Abstract: Windshear detector using Rayleigh-backscattered light and a molecular filter for optical discrimination, and frequency locking of a laser, to detect windshear. The windshear detector has a pulsed ring laser that transmits a signal out of the detector and receives reflected backscatter of the transmitted signal. The ring laser is driven with an injection laser. Both lasers are ultimately keyed to the molecular transmission or absorption filter with locking electronics. The received reflected backscatter is detected and processed into a signal that indicates whether there is windshear or turbulence.

Abstract: A wet steam monitor determines steam particle size by using laser doppler velocimeter (LDV) device to produce backscatter light. The backscatter light signal is processed with a spectrum analyzer to produce a visibility waveform in the frequency domain. The visibility waveform includes a primary peak and a plurality of sidebands. The bandwidth of at least the primary frequency peak is correlated to particle size by either visually comparing the bandwidth to those of known particle sizes, or by digitizing the waveform and comparing the waveforms electronically.

Abstract: A multiple angle and redundant visibility sensor includes a plurality of optical transmitter/receiver pairs, each pair cooperatively coupled so as to transmit and receive in conically controlled beams along a common optical axis such that each transmitter faces, and directs optical energy directly into, its receiver pair. The plurality of pairs are staggered in angular orientation with respect to each other, with a common volume of intersection through which the approximate center of each optical axis passes. Each transmitter propagates a substantially conical beam of light which passes through an aerosol media which causes molecular scattering of the light. A single transmitter outputs optical energy at any given time, and the receiver intercept the appropriate scattered energy at different scattering angles depending on the relative axial orientation with respect to the scattering volume and the incident radiation.

Abstract: This invention relates to a method for simultaneously determining particle concentration and velocity in multi-phase streams. These determinations may be made by use of a fiber optic probe that establishes an illuminated sensing zone of finite dimensions. The probe collects light backscattered from the zone at discrete points in time. The collected light is converted to a voltage waveform. By taking the mean of the voltage values, concentration can be determined, and, by taking a derivative of the voltage waveform, the velocity can be determined.

Abstract: An apparatus in which scattered light is measured, said apparatus having a light source aligned to direct illumination toward an interface between a sample container and an aqueous solution at an angle less than the critical angle. A detector to measure the scattered light is located at a place outside the envelope of the critical angle.

Abstract: An underwater light scattering sensor includes a light source, light stop and a light detector mounted on a planar support capable of measuring nearly all suspended particle concentrations found in natural waters, 1 .mu.g/l to 3 g/l. The sensor is designed to measure light scattered at nearly all angles, which includes forward scattering, back scattering, and multiple scattering, from suspended particles in water through a very short light path length. The small and simple design of the sensor allows it to be produced at low cost, permitting its use in both expendable and non-expendable applications for the detection or measurement of suspended particulate concentrations in water. The magnitude of the scattered light measured by the sensor is proportional to the suspended particle concentration in water, provided the nature of the particles does not change.

Abstract: An improved method of collecting quasi-elastic light scattering (also known as QELS) data and time-average intensity simultaneously is disclosed, as is a novel apparatus therefor. The apparatus utilizes a novel optical element having a pair of diametrically aligned slits on a masking disc that eliminates the need of index matching fluids that are currently required to eliminate flare from the sample cell walls at the cell-sample and the cell-air interfaces. The novel optical element allows improved angular resolution and on-axis resolution for the fluctuation data obtained.

Abstract: An aerosol spectrometer combines the features of forced motion instruments and optical particle sizers. The motion of suspended particles in multiple force fields is used to obtain density, diameter, electrical charge, magnetic moment and other physical attributes of individual particles. Measurements are possible without the need for precision size standards. Optical scattering parameters are also extracted, namely scattering magnitude and visibility. This allows calibration of the optical sizer based on independently measured size parameters also without the need for precision standards. Since the optical counter is extremely rapid, it is possible to apply feedback control to the application of force on the particles and to the sample dispensing apparatus as well.

