Abstract: Flow rates of multi-phase streams may be determined by use of a fiber optic probe which establishes an illuminated sensing zone of finite dimensions. The probe collects light backscattered from the zone, the collected light being converted by a photodiode to voltage waveforms. Flow rate is determined by sampling voltage waveforms at discrete points in time, the sample being digitized and the digits being autocorrelated for such discrete points.

Abstract: An engine control system for operating an internal combustion engine with any mixture of alcohol and gasoline. The control system includes an air/fuel ratio control system providing a desired fuel charge in relation to the alcohol and gasoline content of the fuel which is indicated by an optical sensor. In one embodiment, the optical sensor includes a hemispherical lens having hemispherical recesses formed through the lens base equidistant from the lens plane of symmetry. A light emitting diode positioned in one recess irradiates substantially the entire 2 .pi. steradian outer surface of the hemispherical lens. A portion of the transmitted light is reflected from substantially the entire hemispherical lens and substantially focused on a photodetector positioned in the other recess. Emitter and detector are substantially positioned at conjugate focii of the lens which provides substantially a 2 .pi. steradian collection aperture.

Abstract: Apparatus for measuring the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water comprises a pulsed laser having a high intensity (power per unit area) output beam split into two sub-beams, one of which is a probe beam directed into the ocean water. The intensity of the output beam pulses exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering within the medium and to produce therefrom a phase-conjugate beam which propagates along the path of the first sub-beam but in the opposite direction. The second sub-beam is reflected by a mirror to and combines with the PC beam and the combined beams are mixed at the cathode of a photodetector which produces a heterodyne frequency that is proportional to the temperature T.sub.s. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.

Abstract: A system is presented for the remote detection of the diffuse attenuation coefficient or K factor over very large areas and over relatively short time periods; and for determining depth in a body of water or other medium. In accordance with the present invention, a laser is used to generate short pulses of light with pulse widths on the order of nanoseconds. The laser light is expanded by optics and projected into the water or other medium. An intensified CCD (charge coupled device) camera is electronically shuttered after an appropriate time delay such that the image formed by the camera is composed of light backscattered by the water from a layer of range z and a thickness of .DELTA.z. The signal detected by the camera is S.sub.i. If several measurements of S.sub.i are made at known time delay differences such that the differences of range gates z.sub.i are also known, then K can be calculated.

Abstract: Apparatus is disclosed for remotely sensing the unknown subsurface temperature T.sub.s of a bulk transparent medium, such as ocean water, using a cw laser beam and a pulsed laser beam. In one embodiment the cw output of a continuous laser is split into two sub-beams. An optical amplifier periodically amplifies the first such sub-beam thereby generating an intense pulsed laser beam having a plurality of pulses with the same wavelength as the cw laser beam. The intensity level of the pulses is sufficient to produce stimulated Brillouin scattering when focussed into the ocean water. The pulsed laser beam is directed into the water thereby generating an intense return phase-conjugate beam propagating along the path of the pulsed laser beam but in the opposite direction thereto. The phase-conjugate beam and the second sub-beam are mixed at the cathode of a photodetector to produce a heterodyne frequency proportional to the temperature T.sub.s.

Abstract: A control system having opto-electric detectors responsive to different solids concentrations and character of the solids of a slurry, the output of the detectors controlling the addition of a flocculants to the slurry to optimize coagulation of the materials in the slurry. The detectors having outputs sensing different slurry conditions with the detector outputs being processed to control the addition of different flocculants to the cell.

Abstract: To remotely measure the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water, a high intensity pulsed laser beam is split into two sub-beams, a probe beam and a reference beam. The probe beam is directed into a sample of ocean water of unknown temperature, and the reference beam into a reference sample of water having a known temperature T.sub.r. The irradiance of the two pulse beams exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering (SBS) within the two samples and produce therefrom two return phase-conjugate (PC) beams. A photodetector mixes the two PC beams and produces a heterodyne frequency that is proportional to the difference in temperatures T.sub.s and T.sub.r. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.

Abstract: An integrating sphere for detecting particles in an aerosol has a diffuse reflectant interior surface and a plurality of photodetectors. The aerosol passing through aligned ducts which are spaced at the center of the integrating sphere, and a beam of collimated light, such as a laser beam, projects transversely through the aerosol in the space. Particles in the aerosol scatter the light, and the scattered light is detected simultaneously by the photodetectors within the integrating sphere. A coincidence detection circuit is used to detect the number of times scattered light is simultaneously detected by the photodetectors and, thereby, count the number of particles in the aerosol.

