Abstract: A process for batch interferential granulometry applicable particularly to poly-dispersed biological particles. The process is characterized in that the positioning of the angular measurement regions is selected according to the criteria of representativity of the signals obtained with respect to the given granulometry sought, particularly for their alternative components, and in that the processing of the signals comprises successively a harmonic Fourier analysis of their alternative components, and the use of the results of this analysis in a computation leading to the parameters sought, namely, the numbers, mean dimensions, and granulometric distribution of the analyzed particles.

Abstract: A method of measuring volume of materials in suspensions in a liquid includes providing a sample of liquid containing particulate materials in suspension, passing a laser light beam through the liquid, the laser being diffracted upon exit from the sample, and measuring the diffracted light with at least two photoelectric cells positioned at differing distances from the central ray of the laser. Electrical signals F and F' from the photoelectric cells are produced and the volume (V) of materials in suspension is determined according to the relation Vd=aF+a'F', where d is the average minimum diameter of the particles and a and a' are respective balancing factors. An apparatus for carrying out the method, particularly as it relates to determining the quality of water, includes raw water and flocculating agent sources upstream from a purification station and at least one coagulation-settling system, which includes a pipe coupled to the supply sources and a settling tank in which flocs settle.

Abstract: An illuminated display apparatus includes a laser projector and a retro-reflective screen onto which the beam from the laser projector is projected. A beam deflection device may be disposed between the projector and the screen. The beam deflection device may be associated with a modulator for modulating the intensity of the light beam. A beam spreader and a mask may be substituted for the deflection device and modulator, the shadow of the mask appearing on the screen.

Abstract: A device for measuring dust content in a gas stream comprising a light soe, a photosensitive receiver, and means to direct an essentially dust free stream against the main gas stream to form a dust curtain into which the beam penetrates and reflects to the receiver.