Abstract: A mixer for analytical application mixes a container of fluid without a magnetic stir bar. A device for testing a liquid for particles can use the mixer. The mixing can occur in a sealed container, and liquid can be transmitted to the device from the sealed container.

Abstract: A mixer for analytical application mixes a container of fluid without a magnetic stir bar. A device for testing a liquid for particles can use the mixer. The mixing can occur in a sealed container, and liquid can be transmitted to the device from the sealed container.

Abstract: A mixer for analytical application mixes a container of fluid without a magnetic stir bar. A device for testing a liquid for particles can use the mixer. The mixing can occur in a sealed container, and liquid can be transmitted to the device from the sealed container.

Abstract: Fluid-based particle detection exhibits improved light collection and image quality from a light collection system that uses immersed optics on a flow-through cell for collecting and detecting scattered light from particles carried by the fluid. The flow-through cell includes first and second body sections that are coupled to form a unitary article and have opposed interior surface portions configured to form opposed walls of a flow channel through which the fluid flows. First and second optical elements are associated with the respective first and second body sections. In certain embodiments, at least one of the first and second optical elements is an integral part of its associated body section. A lens element constructed as an integral part of the unitary flow-through cell eliminates additional interfaces or bonding joints that cause scattering and absorption of light.

Abstract: A light-extinction-type optical particle detection system comprises a laser producing a beam in response to a drive current amplitude reaching a lasing threshold, a view volume, and a light-extinction detector. The beam is characterized by mode-hopping noise energy produced by spurious switching of laser operating modes. The system comprises a signal generator producing the drive current such that its amplitude transitions across the threshold by a selected amount and at a selected frequency to cause the beam to operate simultaneously in multiple modes. The selected amount and frequency cooperate to spread the mode-hopping noise energy over a spectral range established by the number of modes, such that the detector does not appreciably respond to the mode-hopping noise energy.

Abstract: A particle detection system exhibits an increased ability to detect the presence of submicron diameter particles and to distinguish between noise and pulse output signals generated by small diameter particles on which a light beam is incident. This increased ability results from the incorporation of a light reflector, a pair of detector elements that detect correlated portions of the light beam that have been scattered in multiple directions, and a coincidence circuit that determines whether each detector element in the pair concurrently generates a pulse output signal exceeding a predetermined threshold. Sample particles are counted only when both detector elements concurrently detect scattered light components.

Abstract: An optical scattering particle counter uses optical scattering and heterodyne detection techniques to overcome the lower limit on particle size detection stemming from background light scattering by the fluid carrier in which a particle is immersed. The particle counter uses a heterodyne technique to exploit a basic physical difference between target particle scattered light and the background light. For gas-borne particulate monitoring, the carrier gas molecules have a pronounced temperature-induced Maxwell-Boltzmann translational velocity distribution and an associated Doppler broadened spectral scattering characteristic that are dissimilar to those of the target particle. The Doppler broadened background Rayleigh light is orders of magnitude spectrally wider than that scattered by a particle in a particle detector view volume. This difference in bandwidth allows the local oscillator light to "tune in" the target particle light in a beat frequency signal and "tune out" the background radiation.

Abstract: A particle counter (10) passes a sample stream of a carrier gas or fluid containing particles (72) through an elongated, flattened nozzle (16) and into a view volume (18) formed by an intersection of the sample stream and a laser beam (13). Particles entrained in the sample stream scatter light rays while passing through the view volume. The scattered light is collected by an optical system (26) and focused on to a detector (40). The magnitude of signal coming from the detector is indicative of the particle size. To correct for variances in particle velocity and light beam intensity across the view volume, flow aperturing is used. Flow aperture modeling (Eqs. 1-7) provides a format for designing the nozzle such that the lateral velocity profile matches the laser beam lateral intensity profile, thereby providing uniform detection sensitivity to laser light scattered from monodisperse particles distributed laterally across the view volume.

Abstract: In a particle detector, a stream carrying particles to be measured is passed through a laser beam. A pair of optical collection systems are arranged perpendicular to the laser beam, opposing each other. The optical collection system reflects light signals indicative of particles sensed in the sensing region to a pair of detector arrays. Each detector array has a plurality of detectors to detect the particle signals, as well as other noise. One detector from each array monitors the same sensing region. The signals from the detectors are processed through a noise cancellation circuit. The noise cancellation circuit first amplifies each detector signal through a photo-amp. Then, the signals of the detectors in one detector array are paired up with corresponding signals of detectors, spaced at least two detectors away, in the other detector array. The paired-up signals pass through differential amplifiers, which essentially cancel the light fluctuation noise.