Abstract: A particle detector that determines the presence of particles in an enclosed volume includes a laser that directs an optical beam to a beam splitter that produces first and second beams. An optical system directs the first beam into the enclosed volume. A detector is positioned adjacent the volume in order to receive back scattered optical energy arising from a particle in the volume encountering the first beam. The back scattered optical energy and the second beam are optically combined so as to overlap in a region and in the overlap region the back scattered optical energy and second beam are in the same state of focus, of the same polarization and are substantially parallel. A detector located at the overlap region produces an electrical signal indicative of the intensity of the back scattered light. A signal processor analyzes the electrical signal to determine the presence of the particle.

Abstract: Contrail detection aft of an aircraft is provided by a rear-looking ranging system carried by the aircraft. A randomly modulated laser beam is directed into a detection volume aft of the aircraft for scatter back toward a detector on the aircraft. Bistatic mounting of a laser and a telescope of the detector preclude sensing of the scattered beam forward of the detection volume. Processing of the detected scattered beam includes cross correlation and analysis to indicate the formation of the contrail aft of the aircraft.

Abstract: A high resolution lidar is used to backscatter light from atmospheric aerosols. The actual relative humidity is measured at altitudes corresponding to those from which the backscattered light occurs. A mathematical relationship between the two is then derived and this is used to predict atmospheric relative humidity from subsequent lidar backscatter s measurements. The predicted relative humidity is used with temperature and pressures derived from standard lapse rates to calculate the radio refractivity of the atmosphere. Radio ray coverage is then determined based upon the calculated radio refractivity.

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 deriving particle characteristics such as diameter and size distribution from the intensity of the light scattered by the particles. Based on the value of the output of a photomultiplier used to detect the scattered light, it is determined whether a particle is a fine particle, which is a particle with a photoelectron pulse count that does not exceed a prescribed value, or a large particle, and these particles are counted separately. Fine particles are processed using photon counting, and large particles are processed by an analog process, in which case the threshold values used to discriminate particles are varied in accordance with pre-stored data on the refractive index of each fluid.

Abstract: An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped .mu.J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited by optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micro pulse lidar systems are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere.

Abstract: A method for using laser Doppler velocimetry to determine the mass flux (mass per area per time) of a polymer fiber stream without interfering with the flow of the fiber stream wherein a factor is determined for converting laser data rate information into stream flow mass flux values and to determine the diameter of a filament by measuring filament velocity without interfering with the flow of the filament.

Abstract: The lidar arrangement (1) has a transmitter (3) for linearly polarized radiation (12), a receiver (5) with a first receiving device which measures intensity of the backscattered radiation (15) coinciding approximately with the transmitted radiation cone (12) in a polarization plane of the cone and in a perpendicular polarization plane, wherein the receiver further includes a second receiving device which measures the intensity of backscattered radiation (17) outside the transmitted cone (12), the outer backscattered radiation has the shape of a conical shell which surrounds the backscattered conical shell of the first mentioned backscattered radiation (15) and of the transmitted cone (12); the received separate radiation cones (15 and 17) are split in a polarization analyzing optical element into two mutually perpendicular partial light beams, each consisting of an inner partial beam portion (15a, 15b) and an outer partial beam portion (17a and 17b), the inner and outer partial beam portions are separately de

Abstract: A mixture is prepared by mixing carriers to which a substance specifically reacting on an object substance adheres with a sample containing the object substance. The mixture is irradiated by light having an intensity gradient to concentrate the carriers at and near the irradiated positions by the optical pressure of the light. The efficiency of an agglomeration reaction of the carriers is thereby increased. A qualitative or quantitative measurement of the object substance is performed by detecting a state of agglomeration of the carriers within the mixture.

Abstract: The present invention employs an optical filter which rejects substantially all wavelengths except for a selected wavelength. This invention eliminates most optical noise (e.g., solar noise) in LIDAR (light detection and ranging) imaging systems as well as LIDAR bathymetry systems and underwater submarine communication systems. The selected wavelength corresponds to the transmission wavelength of the laser. In accordance with the LIDAR systems of the present invention, a laser beam of the selected wavelength is projected at a body of water wherein a return beam is generated. The reflected or backscattered return beam is collected by optics which then directs the beam at the filter. The beam is filtered so that substantially all other wavelengths not corresponding to the selected wavelength are rejected, thereby eliminating most optical noise, particularly solar noise. The filtered beam is then detected.