Abstract: An apparatus for detecting a liquid-vapor change of phase in a fluid substance traveling through a conduit comprises a detector housing providing a path of travel for fluid and interposed in a portion of the fluid-carrying conduit in which the change of phase is to be detected, a source of radiation disposed for directing radiation into the path of travel and a detector for detecting radiation disposed generally at an opposite side of the path of travel from the said source. The arrangement is such that radiation from the source will pass through the fluid in the path of travel prior to reaching the detector. The detector is responsive to radiation detected thereat for producing a corresponding electrical signal. A detector circuit is responsive to the electrical signal produced by said detector for producing an output signal indicative of a liquid-vapor change of phase of the fluid in the conduit.

Abstract: A granulometry device embodying the invention comprises a measuring probe and a micro-computer. The micro-computer provides digital filtering on a first discrete distribution function that is calculated by statistical inversion from a plurality of radiation measurements supplied by the probe and a theoretical radiation coefficient matrix thereby determining, after an iterative calculation, an optimum relation which should be satisfied by the nodes defining a discrete distribution function so as to offer a maximum correlation with uncertainty measurements. All the discrete distribution functions satisfying this relation are then calculated by statistical inversions. The mirco-computer provides an optimum statistical evaluation of the distribution of particles in a gas or liquid fluid.

Abstract: A particle measuring device having a light source, scanning means for optically scanning a light from the light source in a direction intersecting the direction of passage of particles to be examined in a portion to be examined through which the particles to be examined pass, means for making the shape of the scanning light applied to the particles to be examined into a shape longer than the length of the particles to be examined in the direction of passage of the particles to be examined, and light receiving means for receiving the light from the portion to be examined.

Abstract: In an instrument for measuring the size of particles entrained in a fluid stream, photodetectors are mounted on the walls of tubing shaping the flow of the fluid stream through a laser beam. The photodetectors generate electric current pulses in response to scattering of the light which is generated by the particles passing through the laser beam. The pulses generated by the photodetectors provide a measurement of particle size. The photodetectors are mounted either adjacent to the laser beam on the tubing walls or, alternatively, the tubing walls are mirrored above and below the laser beam and the photodetectors are mounted on the tubing walls at right angle bends of the tubing to receive the light reflected from the mirrored surfaces.

Abstract: A method and apparatus for measuring the particle concentration of suspensions, especially suspensions having high particle concentration. Light is directed into the suspension, and light scattered by the particles, preferably back-scattered light, is detected at a first and a second position located at different distances from the position where the light is sent into the suspension. The concentration is then calculated asarctanh (E.sub.f /E.sub.n),or preferably ##EQU1## where E.sub.n is the detected light intensity at the first relatively near position and E.sub.f is the light intensity at the second relatively far position. The intensity of the light directed into the suspension is controlled by means of the relation E.sub.f .multidot.E.sub.n =1. The mean value of E.sub.f and E.sub.n is then compared with 1 in order to determine whether the calculated concentration corresponds to the concentration of the suspension being measured.

Abstract: An apparatus for measuring a property of a liquid comprises at least one guide for electromagnetic radiation, means for directing electromagnetic radiation into the guide, means for providing at least one drop of liquid in contact with the guide at a position where radiation from the guide can enter the drop, and means for deriving a signal which is a function of the interaction of the radiation with the liquid of the drop.

Abstract: An alarm system for warning of a creosote chimney fire hazard, having both means to produce a visible alarm when the creosote temperature is nearing the creosote flash point, and means to produce an audible alarm when light from actual ignition of a creosote fire is detected. The invention also provides means to discriminate against detection of wood fire light, to minimize false alarms.

Abstract: The present invention comprises a simple multi-purpose on-line system for monitoring the concentration and/or the total amount of an organic analyte species or inorganic analyte species in an aqueous solution. The on-line detection system comprises a detection column and a sensor mounted around the detection column. The sensor consists of an electromagnetic radiation source (typically a light source) and an appropriate detector for the electromagnetic radiation. The response from the detector drives an electric circuit, which provides a signal to a recorder as well as a means to trip an alarm system and/or a process system.

Abstract: A focused beam of light from a light source is directed into a closed smoke chamber, having inlets for admitting smoke particles, toward a reflector which reflects and refocuses the beam back into the light source, the direct beam and the reflected beam passing through a test zone within the chamber. In the event that smoke particles enter the test zone, the direct and reflected beams strike and bounce off of those particles to produce scattered radiation that will be picked up and detected by a light responsive sensor to generate an alarm signal. By closely controlling, rather than baffling the light, optimum operation is obtained, efficiency is enhanced and false alarms are minimized.