Abstract: A particle counter (10) passes a sample stream of particles (72) through an elongated, flattened nozzle (16) and into a view volume (18) formed by an intersection of the sample stream and a laser beam (13). Scattered light (24) from the view volume is focused onto a linear array (32) of photodiode detectors (40) positioned such that a longitudinal length (70) of the view volume is imaged on the detectors. Because the sample stream produces nonuniform particle velocities along the longitudinal dimension of the view volume, for same-sized particles higher velocity particles will generate lower output amplitude signals than lower velocity particles. Therefore, the gain associated with each photo-detector element is adjustable to compensate for the nozzle velocity differences, laser beam intensity differences caused by beam divergence and fluctuations, optical path efficiency variations, and photo-detector element-to-element sensitivity differences.

Abstract: A gas-borne optical scattering particle counter uses intracavity optical scattering and heterodyne detection techniques to overcome the lower limit on particle size detection stemming from background light scattering by the gaseous carrier in which a particle is immersed. The particle counter uses a heterodyne technique to exploit a basic physical difference between target particle scattered light and the background light. The carrier gas molecules have a pronounced temperature-induced Maxwell-Boltzmann translational velocity distribution and an associated Doppler broadened spectral scattering characteristic that are dissimilar to those of the target particle. The Doppler broadened background Rayleigh light is orders of magnitude spectrally wider than that scattered by a particle in a particle detector view volume. This difference in bandwidth allows the local oscillator light to "tune in" the target particle light in a beat frequency signal and "tune out" the background radiation.

Abstract: A particle detector employs a resonant cavity having a chromium doped colquiriite crystal lasing medium, such as an Cr:LiSrAlF.sub.6 crystal, adjacent to an intra-cavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the crystal positioned between them, defining a light path through the crystal, but most of the light does not escape past the mirrors. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging thereupon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. Harmonic generators are used in alternate embodiments to produce sub-micron wavelengths. Optical coatings on mirrors forming cascaded cavities are used to isolate a harmonic wavelength in a cavity containing the view volume.

Abstract: A particle detector employs a laser having a solid-state lasing medium, such as an Nd:YAG crystal, disposed in a resonant cavity, and includes an intracavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the laser medium positioned between them, defining a light path. A pump source is optically coupled to drive the laser medium to produce coherent light having a first wavelength. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging there-upon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the intensity of the light sensed.

Abstract: A particle counter including a modulator to allow electronically determining calibration. The modulator is connected to a driving circuit of a source of light to cause the light to emit a beam of a constant amplitude, representing at least one particle of predefined size. Light transmitted along an optical axis changes in intensity in response to a signal produced by the modulator. A detector is positioned to sense the change in intensity to produce signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the change in intensity of the light.

Abstract: A particle detector employs a laser having a solid-state lasing medium, such as an Nd:YAG crystal, disposed in a resonant cavity, and includes an intracavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the laser medium positioned between them, defining a light path. A pump source is optically coupled to drive the laser medium to produce coherent light having a first wavelength. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging thereupon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the intensity of the light sensed.

Abstract: Small, mobile particles in a fluid are optically detected by an apparatus having spaced apart reflectors bordering and defining an optical cavity into which a light beam is introduced. The reflectors are arranged along axes which are slightly misaligned such that the light beam is introduced at a low angle, barely over the edge of one of the reflectors, and is repeatedly reflected between the two reflectors, overlapping itself many times in a view volume located within the optical cavity, thereby increasing the intensity of detected particles. A fluid flow is introduced into the view volume and the light scattered by particles as they pass through the intensely illuminated view volume is received by a detector which observes the view volume. The detector produces a signal which is indicative of characteristics such as the number or size of particles.

Abstract: Apparatus for monitoring fluid contaminant level that includes a light source positioned on one side of a fluid sample path for directing light energy into fluid flowing in the sample path, a photosensor positioned on the same side of the sample path, and a reflector positioned on an opposing side of the sample path for receiving light from the source transmitted through the sample fluid and reflecting such light back through the fluid to the photosensor. The photosensor provides an electrical signal as a function of intensity of light incident thereon from the light source after having twice passed through the fluid, and the concentration or level of contaminants in the fluid is indicated as a function of such electrical signal. Thus, the concentration of contaminants that extinguish light energy transmitted through the fluid is indicated as an inverse function of light intensity at the photosensor, and may be compared to a preset target threshold level for indicating an undesirably high contamination level.