Abstract: An aerodynamic particle size measuring device includes a laser energy source and beam splitting, shaping and polarizing optics for forming two parallel, peripherally overlapping beams. The beams are caused to intersect a gas stream perpendicular to the direction of gas flow, thus to form a measuring volume at the intersection of the beams and flow. Single particles are carried through the measuring volume with the gas flow, each particle scattering and extinguishing light according to the beam profile, as predetermined by the degree of beam overlap and the Gaussian intensity distribution of each beam. A photodetector, responsive either to scattered light or light extinction, generates a time-dependent voltage profile that tends to replicate the intensity profile. The resulting electrical signal is processed to determine an amplitude, set a threshold for minimally acceptable amplitudes, and to derive two negative-going zero crossings for an unambiguous time/velocity determination.

Abstract: An interferometric system for measuring cross-sectional dimensions of glass fibers and other elongate objects includes: a transmitting optics module for generating two laser beams, and causing the laser beams to intersect and interfere with one another over a measuring volume; several photodetectors to collect the light scattered by the glass fiber positioned in the interference region; and signal processing circuitry to deduce the fiber diameter using phase shifts between the signal pairs and fiber velocity using the frequency of the signals. The system further offers: elimination of the 360.degree.

Abstract: A system for measuring cross sectional diameters of optical fibers and other elongate cylindrical objects includes a transmitting optics module for generating two collimated laser beams, and causing the beams to intersect and interfere with one another over a measurement region. The optical fiber under inspection is caused to intersect the measurement region with its longitudinal axis perpendicular to a plane defined by the laser beams. Several photodetectors collect light scattered by the optical fiber, and generate signals indicating fiber diameter based on phase differences in the scattered light received by the detectors. The system can determine fiber refractive index by using three detectors to obtain two phase shifts. Differences in Doppler frequencies also are sensed by the detectors, for determining transverse velocity components.

Abstract: A system for measuring cross sectional diameters of optical fibers and other elongate cylindrical objects includes a transmitting optics module for generating two collimated laser beams, and causing the beams to intersect and interfere with one another over a measurement region. The optical fiber under inspection is caused to intersect the measurement region with its longitudinal axis perpendicular to a plane defined by the laser beams. Several photodetectors collect light scattered by the optical fiber, and generate signals indicating fiber diameter based on phase differences in the scattered light received by the detectors. Differences in Doppler frequencies also are sensed by the detectors, for determining transverse velocity components.

Abstract: The concentration of non-volatile residue in a test solvent is determined by generating multiple liquid droplets from a liquid stream including the solvent and ultrapure water. The droplets are dried to form a stream of multiple particles of the non-volatile residue. A supply of ultrapure deionized water is caused to flow continuously toward a non-volatile residue monitor, at a constant fluid flow rate. Upstream of the residue monitor, a syringe is provided for intermittently injecting a test solvent into the fluid stream. In one case, the solvent is injected for several minutes at a constant flow rate substantially less than that of the ultrapure water. A mixing valve, downstream of the point of solvent introduction, causes turbulent flow to thoroughly mix the solvent and water. In an alternative approach, a syringe is used to instantaneously inject solvent in the form of bursts.

Abstract: A system for determining the fractional capture efficiency of filters includes two filters having substantially the same capture efficiency connected in series. A steady, controlled flow of ultrapure water and a colloidal silica suspension is directed through both filters, with respective stages of the flow upstream of the upstream filter, between the filters and downstream of the downstream filter, directed to respective non-volatile residue monitors. Each residue monitor produces a digital output representing the non-volatile residue concentration at its respective stage. A microprocessor receives the digital outputs and generates respective residue values indicating residue concentration in parts per billion. The three residue values are used to characterize the residue by proportion of the colloidal silica suspension to other residue components, and to calculate filter capture efficiency with respect to the colloidal silica.

Abstract: An ultrasonic anemometer employs three ultrasonic transducers arranged in a configuration defining a horizontal equilateral triangle. Each of the transducers has a response profile characterized by a primary central lobe and secondary or side lobes angularly inclined from and surrounding the primary lobe. Each transducer is tilted from the horizontal to align the secondary lobes with signal propagation paths between it and the other transducers, thus affording a minimum number of transducers performing at a high degree of efficiency. Circuitry is employed to cause the ultrasonic transducers to generate either continuous wave acoustic signals or single pulse acoustic signals on an alternating basis. In each case only one of the transducers transmits the acoustic signal while the other two transducers receive the signal.

