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: A condensation nucleus counter (CNC) device implemented with a multi-directional fluid flow system is configured in a compact, conical geometry. A saturation region includes an inlet that delivers into an annular pool a sample stream of air containing small-diameter particles. The stream of air flows out and expands radially from the inlet and mixes with a working vapor to become saturated in the saturation region. The saturated fluid mixture then flows to a condensation region defined by spaced-apart inner and outer radially converging walls having a conical geometry, thereby forming an annular flow volume of decreasing cross sectional area in the direction of fluid flow to the outlet of the CNC device. The working vapor condenses on the small-diameter particles to enlarge their sizes with less tendency to condense on the inner walls of the condensation region.

Abstract: A preferred OPTICAL BLACK™ ionic anodize process of the present invention applies a porous anodic oxide coating to a component part in a standard sulfuric acid anodizing bath (with or without organic additives). A modified alternating electric current is then applied to the porous oxide coating to remove excess anodizing electrolyte and to allow the coloring solution access to the pores. The oxide coating is electrolytically colored in a low pH acid bath containing a tin salt, sulfuric acid, and organic additives. Alternating current carries additional tin salt to the base of the pores where the tin salt is reduced to metallic tin or tin oxide. Others metals or metallic salts could be employed. Component parts treated by the OPTICAL BLACK™ ionic anodize process can be advantageously employed in optical systems, such as particle detectors, to reduce or eliminate stray light.

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 pump establishes gas flow in a particle counter. A pair of shafts having lobes is mounted in a first housing and serves to establish a gas flow path through a second housing which defines a view volume where particles are counted by light scattering or obscuration of a beam intersecting the light flow path. The lobes of the first housing do not contact each other or the walls of the housing, thereby limiting particles to those suspended in the gas flow.

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: In a reflectance measuring instrument, an integrating sphere is provided to illuminate the sample of which the reflectance is to be measured. A first fiber optic cable is provided to receive a light beam reflected by the sample and a second fiber optic cable is positioned to receive a light beam reflected from the wall of the integrating sphere. The transmitting ends of the fiber optic cables are mounted in a pivoted plate to selectively position the transmitting ends to emit light into the entrance slit of a monochromator.

Abstract: In an instrument adapted particularly for analyzing agricultural products, such as grain, interference filters are rotated successively through an infrared wide wavelength band beam of light, which irradiates a sample of the product. Each of the interference filters operates to transmit a narrow wavelength band of light, the center frequency of which is scanned through a range of values as the angle of incidence of the beam of light to the interference filter varies as the filter rotates through the beam of light. An optical track is provided which rotates with the assembly of interference filters to generate pulses from index markings in the optical track. The markings in the optical track are spaced so that one pulse is generated for each angstrom of variation of the center frequency transmitted through an interference filter.

Abstract: An instrument for optically measuring and analyzing samples of particulate material includes a chute for conveying the samples through a light beam by which the measurements are made and a trough positioned at the bottom of the chute. The trough supports a column of the particulate material in the chute and acts as a gate to prevent the particulate material from flowing out of the chute. The trough is mounted on a vibrator and during the measurement operation vibrates to cause the particulate material to flow out of the chute. When vibrating, the trough transmits vibrations up through the column of particulate material in the chute to maintain the column in a free flowing condition and to prevent bridging.

Abstract: In an instrument for optically measuring the constituents of grain samples, a grinder is provided to grind a sample of grain and direct the ground grain into a chute. A hopper is provided for loading the grain into the grinder with a gate for controlling the flow of the grain into the grinder. A filter wheel and infrared light source assembly directs a beam of infrared light on the grain sample in the chute while continuously changing the wavelength irradiating the grain. As the infrared light is irradiating grain, the grain is moved in a bed through the infrared light and reflectivity measurements are made. From these reflectivity measurements, the oil, water and protein content of the grain sample is determined.