Abstract: A scattered-light smoke detector having an improved shield structure. A detector circuit is provided on a printed circuit board which is disposed at an upper portion of a smoke detecting section. The smoke detecting section includes a planar base and a surrounding wall extending downwardly from a lower surface of the base and having an opening or openings which allows or allow smoke to enter therethrough. The surrounding wall defines a smoke detecting space therein. A light emitting element and a photodetector element which are disposed at positions where they are not opposite each other and optical axes thereof intersect each other at a predetermined angle and said photodetector element can receive light from the light emitting element scattered by smoke entering the smoke detecting space. The printed circuit board is attached on an upper surface of the base. A shield layer is interposed between said printed circuit board and said base.

Abstract: A particle detector includes optical fiber for conducting short wavelength radiation received from a radiation source through a chamber in which a semiconductor wafer is being processed. Light that is scattered by contaminant particles in the process chamber is sensed by an optical fiber pickup, and pulse signals are generated by a photosensing means to provide an indication of the number of particles within the process chamber.

Abstract: A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region illuminated by a laser beam and receiving the particles in a medium, such as air. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times.

Abstract: A station for locating through laser rays an object likely to diffuse back a part of the incident laser ray, wherein the optical emitter and receiver devices consist of one single device comprising, in the direction of emission, a device for separating the emitted and retrodiffused rays, an optical device converting the emitted parallel beam of small diameter into a divergent beam and a telescope adapted to collimate the divergent beam received from the optical device into a parallel beam of larger diameter, the retrodiffused beam travelling that path in the direction reverse from the emitted beam, the invention being usable for detecting in particular forest fire smokes.

Abstract: An apparatus and method for detecting particles in a clean environment provides for forming a beam of electromagnetic radiation into an instantaneous scattering volume and scanning the scattering volume in space defined by a flow cell. Particles are transported by fluid means into the space occupied by the scattering volume and individual particles are multiply scanned while passing through the scanning scattering volume. A fluid conduit is provided to transport the fluid and the particles and windows are provided to transmit the radiation beam into the space defined by the flow cell and to transmit scattered radiation from the particles out of the space. The radiation from the particles is collected and detected to provide an output signal. In the preferred embodiment, the output signal is analyzed to determine the concentration of the particles in the fluid and to determine the size and velocity of each individual particle.

Abstract: A method for assaying incompatible sediment in a blended heavy fuel oil is provided. The method is based on measuring total light absorption at 1600 nanometers wavelength, for example, of two or more samples blended to different viscosities, at least one such sample being at specification viscosity. The method may be used to control visbreaker severity so as to reduce the large ERT safety margin commonly used by refiners.

Abstract: An apparatus for measuring particles in a liquid, with the apparatus including an arrangement for allowing a sample liquid to flow out from a nozzle into a gas in a stream, an arrangement for radiating light into the sample liquid stream coaxially with the axis of the stream, and an arrangement for collecting ways of light scattered by particles contained in the sample liquid stream at a point outside and by a side of the sample liquid stream and then detecting the collective light rays.

Abstract: In the measuring chamber the flow of the fluid to be monitored impinges at an angle upon the end window of the measuring probe. Due to the thus occurring self-cleaning action, no deposit forms at the end window and which deposit would falsify the meaurement. In the event of small fluid quantity throughputs and flow rate and thus insufficient cleaning action, a nozzle ia provided for producing a jet which is directly aimed at the end window. The fluid is irradiated in the region of the measuring probe by using ray guides. If particles causing turbidity are contained in the fluid, the rays will be reflected, collected by the optical system and supplied to a receiver through a ray guide.

Abstract: Gases in the atmosphere are detected remotely using a Raman-shifted excimer/dye laser beam formed by passing an excimer/dye laser beam through a circulating-medium Raman-shifting cell which significantly increases the measurement repetition rate and allows for the production of an infinite number of different wavelengths for measurement. The Raman-active medium is continuously circulated so that the inputted laser beam passes through the Raman-active medium when the molecules of the medium in the optical path are at their ground energy level state. The Raman cell is then tuned to provide a first wavelength, preselected for nonabsorption by the gases to be detected, which is transmitted through the gases to be detected toward an object capable of reflecting the beam back. The Raman cell is also tuned to provide a second wavelength, preselected for being highly absorbed by the gases to be detected, which is then transmitted and similarly reflected.