Abstract: The present invention uses tunable and fixed frequency lasers as an optical light source in underwater communications systems. This invention provides a high energy, short pulse length laser output which is tunable to or set at a desired wavelength. The tuning is used for performance optimization of the communications systems. An example of performance optimization is the tuning to or setting of the laser at the so-called Jerlov minimum, which is dependent upon the optical characteristics of the particular water used. The system described herein is used as an optical communications downlink employing one or more atomic resonance filter detectors. This invention has the effect of significantly improving the optical signal to noise ratio.

Abstract: A system for determining the physical properties of materials through the use of dynamic light scattering is disclosed. The system includes a probe, a laser source for directing a laser beam into the probe, and a photodetector for converting scattered light detected by the probe into electrical signals. The probe includes at least one optical fiber connected to the laser source and a second optical fiber connected to the photodetector. Each of the fibers may adjoin a gradient index microlens which is capable of providing a collimated laser beam into a scattering medium. The position of the second optical fiber with respect to the optical axis of the probe determines whether homodyne or self-beating detection is provided. Self-beating detection may be provided without a gradient index microlens. This allows a very small probe to be constructed which is insertable through a hypodermic needle or the like into a droplet extending from such a needle.

Abstract: A photoluminescence sensor for detecting a photoluminescent light from a toluminescent material is disclosed. In a preferred embodiment the photoluminescence sensor comprises: a source of light; a concave mirror having at least one perforation for passing the source light through the at least one perforation; an optical waveguide having proximal and distal ends with the photoluminescent material being disposed at the distal end; an objective for directing the source light into the proximal end of the waveguide; an objective for receiving photoluminescent light and for focusing the photoluminescent light onto the perforated concave mirror; a liquid filter for passing the photoluminescent light reflected from the perforated concave mirror to a detector to detect the photoluminescent light.

Abstract: A non-invasive medical imaging technique capable of evaluating, in situ, the oxygenation state of body tissues (e.g., by measuring the spectral properties of heme proteins) is described. The technique is based on the measurement of scattered radiation in the near-infrared region (NIR), where significant penetration into body tissues occurs. The disclosed technique employs a multi-wavelength collimated source and a collimated receiver and performs a positional and angular scan of the scattered radiation for each position of the incident beam. The resultant data is evaluated by employing imaging schemes which give differential weights to the contribution of various volume elements (voxels) in the medium to the detector response. A three-dimensional spectroscopic image of the target medium is determined by considering the contribution of the various volume elements for each source-detector configuration and position of the incident beam at various frequencies.

Abstract: This flow cytometer includes flow cell containing a flowing stream of a number of particles which flow one at a time in a straight line based on hydrodynamic methods, a radiator for radiating a light on the particles flowing through the flow cell, a forward scattered light detector for detecting a light scattered in the same direction as the radiating light, a right angle signal light detector for detecting light radiated in a right angle with respect to the direction of the radiating light, whereby the right angle signal light detecting assembly is disposed on a mount, with one end of the mount being elastically supported on a supporting member and the other end being disposed on another supporting member by an adjustment mechanism, whereby adjusting the inclination of the light axis of the right angle signal light detecting assembly is made easier so that the light axis can always be perpendicular to the radiated light.

Abstract: This invention concerns an apparatus for the measurement of the parameters of atmospheric visibility or optical density. The apparatus includes a transmitter with which light operating as the measurement signal can be emitted to the measured space; a receiver with which light backscattered from the measured space can be received; and an information processor with which the information of light received by the receiver can be processed and interpreted. According to the invention the active surfaces of the transmitter and receiver means are aligned along an at least essentially same optical axis.

Abstract: A method of measuring the size distribution of moving particles within a scattering medium includes a step of directing a beam of light into the scattering medium. The frequency of the scattered light is compared to nonscattered light emitted from the scattering medium and results in the generation of a first signal having a magnitude which is indicative of the difference in frequency between the scattered light and the nonscattered light. A second signal is generated having a magnitude which varies with frequency on a linear scale. The frequency scale of the second signal is then translated to a logarithmic scale. Finally, the translated second signal is deconvolved to determine the size and distribution of moving particles within the scattering medium.

