Method for measuring the size and velocity of spherical particles using the phase and intensity of scattered light

In a system for measuring parameters associated with particles, droplets and the like employing laser light scattering, an apparatus for detecting errors due to mixed components in said scattering, comprising:

• laser generation means for generating first and second Guassian laser beams and directing said beams to cross forming a sample volume;
• collection means for collecting the scattered light due to said particles, droplets and the like passing through said sample volume, and converting said scattered light into electrical signals;
• phase detection means coupled to said collection means for determining the phase and amplitude of said signals;
• sizing means coupled to said phase detection means for determining the size of said particle, droplet and the like from the phase of said signals, said sizing means further comparing said amplitude to predefined upper and lower amplitude limits for the particle size, such that if said amplitude is outside said limits an error is detected and said measurement is considered invalid.

In an apparatus for measuring or sensing parameters associated with particles, droplets and the like employing first and second Gaussian laser beams caused to cross to establish an interference pattern forming a sample volume, a method for determining the change in the effective cross-section of said sample volume, comprising the steps of:

• (a) generating said first and second Gaussian laser beams and directing said beams to cross at a known angle, said interference pattern having an apparent spacing defined as .delta.;
• (b) collecting the scattered signal created by said particles, droplets and the like passing through said sample volume;
• (c) determining the maximum (N.sub.max) and minimum (N.sub.min) number of interference fringes crossed by said particles, droplets and the like, of a class of particles having the same diameter passing through said sample volume wherein N.sub.min is the number of fringes detected to produce a signal reliable enough for later use;
• (d) determining the change in the effective cross-section of said sample volume due to size variations of said particles, droplets and the like passing through said interference pattern, said change in said cross-section being defined as:
• T(d)=.delta.[N.sub.max (d).sup.2 -N.sub.min (d).sup.2 ].sup.1/2
• where:
• T=sample volume cross-section
• d=diameter of said particle, droplet and the like
• whereby the effective apparent cross-section of said sample volume is determined for a class of said particles, droplets and the like having a diameter d.

In a system for measuring or sensing parameters associated with particles, droplets and the like employing laser scattering, an apparatus for determining the change in the effective cross-section of two crossed laser beams forming a sample volume, comprising:

• laser generation means for generating first and second Gaussian laser beams and directing said beams to cross at a known angle (.gamma.), said crossed beams forming an interference pattern defining said sample volume, said interference pattern having an apparent spacing (.delta.);
• collection means for collecting the scattered signal created by said particle, droplet and the like passing through said sample volume;
• circuit means coupled to said collection means for determining the maximum (N.sub.max) and minimum (N.sub.min) number of interference fringes crossed by said particles, droplets and the like, of a class of particles having the same diameter passing through said sample volume;
• said circuit means further determining the change in the effective cross-section of said sample volume due to size variations of said particles, droplets and the like passing through said interference pattern, said change in said cross section being defined as:
• T(d)=.delta.[N.sub.max (d).sup.2 -N.sub.min (d).sup.2 ].sup.1/2
• where:
• T=sample volume cross-section;
• d=diameter of said particle, droplet and the like;
• whereby the effective apparent cross-section of said sample volume is determined for a class of said particles, droplets and the like having a diameter d.