Abstract: In a combined obscuration and scattered-light smoke detector, light from a light source in a smoke chamber is reflected from an image-forming optical component onto a first light sensor which senses a reduced electrical signal in the presence of smoke while a second sensor, viewing light from the light source at an angle, senses an increased electrical signal in the presence of smoke. The output of each receptor is subjected to a band pass filter, an amplifier and a comparator; the resultant signals insure early and reliable activation of an alarm when even a low level of smoke is present in the smoke detector. A second light source having a wavelength different from that of the first light source provides, in the obscuration mode, added sensitivity to smoke.

Abstract: An optical head, to which laser light is supplied, produces, in a measuring volume, at least two focusing points at which particles flowing through the measuring volume are illuminated and cause scattered radiation which is collected by the optical head. The laser beam is directed, via at least one first light guide, to the optical head. From the optical head, the radiation received from the measuring volume is supplied, via at least one second light guide, to a light receiving means. The optical head is small-sized and may be rotated about its optical axis by means of a rotating device.

Abstract: A photoelectric smoke detector of this invention comprises a smoke-detection arrangement including a light emitting element and a photodetecting element and a smoke-detecting unit on which said smoke-detection arrangement is mounted. The smoke-detecting unit includes a base plate to which said smoke-detection arrangement is attached and a peripheral wall having such a configuration that allows smoke to enter from the outside, but substantially prevents light to enter from the outside. The peripheral wall is formed of a plurality of wall elements, each of said wall elements is arranged substantially regularly and formed integrally with said base plate so as to extend downward from the base plate. The smoke-detecting unit further includes an insect net which has been fixed to the outer surfaces of the wall elements in the shaping process of the smoke-detecting unit so as to be fit around the outer periphery of the peripheral wall.

Abstract: A method of and apparatus for measuring the density of fine particles floating in a fluid. The method includes the steps of: applying light to a fluid contained in a tubular member having an interior surface constituted by a mirror surface; condensing and detecting rays traveling toward one axial end of the tubular member among the light reflected by fine particles in the fluid; and subjecting the detected rays or signal to a predetermined processing, thereby measuring the density of the fine particles. The apparatus employed in this method includes: a tubular member; a light source directed in a direction perpendicular to the axial direction of the tubular member; a condenser lens disposed at one axial end of the tubular member; a detector opposing the condenser lens; and a processor which processes a signal applied thereto from the detector in a predeteremined manner to obtain the density of fine particles.

Abstract: A sensor for mixing ratio of liquid fuel comprising, a cylindrical enclosure having both inlet and outlet openings to act as a passage through which a mixing liquid fuel flows. A transparent column concentrically disposed in the enclosure to make the outer surface thereof contact with the liquid fuel, each end of the column is inserted into a ring-shaped wall provided with the inner side of the open end portion of the enclosure. A light emitting diode and a photo diode are provided so as to sandwich the column in the lengthwise direction, so that the light emitted from the former enters the column through its one end and reflects at the boundary of the column and the liquid fuel, and go onto the other end thereof to fall on the latter. A metallic sleeve sealant is provided, one side of which is liquid tightly telescoped into each end of the column, the other side of which is liquid tightly secured to the outer side of the wall to hermetically seal between the liquid fuel and the column.

Abstract: There is disclosed a turbidimeter with an optical sensor having an IRED surrounded by four radiation detecting solar cells mounted on a printed circuit board which is encapsulated by a transparent potting material in a cavity of a housing. Additionally, the printed circuit board has a temperature sensor mounted thereon which is utilized by a sensor operating circuit to control the magnitude of the diode energizing current to compensate for variations in component response due to temperature variations.

Abstract: An arrangement for in situ determination of the quantity of turbid matter, aerosol and/or dust in flue gas which flows through a flue by measurement of intensity of light irradiated by means of an optical transmitter in the flue, and dispersed on solid or fluid dispersion particles. The dispersion light is detected by a detector which is arranged outside of the bundle of rays of the transmitter and provided with a wide angle focusing optic. A woodsche horn absorbs the not dispersed part of the bundle of rays of the transmitter. The light source of the transmitter is formed as a xenon spark discharger with intensity maximum in the region of 350-600 nm, the detector signal is evaluated by an evaluating electronic circuit. The arrangement determines extremely low quantities of harmful matter.