Abstract: A vacuum particle detector includes a cavity providing a passage for fluid flow, a laser diode and beam shaping optics to form a substantially rectangular beam spanning the chamber. Light sensing optics, including a pair of biconvex lenses, receive light scattered when the particles suspended in the fluid intersect the beam. At least some of the scattered light is transmitted through the lenses to a photodetector. The photodetector width is selected in concert with the focal lengths of the biconvex lenses, to provide a viewing depth of field commensurate with the complete span of the beam across the chamber, whereby the photodetector responds to particles that intersect the beam over the entire span. A cone and a surrounding sleeve, both concentric about an axis of the beam, absorb the laser energy beam to provide an effective beam stop.

Abstract: An electrospray nebulizer generates an aerosol comprised of submicrometer droplets substantially uniform in size. A liquid sample is supplied at a controlled rate to a capillary needle of the nebulizer, and droplets are formed due to an electrical field in the region about the needle discharge. The tendency of the droplets to disintegrate due to Coulomb forces is counteracted by sources of ionizing radiation within the nebulizer. The ions reduce the charge in each droplet while solvent evaporation reduces the diameter of the droplet. To further ensure against Coulomb disintegration, a controlled air sheath is introduced to the nebulizer for transporting droplets more rapidly downstream. Optionally, solvent vapor can be introduced into the air flow to reduce the rate of solvent evaporation within the nebulizer, and ions can be added to the air flow upstream of the needle discharge.

Abstract: A particle flux counter apparatus utilizing light extinction. The apparatus utilizes two oppositely disposed cylindrical mirrors (21a, 21b) to bounce a beam back and forth between them, the beam traversing the length of the cylindrical mirrors (21a, 21b) in incremental steps. A plane mirror (22) is cooperatively located to reflect the beam back between the system to traverse the length of the cylindrical mirrors (21a, 21b) a second time in incremented steps. The two sets of steps interleaving such that the beam forms a sheet of light. A detector (60) monitors the intensity of the beam. As particles in a sample aerosol intersect the beam, the light is extinguished and the beam intensity changes. The detector (60) transmits a signal to a microprocessor (108) analyzation. The apparatus also utilizes a feedback circuit (300) to regulate the beam intensity and alternatively provides for modulating the beam to provide for higher peak power into the detector (60) and elimination of common mode noise.

Abstract: A continuous flow condensation particle counter employs a working fluid to saturate a gas stream, and then condense onto particles carried in the gas stream as the stream is directed through a condenser and cooled below the supersaturation point. A porous saturation block is positioned beneath the condenser, and receives droplets of working fluid condensate and water as the droplets descend from the condenser by gravity. The saturation block is constructed of a hydrophobic material, whereby it allows the working fluid to pass through but retains water within a collection reservoir centered below the condenser. A vacuum pump and a periodically actuated solenoid valve are employed to introduce a partial vacuum to the reservoir and thereby evacuate accumulated water. The preferred working fluid is a perfluorinated hydrocarbon fluid that is substantially odorless, chemically inert and non-flammable. Water is immiscible in the working fluid, and thus readily separable.

Abstract: An apparatus for measuring nonvolatile residue concentrations in liquid is disclosed. A plurality of fixed and adjustable flow restrictive elements are utilized and arranged in-line from a fluid supply source to provide a constant, pressure controlled flow of liquid to the measuring apparatus and allow for real-time measurements and optimal concentration detection. An atomizer atomizes the liquid into droplets which are dried to nonvolatile residue particles. The nonvolatile residue particle concentration is then determined utilizing an electrostatic aerosol detector. The invention further discloses apparatus for collecting a sample of nonvolatile residue for analysis and identification using a corona precipitator.

Abstract: A non-imaging particle counter 10 utilizing one or more detectors 25 which directly collect light scattered by particles in a fluid traversing a sensing volume 63. The detectors 25, are non-imaging, non-focusing, optic-less light collection devices, such as large area photodiodes. The detectors 25 are arranged and configured proximate the sensing volume 63, but such that the beam of light 60 is not operatively incident thereon. The beam of light 60 is provided by a laser 50 and is shaped by a focusing/collimating lens 54. The beam of light 60 passes through several apertures 51-53 to reduce stray/background light in the system. The detectors 25 are oriented at an angle with respect to the plane formed by the longitudinal axis of the beam and the flow of fluid, wherein stray light 61 strikes the detectors 25 at an angle greater than the acceptance angle of the detectors 25, while scattered light strikes the detectors 25 at an angle less than the detectors' 25 acceptance angle.

