Instrument for measuring particle parameters

Abstract

Values for one or more particle properties, such as an aerosol asymmetry parameter g, can be measured directly using a detector that measures scattered light. The detector can comprise two or more diffusers coupled to optical sensors responsive to scattered light that is incident on the surfaces of the diffusers. One or more weighing functions can be obtained based on diffuser geometry. In an example, the diffusers correspond to quadrants of a circular toroid.

1 . An apparatus for radiation scattering measurements, comprising: 
 a plurality of diffusers situated along a detection axis and configured to receive respective portions of a light flux scattered from an optical axis that is substantially perpendicular to the detection axis; and    a corresponding plurality of light sensors coupled to a respective diffuser.    
   
   
       2 . The apparatus of  claim 1 , further comprising at least one optical barrier coupled to the plurality of diffusers so that the diffusers are substantially optically isolated from each other.  
   
   
       3 . The apparatus of  claim 1 , wherein the plurality of diffusers is defined by respective longitudinal portions of a circular toroidal solid that consists essentially of a translucent material.  
   
   
       4 . The apparatus of  claim 3 , wherein the translucent material is TEFLON.  
   
   
       5 . The apparatus of  claim 3 , wherein each of the diffusers is substantially a quadrant of the circular toroidal solid.  
   
   
       6 . The apparatus of  claim 2 , wherein the plurality of diffusers is defined by respective interior longitudinal portions of a substantially circular toroidal shell, wherein the shell includes a scattering exterior.  
   
   
       7 . The apparatus of  claim 6 , wherein each of the diffusers is substantially a quadrant of the toroidal shell.  
   
   
       8 . The apparatus of  claim 1 , wherein the plurality of diffusers is defined by quadrants of a longitudinal section of a circular cylinder.  
   
   
       9 . The apparatus of  claim 1 , further comprising at least one optical barrier coupled to the plurality of diffusers so that the diffusers are substantially optically isolated from each other.  
   
   
       10 . The apparatus of  claim 1 , further comprising: 
 a second plurality of diffusers situated along a second detection axis that is substantially perpendicular to the optical axis and configured to receive respective portions of a light flux scattered from the optical axis, wherein the first and second detection axes are substantially situated in a plane perpendicular to the optical axis; and    a corresponding second plurality of light sensors coupled to a respective diffuser of the second plurality of diffusers.    
   
   
       11 . The apparatus of  claim 10 , wherein the first detection axis and the second detection axis are substantially parallel.  
   
   
       12 . The apparatus of  claim 10 , wherein the first detection axis and the second detection axis are substantially perpendicular.  
   
   
       13 . The apparatus of  claim 1  further comprising a processor coupled to the plurality of sensors and configured to determine a scattering parameter.  
   
   
       14 . The apparatus of  claim 13 , wherein the scattering parameter is an aerosol asymmetry parameter.  
   
   
       15 . The apparatus of  claim 13 , wherein the scattering parameter is a scattering coefficient.  
   
   
       16 . A method of measuring an aerosol scattering parameter, comprising: 
 receiving a light flux scattered by an aerosol at a plurality of diffusers;    estimating magnitudes of portions of the scattered light flux received by each of the plurality of diffusers; and    determining the scattering parameter based on the estimated magnitudes.    
   
   
       17 . The method of  claim 16 , further comprising selectively patterning portions of an exterior of at least one of the diffusers based on a scattering parameter to be estimated.  
   
   
       18 . The method of  claim 16 , wherein the diffusers consist essentially of a light scattering solid.  
   
   
       19 . A measurement apparatus for determining a light scattering characteristic, comprising: 
 a plurality of diffusers coupled to respective sensors, wherein the sensors are coupled to produce respective sensor signals based on a scattered light flux and the sensors are configured to provide a selected weighing function response; and    a processor coupled to receive the sensor signals and determine the scattering characteristic.    
   
   
       20 . The apparatus of  claim 19 , wherein the diffusers are based on respective volumes of a light scattering material.  
   
   
       21 . The apparatus of  claim 19 , wherein the diffusers are based on respective light scattering surfaces at a diffuser perimeter.  
   
   
       22 . The apparatus of  claim 19 , wherein each of the plurality of diffusers corresponds to a longitudinal quadrant of a longitudinal section of a circular toroid.  
   
   
       23 . The apparatus of  claim 19 , wherein each of the plurality of diffusers corresponds to a longitudinal quadrant of a longitudinal section of a circular cylinder.