Abstract: A sensor system for the detection and/or analysis of smoke, gas or the like, comprising a detection means 6 connected to an analyser means 2 via fiber-optic links 3, 11 and 12. The detector 6 determines the presence of smoke, gas or the like, while the analyzer 2 analyzes the composition of the smoke, gas or the like. The exact location and nature of the smoke, gas or fire can therefore be determined with the aid of suitable associated circuitry 9.

Abstract: A light is applied to particles to be examined in a cell, the scattered light from the particles to be examined is converted to an afocal light, a beam splitter is provided in the afocal light beam, and photometering and observation of the cell are efficiently effected in two optical paths branched off by the beam splitter.

Abstract: Disclosed is a method and apparatus for measuring particles in a fluid by irradiating the fluid containing the particle with a laser beam and analyzing the laser light scattered by the particle to determine the characteristics of the particle. An elliptical laser beam is projected into a particle detection area in which the particles to be measured are caused to flow. The laser light scattered by the particle is received for photoelectric conversion into a time-series photoelectric signal in a direction along which the particle flows. The photoelectric signal is subjected to a moving average process to determine a time width during which the signal exceeds a predetermined level to cause the change in intensity of the scattered light. This change is recognized as a change in intensity caused by the passage of the particle through the particle detection area when the time width falls within a certain range.

Abstract: A monitor for particles of various materials which counts the number of the particles on real-time and in situ basis. The monitor comprises a unit for illuminating an object to be inspected with an illumination light beam of a predetermined cross-sectional area, a unit for detecting a change in optical mode of the illumination light beam caused by the particles being contained in the inspected object and illuminated with the illumination light beam, the illuminating and detecting units being of a unitary structure, and a unit for counting an amount of the particles contained in the inspected object by using a change in intensity of an optically mode changed light beam.

Abstract: A coherent laser light flux is projected into a cell made of transparent quartz and light scattered from particles suspended in an antigen-antibody reaction liquid contained in the cell is detected by a photomultiplier by means of a collimator. An output electrical signal from the photomultiplier is sampled at different time instances and samplings are supplied to a fast Fourier transformer to derive a plurality of power spectrum desnities of fluctuation in intensity of the scattered light. A plurality of power spectrum densities are averaged to generate a mean power spectrum density. An amount of antigen contained in the reaction liquid is measured in accordance with the mean power spectrum density.

Abstract: A particle detecting device for detecting particles contained in a flowing sample fluid is provided which comprises a light beam irradiating mechanism for irradiating the sample fluid with a light beam, the light beam irradiating mechanism including a light beam deflecting portion for directing the light beam across the flow of the sample fluid and for causing the light beam to scan a predetermined irradiation region of the sample fluid, this scanning causing a portion of the light beam to be scattered by the particles in the irradiation region to produce scattered light; a light receiving mechanism for receiving the scattered light and for converting the scattered light to an electrical signal; and a signal processor coupled to the light receiving mechanism for processing the electric signal to obtain at least one of the number of particles in the sample fluid and a particle size distribution for the particles in the sample fluid.

Abstract: A modular transceiver head including cooperative cover and base members operable as a transmitter or as a receiver of infrared energy. The cover member includes a window defining a comparatively wide field of view in azimuth and in elevation. An optical train including a gimbaled specular member that is mounted to the base member readily allows both rough and fine adjustment of the pointing direction of the specular member anywhere within the field of view of the cover member window. A controller including a processor is coupled to a transceiver head pair respectively operative as a transmitter and as a receiver of infrared energy to controllably project a beam of infrared energy therebetween through a protected region. The controller is operative to de-sensitize the beam against potential electrically interferring effects present along the beam path. The controller is periodically operative in a self-test mode to reduce the intensity of the projected-beam to simulate a smoke condition.

Abstract: The arrangement for the transmission of laser light (9) exhibits a laser tter (1) and a receiver (2) for the laser light (9). In order that it should be possible to establish if the optical system (6) of the receiver (2) becomes dirty or an obstruction passes in front of this optical system, the laser receiver (2) is provided with a reference light source (12) disposed after the optical system (6). If the objective (6) becomes dirty or if an obstruction passes in front of the same, light from the reference light source (12) is scattered into the detector (7), so that an alarm indication can be given by a warning circuit (14).