Abstract: A device for measuring the speed of the wind at medium altitude by the Doppler effect within the visible frequency range comprises a laser which emits pulses of light, a telescope which receives a scattered light and an interferometer used to measure the spectral shift of the scattered light in relation to the emitted pulse of light. The interferometer is a Fabry-Perot interferometer in which a part of one of the two mirrors of the interferometer is covered with an excess thickness of silica to form two separate filters. The spacing of the two mirrors and the excess thickness of silica are determined in such a manner that the pass bands of each one of the two filters thus constructed are centered on the flanks of the spectral distribution of the backscattered light.

Abstract: A method and apparatus for the noninvasive real-time characterization of samples using coherent backscattering is disclosed. The sample is illuminated by a laser, and the radiation that is coherently backscattered is measured. The line width or line shape of the coherent backscattered radiation, or in some cases just the existence of coherent backscatter, is then used to characterize the sample under test. This characterization is then used for the real time control of a process acting upon the sample.

Abstract: A device uses fringe laser diode anemometers which, from the beams coming from one or more laser diodes, form measuring volumes having interference fringes. The component of the relative speed of an aircraft in a direction perpendicular to the plane of these fringes is deduced from the modulation of light reflected by particles moving through the measuring volume to cause modulation of the signal of the photodetector of each anemometer during their passage in the measuring volume of this anemometer. By joining two anemometers with the measuring volumes whose planes of the associated fringes are, for example, orthogonal, it is possible to determine two components of the relative speed vector and determine, for example, this relative speed in the longitudinal vertical plane of the aircraft, and to deduce from it the angle of incidence of the aircraft.

Abstract: A system and method for sensing a target substance in a medium by directing at least first and second beams of radiation to intersect within the medium and establish one or more sensing volumes. The beams have different frequencies to generate a beat frequency at the sensing volume. A selected optical effect, based on an optical property of the target substance within the sensing volume, on the first and second beams is detected at at least one selected spectral line. A signal is generated representative of the selected optical effect, such as absorbance or fluorescence, and the portion of the signal which is substantially at the beat frequency is combined with at least one selected value to determine the amount of the target substance.

Abstract: An apparatus for determining the amount of particle suspension in a fluid by measuring radiation reflection on the particles, comprises a beam of radiation directed into the fluid; first and second photovoltaic detectors for picking up at least a portion of the beam of radiation reflected from the particle suspension in the fluid; and a circuit for comparing the output of the first detector relative to the output of the second detector to obtain the amount of particle suspension in the fluid. The detectors are positioned such that the output of the first detector increases relative to the output of the second detector as the amount of particle suspension in the fluid increases.

Abstract: A laser light scattering and spectroscopic detector is provided which includes a probe comprising an optical fiber coupled to a graded index microlens. The angular aperture and the divergence of the probe are designed specifically to satisfy the scattering volume and coherence requirements for laser light scattering and spectroscopic measurements. The detector includes a housing which defines an elongate cell therein and a selected number of detector ports extending at various angles with respect to the cell. A method is provided for detecting scattered light which includes the steps of positioning the probe inside or outside the scattering medium at a selected angle with respect to the laser beam.

Abstract: A velocity distribution measurement apparatus directs light at an object, detects scattered light from the object, photoelectrically converts the light and subjects it to signal processing to obtain velocity distribution characteristics of the object, by detecting a speckle pattern formed by interference between rays of light scattering from points on the object. The apparatus consists mainly of a laser beam source; an optical deflector for scanning the laser at a certain frequency; an optical system for projecting the light scanned by the deflector onto the object; a detector for detecting the speckle pattern; and signal processing means for analyzing detector outputs to establish the speckle pattern variations for each scanning frequency at which the optical deflector performs scanning, in order to obtain information on velocity distribution in the object. The optical system is easy to adjust, and measurement and processing can be accomplished in a relatively short time.

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: A method and an apparatus are disclosed in which paying attention to the fact that the rate of attenuation of laser lilght propagating in the atmosphere changes depending on meteorological conditions, the rate of attenuation is detected and the optimum laser beam emission or divergence angle is controlled in accordance with the detected rate of attenuation. There are also disclosed a method and an apparatus in which the optimum beam angle is controlled in accordance with a distance to a target existing in the atmosphere or the shape of the target. Further, there are disclosed a method and an apparatus in which the optimum beam angle is controlled taking either two or all of the rate of attenuation, the distance to the target and the shape of the target into consideration.

