Photoelectric apparatus for measuring the size of particles

Claim 1

IN APPARATUS FOR MEASURING THE SIZE OF PARTICLES SUSPENDED IN A FLUID, THE COMBINATION COMPRISING ILLUMINATOR MEANS ARRANGED TO PROJECT A BEAM OF LIGHT INTO THE PATH OF MOVING PARTICLE LADEN FLUID, INCLUDING A LIGHT SOURCE FROM WHICH LIGHT PASSES THROUGH A CONDENSER, THENCE THROUGH A FIELD APERTURE, THENCE THROUGH A CONVERGENCE STOP AND THENCE THROUGH A PROJECTOR, AND DETECTOR MEANS ARRANGED TO COLLECT LIGHT SCATTERED BY A PARTICLE ILLUMINATED BY SAID BEAM, INCLUDING A COLLECTOR, A CONVERGENCE STOP, A FIELD APERTURE, A CONDENSER AND A PHOTOMULTIPLIER, SAID DETECTOR MEANS HAVING A RELATIVELY LARGE ANGLE OF ACCEPTANCE IN A PLANE PERPENDICULAR TO THE DIRECTION OF MOTION OF SAID FLUID AND A RELATIVELY SMALL ANGLE OF ACCEPTANCE IN A PLANE PARALLEL TO SAID DIRECTION, WHEREBY AN ILLUMINATED FIELD DIMENSIONALLY SMALLER IN SAID DIRECTION THAN PERPENDICULARLY THERETO IS PROVIDED.