   
   
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       36 . A method for optically detecting single unconstrained particles of less than one micron in size suspended in a flowing fluid, said method comprising:
 flowing said fluid containing said single unconstrained particles of less than one micron in size;   directing a plurality of laser beams through said fluid flow;   collecting light scattered by said single unconstrained particles of less than one micron in size in said fluid; and   detecting said collected light and outputting a signal characteristic of a parameter of said single unconstrained particles of less than one micron in size; wherein said plurality of laser beams define a plane with each beam passing through a different portion of said plane and said collecting comprises collecting said light about an optical axis perpendicular to said plane.   
   
   
       37 . A method as in  claim 36  wherein said directing comprises producing a laser beam, passing said laser beam through said fluid flow, and redirecting and refocusing said laser beam back through said fluid flow. 
   
   
       38 . A method as in  claim 37  wherein said redirecting comprises reflecting said laser beam. 
   
   
       39 . A method as in  claim 38  wherein said reflecting comprises reflecting said laser beam a plurality of times. 
   
   
       40 . A method as in  claim 39  wherein said directing comprises directing ten or more laser beams through said fluid flow, and said reflecting comprises reflecting said laser beam nine or more times. 
   
   
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       42 . A method as in  claim 36 , said sensing region having a cross-sectional area of 0.5 square millimeters or more in said plane. 
   
   
       43 . A method as in  claim 36  wherein said directing comprises producing a plurality of laser beams with a plurality of lasers and passing said plurality of laser beams through said fluid flow. 
   
   
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