Abstract: A method and apparatus for separating particles by means of a contra-flow centrifuge, wherein a monitor system is used to analyze or control the separation process. The monitor system used impinges a monochromatic light beam on a sample of the separated particles, and measures the light scattering not only in the beam-forward direction, but also in the beam-reverse and beam-lateral directions. This reduces the processing time and increases the reliabiity of output data.

Abstract: The device for visibility measurement is designed primarily for use in motor vehicles. A light emitter is arranged inside the driver's compartment preferably on the rear view mirror in front of the windshield. The light emitter generates light pulses or flashes radiating through the windshield. The light scattered back due to soiling on the inside and outside of the windshield or in scatter zones, formed by fog or smoke or the like, in front of the windshield, impinges a light sensor, preferably likewise arranged on the rear view mirror inside the driver's compartment. By utilizing light pulses of various wavelengths and processing of the output signals of the light sensor in predetermined or predeterminable time windows or intervals, not only the respective visibility but also the type of viewing impairment can be determined.

Abstract: An optical radar system for coherent ranging and velocimetry. Modulation of a laser diode by light backscattered from a target is used to determine distance and velocity of a target. An array of laser diodes are used to determine the velocity and topography of a target. Three laser diodes are used to determine speed and orientation of a rotating disk.

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: Apparatus for analyzing particles contained in a fluent edium (12). The apparatus includes a body (20) having a window (30), an optical source preferably comprising a laser diode (100) having a small light emitting area (140), and an optical system (102) for focusing the light from the laser diode at a focal spot (84) such that the size of the focal spot is approximately equal to the size of the light emitting area of the laser diode. A photodetector (106) is mounted in the body and detects light backscattered from the focal spot by particles in the fluent medium, and produces an electrical signal that comprises a series of pulses associated with the particles. The electrical signal is input to a detector that counts the pulses and indicates the number of particles in the fluent medium. The detector includes discrimination means for preventing the counting of a pulse that has a rise or fall time above a predetermined threshold, thereby discriminating against particles that are not at the focal spot.

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: A photometric method and apparatus for measuring agglutination in a biological agglutination reaction system test sample using a laser beam source and at least one photodetector for detecting light scattered by the test sample. The method includes the following steps: (1) arranging the at least one photodetector so as to be capable of detecting scattered light from the test sample at a scatter angle of 30 to 60 with respect to a laser beam directed at the test sample from the laser beam source; (2) irradiating the test sample with the laser beam from the laser beam source; (3) selectively detecting the intensity of scattered light from the test sample at the scatter angle of 30 to 60 using the at least one photodetector which provides an output indicative thereof; and (4) determining the first derivative of the output of the at least one photodetector with respect to time and obtaining the maximum value thereof.

Abstract: The method of measuring the optical scattering co-efficient of the ocean by means of a laser beam (15) from a platform (16) above the ocean surface (3) in which an ocean penetrating beam (15) is swept across the direct path of travel to the surface of the ocean (3) and through it to the ocean bottom (4) to be back-reflected to the ocean surface (3) and to a receiver on the platform (16) characterized by changing the field of view to alternately use a small and a large field of view and calculating from the larger field of view an estimate of the absorption co-efficient and from the smaller field of view an estimate of beam attenuation co-efficient.

Abstract: A method and device is provided for determining the direction and speed of wind in the atmosphere by means of a laser-Doppler anemometer, wherein only values measured in a sector of about 100.degree. and less of an azimuth scan are supplied or fed to a multiple-peak finder of a measuring device. In order to attain a high processing speed, flowing differentiation takes place by means of digitally operating systems. In order to eliminate the influences from clouds, haze, fog and the like in the measuring device, several frequency maximums are always traced in the multiple-peak finder, whereby in each case a preceding maximum is related to a trailing maximum until the trailing maximum is smaller than the preceding maximum. Because of the attainable high-speed sector scanning, the measuring device can be used for the determination of multiple wind peaks caused by clouds and/or fog echoes, or at an installation site where the measuring range is highly restricted, or also for detecting aircraft wake vortices.