Abstract: A method and apparatus is disclosed for detecting the presence of particulate matter in liquids intended for pharmaceutical use, for example liquid contained in vials, flasks or ampoules. The method involves mechanically imparting to the vial or flask a rotary motion and then suddenly stopping it. Any particles contained in the liquid will continue to move, and will be illuminated by a number of parallel light beams of laser light, which are caused to pass through the liquid. Laser light diffused by particles in the liquid is converted into an electrical signal by a photomultiplier. The signal from the photomultiplier is amplified, filtered, and compared with a reference signal. The apparatus has a number of mandrel/chuck units which each impart a rotary motion to one container. At a second location, the light from a He-Ne laser is conveyed through optical fibers in the form of several parallel beams through each container, illuminated from below through a plurality of holes in the bottom of the mandrel.

Abstract: A compact particle flux monitor is formed with an enclosure through which a laser beam is directed by a lens. An aperture in the enclosure allows free particles which are to be detected to pass through a sensing area at a limiting acceptance angle thereby providing an indication of direction of particle flow. Photodiodes mounted at the sensing area detect the particles, including relatively small particles, by means of the high intensity beam portion at the region of the focal point of the light beam. The response region along the diverging beam is relatively long so that the response as a function of particle size is above background noise level.

Abstract: The method of the present invention which relates to the measurement of the turbidity of a liquid media, is characterized by the following steps.(i) Placing a measuring cell having a sensor having a light-receiving surface in contact with the liquid media, wherein the light-receiving surface is oriented in a direction permitting bubbles dissolved in the liquid media to float away therefrom and out of the cell.(ii) Cleaning the light-receiving surface intermittently.(iii) Allowing bubbles in the cell to float out of the cell.(iv) Radiating light in the liquid media.(v) Detecting scattered light impinging on the light-receiving surface.The present invention also provides an apparatus for measurement of liquid media turbidity in accordance with the present invention.

Abstract: A method and apparatus for determining the reflectivity of the tailings from a coal flotation cell to optimize the cell operation. A photoelectric detector determines the coal content of the tailings and through a process controller; frother and collector addition to the cell is monitored. An ultrasonic energy vibration is periodically transmitted to the detector to remove deposits on the detector to optimize detector operation.

Abstract: An apparatus for determining the reflectivity of the tailings from a coal flotation cell to optimize the cell operation. A bifurcated fiber optic cable has ends connected to a light source and a photoconductor, with a scanner end of the cable being submersed in a coal slurry. Light transmitted to the scanner end of the cable is backscattered to the photoconductor to function as a detector to determine the coal content of the tailings and through a process controller, frother and collector addition to the cell is monitored. An ultrasonic energy vibration is periodically transmitted to the scanner end of the cable to remove deposits thereon to optimize detector operation.

Abstract: The invention relates to a measuring method of the properties, especially the dry matter content of cellulose pulp. The most important measurement at the wet end of a paper-making machine is the measurement of dry matter content and quantity of the pulp. The material quantities can be readily measured from a finished product but the wet end optimal control requires a method and apparatus capable of measuring reliably the dry matter content of mass suspension.

Abstract: An apparatus for measuring particles in a fluid comprises a laser source for producing a laser beam which is projected onto the fluid containing the particles. Laser light scattered by the particles is converted into an electrical signal consisting of pulses corresponding to the particles to be measured. The pulses are counted by first and second counters and processed in a processor to derive therefrom the diameter and/or concentration of the particles. The first and second counters are alternately operated for pulse counting and inhibited from pulse counting. Each counter transfers its count to the processor during the period that it is inhibited from counting.

Abstract: A system for detecting contaminant particles in a liquid, such as used for processing wafers during the manufacture of integrated circuits, distinguishes non-contaminant bubbles generally found in liquids from contaminant particles. The system provides a controlled laminar fluid flow of the liquid through a pipe, and the substantially spherical bubbles in the flow path are detected by symmetrically spaced photodiodes. The irregularly shaped contaminant particles are detected, whereas the presence of bubbles are negated by the detection system by virtue of the balanced photodiode assembly.

Abstract: A particle detector includes a laser, a beam shaping lens, and a pair of mirrors which reflect the shaped laser beam back and forth between the mirrors a selected number of times in order to create a sheet of light or light net between the mirrors. The path of the beam is terminated by a beam stop which contains a photodiode to monitor beam intensity and thereby system alignment. Light scattered by a particle falling through the sheet of light is gathered and transmitted to a photodiode. A peak detector provides a measure of the peak intensity of light scattered by such a particle to a microprocessor, which counts the number of particles falling through the light net in a selected time interval. The microprocessor also uses the peak intensity to estimate the size of the particle.