Abstract: An instrument for detecting single airborne particles, and measuring their concentration, includes a transmitting optical fiber optically connected to a light source at one end, and a collecting optical fiber connected to a photodiode at one of its ends. The respective opposite ends of the optical fibers are potted into a rigid probe head with their exposed ends polished smooth and flat, facing each other and separated by an air gap of about one-tenth of an inch. At least some of the light from the source crosses the gap between the optical fibers and reaches the detector, such portion of the light defining a particle sensing volume. Particles passing through this volume are detected by optical extinction as they reduce the amount of light reaching the detector. The device has simple optics, requiring no lenses or mirrors. The transmitting and collecting fibers, and the air gap, form a well defined and repeatable sensing volume so that individual devie calibration is not required.

Abstract: An apparatus and method for determining the concentration of macromolecules and colloids in a liquid sample is disclosed. The apparatus preferably includes an electrospray apparatus 16 for forming droplets from the sample. Liquid is removed from the droplets by drying in the electrospray apparatus 16, thereby forming an aerosol. The aerosol of a size greater than a predetermined size is then counted by a condensation nucleus counter 52. In this manner, the target macromolecules and colloids are counted. This apparatus is capable of detecting very small macromolecules and colloids of a wide range of materials in a liquid, for example, individual molecules having molecular weight as small as 10,000.

Abstract: A method and apparatus for automatically detecting a coherent frequency burst is disclosed. The apparatus 10 determines the approximate frequency and duration of the burst. The apparatus 10 operates utilizing principles of autocorrelation to reject random noise and maximize the efficiency of a down stream data signal processor. The apparatus 10 includes delay means 30 which accepts a digitized signal from a device, such as a photodetector in an LDV, and generates a plurality of delayed signals. The delayed signals are then multiplied by the original signals by multiplier means 40. The multiplied signals are provided to averaging circuits 50. The averaged signals are then compared to a reference level by comparators 60, the output of which is provided to priority encoder 70. Priority encoder 70 prioritizes the signals received from comparators 60 and determines the length of the burst.

Abstract: Methods and apparatus for enhancing the accuracy of laser optical measuring instruments using fringe pattern spacing are disclosed. The apparatus in one embodiment includes a laser beam source 10, a beam splitter 14, and mirrors 22 to deflect the beams 18, 20 emitted from the beam splitter 14 to a sensing volume. Alternative embodiments include prisms 42, 44, gratings 62 or other optical devices in lieu of mirrors 22. Objects passing through the sensing volume scatter light which is detected by the instrument to determine, among other things, the velocity of the object. The emitted beams 18, 20 are automatically deflected in response to wavelength changes of the laser beam 16 such that variations in the fringe spacing, due to variations in laser beam 16 wavelength, are compensated by variations in the closing angle K of the emitted, deflected beams. The fringe pattern spacing is thereby held more nearly constant enhancing the accuracy of the instrument.

Abstract: An optical fiber connector assembly for coupling an optical fiber cable having optical fibers to an instrument equipped with a light source and a photodetector. The connector assembly has a housing accommodating a pair of ferrules that support the optical fibers. The ferrules have cone-shaped heads and generally flat forward ends. The optical fibers have ends that are flush with the flat ends of the heads. The heads of the ferrules seat into cone-shaped reccesses in receptacles mounted on the instrument. The light source and photodetector are aligned with the receptacles so that the light from the light source is transmitted to a first optical fiber and the light from second optical fibers is received by the photodetector. A screw mounted on the housing is threaded into a hole in the instrument to releasably connect the housing to the instrument and locate the heads in alignment with the cone-shaped recesses in the receptacles.

Abstract: A Doppler velocimeter having laser generating crossing light beams provides a crossing and focus area forming a measuring volume having regions of high and low light intensity. Solid or liquid particles moving through the measuring volume scatter light which is sensed and converted into a signal having a frequency. A signal processor measures the frequency by detecting and tracking an individual zero crossing of a particle through the measuring volume to provide real time information about the coherent component of the signal. This information is useable to determine the velocity of the particle moving through the measuring volume.

Abstract: A condensation nucleus counter (1) for measuring particulate concentration within a gaseous environment, including an inlet orifice (3) leading to a flow path (5) within saturator (4). The resultant vapor (10) enters a condenser section (11) wherein the particulate matter suspended within serves as the nucleus for condensation. The enlarged droplets (23) thus formed enter a conventional optical particle counter section (15).