Device for determining the granulometric composition of a mixture of particles by diffraction of light

Claim 1

A device for determining the granulometric composition of a mixture of particles by light-diffraction, said device including: a source of monochromatic light which emits a parallel beam (1); means (2) for making the mixture pass through the beam; an optical system for forming the diffraction pattern in the focal plane 4 of the beam by the mixture, the pattern being circularly symmetrical about a centre (5) constituted by the image of the parallel beam; a system for scanning the diffraction pattern, said system including a set of light detectors (102, 104) each of which receives the light flux which passes through a light-integration area (AI, AJ), each area being constituted by a predetermined portion of the diffraction pattern and having substantially the form of a segment of a circular ring which is concentric with the pattern, the ring being defined by its inner and outer radii, each detector supplying a detection signal which is representative of the light flux which it receives; and a circuit (70) for processing the data constituted by the detection signals; characterized in that said scanning system includes at least two successions (AI,AJ) of increasing inner and outer radii; the inner radius of each integration area of each succession (AI) being greater than the outside radius of the preceding integration area so as to allow unoccupied ranges in the continuous sequence of the values of the radii, the ranges being located between two consecutive integration areas in the continuous sequence and being narrower than the areas; the inner and outer radii of the areas of any one of these successsions being shifted with respect to those of the areas of each other successions so that in said continuous sequence the areas of these other succesions occupy the unoccupied ranges of any succession in question, extending beyond these ranges on either side.

Claim 2

A device for determining the granulometric composition of a mixture of particles by light-diffraction, said device including: a source of monochromatic light which emits a parallel beam (1); means (2) for making the mixture pass through the beam; an optical system for forming the diffraction pattern in the focal plane 4 of the beam by the mixture, the pattern being circularly symmetrical about a centre (5) constituted by the image of the parallel beam; a system for scanning the diffraction pattern, said system including a set of light detectors (102, 104) each of which receives the light flux which passes through a light-integration area (AI, AJ), each area being constituted by a predetermined portion of the diffraction pattern and having substantially the form of a segment of a circular ring which is concentric with the pattern, the ring being defined by its inner and outer radii, each detector supplying a detection signal which is representative of the light flux which it receives; and a circuit (70) for processing the data constituted by the detection signals; characterized in that said scanning system includes at least two successions (AI,AJ) of increasing inner and outer radii; the inner radius of each integration area of each succession (AI) being greater than the outside radius of the preceding integration area so as to allow unoccupied ranges in the continuous sequence of the values of the radii, the ranges being located between two consecutive integration areas in the continuous sequence and being narrower than the areas; the inner and outer radii of the areas of any one of these successsions being shifted with respect to those of the areas of each other successions so that in said continuous sequence the areas of these other succesions occupy the unoccupied ranges of any succession in question, extending beyond these ranges on either side.