Apparatus for simultaneously measuring large and small particle size distribution

An apparatus for measuring a wide range of particle sizes in a sample fluid comprising:

• first means for irradiating the sample fluid with a first light source along a first predetermined optical axis;
• second means for irradiating the sample fluid with a second light source having a different wavelength than the first light source along a second predetermined first optical axis;
• first detector means for measuring the optical intensities of the first light source after interaction with the particles in the sample fluid at predetermined angles off the optical axis at predetermined angles off the second optical axis;
• second detector means for measuring the optical intensities of the second light source after interaction with the particles in the sample fluid;
• means for measuring the intensity of the irradiating first light source simultaneously with the measurement of the first detector and providing a
• means for measuring the intensity of the irradiating second light source simultaneously with the measurement of the second detector and providing a representative signal;
• means for compensating the first detector measured optical intensities with the representative signal of the first light source;
• means for compensating the second detector measured optical intensities with the respective signals of the second light source, and
• means for calculating the particle size distribution in the sample fluid based on the compensated first and second measured light intensities.

In an apparatus for measuring particle size distribution comprising a larger diameter particle-detecting optical system containing a laser beam-irradiating means for irradiating a sample vessel, in which a medium with sample particles are dispersed with laser beams and a ring-shaped detector for measuring optical intensities of laser beams having respective scattering angles diffracted or scattered by said sample particles and a smaller particle-detecting optical system containing a monochrome light-irradiating means for irradiating said sample vessel with monochrome light and a group of photosensors for measuring optical intensities of said monochrome light having the respective scattering angles diffracted or scattered by the sample particles, the improvement comprising:

• a first transmitted beam-measuring photosensor for measuring an optical intensity of a laser beam transmitting through the sample vessel without being diffracted or scattered by the sample particles;
• a second transmitted beam-measuring photosensor for measuring an optical intensity of a monochrome light transmitting through the sample vessel without being diffracted or scattered by the sample particles;
• compensating means for calculating a transmission factor of said light and that of said monochrome light beam, respectively, on the basis of the data measured by means of said first transmitted beam-measuring photosensor and said second transmitted beam-measuring photosensor to compensate the data measured by means of said ring-shaped detector and said group of photosensors by a quantity corresponding to said transmission factors, and
• particle size distribution-calculating means for calculating a particle size distribution of the sample particles from the compensated data of measurement on the basis of a theory of the Fraunhofer diffraction or the Mie scattering.

In an apparatus for measuring a particle size distribution, including a large diameter particle-detecting optical system containing light-irradiating means for irradiating a sample vessel, in which a medium with sample particles are dispersed, with a laser beam and a detector for measuring optical intensities of laser beams having respective scattering angles diffracted or scattered by said sample particles and a smaller particle-detecting optical system containing monochrome light-irradiating means for irradiating said sample vessel with monochrome light and a group of photosensors for measuring optical intensities of monochrome light having respective scattering angles diffracted or scattered by the sample particles, the improvement comprising:

• a first beam splitter for separating a portion of the laser beams before they are incident upon the sample vessel;
• a first monitoring photosensor for measuring an optical intensity of the laser beams separated by said first beam splitter;
• a second beam splitter for separating a portion of the monochrome light before it is incident upon the sample vessel;
• a second monitoring photosensor for measuring an optical intensity of the monochrome light separated by said second beam splitter;
• means for receiving data measured by means of said ring-shaped detector, data measured by means of said group of photosensors, and data measured by means of said respective monitoring photosensors;
• compensating means for compensating said data measured by means of the ring-shaped detector and the group of photosensors depending upon said data measured by the respective monitoring photosensors at the same point of time as when the above described data are measured, and
• particle size distribution-calculating means for particles from the compensated data of measurement on the basis of a theory of the Fraunhofer diffraction or the Mie scattering.