Abstract: Liquid mobility is judged by the steps of filling the specimen in a specimen chamber formed in a specimen bed made of a transparent material just up to the level of the upper surface of the specimen bed, of pressing a liquid-absorbent material keeper for keeping a liquid-absorbent material horizontally to make the liquid-absorbent material contact with the specimen bed from the upper side of the specimen chamber, and of continuously detecting an intensity of a scattered light coming from the specimen in the specimen chamber with an optical detector consisting of a light emitting source and a light receiver and being disposed on the side of the lower surface of the specimen bed while the liquid-absorbent material is forced to contact the specimen bed. The liquid mobility is grasped in a short period of time.

Abstract: A ceilometer operating according to a gating method integrates output signals from a light receiver. The output signals are passed by analog gating means during consecutive time slots following each other at the transmitter frequency and being phase shifted relative to transmitted light pulses. The phase shift of the time slots is varied stepwise after preset time intervals. Signals integrated during a time interval are digitalized, processed n a microprocessor and stored in a memory according to height values determined by respective phase shifts of the time slots. The micro-processors forms a smooth function of the signals accordint to height values, differentiates the smooth function, computes maxima and minima, determines maxima differing from a preset threshold value, and selects a maximum which with increasing height value is followed by a minimum.

Abstract: A fiber optic probe having a sealed, cylindrical housing closed at one end by a transparent window and at the opposite end by a wall through which a plurality of optical fibers extend toward the window. Adjacent the window the fibers are radially and circumferentially spaced about the axis of the housing and converge along lines which intersect one another at a common point on the housing axis that is adjacent or beyond the outer surface of the window. At least one of the fibers transmits light from a source through the window to illuminate a zone of a fluid sample, whereby particles present in such zone scatter light therefrom to the remaining fibers for transmission through the probe housing to light detecting and measuring apparatus.

Abstract: Improved detector and processing circuitry for use with a vorticity measurement optical probe system is disclosed. The invention makes use of a dual axis position indicating photodetector so that two components of vorticity may be simultaneously measured. Reflective spherical particles are disposed in a fluid whose vorticity is to be measured, and a light beam is reflected off of the particles and onto the photodetector. Analog and digital processing circuitry is connected to the outputs of the photodetector, and generate data that is indicative of the position of the reflected light beam on the photodetector as a function of time. Computer interface circuitry is also provided which enables the beam position data to be read into a digital computer so that the two vorticity components may be calculated therefrom. Embodiments which utilize plural axis photodetectors are also disclosed.

Abstract: Air turbulence ahead of an aircraft is determined by scanning the beam of a variable focal distance laser airspeed unit close-in to the aircraft to determine aircraft airspeed and angle of attack, and scanning the beam at distances farther out from the aircraft and measuring airspeed. Discrepancies between the close-in measurement and the farther out measurement are quantifiably indicative of air turbulence.

Abstract: The concentration of larger particles in a suspension of relatively small and relatively large light scattering particles is determined by illuminating a zone of the suspension with light of such wavelength as to be scattered more efficiently by the larger particles than by the smaller particles. The scattered light is collected and its intensity measured. The value of the collected light intensity then is compared with the corresponding value of the same wavelength light scattered by corresponding suspensions containing known concentrations of particles.

Abstract: The present invention relates to a method and apparatus for measuring the content of suspended substances in a flowing medium by illuminating the medium with light from a light source. Reflected light from the medium is detected by at least two detectors, at least one of which measures directly reflected light while the other detectors measure multiply reflected light. The detector for detecting directly reflected light is located such that a linear relationship is established between its output signal and the concentration of the flowing medium. The other detectors are located such that their output signals will be essentially constant in relation to the concentration of particles in the flowing medium within a large range. The measuring scheme provides for obtaining the quotient of the signal provided by direct reflection divided by the signal provided by multiple reflection.

Abstract: A sample cell is described that permits the measurement of the light scattering properties of very small liquid-borne samples with negligible background interference form the illumination source. A technique is described whereby the cell construction permits the measurement of the illumination intensity at the scattering sample itself, permitting, thereby, the normalization of each detected scattered signal. The cell structure and detection method incorporated therein also permit measurement of extremely small angle scattered intensities without interference of the incident light beam itself.